## Guide to the Secure Configuration of Ubuntu 20.04

> with profile CIS Ubuntu 20.04 Level 1 Server Benchmark
> This baseline aligns to the Center for Internet Security Ubuntu 20.04 LTS Benchmark, v1.0.0, released 07-21-2020.

The SCAP Security Guide Project
https://www.open-scap.org/security-policies/scap-security-guide
This guide presents a catalog of security-relevant configuration settings for Ubuntu 20.04. It is a rendering of content structured in the eXtensible Configuration Checklist Description Format (XCCDF) in order to support security automation. The SCAP content is is available in the `scap-security-guide` package which is developed at https://www.open-scap.org/security-policies/scap-security-guide.
Providing system administrators with such guidance informs them how to securely configure systems under their control in a variety of network roles. Policy makers and baseline creators can use this catalog of settings, with its associated references to higher-level security control catalogs, in order to assist them in security baseline creation. This guide is a catalog, not a checklist, and satisfaction of every item is not likely to be possible or sensible in many operational scenarios. However, the XCCDF format enables granular selection and adjustment of settings, and their association with OVAL and OCIL content provides an automated checking capability. Transformations of this document, and its associated automated checking content, are capable of providing baselines that meet a diverse set of policy objectives. Some example XCCDF Profiles, which are selections of items that form checklists and can be used as baselines, are available with this guide. They can be processed, in an automated fashion, with tools that support the Security Content Automation Protocol (SCAP). The DISA STIG, which provides required settings for US Department of Defense systems, is one example of a baseline created from this guidance.
Do not attempt to implement any of the settings in this guide without first testing them in a non-operational environment. The creators of this guidance assume no responsibility whatsoever for its use by other parties, and makes no guarantees, expressed or implied, about its quality, reliability, or any other characteristic.

## Profile Information

Profile Title | CIS Ubuntu 20.04 Level 1 Server Benchmark
Profile ID | xccdf_org.ssgproject.content_profile_cis_level1_server

#### CPE Platforms

- cpe:/o:canonical:ubuntu_linux:20.04::~~lts~~~

## Revision History

Current version: 0.1.76

- draft (as of 2025-03-01)

## Table of Contents

1. System Settings
   1. Installing and Maintaining Software
   2. Account and Access Control
   3. AppArmor
   4. GRUB2 bootloader configuration
   5. Configure Syslog
   6. Network Configuration and Firewalls
   7. File Permissions and Masks
2. Services
   1. Avahi Server
   2. Cron and At Daemons
   3. Deprecated services
   4. DHCP
   5. DNS Server
   6. FTP Server
   7. Web Server
   8. IMAP and POP3 Server
   9. LDAP
   10. Mail Server Software
   11. NFS and RPC
   12. Network Time Protocol
   13. Obsolete Services
   14. Print Support
   15. Proxy Server
   16. Samba(SMB) Microsoft Windows File Sharing Server
   17. SNMP Server
   18. SSH Server
   19. X Window System

## Checklist

Group Guide to the Secure Configuration of Ubuntu 20.04 Group contains 93 groups and 260 rules
Group System Settings Group contains 49 groups and 176 rules
[ref] Contains rules that check correct system settings.
Group Installing and Maintaining Software Group contains 6 groups and 9 rules
[ref] The following sections contain information on security-relevant choices during the initial operating system installation process and the setup of software updates.
Group System and Software Integrity Group contains 2 groups and 4 rules

[ref] System and software integrity can be gained by installing antivirus, increasing system encryption strength with FIPS, verifying installed software, enabling SELinux, installing an Intrusion Prevention System, etc. However, installing or enabling integrity checking tools cannot prevent intrusions, but they can detect that an intrusion may have occurred. Requirements for integrity checking may be highly dependent on the environment in which the system will be used. Snapshot-based approaches such as AIDE may induce considerable overhead in the presence of frequent software updates.

Group Software Integrity Checking Group contains 1 group and 3 rules

[ref] Both the AIDE (Advanced Intrusion Detection Environment) software and the RPM package management system provide mechanisms for verifying the integrity of installed software. AIDE uses snapshots of file metadata (such as hashes) and compares these to current system files in order to detect changes.
The RPM package management system can conduct integrity checks by comparing information in its metadata database with files installed on the system.

Group Verify Integrity with AIDE Group contains 3 rules
[ref] AIDE conducts integrity checks by comparing information about files with previously-gathered information. Ideally, the AIDE database is created immediately after initial system configuration, and then again after any software update. AIDE is highly configurable, with further configuration information located in `/usr/share/doc/aide-VERSION` .

#### Rule Install AIDE [ref]

The `aide` package can be installed with the following command:

    $ apt-get install aide

Rationale: | The AIDE package must be installed if it is to be available for integrity checking.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_package_aide_installed

References:

cis-csc | 1, 11, 12, 13, 14, 15, 16, 2, 3, 5, 7, 8, 9
cjis | 5.10.1.3
cobit5 | APO01.06, BAI01.06, BAI02.01, BAI03.05, BAI06.01, BAI10.01, BAI10.02, BAI10.03, BAI10.05, DSS01.03, DSS03.05, DSS04.07, DSS05.02, DSS05.03, DSS05.05, DSS05.07, DSS06.02, DSS06.06
disa | CCI-002696, CCI-001744
isa-62443-2009 | 4.3.4.3.2, 4.3.4.3.3, 4.3.4.4.4
isa-62443-2013 | SR 3.1, SR 3.3, SR 3.4, SR 3.8, SR 4.1, SR 6.2, SR 7.6
ism | 1034, 1288, 1341, 1417
iso27001-2013 | A.11.2.4, A.12.1.2, A.12.2.1, A.12.4.1, A.12.5.1, A.12.6.2, A.14.1.2, A.14.1.3, A.14.2.2, A.14.2.3, A.14.2.4, A.14.2.7, A.15.2.1, A.8.2.3
nist | CM-6(a)
nist-csf | DE.CM-1, DE.CM-7, PR.DS-1, PR.DS-6, PR.DS-8, PR.IP-1, PR.IP-3
pcidss | Req-11.5
os-srg | SRG-OS-000445-GPOS-00199
stigid | UBTU-20-010450
cis | 1.4.1
anssi | R76, R79
pcidss4 | 11.5.2
stigref | SV-238371r880913_rule

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | enable

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    DEBIAN_FRONTEND=noninteractive apt-get install -y "aide"

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation OSBuild Blueprint snippet ⇲

    [[packages]]
    name = "aide"
    version = "*"

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | enable

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - CJIS-5.10.1.3
      - DISA-STIG-UBTU-20-010450
      - NIST-800-53-CM-6(a)
      - PCI-DSS-Req-11.5
      - PCI-DSSv4-11.5.2
      - enable_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - package_aide_installed

    - name: Ensure aide is installed
      package:
        name: aide
        state: present
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - CJIS-5.10.1.3
      - DISA-STIG-UBTU-20-010450
      - NIST-800-53-CM-6(a)
      - PCI-DSS-Req-11.5
      - PCI-DSSv4-11.5.2
      - enable_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - package_aide_installed

Remediation Puppet snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | enable

    include install_aide

    class install_aide {
      package { 'aide':
        ensure => 'installed',
      }
    }

#### Rule Build and Test AIDE Database [ref]

Run the following command to generate a new database:

    $ sudo aideinit

By default, the database will be written to the file `/var/lib/aide/aide.db.new`. Storing the database, the configuration file `/etc/aide.conf`, and the binary `/usr/bin/aide.wrapper` (or hashes of these files), in a secure location (such as on read-only media) provides additional assurance about their integrity. The newly-generated database can be installed as follows:

    $ sudo cp /var/lib/aide/aide.db.new /var/lib/aide/aide.db

To initiate a manual check, run the following command:

    $ sudo /usr/bin/aide.wrapper --check

If this check produces any unexpected output, investigate.

Rationale: | For AIDE to be effective, an initial database of "known-good" information about files must be captured and it should be able to be verified against the installed files.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_aide_build_database

References:

cis-csc | 1, 11, 12, 13, 14, 15, 16, 2, 3, 5, 7, 8, 9
cjis | 5.10.1.3
cobit5 | APO01.06, BAI01.06, BAI02.01, BAI03.05, BAI06.01, BAI10.01, BAI10.02, BAI10.03, BAI10.05, DSS01.03, DSS03.05, DSS04.07, DSS05.02, DSS05.03, DSS05.05, DSS05.07, DSS06.02, DSS06.06
disa | CCI-002696, CCI-001744
isa-62443-2009 | 4.3.4.3.2, 4.3.4.3.3, 4.3.4.4.4
isa-62443-2013 | SR 3.1, SR 3.3, SR 3.4, SR 3.8, SR 4.1, SR 6.2, SR 7.6
iso27001-2013 | A.11.2.4, A.12.1.2, A.12.2.1, A.12.4.1, A.12.5.1, A.12.6.2, A.14.1.2, A.14.1.3, A.14.2.2, A.14.2.3, A.14.2.4, A.14.2.7, A.15.2.1, A.8.2.3
nist | CM-6(a)
nist-csf | DE.CM-1, DE.CM-7, PR.DS-1, PR.DS-6, PR.DS-8, PR.IP-1, PR.IP-3
pcidss | Req-11.5
os-srg | SRG-OS-000445-GPOS-00199
stigid | UBTU-20-010450
cis | 1.4.1
anssi | R76, R79
pcidss4 | 11.5.2
stigref | SV-238371r880913_rule

Remediation Shell script ⇲

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    DEBIAN_FRONTEND=noninteractive apt-get install -y "aide"

    AIDE_CONFIG=/etc/aide/aide.conf
    DEFAULT_DB_PATH=/var/lib/aide/aide.db

    # Fix db path in the config file, if necessary
    if ! grep -q '^database=file:' ${AIDE_CONFIG}; then
        # replace_or_append gets confused by 'database=file' as a key, so should not be used.
        #replace_or_append "${AIDE_CONFIG}" '^database=file' "${DEFAULT_DB_PATH}" '@CCENUM@' '%s:%s'
        echo "database=file:${DEFAULT_DB_PATH}" >> ${AIDE_CONFIG}
    fi

    # Fix db out path in the config file, if necessary
    if ! grep -q '^database_out=file:' ${AIDE_CONFIG}; then
        echo "database_out=file:${DEFAULT_DB_PATH}.new" >> ${AIDE_CONFIG}
    fi

    /usr/sbin/aideinit -y -f

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | restrict

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - CJIS-5.10.1.3
      - DISA-STIG-UBTU-20-010450
      - NIST-800-53-CM-6(a)
      - PCI-DSS-Req-11.5
      - PCI-DSSv4-11.5.2
      - aide_build_database
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy

    - name: Build and Test AIDE Database - Ensure AIDE Is Installed
      ansible.builtin.apt:
        name: aide
        state: present
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - CJIS-5.10.1.3
      - DISA-STIG-UBTU-20-010450
      - NIST-800-53-CM-6(a)
      - PCI-DSS-Req-11.5
      - PCI-DSSv4-11.5.2
      - aide_build_database
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy

    - name: Build and Test AIDE Database - Check if DB Path in /etc/aide/aide.conf Is
        Already Set
      ansible.builtin.lineinfile:
        path: /etc/aide/aide.conf
        regexp: ^#?(\s*)(database=)(.*)$
        state: absent
      check_mode: true
      changed_when: false
      register: database_replace
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - CJIS-5.10.1.3
      - DISA-STIG-UBTU-20-010450
      - NIST-800-53-CM-6(a)
      - PCI-DSS-Req-11.5
      - PCI-DSSv4-11.5.2
      - aide_build_database
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy

    - name: Build and Test AIDE Database - Check if DB Out Path in /etc/aide/aide.conf
        Is Already Set
      ansible.builtin.lineinfile:
        path: /etc/aide/aide.conf
        regexp: ^#?(\s*)(database_out=)(.*)$
        state: absent
      check_mode: true
      changed_when: false
      register: database_out_replace
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - CJIS-5.10.1.3
      - DISA-STIG-UBTU-20-010450
      - NIST-800-53-CM-6(a)
      - PCI-DSS-Req-11.5
      - PCI-DSSv4-11.5.2
      - aide_build_database
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy

    - name: Build and Test AIDE Database - Fix DB Path in Config File if Necessary
      ansible.builtin.lineinfile:
        path: /etc/aide/aide.conf
        regexp: ^#?(\s*)(database)(\s*)=(\s*)(.*)$
        line: \2\3=\4file:/var/lib/aide/aide.db
        backrefs: true
      when:
      - '"linux-base" in ansible_facts.packages'
      - database_replace.found > 0
      tags:
      - CJIS-5.10.1.3
      - DISA-STIG-UBTU-20-010450
      - NIST-800-53-CM-6(a)
      - PCI-DSS-Req-11.5
      - PCI-DSSv4-11.5.2
      - aide_build_database
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy

    - name: Build and Test AIDE Database - Fix DB Out Path in Config File if Necessary
      ansible.builtin.lineinfile:
        path: /etc/aide/aide.conf
        regexp: ^#?(\s*)(database_out)(\s*)=(\s*)(.*)$
        line: \2\3=\4file:/var/lib/aide/aide.db.new
        backrefs: true
      when:
      - '"linux-base" in ansible_facts.packages'
      - database_out_replace.found > 0
      tags:
      - CJIS-5.10.1.3
      - DISA-STIG-UBTU-20-010450
      - NIST-800-53-CM-6(a)
      - PCI-DSS-Req-11.5
      - PCI-DSSv4-11.5.2
      - aide_build_database
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy

    - name: Build and Test AIDE Database - Ensure the Default DB Path is Added
      ansible.builtin.lineinfile:
        path: /etc/aide/aide.conf
        line: database=file:/var/lib/aide/aide.db
        create: true
      when:
      - '"linux-base" in ansible_facts.packages'
      - database_replace.found == 0
      tags:
      - CJIS-5.10.1.3
      - DISA-STIG-UBTU-20-010450
      - NIST-800-53-CM-6(a)
      - PCI-DSS-Req-11.5
      - PCI-DSSv4-11.5.2
      - aide_build_database
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy

    - name: Build and Test AIDE Database - Ensure the Default Out Path is Added
      ansible.builtin.lineinfile:
        path: /etc/aide/aide.conf
        line: database_out=file:/var/lib/aide/aide.db.new
        create: true
      when:
      - '"linux-base" in ansible_facts.packages'
      - database_out_replace.found == 0
      tags:
      - CJIS-5.10.1.3
      - DISA-STIG-UBTU-20-010450
      - NIST-800-53-CM-6(a)
      - PCI-DSS-Req-11.5
      - PCI-DSSv4-11.5.2
      - aide_build_database
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy

    - name: Build and Test AIDE Database - Build and Test AIDE Database
      ansible.builtin.command: /usr/sbin/aideinit -y -f
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - CJIS-5.10.1.3
      - DISA-STIG-UBTU-20-010450
      - NIST-800-53-CM-6(a)
      - PCI-DSS-Req-11.5
      - PCI-DSSv4-11.5.2
      - aide_build_database
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy

#### Rule Configure Periodic Execution of AIDE [ref]

At a minimum, AIDE should be configured to run a weekly scan. To implement a daily execution of AIDE at 4:05am using cron, add the following line to `/etc/crontab`:

    05 4 * * * root /usr/bin/aide.wrapper --config /etc/aide/aide.conf --check

To implement a weekly execution of AIDE at 4:05am using cron, add the following line to `/etc/crontab`:

    05 4 * * 0 root /usr/bin/aide.wrapper --config /etc/aide/aide.conf --check

AIDE can be executed periodically through other means; this is merely one example. The usage of cron's special time codes, such as `@daily` and `@weekly` is acceptable.

Rationale:

By default, AIDE does not install itself for periodic execution. Periodically running AIDE is necessary to reveal unexpected changes in installed files.
Unauthorized changes to the baseline configuration could make the system vulnerable to various attacks or allow unauthorized access to the operating system. Changes to operating system configurations can have unintended side effects, some of which may be relevant to security.
Detecting such changes and providing an automated response can help avoid unintended, negative consequences that could ultimately affect the security state of the operating system. The operating system's Information Management Officer (IMO)/Information System Security Officer (ISSO) and System Administrators (SAs) must be notified via email and/or monitoring system trap when there is an unauthorized modification of a configuration item.

Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_aide_periodic_cron_checking

References:

cis-csc | 1, 11, 12, 13, 14, 15, 16, 2, 3, 5, 7, 8, 9
cjis | 5.10.1.3
cobit5 | APO01.06, BAI01.06, BAI02.01, BAI03.05, BAI06.01, BAI10.01, BAI10.02, BAI10.03, BAI10.05, DSS01.03, DSS03.05, DSS04.07, DSS05.02, DSS05.03, DSS05.05, DSS05.07, DSS06.02, DSS06.06
disa | CCI-002702, CCI-001744, CCI-002699
isa-62443-2009 | 4.3.4.3.2, 4.3.4.3.3, 4.3.4.4.4
isa-62443-2013 | SR 3.1, SR 3.3, SR 3.4, SR 3.8, SR 4.1, SR 6.2, SR 7.6
iso27001-2013 | A.11.2.4, A.12.1.2, A.12.2.1, A.12.4.1, A.12.5.1, A.12.6.2, A.14.1.2, A.14.1.3, A.14.2.2, A.14.2.3, A.14.2.4, A.14.2.7, A.15.2.1, A.8.2.3
nist | SI-7, SI-7(1), CM-6(a)
nist-csf | DE.CM-1, DE.CM-7, PR.DS-1, PR.DS-6, PR.DS-8, PR.IP-1, PR.IP-3
pcidss | Req-11.5
os-srg | SRG-OS-000363-GPOS-00150, SRG-OS-000446-GPOS-00200, SRG-OS-000447-GPOS-00201
stigid | UBTU-20-010074
cis | 1.4.2
anssi | R76
pcidss4 | 11.5.2
stigref | SV-238236r853415_rule

Remediation Shell script ⇲

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    DEBIAN_FRONTEND=noninteractive apt-get install -y "aide"

    # AiDE usually adds its own cron jobs to /etc/cron.daily. If script is there, this rule is
    # compliant. Otherwise, we copy the script to the /etc/cron.weekly
    if ! grep -Eq '^(\/usr\/bin\/)?aide(\.wrapper)?\s+' /etc/cron.*/*; then
        cp -f /usr/share/aide/config/cron.daily/aide /etc/cron.weekly/
    fi

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | restrict

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - CJIS-5.10.1.3
      - DISA-STIG-UBTU-20-010074
      - NIST-800-53-CM-6(a)
      - NIST-800-53-SI-7
      - NIST-800-53-SI-7(1)
      - PCI-DSS-Req-11.5
      - PCI-DSSv4-11.5.2
      - aide_periodic_cron_checking
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy

    - name: Ensure AIDE is installed
      package:
        name: '{{ item }}'
        state: present
      with_items:
      - aide
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - CJIS-5.10.1.3
      - DISA-STIG-UBTU-20-010074
      - NIST-800-53-CM-6(a)
      - NIST-800-53-SI-7
      - NIST-800-53-SI-7(1)
      - PCI-DSS-Req-11.5
      - PCI-DSSv4-11.5.2
      - aide_periodic_cron_checking
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy

    - name: Set cron package name - RedHat
      set_fact:
        cron_pkg_name: cronie
      when:
      - '"linux-base" in ansible_facts.packages'
      - ansible_os_family == "RedHat" or ansible_os_family == "Suse"
      tags:
      - CJIS-5.10.1.3
      - DISA-STIG-UBTU-20-010074
      - NIST-800-53-CM-6(a)
      - NIST-800-53-SI-7
      - NIST-800-53-SI-7(1)
      - PCI-DSS-Req-11.5
      - PCI-DSSv4-11.5.2
      - aide_periodic_cron_checking
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy

    - name: Set cron package name - Debian
      set_fact:
        cron_pkg_name: cron
      when:
      - '"linux-base" in ansible_facts.packages'
      - ansible_os_family == "Debian"
      tags:
      - CJIS-5.10.1.3
      - DISA-STIG-UBTU-20-010074
      - NIST-800-53-CM-6(a)
      - NIST-800-53-SI-7
      - NIST-800-53-SI-7(1)
      - PCI-DSS-Req-11.5
      - PCI-DSSv4-11.5.2
      - aide_periodic_cron_checking
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy

    - name: Install cron
      package:
        name: '{{ cron_pkg_name }}'
        state: present
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - CJIS-5.10.1.3
      - DISA-STIG-UBTU-20-010074
      - NIST-800-53-CM-6(a)
      - NIST-800-53-SI-7
      - NIST-800-53-SI-7(1)
      - PCI-DSS-Req-11.5
      - PCI-DSSv4-11.5.2
      - aide_periodic_cron_checking
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy

    - name: Configure Periodic Execution of AIDE
      cron:
        name: run AIDE check
        minute: 5
        hour: 4
        weekday: 0
        user: root
        job: /usr/bin/aide.wrapper --check
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - CJIS-5.10.1.3
      - DISA-STIG-UBTU-20-010074
      - NIST-800-53-CM-6(a)
      - NIST-800-53-SI-7
      - NIST-800-53-SI-7(1)
      - PCI-DSS-Req-11.5
      - PCI-DSSv4-11.5.2
      - aide_periodic_cron_checking
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy

#### Rule Package "prelink" Must not be Installed [ref]

The `prelink` package can be removed with the following command:

     $ apt-get remove prelink

Rationale: | The use of the `prelink` package can interfere with the operation of AIDE since it binaries. Prelinking can also increase damage caused by vulnerability in a common library like libc.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_package_prelink_removed

References:

cis | 1.6.3

Remediation Shell script ⇲

Complexity: | medium
Disruption: | low
Reboot: | false
Strategy: | disable

    if [[ -f /usr/sbin/prelink ]];
    then
    prelink -ua
    fi

    DEBIAN_FRONTEND=noninteractive apt-get remove -y "prelink"

Remediation Ansible snippet ⇲

Complexity: | medium
Disruption: | low
Reboot: | false
Strategy: | disable

    - name: Check If Prelinked Is Installed
      ansible.builtin.stat:
        path: /usr/sbin/prelink
        get_checksum: false
      register: prelink
      tags:
      - disable_strategy
      - low_disruption
      - medium_complexity
      - medium_severity
      - no_reboot_needed
      - package_prelink_removed

    - name: Restore Prelinked Binaries
      ansible.builtin.command:
        cmd: prelink -ua
      when: prelink.stat.exists
      tags:
      - disable_strategy
      - low_disruption
      - medium_complexity
      - medium_severity
      - no_reboot_needed
      - package_prelink_removed

    - name: Ensure prelink is Removed
      ansible.builtin.package:
        name: prelink
        state: absent
      tags:
      - disable_strategy
      - low_disruption
      - medium_complexity
      - medium_severity
      - no_reboot_needed
      - package_prelink_removed

Remediation Puppet snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    include remove_prelink

    class remove_prelink {
      package { 'prelink':
        ensure => 'purged',
      }
    }

Group Disk Partitioning Group contains 1 rule

[ref] To ensure separation and protection of data, there are top-level system directories which should be placed on their own physical partition or logical volume. The installer's default partitioning scheme creates separate logical volumes for `/`, `/boot`, and `swap`.

- If starting with any of the default layouts, check the box to \"Review and modify partitioning.\" This allows for the easy creation of additional logical volumes inside the volume group already created, though it may require making `/`'s logical volume smaller to create space. In general, using logical volumes is preferable to using partitions because they can be more easily adjusted later.
- If creating a custom layout, create the partitions mentioned in the previous paragraph (which the installer will require anyway), as well as separate ones described in the following sections.

If a system has already been installed, and the default partitioning scheme was used, it is possible but nontrivial to modify it to create separate logical volumes for the directories listed above. The Logical Volume Manager (LVM) makes this possible.

#### Rule Ensure /tmp Located On Separate Partition [ref]

The `/tmp` directory is a world-writable directory used for temporary file storage. Ensure it has its own partition or logical volume at installation time, or migrate it using LVM.
Rationale: | The `/tmp` partition is used as temporary storage by many programs. Placing `/tmp` in its own partition enables the setting of more restrictive mount options, which can help protect programs which use it.
Severity: | low
Rule ID: | xccdf_org.ssgproject.content_rule_partition_for_tmp

References:

cis-csc | 12, 15, 8
cobit5 | APO13.01, DSS05.02
disa | CCI-000366
isa-62443-2013 | SR 3.1, SR 3.5, SR 3.8, SR 4.1, SR 4.3, SR 5.1, SR 5.2, SR 5.3, SR 7.1, SR 7.6
iso27001-2013 | A.13.1.1, A.13.2.1, A.14.1.3
nist | CM-6(a), SC-5(2)
nist-csf | PR.PT-4
os-srg | SRG-OS-000480-GPOS-00227
cis | 1.1.2

Group GNOME Desktop Environment Group contains 1 rule

[ref] GNOME is a graphical desktop environment bundled with many Linux distributions that allow users to easily interact with the operating system graphically rather than textually. The GNOME Graphical Display Manager (GDM) provides login, logout, and user switching contexts as well as display server management.
GNOME is developed by the GNOME Project and is considered the default Red Hat Graphical environment.
For more information on GNOME and the GNOME Project, see https://www.gnome.org.

#### Rule Remove the GDM Package Group [ref]

By removing the `gdm3` package, the system no longer has GNOME installed installed. If X Windows is not installed then the system cannot boot into graphical user mode. This prevents the system from being accidentally or maliciously booted into a `graphical.target` mode. To do so, run the following command:

    $ sudo apt remove gdm3

Rationale: | Unnecessary service packages must not be installed to decrease the attack surface of the system. A graphical environment is unnecessary for certain types of systems including a virtualization hypervisor.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_package_gdm_removed

References:

disa | CCI-000366
nist | CM-7(a), CM-7(b), CM-6(a)
os-srg | SRG-OS-000480-GPOS-00227
cis | 1.10

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}\n' 'gdm3' 2>/dev/null | grep -q '^installed'; then

    # CAUTION: This remediation script will remove gdm3
    #	   from the system, and may remove any packages
    #	   that depend on gdm3. Execute this
    #	   remediation AFTER testing on a non-production
    #	   system!

    DEBIAN_FRONTEND=noninteractive apt-get remove -y "gdm3"

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - disable_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - package_gdm_removed

    - name: Ensure gdm3 is removed
      package:
        name: gdm3
        state: absent
      when: '"gdm3" in ansible_facts.packages'
      tags:
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - disable_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - package_gdm_removed

Remediation Puppet snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    include remove_gdm3

    class remove_gdm3 {
      package { 'gdm3':
        ensure => 'purged',
      }
    }

Group Sudo Group contains 3 rules

[ref] `Sudo`, which stands for "su 'do'", provides the ability to delegate authority to certain users, groups of users, or system administrators. When configured for system users and/or groups, `Sudo` can allow a user or group to execute privileged commands that normally only `root` is allowed to execute.
For more information on `Sudo` and addition `Sudo` configuration options, see https://www.sudo.ws.

#### Rule Install sudo Package [ref]

The `sudo` package can be installed with the following command:

    $ apt-get install sudo

Rationale: | `sudo` is a program designed to allow a system administrator to give limited root privileges to users and log root activity. The basic philosophy is to give as few privileges as possible but still allow system users to get their work done.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_package_sudo_installed

References:

disa | CCI-002235
ism | 1382, 1384, 1386
nist | CM-6(a)
ospp | FMT_MOF_EXT.1
os-srg | SRG-OS-000324-GPOS-00125
cis | 1.3.1
anssi | R33
pcidss4 | 2.2.6, 2.2

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | enable

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    DEBIAN_FRONTEND=noninteractive apt-get install -y "sudo"

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation OSBuild Blueprint snippet ⇲

    [[packages]]
    name = "sudo"
    version = "*"

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | enable

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - NIST-800-53-CM-6(a)
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - enable_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - package_sudo_installed

    - name: Ensure sudo is installed
      package:
        name: sudo
        state: present
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-53-CM-6(a)
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - enable_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - package_sudo_installed

Remediation Puppet snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | enable

    include install_sudo

    class install_sudo {
      package { 'sudo':
        ensure => 'installed',
      }
    }

#### Rule Ensure Only Users Logged In To Real tty Can Execute Sudo - sudo use_pty [ref]

The sudo `use_pty` tag, when specified, will only execute sudo commands from users logged in to a real tty. This should be enabled by making sure that the `use_pty` tag exists in `/etc/sudoers` configuration file or any sudo configuration snippets in `/etc/sudoers.d/`.
Rationale: | Requiring that sudo commands be run in a pseudo-terminal can prevent an attacker from retaining access to the user's terminal after the main program has finished executing.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_sudo_add_use_pty

References:

pcidss | Req-10.2.5
cis | 1.3.2
anssi | R39
pcidss4 | 2.2.6, 2.2

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | restrict

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}\n' 'sudo' 2>/dev/null | grep -q '^installed'; then

    if /usr/sbin/visudo -qcf /etc/sudoers; then
        cp /etc/sudoers /etc/sudoers.bak
        if ! grep -P '^[\s]*Defaults[\s]*\buse_pty\b.*$' /etc/sudoers; then
            # sudoers file doesn't define Option use_pty
            echo "Defaults use_pty" >> /etc/sudoers
        fi

        # Check validity of sudoers and cleanup bak
        if /usr/sbin/visudo -qcf /etc/sudoers; then
            rm -f /etc/sudoers.bak
        else
            echo "Fail to validate remediated /etc/sudoers, reverting to original file."
            mv /etc/sudoers.bak /etc/sudoers
            false
        fi
    else
        echo "Skipping remediation, /etc/sudoers failed to validate"
        false
    fi

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | restrict

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - PCI-DSS-Req-10.2.5
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy
      - sudo_add_use_pty

    - name: Ensure use_pty is enabled in /etc/sudoers
      lineinfile:
        path: /etc/sudoers
        regexp: ^[\s]*Defaults.*\buse_pty\b.*$
        line: Defaults use_pty
        validate: /usr/sbin/visudo -cf %s
      when: '"sudo" in ansible_facts.packages'
      tags:
      - PCI-DSS-Req-10.2.5
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy
      - sudo_add_use_pty

#### Rule Ensure Sudo Logfile Exists - sudo logfile [ref]

A custom log sudo file can be configured with the 'logfile' tag. This rule configures a sudo custom logfile at the default location suggested by CIS, which uses /var/log/sudo.log.
Rationale: | A sudo log file simplifies auditing of sudo commands.
Severity: | low
Rule ID: | xccdf_org.ssgproject.content_rule_sudo_custom_logfile

References:

pcidss | Req-10.2.5
cis | 1.3.3
pcidss4 | 2.2.6, 2.2

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | restrict

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}\n' 'sudo' 2>/dev/null | grep -q '^installed'; then

    var_sudo_logfile='/var/log/sudo.log'

    if /usr/sbin/visudo -qcf /etc/sudoers; then
        cp /etc/sudoers /etc/sudoers.bak
        if ! grep -P '^[\s]*Defaults[\s]*\blogfile\s*=\s*(?:"?([^",\s]+)"?)\b.*$' /etc/sudoers; then
            # sudoers file doesn't define Option logfile
            echo "Defaults logfile=${var_sudo_logfile}" >> /etc/sudoers
        else
            # sudoers file defines Option logfile, remediate if appropriate value is not set
            if ! grep -P "^[\s]*Defaults.*\blogfile=${var_sudo_logfile}\b.*$" /etc/sudoers; then

                escaped_variable=${var_sudo_logfile//$'/'/$'\/'}
                sed -Ei "s/(^[\s]*Defaults.*\blogfile=)[-]?.+(\b.*$)/\1$escaped_variable\2/" /etc/sudoers
            fi
        fi

        # Check validity of sudoers and cleanup bak
        if /usr/sbin/visudo -qcf /etc/sudoers; then
            rm -f /etc/sudoers.bak
        else
            echo "Fail to validate remediated /etc/sudoers, reverting to original file."
            mv /etc/sudoers.bak /etc/sudoers
            false
        fi
    else
        echo "Skipping remediation, /etc/sudoers failed to validate"
        false
    fi

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | restrict

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - PCI-DSS-Req-10.2.5
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - low_complexity
      - low_disruption
      - low_severity
      - no_reboot_needed
      - restrict_strategy
      - sudo_custom_logfile
    - name: XCCDF Value var_sudo_logfile # promote to variable
      set_fact:
        var_sudo_logfile: !!str /var/log/sudo.log
      tags:
        - always

    - name: Ensure logfile is enabled with the appropriate value in /etc/sudoers
      lineinfile:
        path: /etc/sudoers
        regexp: ^[\s]*Defaults\s(.*)\blogfile=[-]?.+\b(.*)$
        line: Defaults \1logfile={{ var_sudo_logfile }}\2
        validate: /usr/sbin/visudo -cf %s
        backrefs: true
      register: edit_sudoers_logfile_option
      when: '"sudo" in ansible_facts.packages'
      tags:
      - PCI-DSS-Req-10.2.5
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - low_complexity
      - low_disruption
      - low_severity
      - no_reboot_needed
      - restrict_strategy
      - sudo_custom_logfile

    - name: Enable logfile option with appropriate value in /etc/sudoers
      lineinfile:
        path: /etc/sudoers
        line: Defaults logfile={{ var_sudo_logfile }}
        validate: /usr/sbin/visudo -cf %s
      when:
      - '"sudo" in ansible_facts.packages'
      - edit_sudoers_logfile_option is defined and not edit_sudoers_logfile_option.changed
      tags:
      - PCI-DSS-Req-10.2.5
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - low_complexity
      - low_disruption
      - low_severity
      - no_reboot_needed
      - restrict_strategy
      - sudo_custom_logfile

Group Account and Access Control Group contains 13 groups and 58 rules

[ref] In traditional Unix security, if an attacker gains shell access to a certain login account, they can perform any action or access any file to which that account has access. Therefore, making it more difficult for unauthorized people to gain shell access to accounts, particularly to privileged accounts, is a necessary part of securing a system. This section introduces mechanisms for restricting access to accounts under Ubuntu 20.04.

Group Warning Banners for System Accesses Group contains 12 rules

[ref] Each system should expose as little information about itself as possible.
System banners, which are typically displayed just before a login prompt, give out information about the service or the host's operating system. This might include the distribution name and the system kernel version, and the particular version of a network service. This information can assist intruders in gaining access to the system as it can reveal whether the system is running vulnerable software. Most network services can be configured to limit what information is displayed.
Many organizations implement security policies that require a system banner provide notice of the system's ownership, provide warning to unauthorized users, and remind authorized users of their consent to monitoring.

#### Rule Modify the System Login Banner [ref]

To configure the system login banner edit `/etc/issue`. Replace the default text with a message compliant with the local site policy or a legal disclaimer. The DoD required text is either:
`You are accessing a U.S. Government (USG) Information System (IS) that is provided for USG-authorized use only. By using this IS (which includes any device attached to this IS), you consent to the following conditions:
-The USG routinely intercepts and monitors communications on this IS for purposes including, but not limited to, penetration testing, COMSEC monitoring, network operations and defense, personnel misconduct (PM), law enforcement (LE), and counterintelligence (CI) investigations.
-At any time, the USG may inspect and seize data stored on this IS.
-Communications using, or data stored on, this IS are not private, are subject to routine monitoring, interception, and search, and may be disclosed or used for any USG-authorized purpose.
-This IS includes security measures (e.g., authentication and access controls) to protect USG interests -- not for your personal benefit or privacy.
-Notwithstanding the above, using this IS does not constitute consent to PM, LE or CI investigative searching or monitoring of the content of privileged communications, or work product, related to personal representation or services by attorneys, psychotherapists, or clergy, and their assistants. Such communications and work product are private and confidential. See User Agreement for details.`
OR:
`I've read & consent to terms in IS user agreem't.`

Rationale:

Display of a standardized and approved use notification before granting access to the operating system ensures privacy and security notification verbiage used is consistent with applicable federal laws, Executive Orders, directives, policies, regulations, standards, and guidance.
System use notifications are required only for access via login interfaces with human users and are not required when such human interfaces do not exist.

Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_banner_etc_issue

References:

cis-csc | 1, 12, 15, 16
cobit5 | DSS05.04, DSS05.10, DSS06.10
cui | 3.1.9
disa | CCI-001387, CCI-001384, CCI-000048, CCI-001386, CCI-001388, CCI-001385
isa-62443-2009 | 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9
isa-62443-2013 | SR 1.1, SR 1.10, SR 1.2, SR 1.5, SR 1.7, SR 1.8, SR 1.9
iso27001-2013 | A.18.1.4, A.9.2.1, A.9.2.4, A.9.3.1, A.9.4.2, A.9.4.3
nist | AC-8(a), AC-8(c)
nist-csf | PR.AC-7
os-srg | SRG-OS-000023-GPOS-00006, SRG-OS-000228-GPOS-00088
cis | 1.8.1.2

Remediation Shell script ⇲

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    login_banner_text='^Authorized[\s\n]+users[\s\n]+only\.[\s\n]+All[\s\n]+activity[\s\n]+may[\s\n]+be[\s\n]+monitored[\s\n]+and[\s\n]+reported\.$'

    # Multiple regexes transform the banner regex into a usable banner
    # 0 - Remove anchors around the banner text
    login_banner_text=$(echo "$login_banner_text" | sed 's/^\^\(.*\)\$$/\1/g')
    # 1 - Keep only the first banners if there are multiple
    #    (dod_banners contains the long and short banner)
    login_banner_text=$(echo "$login_banner_text" | sed 's/^(\(.*\.\)|.*)$/\1/g')
    # 2 - Add spaces ' '. (Transforms regex for "space or newline" into a " ")
    login_banner_text=$(echo "$login_banner_text" | sed 's/\[\\s\\n\]+/ /g')
    # 3 - Adds newlines. (Transforms "(?:\[\\n\]+|(?:\\n)+)" into "\n")
    login_banner_text=$(echo "$login_banner_text" | sed 's/(?:\[\\n\]+|(?:\\\\n)+)/\n/g')
    # 4 - Remove any leftover backslash. (From any parethesis in the banner, for example).
    login_banner_text=$(echo "$login_banner_text" | sed 's/\\//g')
    formatted=$(echo "$login_banner_text" | fold -sw 80)
    cat <<EOF >/etc/issue
    $formatted
    EOF

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

#### Rule Modify the System Login Banner for Remote Connections [ref]

To configure the system login banner edit `/etc/issue.net`. Replace the default text with a message compliant with the local site policy or a legal disclaimer. The DoD required text is either:
`You are accessing a U.S. Government (USG) Information System (IS) that is provided for USG-authorized use only. By using this IS (which includes any device attached to this IS), you consent to the following conditions:
-The USG routinely intercepts and monitors communications on this IS for purposes including, but not limited to, penetration testing, COMSEC monitoring, network operations and defense, personnel misconduct (PM), law enforcement (LE), and counterintelligence (CI) investigations.
-At any time, the USG may inspect and seize data stored on this IS.
-Communications using, or data stored on, this IS are not private, are subject to routine monitoring, interception, and search, and may be disclosed or used for any USG-authorized purpose.
-This IS includes security measures (e.g., authentication and access controls) to protect USG interests -- not for your personal benefit or privacy.
-Notwithstanding the above, using this IS does not constitute consent to PM, LE or CI investigative searching or monitoring of the content of privileged communications, or work product, related to personal representation or services by attorneys, psychotherapists, or clergy, and their assistants. Such communications and work product are private and confidential. See User Agreement for details.`
OR:
`I've read & consent to terms in IS user agreem't.`

Rationale:

Display of a standardized and approved use notification before granting access to the operating system ensures privacy and security notification verbiage used is consistent with applicable federal laws, Executive Orders, directives, policies, regulations, standards, and guidance.
System use notifications are required only for access via login interfaces with human users and are not required when such human interfaces do not exist.

Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_banner_etc_issue_net

References:

disa | CCI-000048, CCI-001384, CCI-001385, CCI-001386, CCI-001387, CCI-001388
os-srg | SRG-OS-000023-GPOS-00006, SRG-OS-000228-GPOS-00088
stigid | UBTU-20-010038
cis | 1.8.1.3
stigref | SV-238214r951471_rule

Remediation Shell script ⇲

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    remote_login_banner_text='^Authorized[\s\n]+uses[\s\n]+only\.[\s\n]+All[\s\n]+activity[\s\n]+may[\s\n]+be[\s\n]+monitored[\s\n]+and[\s\n]+reported\.$'

    # Multiple regexes transform the banner regex into a usable banner
    # 0 - Remove anchors around the banner text
    remote_login_banner_text=$(echo "$remote_login_banner_text" | sed 's/^\^\(.*\)\$$/\1/g')
    # 1 - Keep only the first banners if there are multiple
    #    (dod_banners contains the long and short banner)
    remote_login_banner_text=$(echo "$remote_login_banner_text" | sed 's/^(\(.*\.\)|.*)$/\1/g')
    # 2 - Add spaces ' '. (Transforms regex for "space or newline" into a " ")
    remote_login_banner_text=$(echo "$remote_login_banner_text" | sed 's/\[\\s\\n\]+/ /g')
    # 3 - Adds newlines. (Transforms "(?:\[\\n\]+|(?:\\n)+)" into "\n")
    remote_login_banner_text=$(echo "$remote_login_banner_text" | sed 's/(?:\[\\n\]+|(?:\\\\n)+)/\n/g')
    # 4 - Remove any leftover backslash. (From any parethesis in the banner, for example).
    remote_login_banner_text=$(echo "$remote_login_banner_text" | sed 's/\\//g')
    formatted=$(echo "$remote_login_banner_text" | fold -sw 80)

    cat <<EOF >/etc/issue.net
    $formatted
    EOF

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | medium
Reboot: | false
Strategy: | unknown

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - DISA-STIG-UBTU-20-010038
      - banner_etc_issue_net
      - low_complexity
      - medium_disruption
      - medium_severity
      - no_reboot_needed
      - unknown_strategy
    - name: XCCDF Value remote_login_banner_text # promote to variable
      set_fact:
        remote_login_banner_text: !!str ^Authorized[\s\n]+uses[\s\n]+only\.[\s\n]+All[\s\n]+activity[\s\n]+may[\s\n]+be[\s\n]+monitored[\s\n]+and[\s\n]+reported\.$
      tags:
        - always

    - name: Modify the System Login Banner for Remote Connections - ensure correct banner
      copy:
        dest: /etc/issue.net
        content: '{{ remote_login_banner_text | regex_replace("^\^(.*)\$$", "\1") | regex_replace("^\((.*\.)\|.*\)$",
          "\1") | regex_replace("\[\\s\\n\]\+"," ") | regex_replace("\(\?:\[\\n\]\+\|\(\?:\\\\n\)\+\)",
          "\n") | regex_replace("\\", "") | wordwrap() }}'
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - DISA-STIG-UBTU-20-010038
      - banner_etc_issue_net
      - low_complexity
      - medium_disruption
      - medium_severity
      - no_reboot_needed
      - unknown_strategy

#### Rule Modify the System Message of the Day Banner [ref]

To configure the system message banner edit `/etc/motd`. Replace the default text with a message compliant with the local site policy or a legal disclaimer. The DoD required text is either:
`You are accessing a U.S. Government (USG) Information System (IS) that is provided for USG-authorized use only. By using this IS (which includes any device attached to this IS), you consent to the following conditions:
-The USG routinely intercepts and monitors communications on this IS for purposes including, but not limited to, penetration testing, COMSEC monitoring, network operations and defense, personnel misconduct (PM), law enforcement (LE), and counterintelligence (CI) investigations.
-At any time, the USG may inspect and seize data stored on this IS.
-Communications using, or data stored on, this IS are not private, are subject to routine monitoring, interception, and search, and may be disclosed or used for any USG-authorized purpose.
-This IS includes security measures (e.g., authentication and access controls) to protect USG interests -- not for your personal benefit or privacy.
-Notwithstanding the above, using this IS does not constitute consent to PM, LE or CI investigative searching or monitoring of the content of privileged communications, or work product, related to personal representation or services by attorneys, psychotherapists, or clergy, and their assistants. Such communications and work product are private and confidential. See User Agreement for details.`
OR:
`I've read & consent to terms in IS user agreem't.`

Rationale:

Display of a standardized and approved use notification before granting access to the operating system ensures privacy and security notification verbiage used is consistent with applicable federal laws, Executive Orders, directives, policies, regulations, standards, and guidance.
System use notifications are required only for access via login interfaces with human users and are not required when such human interfaces do not exist.

Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_banner_etc_motd

References:

cis | 1.8.1.1

Remediation Shell script ⇲

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    motd_banner_text='^Authorized[\s\n]+uses[\s\n]+only\.[\s\n]+All[\s\n]+activity[\s\n]+may[\s\n]+be[\s\n]+monitored[\s\n]+and[\s\n]+reported\.$'

    # Multiple regexes transform the banner regex into a usable banner
    # 0 - Remove anchors around the banner text
    motd_banner_text=$(echo "$motd_banner_text" | sed 's/^\^\(.*\)\$$/\1/g')
    # 1 - Keep only the first banners if there are multiple
    #    (dod_banners contains the long and short banner)
    motd_banner_text=$(echo "$motd_banner_text" | sed 's/^(\(.*\.\)|.*)$/\1/g')
    # 2 - Add spaces ' '. (Transforms regex for "space or newline" into a " ")
    motd_banner_text=$(echo "$motd_banner_text" | sed 's/\[\\s\\n\]+/ /g')
    # 3 - Adds newlines. (Transforms "(?:\[\\n\]+|(?:\\n)+)" into "\n")
    motd_banner_text=$(echo "$motd_banner_text" | sed 's/(?:\[\\n\]+|(?:\\\\n)+)/\n/g')
    # 4 - Remove any leftover backslash. (From any parethesis in the banner, for example).
    motd_banner_text=$(echo "$motd_banner_text" | sed 's/\\//g')
    formatted=$(echo "$motd_banner_text" | fold -sw 80)

    cat <<EOF >/etc/motd
    $formatted
    EOF

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

#### Rule Verify Group Ownership of System Login Banner [ref]

To properly set the group owner of `/etc/issue`, run the command:

    $ sudo chgrp root /etc/issue

Rationale: | Display of a standardized and approved use notification before granting access to the operating system ensures privacy and security notification verbiage used is consistent with applicable federal laws, Executive Orders, directives, policies, regulations, standards, and guidance. Proper group ownership will ensure that only root user can modify the banner.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_file_groupowner_etc_issue

References:

cis | 1.8.1.5

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    chgrp 0 /etc/issue

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    - name: Test for existence /etc/issue
      stat:
        path: /etc/issue
      register: file_exists
      tags:
      - configure_strategy
      - file_groupowner_etc_issue
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Ensure group owner 0 on /etc/issue
      file:
        path: /etc/issue
        group: '0'
      when: file_exists.stat is defined and file_exists.stat.exists
      tags:
      - configure_strategy
      - file_groupowner_etc_issue
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

#### Rule Verify Group Ownership of System Login Banner for Remote Connections [ref]

To properly set the group owner of `/etc/issue.net`, run the command:

    $ sudo chgrp root /etc/issue.net

Rationale: | Display of a standardized and approved use notification before granting access to the operating system ensures privacy and security notification verbiage used is consistent with applicable federal laws, Executive Orders, directives, policies, regulations, standards, and guidance. Proper group ownership will ensure that only root user can modify the banner.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_file_groupowner_etc_issue_net

References:

cis | 1.8.1.6
pcidss4 | 1.2.8, 1.2

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    chgrp 0 /etc/issue.net

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    - name: Test for existence /etc/issue.net
      stat:
        path: /etc/issue.net
      register: file_exists
      tags:
      - PCI-DSSv4-1.2
      - PCI-DSSv4-1.2.8
      - configure_strategy
      - file_groupowner_etc_issue_net
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Ensure group owner 0 on /etc/issue.net
      file:
        path: /etc/issue.net
        group: '0'
      when: file_exists.stat is defined and file_exists.stat.exists
      tags:
      - PCI-DSSv4-1.2
      - PCI-DSSv4-1.2.8
      - configure_strategy
      - file_groupowner_etc_issue_net
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

#### Rule Verify Group Ownership of Message of the Day Banner [ref]

To properly set the group owner of `/etc/motd`, run the command:

    $ sudo chgrp root /etc/motd

Rationale: | Display of a standardized and approved use notification before granting access to the operating system ensures privacy and security notification verbiage used is consistent with applicable federal laws, Executive Orders, directives, policies, regulations, standards, and guidance. Proper group ownership will ensure that only root user can modify the banner.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_file_groupowner_etc_motd

References:

cis | 1.8.1.4

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    chgrp 0 /etc/motd

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    - name: Test for existence /etc/motd
      stat:
        path: /etc/motd
      register: file_exists
      tags:
      - configure_strategy
      - file_groupowner_etc_motd
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Ensure group owner 0 on /etc/motd
      file:
        path: /etc/motd
        group: '0'
      when: file_exists.stat is defined and file_exists.stat.exists
      tags:
      - configure_strategy
      - file_groupowner_etc_motd
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

#### Rule Verify ownership of System Login Banner [ref]

To properly set the owner of `/etc/issue`, run the command:

    $ sudo chown root /etc/issue

Rationale: | Display of a standardized and approved use notification before granting access to the operating system ensures privacy and security notification verbiage used is consistent with applicable federal laws, Executive Orders, directives, policies, regulations, standards, and guidance. Proper ownership will ensure that only root user can modify the banner.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_file_owner_etc_issue

References:

cis | 1.8.1.5

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    chown 0 /etc/issue

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    - name: Test for existence /etc/issue
      stat:
        path: /etc/issue
      register: file_exists
      tags:
      - configure_strategy
      - file_owner_etc_issue
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Ensure owner 0 on /etc/issue
      file:
        path: /etc/issue
        owner: '0'
      when: file_exists.stat is defined and file_exists.stat.exists
      tags:
      - configure_strategy
      - file_owner_etc_issue
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

#### Rule Verify ownership of System Login Banner for Remote Connections [ref]

To properly set the owner of `/etc/issue.net`, run the command:

    $ sudo chown root /etc/issue.net

Rationale: | Display of a standardized and approved use notification before granting access to the operating system ensures privacy and security notification verbiage used is consistent with applicable federal laws, Executive Orders, directives, policies, regulations, standards, and guidance. Proper ownership will ensure that only root user can modify the banner.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_file_owner_etc_issue_net

References:

cis | 1.8.1.6
pcidss4 | 1.2.8, 1.2

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    chown 0 /etc/issue.net

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    - name: Test for existence /etc/issue.net
      stat:
        path: /etc/issue.net
      register: file_exists
      tags:
      - PCI-DSSv4-1.2
      - PCI-DSSv4-1.2.8
      - configure_strategy
      - file_owner_etc_issue_net
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Ensure owner 0 on /etc/issue.net
      file:
        path: /etc/issue.net
        owner: '0'
      when: file_exists.stat is defined and file_exists.stat.exists
      tags:
      - PCI-DSSv4-1.2
      - PCI-DSSv4-1.2.8
      - configure_strategy
      - file_owner_etc_issue_net
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

#### Rule Verify ownership of Message of the Day Banner [ref]

To properly set the owner of `/etc/motd`, run the command:

    $ sudo chown root /etc/motd

Rationale: | Display of a standardized and approved use notification before granting access to the operating system ensures privacy and security notification verbiage used is consistent with applicable federal laws, Executive Orders, directives, policies, regulations, standards, and guidance. Proper ownership will ensure that only root user can modify the banner.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_file_owner_etc_motd

References:

cis | 1.8.1.4

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    chown 0 /etc/motd

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    - name: Test for existence /etc/motd
      stat:
        path: /etc/motd
      register: file_exists
      tags:
      - configure_strategy
      - file_owner_etc_motd
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Ensure owner 0 on /etc/motd
      file:
        path: /etc/motd
        owner: '0'
      when: file_exists.stat is defined and file_exists.stat.exists
      tags:
      - configure_strategy
      - file_owner_etc_motd
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

#### Rule Verify permissions on System Login Banner [ref]

To properly set the permissions of `/etc/issue`, run the command:

    $ sudo chmod 0644 /etc/issue

Rationale: | Display of a standardized and approved use notification before granting access to the operating system ensures privacy and security notification verbiage used is consistent with applicable federal laws, Executive Orders, directives, policies, regulations, standards, and guidance. Proper permissions will ensure that only root user can modify the banner.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_file_permissions_etc_issue

References:

cis | 1.8.1.5

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    chmod u-xs,g-xws,o-xwt /etc/issue

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    - name: Test for existence /etc/issue
      stat:
        path: /etc/issue
      register: file_exists
      tags:
      - configure_strategy
      - file_permissions_etc_issue
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Ensure permission u-xs,g-xws,o-xwt on /etc/issue
      file:
        path: /etc/issue
        mode: u-xs,g-xws,o-xwt
      when: file_exists.stat is defined and file_exists.stat.exists
      tags:
      - configure_strategy
      - file_permissions_etc_issue
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

#### Rule Verify permissions on System Login Banner for Remote Connections [ref]

To properly set the permissions of `/etc/issue.net`, run the command:

    $ sudo chmod 0644 /etc/issue.net

Rationale: | Display of a standardized and approved use notification before granting access to the operating system ensures privacy and security notification verbiage used is consistent with applicable federal laws, Executive Orders, directives, policies, regulations, standards, and guidance. Proper permissions will ensure that only root user can modify the banner.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_file_permissions_etc_issue_net

References:

cis | 1.8.1.6
pcidss4 | 1.2.8, 1.2

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    chmod u-xs,g-xws,o-xwt /etc/issue.net

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    - name: Test for existence /etc/issue.net
      stat:
        path: /etc/issue.net
      register: file_exists
      tags:
      - PCI-DSSv4-1.2
      - PCI-DSSv4-1.2.8
      - configure_strategy
      - file_permissions_etc_issue_net
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Ensure permission u-xs,g-xws,o-xwt on /etc/issue.net
      file:
        path: /etc/issue.net
        mode: u-xs,g-xws,o-xwt
      when: file_exists.stat is defined and file_exists.stat.exists
      tags:
      - PCI-DSSv4-1.2
      - PCI-DSSv4-1.2.8
      - configure_strategy
      - file_permissions_etc_issue_net
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

#### Rule Verify permissions on Message of the Day Banner [ref]

To properly set the permissions of `/etc/motd`, run the command:

    $ sudo chmod 0644 /etc/motd

Rationale: | Display of a standardized and approved use notification before granting access to the operating system ensures privacy and security notification verbiage used is consistent with applicable federal laws, Executive Orders, directives, policies, regulations, standards, and guidance. Proper permissions will ensure that only root user can modify the banner.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_file_permissions_etc_motd

References:

cis | 1.8.1.4

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    chmod u-xs,g-xws,o-xwt /etc/motd

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    - name: Test for existence /etc/motd
      stat:
        path: /etc/motd
      register: file_exists
      tags:
      - configure_strategy
      - file_permissions_etc_motd
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Ensure permission u-xs,g-xws,o-xwt on /etc/motd
      file:
        path: /etc/motd
        mode: u-xs,g-xws,o-xwt
      when: file_exists.stat is defined and file_exists.stat.exists
      tags:
      - configure_strategy
      - file_permissions_etc_motd
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

Group Protect Accounts by Configuring PAM Group contains 3 groups and 10 rules

[ref] PAM, or Pluggable Authentication Modules, is a system which implements modular authentication for Linux programs. PAM provides a flexible and configurable architecture for authentication, and it should be configured to minimize exposure to unnecessary risk. This section contains guidance on how to accomplish that.
PAM is implemented as a set of shared objects which are loaded and invoked whenever an application wishes to authenticate a user. Typically, the application must be running as root in order to take advantage of PAM, because PAM's modules often need to be able to access sensitive stores of account information, such as /etc/shadow. Traditional privileged network listeners (e.g. sshd) or SUID programs (e.g. sudo) already meet this requirement. An SUID root application, userhelper, is provided so that programs which are not SUID or privileged themselves can still take advantage of PAM.
PAM looks in the directory `/etc/pam.d` for application-specific configuration information. For instance, if the program login attempts to authenticate a user, then PAM's libraries follow the instructions in the file `/etc/pam.d/login` to determine what actions should be taken.
One very important file in `/etc/pam.d` is `/etc/pam.d/system-auth`. This file, which is included by many other PAM configuration files, defines 'default' system authentication measures. Modifying this file is a good way to make far-reaching authentication changes, for instance when implementing a centralized authentication service.
Warning: Be careful when making changes to PAM's configuration files. The syntax for these files is complex, and modifications can have unexpected consequences. The default configurations shipped with applications should be sufficient for most users.
Warning: Running `authconfig` or `system-config-authentication` will re-write the PAM configuration files, destroying any manually made changes and replacing them with a series of system defaults. One reference to the configuration file syntax can be found at https://fossies.org/linux/Linux-PAM-docs/doc/sag/Linux-PAM_SAG.pdf.

Group Set Lockouts for Failed Password Attempts Group contains 2 rules

[ref] The `pam_faillock` PAM module provides the capability to lock out user accounts after a number of failed login attempts. Its documentation is available in `/usr/share/doc/pam-VERSION/txts/README.pam_faillock`.
Warning: Locking out user accounts presents the risk of a denial-of-service attack. The lockout policy must weigh whether the risk of such a denial-of-service attack outweighs the benefits of thwarting password guessing attacks.

#### Rule Limit Password Reuse [ref]

Do not allow users to reuse recent passwords. This can be accomplished by using the `remember` option for the `pam_pwhistory` PAM modules.
In the file `/etc/pam.d/common-password`, make sure the parameters `remember` and `use_authtok` are present, and that the value for the `remember` parameter is 5 or greater. For example:

    password requisite pam_pwhistory.so ...existing_options... remember=5 use_authtok

The DoD STIG requirement is 5 passwords.

Rationale: | Preventing re-use of previous passwords helps ensure that a compromised password is not re-used by a user.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_accounts_password_pam_pwhistory_remember

References:

disa | CCI-000200
os-srg | SRG-OS-000077-GPOS-00045
cis | 5.3.3

Remediation Shell script ⇲

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}\n' 'libpam-runtime' 2>/dev/null | grep -q '^installed'; then

    if [ -f /usr/bin/authselect ]; then
        if authselect list-features sssd | grep -q with-pwhistory; then
            if ! authselect check; then
            echo "
            authselect integrity check failed. Remediation aborted!
            This remediation could not be applied because an authselect profile was not selected or the selected profile is not intact.
            It is not recommended to manually edit the PAM files when authselect tool is available.
            In cases where the default authselect profile does not cover a specific demand, a custom authselect profile is recommended."
            exit 1
            fi
            authselect enable-feature with-pwhistory

            authselect apply-changes -b
        else

            if ! authselect check; then
            echo "
            authselect integrity check failed. Remediation aborted!
            This remediation could not be applied because an authselect profile was not selected or the selected profile is not intact.
            It is not recommended to manually edit the PAM files when authselect tool is available.
            In cases where the default authselect profile does not cover a specific demand, a custom authselect profile is recommended."
            exit 1
            fi

            CURRENT_PROFILE=$(authselect current -r | awk '{ print $1 }')
            # If not already in use, a custom profile is created preserving the enabled features.
            if [[ ! $CURRENT_PROFILE == custom/* ]]; then
                ENABLED_FEATURES=$(authselect current | tail -n+3 | awk '{ print $2 }')
                # The "local" profile does not contain essential security features required by multiple Benchmarks.
                # If currently used, it is replaced by "sssd", which is the best option in this case.
                if [[ $CURRENT_PROFILE == local ]]; then
                    CURRENT_PROFILE="sssd"
                fi
                authselect create-profile hardening -b $CURRENT_PROFILE
                CURRENT_PROFILE="custom/hardening"

                authselect apply-changes -b --backup=before-hardening-custom-profile
                authselect select $CURRENT_PROFILE
                for feature in $ENABLED_FEATURES; do
                    authselect enable-feature $feature;
                done

                authselect apply-changes -b --backup=after-hardening-custom-profile
            fi
            PAM_FILE_NAME=$(basename "cac_pwhistory")
            PAM_FILE_PATH="/etc/authselect/$CURRENT_PROFILE/$PAM_FILE_NAME"

            authselect apply-changes -b

            if ! grep -qP "^\s*password\s+requisite\s+pam_pwhistory.so\s*.*" "$PAM_FILE_PATH"; then
                # Line matching group + control + module was not found. Check group + module.
                if [ "$(grep -cP '^\s*password\s+.*\s+pam_pwhistory.so\s*' "$PAM_FILE_PATH")" -eq 1 ]; then
                    # The control is updated only if one single line matches.
                    sed -i -E --follow-symlinks "s/^(\s*password\s+).*(\bpam_pwhistory.so.*)/\1requisite \2/" "$PAM_FILE_PATH"
                else
                    echo "password    requisite    pam_pwhistory.so" >> "$PAM_FILE_PATH"
                fi
            fi
        fi
    else

    conf_name=cac_pwhistory
    conf_path="/usr/share/pam-configs"

    if [ ! -f "$conf_path"/"$conf_name" ]; then
        cat << EOF > "$conf_path"/"$conf_name"
    Name: pwhistory password history checking
    Default: yes
    Priority: 1024
    Password-Type: Primary
    Password: requisite pam_pwhistory.so remember=24 enforce_for_root try_first_pass use_authtok
    Password-Initial: requisite pam_pwhistory.so remember=24 enforce_for_root try_first_pass
    EOF
    fi

    DEBIAN_FRONTEND=noninteractive pam-auth-update

    fi

    var_password_pam_remember='5'

    sed -i -E '/^Password:/,/^[^[:space:]]/ {
        /pam_pwhistory\.so/ {
            s/\s*remember=[^[:space:]]*//g
            s/$/ remember='"$var_password_pam_remember"'/g
        }
    }' /usr/share/pam-configs/cac_pwhistory

    sed -i -E '/^Password-Initial:/,/^[^[:space:]]/ {
        /pam_pwhistory\.so/ {
            s/\s*remember=[^[:space:]]*//g
            s/$/ remember='"$var_password_pam_remember"'/g
        }
    }' /usr/share/pam-configs/cac_pwhistory

    DEBIAN_FRONTEND=noninteractive pam-auth-update --enable cac_pwhistory

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

#### Rule Set Deny For Failed Password Attempts [ref]

The Ubuntu 20.04 operating system must lock an account after - at most - 5 consecutive invalid access attempts.

Rationale:

By limiting the number of failed logon attempts, the risk of unauthorized system access via user password guessing, otherwise known as brute-force attacks, is reduced. Limits are imposed by locking the account. To configure the operating system to lock an account after three unsuccessful consecutive access attempts using `pam_tally2.so`, modify the content of both `/etc/pam.d/common-auth` and `/etc/pam.d/common-account` as follows:

- add or modify the `pam_tally2.so` module line in `/etc/pam.d/common-auth` to ensure both `onerr=fail` and `deny=5` are present. For example:

      auth required pam_tally2.so onerr=fail silent audit deny=5

- add or modify the following line in `/etc/pam.d/common-account`:

      account required pam_tally2.so

Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_accounts_passwords_pam_tally2

References:

disa | CCI-000044
pcidss | Req-8.1.6
os-srg | SRG-OS-000021-GPOS-00005
cis | 5.3.2
anssi | R31
pcidss4 | 8.3.4, 8.3

Remediation Shell script ⇲

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}\n' 'libpam-runtime' 2>/dev/null | grep -q '^installed'; then

    var_password_pam_tally2='5'

    # Use a non-number regexp to force update of the value of the deny option

    if ! grep -qP "^\s*auth\s+required\s+pam_tally2.so\s*.*" "/etc/pam.d/common-auth"; then
        # Line matching group + control + module was not found. Check group + module.
        if [ "$(grep -cP '^\s*auth\s+.*\s+pam_tally2.so\s*' "/etc/pam.d/common-auth")" -eq 1 ]; then
            # The control is updated only if one single line matches.
            sed -i -E --follow-symlinks "s/^(\s*auth\s+).*(\bpam_tally2.so.*)/\1required \2/" "/etc/pam.d/common-auth"
        else
            echo "auth    required    pam_tally2.so" >> "/etc/pam.d/common-auth"
        fi
    fi
    # Check the option
    if ! grep -qP "^\s*auth\s+required\s+pam_tally2.so\s*.*\sdeny\b" "/etc/pam.d/common-auth"; then
        sed -i -E --follow-symlinks "/\s*auth\s+required\s+pam_tally2.so.*/ s/$/ deny=${var_password_pam_tally2}/" "/etc/pam.d/common-auth"
    else
        sed -i -E --follow-symlinks "s/(\s*auth\s+required\s+pam_tally2.so\s+.*)(deny=)[[:alnum:]]+\s*(.*)/\1\2${var_password_pam_tally2} \3/" "/etc/pam.d/common-auth"
    fi

    if ! grep -qP "^\s*auth\s+required\s+pam_tally2.so\s*.*" "/etc/pam.d/common-auth"; then
        # Line matching group + control + module was not found. Check group + module.
        if [ "$(grep -cP '^\s*auth\s+.*\s+pam_tally2.so\s*' "/etc/pam.d/common-auth")" -eq 1 ]; then
            # The control is updated only if one single line matches.
            sed -i -E --follow-symlinks "s/^(\s*auth\s+).*(\bpam_tally2.so.*)/\1required \2/" "/etc/pam.d/common-auth"
        else
            LAST_MATCH_LINE=$(grep -nP "(fail)" "/etc/pam.d/common-auth" | tail -n 1 | cut -d: -f 1)
            if [ ! -z $LAST_MATCH_LINE ]; then
                sed -i --follow-symlinks $LAST_MATCH_LINE" a auth     required    pam_tally2.so" "/etc/pam.d/common-auth"
            else
                echo "auth    required    pam_tally2.so" >> "/etc/pam.d/common-auth"
            fi
        fi
    fi
    # Check the option
    if ! grep -qP "^\s*auth\s+required\s+pam_tally2.so\s*.*\sonerr\b" "/etc/pam.d/common-auth"; then
        sed -i -E --follow-symlinks "/\s*auth\s+required\s+pam_tally2.so.*/ s/$/ onerr=fail/" "/etc/pam.d/common-auth"
    else
        sed -i -E --follow-symlinks "s/(\s*auth\s+required\s+pam_tally2.so\s+.*)(onerr=)[[:alnum:]]+\s*(.*)/\1\2fail \3/" "/etc/pam.d/common-auth"
    fi

    if ! grep -qP "^\s*account\s+required\s+pam_tally2.so\s*.*" "/etc/pam.d/common-account"; then
        # Line matching group + control + module was not found. Check group + module.
        if [ "$(grep -cP '^\s*account\s+.*\s+pam_tally2.so\s*' "/etc/pam.d/common-account")" -eq 1 ]; then
            # The control is updated only if one single line matches.
            sed -i -E --follow-symlinks "s/^(\s*account\s+).*(\bpam_tally2.so.*)/\1required \2/" "/etc/pam.d/common-account"
        else
            echo "account    required    pam_tally2.so" >> "/etc/pam.d/common-account"
        fi
    fi
    # Check the option
    if ! grep -qP "^\s*account\s+required\s+pam_tally2.so\s*.*\s\b" "/etc/pam.d/common-account"; then
        sed -i -E --follow-symlinks "/\s*account\s+required\s+pam_tally2.so.*/ s/$/ /" "/etc/pam.d/common-account"
    fi

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - PCI-DSS-Req-8.1.6
      - PCI-DSSv4-8.3
      - PCI-DSSv4-8.3.4
      - accounts_passwords_pam_tally2
      - configure_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
    - name: XCCDF Value var_password_pam_tally2 # promote to variable
      set_fact:
        var_password_pam_tally2: !!str 5
      tags:
        - always

    - name: Set Deny For Failed Password Attempts - Define a fact for control already
        filtered in case filters are used
      ansible.builtin.set_fact:
        pam_module_control: required
      when: '"libpam-runtime" in ansible_facts.packages'
      tags:
      - PCI-DSS-Req-8.1.6
      - PCI-DSSv4-8.3
      - PCI-DSSv4-8.3.4
      - accounts_passwords_pam_tally2
      - configure_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Set Deny For Failed Password Attempts - Check if expected PAM module line
        is present in /etc/pam.d/common-auth
      ansible.builtin.lineinfile:
        path: /etc/pam.d/common-auth
        regexp: ^\s*auth\s+{{ pam_module_control | regex_escape() }}\s+pam_tally2.so\s*.*
        state: absent
      check_mode: true
      changed_when: false
      register: result_pam_line_present
      when: '"libpam-runtime" in ansible_facts.packages'
      tags:
      - PCI-DSS-Req-8.1.6
      - PCI-DSSv4-8.3
      - PCI-DSSv4-8.3.4
      - accounts_passwords_pam_tally2
      - configure_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Set Deny For Failed Password Attempts - Include or update the PAM module line
        in /etc/pam.d/common-auth
      block:

      - name: Set Deny For Failed Password Attempts - Check if required PAM module line
          is present in /etc/pam.d/common-auth with different control
        ansible.builtin.lineinfile:
          path: /etc/pam.d/common-auth
          regexp: ^\s*auth\s+.*\s+pam_tally2.so\s*
          state: absent
        check_mode: true
        changed_when: false
        register: result_pam_line_other_control_present

      - name: Set Deny For Failed Password Attempts - Ensure the correct control for the
          required PAM module line in /etc/pam.d/common-auth
        ansible.builtin.replace:
          dest: /etc/pam.d/common-auth
          regexp: ^(\s*auth\s+).*(\bpam_tally2.so.*)
          replace: \1{{ pam_module_control }} \2
        register: result_pam_module_edit
        when:
        - result_pam_line_other_control_present.found == 1

      - name: Set Deny For Failed Password Attempts - Ensure the required PAM module line
          is included in /etc/pam.d/common-auth
        ansible.builtin.lineinfile:
          dest: /etc/pam.d/common-auth
          line: auth    {{ pam_module_control }}    pam_tally2.so
        register: result_pam_module_add
        when:
        - result_pam_line_other_control_present.found == 0 or result_pam_line_other_control_present.found
          > 1

      - name: Set Deny For Failed Password Attempts - Ensure authselect changes are applied
        ansible.builtin.command:
          cmd: authselect apply-changes -b
        when:
        - result_authselect_present is defined
        - result_authselect_present.stat.exists
        - |-
          (result_pam_module_add is defined and result_pam_module_add.changed)
           or (result_pam_module_edit is defined and result_pam_module_edit.changed)
      when:
      - '"libpam-runtime" in ansible_facts.packages'
      - result_pam_line_present.found is defined
      - result_pam_line_present.found == 0
      tags:
      - PCI-DSS-Req-8.1.6
      - PCI-DSSv4-8.3
      - PCI-DSSv4-8.3.4
      - accounts_passwords_pam_tally2
      - configure_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Set Deny For Failed Password Attempts - Define a fact for control already
        filtered in case filters are used
      ansible.builtin.set_fact:
        pam_module_control: required
      when: '"libpam-runtime" in ansible_facts.packages'
      tags:
      - PCI-DSS-Req-8.1.6
      - PCI-DSSv4-8.3
      - PCI-DSSv4-8.3.4
      - accounts_passwords_pam_tally2
      - configure_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Set Deny For Failed Password Attempts - Check if the required PAM module option
        is present in /etc/pam.d/common-auth
      ansible.builtin.lineinfile:
        path: /etc/pam.d/common-auth
        regexp: ^\s*auth\s+{{ pam_module_control | regex_escape() }}\s+pam_tally2.so\s*.*\sdeny\b
        state: absent
      check_mode: true
      changed_when: false
      register: result_pam_module_accounts_passwords_pam_tally2_option_present
      when: '"libpam-runtime" in ansible_facts.packages'
      tags:
      - PCI-DSS-Req-8.1.6
      - PCI-DSSv4-8.3
      - PCI-DSSv4-8.3.4
      - accounts_passwords_pam_tally2
      - configure_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Set Deny For Failed Password Attempts - Ensure the "deny" PAM option for "pam_tally2.so"
        is included in /etc/pam.d/common-auth
      ansible.builtin.lineinfile:
        path: /etc/pam.d/common-auth
        backrefs: true
        regexp: ^(\s*auth\s+{{ pam_module_control | regex_escape() }}\s+pam_tally2.so.*)
        line: \1 deny={{ var_password_pam_tally2 }}
        state: present
      register: result_pam_accounts_passwords_pam_tally2_add
      when:
      - '"libpam-runtime" in ansible_facts.packages'
      - result_pam_module_accounts_passwords_pam_tally2_option_present.found == 0
      tags:
      - PCI-DSS-Req-8.1.6
      - PCI-DSSv4-8.3
      - PCI-DSSv4-8.3.4
      - accounts_passwords_pam_tally2
      - configure_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Set Deny For Failed Password Attempts - Ensure the required value for "deny"
        PAM option from "pam_tally2.so" in /etc/pam.d/common-auth
      ansible.builtin.lineinfile:
        path: /etc/pam.d/common-auth
        backrefs: true
        regexp: ^(\s*auth\s+{{ pam_module_control | regex_escape() }}\s+pam_tally2.so\s+.*)(deny)=[0-9a-zA-Z]+\s*(.*)
        line: \1\2={{ var_password_pam_tally2 }} \3
      register: result_pam_accounts_passwords_pam_tally2_edit
      when:
      - '"libpam-runtime" in ansible_facts.packages'
      - result_pam_module_accounts_passwords_pam_tally2_option_present.found > 0
      tags:
      - PCI-DSS-Req-8.1.6
      - PCI-DSSv4-8.3
      - PCI-DSSv4-8.3.4
      - accounts_passwords_pam_tally2
      - configure_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Set Deny For Failed Password Attempts - Define a fact for control already
        filtered in case filters are used
      ansible.builtin.set_fact:
        pam_module_control: required
      when: '"libpam-runtime" in ansible_facts.packages'
      tags:
      - PCI-DSS-Req-8.1.6
      - PCI-DSSv4-8.3
      - PCI-DSSv4-8.3.4
      - accounts_passwords_pam_tally2
      - configure_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Set Deny For Failed Password Attempts - Check if expected PAM module line
        is present in /etc/pam.d/common-auth
      ansible.builtin.lineinfile:
        path: /etc/pam.d/common-auth
        regexp: ^\s*auth\s+{{ pam_module_control | regex_escape() }}\s+pam_tally2.so\s*.*
        state: absent
      check_mode: true
      changed_when: false
      register: result_pam_line_present
      when: '"libpam-runtime" in ansible_facts.packages'
      tags:
      - PCI-DSS-Req-8.1.6
      - PCI-DSSv4-8.3
      - PCI-DSSv4-8.3.4
      - accounts_passwords_pam_tally2
      - configure_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Set Deny For Failed Password Attempts - Include or update the PAM module line
        in /etc/pam.d/common-auth
      block:

      - name: Set Deny For Failed Password Attempts - Check if required PAM module line
          is present in /etc/pam.d/common-auth with different control
        ansible.builtin.lineinfile:
          path: /etc/pam.d/common-auth
          regexp: ^\s*auth\s+.*\s+pam_tally2.so\s*
          state: absent
        check_mode: true
        changed_when: false
        register: result_pam_line_other_control_present

      - name: Set Deny For Failed Password Attempts - Ensure the correct control for the
          required PAM module line in /etc/pam.d/common-auth
        ansible.builtin.replace:
          dest: /etc/pam.d/common-auth
          regexp: ^(\s*auth\s+).*(\bpam_tally2.so.*)
          replace: \1{{ pam_module_control }} \2
        register: result_pam_module_edit
        when:
        - result_pam_line_other_control_present.found == 1

      - name: Set Deny For Failed Password Attempts - Ensure the required PAM module line
          is included in /etc/pam.d/common-auth
        ansible.builtin.lineinfile:
          dest: /etc/pam.d/common-auth
          insertafter: (fail)
          line: auth    {{ pam_module_control }}    pam_tally2.so
        register: result_pam_module_add
        when:
        - result_pam_line_other_control_present.found == 0 or result_pam_line_other_control_present.found
          > 1

      - name: Set Deny For Failed Password Attempts - Ensure authselect changes are applied
        ansible.builtin.command:
          cmd: authselect apply-changes -b
        when:
        - result_authselect_present is defined
        - result_authselect_present.stat.exists
        - |-
          (result_pam_module_add is defined and result_pam_module_add.changed)
           or (result_pam_module_edit is defined and result_pam_module_edit.changed)
      when:
      - '"libpam-runtime" in ansible_facts.packages'
      - result_pam_line_present.found is defined
      - result_pam_line_present.found == 0
      tags:
      - PCI-DSS-Req-8.1.6
      - PCI-DSSv4-8.3
      - PCI-DSSv4-8.3.4
      - accounts_passwords_pam_tally2
      - configure_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Set Deny For Failed Password Attempts - Define a fact for control already
        filtered in case filters are used
      ansible.builtin.set_fact:
        pam_module_control: required
      when: '"libpam-runtime" in ansible_facts.packages'
      tags:
      - PCI-DSS-Req-8.1.6
      - PCI-DSSv4-8.3
      - PCI-DSSv4-8.3.4
      - accounts_passwords_pam_tally2
      - configure_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Set Deny For Failed Password Attempts - Check if the required PAM module option
        is present in /etc/pam.d/common-auth
      ansible.builtin.lineinfile:
        path: /etc/pam.d/common-auth
        regexp: ^\s*auth\s+{{ pam_module_control | regex_escape() }}\s+pam_tally2.so\s*.*\sonerr\b
        state: absent
      check_mode: true
      changed_when: false
      register: result_pam_module_accounts_passwords_pam_tally2_option_present
      when: '"libpam-runtime" in ansible_facts.packages'
      tags:
      - PCI-DSS-Req-8.1.6
      - PCI-DSSv4-8.3
      - PCI-DSSv4-8.3.4
      - accounts_passwords_pam_tally2
      - configure_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Set Deny For Failed Password Attempts - Ensure the "onerr" PAM option for
        "pam_tally2.so" is included in /etc/pam.d/common-auth
      ansible.builtin.lineinfile:
        path: /etc/pam.d/common-auth
        backrefs: true
        regexp: ^(\s*auth\s+{{ pam_module_control | regex_escape() }}\s+pam_tally2.so.*)
        line: \1 onerr=fail
        state: present
      register: result_pam_accounts_passwords_pam_tally2_add
      when:
      - '"libpam-runtime" in ansible_facts.packages'
      - result_pam_module_accounts_passwords_pam_tally2_option_present.found == 0
      tags:
      - PCI-DSS-Req-8.1.6
      - PCI-DSSv4-8.3
      - PCI-DSSv4-8.3.4
      - accounts_passwords_pam_tally2
      - configure_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Set Deny For Failed Password Attempts - Ensure the required value for "onerr"
        PAM option from "pam_tally2.so" in /etc/pam.d/common-auth
      ansible.builtin.lineinfile:
        path: /etc/pam.d/common-auth
        backrefs: true
        regexp: ^(\s*auth\s+{{ pam_module_control | regex_escape() }}\s+pam_tally2.so\s+.*)(onerr)=[0-9a-zA-Z]+\s*(.*)
        line: \1\2=fail \3
      register: result_pam_accounts_passwords_pam_tally2_edit
      when:
      - '"libpam-runtime" in ansible_facts.packages'
      - result_pam_module_accounts_passwords_pam_tally2_option_present.found > 0
      tags:
      - PCI-DSS-Req-8.1.6
      - PCI-DSSv4-8.3
      - PCI-DSSv4-8.3.4
      - accounts_passwords_pam_tally2
      - configure_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Set Deny For Failed Password Attempts - Define a fact for control already
        filtered in case filters are used
      ansible.builtin.set_fact:
        pam_module_control: required
      when: '"libpam-runtime" in ansible_facts.packages'
      tags:
      - PCI-DSS-Req-8.1.6
      - PCI-DSSv4-8.3
      - PCI-DSSv4-8.3.4
      - accounts_passwords_pam_tally2
      - configure_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Set Deny For Failed Password Attempts - Check if expected PAM module line
        is present in /etc/pam.d/common-account
      ansible.builtin.lineinfile:
        path: /etc/pam.d/common-account
        regexp: ^\s*account\s+{{ pam_module_control | regex_escape() }}\s+pam_tally2.so\s*.*
        state: absent
      check_mode: true
      changed_when: false
      register: result_pam_line_present
      when: '"libpam-runtime" in ansible_facts.packages'
      tags:
      - PCI-DSS-Req-8.1.6
      - PCI-DSSv4-8.3
      - PCI-DSSv4-8.3.4
      - accounts_passwords_pam_tally2
      - configure_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Set Deny For Failed Password Attempts - Include or update the PAM module line
        in /etc/pam.d/common-account
      block:

      - name: Set Deny For Failed Password Attempts - Check if required PAM module line
          is present in /etc/pam.d/common-account with different control
        ansible.builtin.lineinfile:
          path: /etc/pam.d/common-account
          regexp: ^\s*account\s+.*\s+pam_tally2.so\s*
          state: absent
        check_mode: true
        changed_when: false
        register: result_pam_line_other_control_present

      - name: Set Deny For Failed Password Attempts - Ensure the correct control for the
          required PAM module line in /etc/pam.d/common-account
        ansible.builtin.replace:
          dest: /etc/pam.d/common-account
          regexp: ^(\s*account\s+).*(\bpam_tally2.so.*)
          replace: \1{{ pam_module_control }} \2
        register: result_pam_module_edit
        when:
        - result_pam_line_other_control_present.found == 1

      - name: Set Deny For Failed Password Attempts - Ensure the required PAM module line
          is included in /etc/pam.d/common-account
        ansible.builtin.lineinfile:
          dest: /etc/pam.d/common-account
          line: account    {{ pam_module_control }}    pam_tally2.so
        register: result_pam_module_add
        when:
        - result_pam_line_other_control_present.found == 0 or result_pam_line_other_control_present.found
          > 1

      - name: Set Deny For Failed Password Attempts - Ensure authselect changes are applied
        ansible.builtin.command:
          cmd: authselect apply-changes -b
        when:
        - result_authselect_present is defined
        - result_authselect_present.stat.exists
        - |-
          (result_pam_module_add is defined and result_pam_module_add.changed)
           or (result_pam_module_edit is defined and result_pam_module_edit.changed)
      when:
      - '"libpam-runtime" in ansible_facts.packages'
      - result_pam_line_present.found is defined
      - result_pam_line_present.found == 0
      tags:
      - PCI-DSS-Req-8.1.6
      - PCI-DSSv4-8.3
      - PCI-DSSv4-8.3.4
      - accounts_passwords_pam_tally2
      - configure_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Set Deny For Failed Password Attempts - Define a fact for control already
        filtered in case filters are used
      ansible.builtin.set_fact:
        pam_module_control: required
      when: '"libpam-runtime" in ansible_facts.packages'
      tags:
      - PCI-DSS-Req-8.1.6
      - PCI-DSSv4-8.3
      - PCI-DSSv4-8.3.4
      - accounts_passwords_pam_tally2
      - configure_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Set Deny For Failed Password Attempts - Check if the required PAM module option
        is present in /etc/pam.d/common-account
      ansible.builtin.lineinfile:
        path: /etc/pam.d/common-account
        regexp: ^\s*account\s+{{ pam_module_control | regex_escape() }}\s+pam_tally2.so\s*.*\s\b
        state: absent
      check_mode: true
      changed_when: false
      register: result_pam_module_accounts_passwords_pam_tally2_option_present
      when: '"libpam-runtime" in ansible_facts.packages'
      tags:
      - PCI-DSS-Req-8.1.6
      - PCI-DSSv4-8.3
      - PCI-DSSv4-8.3.4
      - accounts_passwords_pam_tally2
      - configure_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Set Deny For Failed Password Attempts - Ensure the "" PAM option for "pam_tally2.so"
        is included in /etc/pam.d/common-account
      ansible.builtin.lineinfile:
        path: /etc/pam.d/common-account
        backrefs: true
        regexp: ^(\s*account\s+{{ pam_module_control | regex_escape() }}\s+pam_tally2.so.*)
        line: \1
        state: present
      register: result_pam_accounts_passwords_pam_tally2_add
      when:
      - '"libpam-runtime" in ansible_facts.packages'
      - result_pam_module_accounts_passwords_pam_tally2_option_present.found == 0
      tags:
      - PCI-DSS-Req-8.1.6
      - PCI-DSSv4-8.3
      - PCI-DSSv4-8.3.4
      - accounts_passwords_pam_tally2
      - configure_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

Group Set Password Quality Requirements Group contains 1 group and 7 rules

[ref] The default `pam_pwquality` PAM module provides strength checking for passwords. It performs a number of checks, such as making sure passwords are not similar to dictionary words, are of at least a certain length, are not the previous password reversed, and are not simply a change of case from the previous password. It can also require passwords to be in certain character classes. The `pam_pwquality` module is the preferred way of configuring password requirements.
The man pages `pam_pwquality(8)` provide information on the capabilities and configuration of each.

Group Set Password Quality Requirements with pam_pwquality Group contains 7 rules

[ref] The `pam_pwquality` PAM module can be configured to meet requirements for a variety of policies.
For example, to configure `pam_pwquality` to require at least one uppercase character, lowercase character, digit, and other (special) character, make sure that `pam_pwquality` exists in `/etc/pam.d/system-auth`:

    password    requisite     pam_pwquality.so try_first_pass local_users_only retry=3 authtok_type=

If no such line exists, add one as the first line of the password section in `/etc/pam.d/system-auth`. Next, modify the settings in `/etc/security/pwquality.conf` to match the following:

    difok = 4
    minlen = 14
    dcredit = -1
    ucredit = -1
    lcredit = -1
    ocredit = -1
    maxrepeat = 3

The arguments can be modified to ensure compliance with your organization's security policy. Discussion of each parameter follows.

#### Rule Ensure PAM Enforces Password Requirements - Minimum Digit Characters [ref]

The pam_pwquality module's `dcredit` parameter controls requirements for usage of digits in a password. When set to a negative number, any password will be required to contain that many digits. When set to a positive number, pam_pwquality will grant +1 additional length credit for each digit. Modify the `dcredit` setting in `/etc/security/pwquality.conf` to require the use of a digit in passwords.

Rationale:

Use of a complex password helps to increase the time and resources required to compromise the password. Password complexity, or strength, is a measure of the effectiveness of a password in resisting attempts at guessing and brute-force attacks.
Password complexity is one factor of several that determines how long it takes to crack a password. The more complex the password, the greater the number of possible combinations that need to be tested before the password is compromised. Requiring digits makes password guessing attacks more difficult by ensuring a larger search space.

Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_accounts_password_pam_dcredit

References:

cis-csc | 1, 12, 15, 16, 5
cobit5 | DSS05.04, DSS05.05, DSS05.07, DSS05.10, DSS06.03, DSS06.10
disa | CCI-004066
isa-62443-2009 | 4.3.3.2.2, 4.3.3.5.1, 4.3.3.5.2, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.2, 4.3.3.7.4
isa-62443-2013 | SR 1.1, SR 1.10, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.7, SR 1.8, SR 1.9, SR 2.1
ism | 0421, 0422, 0431, 0974, 1173, 1401, 1504, 1505, 1546, 1557, 1558, 1559, 1560, 1561
iso27001-2013 | A.18.1.4, A.7.1.1, A.9.2.1, A.9.2.2, A.9.2.3, A.9.2.4, A.9.2.6, A.9.3.1, A.9.4.2, A.9.4.3
nist | IA-5(c), IA-5(1)(a), CM-6(a), IA-5(4)
nist-csf | PR.AC-1, PR.AC-6, PR.AC-7
ospp | FMT_SMF_EXT.1
pcidss | Req-8.2.3
os-srg | SRG-OS-000071-GPOS-00039
stigid | UBTU-20-010052
cis | 5.3.1
anssi | R31
pcidss4 | 8.3.6, 8.3
stigref | SV-238223r653844_rule

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | restrict

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}\n' 'libpam-runtime' 2>/dev/null | grep -q '^installed'; then

    var_password_pam_dcredit='-1'

    # Strip any search characters in the key arg so that the key can be replaced without
    # adding any search characters to the config file.
    stripped_key=$(sed 's/[\^=\$,;+]*//g' <<< "^dcredit")

    # shellcheck disable=SC2059
    printf -v formatted_output "%s = %s" "$stripped_key" "$var_password_pam_dcredit"

    # If the key exists, change it. Otherwise, add it to the config_file.
    # We search for the key string followed by a word boundary (matched by \>),
    # so if we search for 'setting', 'setting2' won't match.
    if LC_ALL=C grep -q -m 1 -i -e "^dcredit\\>" "/etc/security/pwquality.conf"; then
        escaped_formatted_output=$(sed -e 's|/|\\/|g' <<< "$formatted_output")
        LC_ALL=C sed -i --follow-symlinks "s/^dcredit\\>.*/$escaped_formatted_output/gi" "/etc/security/pwquality.conf"
    else
        if [[ -s "/etc/security/pwquality.conf" ]] && [[ -n "$(tail -c 1 -- "/etc/security/pwquality.conf" || true)" ]]; then
            LC_ALL=C sed -i --follow-symlinks '$a'\\ "/etc/security/pwquality.conf"
        fi
        printf '%s\n' "$formatted_output" >> "/etc/security/pwquality.conf"
    fi

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | restrict

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - DISA-STIG-UBTU-20-010052
      - NIST-800-53-CM-6(a)
      - NIST-800-53-IA-5(1)(a)
      - NIST-800-53-IA-5(4)
      - NIST-800-53-IA-5(c)
      - PCI-DSS-Req-8.2.3
      - PCI-DSSv4-8.3
      - PCI-DSSv4-8.3.6
      - accounts_password_pam_dcredit
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy
    - name: XCCDF Value var_password_pam_dcredit # promote to variable
      set_fact:
        var_password_pam_dcredit: !!str -1
      tags:
        - always

    - name: Ensure PAM Enforces Password Requirements - Minimum Digit Characters - Check
        if system relies on pam-auth-update tool
      ansible.builtin.stat:
        path: /usr/sbin/pam-auth-update
      register: result_pam_auth_update_present
      when: '"libpam-runtime" in ansible_facts.packages'
      tags:
      - DISA-STIG-UBTU-20-010052
      - NIST-800-53-CM-6(a)
      - NIST-800-53-IA-5(1)(a)
      - NIST-800-53-IA-5(4)
      - NIST-800-53-IA-5(c)
      - PCI-DSS-Req-8.2.3
      - PCI-DSSv4-8.3
      - PCI-DSSv4-8.3.6
      - accounts_password_pam_dcredit
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy

    - name: Ensure PAM Enforces Password Requirements - Minimum Digit Characters - Remediation
        where pam-auth-update tool is present
      block:

      - name: Check if /usr/share/pam-configs/cac_pwquality exists
        stat:
          path: /usr/share/pam-configs/cac_pwquality
        register: pwquality_file_stat

      - name: Put the content into /usr/share/pam-configs/cac_pwquality if it does not
          exist
        copy:
          dest: /usr/share/pam-configs/cac_pwquality
          content: |
            Name: Pwquality password strength checking
            Default: yes
            Priority: 1024
            Conflicts: cracklib
            Password-Type: Primary
            Password:
              requisite           pam_pwquality.so retry=3
          force: true
        when: not pwquality_file_stat.stat.exists

      - name: Ensure PAM Enforces Password Requirements - Minimum Digit Characters - Ensure
          pam-auth-update profile changes are applied
        ansible.builtin.command:
          cmd: pam-auth-update --enable cac_pwquality
      when:
      - '"libpam-runtime" in ansible_facts.packages'
      - result_pam_auth_update_present.stat.exists
      tags:
      - DISA-STIG-UBTU-20-010052
      - NIST-800-53-CM-6(a)
      - NIST-800-53-IA-5(1)(a)
      - NIST-800-53-IA-5(4)
      - NIST-800-53-IA-5(c)
      - PCI-DSS-Req-8.2.3
      - PCI-DSSv4-8.3
      - PCI-DSSv4-8.3.6
      - accounts_password_pam_dcredit
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy

    - name: Ensure PAM Enforces Password Requirements - Minimum Digit Characters - Ensure
        PAM variable dcredit is set accordingly
      ansible.builtin.lineinfile:
        create: true
        dest: /etc/security/pwquality.conf
        regexp: ^#?\s*dcredit
        line: dcredit = {{ var_password_pam_dcredit }}
      when: '"libpam-runtime" in ansible_facts.packages'
      tags:
      - DISA-STIG-UBTU-20-010052
      - NIST-800-53-CM-6(a)
      - NIST-800-53-IA-5(1)(a)
      - NIST-800-53-IA-5(4)
      - NIST-800-53-IA-5(c)
      - PCI-DSS-Req-8.2.3
      - PCI-DSSv4-8.3
      - PCI-DSSv4-8.3.6
      - accounts_password_pam_dcredit
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy

#### Rule Ensure PAM Enforces Password Requirements - Minimum Lowercase Characters [ref]

The pam_pwquality module's `lcredit` parameter controls requirements for usage of lowercase letters in a password. When set to a negative number, any password will be required to contain that many lowercase characters. When set to a positive number, pam_pwquality will grant +1 additional length credit for each lowercase character. Modify the `lcredit` setting in `/etc/security/pwquality.conf` to require the use of a lowercase character in passwords.

Rationale:

Use of a complex password helps to increase the time and resources required to compromise the password. Password complexity, or strength, is a measure of the effectiveness of a password in resisting attempts at guessing and brute-force attacks.
Password complexity is one factor of several that determines how long it takes to crack a password. The more complex the password, the greater the number of possble combinations that need to be tested before the password is compromised. Requiring a minimum number of lowercase characters makes password guessing attacks more difficult by ensuring a larger search space.

Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_accounts_password_pam_lcredit

References:

cis-csc | 1, 12, 15, 16, 5
cobit5 | DSS05.04, DSS05.05, DSS05.07, DSS05.10, DSS06.03, DSS06.10
disa | CCI-004066
isa-62443-2009 | 4.3.3.2.2, 4.3.3.5.1, 4.3.3.5.2, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.2, 4.3.3.7.4
isa-62443-2013 | SR 1.1, SR 1.10, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.7, SR 1.8, SR 1.9, SR 2.1
ism | 0421, 0422, 0431, 0974, 1173, 1401, 1504, 1505, 1546, 1557, 1558, 1559, 1560, 1561
iso27001-2013 | A.18.1.4, A.7.1.1, A.9.2.1, A.9.2.2, A.9.2.3, A.9.2.4, A.9.2.6, A.9.3.1, A.9.4.2, A.9.4.3
nist | IA-5(c), IA-5(1)(a), CM-6(a), IA-5(4)
nist-csf | PR.AC-1, PR.AC-6, PR.AC-7
ospp | FMT_SMF_EXT.1
pcidss | Req-8.2.3
os-srg | SRG-OS-000070-GPOS-00038
stigid | UBTU-20-010051
cis | 5.3.1
anssi | R31
pcidss4 | 8.3.6, 8.3
stigref | SV-238222r653841_rule

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | restrict

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}\n' 'libpam-runtime' 2>/dev/null | grep -q '^installed'; then

    var_password_pam_lcredit='-1'

    # Strip any search characters in the key arg so that the key can be replaced without
    # adding any search characters to the config file.
    stripped_key=$(sed 's/[\^=\$,;+]*//g' <<< "^lcredit")

    # shellcheck disable=SC2059
    printf -v formatted_output "%s = %s" "$stripped_key" "$var_password_pam_lcredit"

    # If the key exists, change it. Otherwise, add it to the config_file.
    # We search for the key string followed by a word boundary (matched by \>),
    # so if we search for 'setting', 'setting2' won't match.
    if LC_ALL=C grep -q -m 1 -i -e "^lcredit\\>" "/etc/security/pwquality.conf"; then
        escaped_formatted_output=$(sed -e 's|/|\\/|g' <<< "$formatted_output")
        LC_ALL=C sed -i --follow-symlinks "s/^lcredit\\>.*/$escaped_formatted_output/gi" "/etc/security/pwquality.conf"
    else
        if [[ -s "/etc/security/pwquality.conf" ]] && [[ -n "$(tail -c 1 -- "/etc/security/pwquality.conf" || true)" ]]; then
            LC_ALL=C sed -i --follow-symlinks '$a'\\ "/etc/security/pwquality.conf"
        fi
        printf '%s\n' "$formatted_output" >> "/etc/security/pwquality.conf"
    fi

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | restrict

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - DISA-STIG-UBTU-20-010051
      - NIST-800-53-CM-6(a)
      - NIST-800-53-IA-5(1)(a)
      - NIST-800-53-IA-5(4)
      - NIST-800-53-IA-5(c)
      - PCI-DSS-Req-8.2.3
      - PCI-DSSv4-8.3
      - PCI-DSSv4-8.3.6
      - accounts_password_pam_lcredit
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy
    - name: XCCDF Value var_password_pam_lcredit # promote to variable
      set_fact:
        var_password_pam_lcredit: !!str -1
      tags:
        - always

    - name: Ensure PAM Enforces Password Requirements - Minimum Lowercase Characters -
        Check if system relies on pam-auth-update tool
      ansible.builtin.stat:
        path: /usr/sbin/pam-auth-update
      register: result_pam_auth_update_present
      when: '"libpam-runtime" in ansible_facts.packages'
      tags:
      - DISA-STIG-UBTU-20-010051
      - NIST-800-53-CM-6(a)
      - NIST-800-53-IA-5(1)(a)
      - NIST-800-53-IA-5(4)
      - NIST-800-53-IA-5(c)
      - PCI-DSS-Req-8.2.3
      - PCI-DSSv4-8.3
      - PCI-DSSv4-8.3.6
      - accounts_password_pam_lcredit
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy

    - name: Ensure PAM Enforces Password Requirements - Minimum Lowercase Characters -
        Remediation where pam-auth-update tool is present
      block:

      - name: Check if /usr/share/pam-configs/cac_pwquality exists
        stat:
          path: /usr/share/pam-configs/cac_pwquality
        register: pwquality_file_stat

      - name: Put the content into /usr/share/pam-configs/cac_pwquality if it does not
          exist
        copy:
          dest: /usr/share/pam-configs/cac_pwquality
          content: |
            Name: Pwquality password strength checking
            Default: yes
            Priority: 1024
            Conflicts: cracklib
            Password-Type: Primary
            Password:
              requisite           pam_pwquality.so retry=3
          force: true
        when: not pwquality_file_stat.stat.exists

      - name: Ensure PAM Enforces Password Requirements - Minimum Lowercase Characters
          - Ensure pam-auth-update profile changes are applied
        ansible.builtin.command:
          cmd: pam-auth-update --enable cac_pwquality
      when:
      - '"libpam-runtime" in ansible_facts.packages'
      - result_pam_auth_update_present.stat.exists
      tags:
      - DISA-STIG-UBTU-20-010051
      - NIST-800-53-CM-6(a)
      - NIST-800-53-IA-5(1)(a)
      - NIST-800-53-IA-5(4)
      - NIST-800-53-IA-5(c)
      - PCI-DSS-Req-8.2.3
      - PCI-DSSv4-8.3
      - PCI-DSSv4-8.3.6
      - accounts_password_pam_lcredit
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy

    - name: Ensure PAM Enforces Password Requirements - Minimum Lowercase Characters -
        Ensure PAM variable lcredit is set accordingly
      ansible.builtin.lineinfile:
        create: true
        dest: /etc/security/pwquality.conf
        regexp: ^#?\s*lcredit
        line: lcredit = {{ var_password_pam_lcredit }}
      when: '"libpam-runtime" in ansible_facts.packages'
      tags:
      - DISA-STIG-UBTU-20-010051
      - NIST-800-53-CM-6(a)
      - NIST-800-53-IA-5(1)(a)
      - NIST-800-53-IA-5(4)
      - NIST-800-53-IA-5(c)
      - PCI-DSS-Req-8.2.3
      - PCI-DSSv4-8.3
      - PCI-DSSv4-8.3.6
      - accounts_password_pam_lcredit
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy

#### Rule Ensure PAM Enforces Password Requirements - Minimum Different Categories [ref]

The pam_pwquality module's `minclass` parameter controls requirements for usage of different character classes, or types, of character that must exist in a password before it is considered valid. For example, setting this value to three (3) requires that any password must have characters from at least three different categories in order to be approved. The default value is zero (0), meaning there are no required classes. There are four categories available:

    * Upper-case characters
    * Lower-case characters
    * Digits
    * Special characters (for example, punctuation)

Modify the `minclass` setting in `/etc/security/pwquality.conf` entry to require 4 differing categories of characters when changing passwords.

Rationale:

Use of a complex password helps to increase the time and resources required to compromise the password. Password complexity, or strength, is a measure of the effectiveness of a password in resisting attempts at guessing and brute-force attacks.
Password complexity is one factor of several that determines how long it takes to crack a password. The more complex the password, the greater the number of possible combinations that need to be tested before the password is compromised.
Requiring a minimum number of character categories makes password guessing attacks more difficult by ensuring a larger search space.

Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_accounts_password_pam_minclass

References:

cis-csc | 1, 12, 15, 16, 5
cobit5 | DSS05.04, DSS05.05, DSS05.07, DSS05.10, DSS06.03, DSS06.10
disa | CCI-004066
isa-62443-2009 | 4.3.3.2.2, 4.3.3.5.1, 4.3.3.5.2, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.2, 4.3.3.7.4
isa-62443-2013 | SR 1.1, SR 1.10, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.7, SR 1.8, SR 1.9, SR 2.1
ism | 0421, 0422, 0431, 0974, 1173, 1401, 1504, 1505, 1546, 1557, 1558, 1559, 1560, 1561
iso27001-2013 | A.18.1.4, A.7.1.1, A.9.2.1, A.9.2.2, A.9.2.3, A.9.2.4, A.9.2.6, A.9.3.1, A.9.4.2, A.9.4.3
nist | IA-5(c), IA-5(1)(a), CM-6(a), IA-5(4)
nist-csf | PR.AC-1, PR.AC-6, PR.AC-7
os-srg | SRG-OS-000072-GPOS-00040
cis | 5.3.1
anssi | R68

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | restrict

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}\n' 'libpam-runtime' 2>/dev/null | grep -q '^installed'; then

    var_password_pam_minclass='4'

    # Strip any search characters in the key arg so that the key can be replaced without
    # adding any search characters to the config file.
    stripped_key=$(sed 's/[\^=\$,;+]*//g' <<< "^minclass")

    # shellcheck disable=SC2059
    printf -v formatted_output "%s = %s" "$stripped_key" "$var_password_pam_minclass"

    # If the key exists, change it. Otherwise, add it to the config_file.
    # We search for the key string followed by a word boundary (matched by \>),
    # so if we search for 'setting', 'setting2' won't match.
    if LC_ALL=C grep -q -m 1 -i -e "^minclass\\>" "/etc/security/pwquality.conf"; then
        escaped_formatted_output=$(sed -e 's|/|\\/|g' <<< "$formatted_output")
        LC_ALL=C sed -i --follow-symlinks "s/^minclass\\>.*/$escaped_formatted_output/gi" "/etc/security/pwquality.conf"
    else
        if [[ -s "/etc/security/pwquality.conf" ]] && [[ -n "$(tail -c 1 -- "/etc/security/pwquality.conf" || true)" ]]; then
            LC_ALL=C sed -i --follow-symlinks '$a'\\ "/etc/security/pwquality.conf"
        fi
        printf '%s\n' "$formatted_output" >> "/etc/security/pwquality.conf"
    fi

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | restrict

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - NIST-800-53-CM-6(a)
      - NIST-800-53-IA-5(1)(a)
      - NIST-800-53-IA-5(4)
      - NIST-800-53-IA-5(c)
      - accounts_password_pam_minclass
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy
    - name: XCCDF Value var_password_pam_minclass # promote to variable
      set_fact:
        var_password_pam_minclass: !!str 4
      tags:
        - always

    - name: Ensure PAM Enforces Password Requirements - Minimum Different Categories -
        Check if system relies on pam-auth-update tool
      ansible.builtin.stat:
        path: /usr/sbin/pam-auth-update
      register: result_pam_auth_update_present
      when: '"libpam-runtime" in ansible_facts.packages'
      tags:
      - NIST-800-53-CM-6(a)
      - NIST-800-53-IA-5(1)(a)
      - NIST-800-53-IA-5(4)
      - NIST-800-53-IA-5(c)
      - accounts_password_pam_minclass
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy

    - name: Ensure PAM Enforces Password Requirements - Minimum Different Categories -
        Remediation where pam-auth-update tool is present
      block:

      - name: Check if /usr/share/pam-configs/cac_pwquality exists
        stat:
          path: /usr/share/pam-configs/cac_pwquality
        register: pwquality_file_stat

      - name: Put the content into /usr/share/pam-configs/cac_pwquality if it does not
          exist
        copy:
          dest: /usr/share/pam-configs/cac_pwquality
          content: |
            Name: Pwquality password strength checking
            Default: yes
            Priority: 1024
            Conflicts: cracklib
            Password-Type: Primary
            Password:
              requisite           pam_pwquality.so retry=3
          force: true
        when: not pwquality_file_stat.stat.exists

      - name: Ensure PAM Enforces Password Requirements - Minimum Different Categories
          - Ensure pam-auth-update profile changes are applied
        ansible.builtin.command:
          cmd: pam-auth-update --enable cac_pwquality
      when:
      - '"libpam-runtime" in ansible_facts.packages'
      - result_pam_auth_update_present.stat.exists
      tags:
      - NIST-800-53-CM-6(a)
      - NIST-800-53-IA-5(1)(a)
      - NIST-800-53-IA-5(4)
      - NIST-800-53-IA-5(c)
      - accounts_password_pam_minclass
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy

    - name: Ensure PAM Enforces Password Requirements - Minimum Different Categories -
        Ensure PAM variable minclass is set accordingly
      ansible.builtin.lineinfile:
        create: true
        dest: /etc/security/pwquality.conf
        regexp: ^#?\s*minclass
        line: minclass = {{ var_password_pam_minclass }}
      when: '"libpam-runtime" in ansible_facts.packages'
      tags:
      - NIST-800-53-CM-6(a)
      - NIST-800-53-IA-5(1)(a)
      - NIST-800-53-IA-5(4)
      - NIST-800-53-IA-5(c)
      - accounts_password_pam_minclass
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy

#### Rule Ensure PAM Enforces Password Requirements - Minimum Length [ref]

The pam_pwquality module's `minlen` parameter controls requirements for minimum characters required in a password. Add `minlen=14` after pam_pwquality to set minimum password length requirements.

Rationale:

The shorter the password, the lower the number of possible combinations that need to be tested before the password is compromised.
Password complexity, or strength, is a measure of the effectiveness of a password in resisting attempts at guessing and brute-force attacks. Password length is one factor of several that helps to determine strength and how long it takes to crack a password. Use of more characters in a password helps to exponentially increase the time and/or resources required to compromise the password.

Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_accounts_password_pam_minlen

References:

cis-csc | 1, 12, 15, 16, 5
cjis | 5.6.2.1.1
cobit5 | DSS05.04, DSS05.05, DSS05.07, DSS05.10, DSS06.03, DSS06.10
disa | CCI-004066
isa-62443-2009 | 4.3.3.2.2, 4.3.3.5.1, 4.3.3.5.2, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.2, 4.3.3.7.4
isa-62443-2013 | SR 1.1, SR 1.10, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.7, SR 1.8, SR 1.9, SR 2.1
ism | 0421, 0422, 0431, 0974, 1173, 1401, 1504, 1505, 1546, 1557, 1558, 1559, 1560, 1561
iso27001-2013 | A.18.1.4, A.7.1.1, A.9.2.1, A.9.2.2, A.9.2.3, A.9.2.4, A.9.2.6, A.9.3.1, A.9.4.2, A.9.4.3
nist | IA-5(c), IA-5(1)(a), CM-6(a), IA-5(4)
nist-csf | PR.AC-1, PR.AC-6, PR.AC-7
ospp | FMT_SMF_EXT.1
pcidss | Req-8.2.3
os-srg | SRG-OS-000078-GPOS-00046
stigid | UBTU-20-010054
cis | 5.3.1
anssi | R31, R68
pcidss4 | 8.3.6, 8.3
stigref | SV-238225r832942_rule

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | restrict

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}\n' 'libpam-runtime' 2>/dev/null | grep -q '^installed'; then

    var_password_pam_minlen='14'

    # Strip any search characters in the key arg so that the key can be replaced without
    # adding any search characters to the config file.
    stripped_key=$(sed 's/[\^=\$,;+]*//g' <<< "^minlen")

    # shellcheck disable=SC2059
    printf -v formatted_output "%s = %s" "$stripped_key" "$var_password_pam_minlen"

    # If the key exists, change it. Otherwise, add it to the config_file.
    # We search for the key string followed by a word boundary (matched by \>),
    # so if we search for 'setting', 'setting2' won't match.
    if LC_ALL=C grep -q -m 1 -i -e "^minlen\\>" "/etc/security/pwquality.conf"; then
        escaped_formatted_output=$(sed -e 's|/|\\/|g' <<< "$formatted_output")
        LC_ALL=C sed -i --follow-symlinks "s/^minlen\\>.*/$escaped_formatted_output/gi" "/etc/security/pwquality.conf"
    else
        if [[ -s "/etc/security/pwquality.conf" ]] && [[ -n "$(tail -c 1 -- "/etc/security/pwquality.conf" || true)" ]]; then
            LC_ALL=C sed -i --follow-symlinks '$a'\\ "/etc/security/pwquality.conf"
        fi
        printf '%s\n' "$formatted_output" >> "/etc/security/pwquality.conf"
    fi

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | restrict

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - CJIS-5.6.2.1.1
      - DISA-STIG-UBTU-20-010054
      - NIST-800-53-CM-6(a)
      - NIST-800-53-IA-5(1)(a)
      - NIST-800-53-IA-5(4)
      - NIST-800-53-IA-5(c)
      - PCI-DSS-Req-8.2.3
      - PCI-DSSv4-8.3
      - PCI-DSSv4-8.3.6
      - accounts_password_pam_minlen
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy
    - name: XCCDF Value var_password_pam_minlen # promote to variable
      set_fact:
        var_password_pam_minlen: !!str 14
      tags:
        - always

    - name: Ensure PAM Enforces Password Requirements - Minimum Length - Check if system
        relies on pam-auth-update tool
      ansible.builtin.stat:
        path: /usr/sbin/pam-auth-update
      register: result_pam_auth_update_present
      when: '"libpam-runtime" in ansible_facts.packages'
      tags:
      - CJIS-5.6.2.1.1
      - DISA-STIG-UBTU-20-010054
      - NIST-800-53-CM-6(a)
      - NIST-800-53-IA-5(1)(a)
      - NIST-800-53-IA-5(4)
      - NIST-800-53-IA-5(c)
      - PCI-DSS-Req-8.2.3
      - PCI-DSSv4-8.3
      - PCI-DSSv4-8.3.6
      - accounts_password_pam_minlen
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy

    - name: Ensure PAM Enforces Password Requirements - Minimum Length - Remediation where
        pam-auth-update tool is present
      block:

      - name: Check if /usr/share/pam-configs/cac_pwquality exists
        stat:
          path: /usr/share/pam-configs/cac_pwquality
        register: pwquality_file_stat

      - name: Put the content into /usr/share/pam-configs/cac_pwquality if it does not
          exist
        copy:
          dest: /usr/share/pam-configs/cac_pwquality
          content: |
            Name: Pwquality password strength checking
            Default: yes
            Priority: 1024
            Conflicts: cracklib
            Password-Type: Primary
            Password:
              requisite           pam_pwquality.so retry=3
          force: true
        when: not pwquality_file_stat.stat.exists

      - name: Ensure PAM Enforces Password Requirements - Minimum Length - Ensure pam-auth-update
          profile changes are applied
        ansible.builtin.command:
          cmd: pam-auth-update --enable cac_pwquality
      when:
      - '"libpam-runtime" in ansible_facts.packages'
      - result_pam_auth_update_present.stat.exists
      tags:
      - CJIS-5.6.2.1.1
      - DISA-STIG-UBTU-20-010054
      - NIST-800-53-CM-6(a)
      - NIST-800-53-IA-5(1)(a)
      - NIST-800-53-IA-5(4)
      - NIST-800-53-IA-5(c)
      - PCI-DSS-Req-8.2.3
      - PCI-DSSv4-8.3
      - PCI-DSSv4-8.3.6
      - accounts_password_pam_minlen
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy

    - name: Ensure PAM Enforces Password Requirements - Minimum Length - Ensure PAM variable
        minlen is set accordingly
      ansible.builtin.lineinfile:
        create: true
        dest: /etc/security/pwquality.conf
        regexp: ^#?\s*minlen
        line: minlen = {{ var_password_pam_minlen }}
      when: '"libpam-runtime" in ansible_facts.packages'
      tags:
      - CJIS-5.6.2.1.1
      - DISA-STIG-UBTU-20-010054
      - NIST-800-53-CM-6(a)
      - NIST-800-53-IA-5(1)(a)
      - NIST-800-53-IA-5(4)
      - NIST-800-53-IA-5(c)
      - PCI-DSS-Req-8.2.3
      - PCI-DSSv4-8.3
      - PCI-DSSv4-8.3.6
      - accounts_password_pam_minlen
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy

#### Rule Ensure PAM Enforces Password Requirements - Minimum Special Characters [ref]

The pam_pwquality module's `ocredit=` parameter controls requirements for usage of special (or "other") characters in a password. When set to a negative number, any password will be required to contain that many special characters. When set to a positive number, pam_pwquality will grant +1 additional length credit for each special character. Modify the `ocredit` setting in `/etc/security/pwquality.conf` to equal -1 to require use of a special character in passwords.

Rationale:

Use of a complex password helps to increase the time and resources required to compromise the password. Password complexity, or strength, is a measure of the effectiveness of a password in resisting attempts at guessing and brute-force attacks.
Password complexity is one factor of several that determines how long it takes to crack a password. The more complex the password, the greater the number of possible combinations that need to be tested before the password is compromised. Requiring a minimum number of special characters makes password guessing attacks more difficult by ensuring a larger search space.

Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_accounts_password_pam_ocredit

References:

cis-csc | 1, 12, 15, 16, 5
cobit5 | DSS05.04, DSS05.05, DSS05.07, DSS05.10, DSS06.03, DSS06.10
disa | CCI-004066
isa-62443-2009 | 4.3.3.2.2, 4.3.3.5.1, 4.3.3.5.2, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.2, 4.3.3.7.4
isa-62443-2013 | SR 1.1, SR 1.10, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.7, SR 1.8, SR 1.9, SR 2.1
ism | 0421, 0422, 0431, 0974, 1173, 1401, 1504, 1505, 1546, 1557, 1558, 1559, 1560, 1561
iso27001-2013 | A.18.1.4, A.7.1.1, A.9.2.1, A.9.2.2, A.9.2.3, A.9.2.4, A.9.2.6, A.9.3.1, A.9.4.2, A.9.4.3
nist | IA-5(c), IA-5(1)(a), CM-6(a), IA-5(4)
nist-csf | PR.AC-1, PR.AC-6, PR.AC-7
ospp | FMT_SMF_EXT.1
os-srg | SRG-OS-000266-GPOS-00101
stigid | UBTU-20-010055
cis | 5.3.1
anssi | R31
stigref | SV-238226r653853_rule

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | restrict

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}\n' 'libpam-runtime' 2>/dev/null | grep -q '^installed'; then

    var_password_pam_ocredit='-1'

    # Strip any search characters in the key arg so that the key can be replaced without
    # adding any search characters to the config file.
    stripped_key=$(sed 's/[\^=\$,;+]*//g' <<< "^ocredit")

    # shellcheck disable=SC2059
    printf -v formatted_output "%s = %s" "$stripped_key" "$var_password_pam_ocredit"

    # If the key exists, change it. Otherwise, add it to the config_file.
    # We search for the key string followed by a word boundary (matched by \>),
    # so if we search for 'setting', 'setting2' won't match.
    if LC_ALL=C grep -q -m 1 -i -e "^ocredit\\>" "/etc/security/pwquality.conf"; then
        escaped_formatted_output=$(sed -e 's|/|\\/|g' <<< "$formatted_output")
        LC_ALL=C sed -i --follow-symlinks "s/^ocredit\\>.*/$escaped_formatted_output/gi" "/etc/security/pwquality.conf"
    else
        if [[ -s "/etc/security/pwquality.conf" ]] && [[ -n "$(tail -c 1 -- "/etc/security/pwquality.conf" || true)" ]]; then
            LC_ALL=C sed -i --follow-symlinks '$a'\\ "/etc/security/pwquality.conf"
        fi
        printf '%s\n' "$formatted_output" >> "/etc/security/pwquality.conf"
    fi

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | restrict

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - DISA-STIG-UBTU-20-010055
      - NIST-800-53-CM-6(a)
      - NIST-800-53-IA-5(1)(a)
      - NIST-800-53-IA-5(4)
      - NIST-800-53-IA-5(c)
      - accounts_password_pam_ocredit
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy
    - name: XCCDF Value var_password_pam_ocredit # promote to variable
      set_fact:
        var_password_pam_ocredit: !!str -1
      tags:
        - always

    - name: Ensure PAM Enforces Password Requirements - Minimum Special Characters - Check
        if system relies on pam-auth-update tool
      ansible.builtin.stat:
        path: /usr/sbin/pam-auth-update
      register: result_pam_auth_update_present
      when: '"libpam-runtime" in ansible_facts.packages'
      tags:
      - DISA-STIG-UBTU-20-010055
      - NIST-800-53-CM-6(a)
      - NIST-800-53-IA-5(1)(a)
      - NIST-800-53-IA-5(4)
      - NIST-800-53-IA-5(c)
      - accounts_password_pam_ocredit
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy

    - name: Ensure PAM Enforces Password Requirements - Minimum Special Characters - Remediation
        where pam-auth-update tool is present
      block:

      - name: Check if /usr/share/pam-configs/cac_pwquality exists
        stat:
          path: /usr/share/pam-configs/cac_pwquality
        register: pwquality_file_stat

      - name: Put the content into /usr/share/pam-configs/cac_pwquality if it does not
          exist
        copy:
          dest: /usr/share/pam-configs/cac_pwquality
          content: |
            Name: Pwquality password strength checking
            Default: yes
            Priority: 1024
            Conflicts: cracklib
            Password-Type: Primary
            Password:
              requisite           pam_pwquality.so retry=3
          force: true
        when: not pwquality_file_stat.stat.exists

      - name: Ensure PAM Enforces Password Requirements - Minimum Special Characters -
          Ensure pam-auth-update profile changes are applied
        ansible.builtin.command:
          cmd: pam-auth-update --enable cac_pwquality
      when:
      - '"libpam-runtime" in ansible_facts.packages'
      - result_pam_auth_update_present.stat.exists
      tags:
      - DISA-STIG-UBTU-20-010055
      - NIST-800-53-CM-6(a)
      - NIST-800-53-IA-5(1)(a)
      - NIST-800-53-IA-5(4)
      - NIST-800-53-IA-5(c)
      - accounts_password_pam_ocredit
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy

    - name: Ensure PAM Enforces Password Requirements - Minimum Special Characters - Ensure
        PAM variable ocredit is set accordingly
      ansible.builtin.lineinfile:
        create: true
        dest: /etc/security/pwquality.conf
        regexp: ^#?\s*ocredit
        line: ocredit = {{ var_password_pam_ocredit }}
      when: '"libpam-runtime" in ansible_facts.packages'
      tags:
      - DISA-STIG-UBTU-20-010055
      - NIST-800-53-CM-6(a)
      - NIST-800-53-IA-5(1)(a)
      - NIST-800-53-IA-5(4)
      - NIST-800-53-IA-5(c)
      - accounts_password_pam_ocredit
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy

#### Rule Ensure PAM Enforces Password Requirements - Authentication Retry Prompts Permitted Per-Session [ref]

To configure the number of retry prompts that are permitted per-session: Edit the `pam_pwquality.so` statement in `/etc/pam.d/common-password` to show `retry=3` , or a lower value if site policy is more restrictive. The DoD requirement is a maximum of 3 prompts per session.
Rationale: | Setting the password retry prompts that are permitted on a per-session basis to a low value requires some software, such as SSH, to re-connect. This can slow down and draw additional attention to some types of password-guessing attacks. Note that this is different from account lockout, which is provided by the pam_faillock module.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_accounts_password_pam_retry

References:

cis-csc | 1, 11, 12, 15, 16, 3, 5, 9
cjis | 5.5.3
cobit5 | BAI10.01, BAI10.02, BAI10.03, BAI10.05, DSS05.04, DSS05.05, DSS05.07, DSS05.10, DSS06.03, DSS06.10
disa | CCI-004066
isa-62443-2009 | 4.3.3.2.2, 4.3.3.5.1, 4.3.3.5.2, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.2, 4.3.3.7.4, 4.3.4.3.2, 4.3.4.3.3
isa-62443-2013 | SR 1.1, SR 1.10, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 7.6
iso27001-2013 | A.12.1.2, A.12.5.1, A.12.6.2, A.14.2.2, A.14.2.3, A.14.2.4, A.18.1.4, A.7.1.1, A.9.2.1, A.9.2.2, A.9.2.3, A.9.2.4, A.9.2.6, A.9.3.1, A.9.4.2, A.9.4.3
nist | CM-6(a), AC-7(a), IA-5(4)
nist-csf | PR.AC-1, PR.AC-6, PR.AC-7, PR.IP-1
os-srg | SRG-OS-000069-GPOS-00037, SRG-OS-000480-GPOS-00227
stigid | UBTU-20-010057
cis | 5.3.1
anssi | R68
stigref | SV-238228r653859_rule

Remediation Shell script ⇲

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}\n' 'libpam-runtime' 2>/dev/null | grep -q '^installed'; then

    var_password_pam_retry='3'

    conf_name=cac_pwquality
    if [ ! -f /usr/share/pam-configs/"$conf_name" ]; then
        cat << EOF > /usr/share/pam-configs/"$conf_name"
    Name: Pwquality password strength checking
    Default: yes
    Priority: 1025
    Conflicts: cracklib, pwquality
    Password-Type: Primary
    Password:
        requisite                   pam_pwquality.so
    EOF
    fi

    DEBIAN_FRONTEND=noninteractive pam-auth-update
    PWQUALITY_CONF="/etc/security/pwquality.conf"
        regex="^\s*retry\s*="
        line="retry = $var_password_pam_retry"
        if ! grep -q $regex $PWQUALITY_CONF; then
            echo $line >> $PWQUALITY_CONF
        else
            sed -i --follow-symlinks 's|^\s*\(retry\s*=\s*\)\(\S\+\)|\1'"$var_password_pam_retry"'|g' $PWQUALITY_CONF
        fi

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

#### Rule Ensure PAM Enforces Password Requirements - Minimum Uppercase Characters [ref]

The pam_pwquality module's `ucredit=` parameter controls requirements for usage of uppercase letters in a password. When set to a negative number, any password will be required to contain that many uppercase characters. When set to a positive number, pam_pwquality will grant +1 additional length credit for each uppercase character. Modify the `ucredit` setting in `/etc/security/pwquality.conf` to require the use of an uppercase character in passwords.

Rationale:

Use of a complex password helps to increase the time and resources required to compromise the password. Password complexity, or strength, is a measure of the effectiveness of a password in resisting attempts at guessing and brute-force attacks.
Password complexity is one factor of several that determines how long it takes to crack a password. The more complex the password, the greater the number of possible combinations that need to be tested before the password is compromised.

Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_accounts_password_pam_ucredit

References:

cis-csc | 1, 12, 15, 16, 5
cobit5 | DSS05.04, DSS05.05, DSS05.07, DSS05.10, DSS06.03, DSS06.10
disa | CCI-004066
isa-62443-2009 | 4.3.3.2.2, 4.3.3.5.1, 4.3.3.5.2, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.2, 4.3.3.7.4
isa-62443-2013 | SR 1.1, SR 1.10, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.7, SR 1.8, SR 1.9, SR 2.1
ism | 0421, 0422, 0431, 0974, 1173, 1401, 1504, 1505, 1546, 1557, 1558, 1559, 1560, 1561
iso27001-2013 | A.18.1.4, A.7.1.1, A.9.2.1, A.9.2.2, A.9.2.3, A.9.2.4, A.9.2.6, A.9.3.1, A.9.4.2, A.9.4.3
nist | IA-5(c), IA-5(1)(a), CM-6(a), IA-5(4)
nist-csf | PR.AC-1, PR.AC-6, PR.AC-7
ospp | FMT_SMF_EXT.1
pcidss | Req-8.2.3
os-srg | SRG-OS-000069-GPOS-00037, SRG-OS-000070-GPOS-00038
stigid | UBTU-20-010050
cis | 5.3.1
anssi | R31
stigref | SV-238221r653838_rule

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | restrict

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}\n' 'libpam-runtime' 2>/dev/null | grep -q '^installed'; then

    var_password_pam_ucredit='-1'

    # Strip any search characters in the key arg so that the key can be replaced without
    # adding any search characters to the config file.
    stripped_key=$(sed 's/[\^=\$,;+]*//g' <<< "^ucredit")

    # shellcheck disable=SC2059
    printf -v formatted_output "%s = %s" "$stripped_key" "$var_password_pam_ucredit"

    # If the key exists, change it. Otherwise, add it to the config_file.
    # We search for the key string followed by a word boundary (matched by \>),
    # so if we search for 'setting', 'setting2' won't match.
    if LC_ALL=C grep -q -m 1 -i -e "^ucredit\\>" "/etc/security/pwquality.conf"; then
        escaped_formatted_output=$(sed -e 's|/|\\/|g' <<< "$formatted_output")
        LC_ALL=C sed -i --follow-symlinks "s/^ucredit\\>.*/$escaped_formatted_output/gi" "/etc/security/pwquality.conf"
    else
        if [[ -s "/etc/security/pwquality.conf" ]] && [[ -n "$(tail -c 1 -- "/etc/security/pwquality.conf" || true)" ]]; then
            LC_ALL=C sed -i --follow-symlinks '$a'\\ "/etc/security/pwquality.conf"
        fi
        printf '%s\n' "$formatted_output" >> "/etc/security/pwquality.conf"
    fi

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | restrict

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - DISA-STIG-UBTU-20-010050
      - NIST-800-53-CM-6(a)
      - NIST-800-53-IA-5(1)(a)
      - NIST-800-53-IA-5(4)
      - NIST-800-53-IA-5(c)
      - PCI-DSS-Req-8.2.3
      - accounts_password_pam_ucredit
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy
    - name: XCCDF Value var_password_pam_ucredit # promote to variable
      set_fact:
        var_password_pam_ucredit: !!str -1
      tags:
        - always

    - name: Ensure PAM Enforces Password Requirements - Minimum Uppercase Characters -
        Check if system relies on pam-auth-update tool
      ansible.builtin.stat:
        path: /usr/sbin/pam-auth-update
      register: result_pam_auth_update_present
      when: '"libpam-runtime" in ansible_facts.packages'
      tags:
      - DISA-STIG-UBTU-20-010050
      - NIST-800-53-CM-6(a)
      - NIST-800-53-IA-5(1)(a)
      - NIST-800-53-IA-5(4)
      - NIST-800-53-IA-5(c)
      - PCI-DSS-Req-8.2.3
      - accounts_password_pam_ucredit
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy

    - name: Ensure PAM Enforces Password Requirements - Minimum Uppercase Characters -
        Remediation where pam-auth-update tool is present
      block:

      - name: Check if /usr/share/pam-configs/cac_pwquality exists
        stat:
          path: /usr/share/pam-configs/cac_pwquality
        register: pwquality_file_stat

      - name: Put the content into /usr/share/pam-configs/cac_pwquality if it does not
          exist
        copy:
          dest: /usr/share/pam-configs/cac_pwquality
          content: |
            Name: Pwquality password strength checking
            Default: yes
            Priority: 1024
            Conflicts: cracklib
            Password-Type: Primary
            Password:
              requisite           pam_pwquality.so retry=3
          force: true
        when: not pwquality_file_stat.stat.exists

      - name: Ensure PAM Enforces Password Requirements - Minimum Uppercase Characters
          - Ensure pam-auth-update profile changes are applied
        ansible.builtin.command:
          cmd: pam-auth-update --enable cac_pwquality
      when:
      - '"libpam-runtime" in ansible_facts.packages'
      - result_pam_auth_update_present.stat.exists
      tags:
      - DISA-STIG-UBTU-20-010050
      - NIST-800-53-CM-6(a)
      - NIST-800-53-IA-5(1)(a)
      - NIST-800-53-IA-5(4)
      - NIST-800-53-IA-5(c)
      - PCI-DSS-Req-8.2.3
      - accounts_password_pam_ucredit
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy

    - name: Ensure PAM Enforces Password Requirements - Minimum Uppercase Characters -
        Ensure PAM variable ucredit is set accordingly
      ansible.builtin.lineinfile:
        create: true
        dest: /etc/security/pwquality.conf
        regexp: ^#?\s*ucredit
        line: ucredit = {{ var_password_pam_ucredit }}
      when: '"libpam-runtime" in ansible_facts.packages'
      tags:
      - DISA-STIG-UBTU-20-010050
      - NIST-800-53-CM-6(a)
      - NIST-800-53-IA-5(1)(a)
      - NIST-800-53-IA-5(4)
      - NIST-800-53-IA-5(c)
      - PCI-DSS-Req-8.2.3
      - accounts_password_pam_ucredit
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy

#### Rule Install pam_pwquality Package [ref]

The `libpam-pwquality` package can be installed with the following command:

    $ apt-get install libpam-pwquality

Rationale: | Use of a complex password helps to increase the time and resources required to compromise the password. Password complexity, or strength, is a measure of the effectiveness of a password in resisting attempts at guessing and brute-force attacks. "pwquality" enforces complex password construction configuration and has the ability to limit brute-force attacks on the system.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_package_pam_pwquality_installed

References:

disa | CCI-000366
os-srg | SRG-OS-000480-GPOS-00225
stigid | UBTU-20-010057
cis | 5.3.1
stigref | SV-238228r653859_rule

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | enable

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}\n' 'libpam-runtime' 2>/dev/null | grep -q '^installed'; then

    DEBIAN_FRONTEND=noninteractive apt-get install -y "libpam-pwquality"

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation OSBuild Blueprint snippet ⇲

    [[packages]]
    name = "libpam-pwquality"
    version = "*"

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | enable

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - DISA-STIG-UBTU-20-010057
      - enable_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - package_pam_pwquality_installed

    - name: Ensure libpam-pwquality is installed
      package:
        name: libpam-pwquality
        state: present
      when: '"libpam-runtime" in ansible_facts.packages'
      tags:
      - DISA-STIG-UBTU-20-010057
      - enable_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - package_pam_pwquality_installed

Remediation Puppet snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | enable

    include install_libpam-pwquality

    class install_libpam-pwquality {
      package { 'libpam-pwquality':
        ensure => 'installed',
      }
    }

Group Protect Accounts by Restricting Password-Based Login Group contains 4 groups and 23 rules

[ref] Conventionally, Unix shell accounts are accessed by providing a username and password to a login program, which tests these values for correctness using the `/etc/passwd` and `/etc/shadow` files. Password-based login is vulnerable to guessing of weak passwords, and to sniffing and man-in-the-middle attacks against passwords entered over a network or at an insecure console. Therefore, mechanisms for accessing accounts by entering usernames and passwords should be restricted to those which are operationally necessary.

Group Set Account Expiration Parameters Group contains 3 rules

[ref] Accounts can be configured to be automatically disabled after a certain time period, meaning that they will require administrator interaction to become usable again. Expiration of accounts after inactivity can be set for all accounts by default and also on a per-account basis, such as for accounts that are known to be temporary. To configure automatic expiration of an account following the expiration of its password (that is, after the password has expired and not been changed), run the following command, substituting `NUM_DAYS` and `USER` appropriately:

    $ sudo chage -I NUM_DAYS USER

Accounts, such as temporary accounts, can also be configured to expire on an explicitly-set date with the `-E` option. The file `/etc/default/useradd` controls default settings for all newly-created accounts created with the system's normal command line utilities.
Warning: This will only apply to newly created accounts

#### Rule Set Account Expiration Following Inactivity [ref]

To specify the number of days after a password expires (which signifies inactivity) until an account is permanently disabled, add or correct the following line in `/etc/default/useradd`:

    INACTIVE=30

If a password is currently on the verge of expiration, then `30` day(s) remain(s) until the account is automatically disabled. However, if the password will not expire for another 60 days, then 60 days plus `30` day(s) could elapse until the account would be automatically disabled. See the `useradd` man page for more information.

Rationale:

Inactive identifiers pose a risk to systems and applications because attackers may exploit an inactive identifier and potentially obtain undetected access to the system. Disabling inactive accounts ensures that accounts which may not have been responsibly removed are not available to attackers who may have compromised their credentials. Owners of inactive accounts will not notice if unauthorized access to their user account has been obtained.

Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_account_disable_post_pw_expiration

References:

cis-csc | 1, 12, 13, 14, 15, 16, 18, 3, 5, 7, 8
cjis | 5.6.2.1.1
cobit5 | DSS01.03, DSS03.05, DSS05.04, DSS05.05, DSS05.07, DSS05.10, DSS06.03, DSS06.10
cui | 3.5.6
disa | CCI-003628, CCI-003627
isa-62443-2009 | 4.3.3.2.2, 4.3.3.5.1, 4.3.3.5.2, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.2, 4.3.3.7.3, 4.3.3.7.4
isa-62443-2013 | SR 1.1, SR 1.10, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 6.2
iso27001-2013 | A.12.4.1, A.12.4.3, A.18.1.4, A.6.1.2, A.7.1.1, A.9.1.2, A.9.2.1, A.9.2.2, A.9.2.3, A.9.2.4, A.9.2.6, A.9.3.1, A.9.4.1, A.9.4.2, A.9.4.3, A.9.4.4, A.9.4.5
nerc-cip | CIP-004-6 R2.2.2, CIP-004-6 R2.2.3, CIP-007-3 R.1.3, CIP-007-3 R5, CIP-007-3 R5.1.1, CIP-007-3 R5.1.3, CIP-007-3 R5.2.1, CIP-007-3 R5.2.3
nist | IA-4(e), AC-2(3), CM-6(a)
nist-csf | DE.CM-1, DE.CM-3, PR.AC-1, PR.AC-4, PR.AC-6, PR.AC-7
pcidss | Req-8.1.4
os-srg | SRG-OS-000118-GPOS-00060
stigid | UBTU-20-010409
cis | 5.4.1.4
pcidss4 | 8.2.6, 8.2
stigref | SV-238330r928525_rule

Remediation Shell script ⇲

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}\n' 'login' 2>/dev/null | grep -q '^installed'; then

    var_account_disable_post_pw_expiration='30'

    # Strip any search characters in the key arg so that the key can be replaced without
    # adding any search characters to the config file.
    stripped_key=$(sed 's/[\^=\$,;+]*//g' <<< "^INACTIVE")

    # shellcheck disable=SC2059
    printf -v formatted_output "%s=%s" "$stripped_key" "$var_account_disable_post_pw_expiration"

    # If the key exists, change it. Otherwise, add it to the config_file.
    # We search for the key string followed by a word boundary (matched by \>),
    # so if we search for 'setting', 'setting2' won't match.
    if LC_ALL=C grep -q -m 1 -i -e "^INACTIVE\\>" "/etc/default/useradd"; then
        escaped_formatted_output=$(sed -e 's|/|\\/|g' <<< "$formatted_output")
        LC_ALL=C sed -i --follow-symlinks "s/^INACTIVE\\>.*/$escaped_formatted_output/gi" "/etc/default/useradd"
    else
        if [[ -s "/etc/default/useradd" ]] && [[ -n "$(tail -c 1 -- "/etc/default/useradd" || true)" ]]; then
            LC_ALL=C sed -i --follow-symlinks '$a'\\ "/etc/default/useradd"
        fi
        printf '%s\n' "$formatted_output" >> "/etc/default/useradd"
    fi

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

#### Rule Ensure All Accounts on the System Have Unique Names [ref]

Ensure accounts on the system have unique names. To ensure all accounts have unique names, run the following command:

    $ sudo getent passwd | awk -F: '{ print $1}' | uniq -d

If a username is returned, change or delete the username.

Rationale: | Unique usernames allow for accountability on the system.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_account_unique_name

References:

cjis | 5.5.2
disa | CCI-000770, CCI-000804
pcidss | Req-8.1.1
cis | 6.2.15
pcidss4 | 8.2.1, 8.2

#### Rule Ensure shadow Group is Empty [ref]

The shadow group allows system programs which require access the ability to read the /etc/shadow file. No users should be assigned to the shadow group. Warning: This rule remediation will ensure the group membership is empty in /etc/group. To avoid any disruption the remediation won't change the primary group of users in /etc/passwd if any user has the shadow GID as primary group.

Rationale:

Any users assigned to the shadow group would be granted read access to the /etc/shadow file. If attackers can gain read access to the /etc/shadow file, they can easily run a password cracking program against the hashed passwords to break them. Other security information that is stored in the /etc/shadow file (such as expiration) could also be useful to subvert additional user accounts.

Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_ensure_shadow_group_empty

References:

pcidss | Req-8.2.1
cis | 6.2.17
pcidss4 | 8.3.2, 8.3

Remediation Shell script ⇲

    sed -ri 's/(^shadow:[^:]*:[^:]*:)([^:]+$)/\1/' /etc/group

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | medium
Reboot: | false
Strategy: | restrict

    - name: Ensure interactive local users are the owners of their respective initialization
        files
      ansible.builtin.lineinfile:
        dest: /etc/group
        backrefs: true
        regexp: (^shadow:[^:]*:[^:]*:)([^:]+$)
        line: \1
      tags:
      - PCI-DSS-Req-8.2.1
      - PCI-DSSv4-8.3
      - PCI-DSSv4-8.3.2
      - ensure_shadow_group_empty
      - low_complexity
      - medium_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy

Group Set Password Expiration Parameters Group contains 5 rules

[ref] The file `/etc/login.defs` controls several password-related settings. Programs such as `passwd`, `su`, and `login` consult `/etc/login.defs` to determine behavior with regard to password aging, expiration warnings, and length. See the man page `login.defs(5)` for more information.
Users should be forced to change their passwords, in order to decrease the utility of compromised passwords. However, the need to change passwords often should be balanced against the risk that users will reuse or write down passwords if forced to change them too often. Forcing password changes every 90-360 days, depending on the environment, is recommended. Set the appropriate value as `PASS_MAX_DAYS` and apply it to existing accounts with the `-M` flag.
The `PASS_MIN_DAYS` (`-m`) setting prevents password changes for 7 days after the first change, to discourage password cycling. If you use this setting, train users to contact an administrator for an emergency password change in case a new password becomes compromised. The `PASS_WARN_AGE` (`-W`) setting gives users 7 days of warnings at login time that their passwords are about to expire.
For example, for each existing human user USER, expiration parameters could be adjusted to a 180 day maximum password age, 7 day minimum password age, and 7 day warning period with the following command:

    $ sudo chage -M 180 -m 7 -W 7 USER

#### Rule Set Password Maximum Age [ref]

To specify password maximum age for new accounts, edit the file `/etc/login.defs` and add or correct the following line:

    PASS_MAX_DAYS 365

A value of 180 days is sufficient for many environments. The DoD requirement is 60. The profile requirement is `365`.

Rationale:

Any password, no matter how complex, can eventually be cracked. Therefore, passwords need to be changed periodically. If the operating system does not limit the lifetime of passwords and force users to change their passwords, there is the risk that the operating system passwords could be compromised.
Setting the password maximum age ensures users are required to periodically change their passwords. Requiring shorter password lifetimes increases the risk of users writing down the password in a convenient location subject to physical compromise.

Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_accounts_maximum_age_login_defs

References:

cis-csc | 1, 12, 15, 16, 5
cjis | 5.6.2.1
cobit5 | DSS05.04, DSS05.05, DSS05.07, DSS05.10, DSS06.03, DSS06.10
cui | 3.5.6
disa | CCI-004066
isa-62443-2009 | 4.3.3.2.2, 4.3.3.5.1, 4.3.3.5.2, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.2, 4.3.3.7.4
isa-62443-2013 | SR 1.1, SR 1.10, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.7, SR 1.8, SR 1.9, SR 2.1
ism | 0418, 1055, 1402
iso27001-2013 | A.18.1.4, A.7.1.1, A.9.2.1, A.9.2.2, A.9.2.3, A.9.2.4, A.9.2.6, A.9.3.1, A.9.4.2, A.9.4.3
nist | IA-5(f), IA-5(1)(d), CM-6(a)
nist-csf | PR.AC-1, PR.AC-6, PR.AC-7
pcidss | Req-8.2.4
os-srg | SRG-OS-000076-GPOS-00044
stigid | UBTU-20-010008
cis | 5.4.1.1
pcidss4 | 8.3.9, 8.3
stigref | SV-238203r653784_rule

Remediation Shell script ⇲

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}\n' 'login' 2>/dev/null | grep -q '^installed'; then

    var_accounts_maximum_age_login_defs='365'

    # Strip any search characters in the key arg so that the key can be replaced without
    # adding any search characters to the config file.
    stripped_key=$(sed 's/[\^=\$,;+]*//g' <<< "^PASS_MAX_DAYS")

    # shellcheck disable=SC2059
    printf -v formatted_output "%s %s" "$stripped_key" "$var_accounts_maximum_age_login_defs"

    # If the key exists, change it. Otherwise, add it to the config_file.
    # We search for the key string followed by a word boundary (matched by \>),
    # so if we search for 'setting', 'setting2' won't match.
    if LC_ALL=C grep -q -m 1 -i -e "^PASS_MAX_DAYS\\>" "/etc/login.defs"; then
        escaped_formatted_output=$(sed -e 's|/|\\/|g' <<< "$formatted_output")
        LC_ALL=C sed -i --follow-symlinks "s/^PASS_MAX_DAYS\\>.*/$escaped_formatted_output/gi" "/etc/login.defs"
    else
        if [[ -s "/etc/login.defs" ]] && [[ -n "$(tail -c 1 -- "/etc/login.defs" || true)" ]]; then
            LC_ALL=C sed -i --follow-symlinks '$a'\\ "/etc/login.defs"
        fi
        printf '%s\n' "$formatted_output" >> "/etc/login.defs"
    fi

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

#### Rule Set Password Minimum Age [ref]

To specify password minimum age for new accounts, edit the file `/etc/login.defs` and add or correct the following line:

    PASS_MIN_DAYS 1

A value of 1 day is considered sufficient for many environments. The DoD requirement is 1. The profile requirement is `1`.

Rationale:

Enforcing a minimum password lifetime helps to prevent repeated password changes to defeat the password reuse or history enforcement requirement. If users are allowed to immediately and continually change their password, then the password could be repeatedly changed in a short period of time to defeat the organization's policy regarding password reuse.
Setting the minimum password age protects against users cycling back to a favorite password after satisfying the password reuse requirement.

Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_accounts_minimum_age_login_defs

References:

cis-csc | 1, 12, 15, 16, 5
cjis | 5.6.2.1.1
cobit5 | DSS05.04, DSS05.05, DSS05.07, DSS05.10, DSS06.03, DSS06.10
cui | 3.5.8
disa | CCI-004066
isa-62443-2009 | 4.3.3.2.2, 4.3.3.5.1, 4.3.3.5.2, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.2, 4.3.3.7.4
isa-62443-2013 | SR 1.1, SR 1.10, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.7, SR 1.8, SR 1.9, SR 2.1
ism | 0418, 1055, 1402
iso27001-2013 | A.18.1.4, A.7.1.1, A.9.2.1, A.9.2.2, A.9.2.3, A.9.2.4, A.9.2.6, A.9.3.1, A.9.4.2, A.9.4.3
nist | IA-5(f), IA-5(1)(d), CM-6(a)
nist-csf | PR.AC-1, PR.AC-6, PR.AC-7
os-srg | SRG-OS-000075-GPOS-00043
stigid | UBTU-20-010007
cis | 5.4.1.2
stigref | SV-238202r653781_rule

Remediation Shell script ⇲

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}\n' 'login' 2>/dev/null | grep -q '^installed'; then

    var_accounts_minimum_age_login_defs='1'

    # Strip any search characters in the key arg so that the key can be replaced without
    # adding any search characters to the config file.
    stripped_key=$(sed 's/[\^=\$,;+]*//g' <<< "^PASS_MIN_DAYS")

    # shellcheck disable=SC2059
    printf -v formatted_output "%s %s" "$stripped_key" "$var_accounts_minimum_age_login_defs"

    # If the key exists, change it. Otherwise, add it to the config_file.
    # We search for the key string followed by a word boundary (matched by \>),
    # so if we search for 'setting', 'setting2' won't match.
    if LC_ALL=C grep -q -m 1 -i -e "^PASS_MIN_DAYS\\>" "/etc/login.defs"; then
        escaped_formatted_output=$(sed -e 's|/|\\/|g' <<< "$formatted_output")
        LC_ALL=C sed -i --follow-symlinks "s/^PASS_MIN_DAYS\\>.*/$escaped_formatted_output/gi" "/etc/login.defs"
    else
        if [[ -s "/etc/login.defs" ]] && [[ -n "$(tail -c 1 -- "/etc/login.defs" || true)" ]]; then
            LC_ALL=C sed -i --follow-symlinks '$a'\\ "/etc/login.defs"
        fi
        printf '%s\n' "$formatted_output" >> "/etc/login.defs"
    fi

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

#### Rule Set Existing Passwords Maximum Age [ref]

Configure non-compliant accounts to enforce a 365-day maximum password lifetime restriction by running the following command:

    $ sudo chage -M 365
              USER

Rationale: | Any password, no matter how complex, can eventually be cracked. Therefore, passwords need to be changed periodically. If the operating system does not limit the lifetime of passwords and force users to change their passwords, there is the risk that the operating system passwords could be compromised.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_accounts_password_set_max_life_existing

References:

disa | CCI-004066
nist | IA-5(f), IA-5(1)(d), CM-6(a)
os-srg | SRG-OS-000076-GPOS-00044
cis | 5.4.1.1
pcidss4 | 8.3.9, 8.3

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | restrict

    var_accounts_maximum_age_login_defs='365'

    while IFS= read -r i; do

        chage -M $var_accounts_maximum_age_login_defs $i

    done <   <(awk -v var="$var_accounts_maximum_age_login_defs" -F: '(/^[^:]+:[^!*]/ && ($5 > var || $5 == "")) {print $1}' /etc/shadow)

#### Rule Set Existing Passwords Minimum Age [ref]

Configure non-compliant accounts to enforce a 24 hours/1 day minimum password lifetime by running the following command:

    $ sudo chage -m 1 USER

Rationale: | Enforcing a minimum password lifetime helps to prevent repeated password changes to defeat the password reuse or history enforcement requirement. If users are allowed to immediately and continually change their password, the password could be repeatedly changed in a short period of time to defeat the organization's policy regarding password reuse.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_accounts_password_set_min_life_existing

References:

disa | CCI-004066
nist | IA-5(f), IA-5(1)(d), CM-6(a)
os-srg | SRG-OS-000075-GPOS-00043
cis | 5.4.1.2

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | restrict

    var_accounts_minimum_age_login_defs='1'

    while IFS= read -r i; do

        chage -m $var_accounts_minimum_age_login_defs $i

    done <   <(awk -v var="$var_accounts_minimum_age_login_defs" -F: '(/^[^:]+:[^!*]/ && ($4 < var || $4 == "")) {print $1}' /etc/shadow)

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | restrict

    - name: XCCDF Value var_accounts_minimum_age_login_defs # promote to variable
      set_fact:
        var_accounts_minimum_age_login_defs: !!str 1
      tags:
        - always

    - name: Collect users with not correct minimum time period between password changes
      command: |
        awk -F':' '(/^[^:]+:[^!*]/ && ($4 < {{ var_accounts_minimum_age_login_defs }} || $4 == "")) {print $1}' /etc/shadow
      register: user_names
      tags:
      - NIST-800-53-CM-6(a)
      - NIST-800-53-IA-5(1)(d)
      - NIST-800-53-IA-5(f)
      - accounts_password_set_min_life_existing
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy

    - name: Change the minimum time period between password changes
      command: |
        chage -m {{ var_accounts_minimum_age_login_defs }} {{ item }}
      with_items: '{{ user_names.stdout_lines }}'
      when: user_names.stdout_lines | length > 0
      tags:
      - NIST-800-53-CM-6(a)
      - NIST-800-53-IA-5(1)(d)
      - NIST-800-53-IA-5(f)
      - accounts_password_set_min_life_existing
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy

#### Rule Set Password Warning Age [ref]

To specify how many days prior to password expiration that a warning will be issued to users, edit the file `/etc/login.defs` and add or correct the following line:

    PASS_WARN_AGE 7

The DoD requirement is 7. The profile requirement is `7`.

Rationale: | Setting the password warning age enables users to make the change at a practical time.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_accounts_password_warn_age_login_defs

References:

cis-csc | 1, 12, 13, 14, 15, 16, 18, 3, 5, 7, 8
cobit5 | DSS01.03, DSS03.05, DSS05.04, DSS05.05, DSS05.07, DSS05.10, DSS06.03, DSS06.10
cui | 3.5.8
isa-62443-2009 | 4.3.3.2.2, 4.3.3.5.1, 4.3.3.5.2, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.2, 4.3.3.7.3, 4.3.3.7.4
isa-62443-2013 | SR 1.1, SR 1.10, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 6.2
ism | 0418, 1055, 1402
iso27001-2013 | A.12.4.1, A.12.4.3, A.18.1.4, A.6.1.2, A.7.1.1, A.9.1.2, A.9.2.1, A.9.2.2, A.9.2.3, A.9.2.4, A.9.2.6, A.9.3.1, A.9.4.1, A.9.4.2, A.9.4.3, A.9.4.4, A.9.4.5
nist | IA-5(f), IA-5(1)(d), CM-6(a)
nist-csf | DE.CM-1, DE.CM-3, PR.AC-1, PR.AC-4, PR.AC-6, PR.AC-7
pcidss | Req-8.2.4
cis | 5.4.1.3
pcidss4 | 8.3.9, 8.3

Remediation Shell script ⇲

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}\n' 'login' 2>/dev/null | grep -q '^installed'; then

    var_accounts_password_warn_age_login_defs='7'

    # Strip any search characters in the key arg so that the key can be replaced without
    # adding any search characters to the config file.
    stripped_key=$(sed 's/[\^=\$,;+]*//g' <<< "^PASS_WARN_AGE")

    # shellcheck disable=SC2059
    printf -v formatted_output "%s %s" "$stripped_key" "$var_accounts_password_warn_age_login_defs"

    # If the key exists, change it. Otherwise, add it to the config_file.
    # We search for the key string followed by a word boundary (matched by \>),
    # so if we search for 'setting', 'setting2' won't match.
    if LC_ALL=C grep -q -m 1 -i -e "^PASS_WARN_AGE\\>" "/etc/login.defs"; then
        escaped_formatted_output=$(sed -e 's|/|\\/|g' <<< "$formatted_output")
        LC_ALL=C sed -i --follow-symlinks "s/^PASS_WARN_AGE\\>.*/$escaped_formatted_output/gi" "/etc/login.defs"
    else
        if [[ -s "/etc/login.defs" ]] && [[ -n "$(tail -c 1 -- "/etc/login.defs" || true)" ]]; then
            LC_ALL=C sed -i --follow-symlinks '$a'\\ "/etc/login.defs"
        fi
        printf '%s\n' "$formatted_output" >> "/etc/login.defs"
    fi

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Group Verify Proper Storage and Existence of Password Hashes Group contains 6 rules

[ref] By default, password hashes for local accounts are stored in the second field (colon-separated) in `/etc/shadow`. This file should be readable only by processes running with root credentials, preventing users from casually accessing others' password hashes and attempting to crack them. However, it remains possible to misconfigure the system and store password hashes in world-readable files such as `/etc/passwd`, or to even store passwords themselves in plaintext on the system. Using system-provided tools for password change/creation should allow administrators to avoid such misconfiguration.

#### Rule Verify All Account Password Hashes are Shadowed with SHA512 [ref]

Verify the operating system requires the shadow password suite configuration be set to encrypt interactive user passwords using a strong cryptographic hash. Check that the interactive user account passwords are using a strong password hash with the following command:

    $ sudo cut -d: -f2 /etc/shadow
    $6$kcOnRq/5$NUEYPuyL.wghQwWssXRcLRFiiru7f5JPV6GaJhNC2aK5F3PZpE/BCCtwrxRc/AInKMNX3CdMw11m9STiql12f/

Password hashes `!` or `*` indicate inactive accounts not available for logon and are not evaluated. If any interactive user password hash does not begin with `$6`, this is a finding.

Rationale: | Passwords need to be protected at all times, and encryption is the standard method for protecting passwords. If passwords are not encrypted, they can be plainly read (i.e., clear text) and easily compromised.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_accounts_password_all_shadowed_sha512

References:

disa | CCI-000803, CCI-004062
nist | IA-5(1)(c), IA-5(1).1(v), IA-7, IA-7.1
os-srg | SRG-OS-000073-GPOS-00041, SRG-OS-000120-GPOS-00061
cis | 5.3.4

#### Rule Ensure all users last password change date is in the past [ref]

All users should have a password change date in the past. Warning: Automatic remediation is not available, in order to avoid any system disruption.
Rationale: | If a user recorded password change date is in the future then they could bypass any set password expiration.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_accounts_password_last_change_is_in_past

References:

cis | 5.4.1.5
pcidss4 | 8.3.5, 8.3

#### Rule All GIDs referenced in /etc/passwd must be defined in /etc/group [ref]

Add a group to the system for each GID referenced without a corresponding group.
Rationale: | If a user is assigned the Group Identifier (GID) of a group not existing on the system, and a group with the Group Identifier (GID) is subsequently created, the user may have unintended rights to any files associated with the group.
Severity: | low
Rule ID: | xccdf_org.ssgproject.content_rule_gid_passwd_group_same

References:

cis-csc | 1, 12, 15, 16, 5
cjis | 5.5.2
cobit5 | DSS05.04, DSS05.05, DSS05.07, DSS05.10, DSS06.03, DSS06.10
disa | CCI-000764
isa-62443-2009 | 4.3.3.2.2, 4.3.3.5.1, 4.3.3.5.2, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.2, 4.3.3.7.4
isa-62443-2013 | SR 1.1, SR 1.10, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.7, SR 1.8, SR 1.9, SR 2.1
iso27001-2013 | A.18.1.4, A.7.1.1, A.9.2.1, A.9.2.2, A.9.2.3, A.9.2.4, A.9.2.6, A.9.3.1, A.9.4.2, A.9.4.3
nerc-cip | CIP-003-8 R5.1.1, CIP-003-8 R5.3, CIP-004-6 R2.2.3, CIP-004-6 R2.3, CIP-007-3 R5.1, CIP-007-3 R5.1.2, CIP-007-3 R5.2, CIP-007-3 R5.3.1, CIP-007-3 R5.3.2, CIP-007-3 R5.3.3
nist | IA-2, CM-6(a)
nist-csf | PR.AC-1, PR.AC-6, PR.AC-7
pcidss | Req-8.5.a
os-srg | SRG-OS-000104-GPOS-00051
cis | 6.2.12
pcidss4 | 8.2.2, 8.2

#### Rule Prevent Login to Accounts With Empty Password [ref]

If an account is configured for password authentication but does not have an assigned password, it may be possible to log into the account without authentication. Remove any instances of the `nullok` in `/etc/pam.d/common-password` to prevent logins with empty passwords.
Warning: If the system relies on `authselect` tool to manage PAM settings, the remediation will also use `authselect` tool. However, if any manual modification was made in PAM files, the `authselect` integrity check will fail and the remediation will be aborted in order to preserve intentional changes. In this case, an informative message will be shown in the remediation report. Note that this rule is not applicable for systems running within a container. Having user with empty password within a container is not considered a risk, because it should not be possible to directly login into a container anyway.

Rationale: | If an account has an empty password, anyone could log in and run commands with the privileges of that account. Accounts with empty passwords should never be used in operational environments.
Severity: | high
Rule ID: | xccdf_org.ssgproject.content_rule_no_empty_passwords

References:

cis-csc | 1, 12, 13, 14, 15, 16, 18, 3, 5
cjis | 5.5.2
cobit5 | APO01.06, DSS05.04, DSS05.05, DSS05.07, DSS05.10, DSS06.02, DSS06.03, DSS06.10
cui | 3.1.1, 3.1.5
disa | CCI-000366
hipaa | 164.308(a)(1)(ii)(B), 164.308(a)(7)(i), 164.308(a)(7)(ii)(A), 164.310(a)(1), 164.310(a)(2)(i), 164.310(a)(2)(ii), 164.310(a)(2)(iii), 164.310(b), 164.310(c), 164.310(d)(1), 164.310(d)(2)(iii)
isa-62443-2009 | 4.3.3.2.2, 4.3.3.5.1, 4.3.3.5.2, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.2, 4.3.3.7.3, 4.3.3.7.4
isa-62443-2013 | SR 1.1, SR 1.10, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 5.2
iso27001-2013 | A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.13.1.1, A.13.1.3, A.13.2.1, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, A.18.1.4, A.6.1.2, A.7.1.1, A.7.1.2, A.7.3.1, A.8.2.2, A.8.2.3, A.9.1.1, A.9.1.2, A.9.2.1, A.9.2.2, A.9.2.3, A.9.2.4, A.9.2.6, A.9.3.1, A.9.4.1, A.9.4.2, A.9.4.3, A.9.4.4, A.9.4.5
nist | IA-5(1)(a), IA-5(c), CM-6(a)
nist-csf | PR.AC-1, PR.AC-4, PR.AC-6, PR.AC-7, PR.DS-5
ospp | FIA_UAU.1
pcidss | Req-8.2.3
os-srg | SRG-OS-000480-GPOS-00227
stigid | UBTU-20-010463
cis | 6.2.1
pcidss4 | 8.3.1, 8.3
stigref | SV-251504r832977_rule

Remediation Shell script ⇲

Complexity: | low
Disruption: | medium
Reboot: | false
Strategy: | configure

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}\n' 'libpam-runtime' 2>/dev/null | grep -q '^installed'; then

    conf_name=cac_unix
    conf_path="/usr/share/pam-configs"

    if [ ! -f "$conf_path"/"$conf_name" ]; then
        if [ -f "$conf_path"/unix ]; then
            if grep -q "$(md5sum "$conf_path"/unix | cut -d ' ' -f 1)" /var/lib/dpkg/info/libpam-runtime.md5sums;then
                cp "$conf_path"/unix "$conf_path"/"$conf_name"
                sed -i 's/Priority: [0-9]\+/Priority: 257\
    Conflicts: unix/' "$conf_path"/"$conf_name"
                DEBIAN_FRONTEND=noninteractive pam-auth-update
            else
                echo "Not applicable - checksum of $conf_path/unix does not match the original." >&2
            fi
        else
            echo "Not applicable - $conf_path/unix does not exist" >&2
        fi
    fi
    config_file="/usr/share/pam-configs/cac_unix"
    sed -i -E '/^Password:/,/^[^[:space:]]/ {
        /pam_unix\.so/ {
            s/\s*nullok//g
        }
    }' "$config_file"

    sed -i -E '/^Password-Initial:/,/^[^[:space:]]/ {
        /pam_unix\.so/ {
            s/\s*nullok//g
        }
    }' "$config_file"

    DEBIAN_FRONTEND=noninteractive pam-auth-update

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | medium
Reboot: | false
Strategy: | configure

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - CJIS-5.5.2
      - DISA-STIG-UBTU-20-010463
      - NIST-800-171-3.1.1
      - NIST-800-171-3.1.5
      - NIST-800-53-CM-6(a)
      - NIST-800-53-IA-5(1)(a)
      - NIST-800-53-IA-5(c)
      - PCI-DSS-Req-8.2.3
      - PCI-DSSv4-8.3
      - PCI-DSSv4-8.3.1
      - configure_strategy
      - high_severity
      - low_complexity
      - medium_disruption
      - no_empty_passwords
      - no_reboot_needed

    - name: Prevent Login to Accounts With Empty Password - Check if system relies on
        authselect
      ansible.builtin.stat:
        path: /usr/bin/authselect
      register: result_authselect_present
      when: '"libpam-runtime" in ansible_facts.packages'
      tags:
      - CJIS-5.5.2
      - DISA-STIG-UBTU-20-010463
      - NIST-800-171-3.1.1
      - NIST-800-171-3.1.5
      - NIST-800-53-CM-6(a)
      - NIST-800-53-IA-5(1)(a)
      - NIST-800-53-IA-5(c)
      - PCI-DSS-Req-8.2.3
      - PCI-DSSv4-8.3
      - PCI-DSSv4-8.3.1
      - configure_strategy
      - high_severity
      - low_complexity
      - medium_disruption
      - no_empty_passwords
      - no_reboot_needed

    - name: Prevent Login to Accounts With Empty Password - Remediate using authselect
      block:

      - name: Prevent Login to Accounts With Empty Password - Check integrity of authselect
          current profile
        ansible.builtin.command:
          cmd: authselect check
        register: result_authselect_check_cmd
        changed_when: false
        failed_when: false

      - name: Prevent Login to Accounts With Empty Password - Informative message based
          on the authselect integrity check result
        ansible.builtin.assert:
          that:
          - result_authselect_check_cmd.rc == 0
          fail_msg:
          - authselect integrity check failed. Remediation aborted!
          - This remediation could not be applied because an authselect profile was not
            selected or the selected profile is not intact.
          - It is not recommended to manually edit the PAM files when authselect tool
            is available.
          - In cases where the default authselect profile does not cover a specific demand,
            a custom authselect profile is recommended.
          success_msg:
          - authselect integrity check passed

      - name: Prevent Login to Accounts With Empty Password - Get authselect current features
        ansible.builtin.shell:
          cmd: authselect current | tail -n+3 | awk '{ print $2 }'
        register: result_authselect_features
        changed_when: false
        when:
        - result_authselect_check_cmd is success

      - name: Prevent Login to Accounts With Empty Password - Ensure "without-nullok"
          feature is enabled using authselect tool
        ansible.builtin.command:
          cmd: authselect enable-feature without-nullok
        register: result_authselect_enable_feature_cmd
        when:
        - result_authselect_check_cmd is success
        - result_authselect_features.stdout is not search("without-nullok")

      - name: Prevent Login to Accounts With Empty Password - Ensure authselect changes
          are applied
        ansible.builtin.command:
          cmd: authselect apply-changes -b
        when:
        - result_authselect_enable_feature_cmd is not skipped
        - result_authselect_enable_feature_cmd is success
      when:
      - '"libpam-runtime" in ansible_facts.packages'
      - result_authselect_present.stat.exists
      tags:
      - CJIS-5.5.2
      - DISA-STIG-UBTU-20-010463
      - NIST-800-171-3.1.1
      - NIST-800-171-3.1.5
      - NIST-800-53-CM-6(a)
      - NIST-800-53-IA-5(1)(a)
      - NIST-800-53-IA-5(c)
      - PCI-DSS-Req-8.2.3
      - PCI-DSSv4-8.3
      - PCI-DSSv4-8.3.1
      - configure_strategy
      - high_severity
      - low_complexity
      - medium_disruption
      - no_empty_passwords
      - no_reboot_needed

    - name: Prevent Login to Accounts With Empty Password - Remediate directly editing
        PAM files
      ansible.builtin.replace:
        dest: '{{ item }}'
        regexp: nullok
      loop:
      - /etc/pam.d/common-password
      when:
      - '"libpam-runtime" in ansible_facts.packages'
      - not result_authselect_present.stat.exists
      tags:
      - CJIS-5.5.2
      - DISA-STIG-UBTU-20-010463
      - NIST-800-171-3.1.1
      - NIST-800-171-3.1.5
      - NIST-800-53-CM-6(a)
      - NIST-800-53-IA-5(1)(a)
      - NIST-800-53-IA-5(c)
      - PCI-DSS-Req-8.2.3
      - PCI-DSSv4-8.3
      - PCI-DSSv4-8.3.1
      - configure_strategy
      - high_severity
      - low_complexity
      - medium_disruption
      - no_empty_passwords
      - no_reboot_needed

#### Rule Verify No .forward Files Exist [ref]

The `.forward` file specifies an email address to forward the user's mail to.
Rationale: | Use of the `.forward` file poses a security risk in that sensitive data may be inadvertently transferred outside the organization. The .forward file also poses a risk as it can be used to execute commands that may perform unintended actions.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_no_forward_files

References:

cis | 6.2.8

#### Rule Verify No netrc Files Exist [ref]

The `.netrc` files contain login information used to auto-login into FTP servers and reside in the user's home directory. These files may contain unencrypted passwords to remote FTP servers making them susceptible to access by unauthorized users and should not be used. Any `.netrc` files should be removed.
Rationale: | Unencrypted passwords for remote FTP servers may be stored in `.netrc` files.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_no_netrc_files

References:

cis-csc | 1, 11, 12, 14, 15, 16, 18, 3, 5
cobit5 | DSS05.02, DSS05.04, DSS05.05, DSS05.07, DSS05.10, DSS06.03, DSS06.06, DSS06.10
disa | CCI-000196
isa-62443-2009 | 4.3.3.2.2, 4.3.3.5.1, 4.3.3.5.2, 4.3.3.5.3, 4.3.3.5.4, 4.3.3.5.5, 4.3.3.5.6, 4.3.3.5.7, 4.3.3.5.8, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.1, 4.3.3.7.2, 4.3.3.7.3, 4.3.3.7.4
isa-62443-2013 | SR 1.1, SR 1.10, SR 1.11, SR 1.12, SR 1.13, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.6, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 2.2, SR 2.3, SR 2.4, SR 2.5, SR 2.6, SR 2.7
iso27001-2013 | A.18.1.4, A.6.1.2, A.7.1.1, A.9.1.2, A.9.2.1, A.9.2.2, A.9.2.3, A.9.2.4, A.9.2.6, A.9.3.1, A.9.4.1, A.9.4.2, A.9.4.3, A.9.4.4, A.9.4.5
nerc-cip | CIP-003-8 R1.3, CIP-003-8 R3, CIP-003-8 R3.1, CIP-003-8 R3.2, CIP-003-8 R3.3, CIP-003-8 R5.1.1, CIP-003-8 R5.3, CIP-004-6 R2.2.3, CIP-004-6 R2.3, CIP-007-3 R5.1, CIP-007-3 R5.1.2, CIP-007-3 R5.2, CIP-007-3 R5.3.1, CIP-007-3 R5.3.2, CIP-007-3 R5.3.3
nist | IA-5(h), IA-5(1)(c), CM-6(a), IA-5(7)
nist-csf | PR.AC-1, PR.AC-4, PR.AC-6, PR.AC-7, PR.PT-3
cis | 6.2.9

Group Restrict Root Logins Group contains 6 rules

[ref] Direct root logins should be allowed only for emergency use. In normal situations, the administrator should access the system via a unique unprivileged account, and then use `su` or `sudo` to execute privileged commands. Discouraging administrators from accessing the root account directly ensures an audit trail in organizations with multiple administrators. Locking down the channels through which root can connect directly also reduces opportunities for password-guessing against the root account. The `login` program uses the file `/etc/securetty` to determine which interfaces should allow root logins. The virtual devices `/dev/console` and `/dev/tty*` represent the system consoles (accessible via the Ctrl-Alt-F1 through Ctrl-Alt-F6 keyboard sequences on a default installation). The default securetty file also contains `/dev/vc/*`. These are likely to be deprecated in most environments, but may be retained for compatibility. Root should also be prohibited from connecting via network protocols. Other sections of this document include guidance describing how to prevent root from logging in via SSH.

#### Rule Verify Only Root Has UID 0 [ref]

If any account other than root has a UID of 0, this misconfiguration should be investigated and the accounts other than root should be removed or have their UID changed. If the account is associated with system commands or applications the UID should be changed to one greater than "0" but less than "1000." Otherwise assign a UID greater than "1000" that has not already been assigned.
Rationale: | An account has root authority if it has a UID of 0. Multiple accounts with a UID of 0 afford more opportunity for potential intruders to guess a password for a privileged account. Proper configuration of sudo is recommended to afford multiple system administrators access to root privileges in an accountable manner.
Severity: | high
Rule ID: | xccdf_org.ssgproject.content_rule_accounts_no_uid_except_zero

References:

cis-csc | 1, 12, 13, 14, 15, 16, 18, 3, 5
cobit5 | APO01.06, DSS05.04, DSS05.05, DSS05.07, DSS05.10, DSS06.02, DSS06.03, DSS06.10
cui | 3.1.1, 3.1.5
disa | CCI-000366
isa-62443-2009 | 4.3.3.2.2, 4.3.3.5.1, 4.3.3.5.2, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.2, 4.3.3.7.3, 4.3.3.7.4
isa-62443-2013 | SR 1.1, SR 1.10, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 5.2
iso27001-2013 | A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.13.1.1, A.13.1.3, A.13.2.1, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, A.18.1.4, A.6.1.2, A.7.1.1, A.7.1.2, A.7.3.1, A.8.2.2, A.8.2.3, A.9.1.1, A.9.1.2, A.9.2.1, A.9.2.2, A.9.2.3, A.9.2.4, A.9.2.6, A.9.3.1, A.9.4.1, A.9.4.2, A.9.4.3, A.9.4.4, A.9.4.5
nerc-cip | CIP-003-8 R5.1.1, CIP-003-8 R5.3, CIP-004-6 R2.2.3, CIP-004-6 R2.3, CIP-007-3 R5.1, CIP-007-3 R5.1.2, CIP-007-3 R5.2, CIP-007-3 R5.3.1, CIP-007-3 R5.3.2, CIP-007-3 R5.3.3
nist | IA-2, AC-6(5), IA-4(b)
nist-csf | PR.AC-1, PR.AC-4, PR.AC-6, PR.AC-7, PR.DS-5
pcidss | Req-8.5
os-srg | SRG-OS-000480-GPOS-00227
cis | 6.2.2
pcidss4 | 8.2.1, 8.2

Remediation Shell script ⇲

    awk -F: '$3 == 0 && $1 != "root" { print $1 }' /etc/passwd | xargs --no-run-if-empty --max-lines=1 passwd -l

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | restrict

    - name: Get all /etc/passwd file entries
      getent:
        database: passwd
        split: ':'
      tags:
      - NIST-800-171-3.1.1
      - NIST-800-171-3.1.5
      - NIST-800-53-AC-6(5)
      - NIST-800-53-IA-2
      - NIST-800-53-IA-4(b)
      - PCI-DSS-Req-8.5
      - PCI-DSSv4-8.2
      - PCI-DSSv4-8.2.1
      - accounts_no_uid_except_zero
      - high_severity
      - low_complexity
      - low_disruption
      - no_reboot_needed
      - restrict_strategy

    - name: Lock the password of the user accounts other than root with uid 0
      command: passwd -l {{ item.key }}
      loop: '{{ getent_passwd | dict2items | rejectattr(''key'', ''search'', ''root'')
        | list }}'
      when: item.value.1  == '0'
      tags:
      - NIST-800-171-3.1.1
      - NIST-800-171-3.1.5
      - NIST-800-53-AC-6(5)
      - NIST-800-53-IA-2
      - NIST-800-53-IA-4(b)
      - PCI-DSS-Req-8.5
      - PCI-DSSv4-8.2
      - PCI-DSSv4-8.2.1
      - accounts_no_uid_except_zero
      - high_severity
      - low_complexity
      - low_disruption
      - no_reboot_needed
      - restrict_strategy

#### Rule Verify Root Has A Primary GID 0 [ref]

The `root` user should have a primary group of 0.
Rationale: | To help ensure that root-owned files are not inadvertently exposed to other users.
Severity: | high
Rule ID: | xccdf_org.ssgproject.content_rule_accounts_root_gid_zero

References:

pcidss | Req-8.1.1
cis | 5.4.3
pcidss4 | 8.2.1, 8.2

#### Rule Ensure the Group Used by pam_wheel.so Module Exists on System and is Empty [ref]

Ensure that the group `sugroup` referenced by `var_pam_wheel_group_for_su` variable and used as value for the `pam_wheel.so` `group` option exists and has no members. This empty group used by `pam_wheel.so` in `/etc/pam.d/su` ensures that no user can run commands with altered privileges through the `su` command.
Warning: Note that this rule just ensures the group exists and has no members. This rule does not configure `pam_wheel.so` module. The `pam_wheel.so` module configuration is accomplished by `use_pam_wheel_group_for_su` rule.

Rationale: | The `su` program allows to run commands with a substitute user and group ID. It is commonly used to run commands as the root user. Limiting access to such command is considered a good security practice.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_ensure_pam_wheel_group_empty

References:

cis | 5.6
pcidss4 | 2.2.6, 2.2

Remediation Shell script ⇲

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}\n' 'libpam-runtime' 2>/dev/null | grep -q '^installed'; then

    var_pam_wheel_group_for_su='sugroup'

    if ! grep -q "^${var_pam_wheel_group_for_su}:[^:]*:[^:]*:[^:]*" /etc/group; then
        groupadd ${var_pam_wheel_group_for_su}
    fi

    # group must be empty
    gpasswd -M '' ${var_pam_wheel_group_for_su}

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | restrict

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - ensure_pam_wheel_group_empty
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy
    - name: XCCDF Value var_pam_wheel_group_for_su # promote to variable
      set_fact:
        var_pam_wheel_group_for_su: !!str sugroup
      tags:
        - always

    - name: Ensure the Group Used by pam_wheel.so Module Exists on System and is Empty
        - Ensure {{ var_pam_wheel_group_for_su }} Group Exists
      ansible.builtin.group:
        name: '{{ var_pam_wheel_group_for_su }}'
        state: present
      when: '"libpam-runtime" in ansible_facts.packages'
      tags:
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - ensure_pam_wheel_group_empty
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy

    - name: Ensure the Group Used by pam_wheel.so Module Exists on System and is Empty
        - Ensure {{ var_pam_wheel_group_for_su }} Group is Empty
      ansible.builtin.lineinfile:
        path: /etc/group
        regexp: ^({{ var_pam_wheel_group_for_su }}:[^:]+:[0-9]+:).*$
        line: \1
        backrefs: true
      when: '"libpam-runtime" in ansible_facts.packages'
      tags:
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - ensure_pam_wheel_group_empty
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy

#### Rule Ensure Authentication Required for Single User Mode [ref]

Single user mode is used for recovery when the system detects an issue during boot or by manual selection from the bootloader.
Rationale: | Requiring authentication in single user mode prevents an unauthorized user from rebooting the system into single user to gain root privileges without credentials.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_ensure_root_password_configured

References:

cis | 1.5.3
pcidss4 | 2.2.2, 2.2

#### Rule Ensure that System Accounts Do Not Run a Shell Upon Login [ref]

Some accounts are not associated with a human user of the system, and exist to perform some administrative functions. Should an attacker be able to log into these accounts, they should not be granted access to a shell.
The login shell for each local account is stored in the last field of each line in `/etc/passwd`. System accounts are those user accounts with a user ID less than `1000`. The user ID is stored in the third field. If any system account other than `root` has a login shell, disable it with the command:

    $ sudo usermod -s /sbin/nologin account

Warning: Do not perform the steps in this section on the root account. Doing so might cause the system to become inaccessible.

Rationale: | Ensuring shells are not given to system accounts upon login makes it more difficult for attackers to make use of system accounts.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_no_shelllogin_for_systemaccounts

References:

cis-csc | 1, 12, 13, 14, 15, 16, 18, 3, 5, 7, 8
cobit5 | DSS01.03, DSS03.05, DSS05.04, DSS05.05, DSS05.07, DSS06.03
disa | CCI-000366
isa-62443-2009 | 4.3.3.2.2, 4.3.3.5.1, 4.3.3.5.2, 4.3.3.7.2, 4.3.3.7.3, 4.3.3.7.4
isa-62443-2013 | SR 1.1, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 6.2
ism | 1491
iso27001-2013 | A.12.4.1, A.12.4.3, A.6.1.2, A.7.1.1, A.9.1.2, A.9.2.1, A.9.2.2, A.9.2.3, A.9.2.4, A.9.2.6, A.9.3.1, A.9.4.1, A.9.4.2, A.9.4.3, A.9.4.4, A.9.4.5
nist | AC-6, CM-6(a), CM-6(b), CM-6.1(iv)
nist-csf | DE.CM-1, DE.CM-3, PR.AC-1, PR.AC-4, PR.AC-6
os-srg | SRG-OS-000480-GPOS-00227
cis | 5.4.2
pcidss4 | 8.2.2, 8.2

Remediation Shell script ⇲

Complexity: | low
Disruption: | medium
Reboot: | false
Strategy: | restrict

    readarray -t systemaccounts < <(awk -F: '($3 < 1000 && $3 != root \
      && $7 != "\/sbin\/shutdown" && $7 != "\/sbin\/halt" && $7 != "\/bin\/sync") \
      { print $1 }' /etc/passwd)

    for systemaccount in "${systemaccounts[@]}"; do
        usermod -s /sbin/nologin "$systemaccount"
    done

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | medium
Reboot: | false
Strategy: | restrict

    - name: Ensure that System Accounts Do Not Run a Shell Upon Login - Get All Local
        Users From /etc/passwd
      ansible.builtin.getent:
        database: passwd
        split: ':'
      tags:
      - NIST-800-53-AC-6
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-6(b)
      - NIST-800-53-CM-6.1(iv)
      - PCI-DSSv4-8.2
      - PCI-DSSv4-8.2.2
      - low_complexity
      - medium_disruption
      - medium_severity
      - no_reboot_needed
      - no_shelllogin_for_systemaccounts
      - restrict_strategy

    - name: Ensure that System Accounts Do Not Run a Shell Upon Login - Create local_users
        Variable From getent_passwd Facts
      ansible.builtin.set_fact:
        local_users: '{{ ansible_facts.getent_passwd | dict2items }}'
      tags:
      - NIST-800-53-AC-6
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-6(b)
      - NIST-800-53-CM-6.1(iv)
      - PCI-DSSv4-8.2
      - PCI-DSSv4-8.2.2
      - low_complexity
      - medium_disruption
      - medium_severity
      - no_reboot_needed
      - no_shelllogin_for_systemaccounts
      - restrict_strategy

    - name: Ensure that System Accounts Do Not Run a Shell Upon Login -  Disable Login
        Shell for System Accounts
      ansible.builtin.user:
        name: '{{ item.key }}'
        shell: /sbin/nologin
      loop: '{{ local_users }}'
      when:
      - item.key not in ['root']
      - item.value[1]|int < 1000
      - item.value[5] not in ['/sbin/shutdown', '/sbin/halt', '/bin/sync']
      tags:
      - NIST-800-53-AC-6
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-6(b)
      - NIST-800-53-CM-6.1(iv)
      - PCI-DSSv4-8.2
      - PCI-DSSv4-8.2.2
      - low_complexity
      - medium_disruption
      - medium_severity
      - no_reboot_needed
      - no_shelllogin_for_systemaccounts
      - restrict_strategy

#### Rule Enforce Usage of pam_wheel with Group Parameter for su Authentication [ref]

To ensure that only users who are members of the group set in the `group` option of `pam_wheel.so` module can run commands with altered privileges through the `su` command, make sure that the following line exists in the file `/etc/pam.d/su`:

    auth required pam_wheel.so use_uid group=sugroup

Warning: Note that `ensure_pam_wheel_group_empty` rule complements this requirement by ensuring the referenced group exists and has no members.

Rationale: | The `su` program allows to run commands with a substitute user and group ID. It is commonly used to run commands as the root user. Limiting access to such command is considered a good security practice.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_use_pam_wheel_group_for_su

References:

cis | 5.6
pcidss4 | 2.2.6, 2.2

Remediation Shell script ⇲

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}\n' 'libpam-runtime' 2>/dev/null | grep -q '^installed'; then

    var_pam_wheel_group_for_su='sugroup'

    PAM_CONF=/etc/pam.d/su

    pamstr=$(grep -P '^auth\s+required\s+pam_wheel\.so\s+(?=[^#]*\buse_uid\b)(?=[^#]*\bgroup=)' ${PAM_CONF})
    if [ -z "$pamstr" ]; then
        sed -Ei '/^auth\b.*\brequired\b.*\bpam_wheel\.so/d' ${PAM_CONF} # remove any remaining uncommented pam_wheel.so line
        sed -Ei "/^auth\s+sufficient\s+pam_rootok\.so.*$/a auth             required        pam_wheel.so use_uid group=${var_pam_wheel_group_for_su}" ${PAM_CONF}
    else
        group_val=$(echo -n "$pamstr" | grep -Eo '\bgroup=[_a-z][-0-9_a-z]*' | cut -d '=' -f 2)
        if [ -z "${group_val}" ] || [ ${group_val} != ${var_pam_wheel_group_for_su} ]; then
            sed -Ei "s/(^auth\s+required\s+pam_wheel.so\s+[^#]*group=)[_a-z][-0-9_a-z]*/\1${var_pam_wheel_group_for_su}/" ${PAM_CONF}
        fi
    fi

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | restrict

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy
      - use_pam_wheel_group_for_su
    - name: XCCDF Value var_pam_wheel_group_for_su # promote to variable
      set_fact:
        var_pam_wheel_group_for_su: !!str sugroup
      tags:
        - always

    - name: Enforce Usage of pam_wheel with Group Parameter for su Authentication - Add
        the group to the /etc/pam.d/su file
      ansible.builtin.lineinfile:
        path: /etc/pam.d/su
        state: present
        regexp: ^[\s]*#[\s]*auth[\s]+required[\s]+pam_wheel\.so[\s]+use_uid group=$
        line: auth             required        pam_wheel.so use_uid group={{ var_pam_wheel_group_for_su
          }}
      when: '"libpam-runtime" in ansible_facts.packages'
      tags:
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy
      - use_pam_wheel_group_for_su

#### Rule Ensure All Accounts on the System Have Unique User IDs [ref]

Change user IDs (UIDs), or delete accounts, so each has a unique name. Warning: Automatic remediation of this control is not available due to unique requirements of each system.
Rationale: | To assure accountability and prevent unauthenticated access, interactive users must be identified and authenticated to prevent potential misuse and compromise of the system.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_account_unique_id

References:

disa | CCI-000135, CCI-000764, CCI-000804
pcidss | Req-8.1.1
os-srg | SRG-OS-000104-GPOS-00051, SRG-OS-000121-GPOS-00062
cis | 6.2.13
pcidss4 | 8.2.1, 8.2

#### Rule Ensure All Groups on the System Have Unique Group ID [ref]

Change the group name or delete groups, so each has a unique id. Warning: Automatic remediation of this control is not available due to the unique requirements of each system.
Rationale: | To assure accountability and prevent unauthenticated access, groups must be identified uniquely to prevent potential misuse and compromise of the system.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_group_unique_id

References:

disa | CCI-000764
os-srg | SRG-OS-000104-GPOS-00051
cis | 6.2.14
pcidss4 | 8.2.1, 8.2

#### Rule Ensure All Groups on the System Have Unique Group Names [ref]

Change the group name or delete groups, so each has a unique name. Warning: Automatic remediation of this control is not available due to the unique requirements of each system.
Rationale: | To assure accountability and prevent unauthenticated access, groups must be identified uniquely to prevent potential misuse and compromise of the system.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_group_unique_name

References:

cis | 6.2.16
pcidss4 | 8.2.1, 8.2

Group Secure Session Configuration Files for Login Accounts Group contains 2 groups and 13 rules

[ref] When a user logs into a Unix account, the system configures the user's session by reading a number of files. Many of these files are located in the user's home directory, and may have weak permissions as a result of user error or misconfiguration. If an attacker can modify or even read certain types of account configuration information, they can often gain full access to the affected user's account. Therefore, it is important to test and correct configuration file permissions for interactive accounts, particularly those of privileged users such as root or system administrators.

Group Ensure that No Dangerous Directories Exist in Root's Path Group contains 1 rule

[ref] The active path of the root account can be obtained by starting a new root shell and running:

    # echo $PATH

This will produce a colon-separated list of directories in the path.
Certain path elements could be considered dangerous, as they could lead to root executing unknown or untrusted programs, which could contain malicious code. Since root may sometimes work inside untrusted directories, the `.` character, which represents the current directory, should never be in the root path, nor should any directory which can be written to by an unprivileged or semi-privileged (system) user.
It is a good practice for administrators to always execute privileged commands by typing the full path to the command.

#### Rule Ensure that Root's Path Does Not Include World or Group-Writable Directories [ref]

For each element in root's path, run:

    # ls -ld DIR

and ensure that write permissions are disabled for group and other.

Rationale: | Such entries increase the risk that root could execute code provided by unprivileged users, and potentially malicious code.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_accounts_root_path_dirs_no_write

References:

cis-csc | 11, 3, 9
cobit5 | BAI10.01, BAI10.02, BAI10.03, BAI10.05
disa | CCI-000366
isa-62443-2009 | 4.3.4.3.2, 4.3.4.3.3
isa-62443-2013 | SR 7.6
iso27001-2013 | A.12.1.2, A.12.5.1, A.12.6.2, A.14.2.2, A.14.2.3, A.14.2.4
nist | CM-6(a), CM-6(a)
nist-csf | PR.IP-1
cis | 6.2.3

Group Ensure that Users Have Sensible Umask Values Group contains 5 rules

[ref] The umask setting controls the default permissions for the creation of new files. With a default `umask` setting of 077, files and directories created by users will not be readable by any other user on the system. Users who wish to make specific files group- or world-readable can accomplish this by using the chmod command. Additionally, users can make all their files readable to their group by default by setting a `umask` of 027 in their shell configuration files. If default per-user groups exist (that is, if every user has a default group whose name is the same as that user's username and whose only member is the user), then it may even be safe for users to select a `umask` of 007, making it very easy to intentionally share files with groups of which the user is a member.

#### Rule Ensure the Default Bash Umask is Set Correctly [ref]

To ensure the default umask for users of the Bash shell is set properly, add or correct the `umask` setting in `/etc/bash.bashrc` to read as follows:

    umask 027

Rationale: | The umask value influences the permissions assigned to files when they are created. A misconfigured umask value could result in files with excessive permissions that can be read or written to by unauthorized users.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_accounts_umask_etc_bashrc

References:

cis-csc | 18
cobit5 | APO13.01, BAI03.01, BAI03.02, BAI03.03
disa | CCI-000366
isa-62443-2009 | 4.3.4.3.3
iso27001-2013 | A.14.1.1, A.14.2.1, A.14.2.5, A.6.1.5
nerc-cip | CIP-003-8 R5.1.1, CIP-003-8 R5.3, CIP-004-6 R2.3, CIP-007-3 R2.1, CIP-007-3 R2.2, CIP-007-3 R2.3, CIP-007-3 R5.1, CIP-007-3 R5.1.1, CIP-007-3 R5.1.2
nist | AC-6(1), CM-6(a)
nist-csf | PR.IP-2
os-srg | SRG-OS-000480-GPOS-00228, SRG-OS-000480-GPOS-00227
cis | 5.4.4
anssi | R36

Remediation Shell script ⇲

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}\n' 'bash' 2>/dev/null | grep -q '^installed'; then

    var_accounts_user_umask='027'

    grep -q "^[^#]*\bumask" /etc/bash.bashrc && \
      sed -i -E -e "s/^([^#]*\bumask)[[:space:]]+[[:digit:]]+/\1 $var_accounts_user_umask/g" /etc/bash.bashrc
    if ! [ $? -eq 0 ]; then
        echo "umask $var_accounts_user_umask" >> /etc/bash.bashrc
    fi

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | restrict

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - accounts_umask_etc_bashrc
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy
    - name: XCCDF Value var_accounts_user_umask # promote to variable
      set_fact:
        var_accounts_user_umask: !!str 027
      tags:
        - always

    - name: Check if umask in /etc/bash.bashrc is already set
      ansible.builtin.lineinfile:
        path: /etc/bash.bashrc
        regexp: ^[^#]*\bumask\s+\d+$
        state: absent
      check_mode: true
      changed_when: false
      register: umask_replace
      when: '"bash" in ansible_facts.packages'
      tags:
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - accounts_umask_etc_bashrc
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy

    - name: Replace user umask in /etc/bash.bashrc
      ansible.builtin.replace:
        path: /etc/bash.bashrc
        regexp: ^([^#]*\b)umask\s+\d+$
        replace: \g<1>umask {{ var_accounts_user_umask }}
      when:
      - '"bash" in ansible_facts.packages'
      - umask_replace.found > 0
      tags:
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - accounts_umask_etc_bashrc
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy

    - name: Ensure the Default umask is Appended Correctly
      ansible.builtin.lineinfile:
        create: true
        path: /etc/bash.bashrc
        line: umask {{ var_accounts_user_umask }}
      when:
      - '"bash" in ansible_facts.packages'
      - umask_replace.found == 0
      tags:
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - accounts_umask_etc_bashrc
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy

#### Rule Ensure the Default C Shell Umask is Set Correctly [ref]

To ensure the default umask for users of the C shell is set properly, add or correct the `umask` setting in `/etc/csh.cshrc` to read as follows:

    umask 027

Rationale: | The umask value influences the permissions assigned to files when they are created. A misconfigured umask value could result in files with excessive permissions that can be read or written to by unauthorized users.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_accounts_umask_etc_csh_cshrc

References:

cis-csc | 18
cobit5 | APO13.01, BAI03.01, BAI03.02, BAI03.03
disa | CCI-000366
isa-62443-2009 | 4.3.4.3.3
iso27001-2013 | A.14.1.1, A.14.2.1, A.14.2.5, A.6.1.5
nerc-cip | CIP-003-8 R5.1.1, CIP-003-8 R5.3, CIP-004-6 R2.3, CIP-007-3 R2.1, CIP-007-3 R2.2, CIP-007-3 R2.3, CIP-007-3 R5.1, CIP-007-3 R5.1.1, CIP-007-3 R5.1.2
nist | AC-6(1), CM-6(a)
nist-csf | PR.IP-2
os-srg | SRG-OS-000480-GPOS-00228, SRG-OS-000480-GPOS-00227
cis | 5.4.4

Remediation Shell script ⇲

    var_accounts_user_umask='027'

    grep -q "^\s*umask" /etc/csh.cshrc && \
      sed -i -E -e "s/^(\s*umask).*/\1 $var_accounts_user_umask/g" /etc/csh.cshrc
    if ! [ $? -eq 0 ]; then
        echo "umask $var_accounts_user_umask" >> /etc/csh.cshrc
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | restrict

    - name: XCCDF Value var_accounts_user_umask # promote to variable
      set_fact:
        var_accounts_user_umask: !!str 027
      tags:
        - always

    - name: Check if umask in /etc/csh.cshrc is already set
      ansible.builtin.lineinfile:
        path: /etc/csh.cshrc
        regexp: ^(\s*)umask\s+.*
        state: absent
      check_mode: true
      changed_when: false
      register: umask_replace
      tags:
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - accounts_umask_etc_csh_cshrc
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy

    - name: Replace user umask in /etc/csh.cshrc
      ansible.builtin.replace:
        path: /etc/csh.cshrc
        regexp: ^(\s*)umask(\s+).*
        replace: \g<1>umask\g<2>{{ var_accounts_user_umask }}
      when: umask_replace.found > 0
      tags:
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - accounts_umask_etc_csh_cshrc
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy

    - name: Ensure the Default umask is Appended Correctly
      ansible.builtin.lineinfile:
        create: true
        path: /etc/csh.cshrc
        line: umask {{ var_accounts_user_umask }}
      when: umask_replace.found == 0
      tags:
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - accounts_umask_etc_csh_cshrc
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy

#### Rule Ensure the Default Umask is Set Correctly in login.defs [ref]

To ensure the default umask controlled by `/etc/login.defs` is set properly, add or correct the `UMASK` setting in `/etc/login.defs` to read as follows:

    UMASK 027

Rationale: | The umask value influences the permissions assigned to files when they are created. A misconfigured umask value could result in files with excessive permissions that can be read and written to by unauthorized users.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_accounts_umask_etc_login_defs

References:

cis-csc | 11, 18, 3, 9
cobit5 | APO13.01, BAI03.01, BAI03.02, BAI03.03, BAI10.01, BAI10.02, BAI10.03, BAI10.05
disa | CCI-000366
isa-62443-2009 | 4.3.4.3.2, 4.3.4.3.3
isa-62443-2013 | SR 7.6
iso27001-2013 | A.12.1.2, A.12.5.1, A.12.6.2, A.14.1.1, A.14.2.1, A.14.2.2, A.14.2.3, A.14.2.4, A.14.2.5, A.6.1.5
nerc-cip | CIP-003-8 R5.1.1, CIP-003-8 R5.3, CIP-004-6 R2.3, CIP-007-3 R2.1, CIP-007-3 R2.2, CIP-007-3 R2.3, CIP-007-3 R5.1, CIP-007-3 R5.1.1, CIP-007-3 R5.1.2
nist | AC-6(1), CM-6(a)
nist-csf | PR.IP-1, PR.IP-2
os-srg | SRG-OS-000480-GPOS-00228
stigid | UBTU-20-010016
cis | 5.4.4
anssi | R36
stigref | SV-238209r653802_rule

Remediation Shell script ⇲

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}\n' 'login' 2>/dev/null | grep -q '^installed'; then

    var_accounts_user_umask='027'

    # Strip any search characters in the key arg so that the key can be replaced without
    # adding any search characters to the config file.
    stripped_key=$(sed 's/[\^=\$,;+]*//g' <<< "^UMASK")

    # shellcheck disable=SC2059
    printf -v formatted_output "%s %s" "$stripped_key" "$var_accounts_user_umask"

    # If the key exists, change it. Otherwise, add it to the config_file.
    # We search for the key string followed by a word boundary (matched by \>),
    # so if we search for 'setting', 'setting2' won't match.
    if LC_ALL=C grep -q -m 1 -i -e "^UMASK\\>" "/etc/login.defs"; then
        escaped_formatted_output=$(sed -e 's|/|\\/|g' <<< "$formatted_output")
        LC_ALL=C sed -i --follow-symlinks "s/^UMASK\\>.*/$escaped_formatted_output/gi" "/etc/login.defs"
    else
        if [[ -s "/etc/login.defs" ]] && [[ -n "$(tail -c 1 -- "/etc/login.defs" || true)" ]]; then
            LC_ALL=C sed -i --follow-symlinks '$a'\\ "/etc/login.defs"
        fi
        printf '%s\n' "$formatted_output" >> "/etc/login.defs"
    fi

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | restrict

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - DISA-STIG-UBTU-20-010016
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - accounts_umask_etc_login_defs
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy
    - name: XCCDF Value var_accounts_user_umask # promote to variable
      set_fact:
        var_accounts_user_umask: !!str 027
      tags:
        - always

    - name: Check if UMASK is already set
      ansible.builtin.lineinfile:
        path: /etc/login.defs
        regexp: ^(\s*)UMASK\s+.*
        state: absent
      check_mode: true
      changed_when: false
      register: result_umask_is_set
      when: '"login" in ansible_facts.packages'
      tags:
      - DISA-STIG-UBTU-20-010016
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - accounts_umask_etc_login_defs
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy

    - name: Replace user UMASK in /etc/login.defs
      ansible.builtin.replace:
        path: /etc/login.defs
        regexp: ^(\s*)UMASK(\s+).*
        replace: \g<1>UMASK\g<2>{{ var_accounts_user_umask }}
      when:
      - '"login" in ansible_facts.packages'
      - result_umask_is_set.found > 0
      tags:
      - DISA-STIG-UBTU-20-010016
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - accounts_umask_etc_login_defs
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy

    - name: Ensure the Default UMASK is Appended Correctly
      ansible.builtin.lineinfile:
        create: true
        path: /etc/login.defs
        line: UMASK {{ var_accounts_user_umask }}
      when:
      - '"login" in ansible_facts.packages'
      - result_umask_is_set.found == 0
      tags:
      - DISA-STIG-UBTU-20-010016
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - accounts_umask_etc_login_defs
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy

#### Rule Ensure the Default Umask is Set Correctly in /etc/profile [ref]

To ensure the default umask controlled by `/etc/profile` is set properly, add or correct the `umask` setting in `/etc/profile` to read as follows:

    umask 027

Note that `/etc/profile` also reads scrips within `/etc/profile.d` directory. These scripts are also valid files to set umask value. Therefore, they should also be considered during the check and properly remediated, if necessary.

Rationale: | The umask value influences the permissions assigned to files when they are created. A misconfigured umask value could result in files with excessive permissions that can be read or written to by unauthorized users.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_accounts_umask_etc_profile

References:

cis-csc | 18
cobit5 | APO13.01, BAI03.01, BAI03.02, BAI03.03
disa | CCI-000366
isa-62443-2009 | 4.3.4.3.3
iso27001-2013 | A.14.1.1, A.14.2.1, A.14.2.5, A.6.1.5
nerc-cip | CIP-003-8 R5.1.1, CIP-003-8 R5.3, CIP-004-6 R2.3, CIP-007-3 R2.1, CIP-007-3 R2.2, CIP-007-3 R2.3, CIP-007-3 R5.1, CIP-007-3 R5.1.1, CIP-007-3 R5.1.2
nist | AC-6(1), CM-6(a)
nist-csf | PR.IP-2
os-srg | SRG-OS-000480-GPOS-00228, SRG-OS-000480-GPOS-00227
cis | 5.4.4
anssi | R36

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | restrict

    var_accounts_user_umask='027'

    readarray -t profile_files < <(find /etc/profile.d/ -type f -name '*.sh' -or -name 'sh.local')

    for file in "${profile_files[@]}" /etc/profile; do
      grep -qE '^[^#]*umask' "$file" && sed -i -E "s/^(\s*umask\s*)[0-7]+/\1$var_accounts_user_umask/g" "$file"
    done

    if ! grep -qrE '^[^#]*umask' /etc/profile*; then
      echo "umask $var_accounts_user_umask" >> /etc/profile
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | restrict

    - name: XCCDF Value var_accounts_user_umask # promote to variable
      set_fact:
        var_accounts_user_umask: !!str 027
      tags:
        - always

    - name: Ensure the Default Umask is Set Correctly in /etc/profile - Locate Profile
        Configuration Files Where umask Is Defined
      ansible.builtin.find:
        paths:
        - /etc/profile.d
        patterns:
        - sh.local
        - '*.sh'
        contains: ^[\s]*umask\s+\d+
      register: result_profile_d_files
      tags:
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - accounts_umask_etc_profile
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy

    - name: Ensure the Default Umask is Set Correctly in /etc/profile - Replace Existing
        umask Value in Files From /etc/profile.d
      ansible.builtin.replace:
        path: '{{ item.path }}'
        regexp: ^(\s*)umask\s+\d+
        replace: \1umask {{ var_accounts_user_umask }}
      loop: '{{ result_profile_d_files.files }}'
      register: result_umask_replaced_profile_d
      when: result_profile_d_files.matched
      tags:
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - accounts_umask_etc_profile
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy

    - name: Ensure the Default Umask is Set Correctly in /etc/profile - Ensure umask Is
        Set in /etc/profile if Not Already Set Elsewhere
      ansible.builtin.lineinfile:
        create: true
        mode: 420
        path: /etc/profile
        line: umask {{ var_accounts_user_umask }}
      when: not result_profile_d_files.matched
      tags:
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - accounts_umask_etc_profile
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy

    - name: Ensure the Default Umask is Set Correctly in /etc/profile - Ensure umask Value
        For All Existing umask Definition in /etc/profile
      ansible.builtin.replace:
        path: /etc/profile
        regexp: ^(\s*)umask\s+\d+
        replace: \1umask {{ var_accounts_user_umask }}
      register: result_umask_replaced_profile
      tags:
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - accounts_umask_etc_profile
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy

#### Rule Ensure the Default Umask is Set Correctly For Interactive Users [ref]

Remove the `UMASK` environment variable from all interactive users initialization files.

Rationale:

The umask controls the default access mode assigned to newly created files. A umask of 077 limits new files to mode 700 or less permissive. Although umask can be represented as a four-digit number, the first digit representing special access modes is typically ignored or required to be 0. This requirement applies to the globally configured system defaults and the local interactive user defaults for each account on the system.

Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_accounts_umask_interactive_users

References:

disa | CCI-000366
os-srg | SRG-OS-000480-GPOS-00227, SRG-OS-000480-GPOS-00228
cis | 5.4.4

#### Rule Set Interactive Session Timeout [ref]

Setting the `TMOUT` option in `/etc/profile` ensures that all user sessions will terminate based on inactivity. The value of TMOUT should be exported and read only. The `TMOUT` setting in a file loaded by `/etc/profile`, e.g. `/etc/profile.d/tmout.sh` should read as follows:

    TMOUT=900

readonly TMOUT export TMOUT

Rationale: | Terminating an idle session within a short time period reduces the window of opportunity for unauthorized personnel to take control of a management session enabled on the console or console port that has been left unattended.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_accounts_tmout

References:

cis-csc | 1, 12, 15, 16
cobit5 | DSS05.04, DSS05.10, DSS06.10
cui | 3.1.11
disa | CCI-000057, CCI-001133
isa-62443-2009 | 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9
isa-62443-2013 | SR 1.1, SR 1.10, SR 1.2, SR 1.5, SR 1.7, SR 1.8, SR 1.9
iso27001-2013 | A.18.1.4, A.9.2.1, A.9.2.4, A.9.3.1, A.9.4.2, A.9.4.3
nerc-cip | CIP-004-6 R2.2.3, CIP-007-3 R5.1, CIP-007-3 R5.2, CIP-007-3 R5.3.1, CIP-007-3 R5.3.2, CIP-007-3 R5.3.3
nist | AC-12, SC-10, AC-2(5), CM-6(a)
nist-csf | PR.AC-7
os-srg | SRG-OS-000163-GPOS-00072, SRG-OS-000029-GPOS-00010
stigid | UBTU-20-010013
cis | 5.4.5
anssi | R32
pcidss4 | 8.6.1, 8.6
stigref | SV-238207r853404_rule

Remediation Shell script ⇲

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    var_accounts_tmout='900'

    # if 0, no occurence of tmout found, if 1, occurence found
    tmout_found=0

    for f in /etc/bash.bashrc /etc/profile /etc/profile.d/*.sh; do
        if grep --silent '^\s*TMOUT' $f; then
            sed -i -E "s/^(\s*)TMOUT\s*=\s*(\w|\$)*(.*)$/\1TMOUT=$var_accounts_tmout\3/g" $f
            tmout_found=1
            if ! grep --silent '^\s*readonly TMOUT' $f ; then
                echo "readonly TMOUT" >> $f
            fi
            if ! grep --silent '^\s*export TMOUT' $f ; then
                echo "export TMOUT" >> $f
            fi
        fi
    done

    if [ $tmout_found -eq 0 ]; then
            echo -e "\n# Set TMOUT to $var_accounts_tmout per security requirements" >> /etc/profile.d/tmout.sh
            echo "TMOUT=$var_accounts_tmout" >> /etc/profile.d/tmout.sh
            echo "readonly TMOUT" >> /etc/profile.d/tmout.sh
            echo "export TMOUT" >> /etc/profile.d/tmout.sh
    fi

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | restrict

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - DISA-STIG-UBTU-20-010013
      - NIST-800-171-3.1.11
      - NIST-800-53-AC-12
      - NIST-800-53-AC-2(5)
      - NIST-800-53-CM-6(a)
      - NIST-800-53-SC-10
      - PCI-DSSv4-8.6
      - PCI-DSSv4-8.6.1
      - accounts_tmout
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy
    - name: XCCDF Value var_accounts_tmout # promote to variable
      set_fact:
        var_accounts_tmout: !!str 900
      tags:
        - always

    - name: Correct any occurrence of TMOUT in /etc/profile
      replace:
        path: /etc/profile
        regexp: ^[^#].*TMOUT=.*
        replace: typeset -xr TMOUT={{ var_accounts_tmout }}
      register: profile_replaced
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - DISA-STIG-UBTU-20-010013
      - NIST-800-171-3.1.11
      - NIST-800-53-AC-12
      - NIST-800-53-AC-2(5)
      - NIST-800-53-CM-6(a)
      - NIST-800-53-SC-10
      - PCI-DSSv4-8.6
      - PCI-DSSv4-8.6.1
      - accounts_tmout
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy

    - name: Set Interactive Session Timeout
      lineinfile:
        path: /etc/profile.d/tmout.sh
        create: true
        regexp: TMOUT=
        line: typeset -xr TMOUT={{ var_accounts_tmout }}
        state: present
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - DISA-STIG-UBTU-20-010013
      - NIST-800-171-3.1.11
      - NIST-800-53-AC-12
      - NIST-800-53-AC-2(5)
      - NIST-800-53-CM-6(a)
      - NIST-800-53-SC-10
      - PCI-DSSv4-8.6
      - PCI-DSSv4-8.6.1
      - accounts_tmout
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy

#### Rule User Initialization Files Must Be Group-Owned By The Primary Group [ref]

Change the group owner of interactive users files to the group found in

    /etc/passwd

for the user. To change the group owner of a local interactive user home directory, use the following command:

    $ sudo chgrp USER_GROUP /home/USER/.INIT_FILE

This rule ensures every initialization file related to an interactive user is group-owned by an interactive user.
Warning: Due to OVAL limitation, this rule can report a false negative in a specific situation where two interactive users swap the group-ownership of their respective initialization files.

Rationale: | Local initialization files for interactive users are used to configure the user's shell environment upon logon. Malicious modification of these files could compromise accounts upon logon.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_accounts_user_dot_group_ownership

References:

disa | CCI-000366
os-srg | SRG-OS-000480-GPOS-00227
cis | 6.2.7
anssi | R50

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | restrict

    awk -F':' '{ if ($3 >= 1000 && $3 != 65534) system("chgrp -f " $4" "$6"/.[^\.]?*") }' /etc/passwd

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | restrict

    - name: Ensure interactive local users are the group-owners of their respective initialization
        files
      ansible.builtin.command:
        cmd: awk -F':' '{ if ($3 >= 1000 && $3 != 65534) system("chgrp -f " $4" "$6"/.[^\.]?*")
          }' /etc/passwd
      tags:
      - accounts_user_dot_group_ownership
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy

#### Rule User Initialization Files Must Be Owned By the Primary User [ref]

Set the owner of the user initialization files for interactive users to the primary owner with the following command:

    $ sudo chown USER /home/USER/.*

This rule ensures every initialization file related to an interactive user is owned by an interactive user.
Warning: Due to OVAL limitation, this rule can report a false negative in a specific situation where two interactive users swap the ownership of their respective initialization files.

Rationale: | Local initialization files are used to configure the user's shell environment upon logon. Malicious modification of these files could compromise accounts upon logon.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_accounts_user_dot_user_ownership

References:

disa | CCI-000366
os-srg | SRG-OS-000480-GPOS-00227
cis | 6.2.7
anssi | R50

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | restrict

    awk -F':' '{ if ($3 >= 1000 && $3 != 65534) system("chown -f " $3" "$6"/.[^\.]?*") }' /etc/passwd

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | restrict

    - name: Ensure interactive local users are the owners of their respective initialization
        files
      ansible.builtin.command:
        cmd: awk -F':' '{ if ($3 >= 1000 && $3 != 65534) system("chown -f " $3" "$6"/.[^\.]?*")
          }' /etc/passwd
      tags:
      - accounts_user_dot_user_ownership
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy

#### Rule All Interactive Users Home Directories Must Exist [ref]

Create home directories to all local interactive users that currently do not have a home directory assigned. Use the following commands to create the user home directory assigned in `/etc/passwd`:

    $ sudo mkdir /home/USER

Rationale: | If a local interactive user has a home directory defined that does not exist, the user may be given access to the / directory as the current working directory upon logon. This could create a Denial of Service because the user would not be able to access their logon configuration files, and it may give them visibility to system files they normally would not be able to access.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_accounts_user_interactive_home_directory_exists

References:

disa | CCI-000366
os-srg | SRG-OS-000480-GPOS-00227
cis | 6.2.4

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | restrict

    for user in $(awk -F':' '{ if ($3 >= 1000 && $3 != 65534) print $1}' /etc/passwd); do
        mkhomedir_helper $user 0077;
    done

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | restrict

    - name: Get all local users from /etc/passwd
      ansible.builtin.getent:
        database: passwd
        split: ':'
      tags:
      - accounts_user_interactive_home_directory_exists
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy

    - name: Create local_users variable from the getent output
      ansible.builtin.set_fact:
        local_users: '{{ ansible_facts.getent_passwd|dict2items }}'
      tags:
      - accounts_user_interactive_home_directory_exists
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy

    - name: Ensure interactive users have a home directory exists
      ansible.builtin.user:
        name: '{{ item.key }}'
        create_home: true
      loop: '{{ local_users }}'
      when:
      - item.value[2]|int >= 1000
      - item.value[2]|int != 65534
      tags:
      - accounts_user_interactive_home_directory_exists
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy

#### Rule All Interactive User Home Directories Must Be Group-Owned By The Primary Group [ref]

Change the group owner of interactive users home directory to the group found in `/etc/passwd`. To change the group owner of interactive users home directory, use the following command:

    $ sudo chgrp USER_GROUP /home/USER

This rule ensures every home directory related to an interactive user is group-owned by an interactive user. It also ensures that interactive users are group-owners of one and only one home directory.
Warning: Due to OVAL limitation, this rule can report a false negative in a specific situation where two interactive users swap the group-ownership of their respective home directories.

Rationale: | If the Group Identifier (GID) of a local interactive users home directory is not the same as the primary GID of the user, this would allow unauthorized access to the users files, and users that share the same group may not be able to access files that they legitimately should.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_file_groupownership_home_directories

References:

disa | CCI-000366
os-srg | SRG-OS-000480-GPOS-00227
cis | 6.2.6

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | restrict

    awk -F':' '{ if ($3 >= 1000 && $3 != 65534) system("chgrp -f " $4" "$6) }' /etc/passwd

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | restrict

    - name: Get all local users from /etc/passwd
      ansible.builtin.getent:
        database: passwd
        split: ':'
      tags:
      - file_groupownership_home_directories
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy

    - name: Create local_users variable from the getent output
      ansible.builtin.set_fact:
        local_users: '{{ ansible_facts.getent_passwd|dict2items }}'
      tags:
      - file_groupownership_home_directories
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy

    - name: Test for existence of home directories to avoid creating them, but only fixing
        group ownership
      ansible.builtin.stat:
        path: '{{ item.value[4] }}'
      register: path_exists
      loop: '{{ local_users }}'
      when:
      - item.value[1]|int >= 1000
      - item.value[1]|int != 65534
      tags:
      - file_groupownership_home_directories
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy

    - name: Ensure interactive local users are the group-owners of their respective home
        directories
      ansible.builtin.file:
        path: '{{ item.0.value[4] }}'
        group: '{{ item.0.value[2] }}'
      loop: '{{ local_users|zip(path_exists.results)|list }}'
      when: item.1.stat is defined and item.1.stat.exists
      tags:
      - file_groupownership_home_directories
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy

#### Rule All Interactive User Home Directories Must Be Owned By The Primary User [ref]

Change the owner of interactive users home directories to that correct owner. To change the owner of a interactive users home directory, use the following command:

    $ sudo chown USER /home/USER

This rule ensures every home directory related to an interactive user is owned by an interactive user. It also ensures that interactive users are owners of one and only one home directory.
Warning: Due to OVAL limitation, this rule can report a false negative in a specific situation where two interactive users swap the ownership of their respective home directories.

Rationale: | If a local interactive user does not own their home directory, unauthorized users could access or modify the user's files, and the users may not be able to access their own files.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_file_ownership_home_directories

References:

disa | CCI-000366
os-srg | SRG-OS-000480-GPOS-00227
cis | 6.2.6

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | restrict

    awk -F':' '{ if ($3 >= 1000 && $3 != 65534) system("chown -f " $3" "$6) }' /etc/passwd

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | restrict

    - name: Get all local users from /etc/passwd
      ansible.builtin.getent:
        database: passwd
        split: ':'
      tags:
      - file_ownership_home_directories
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy

    - name: Create local_users variable from the getent output
      ansible.builtin.set_fact:
        local_users: '{{ ansible_facts.getent_passwd|dict2items }}'
      tags:
      - file_ownership_home_directories
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy

    - name: Test for existence of home directories to avoid creating them, but only fixing
        ownership
      ansible.builtin.stat:
        path: '{{ item.value[4] }}'
      register: path_exists
      loop: '{{ local_users }}'
      when:
      - item.value[1]|int >= 1000
      - item.value[1]|int != 65534
      tags:
      - file_ownership_home_directories
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy

    - name: Ensure interactive local users are the owners of their respective home directories
      ansible.builtin.file:
        path: '{{ item.0.value[4] }}'
        owner: '{{ item.0.value[1] }}'
      loop: '{{ local_users|zip(path_exists.results)|list }}'
      when: item.1.stat is defined and item.1.stat.exists
      tags:
      - file_ownership_home_directories
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy

#### Rule All Interactive User Home Directories Must Have mode 0750 Or Less Permissive [ref]

Change the mode of interactive users home directories to `0750`. To change the mode of interactive users home directory, use the following command:

    $ sudo chmod 0750 /home/USER

Rationale: | Excessive permissions on local interactive user home directories may allow unauthorized access to user files by other users.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_file_permissions_home_directories

References:

disa | CCI-000366
os-srg | SRG-OS-000480-GPOS-00227
cis | 6.2.5

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | restrict

    for home_dir in $(awk -F':' '{ if ($3 >= 1000 && $3 != 65534 && $6 != "/") print $6 }' /etc/passwd); do
        # Only update the permissions when necessary. This will avoid changing the inode timestamp when
        # the permission is already defined as expected, therefore not impacting in possible integrity
        # check systems that also check inodes timestamps.
        find "$home_dir" -maxdepth 0 -perm /7027 \! -type l -exec chmod u-s,g-w-s,o=- {} \;
    done

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | restrict

    - name: Get all local users from /etc/passwd
      ansible.builtin.getent:
        database: passwd
        split: ':'
      tags:
      - file_permissions_home_directories
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy

    - name: Create local_users variable from the getent output
      ansible.builtin.set_fact:
        local_users: '{{ ansible_facts.getent_passwd|dict2items }}'
      tags:
      - file_permissions_home_directories
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy

    - name: Test for existence home directories to avoid creating them.
      ansible.builtin.stat:
        path: '{{ item.value[4] }}'
      register: path_exists
      loop: '{{ local_users }}'
      when:
      - item.value[1]|int >= 1000
      - item.value[1]|int != 65534
      - item.value[4] != "/"
      tags:
      - file_permissions_home_directories
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy

    - name: Ensure interactive local users have proper permissions on their respective
        home directories
      ansible.builtin.file:
        path: '{{ item.0.value[4] }}'
        mode: u-s,g-w-s,o=-
        follow: false
        recurse: false
      loop: '{{ local_users|zip(path_exists.results)|list }}'
      when: item.1.stat is defined and item.1.stat.exists
      tags:
      - file_permissions_home_directories
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy

Group AppArmor Group contains 3 rules

[ref] Many security vulnerabilities result from bugs in trusted programs. A trusted program runs with privileges that attackers want to possess. The program fails to keep that trust if there is a bug in the program that allows the attacker to acquire said privilege.
AppArmor® is an application security solution designed specifically to apply privilege confinement to suspect programs. AppArmor allows the administrator to specify the domain of activities the program can perform by developing a security profile. A security profile is a listing of files that the program may access and the operations the program may perform. AppArmor secures applications by enforcing good application behavior without relying on attack signatures, so it can prevent attacks even if previously unknown vulnerabilities are being exploited.

#### Rule Ensure AppArmor is installed [ref]

AppArmor provide Mandatory Access Controls.
Rationale: | Without a Mandatory Access Control system installed only the default Discretionary Access Control system will be available.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_package_apparmor_installed

References:

disa | CCI-001764, CCI-001774, CCI-002165, CCI-002235
os-srg | SRG-OS-000368-GPOS-00154, SRG-OS-000312-GPOS-00122, SRG-OS-000312-GPOS-00123, SRG-OS-000312-GPOS-00124, SRG-OS-000324-GPOS-00125, SRG-OS-000370-GPOS-00155
stigid | UBTU-20-010439
cis | 1.7.1.1
anssi | R45
stigref | SV-238360r853435_rule

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | enable

    # Remediation is applicable only in certain platforms
    if [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ]; then

    DEBIAN_FRONTEND=noninteractive apt-get install -y "apparmor"

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation OSBuild Blueprint snippet ⇲

    [[packages]]
    name = "apparmor"
    version = "*"

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | enable

    - name: Ensure apparmor is installed
      package:
        name: apparmor
        state: present
      when: ansible_virtualization_type not in ["docker", "lxc", "openvz", "podman", "container"]
      tags:
      - DISA-STIG-UBTU-20-010439
      - enable_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - package_apparmor_installed

Remediation Puppet snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | enable

    include install_apparmor

    class install_apparmor {
      package { 'apparmor':
        ensure => 'installed',
      }
    }

#### Rule All AppArmor Profiles are in enforce or complain mode [ref]

AppArmor profiles define what resources applications are able to access. To set all profiles to either `enforce` or `complain` mode run the following command to set all profiles to `enforce` mode:

    $ sudo aa-enforce /etc/apparmor.d/*

run the following command to set all profiles to `complain` mode:

    $ sudo aa-complain /etc/apparmor.d/*

To list unconfined processes run the following command:

    $ sudo apparmor_status | grep processes

Any unconfined processes may need to have a profile created or activated for them and then be restarted.

Rationale: | Security configuration requirements vary from site to site. Some sites may mandate a policy that is stricter than the default policy, which is perfectly acceptable. This recommendation is intended to ensure that any policies that exist on the system are activated.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_all_apparmor_profiles_in_enforce_complain_mode

References:

cis | 1.7.1.3

Remediation Shell script ⇲

    # Remediation is applicable only in certain platforms
    if [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ] && { ( [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ] && dpkg-query --show --showformat='${db:Status-Status}\n' 'apparmor' 2>/dev/null | grep -q '^installed' ); }; then

    var_apparmor_mode='enforce'

    # make sure apparmor-utils is installed for aa-complain and aa-enforce
    DEBIAN_FRONTEND=noninteractive apt-get install -y "apparmor-utils"

    # Reload all AppArmor profiles
    apparmor_parser -q -r /etc/apparmor.d/

    # Set the mode
    APPARMOR_MODE="$var_apparmor_mode"

    if [ "$APPARMOR_MODE" = "enforce" ]
    then

      # Set all profiles to enforce mode except disabled profiles
      find /etc/apparmor.d -maxdepth 1 ! -type d -exec bash -c '[[ -e "/etc/apparmor.d/disable/$(basename "$1")" ]] || aa-enforce "$1"' _ {} \;

    fi

    if [ "$APPARMOR_MODE" = "complain" ]
    then

      # Load all not-loaded profiles into complain mode
      apparmor_parser -a --Complain /etc/apparmor.d/
      echo "***WARNING***: This remediation will not downgrade any existing AppArmor profiles."

    fi

    UNCONFINED=$(aa-status | grep "processes are unconfined" | awk '{print $1;}')
    if [ $UNCONFINED -ne 0 ];

    then
      echo -e "***WARNING***: There are some unconfined processes:"
      echo -e "----------------------------"
      echo "The may need to have a profile created or activated for them and then be restarted."
      for PROCESS in "${UNCONFINED[@]}"
      do
          echo "$PROCESS"
      done
      echo -e "----------------------------"
      echo "The may need to have a profile created or activated for them and then be restarted."
    fi

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

#### Rule Ensure AppArmor is enabled in the bootloader configuration [ref]

Configure AppArmor to be enabled at boot time and verify that it has not been overwritten by the bootloader boot parameters. Note: This recommendation is designed around the grub bootloader, if LILO or another bootloader is in use in your environment, enact equivalent settings.
Rationale: | AppArmor must be enabled at boot time in your bootloader configuration to ensure that the controls it provides are not overridden.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_grub2_enable_apparmor

References:

cis | 1.7.1.2
anssi | R45

Remediation Shell script ⇲

    # Remediation is applicable only in certain platforms
    if [ ! -f /.dockerenv ] && [ ! -f /run/.containerenv ]; then

    # Correct the form of default kernel command line in GRUB
    if grep -q '^\s*GRUB_CMDLINE_LINUX=.*apparmor=.*"'  '/etc/default/grub' ; then
           # modify the GRUB command-line if an apparmor= arg already exists
           sed -i "s/\(^\s*GRUB_CMDLINE_LINUX=\".*\)apparmor=[^[:space:]]\+\(.*\"\)/\1apparmor=1\2/"  '/etc/default/grub'
    # Add to already existing GRUB_CMDLINE_LINUX parameters
    elif grep -q '^\s*GRUB_CMDLINE_LINUX='  '/etc/default/grub' ; then
           # no apparmor=arg is present, append it
           sed -i "s/\(^\s*GRUB_CMDLINE_LINUX=\".*\)\"/\1 apparmor=1\"/"  '/etc/default/grub'
    # Add GRUB_CMDLINE_LINUX parameters line
    else
           echo "GRUB_CMDLINE_LINUX=\"apparmor=1\"" >> '/etc/default/grub'
    fi
    # Correct the form of default kernel command line in GRUB
    if grep -q '^\s*GRUB_CMDLINE_LINUX=.*security=.*"'  '/etc/default/grub' ; then
           # modify the GRUB command-line if an security= arg already exists
           sed -i "s/\(^\s*GRUB_CMDLINE_LINUX=\".*\)security=[^[:space:]]\+\(.*\"\)/\1security=apparmor\2/"  '/etc/default/grub'
    # Add to already existing GRUB_CMDLINE_LINUX parameters
    elif grep -q '^\s*GRUB_CMDLINE_LINUX='  '/etc/default/grub' ; then
           # no security=arg is present, append it
           sed -i "s/\(^\s*GRUB_CMDLINE_LINUX=\".*\)\"/\1 security=apparmor\"/"  '/etc/default/grub'
    # Add GRUB_CMDLINE_LINUX parameters line
    else
           echo "GRUB_CMDLINE_LINUX=\"security=apparmor\"" >> '/etc/default/grub'
    fi

    update-grub

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Group GRUB2 bootloader configuration Group contains 2 groups and 4 rules

[ref] During the boot process, the boot loader is responsible for starting the execution of the kernel and passing options to it. The boot loader allows for the selection of different kernels - possibly on different partitions or media. The default Ubuntu 20.04 boot loader for x86 systems is called GRUB2. Options it can pass to the kernel include single-user mode, which provides root access without any authentication, and the ability to disable SELinux. To prevent local users from modifying the boot parameters and endangering security, protect the boot loader configuration with a password and ensure its configuration file's permissions are set properly.

Group Non-UEFI GRUB2 bootloader configuration Group contains 3 rules
[ref] Non-UEFI GRUB2 bootloader configuration

#### Rule Verify /boot/grub/grub.cfg User Ownership [ref]

The file `/boot/grub/grub.cfg` should be owned by the `root` user to prevent destruction or modification of the file. To properly set the owner of `/boot/grub/grub.cfg`, run the command:

    $ sudo chown root /boot/grub/grub.cfg

Rationale: | Only root should be able to modify important boot parameters.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_file_owner_grub2_cfg

References:

cis-csc | 12, 13, 14, 15, 16, 18, 3, 5
cjis | 5.5.2.2
cobit5 | APO01.06, DSS05.04, DSS05.07, DSS06.02
cui | 3.4.5
disa | CCI-000366
hipaa | 164.308(a)(1)(ii)(B), 164.308(a)(7)(i), 164.308(a)(7)(ii)(A), 164.310(a)(1), 164.310(a)(2)(i), 164.310(a)(2)(ii), 164.310(a)(2)(iii), 164.310(b), 164.310(c), 164.310(d)(1), 164.310(d)(2)(iii)
isa-62443-2009 | 4.3.3.7.3
isa-62443-2013 | SR 2.1, SR 5.2
iso27001-2013 | A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.13.1.1, A.13.1.3, A.13.2.1, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, A.6.1.2, A.7.1.1, A.7.1.2, A.7.3.1, A.8.2.2, A.8.2.3, A.9.1.1, A.9.1.2, A.9.2.3, A.9.4.1, A.9.4.4, A.9.4.5
nist | CM-6(a), AC-6(1)
nist-csf | PR.AC-4, PR.DS-5
pcidss | Req-7.1
os-srg | SRG-OS-000480-GPOS-00227
cis | 1.5.2
anssi | R29
pcidss4 | 2.2.6, 2.2

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    # Remediation is applicable only in certain platforms
    if ( dpkg-query --show --showformat='${db:Status-Status}\n' 'grub2-common' 2>/dev/null | grep -q '^installed' && dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed ) && [ ! -d /sys/firmware/efi ] && { ! ( [ -f /.dockerenv ] || [ -f /run/.containerenv ] ); }; then

    chown 0 /boot/grub/grub.cfg

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - CJIS-5.5.2.2
      - NIST-800-171-3.4.5
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - PCI-DSS-Req-7.1
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_owner_grub2_cfg
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Test for existence /boot/grub/grub.cfg
      stat:
        path: /boot/grub/grub.cfg
      register: file_exists
      when:
      - '"/boot/efi" not in ansible_mounts | map(attribute="mount") | list'
      - ( "grub2-common" in ansible_facts.packages and "linux-base" in ansible_facts.packages
        )
      - not ( ansible_virtualization_type in ["docker", "lxc", "openvz", "podman", "container"]
        )
      tags:
      - CJIS-5.5.2.2
      - NIST-800-171-3.4.5
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - PCI-DSS-Req-7.1
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_owner_grub2_cfg
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Ensure owner 0 on /boot/grub/grub.cfg
      file:
        path: /boot/grub/grub.cfg
        owner: '0'
      when:
      - '"/boot/efi" not in ansible_mounts | map(attribute="mount") | list'
      - ( "grub2-common" in ansible_facts.packages and "linux-base" in ansible_facts.packages
        )
      - not ( ansible_virtualization_type in ["docker", "lxc", "openvz", "podman", "container"]
        )
      - file_exists.stat is defined and file_exists.stat.exists
      tags:
      - CJIS-5.5.2.2
      - NIST-800-171-3.4.5
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - PCI-DSS-Req-7.1
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_owner_grub2_cfg
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

#### Rule Verify /boot/grub/grub.cfg Permissions [ref]

File permissions for `/boot/grub/grub.cfg` should be set to 600. To properly set the permissions of `/boot/grub/grub.cfg`, run the command:

    $ sudo chmod 600 /boot/grub/grub.cfg

Rationale: | Proper permissions ensure that only the root user can modify important boot parameters.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_file_permissions_grub2_cfg

References:

cis-csc | 12, 13, 14, 15, 16, 18, 3, 5
cobit5 | APO01.06, DSS05.04, DSS05.07, DSS06.02
cui | 3.4.5
disa | CCI-000225
hipaa | 164.308(a)(1)(ii)(B), 164.308(a)(7)(i), 164.308(a)(7)(ii)(A), 164.310(a)(1), 164.310(a)(2)(i), 164.310(a)(2)(ii), 164.310(a)(2)(iii), 164.310(b), 164.310(c), 164.310(d)(1), 164.310(d)(2)(iii)
isa-62443-2009 | 4.3.3.7.3
isa-62443-2013 | SR 2.1, SR 5.2
iso27001-2013 | A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.13.1.1, A.13.1.3, A.13.2.1, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, A.6.1.2, A.7.1.1, A.7.1.2, A.7.3.1, A.8.2.2, A.8.2.3, A.9.1.1, A.9.1.2, A.9.2.3, A.9.4.1, A.9.4.4, A.9.4.5
nist | CM-6(a), AC-6(1)
nist-csf | PR.AC-4, PR.DS-5
cis | 1.5.2
anssi | R29
pcidss4 | 2.2.6, 2.2

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    # Remediation is applicable only in certain platforms
    if ( dpkg-query --show --showformat='${db:Status-Status}\n' 'grub2-common' 2>/dev/null | grep -q '^installed' && dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed ) && [ ! -d /sys/firmware/efi ] && { ! ( [ -f /.dockerenv ] || [ -f /run/.containerenv ] ); }; then

    chmod u-xs,g-xwrs,o-xwrt /boot/grub/grub.cfg

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - NIST-800-171-3.4.5
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_permissions_grub2_cfg
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Test for existence /boot/grub/grub.cfg
      stat:
        path: /boot/grub/grub.cfg
      register: file_exists
      when:
      - '"/boot/efi" not in ansible_mounts | map(attribute="mount") | list'
      - ( "grub2-common" in ansible_facts.packages and "linux-base" in ansible_facts.packages
        )
      - not ( ansible_virtualization_type in ["docker", "lxc", "openvz", "podman", "container"]
        )
      tags:
      - NIST-800-171-3.4.5
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_permissions_grub2_cfg
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Ensure permission u-xs,g-xwrs,o-xwrt on /boot/grub/grub.cfg
      file:
        path: /boot/grub/grub.cfg
        mode: u-xs,g-xwrs,o-xwrt
      when:
      - '"/boot/efi" not in ansible_mounts | map(attribute="mount") | list'
      - ( "grub2-common" in ansible_facts.packages and "linux-base" in ansible_facts.packages
        )
      - not ( ansible_virtualization_type in ["docker", "lxc", "openvz", "podman", "container"]
        )
      - file_exists.stat is defined and file_exists.stat.exists
      tags:
      - NIST-800-171-3.4.5
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_permissions_grub2_cfg
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

#### Rule Set Boot Loader Password in grub2 [ref]

The grub2 boot loader should have a superuser account and password protection enabled to protect boot-time settings.
Since plaintext passwords are a security risk, generate a hash for the password by running the following command:

    # grub2-mkpasswd-pbkdf2

When prompted, enter the password that was selected.
Using the hash from the output, modify the `/etc/grub.d/40_custom` file with the following content:

    set superusers="boot"
    password_pbkdf2 boot grub.pbkdf2.sha512.VeryLongString

NOTE: the bootloader superuser account and password MUST differ from the root account and password. Once the superuser password has been added, update the `grub.cfg` file by running:

    update-grub

Warning: To prevent hard-coded passwords, automatic remediation of this control is not available. Remediation must be automated as a component of machine provisioning, or followed manually as outlined above. Also, do NOT manually add the superuser account and password to the `grub.cfg` file as the grub2-mkconfig command overwrites this file.

Rationale: | Password protection on the boot loader configuration ensures users with physical access cannot trivially alter important bootloader settings. These include which kernel to use, and whether to enter single-user mode.
Severity: | high
Rule ID: | xccdf_org.ssgproject.content_rule_grub2_password

References:

cis-csc | 1, 11, 12, 14, 15, 16, 18, 3, 5
cobit5 | DSS05.02, DSS05.04, DSS05.05, DSS05.07, DSS05.10, DSS06.03, DSS06.06, DSS06.10
cui | 3.4.5
disa | CCI-000213
hipaa | 164.308(a)(1)(ii)(B), 164.308(a)(7)(i), 164.308(a)(7)(ii)(A), 164.310(a)(1), 164.310(a)(2)(i), 164.310(a)(2)(ii), 164.310(a)(2)(iii), 164.310(b), 164.310(c), 164.310(d)(1), 164.310(d)(2)(iii)
isa-62443-2009 | 4.3.3.2.2, 4.3.3.5.1, 4.3.3.5.2, 4.3.3.5.3, 4.3.3.5.4, 4.3.3.5.5, 4.3.3.5.6, 4.3.3.5.7, 4.3.3.5.8, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.1, 4.3.3.7.2, 4.3.3.7.3, 4.3.3.7.4
isa-62443-2013 | SR 1.1, SR 1.10, SR 1.11, SR 1.12, SR 1.13, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.6, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 2.2, SR 2.3, SR 2.4, SR 2.5, SR 2.6, SR 2.7
iso27001-2013 | A.18.1.4, A.6.1.2, A.7.1.1, A.9.1.2, A.9.2.1, A.9.2.2, A.9.2.3, A.9.2.4, A.9.2.6, A.9.3.1, A.9.4.1, A.9.4.2, A.9.4.3, A.9.4.4, A.9.4.5
nist | CM-6(a)
nist-csf | PR.AC-1, PR.AC-4, PR.AC-6, PR.AC-7, PR.PT-3
os-srg | SRG-OS-000080-GPOS-00048
stigid | UBTU-20-010009
cis | 1.5.1
anssi | R5
stigref | SV-238204r832936_rule

Group UEFI GRUB2 bootloader configuration Group contains 1 rule
[ref] UEFI GRUB2 bootloader configuration Warning: UEFI generally uses vfat file systems, which does not support Unix-style permissions managed by chmod command. In this case, in order to change file permissions for files within /boot/efi it is necessary to update the mount options in /etc/fstab file and reboot the system.

#### Rule Set the UEFI Boot Loader Password [ref]

The grub2 boot loader should have a superuser account and password protection enabled to protect boot-time settings.
Since plaintext passwords are a security risk, generate a hash for the password by running the following command:

    # grub2-mkpasswd-pbkdf2

When prompted, enter the password that was selected.
Using the hash from the output, modify the `/etc/grub.d/40_custom` file with the following content:

    set superusers="boot"
    password_pbkdf2 boot grub.pbkdf2.sha512.VeryLongString

NOTE: the bootloader superuser account and password MUST differ from the root account and password. Once the superuser password has been added, update the `grub.cfg` file by running:

    update-grub

Warning: To prevent hard-coded passwords, automatic remediation of this control is not available. Remediation must be automated as a component of machine provisioning, or followed manually as outlined above. Also, do NOT manually add the superuser account and password to the `grub.cfg` file as the grub2-mkconfig command overwrites this file.

Rationale: | Password protection on the boot loader configuration ensures users with physical access cannot trivially alter important bootloader settings. These include which kernel to use, and whether to enter single-user mode.
Severity: | high
Rule ID: | xccdf_org.ssgproject.content_rule_grub2_uefi_password

References:

cis-csc | 11, 12, 14, 15, 16, 18, 3, 5
cobit5 | DSS05.02, DSS05.04, DSS05.05, DSS05.07, DSS06.03, DSS06.06
cui | 3.4.5
disa | CCI-000213
hipaa | 164.308(a)(1)(ii)(B), 164.308(a)(7)(i), 164.308(a)(7)(ii)(A), 164.310(a)(1), 164.310(a)(2)(i), 164.310(a)(2)(ii), 164.310(a)(2)(iii), 164.310(b), 164.310(c), 164.310(d)(1), 164.310(d)(2)(iii)
isa-62443-2009 | 4.3.3.2.2, 4.3.3.5.1, 4.3.3.5.2, 4.3.3.5.3, 4.3.3.5.4, 4.3.3.5.5, 4.3.3.5.6, 4.3.3.5.7, 4.3.3.5.8, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.1, 4.3.3.7.2, 4.3.3.7.3, 4.3.3.7.4
isa-62443-2013 | SR 1.1, SR 1.10, SR 1.11, SR 1.12, SR 1.13, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.6, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 2.2, SR 2.3, SR 2.4, SR 2.5, SR 2.6, SR 2.7
iso27001-2013 | A.6.1.2, A.7.1.1, A.9.1.2, A.9.2.1, A.9.2.3, A.9.4.1, A.9.4.4, A.9.4.5
nist | CM-6(a)
nist-csf | PR.AC-4, PR.AC-6, PR.PT-3
ospp | FIA_UAU.1
os-srg | SRG-OS-000080-GPOS-00048
stigid | UBTU-20-010009
cis | 1.5.1
anssi | R5
stigref | SV-238204r832936_rule

Group Configure Syslog Group contains 2 groups and 7 rules

[ref] The syslog service has been the default Unix logging mechanism for many years. It has a number of downsides, including inconsistent log format, lack of authentication for received messages, and lack of authentication, encryption, or reliable transport for messages sent over a network. However, due to its long history, syslog is a de facto standard which is supported by almost all Unix applications.
In Ubuntu 20.04, rsyslog has replaced ksyslogd as the syslog daemon of choice, and it includes some additional security features such as reliable, connection-oriented (i.e. TCP) transmission of logs, the option to log to database formats, and the encryption of log data en route to a central logging server. This section discusses how to configure rsyslog for best effect, and how to use tools provided with the system to maintain and monitor logs.

Group systemd-journald Group contains 3 rules
[ref] systemd-journald is a system service that collects and stores logging data. It creates and maintains structured, indexed journals based on logging information that is received from a variety of sources. For more information on `systemd-journald` and additional `systemd-journald` configuration options, see https://systemd.io/.

#### Rule Ensure journald is configured to compress large log files [ref]

The journald system can compress large log files to avoid fill the system disk.
Rationale: | Log files that are not properly compressed run the risk of growing so large that they fill up the log partition. Valuable logging information could be lost if the log partition becomes full.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_journald_compress

References:

cis | 4.2.2.2

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | restrict

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    if [ -e "/etc/systemd/journald.conf" ] ; then

        LC_ALL=C sed -i "/^\s*Compress\s*=\s*/d" "/etc/systemd/journald.conf"
    else
        touch "/etc/systemd/journald.conf"
    fi
    # make sure file has newline at the end
    sed -i -e '$a\' "/etc/systemd/journald.conf"

    cp "/etc/systemd/journald.conf" "/etc/systemd/journald.conf.bak"
    # Insert before the line matching the regex '^#\s*Compress'.
    line_number="$(LC_ALL=C grep -n "^#\s*Compress" "/etc/systemd/journald.conf.bak" | LC_ALL=C sed 's/:.*//g')"
    if [ -z "$line_number" ]; then
        # There was no match of '^#\s*Compress', insert at
        # the end of the file.
        printf '%s\n' "Compress=yes" >> "/etc/systemd/journald.conf"
    else
        head -n "$(( line_number - 1 ))" "/etc/systemd/journald.conf.bak" > "/etc/systemd/journald.conf"
        printf '%s\n' "Compress=yes" >> "/etc/systemd/journald.conf"
        tail -n "+$(( line_number ))" "/etc/systemd/journald.conf.bak" >> "/etc/systemd/journald.conf"
    fi
    # Clean up after ourselves.
    rm "/etc/systemd/journald.conf.bak"

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | restrict

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - journald_compress
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy

    - name: Setting unquoted shell-style assignment of 'Compress' to 'yes' in '/etc/systemd/journald.conf'
      block:

      - name: Check for duplicate values
        lineinfile:
          path: /etc/systemd/journald.conf
          create: true
          regexp: (?i)^\s*Compress=
          state: absent
        check_mode: true
        changed_when: false
        register: dupes

      - name: Deduplicate values from /etc/systemd/journald.conf
        lineinfile:
          path: /etc/systemd/journald.conf
          create: true
          regexp: (?i)^\s*Compress=
          state: absent
        when: dupes.found is defined and dupes.found > 1

      - name: Insert correct line to /etc/systemd/journald.conf
        lineinfile:
          path: /etc/systemd/journald.conf
          create: true
          regexp: (?i)^\s*Compress=
          line: Compress=yes
          state: present
          insertbefore: ^# Compress
          validate: /usr/bin/bash -n %s
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - journald_compress
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy

#### Rule Ensure journald is configured to send logs to rsyslog [ref]

Data from journald may be stored in volatile memory or persisted locally. Utilities exist to accept remote export of journald logs.
Rationale: | Storing log data on a remote host protects log integrity from local attacks. If an attacker gains root access on the local system, they could tamper with or remove log data that is stored on the local system.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_journald_forward_to_syslog

References:

cis | 4.2.2.1

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | restrict

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    if [ -e "/etc/systemd/journald.conf" ] ; then

        LC_ALL=C sed -i "/^\s*ForwardToSyslog\s*=\s*/d" "/etc/systemd/journald.conf"
    else
        touch "/etc/systemd/journald.conf"
    fi
    # make sure file has newline at the end
    sed -i -e '$a\' "/etc/systemd/journald.conf"

    cp "/etc/systemd/journald.conf" "/etc/systemd/journald.conf.bak"
    # Insert before the line matching the regex '^#\s*ForwardToSyslog'.
    line_number="$(LC_ALL=C grep -n "^#\s*ForwardToSyslog" "/etc/systemd/journald.conf.bak" | LC_ALL=C sed 's/:.*//g')"
    if [ -z "$line_number" ]; then
        # There was no match of '^#\s*ForwardToSyslog', insert at
        # the end of the file.
        printf '%s\n' "ForwardToSyslog=yes" >> "/etc/systemd/journald.conf"
    else
        head -n "$(( line_number - 1 ))" "/etc/systemd/journald.conf.bak" > "/etc/systemd/journald.conf"
        printf '%s\n' "ForwardToSyslog=yes" >> "/etc/systemd/journald.conf"
        tail -n "+$(( line_number ))" "/etc/systemd/journald.conf.bak" >> "/etc/systemd/journald.conf"
    fi
    # Clean up after ourselves.
    rm "/etc/systemd/journald.conf.bak"

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | restrict

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - journald_forward_to_syslog
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy

    - name: Setting unquoted shell-style assignment of 'ForwardToSyslog' to 'yes' in '/etc/systemd/journald.conf'
      block:

      - name: Check for duplicate values
        lineinfile:
          path: /etc/systemd/journald.conf
          create: true
          regexp: (?i)^\s*ForwardToSyslog=
          state: absent
        check_mode: true
        changed_when: false
        register: dupes

      - name: Deduplicate values from /etc/systemd/journald.conf
        lineinfile:
          path: /etc/systemd/journald.conf
          create: true
          regexp: (?i)^\s*ForwardToSyslog=
          state: absent
        when: dupes.found is defined and dupes.found > 1

      - name: Insert correct line to /etc/systemd/journald.conf
        lineinfile:
          path: /etc/systemd/journald.conf
          create: true
          regexp: (?i)^\s*ForwardToSyslog=
          line: ForwardToSyslog=yes
          state: present
          insertbefore: ^# ForwardToSyslog
          validate: /usr/bin/bash -n %s
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - journald_forward_to_syslog
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy

#### Rule Ensure journald is configured to write log files to persistent disk [ref]

The journald system may store log files in volatile memory or locally on disk. If the logs are only stored in volatile memory they will we lost upon reboot.
Rationale: | Log files contain valuable data and need to be persistent to aid in possible investigations.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_journald_storage

References:

cis | 4.2.2.3

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | restrict

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    if [ -e "/etc/systemd/journald.conf" ] ; then

        LC_ALL=C sed -i "/^\s*Storage\s*=\s*/d" "/etc/systemd/journald.conf"
    else
        touch "/etc/systemd/journald.conf"
    fi
    # make sure file has newline at the end
    sed -i -e '$a\' "/etc/systemd/journald.conf"

    cp "/etc/systemd/journald.conf" "/etc/systemd/journald.conf.bak"
    # Insert before the line matching the regex '^#\s*Storage'.
    line_number="$(LC_ALL=C grep -n "^#\s*Storage" "/etc/systemd/journald.conf.bak" | LC_ALL=C sed 's/:.*//g')"
    if [ -z "$line_number" ]; then
        # There was no match of '^#\s*Storage', insert at
        # the end of the file.
        printf '%s\n' "Storage=persistent" >> "/etc/systemd/journald.conf"
    else
        head -n "$(( line_number - 1 ))" "/etc/systemd/journald.conf.bak" > "/etc/systemd/journald.conf"
        printf '%s\n' "Storage=persistent" >> "/etc/systemd/journald.conf"
        tail -n "+$(( line_number ))" "/etc/systemd/journald.conf.bak" >> "/etc/systemd/journald.conf"
    fi
    # Clean up after ourselves.
    rm "/etc/systemd/journald.conf.bak"

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | restrict

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - journald_storage
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy

    - name: Setting unquoted shell-style assignment of 'Storage' to 'persistent' in '/etc/systemd/journald.conf'
      block:

      - name: Check for duplicate values
        lineinfile:
          path: /etc/systemd/journald.conf
          create: true
          regexp: (?i)^\s*Storage=
          state: absent
        check_mode: true
        changed_when: false
        register: dupes

      - name: Deduplicate values from /etc/systemd/journald.conf
        lineinfile:
          path: /etc/systemd/journald.conf
          create: true
          regexp: (?i)^\s*Storage=
          state: absent
        when: dupes.found is defined and dupes.found > 1

      - name: Insert correct line to /etc/systemd/journald.conf
        lineinfile:
          path: /etc/systemd/journald.conf
          create: true
          regexp: (?i)^\s*Storage=
          line: Storage=persistent
          state: present
          insertbefore: ^# Storage
          validate: /usr/bin/bash -n %s
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - journald_storage
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy

Group Rsyslog Logs Sent To Remote Host Group contains 1 rule

[ref] If system logs are to be useful in detecting malicious activities, it is necessary to send logs to a remote server. An intruder who has compromised the root account on a system may delete the log entries which indicate that the system was attacked before they are seen by an administrator.
However, it is recommended that logs be stored on the local host in addition to being sent to the loghost, especially if `rsyslog` has been configured to use the UDP protocol to send messages over a network. UDP does not guarantee reliable delivery, and moderately busy sites will lose log messages occasionally, especially in periods of high traffic which may be the result of an attack. In addition, remote `rsyslog` messages are not authenticated in any way by default, so it is easy for an attacker to introduce spurious messages to the central log server. Also, some problems cause loss of network connectivity, which will prevent the sending of messages to the central server. For all of these reasons, it is better to store log messages both centrally and on each host, so that they can be correlated if necessary.

#### Rule Ensure Logs Sent To Remote Host [ref]

To configure rsyslog to send logs to a remote log server, open `/etc/rsyslog.conf` and read and understand the last section of the file, which describes the multiple directives necessary to activate remote logging. Along with these other directives, the system can be configured to forward its logs to a particular log server by adding or correcting one of the following lines, substituting `logcollector` appropriately. The choice of protocol depends on the environment of the system; although TCP and RELP provide more reliable message delivery, they may not be supported in all environments.
To use UDP for log message delivery:

    *.* @logcollector

To use TCP for log message delivery:

    *.* @@logcollector

To use RELP for log message delivery:

    *.* :omrelp:logcollector

There must be a resolvable DNS CNAME or Alias record set to "logcollector" for logs to be sent correctly to the centralized logging utility.
Warning: It is important to configure queues in case the client is sending log messages to a remote server. If queues are not configured, the system will stop functioning when the connection to the remote server is not available. Please consult Rsyslog documentation for more information about configuration of queues. The example configuration which should go into `/etc/rsyslog.conf` can look like the following lines:

    $ActionQueueType LinkedList
    $ActionQueueFileName queuefilename
    $ActionQueueMaxDiskSpace 1g
    $ActionQueueSaveOnShutdown on
    $ActionResumeRetryCount -1

Rationale: | A log server (loghost) receives syslog messages from one or more systems. This data can be used as an additional log source in the event a system is compromised and its local logs are suspect. Forwarding log messages to a remote loghost also provides system administrators with a centralized place to view the status of multiple hosts within the enterprise.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_rsyslog_remote_loghost

References:

cis-csc | 1, 13, 14, 15, 16, 2, 3, 5, 6
cobit5 | APO11.04, APO13.01, BAI03.05, BAI04.04, DSS05.04, DSS05.07, MEA02.01
disa | CCI-000366, CCI-001851
hipaa | 164.308(a)(1)(ii)(D), 164.308(a)(5)(ii)(B), 164.308(a)(5)(ii)(C), 164.308(a)(6)(ii), 164.308(a)(8), 164.310(d)(2)(iii), 164.312(b), 164.314(a)(2)(i)(C), 164.314(a)(2)(iii)
isa-62443-2009 | 4.3.3.3.9, 4.3.3.5.8, 4.3.4.4.7, 4.4.2.1, 4.4.2.2, 4.4.2.4
isa-62443-2013 | SR 2.10, SR 2.11, SR 2.12, SR 2.8, SR 2.9, SR 7.1, SR 7.2
ism | 0988, 1405
iso27001-2013 | A.12.1.3, A.12.4.1, A.12.4.2, A.12.4.3, A.12.4.4, A.12.7.1, A.17.2.1
nerc-cip | CIP-003-8 R5.2, CIP-004-6 R3.3
nist | CM-6(a), AU-4(1), AU-9(2)
nist-csf | PR.DS-4, PR.PT-1
os-srg | SRG-OS-000479-GPOS-00224, SRG-OS-000480-GPOS-00227, SRG-OS-000342-GPOS-00133
cis | 4.2.1.5
anssi | R71

Remediation Shell script ⇲

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    rsyslog_remote_loghost_address='logcollector'

    # Strip any search characters in the key arg so that the key can be replaced without
    # adding any search characters to the config file.
    stripped_key=$(sed 's/[\^=\$,;+]*//g' <<< "^\*\.\*")

    # shellcheck disable=SC2059
    printf -v formatted_output "%s %s" "$stripped_key" "@@$rsyslog_remote_loghost_address"

    # If the key exists, change it. Otherwise, add it to the config_file.
    # We search for the key string followed by a word boundary (matched by \>),
    # so if we search for 'setting', 'setting2' won't match.
    if LC_ALL=C grep -q -m 1 -i -e "^\*\.\*\\>" "/etc/rsyslog.conf"; then
        escaped_formatted_output=$(sed -e 's|/|\\/|g' <<< "$formatted_output")
        LC_ALL=C sed -i --follow-symlinks "s/^\*\.\*\\>.*/$escaped_formatted_output/gi" "/etc/rsyslog.conf"
    else
        if [[ -s "/etc/rsyslog.conf" ]] && [[ -n "$(tail -c 1 -- "/etc/rsyslog.conf" || true)" ]]; then
            LC_ALL=C sed -i --follow-symlinks '$a'\\ "/etc/rsyslog.conf"
        fi
        printf '%s\n' "$formatted_output" >> "/etc/rsyslog.conf"
    fi

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

#### Rule Ensure rsyslog is Installed [ref]

Rsyslog is installed by default. The `rsyslog` package can be installed with the following command:

     $ apt-get install rsyslog

Rationale: | The rsyslog package provides the rsyslog daemon, which provides system logging services.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_package_rsyslog_installed

References:

cis-csc | 1, 14, 15, 16, 3, 5, 6
cobit5 | APO11.04, BAI03.05, DSS05.04, DSS05.07, MEA02.01
disa | CCI-000366, CCI-000154, CCI-001851
hipaa | 164.312(a)(2)(ii)
isa-62443-2009 | 4.3.3.3.9, 4.3.3.5.8, 4.3.4.4.7, 4.4.2.1, 4.4.2.2, 4.4.2.4
isa-62443-2013 | SR 2.10, SR 2.11, SR 2.12, SR 2.8, SR 2.9
iso27001-2013 | A.12.4.1, A.12.4.2, A.12.4.3, A.12.4.4, A.12.7.1
nist | CM-6(a)
nist-csf | PR.PT-1
os-srg | SRG-OS-000479-GPOS-00224, SRG-OS-000051-GPOS-00024, SRG-OS-000480-GPOS-00227
cis | 4.2.1.1

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | enable

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    DEBIAN_FRONTEND=noninteractive apt-get install -y "rsyslog"

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation OSBuild Blueprint snippet ⇲

    [[packages]]
    name = "rsyslog"
    version = "*"

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | enable

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - NIST-800-53-CM-6(a)
      - enable_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - package_rsyslog_installed

    - name: Ensure rsyslog is installed
      package:
        name: rsyslog
        state: present
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-53-CM-6(a)
      - enable_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - package_rsyslog_installed

Remediation Puppet snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | enable

    include install_rsyslog

    class install_rsyslog {
      package { 'rsyslog':
        ensure => 'installed',
      }
    }

#### Rule Enable rsyslog Service [ref]

The `rsyslog` service provides syslog-style logging by default on Ubuntu 20.04. The `rsyslog` service can be enabled with the following command:

    $ sudo systemctl enable rsyslog.service

Rationale: | The `rsyslog` service must be running in order to provide logging services, which are essential to system administration.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_service_rsyslog_enabled

References:

cis-csc | 1, 12, 13, 14, 15, 16, 2, 3, 5, 6, 7, 8, 9
cobit5 | APO10.01, APO10.03, APO10.04, APO10.05, APO11.04, APO13.01, BAI03.05, BAI04.04, DSS01.03, DSS03.05, DSS05.02, DSS05.04, DSS05.05, DSS05.07, MEA01.01, MEA01.02, MEA01.03, MEA01.04, MEA01.05, MEA02.01
disa | CCI-000366
hipaa | 164.312(a)(2)(ii)
isa-62443-2009 | 4.3.2.6.7, 4.3.3.3.9, 4.3.3.5.8, 4.3.4.4.7, 4.4.2.1, 4.4.2.2, 4.4.2.4
isa-62443-2013 | SR 2.10, SR 2.11, SR 2.12, SR 2.8, SR 2.9, SR 6.1, SR 6.2, SR 7.1, SR 7.2
iso27001-2013 | A.12.1.3, A.12.4.1, A.12.4.2, A.12.4.3, A.12.4.4, A.12.7.1, A.14.2.7, A.15.2.1, A.15.2.2, A.17.2.1
nist | CM-6(a), AU-4(1)
nist-csf | DE.CM-1, DE.CM-3, DE.CM-7, ID.SC-4, PR.DS-4, PR.PT-1
os-srg | SRG-OS-000480-GPOS-00227
stigid | UBTU-20-010432
cis | 4.2.1.2
stigref | SV-238353r654234_rule

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | enable

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    SYSTEMCTL_EXEC='/usr/bin/systemctl'
    "$SYSTEMCTL_EXEC" unmask 'rsyslog.service'
    if [[ $("$SYSTEMCTL_EXEC" is-system-running) != "offline" ]]; then
      "$SYSTEMCTL_EXEC" start 'rsyslog.service'
    fi
    "$SYSTEMCTL_EXEC" enable 'rsyslog.service'

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation OSBuild Blueprint snippet ⇲

    [customizations.services]
    enabled = ["rsyslog"]

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | enable

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - DISA-STIG-UBTU-20-010432
      - NIST-800-53-AU-4(1)
      - NIST-800-53-CM-6(a)
      - enable_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - service_rsyslog_enabled

    - name: Enable rsyslog Service - Enable service rsyslog
      block:

      - name: Gather the package facts
        package_facts:
          manager: auto

      - name: Enable rsyslog Service - Enable Service rsyslog
        ansible.builtin.systemd:
          name: rsyslog
          enabled: true
          state: started
          masked: false
        when:
        - '"rsyslog" in ansible_facts.packages'
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - DISA-STIG-UBTU-20-010432
      - NIST-800-53-AU-4(1)
      - NIST-800-53-CM-6(a)
      - enable_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - service_rsyslog_enabled

Remediation Puppet snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | enable

    include enable_rsyslog

    class enable_rsyslog {
      service {'rsyslog':
        enable => true,
        ensure => 'running',
      }
    }

#### Rule Ensure rsyslog Default File Permissions Configured [ref]

rsyslog will create logfiles that do not already exist on the system. This settings controls what permissions will be applied to these newly created files.
Rationale: | It is important to ensure that log files have the correct permissions to ensure that sensitive data is archived and protected.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_rsyslog_filecreatemode

References:

cis | 4.2.1.4

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    readarray -t targets < <(grep -H '^\s*$FileCreateMode' /etc/rsyslog.conf /etc/rsyslog.d/*)

    # if $FileCreateMode set in multiple places
    if [ ${#targets[@]} -gt 1 ]; then
        # delete all and create new entry with expected value
        sed -i '/^\s*$FileCreateMode/d' /etc/rsyslog.conf /etc/rsyslog.d/*
        echo '$FileCreateMode 0640' > /etc/rsyslog.d/99-rsyslog_filecreatemode.conf
    # if $FileCreateMode set in only one place
    elif [ "${#targets[@]}" -eq 1 ]; then
        filename=$(echo "${targets[0]}" | cut -d':' -f1)
        value=$(echo "${targets[0]}" | cut -d' ' -f2)
        #convert to decimal and bitwise or operation
        result=$((8#$value | 416))
        # if more permissive than expected, then set it to 0640
        if [ $result -ne 416 ]; then
            # if value is wrong remove it
            sed -i '/^\s*$FileCreateMode/d' $filename
            echo '$FileCreateMode 0640' > $filename
        fi
    else
        echo '$FileCreateMode 0640' > /etc/rsyslog.d/99-rsyslog_filecreatemode.conf
    fi

    systemctl restart rsyslog.service

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - configure_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - rsyslog_filecreatemode

    - name: Ensure rsyslog Default File Permissions Configured - Search for $FileCreateMode
        Parameter in rsyslog Main Config File
      ansible.builtin.find:
        paths: /etc
        pattern: rsyslog.conf
        contains: ^\s*\$FileCreateMode\s*\d+
      register: rsyslog_main_file_with_filecreatemode
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - configure_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - rsyslog_filecreatemode

    - name: Ensure rsyslog Default File Permissions Configured - Search for $FileCreateMode
        Parameter in rsyslog Include Files
      ansible.builtin.find:
        paths: /etc/rsyslog.d/
        pattern: '*.conf'
        contains: ^\s*\$FileCreateMode\s*\d+
      register: rsyslog_includes_with_filecreatemode
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - configure_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - rsyslog_filecreatemode

    - name: Ensure rsyslog Default File Permissions Configured - Assemble List of rsyslog
        Configuration Files with $FileCreateMode Parameter
      ansible.builtin.set_fact:
        rsyslog_filecreatemode_files: '{{ rsyslog_main_file_with_filecreatemode.files
          | map(attribute=''path'') | list + rsyslog_includes_with_filecreatemode.files
          | map(attribute=''path'') | list }}'
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - configure_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - rsyslog_filecreatemode

    - name: Ensure rsyslog Default File Permissions Configured - Remove $FileCreateMode
        Parameter from Multiple Files to Avoid Conflicts
      ansible.builtin.lineinfile:
        path: '{{ item }}'
        regexp: \$FileCreateMode.*
        state: absent
      register: result_rsyslog_filecreatemode_removed
      loop: '{{ rsyslog_filecreatemode_files }}'
      when:
      - '"linux-base" in ansible_facts.packages'
      - rsyslog_filecreatemode_files | length > 1
      tags:
      - configure_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - rsyslog_filecreatemode

    - name: Ensure rsyslog Default File Permissions Configured - Add $FileCreateMode Parameter
        and Expected Value
      ansible.builtin.lineinfile:
        path: /etc/rsyslog.d/99-rsyslog_filecreatemode.conf
        line: $FileCreateMode 0640
        mode: 416
        create: true
      when:
      - '"linux-base" in ansible_facts.packages'
      - rsyslog_filecreatemode_files | length == 0 or result_rsyslog_filecreatemode_removed
        is not skipped
      tags:
      - configure_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - rsyslog_filecreatemode

    - name: Ensure rsyslog Default File Permissions Configured - Ensure Correct Value
        of Existing $FileCreateMode Parameter
      ansible.builtin.lineinfile:
        path: '{{ item }}'
        regexp: ^\$FileCreateMode
        line: $FileCreateMode 0640
      loop: '{{ rsyslog_filecreatemode_files }}'
      when:
      - '"linux-base" in ansible_facts.packages'
      - rsyslog_filecreatemode_files | length == 1
      tags:
      - configure_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - rsyslog_filecreatemode

Group Network Configuration and Firewalls Group contains 12 groups and 45 rules

[ref] Most systems must be connected to a network of some sort, and this brings with it the substantial risk of network attack. This section discusses the security impact of decisions about networking which must be made when configuring a system.
This section also discusses firewalls, network access controls, and other network security frameworks, which allow system-level rules to be written that can limit an attackers' ability to connect to your system. These rules can specify that network traffic should be allowed or denied from certain IP addresses, hosts, and networks. The rules can also specify which of the system's network services are available to particular hosts or networks.

Group iptables and ip6tables Group contains 2 groups and 7 rules

[ref] A host-based firewall called `netfilter` is included as part of the Linux kernel distributed with the system. It is activated by default. This firewall is controlled by the program `iptables`, and the entire capability is frequently referred to by this name. An analogous program called `ip6tables` handles filtering for IPv6.
Unlike TCP Wrappers, which depends on the network server program to support and respect the rules written, `netfilter` filtering occurs at the kernel level, before a program can even process the data from the network packet. As such, any program on the system is affected by the rules written.
This section provides basic information about strengthening the `iptables` and `ip6tables` configurations included with the system. For more complete information that may allow the construction of a sophisticated ruleset tailored to your environment, please consult the references at the end of this section.

Group Inspect and Activate Default Rules Group contains 3 rules

[ref] View the currently-enforced `iptables` rules by running the command:

    $ sudo iptables -nL --line-numbers

The command is analogous for `ip6tables`.
If the firewall does not appear to be active (i.e., no rules appear), activate it and ensure that it starts at boot by issuing the following commands (and analogously for `ip6tables`):

    $ sudo service iptables restart

The default iptables rules are:

    Chain INPUT (policy ACCEPT)
    num  target     prot opt source       destination
    1    ACCEPT     all  --  0.0.0.0/0    0.0.0.0/0    state RELATED,ESTABLISHED
    2    ACCEPT     icmp --  0.0.0.0/0    0.0.0.0/0
    3    ACCEPT     all  --  0.0.0.0/0    0.0.0.0/0
    4    ACCEPT     tcp  --  0.0.0.0/0    0.0.0.0/0    state NEW tcp dpt:22
    5    REJECT     all  --  0.0.0.0/0    0.0.0.0/0    reject-with icmp-host-prohibited

    Chain FORWARD (policy ACCEPT)
    num  target     prot opt source       destination
    1    REJECT     all  --  0.0.0.0/0    0.0.0.0/0    reject-with icmp-host-prohibited

    Chain OUTPUT (policy ACCEPT)
    num  target     prot opt source       destination

The `ip6tables` default rules are essentially the same.

#### Rule Set Default ip6tables Policy for Incoming Packets [ref]

To set the default policy to DROP (instead of ACCEPT) for the built-in INPUT chain which processes incoming packets, add or correct the following line in `/etc/iptables/rules.v6`:

    :INPUT DROP [0:0]

If changes were required, reload the ip6tables rules:

    $ sudo service ip6tables reload

Rationale: | In `ip6tables`, the default policy is applied only after all the applicable rules in the table are examined for a match. Setting the default policy to `DROP` implements proper design for a firewall, i.e. any packets which are not explicitly permitted should not be accepted.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_set_ip6tables_default_rule

References:

cis-csc | 11, 14, 3, 9
cobit5 | BAI10.01, BAI10.02, BAI10.03, BAI10.05, DSS05.02, DSS05.05, DSS06.06
isa-62443-2009 | 4.3.3.5.1, 4.3.3.5.2, 4.3.3.5.3, 4.3.3.5.4, 4.3.3.5.5, 4.3.3.5.6, 4.3.3.5.7, 4.3.3.5.8, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.1, 4.3.3.7.2, 4.3.3.7.3, 4.3.3.7.4, 4.3.4.3.2, 4.3.4.3.3
isa-62443-2013 | SR 1.1, SR 1.10, SR 1.11, SR 1.12, SR 1.13, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.6, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 2.2, SR 2.3, SR 2.4, SR 2.5, SR 2.6, SR 2.7, SR 7.6
iso27001-2013 | A.12.1.2, A.12.5.1, A.12.6.2, A.14.2.2, A.14.2.3, A.14.2.4, A.9.1.2
nerc-cip | CIP-003-8 R4, CIP-003-8 R5, CIP-004-6 R3
nist | AC-4, CM-7(b), CA-3(5), SC-7(21), CM-6(a)
nist-csf | PR.IP-1, PR.PT-3
cis | 3.5.3.3.1
pcidss4 | 1.4.1, 1.4

Remediation Shell script ⇲

    # Remediation is applicable only in certain platforms
    if ( ! ( dpkg-query --show --showformat='${db:Status-Status}\n' 'nftables' 2>/dev/null | grep -q '^installed' ) && ! ( dpkg-query --show --showformat='${db:Status-Status}\n' 'ufw' 2>/dev/null | grep -q '^installed' ) && dpkg-query --show --showformat='${db:Status-Status}\n' 'iptables' 2>/dev/null | grep -q '^installed' ); then

    DEBIAN_FRONTEND=noninteractive apt-get install -y "iptables-persistent"
    sed -i 's/^:INPUT ACCEPT.*/:INPUT DROP [0:0]/g' /etc/iptables/rules.v6

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

#### Rule Set configuration for IPv6 loopback traffic [ref]

Configure the loopback interface to accept traffic. Configure all other interfaces to deny traffic to the loopback network. Warning: Changing firewall settings while connected over network can result in being locked out of the system.
Rationale: | Loopback traffic is generated between processes on machine and is typically critical to operation of the system. The loopback interface is the only place that loopback network traffic should be seen, all other interfaces should ignore traffic on this network as an anti-spoofing measure.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_set_ipv6_loopback_traffic

References:

pcidss | Req-1.3
cis | 3.5.3.3.2
pcidss4 | 1.4.1, 1.4

Remediation Shell script ⇲

    # Remediation is applicable only in certain platforms
    if ( ! ( dpkg-query --show --showformat='${db:Status-Status}\n' 'nftables' 2>/dev/null | grep -q '^installed' ) && ! ( dpkg-query --show --showformat='${db:Status-Status}\n' 'ufw' 2>/dev/null | grep -q '^installed' ) && dpkg-query --show --showformat='${db:Status-Status}\n' 'iptables' 2>/dev/null | grep -q '^installed' ); then

    if [ "$(sysctl -n net.ipv6.conf.all.disable_ipv6)" -eq 0 ]; then
      # IPv6 is not disabled, so run the script
      ip6tables -A INPUT -i lo -j ACCEPT
      ip6tables -A OUTPUT -o lo -j ACCEPT
      ip6tables -A INPUT -s ::1 -j DROP
    fi

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - PCI-DSS-Req-1.3
      - PCI-DSSv4-1.4
      - PCI-DSSv4-1.4.1
      - medium_severity
      - set_ipv6_loopback_traffic

    - name: Check if IPv6 is enabled
      command: sysctl -n net.ipv6.conf.all.disable_ipv6
      register: ipv6_status
      failed_when: ipv6_status.stdout != "0"
      when: ( not ( "nftables" in ansible_facts.packages ) and not ( "ufw" in ansible_facts.packages
        ) and "iptables" in ansible_facts.packages )
      tags:
      - PCI-DSS-Req-1.3
      - PCI-DSSv4-1.4
      - PCI-DSSv4-1.4.1
      - medium_severity
      - set_ipv6_loopback_traffic

    - name: Allow incoming traffic on the loopback interface
      ansible.builtin.iptables:
        ipv6: true
        chain: INPUT
        in_interface: lo
        jump: ACCEPT
      when:
      - ( not ( "nftables" in ansible_facts.packages ) and not ( "ufw" in ansible_facts.packages
        ) and "iptables" in ansible_facts.packages )
      - ipv6_status.stdout == '0'
      tags:
      - PCI-DSS-Req-1.3
      - PCI-DSSv4-1.4
      - PCI-DSSv4-1.4.1
      - medium_severity
      - set_ipv6_loopback_traffic

    - name: Allow outgoing traffic on the loopback interface
      ansible.builtin.iptables:
        ipv6: true
        chain: OUTPUT
        out_interface: lo
        jump: ACCEPT
      when:
      - ( not ( "nftables" in ansible_facts.packages ) and not ( "ufw" in ansible_facts.packages
        ) and "iptables" in ansible_facts.packages )
      - ipv6_status.stdout == '0'
      tags:
      - PCI-DSS-Req-1.3
      - PCI-DSSv4-1.4
      - PCI-DSSv4-1.4.1
      - medium_severity
      - set_ipv6_loopback_traffic

    - name: Drop incoming traffic from the localhost
      ansible.builtin.iptables:
        ipv6: true
        chain: INPUT
        source: ::1
        jump: DROP
      when:
      - ( not ( "nftables" in ansible_facts.packages ) and not ( "ufw" in ansible_facts.packages
        ) and "iptables" in ansible_facts.packages )
      - ipv6_status.stdout == '0'
      tags:
      - PCI-DSS-Req-1.3
      - PCI-DSSv4-1.4
      - PCI-DSSv4-1.4.1
      - medium_severity
      - set_ipv6_loopback_traffic

#### Rule Set configuration for loopback traffic [ref]

Configure the loopback interface to accept traffic. Configure all other interfaces to deny traffic to the loopback network. Warning: Changing firewall settings while connected over network can result in being locked out of the system.
Rationale: | Loopback traffic is generated between processes on machine and is typically critical to operation of the system. The loopback interface is the only place that loopback network traffic should be seen, all other interfaces should ignore traffic on this network as an anti-spoofing measure.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_set_loopback_traffic

References:

pcidss | Req-1.3
cis | 3.5.3.2.2
pcidss4 | 1.4.1, 1.4

Remediation Shell script ⇲

    # Remediation is applicable only in certain platforms
    if ( ! ( dpkg-query --show --showformat='${db:Status-Status}\n' 'nftables' 2>/dev/null | grep -q '^installed' ) && ! ( dpkg-query --show --showformat='${db:Status-Status}\n' 'ufw' 2>/dev/null | grep -q '^installed' ) && dpkg-query --show --showformat='${db:Status-Status}\n' 'iptables' 2>/dev/null | grep -q '^installed' ); then

    iptables -A INPUT -i lo -j ACCEPT
    iptables -A OUTPUT -o lo -j ACCEPT
    iptables -A INPUT -s 127.0.0.0/8 -j DROP

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - PCI-DSS-Req-1.3
      - PCI-DSSv4-1.4
      - PCI-DSSv4-1.4.1
      - medium_severity
      - set_loopback_traffic

    - name: Allow incoming traffic on the loopback interface
      ansible.builtin.iptables:
        chain: INPUT
        in_interface: lo
        jump: ACCEPT
      when: ( not ( "nftables" in ansible_facts.packages ) and not ( "ufw" in ansible_facts.packages
        ) and "iptables" in ansible_facts.packages )
      tags:
      - PCI-DSS-Req-1.3
      - PCI-DSSv4-1.4
      - PCI-DSSv4-1.4.1
      - medium_severity
      - set_loopback_traffic

    - name: Allow outgoing traffic on the loopback interface
      ansible.builtin.iptables:
        chain: OUTPUT
        out_interface: lo
        jump: ACCEPT
      when: ( not ( "nftables" in ansible_facts.packages ) and not ( "ufw" in ansible_facts.packages
        ) and "iptables" in ansible_facts.packages )
      tags:
      - PCI-DSS-Req-1.3
      - PCI-DSSv4-1.4
      - PCI-DSSv4-1.4.1
      - medium_severity
      - set_loopback_traffic

    - name: Drop incoming traffic from the localhost
      ansible.builtin.iptables:
        chain: INPUT
        source: 127.0.0.0/8
        jump: DROP
      when: ( not ( "nftables" in ansible_facts.packages ) and not ( "ufw" in ansible_facts.packages
        ) and "iptables" in ansible_facts.packages )
      tags:
      - PCI-DSS-Req-1.3
      - PCI-DSSv4-1.4
      - PCI-DSSv4-1.4.1
      - medium_severity
      - set_loopback_traffic

Group Strengthen the Default Ruleset Group contains 1 rule

[ref] The default rules can be strengthened. The system scripts that activate the firewall rules expect them to be defined in the configuration files `iptables` and `ip6tables` in the directory `/etc/sysconfig`. Many of the lines in these files are similar to the command line arguments that would be provided to the programs `/sbin/iptables` or `/sbin/ip6tables` - but some are quite different.
The following recommendations describe how to strengthen the default ruleset configuration file. An alternative to editing this configuration file is to create a shell script that makes calls to the iptables program to load in rules, and then invokes service iptables save to write those loaded rules to `/etc/sysconfig/iptables.`
The following alterations can be made directly to `/etc/sysconfig/iptables` and `/etc/sysconfig/ip6tables`. Instructions apply to both unless otherwise noted. Language and address conventions for regular iptables are used throughout this section; configuration for ip6tables will be either analogous or explicitly covered.
Warning: The program `system-config-securitylevel` allows additional services to penetrate the default firewall rules and automatically adjusts `/etc/sysconfig/iptables`. This program is only useful if the default ruleset meets your security requirements. Otherwise, this program should not be used to make changes to the firewall configuration because it re-writes the saved configuration file.

#### Rule Set Default iptables Policy for Incoming Packets [ref]

To set the default policy to DROP (instead of ACCEPT) for the built-in INPUT chain which processes incoming packets, add or correct the following line in `/etc/sysconfig/iptables`:

    :INPUT DROP [0:0]

Rationale: | In `iptables` the default policy is applied only after all the applicable rules in the table are examined for a match. Setting the default policy to `DROP` implements proper design for a firewall, i.e. any packets which are not explicitly permitted should not be accepted.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_set_iptables_default_rule

References:

cis-csc | 11, 14, 3, 9
cobit5 | BAI10.01, BAI10.02, BAI10.03, BAI10.05, DSS05.02, DSS05.05, DSS06.06
isa-62443-2009 | 4.3.3.5.1, 4.3.3.5.2, 4.3.3.5.3, 4.3.3.5.4, 4.3.3.5.5, 4.3.3.5.6, 4.3.3.5.7, 4.3.3.5.8, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.1, 4.3.3.7.2, 4.3.3.7.3, 4.3.3.7.4, 4.3.4.3.2, 4.3.4.3.3
isa-62443-2013 | SR 1.1, SR 1.10, SR 1.11, SR 1.12, SR 1.13, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.6, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 2.2, SR 2.3, SR 2.4, SR 2.5, SR 2.6, SR 2.7, SR 7.6
iso27001-2013 | A.12.1.2, A.12.5.1, A.12.6.2, A.14.2.2, A.14.2.3, A.14.2.4, A.9.1.2
nist | CA-3(5), CM-7(b), SC-7(23), CM-6(a)
nist-csf | PR.IP-1, PR.PT-3
cis | 3.5.3.2.1

Remediation Shell script ⇲

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}\n' 'iptables' 2>/dev/null | grep -q '^installed' && { ( ! ( dpkg-query --show --showformat='${db:Status-Status}\n' 'nftables' 2>/dev/null | grep -q '^installed' ) && ! ( dpkg-query --show --showformat='${db:Status-Status}\n' 'ufw' 2>/dev/null | grep -q '^installed' ) ); }; then

    sed -i 's/^:INPUT ACCEPT.*/:INPUT DROP [0:0]/g' /etc/sysconfig/iptables

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

#### Rule Install iptables-persistent Package [ref]

The `iptables-persistent` package can be installed with the following command:

    $ apt-get install iptables-persistent

Rationale: | A method of configuring and maintaining firewall rules is necessary to configure a Host Based Firewall.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_package_iptables-persistent_installed

References:

cis | 3.5.3.1.1

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | enable

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}\n' 'iptables' 2>/dev/null | grep -q '^installed'; then

    DEBIAN_FRONTEND=noninteractive apt-get install -y "iptables-persistent"

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation OSBuild Blueprint snippet ⇲

    [[packages]]
    name = "iptables-persistent"
    version = "*"

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | enable

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - enable_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - package_iptables-persistent_installed

    - name: Ensure iptables-persistent is installed
      package:
        name: iptables-persistent
        state: present
      when: '"iptables" in ansible_facts.packages'
      tags:
      - enable_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - package_iptables-persistent_installed

Remediation Puppet snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | enable

    include install_iptables-persistent

    class install_iptables-persistent {
      package { 'iptables-persistent':
        ensure => 'installed',
      }
    }

#### Rule Install iptables Package [ref]

The `iptables` package can be installed with the following command:

    $ apt-get install iptables

Rationale: | `iptables` controls the Linux kernel network packet filtering code. `iptables` allows system operators to set up firewalls and IP masquerading, etc.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_package_iptables_installed

References:

nist | CM-6(a)
pcidss | Req-1.4.1
os-srg | SRG-OS-000480-GPOS-00227
cis | 3.5.3.1.1

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | enable

    # Remediation is applicable only in certain platforms
    if ( dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed ); then

    DEBIAN_FRONTEND=noninteractive apt-get install -y "iptables"

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation OSBuild Blueprint snippet ⇲

    [[packages]]
    name = "iptables"
    version = "*"

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | enable

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - NIST-800-53-CM-6(a)
      - PCI-DSS-Req-1.4.1
      - enable_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - package_iptables_installed

    - name: Ensure iptables is installed
      package:
        name: iptables
        state: present
      when: ( "linux-base" in ansible_facts.packages )
      tags:
      - NIST-800-53-CM-6(a)
      - PCI-DSS-Req-1.4.1
      - enable_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - package_iptables_installed

Remediation Puppet snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | enable

    include install_iptables

    class install_iptables {
      package { 'iptables':
        ensure => 'installed',
      }
    }

#### Rule Remove iptables-persistent Package [ref]

The `iptables-persistent` package can be removed with the following command:

    $ apt-get remove iptables-persistent

Rationale: | Running both `ufw` and the services included in the `iptables-persistent` package may lead to conflict.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_package_iptables-persistent_removed

References:

cis | 3.5.1.2

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}\n' 'ufw' 2>/dev/null | grep -q '^installed'; then

    # CAUTION: This remediation script will remove iptables-persistent
    #	   from the system, and may remove any packages
    #	   that depend on iptables-persistent. Execute this
    #	   remediation AFTER testing on a non-production
    #	   system!

    DEBIAN_FRONTEND=noninteractive apt-get remove -y "iptables-persistent"

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - disable_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - package_iptables-persistent_removed

    - name: Ensure iptables-persistent is removed
      package:
        name: iptables-persistent
        state: absent
      when: '"ufw" in ansible_facts.packages'
      tags:
      - disable_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - package_iptables-persistent_removed

Remediation Puppet snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    include remove_iptables-persistent

    class remove_iptables-persistent {
      package { 'iptables-persistent':
        ensure => 'purged',
      }
    }

Group IPv6 Group contains 1 group and 7 rules
[ref] The system includes support for Internet Protocol version 6. A major and often-mentioned improvement over IPv4 is its enormous increase in the number of available addresses. Another important feature is its support for automatic configuration of many network settings.
Group Configure IPv6 Settings if Necessary Group contains 7 rules
[ref] A major feature of IPv6 is the extent to which systems implementing it can automatically configure their networking devices using information from the network. From a security perspective, manually configuring important configuration information is preferable to accepting it from the network in an unauthenticated fashion.

#### Rule Configure Accepting Router Advertisements on All IPv6 Interfaces [ref]

To set the runtime status of the `net.ipv6.conf.all.accept_ra` kernel parameter, run the following command:

    $ sudo sysctl -w net.ipv6.conf.all.accept_ra=0

To make sure that the setting is persistent, add the following line to a file in the directory `/etc/sysctl.d`:

    net.ipv6.conf.all.accept_ra = 0

Rationale: | An illicit router advertisement message could result in a man-in-the-middle attack.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_sysctl_net_ipv6_conf_all_accept_ra

References:

cis-csc | 11, 14, 3, 9
cobit5 | BAI10.01, BAI10.02, BAI10.03, BAI10.05, DSS05.02, DSS05.05, DSS06.06
cui | 3.1.20
disa | CCI-000366
isa-62443-2009 | 4.3.3.5.1, 4.3.3.5.2, 4.3.3.5.3, 4.3.3.5.4, 4.3.3.5.5, 4.3.3.5.6, 4.3.3.5.7, 4.3.3.5.8, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.1, 4.3.3.7.2, 4.3.3.7.3, 4.3.3.7.4, 4.3.4.3.2, 4.3.4.3.3
isa-62443-2013 | SR 1.1, SR 1.10, SR 1.11, SR 1.12, SR 1.13, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.6, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 2.2, SR 2.3, SR 2.4, SR 2.5, SR 2.6, SR 2.7, SR 7.6
iso27001-2013 | A.12.1.2, A.12.5.1, A.12.6.2, A.14.2.2, A.14.2.3, A.14.2.4, A.9.1.2
nist | CM-7(a), CM-7(b), CM-6(a)
nist-csf | PR.IP-1, PR.PT-3
os-srg | SRG-OS-000480-GPOS-00227
cis | 3.3.9

Remediation Shell script ⇲

Complexity: | low
Disruption: | medium
Reboot: | true
Strategy: | disable

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    # Comment out any occurrences of net.ipv6.conf.all.accept_ra from /etc/sysctl.d/*.conf files

    for f in /etc/sysctl.d/*.conf /run/sysctl.d/*.conf /usr/local/lib/sysctl.d/*.conf; do

      # skip systemd-sysctl symlink (/etc/sysctl.d/99-sysctl.conf -> /etc/sysctl.conf)
      if [[ "$(readlink -f "$f")" == "/etc/sysctl.conf" ]]; then continue; fi

      matching_list=$(grep -P '^(?!#).*[\s]*net.ipv6.conf.all.accept_ra.*$' $f | uniq )
      if ! test -z "$matching_list"; then
        while IFS= read -r entry; do
          escaped_entry=$(sed -e 's|/|\\/|g' <<< "$entry")
          # comment out "net.ipv6.conf.all.accept_ra" matches to preserve user data
          sed -i --follow-symlinks "s/^${escaped_entry}$/# &/g" $f
        done <<< "$matching_list"
      fi
    done

    #
    # Set sysctl config file which to save the desired value
    #

    SYSCONFIG_FILE="/etc/sysctl.conf"

    sysctl_net_ipv6_conf_all_accept_ra_value='0'

    #
    # Set runtime for net.ipv6.conf.all.accept_ra
    #
    if [[ "$OSCAP_BOOTC_BUILD" != "YES" ]] ; then
        /sbin/sysctl -q -n -w net.ipv6.conf.all.accept_ra="$sysctl_net_ipv6_conf_all_accept_ra_value"
    fi

    #
    # If net.ipv6.conf.all.accept_ra present in /etc/sysctl.conf, change value to appropriate value
    #	else, add "net.ipv6.conf.all.accept_ra = value" to /etc/sysctl.conf
    #

    # Strip any search characters in the key arg so that the key can be replaced without
    # adding any search characters to the config file.
    stripped_key=$(sed 's/[\^=\$,;+]*//g' <<< "^net.ipv6.conf.all.accept_ra")

    # shellcheck disable=SC2059
    printf -v formatted_output "%s = %s" "$stripped_key" "$sysctl_net_ipv6_conf_all_accept_ra_value"

    # If the key exists, change it. Otherwise, add it to the config_file.
    # We search for the key string followed by a word boundary (matched by \>),
    # so if we search for 'setting', 'setting2' won't match.
    if LC_ALL=C grep -q -m 1 -i -e "^net.ipv6.conf.all.accept_ra\\>" "${SYSCONFIG_FILE}"; then
        escaped_formatted_output=$(sed -e 's|/|\\/|g' <<< "$formatted_output")
        LC_ALL=C sed -i --follow-symlinks "s/^net.ipv6.conf.all.accept_ra\\>.*/$escaped_formatted_output/gi" "${SYSCONFIG_FILE}"
    else
        if [[ -s "${SYSCONFIG_FILE}" ]] && [[ -n "$(tail -c 1 -- "${SYSCONFIG_FILE}" || true)" ]]; then
            LC_ALL=C sed -i --follow-symlinks '$a'\\ "${SYSCONFIG_FILE}"
        fi
        printf '%s\n' "$formatted_output" >> "${SYSCONFIG_FILE}"
    fi

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | medium
Reboot: | true
Strategy: | disable

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_net_ipv6_conf_all_accept_ra

    - name: List /etc/sysctl.d/*.conf files
      find:
        paths:
        - /etc/sysctl.d/
        - /run/sysctl.d/
        - /usr/local/lib/sysctl.d/
        contains: ^[\s]*net.ipv6.conf.all.accept_ra.*$
        patterns: '*.conf'
        file_type: any
      register: find_sysctl_d
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_net_ipv6_conf_all_accept_ra

    - name: Comment out any occurrences of net.ipv6.conf.all.accept_ra from config files
      replace:
        path: '{{ item.path }}'
        regexp: ^[\s]*net.ipv6.conf.all.accept_ra
        replace: '#net.ipv6.conf.all.accept_ra'
      loop: '{{ find_sysctl_d.files }}'
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_net_ipv6_conf_all_accept_ra
    - name: XCCDF Value sysctl_net_ipv6_conf_all_accept_ra_value # promote to variable
      set_fact:
        sysctl_net_ipv6_conf_all_accept_ra_value: !!str 0
      tags:
        - always

    - name: Ensure sysctl net.ipv6.conf.all.accept_ra is set
      sysctl:
        name: net.ipv6.conf.all.accept_ra
        value: '{{ sysctl_net_ipv6_conf_all_accept_ra_value }}'
        sysctl_file: /etc/sysctl.conf
        state: present
        reload: true
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_net_ipv6_conf_all_accept_ra

#### Rule Disable Accepting ICMP Redirects for All IPv6 Interfaces [ref]

To set the runtime status of the `net.ipv6.conf.all.accept_redirects` kernel parameter, run the following command:

    $ sudo sysctl -w net.ipv6.conf.all.accept_redirects=0

To make sure that the setting is persistent, add the following line to a file in the directory `/etc/sysctl.d`:

    net.ipv6.conf.all.accept_redirects = 0

Rationale: | An illicit ICMP redirect message could result in a man-in-the-middle attack.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_sysctl_net_ipv6_conf_all_accept_redirects

References:

cis-csc | 11, 14, 3, 9
cobit5 | BAI10.01, BAI10.02, BAI10.03, BAI10.05, DSS05.02, DSS05.05, DSS06.06
cui | 3.1.20
disa | CCI-000366
isa-62443-2009 | 4.3.3.5.1, 4.3.3.5.2, 4.3.3.5.3, 4.3.3.5.4, 4.3.3.5.5, 4.3.3.5.6, 4.3.3.5.7, 4.3.3.5.8, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.1, 4.3.3.7.2, 4.3.3.7.3, 4.3.3.7.4, 4.3.4.3.2, 4.3.4.3.3
isa-62443-2013 | SR 1.1, SR 1.10, SR 1.11, SR 1.12, SR 1.13, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.6, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 2.2, SR 2.3, SR 2.4, SR 2.5, SR 2.6, SR 2.7, SR 7.6
iso27001-2013 | A.12.1.2, A.12.5.1, A.12.6.2, A.14.2.2, A.14.2.3, A.14.2.4, A.9.1.2
nist | CM-7(a), CM-7(b), CM-6(a), CM-6(b), CM-6.1(iv)
nist-csf | PR.IP-1, PR.PT-3
os-srg | SRG-OS-000480-GPOS-00227
cis | 3.3.2
anssi | R13

Remediation Shell script ⇲

Complexity: | low
Disruption: | medium
Reboot: | true
Strategy: | disable

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    # Comment out any occurrences of net.ipv6.conf.all.accept_redirects from /etc/sysctl.d/*.conf files

    for f in /etc/sysctl.d/*.conf /run/sysctl.d/*.conf /usr/local/lib/sysctl.d/*.conf; do

      # skip systemd-sysctl symlink (/etc/sysctl.d/99-sysctl.conf -> /etc/sysctl.conf)
      if [[ "$(readlink -f "$f")" == "/etc/sysctl.conf" ]]; then continue; fi

      matching_list=$(grep -P '^(?!#).*[\s]*net.ipv6.conf.all.accept_redirects.*$' $f | uniq )
      if ! test -z "$matching_list"; then
        while IFS= read -r entry; do
          escaped_entry=$(sed -e 's|/|\\/|g' <<< "$entry")
          # comment out "net.ipv6.conf.all.accept_redirects" matches to preserve user data
          sed -i --follow-symlinks "s/^${escaped_entry}$/# &/g" $f
        done <<< "$matching_list"
      fi
    done

    #
    # Set sysctl config file which to save the desired value
    #

    SYSCONFIG_FILE="/etc/sysctl.conf"

    sysctl_net_ipv6_conf_all_accept_redirects_value='0'

    #
    # Set runtime for net.ipv6.conf.all.accept_redirects
    #
    if [[ "$OSCAP_BOOTC_BUILD" != "YES" ]] ; then
        /sbin/sysctl -q -n -w net.ipv6.conf.all.accept_redirects="$sysctl_net_ipv6_conf_all_accept_redirects_value"
    fi

    #
    # If net.ipv6.conf.all.accept_redirects present in /etc/sysctl.conf, change value to appropriate value
    #	else, add "net.ipv6.conf.all.accept_redirects = value" to /etc/sysctl.conf
    #

    # Strip any search characters in the key arg so that the key can be replaced without
    # adding any search characters to the config file.
    stripped_key=$(sed 's/[\^=\$,;+]*//g' <<< "^net.ipv6.conf.all.accept_redirects")

    # shellcheck disable=SC2059
    printf -v formatted_output "%s = %s" "$stripped_key" "$sysctl_net_ipv6_conf_all_accept_redirects_value"

    # If the key exists, change it. Otherwise, add it to the config_file.
    # We search for the key string followed by a word boundary (matched by \>),
    # so if we search for 'setting', 'setting2' won't match.
    if LC_ALL=C grep -q -m 1 -i -e "^net.ipv6.conf.all.accept_redirects\\>" "${SYSCONFIG_FILE}"; then
        escaped_formatted_output=$(sed -e 's|/|\\/|g' <<< "$formatted_output")
        LC_ALL=C sed -i --follow-symlinks "s/^net.ipv6.conf.all.accept_redirects\\>.*/$escaped_formatted_output/gi" "${SYSCONFIG_FILE}"
    else
        if [[ -s "${SYSCONFIG_FILE}" ]] && [[ -n "$(tail -c 1 -- "${SYSCONFIG_FILE}" || true)" ]]; then
            LC_ALL=C sed -i --follow-symlinks '$a'\\ "${SYSCONFIG_FILE}"
        fi
        printf '%s\n' "$formatted_output" >> "${SYSCONFIG_FILE}"
    fi

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | medium
Reboot: | true
Strategy: | disable

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-6(b)
      - NIST-800-53-CM-6.1(iv)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_net_ipv6_conf_all_accept_redirects

    - name: List /etc/sysctl.d/*.conf files
      find:
        paths:
        - /etc/sysctl.d/
        - /run/sysctl.d/
        - /usr/local/lib/sysctl.d/
        contains: ^[\s]*net.ipv6.conf.all.accept_redirects.*$
        patterns: '*.conf'
        file_type: any
      register: find_sysctl_d
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-6(b)
      - NIST-800-53-CM-6.1(iv)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_net_ipv6_conf_all_accept_redirects

    - name: Comment out any occurrences of net.ipv6.conf.all.accept_redirects from config
        files
      replace:
        path: '{{ item.path }}'
        regexp: ^[\s]*net.ipv6.conf.all.accept_redirects
        replace: '#net.ipv6.conf.all.accept_redirects'
      loop: '{{ find_sysctl_d.files }}'
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-6(b)
      - NIST-800-53-CM-6.1(iv)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_net_ipv6_conf_all_accept_redirects
    - name: XCCDF Value sysctl_net_ipv6_conf_all_accept_redirects_value # promote to variable
      set_fact:
        sysctl_net_ipv6_conf_all_accept_redirects_value: !!str 0
      tags:
        - always

    - name: Ensure sysctl net.ipv6.conf.all.accept_redirects is set
      sysctl:
        name: net.ipv6.conf.all.accept_redirects
        value: '{{ sysctl_net_ipv6_conf_all_accept_redirects_value }}'
        sysctl_file: /etc/sysctl.conf
        state: present
        reload: true
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-6(b)
      - NIST-800-53-CM-6.1(iv)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_net_ipv6_conf_all_accept_redirects

#### Rule Disable Kernel Parameter for Accepting Source-Routed Packets on all IPv6 Interfaces [ref]

To set the runtime status of the `net.ipv6.conf.all.accept_source_route` kernel parameter, run the following command:

    $ sudo sysctl -w net.ipv6.conf.all.accept_source_route=0

To make sure that the setting is persistent, add the following line to a file in the directory `/etc/sysctl.d`:

    net.ipv6.conf.all.accept_source_route = 0

Rationale:

Source-routed packets allow the source of the packet to suggest routers forward the packet along a different path than configured on the router, which can be used to bypass network security measures. This requirement applies only to the forwarding of source-routerd traffic, such as when IPv6 forwarding is enabled and the system is functioning as a router.
Accepting source-routed packets in the IPv6 protocol has few legitimate uses. It should be disabled unless it is absolutely required.

Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_sysctl_net_ipv6_conf_all_accept_source_route

References:

cis-csc | 1, 12, 13, 14, 15, 16, 18, 4, 6, 8, 9
cobit5 | APO01.06, APO13.01, DSS01.05, DSS03.01, DSS05.02, DSS05.04, DSS05.07, DSS06.02
cui | 3.1.20
disa | CCI-000366
isa-62443-2009 | 4.2.3.4, 4.3.3.4, 4.4.3.3
isa-62443-2013 | SR 3.1, SR 3.5, SR 3.8, SR 4.1, SR 4.3, SR 5.1, SR 5.2, SR 5.3, SR 7.1, SR 7.6
iso27001-2013 | A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.12.1.1, A.12.1.2, A.13.1.1, A.13.1.2, A.13.1.3, A.13.2.1, A.13.2.2, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, A.6.1.2, A.7.1.1, A.7.1.2, A.7.3.1, A.8.2.2, A.8.2.3, A.9.1.1, A.9.1.2, A.9.2.3, A.9.4.1, A.9.4.4, A.9.4.5
nist | CM-7(a), CM-7(b), CM-6(a)
nist-csf | DE.AE-1, ID.AM-3, PR.AC-5, PR.DS-5, PR.PT-4
os-srg | SRG-OS-000480-GPOS-00227
cis | 3.3.1
anssi | R13

Remediation Shell script ⇲

Complexity: | low
Disruption: | medium
Reboot: | true
Strategy: | disable

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    # Comment out any occurrences of net.ipv6.conf.all.accept_source_route from /etc/sysctl.d/*.conf files

    for f in /etc/sysctl.d/*.conf /run/sysctl.d/*.conf /usr/local/lib/sysctl.d/*.conf; do

      # skip systemd-sysctl symlink (/etc/sysctl.d/99-sysctl.conf -> /etc/sysctl.conf)
      if [[ "$(readlink -f "$f")" == "/etc/sysctl.conf" ]]; then continue; fi

      matching_list=$(grep -P '^(?!#).*[\s]*net.ipv6.conf.all.accept_source_route.*$' $f | uniq )
      if ! test -z "$matching_list"; then
        while IFS= read -r entry; do
          escaped_entry=$(sed -e 's|/|\\/|g' <<< "$entry")
          # comment out "net.ipv6.conf.all.accept_source_route" matches to preserve user data
          sed -i --follow-symlinks "s/^${escaped_entry}$/# &/g" $f
        done <<< "$matching_list"
      fi
    done

    #
    # Set sysctl config file which to save the desired value
    #

    SYSCONFIG_FILE="/etc/sysctl.conf"

    sysctl_net_ipv6_conf_all_accept_source_route_value='0'

    #
    # Set runtime for net.ipv6.conf.all.accept_source_route
    #
    if [[ "$OSCAP_BOOTC_BUILD" != "YES" ]] ; then
        /sbin/sysctl -q -n -w net.ipv6.conf.all.accept_source_route="$sysctl_net_ipv6_conf_all_accept_source_route_value"
    fi

    #
    # If net.ipv6.conf.all.accept_source_route present in /etc/sysctl.conf, change value to appropriate value
    #	else, add "net.ipv6.conf.all.accept_source_route = value" to /etc/sysctl.conf
    #

    # Strip any search characters in the key arg so that the key can be replaced without
    # adding any search characters to the config file.
    stripped_key=$(sed 's/[\^=\$,;+]*//g' <<< "^net.ipv6.conf.all.accept_source_route")

    # shellcheck disable=SC2059
    printf -v formatted_output "%s = %s" "$stripped_key" "$sysctl_net_ipv6_conf_all_accept_source_route_value"

    # If the key exists, change it. Otherwise, add it to the config_file.
    # We search for the key string followed by a word boundary (matched by \>),
    # so if we search for 'setting', 'setting2' won't match.
    if LC_ALL=C grep -q -m 1 -i -e "^net.ipv6.conf.all.accept_source_route\\>" "${SYSCONFIG_FILE}"; then
        escaped_formatted_output=$(sed -e 's|/|\\/|g' <<< "$formatted_output")
        LC_ALL=C sed -i --follow-symlinks "s/^net.ipv6.conf.all.accept_source_route\\>.*/$escaped_formatted_output/gi" "${SYSCONFIG_FILE}"
    else
        if [[ -s "${SYSCONFIG_FILE}" ]] && [[ -n "$(tail -c 1 -- "${SYSCONFIG_FILE}" || true)" ]]; then
            LC_ALL=C sed -i --follow-symlinks '$a'\\ "${SYSCONFIG_FILE}"
        fi
        printf '%s\n' "$formatted_output" >> "${SYSCONFIG_FILE}"
    fi

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | medium
Reboot: | true
Strategy: | disable

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_net_ipv6_conf_all_accept_source_route

    - name: List /etc/sysctl.d/*.conf files
      find:
        paths:
        - /etc/sysctl.d/
        - /run/sysctl.d/
        - /usr/local/lib/sysctl.d/
        contains: ^[\s]*net.ipv6.conf.all.accept_source_route.*$
        patterns: '*.conf'
        file_type: any
      register: find_sysctl_d
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_net_ipv6_conf_all_accept_source_route

    - name: Comment out any occurrences of net.ipv6.conf.all.accept_source_route from
        config files
      replace:
        path: '{{ item.path }}'
        regexp: ^[\s]*net.ipv6.conf.all.accept_source_route
        replace: '#net.ipv6.conf.all.accept_source_route'
      loop: '{{ find_sysctl_d.files }}'
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_net_ipv6_conf_all_accept_source_route
    - name: XCCDF Value sysctl_net_ipv6_conf_all_accept_source_route_value # promote to variable
      set_fact:
        sysctl_net_ipv6_conf_all_accept_source_route_value: !!str 0
      tags:
        - always

    - name: Ensure sysctl net.ipv6.conf.all.accept_source_route is set
      sysctl:
        name: net.ipv6.conf.all.accept_source_route
        value: '{{ sysctl_net_ipv6_conf_all_accept_source_route_value }}'
        sysctl_file: /etc/sysctl.conf
        state: present
        reload: true
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_net_ipv6_conf_all_accept_source_route

#### Rule Disable Kernel Parameter for IPv6 Forwarding [ref]

To set the runtime status of the `net.ipv6.conf.all.forwarding` kernel parameter, run the following command:

    $ sudo sysctl -w net.ipv6.conf.all.forwarding=0

To make sure that the setting is persistent, add the following line to a file in the directory `/etc/sysctl.d`:

    net.ipv6.conf.all.forwarding = 0

Rationale: | IP forwarding permits the kernel to forward packets from one network interface to another. The ability to forward packets between two networks is only appropriate for systems acting as routers.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_sysctl_net_ipv6_conf_all_forwarding

References:

cis-csc | 1, 11, 12, 13, 14, 15, 16, 2, 3, 7, 8, 9
cobit5 | APO13.01, BAI04.04, BAI10.01, BAI10.02, BAI10.03, BAI10.05, DSS01.03, DSS03.05, DSS05.02, DSS05.05, DSS05.07, DSS06.06
disa | CCI-000366
isa-62443-2009 | 4.3.3.5.1, 4.3.3.5.2, 4.3.3.5.3, 4.3.3.5.4, 4.3.3.5.5, 4.3.3.5.6, 4.3.3.5.7, 4.3.3.5.8, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.1, 4.3.3.7.2, 4.3.3.7.3, 4.3.3.7.4, 4.3.4.3.2, 4.3.4.3.3
isa-62443-2013 | SR 1.1, SR 1.10, SR 1.11, SR 1.12, SR 1.13, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.6, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 2.2, SR 2.3, SR 2.4, SR 2.5, SR 2.6, SR 2.7, SR 6.2, SR 7.1, SR 7.2, SR 7.6
iso27001-2013 | A.12.1.2, A.12.1.3, A.12.5.1, A.12.6.2, A.14.2.2, A.14.2.3, A.14.2.4, A.17.2.1, A.9.1.2
nist | CM-7(a), CM-7(b), CM-6(a), CM-6(b), CM-6.1(iv)
nist-csf | DE.CM-1, PR.DS-4, PR.IP-1, PR.PT-3
os-srg | SRG-OS-000480-GPOS-00227
cis | 3.2.2

Remediation Shell script ⇲

Complexity: | low
Disruption: | medium
Reboot: | true
Strategy: | disable

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    # Comment out any occurrences of net.ipv6.conf.all.forwarding from /etc/sysctl.d/*.conf files

    for f in /etc/sysctl.d/*.conf /run/sysctl.d/*.conf /usr/local/lib/sysctl.d/*.conf; do

      # skip systemd-sysctl symlink (/etc/sysctl.d/99-sysctl.conf -> /etc/sysctl.conf)
      if [[ "$(readlink -f "$f")" == "/etc/sysctl.conf" ]]; then continue; fi

      matching_list=$(grep -P '^(?!#).*[\s]*net.ipv6.conf.all.forwarding.*$' $f | uniq )
      if ! test -z "$matching_list"; then
        while IFS= read -r entry; do
          escaped_entry=$(sed -e 's|/|\\/|g' <<< "$entry")
          # comment out "net.ipv6.conf.all.forwarding" matches to preserve user data
          sed -i --follow-symlinks "s/^${escaped_entry}$/# &/g" $f
        done <<< "$matching_list"
      fi
    done

    #
    # Set sysctl config file which to save the desired value
    #

    SYSCONFIG_FILE="/etc/sysctl.conf"

    sysctl_net_ipv6_conf_all_forwarding_value='0'

    #
    # Set runtime for net.ipv6.conf.all.forwarding
    #
    if [[ "$OSCAP_BOOTC_BUILD" != "YES" ]] ; then
        /sbin/sysctl -q -n -w net.ipv6.conf.all.forwarding="$sysctl_net_ipv6_conf_all_forwarding_value"
    fi

    #
    # If net.ipv6.conf.all.forwarding present in /etc/sysctl.conf, change value to appropriate value
    #	else, add "net.ipv6.conf.all.forwarding = value" to /etc/sysctl.conf
    #

    # Strip any search characters in the key arg so that the key can be replaced without
    # adding any search characters to the config file.
    stripped_key=$(sed 's/[\^=\$,;+]*//g' <<< "^net.ipv6.conf.all.forwarding")

    # shellcheck disable=SC2059
    printf -v formatted_output "%s = %s" "$stripped_key" "$sysctl_net_ipv6_conf_all_forwarding_value"

    # If the key exists, change it. Otherwise, add it to the config_file.
    # We search for the key string followed by a word boundary (matched by \>),
    # so if we search for 'setting', 'setting2' won't match.
    if LC_ALL=C grep -q -m 1 -i -e "^net.ipv6.conf.all.forwarding\\>" "${SYSCONFIG_FILE}"; then
        escaped_formatted_output=$(sed -e 's|/|\\/|g' <<< "$formatted_output")
        LC_ALL=C sed -i --follow-symlinks "s/^net.ipv6.conf.all.forwarding\\>.*/$escaped_formatted_output/gi" "${SYSCONFIG_FILE}"
    else
        if [[ -s "${SYSCONFIG_FILE}" ]] && [[ -n "$(tail -c 1 -- "${SYSCONFIG_FILE}" || true)" ]]; then
            LC_ALL=C sed -i --follow-symlinks '$a'\\ "${SYSCONFIG_FILE}"
        fi
        printf '%s\n' "$formatted_output" >> "${SYSCONFIG_FILE}"
    fi

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | medium
Reboot: | true
Strategy: | disable

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-6(b)
      - NIST-800-53-CM-6.1(iv)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_net_ipv6_conf_all_forwarding

    - name: List /etc/sysctl.d/*.conf files
      find:
        paths:
        - /etc/sysctl.d/
        - /run/sysctl.d/
        - /usr/local/lib/sysctl.d/
        contains: ^[\s]*net.ipv6.conf.all.forwarding.*$
        patterns: '*.conf'
        file_type: any
      register: find_sysctl_d
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-6(b)
      - NIST-800-53-CM-6.1(iv)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_net_ipv6_conf_all_forwarding

    - name: Comment out any occurrences of net.ipv6.conf.all.forwarding from config files
      replace:
        path: '{{ item.path }}'
        regexp: ^[\s]*net.ipv6.conf.all.forwarding
        replace: '#net.ipv6.conf.all.forwarding'
      loop: '{{ find_sysctl_d.files }}'
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-6(b)
      - NIST-800-53-CM-6.1(iv)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_net_ipv6_conf_all_forwarding
    - name: XCCDF Value sysctl_net_ipv6_conf_all_forwarding_value # promote to variable
      set_fact:
        sysctl_net_ipv6_conf_all_forwarding_value: !!str 0
      tags:
        - always

    - name: Ensure sysctl net.ipv6.conf.all.forwarding is set
      sysctl:
        name: net.ipv6.conf.all.forwarding
        value: '{{ sysctl_net_ipv6_conf_all_forwarding_value }}'
        sysctl_file: /etc/sysctl.conf
        state: present
        reload: true
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-6(b)
      - NIST-800-53-CM-6.1(iv)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_net_ipv6_conf_all_forwarding

#### Rule Disable Accepting Router Advertisements on all IPv6 Interfaces by Default [ref]

To set the runtime status of the `net.ipv6.conf.default.accept_ra` kernel parameter, run the following command:

    $ sudo sysctl -w net.ipv6.conf.default.accept_ra=0

To make sure that the setting is persistent, add the following line to a file in the directory `/etc/sysctl.d`:

    net.ipv6.conf.default.accept_ra = 0

Rationale: | An illicit router advertisement message could result in a man-in-the-middle attack.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_sysctl_net_ipv6_conf_default_accept_ra

References:

cis-csc | 11, 14, 3, 9
cobit5 | BAI10.01, BAI10.02, BAI10.03, BAI10.05, DSS05.02, DSS05.05, DSS06.06
cui | 3.1.20
disa | CCI-000366
isa-62443-2009 | 4.3.3.5.1, 4.3.3.5.2, 4.3.3.5.3, 4.3.3.5.4, 4.3.3.5.5, 4.3.3.5.6, 4.3.3.5.7, 4.3.3.5.8, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.1, 4.3.3.7.2, 4.3.3.7.3, 4.3.3.7.4, 4.3.4.3.2, 4.3.4.3.3
isa-62443-2013 | SR 1.1, SR 1.10, SR 1.11, SR 1.12, SR 1.13, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.6, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 2.2, SR 2.3, SR 2.4, SR 2.5, SR 2.6, SR 2.7, SR 7.6
iso27001-2013 | A.12.1.2, A.12.5.1, A.12.6.2, A.14.2.2, A.14.2.3, A.14.2.4, A.9.1.2
nist | CM-7(a), CM-7(b), CM-6(a)
nist-csf | PR.IP-1, PR.PT-3
os-srg | SRG-OS-000480-GPOS-00227
cis | 3.3.9

Remediation Shell script ⇲

Complexity: | low
Disruption: | medium
Reboot: | true
Strategy: | disable

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    # Comment out any occurrences of net.ipv6.conf.default.accept_ra from /etc/sysctl.d/*.conf files

    for f in /etc/sysctl.d/*.conf /run/sysctl.d/*.conf /usr/local/lib/sysctl.d/*.conf; do

      # skip systemd-sysctl symlink (/etc/sysctl.d/99-sysctl.conf -> /etc/sysctl.conf)
      if [[ "$(readlink -f "$f")" == "/etc/sysctl.conf" ]]; then continue; fi

      matching_list=$(grep -P '^(?!#).*[\s]*net.ipv6.conf.default.accept_ra.*$' $f | uniq )
      if ! test -z "$matching_list"; then
        while IFS= read -r entry; do
          escaped_entry=$(sed -e 's|/|\\/|g' <<< "$entry")
          # comment out "net.ipv6.conf.default.accept_ra" matches to preserve user data
          sed -i --follow-symlinks "s/^${escaped_entry}$/# &/g" $f
        done <<< "$matching_list"
      fi
    done

    #
    # Set sysctl config file which to save the desired value
    #

    SYSCONFIG_FILE="/etc/sysctl.conf"

    sysctl_net_ipv6_conf_default_accept_ra_value='0'

    #
    # Set runtime for net.ipv6.conf.default.accept_ra
    #
    if [[ "$OSCAP_BOOTC_BUILD" != "YES" ]] ; then
        /sbin/sysctl -q -n -w net.ipv6.conf.default.accept_ra="$sysctl_net_ipv6_conf_default_accept_ra_value"
    fi

    #
    # If net.ipv6.conf.default.accept_ra present in /etc/sysctl.conf, change value to appropriate value
    #	else, add "net.ipv6.conf.default.accept_ra = value" to /etc/sysctl.conf
    #

    # Strip any search characters in the key arg so that the key can be replaced without
    # adding any search characters to the config file.
    stripped_key=$(sed 's/[\^=\$,;+]*//g' <<< "^net.ipv6.conf.default.accept_ra")

    # shellcheck disable=SC2059
    printf -v formatted_output "%s = %s" "$stripped_key" "$sysctl_net_ipv6_conf_default_accept_ra_value"

    # If the key exists, change it. Otherwise, add it to the config_file.
    # We search for the key string followed by a word boundary (matched by \>),
    # so if we search for 'setting', 'setting2' won't match.
    if LC_ALL=C grep -q -m 1 -i -e "^net.ipv6.conf.default.accept_ra\\>" "${SYSCONFIG_FILE}"; then
        escaped_formatted_output=$(sed -e 's|/|\\/|g' <<< "$formatted_output")
        LC_ALL=C sed -i --follow-symlinks "s/^net.ipv6.conf.default.accept_ra\\>.*/$escaped_formatted_output/gi" "${SYSCONFIG_FILE}"
    else
        if [[ -s "${SYSCONFIG_FILE}" ]] && [[ -n "$(tail -c 1 -- "${SYSCONFIG_FILE}" || true)" ]]; then
            LC_ALL=C sed -i --follow-symlinks '$a'\\ "${SYSCONFIG_FILE}"
        fi
        printf '%s\n' "$formatted_output" >> "${SYSCONFIG_FILE}"
    fi

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | medium
Reboot: | true
Strategy: | disable

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_net_ipv6_conf_default_accept_ra

    - name: List /etc/sysctl.d/*.conf files
      find:
        paths:
        - /etc/sysctl.d/
        - /run/sysctl.d/
        - /usr/local/lib/sysctl.d/
        contains: ^[\s]*net.ipv6.conf.default.accept_ra.*$
        patterns: '*.conf'
        file_type: any
      register: find_sysctl_d
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_net_ipv6_conf_default_accept_ra

    - name: Comment out any occurrences of net.ipv6.conf.default.accept_ra from config
        files
      replace:
        path: '{{ item.path }}'
        regexp: ^[\s]*net.ipv6.conf.default.accept_ra
        replace: '#net.ipv6.conf.default.accept_ra'
      loop: '{{ find_sysctl_d.files }}'
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_net_ipv6_conf_default_accept_ra
    - name: XCCDF Value sysctl_net_ipv6_conf_default_accept_ra_value # promote to variable
      set_fact:
        sysctl_net_ipv6_conf_default_accept_ra_value: !!str 0
      tags:
        - always

    - name: Ensure sysctl net.ipv6.conf.default.accept_ra is set
      sysctl:
        name: net.ipv6.conf.default.accept_ra
        value: '{{ sysctl_net_ipv6_conf_default_accept_ra_value }}'
        sysctl_file: /etc/sysctl.conf
        state: present
        reload: true
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_net_ipv6_conf_default_accept_ra

#### Rule Disable Kernel Parameter for Accepting ICMP Redirects by Default on IPv6 Interfaces [ref]

To set the runtime status of the `net.ipv6.conf.default.accept_redirects` kernel parameter, run the following command:

    $ sudo sysctl -w net.ipv6.conf.default.accept_redirects=0

To make sure that the setting is persistent, add the following line to a file in the directory `/etc/sysctl.d`:

    net.ipv6.conf.default.accept_redirects = 0

Rationale: | An illicit ICMP redirect message could result in a man-in-the-middle attack.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_sysctl_net_ipv6_conf_default_accept_redirects

References:

cis-csc | 11, 14, 3, 9
cobit5 | BAI10.01, BAI10.02, BAI10.03, BAI10.05, DSS05.02, DSS05.05, DSS06.06
cui | 3.1.20
disa | CCI-000366
isa-62443-2009 | 4.3.3.5.1, 4.3.3.5.2, 4.3.3.5.3, 4.3.3.5.4, 4.3.3.5.5, 4.3.3.5.6, 4.3.3.5.7, 4.3.3.5.8, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.1, 4.3.3.7.2, 4.3.3.7.3, 4.3.3.7.4, 4.3.4.3.2, 4.3.4.3.3
isa-62443-2013 | SR 1.1, SR 1.10, SR 1.11, SR 1.12, SR 1.13, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.6, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 2.2, SR 2.3, SR 2.4, SR 2.5, SR 2.6, SR 2.7, SR 7.6
iso27001-2013 | A.12.1.2, A.12.5.1, A.12.6.2, A.14.2.2, A.14.2.3, A.14.2.4, A.9.1.2
nist | CM-7(a), CM-7(b), CM-6(a)
nist-csf | PR.IP-1, PR.PT-3
os-srg | SRG-OS-000480-GPOS-00227
cis | 3.3.2
anssi | R13

Remediation Shell script ⇲

Complexity: | low
Disruption: | medium
Reboot: | true
Strategy: | disable

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    # Comment out any occurrences of net.ipv6.conf.default.accept_redirects from /etc/sysctl.d/*.conf files

    for f in /etc/sysctl.d/*.conf /run/sysctl.d/*.conf /usr/local/lib/sysctl.d/*.conf; do

      # skip systemd-sysctl symlink (/etc/sysctl.d/99-sysctl.conf -> /etc/sysctl.conf)
      if [[ "$(readlink -f "$f")" == "/etc/sysctl.conf" ]]; then continue; fi

      matching_list=$(grep -P '^(?!#).*[\s]*net.ipv6.conf.default.accept_redirects.*$' $f | uniq )
      if ! test -z "$matching_list"; then
        while IFS= read -r entry; do
          escaped_entry=$(sed -e 's|/|\\/|g' <<< "$entry")
          # comment out "net.ipv6.conf.default.accept_redirects" matches to preserve user data
          sed -i --follow-symlinks "s/^${escaped_entry}$/# &/g" $f
        done <<< "$matching_list"
      fi
    done

    #
    # Set sysctl config file which to save the desired value
    #

    SYSCONFIG_FILE="/etc/sysctl.conf"

    sysctl_net_ipv6_conf_default_accept_redirects_value='0'

    #
    # Set runtime for net.ipv6.conf.default.accept_redirects
    #
    if [[ "$OSCAP_BOOTC_BUILD" != "YES" ]] ; then
        /sbin/sysctl -q -n -w net.ipv6.conf.default.accept_redirects="$sysctl_net_ipv6_conf_default_accept_redirects_value"
    fi

    #
    # If net.ipv6.conf.default.accept_redirects present in /etc/sysctl.conf, change value to appropriate value
    #	else, add "net.ipv6.conf.default.accept_redirects = value" to /etc/sysctl.conf
    #

    # Strip any search characters in the key arg so that the key can be replaced without
    # adding any search characters to the config file.
    stripped_key=$(sed 's/[\^=\$,;+]*//g' <<< "^net.ipv6.conf.default.accept_redirects")

    # shellcheck disable=SC2059
    printf -v formatted_output "%s = %s" "$stripped_key" "$sysctl_net_ipv6_conf_default_accept_redirects_value"

    # If the key exists, change it. Otherwise, add it to the config_file.
    # We search for the key string followed by a word boundary (matched by \>),
    # so if we search for 'setting', 'setting2' won't match.
    if LC_ALL=C grep -q -m 1 -i -e "^net.ipv6.conf.default.accept_redirects\\>" "${SYSCONFIG_FILE}"; then
        escaped_formatted_output=$(sed -e 's|/|\\/|g' <<< "$formatted_output")
        LC_ALL=C sed -i --follow-symlinks "s/^net.ipv6.conf.default.accept_redirects\\>.*/$escaped_formatted_output/gi" "${SYSCONFIG_FILE}"
    else
        if [[ -s "${SYSCONFIG_FILE}" ]] && [[ -n "$(tail -c 1 -- "${SYSCONFIG_FILE}" || true)" ]]; then
            LC_ALL=C sed -i --follow-symlinks '$a'\\ "${SYSCONFIG_FILE}"
        fi
        printf '%s\n' "$formatted_output" >> "${SYSCONFIG_FILE}"
    fi

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | medium
Reboot: | true
Strategy: | disable

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_net_ipv6_conf_default_accept_redirects

    - name: List /etc/sysctl.d/*.conf files
      find:
        paths:
        - /etc/sysctl.d/
        - /run/sysctl.d/
        - /usr/local/lib/sysctl.d/
        contains: ^[\s]*net.ipv6.conf.default.accept_redirects.*$
        patterns: '*.conf'
        file_type: any
      register: find_sysctl_d
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_net_ipv6_conf_default_accept_redirects

    - name: Comment out any occurrences of net.ipv6.conf.default.accept_redirects from
        config files
      replace:
        path: '{{ item.path }}'
        regexp: ^[\s]*net.ipv6.conf.default.accept_redirects
        replace: '#net.ipv6.conf.default.accept_redirects'
      loop: '{{ find_sysctl_d.files }}'
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_net_ipv6_conf_default_accept_redirects
    - name: XCCDF Value sysctl_net_ipv6_conf_default_accept_redirects_value # promote to variable
      set_fact:
        sysctl_net_ipv6_conf_default_accept_redirects_value: !!str 0
      tags:
        - always

    - name: Ensure sysctl net.ipv6.conf.default.accept_redirects is set
      sysctl:
        name: net.ipv6.conf.default.accept_redirects
        value: '{{ sysctl_net_ipv6_conf_default_accept_redirects_value }}'
        sysctl_file: /etc/sysctl.conf
        state: present
        reload: true
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_net_ipv6_conf_default_accept_redirects

#### Rule Disable Kernel Parameter for Accepting Source-Routed Packets on IPv6 Interfaces by Default [ref]

To set the runtime status of the `net.ipv6.conf.default.accept_source_route` kernel parameter, run the following command:

    $ sudo sysctl -w net.ipv6.conf.default.accept_source_route=0

To make sure that the setting is persistent, add the following line to a file in the directory `/etc/sysctl.d`:

    net.ipv6.conf.default.accept_source_route = 0

Rationale:

Source-routed packets allow the source of the packet to suggest routers forward the packet along a different path than configured on the router, which can be used to bypass network security measures. This requirement applies only to the forwarding of source-routerd traffic, such as when IPv6 forwarding is enabled and the system is functioning as a router. Accepting source-routed packets in the IPv6 protocol has few legitimate uses. It should be disabled unless it is absolutely required.

Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_sysctl_net_ipv6_conf_default_accept_source_route

References:

cis-csc | 1, 12, 13, 14, 15, 16, 18, 4, 6, 8, 9
cobit5 | APO01.06, APO13.01, DSS01.05, DSS03.01, DSS05.02, DSS05.04, DSS05.07, DSS06.02
cui | 3.1.20
disa | CCI-000366
isa-62443-2009 | 4.2.3.4, 4.3.3.4, 4.4.3.3
isa-62443-2013 | SR 3.1, SR 3.5, SR 3.8, SR 4.1, SR 4.3, SR 5.1, SR 5.2, SR 5.3, SR 7.1, SR 7.6
iso27001-2013 | A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.12.1.1, A.12.1.2, A.13.1.1, A.13.1.2, A.13.1.3, A.13.2.1, A.13.2.2, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, A.6.1.2, A.7.1.1, A.7.1.2, A.7.3.1, A.8.2.2, A.8.2.3, A.9.1.1, A.9.1.2, A.9.2.3, A.9.4.1, A.9.4.4, A.9.4.5
nist | CM-7(a), CM-7(b), CM-6(a), CM-6(b), CM-6.1(iv)
nist-csf | DE.AE-1, ID.AM-3, PR.AC-5, PR.DS-5, PR.PT-4
pcidss | Req-1.4.3
os-srg | SRG-OS-000480-GPOS-00227
cis | 3.3.1
anssi | R13
pcidss4 | 1.4.2, 1.4

Remediation Shell script ⇲

Complexity: | low
Disruption: | medium
Reboot: | true
Strategy: | disable

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    # Comment out any occurrences of net.ipv6.conf.default.accept_source_route from /etc/sysctl.d/*.conf files

    for f in /etc/sysctl.d/*.conf /run/sysctl.d/*.conf /usr/local/lib/sysctl.d/*.conf; do

      # skip systemd-sysctl symlink (/etc/sysctl.d/99-sysctl.conf -> /etc/sysctl.conf)
      if [[ "$(readlink -f "$f")" == "/etc/sysctl.conf" ]]; then continue; fi

      matching_list=$(grep -P '^(?!#).*[\s]*net.ipv6.conf.default.accept_source_route.*$' $f | uniq )
      if ! test -z "$matching_list"; then
        while IFS= read -r entry; do
          escaped_entry=$(sed -e 's|/|\\/|g' <<< "$entry")
          # comment out "net.ipv6.conf.default.accept_source_route" matches to preserve user data
          sed -i --follow-symlinks "s/^${escaped_entry}$/# &/g" $f
        done <<< "$matching_list"
      fi
    done

    #
    # Set sysctl config file which to save the desired value
    #

    SYSCONFIG_FILE="/etc/sysctl.conf"

    sysctl_net_ipv6_conf_default_accept_source_route_value='0'

    #
    # Set runtime for net.ipv6.conf.default.accept_source_route
    #
    if [[ "$OSCAP_BOOTC_BUILD" != "YES" ]] ; then
        /sbin/sysctl -q -n -w net.ipv6.conf.default.accept_source_route="$sysctl_net_ipv6_conf_default_accept_source_route_value"
    fi

    #
    # If net.ipv6.conf.default.accept_source_route present in /etc/sysctl.conf, change value to appropriate value
    #	else, add "net.ipv6.conf.default.accept_source_route = value" to /etc/sysctl.conf
    #

    # Strip any search characters in the key arg so that the key can be replaced without
    # adding any search characters to the config file.
    stripped_key=$(sed 's/[\^=\$,;+]*//g' <<< "^net.ipv6.conf.default.accept_source_route")

    # shellcheck disable=SC2059
    printf -v formatted_output "%s = %s" "$stripped_key" "$sysctl_net_ipv6_conf_default_accept_source_route_value"

    # If the key exists, change it. Otherwise, add it to the config_file.
    # We search for the key string followed by a word boundary (matched by \>),
    # so if we search for 'setting', 'setting2' won't match.
    if LC_ALL=C grep -q -m 1 -i -e "^net.ipv6.conf.default.accept_source_route\\>" "${SYSCONFIG_FILE}"; then
        escaped_formatted_output=$(sed -e 's|/|\\/|g' <<< "$formatted_output")
        LC_ALL=C sed -i --follow-symlinks "s/^net.ipv6.conf.default.accept_source_route\\>.*/$escaped_formatted_output/gi" "${SYSCONFIG_FILE}"
    else
        if [[ -s "${SYSCONFIG_FILE}" ]] && [[ -n "$(tail -c 1 -- "${SYSCONFIG_FILE}" || true)" ]]; then
            LC_ALL=C sed -i --follow-symlinks '$a'\\ "${SYSCONFIG_FILE}"
        fi
        printf '%s\n' "$formatted_output" >> "${SYSCONFIG_FILE}"
    fi

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | medium
Reboot: | true
Strategy: | disable

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-6(b)
      - NIST-800-53-CM-6.1(iv)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - PCI-DSS-Req-1.4.3
      - PCI-DSSv4-1.4
      - PCI-DSSv4-1.4.2
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_net_ipv6_conf_default_accept_source_route

    - name: List /etc/sysctl.d/*.conf files
      find:
        paths:
        - /etc/sysctl.d/
        - /run/sysctl.d/
        - /usr/local/lib/sysctl.d/
        contains: ^[\s]*net.ipv6.conf.default.accept_source_route.*$
        patterns: '*.conf'
        file_type: any
      register: find_sysctl_d
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-6(b)
      - NIST-800-53-CM-6.1(iv)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - PCI-DSS-Req-1.4.3
      - PCI-DSSv4-1.4
      - PCI-DSSv4-1.4.2
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_net_ipv6_conf_default_accept_source_route

    - name: Comment out any occurrences of net.ipv6.conf.default.accept_source_route from
        config files
      replace:
        path: '{{ item.path }}'
        regexp: ^[\s]*net.ipv6.conf.default.accept_source_route
        replace: '#net.ipv6.conf.default.accept_source_route'
      loop: '{{ find_sysctl_d.files }}'
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-6(b)
      - NIST-800-53-CM-6.1(iv)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - PCI-DSS-Req-1.4.3
      - PCI-DSSv4-1.4
      - PCI-DSSv4-1.4.2
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_net_ipv6_conf_default_accept_source_route
    - name: XCCDF Value sysctl_net_ipv6_conf_default_accept_source_route_value # promote to variable
      set_fact:
        sysctl_net_ipv6_conf_default_accept_source_route_value: !!str 0
      tags:
        - always

    - name: Ensure sysctl net.ipv6.conf.default.accept_source_route is set
      sysctl:
        name: net.ipv6.conf.default.accept_source_route
        value: '{{ sysctl_net_ipv6_conf_default_accept_source_route_value }}'
        sysctl_file: /etc/sysctl.conf
        state: present
        reload: true
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-6(b)
      - NIST-800-53-CM-6.1(iv)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - PCI-DSS-Req-1.4.3
      - PCI-DSSv4-1.4
      - PCI-DSSv4-1.4.2
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_net_ipv6_conf_default_accept_source_route

Group Kernel Parameters Which Affect Networking Group contains 2 groups and 16 rules
[ref] The `sysctl` utility is used to set parameters which affect the operation of the Linux kernel. Kernel parameters which affect networking and have security implications are described here.
Group Network Related Kernel Runtime Parameters for Hosts and Routers Group contains 13 rules
[ref] Certain kernel parameters should be set for systems which are acting as either hosts or routers to improve the system's ability defend against certain types of IPv4 protocol attacks.

#### Rule Disable Accepting ICMP Redirects for All IPv4 Interfaces [ref]

To set the runtime status of the `net.ipv4.conf.all.accept_redirects` kernel parameter, run the following command:

    $ sudo sysctl -w net.ipv4.conf.all.accept_redirects=0

To make sure that the setting is persistent, add the following line to a file in the directory `/etc/sysctl.d`:

    net.ipv4.conf.all.accept_redirects = 0

Rationale: | ICMP redirect messages are used by routers to inform hosts that a more direct route exists for a particular destination. These messages modify the host's route table and are unauthenticated. An illicit ICMP redirect message could result in a man-in-the-middle attack. This feature of the IPv4 protocol has few legitimate uses. It should be disabled unless absolutely required."
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_sysctl_net_ipv4_conf_all_accept_redirects

References:

cis-csc | 1, 11, 12, 13, 14, 15, 16, 2, 3, 7, 8, 9
cjis | 5.10.1.1
cobit5 | APO13.01, BAI04.04, BAI10.01, BAI10.02, BAI10.03, BAI10.05, DSS01.03, DSS03.05, DSS05.02, DSS05.05, DSS05.07, DSS06.06
cui | 3.1.20
disa | CCI-000366
isa-62443-2009 | 4.3.3.5.1, 4.3.3.5.2, 4.3.3.5.3, 4.3.3.5.4, 4.3.3.5.5, 4.3.3.5.6, 4.3.3.5.7, 4.3.3.5.8, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.1, 4.3.3.7.2, 4.3.3.7.3, 4.3.3.7.4, 4.3.4.3.2, 4.3.4.3.3
isa-62443-2013 | SR 1.1, SR 1.10, SR 1.11, SR 1.12, SR 1.13, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.6, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 2.2, SR 2.3, SR 2.4, SR 2.5, SR 2.6, SR 2.7, SR 6.2, SR 7.1, SR 7.2, SR 7.6
iso27001-2013 | A.12.1.2, A.12.1.3, A.12.5.1, A.12.6.2, A.14.2.2, A.14.2.3, A.14.2.4, A.17.2.1, A.9.1.2
nist | CM-7(a), CM-7(b), CM-6(a), SC-7(a)
nist-csf | DE.CM-1, PR.DS-4, PR.IP-1, PR.PT-3
os-srg | SRG-OS-000480-GPOS-00227
cis | 3.3.2
anssi | R12

Remediation Shell script ⇲

Complexity: | low
Disruption: | medium
Reboot: | true
Strategy: | disable

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    # Comment out any occurrences of net.ipv4.conf.all.accept_redirects from /etc/sysctl.d/*.conf files

    for f in /etc/sysctl.d/*.conf /run/sysctl.d/*.conf /usr/local/lib/sysctl.d/*.conf; do

      # skip systemd-sysctl symlink (/etc/sysctl.d/99-sysctl.conf -> /etc/sysctl.conf)
      if [[ "$(readlink -f "$f")" == "/etc/sysctl.conf" ]]; then continue; fi

      matching_list=$(grep -P '^(?!#).*[\s]*net.ipv4.conf.all.accept_redirects.*$' $f | uniq )
      if ! test -z "$matching_list"; then
        while IFS= read -r entry; do
          escaped_entry=$(sed -e 's|/|\\/|g' <<< "$entry")
          # comment out "net.ipv4.conf.all.accept_redirects" matches to preserve user data
          sed -i --follow-symlinks "s/^${escaped_entry}$/# &/g" $f
        done <<< "$matching_list"
      fi
    done

    #
    # Set sysctl config file which to save the desired value
    #

    SYSCONFIG_FILE="/etc/sysctl.conf"

    sysctl_net_ipv4_conf_all_accept_redirects_value='0'

    #
    # Set runtime for net.ipv4.conf.all.accept_redirects
    #
    if [[ "$OSCAP_BOOTC_BUILD" != "YES" ]] ; then
        /sbin/sysctl -q -n -w net.ipv4.conf.all.accept_redirects="$sysctl_net_ipv4_conf_all_accept_redirects_value"
    fi

    #
    # If net.ipv4.conf.all.accept_redirects present in /etc/sysctl.conf, change value to appropriate value
    #	else, add "net.ipv4.conf.all.accept_redirects = value" to /etc/sysctl.conf
    #

    # Strip any search characters in the key arg so that the key can be replaced without
    # adding any search characters to the config file.
    stripped_key=$(sed 's/[\^=\$,;+]*//g' <<< "^net.ipv4.conf.all.accept_redirects")

    # shellcheck disable=SC2059
    printf -v formatted_output "%s = %s" "$stripped_key" "$sysctl_net_ipv4_conf_all_accept_redirects_value"

    # If the key exists, change it. Otherwise, add it to the config_file.
    # We search for the key string followed by a word boundary (matched by \>),
    # so if we search for 'setting', 'setting2' won't match.
    if LC_ALL=C grep -q -m 1 -i -e "^net.ipv4.conf.all.accept_redirects\\>" "${SYSCONFIG_FILE}"; then
        escaped_formatted_output=$(sed -e 's|/|\\/|g' <<< "$formatted_output")
        LC_ALL=C sed -i --follow-symlinks "s/^net.ipv4.conf.all.accept_redirects\\>.*/$escaped_formatted_output/gi" "${SYSCONFIG_FILE}"
    else
        if [[ -s "${SYSCONFIG_FILE}" ]] && [[ -n "$(tail -c 1 -- "${SYSCONFIG_FILE}" || true)" ]]; then
            LC_ALL=C sed -i --follow-symlinks '$a'\\ "${SYSCONFIG_FILE}"
        fi
        printf '%s\n' "$formatted_output" >> "${SYSCONFIG_FILE}"
    fi

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | medium
Reboot: | true
Strategy: | disable

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - CJIS-5.10.1.1
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-SC-7(a)
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_net_ipv4_conf_all_accept_redirects

    - name: List /etc/sysctl.d/*.conf files
      find:
        paths:
        - /etc/sysctl.d/
        - /run/sysctl.d/
        - /usr/local/lib/sysctl.d/
        contains: ^[\s]*net.ipv4.conf.all.accept_redirects.*$
        patterns: '*.conf'
        file_type: any
      register: find_sysctl_d
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - CJIS-5.10.1.1
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-SC-7(a)
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_net_ipv4_conf_all_accept_redirects

    - name: Comment out any occurrences of net.ipv4.conf.all.accept_redirects from config
        files
      replace:
        path: '{{ item.path }}'
        regexp: ^[\s]*net.ipv4.conf.all.accept_redirects
        replace: '#net.ipv4.conf.all.accept_redirects'
      loop: '{{ find_sysctl_d.files }}'
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - CJIS-5.10.1.1
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-SC-7(a)
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_net_ipv4_conf_all_accept_redirects
    - name: XCCDF Value sysctl_net_ipv4_conf_all_accept_redirects_value # promote to variable
      set_fact:
        sysctl_net_ipv4_conf_all_accept_redirects_value: !!str 0
      tags:
        - always

    - name: Ensure sysctl net.ipv4.conf.all.accept_redirects is set
      sysctl:
        name: net.ipv4.conf.all.accept_redirects
        value: '{{ sysctl_net_ipv4_conf_all_accept_redirects_value }}'
        sysctl_file: /etc/sysctl.conf
        state: present
        reload: true
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - CJIS-5.10.1.1
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-SC-7(a)
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_net_ipv4_conf_all_accept_redirects

#### Rule Disable Kernel Parameter for Accepting Source-Routed Packets on all IPv4 Interfaces [ref]

To set the runtime status of the `net.ipv4.conf.all.accept_source_route` kernel parameter, run the following command:

    $ sudo sysctl -w net.ipv4.conf.all.accept_source_route=0

To make sure that the setting is persistent, add the following line to a file in the directory `/etc/sysctl.d`:

    net.ipv4.conf.all.accept_source_route = 0

Rationale:

Source-routed packets allow the source of the packet to suggest routers forward the packet along a different path than configured on the router, which can be used to bypass network security measures. This requirement applies only to the forwarding of source-routerd traffic, such as when IPv4 forwarding is enabled and the system is functioning as a router.
Accepting source-routed packets in the IPv4 protocol has few legitimate uses. It should be disabled unless it is absolutely required.

Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_sysctl_net_ipv4_conf_all_accept_source_route

References:

cis-csc | 1, 11, 12, 13, 14, 15, 16, 18, 2, 3, 4, 6, 7, 8, 9
cobit5 | APO01.06, APO13.01, BAI04.04, BAI10.01, BAI10.02, BAI10.03, BAI10.05, DSS01.03, DSS01.05, DSS03.01, DSS03.05, DSS05.02, DSS05.04, DSS05.05, DSS05.07, DSS06.02, DSS06.06
cui | 3.1.20
disa | CCI-000366
isa-62443-2009 | 4.2.3.4, 4.3.3.4, 4.3.3.5.1, 4.3.3.5.2, 4.3.3.5.3, 4.3.3.5.4, 4.3.3.5.5, 4.3.3.5.6, 4.3.3.5.7, 4.3.3.5.8, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.1, 4.3.3.7.2, 4.3.3.7.3, 4.3.3.7.4, 4.3.4.3.2, 4.3.4.3.3, 4.4.3.3
isa-62443-2013 | SR 1.1, SR 1.10, SR 1.11, SR 1.12, SR 1.13, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.6, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 2.2, SR 2.3, SR 2.4, SR 2.5, SR 2.6, SR 2.7, SR 3.1, SR 3.5, SR 3.8, SR 4.1, SR 4.3, SR 5.1, SR 5.2, SR 5.3, SR 6.2, SR 7.1, SR 7.2, SR 7.6
iso27001-2013 | A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.12.1.1, A.12.1.2, A.12.1.3, A.12.5.1, A.12.6.2, A.13.1.1, A.13.1.2, A.13.1.3, A.13.2.1, A.13.2.2, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, A.14.2.2, A.14.2.3, A.14.2.4, A.17.2.1, A.6.1.2, A.7.1.1, A.7.1.2, A.7.3.1, A.8.2.2, A.8.2.3, A.9.1.1, A.9.1.2, A.9.2.3, A.9.4.1, A.9.4.4, A.9.4.5
nerc-cip | CIP-007-3 R4, CIP-007-3 R4.1, CIP-007-3 R4.2, CIP-007-3 R5.1
nist | CM-7(a), CM-7(b), SC-5, CM-6(a), SC-7(a)
nist-csf | DE.AE-1, DE.CM-1, ID.AM-3, PR.AC-5, PR.DS-4, PR.DS-5, PR.IP-1, PR.PT-3, PR.PT-4
os-srg | SRG-OS-000480-GPOS-00227
cis | 3.3.1
anssi | R12

Remediation Shell script ⇲

Complexity: | low
Disruption: | medium
Reboot: | true
Strategy: | disable

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    # Comment out any occurrences of net.ipv4.conf.all.accept_source_route from /etc/sysctl.d/*.conf files

    for f in /etc/sysctl.d/*.conf /run/sysctl.d/*.conf /usr/local/lib/sysctl.d/*.conf; do

      # skip systemd-sysctl symlink (/etc/sysctl.d/99-sysctl.conf -> /etc/sysctl.conf)
      if [[ "$(readlink -f "$f")" == "/etc/sysctl.conf" ]]; then continue; fi

      matching_list=$(grep -P '^(?!#).*[\s]*net.ipv4.conf.all.accept_source_route.*$' $f | uniq )
      if ! test -z "$matching_list"; then
        while IFS= read -r entry; do
          escaped_entry=$(sed -e 's|/|\\/|g' <<< "$entry")
          # comment out "net.ipv4.conf.all.accept_source_route" matches to preserve user data
          sed -i --follow-symlinks "s/^${escaped_entry}$/# &/g" $f
        done <<< "$matching_list"
      fi
    done

    #
    # Set sysctl config file which to save the desired value
    #

    SYSCONFIG_FILE="/etc/sysctl.conf"

    sysctl_net_ipv4_conf_all_accept_source_route_value='0'

    #
    # Set runtime for net.ipv4.conf.all.accept_source_route
    #
    if [[ "$OSCAP_BOOTC_BUILD" != "YES" ]] ; then
        /sbin/sysctl -q -n -w net.ipv4.conf.all.accept_source_route="$sysctl_net_ipv4_conf_all_accept_source_route_value"
    fi

    #
    # If net.ipv4.conf.all.accept_source_route present in /etc/sysctl.conf, change value to appropriate value
    #	else, add "net.ipv4.conf.all.accept_source_route = value" to /etc/sysctl.conf
    #

    # Strip any search characters in the key arg so that the key can be replaced without
    # adding any search characters to the config file.
    stripped_key=$(sed 's/[\^=\$,;+]*//g' <<< "^net.ipv4.conf.all.accept_source_route")

    # shellcheck disable=SC2059
    printf -v formatted_output "%s = %s" "$stripped_key" "$sysctl_net_ipv4_conf_all_accept_source_route_value"

    # If the key exists, change it. Otherwise, add it to the config_file.
    # We search for the key string followed by a word boundary (matched by \>),
    # so if we search for 'setting', 'setting2' won't match.
    if LC_ALL=C grep -q -m 1 -i -e "^net.ipv4.conf.all.accept_source_route\\>" "${SYSCONFIG_FILE}"; then
        escaped_formatted_output=$(sed -e 's|/|\\/|g' <<< "$formatted_output")
        LC_ALL=C sed -i --follow-symlinks "s/^net.ipv4.conf.all.accept_source_route\\>.*/$escaped_formatted_output/gi" "${SYSCONFIG_FILE}"
    else
        if [[ -s "${SYSCONFIG_FILE}" ]] && [[ -n "$(tail -c 1 -- "${SYSCONFIG_FILE}" || true)" ]]; then
            LC_ALL=C sed -i --follow-symlinks '$a'\\ "${SYSCONFIG_FILE}"
        fi
        printf '%s\n' "$formatted_output" >> "${SYSCONFIG_FILE}"
    fi

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | medium
Reboot: | true
Strategy: | disable

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-SC-5
      - NIST-800-53-SC-7(a)
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_net_ipv4_conf_all_accept_source_route

    - name: List /etc/sysctl.d/*.conf files
      find:
        paths:
        - /etc/sysctl.d/
        - /run/sysctl.d/
        - /usr/local/lib/sysctl.d/
        contains: ^[\s]*net.ipv4.conf.all.accept_source_route.*$
        patterns: '*.conf'
        file_type: any
      register: find_sysctl_d
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-SC-5
      - NIST-800-53-SC-7(a)
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_net_ipv4_conf_all_accept_source_route

    - name: Comment out any occurrences of net.ipv4.conf.all.accept_source_route from
        config files
      replace:
        path: '{{ item.path }}'
        regexp: ^[\s]*net.ipv4.conf.all.accept_source_route
        replace: '#net.ipv4.conf.all.accept_source_route'
      loop: '{{ find_sysctl_d.files }}'
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-SC-5
      - NIST-800-53-SC-7(a)
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_net_ipv4_conf_all_accept_source_route
    - name: XCCDF Value sysctl_net_ipv4_conf_all_accept_source_route_value # promote to variable
      set_fact:
        sysctl_net_ipv4_conf_all_accept_source_route_value: !!str 0
      tags:
        - always

    - name: Ensure sysctl net.ipv4.conf.all.accept_source_route is set
      sysctl:
        name: net.ipv4.conf.all.accept_source_route
        value: '{{ sysctl_net_ipv4_conf_all_accept_source_route_value }}'
        sysctl_file: /etc/sysctl.conf
        state: present
        reload: true
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-SC-5
      - NIST-800-53-SC-7(a)
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_net_ipv4_conf_all_accept_source_route

#### Rule Enable Kernel Parameter to Log Martian Packets on all IPv4 Interfaces [ref]

To set the runtime status of the `net.ipv4.conf.all.log_martians` kernel parameter, run the following command:

    $ sudo sysctl -w net.ipv4.conf.all.log_martians=1

To make sure that the setting is persistent, add the following line to a file in the directory `/etc/sysctl.d`:

    net.ipv4.conf.all.log_martians = 1

Rationale: | The presence of "martian" packets (which have impossible addresses) as well as spoofed packets, source-routed packets, and redirects could be a sign of nefarious network activity. Logging these packets enables this activity to be detected.
Severity: | unknown
Rule ID: | xccdf_org.ssgproject.content_rule_sysctl_net_ipv4_conf_all_log_martians

References:

cis-csc | 1, 11, 12, 13, 14, 15, 16, 2, 3, 7, 8, 9
cobit5 | APO13.01, BAI04.04, BAI10.01, BAI10.02, BAI10.03, BAI10.05, DSS01.03, DSS01.04, DSS03.05, DSS05.02, DSS05.03, DSS05.05, DSS05.07, DSS06.06
cui | 3.1.20
disa | CCI-000366
isa-62443-2009 | 4.3.3.5.1, 4.3.3.5.2, 4.3.3.5.3, 4.3.3.5.4, 4.3.3.5.5, 4.3.3.5.6, 4.3.3.5.7, 4.3.3.5.8, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.1, 4.3.3.7.2, 4.3.3.7.3, 4.3.3.7.4, 4.3.4.3.2, 4.3.4.3.3
isa-62443-2013 | SR 1.1, SR 1.10, SR 1.11, SR 1.12, SR 1.13, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.6, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 2.2, SR 2.3, SR 2.4, SR 2.5, SR 2.6, SR 2.7, SR 3.1, SR 3.5, SR 3.8, SR 4.1, SR 4.3, SR 5.1, SR 5.2, SR 5.3, SR 6.2, SR 7.1, SR 7.2, SR 7.6
iso27001-2013 | A.11.2.6, A.12.1.2, A.12.1.3, A.12.5.1, A.12.6.2, A.13.1.1, A.13.2.1, A.14.1.3, A.14.2.2, A.14.2.3, A.14.2.4, A.17.2.1, A.6.2.1, A.6.2.2, A.9.1.2
nist | CM-7(a), CM-7(b), SC-5(3)(a)
nist-csf | DE.CM-1, PR.AC-3, PR.DS-4, PR.IP-1, PR.PT-3, PR.PT-4
os-srg | SRG-OS-000480-GPOS-00227
cis | 3.3.4

Remediation Shell script ⇲

Complexity: | low
Disruption: | medium
Reboot: | true
Strategy: | disable

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    # Comment out any occurrences of net.ipv4.conf.all.log_martians from /etc/sysctl.d/*.conf files

    for f in /etc/sysctl.d/*.conf /run/sysctl.d/*.conf /usr/local/lib/sysctl.d/*.conf; do

      # skip systemd-sysctl symlink (/etc/sysctl.d/99-sysctl.conf -> /etc/sysctl.conf)
      if [[ "$(readlink -f "$f")" == "/etc/sysctl.conf" ]]; then continue; fi

      matching_list=$(grep -P '^(?!#).*[\s]*net.ipv4.conf.all.log_martians.*$' $f | uniq )
      if ! test -z "$matching_list"; then
        while IFS= read -r entry; do
          escaped_entry=$(sed -e 's|/|\\/|g' <<< "$entry")
          # comment out "net.ipv4.conf.all.log_martians" matches to preserve user data
          sed -i --follow-symlinks "s/^${escaped_entry}$/# &/g" $f
        done <<< "$matching_list"
      fi
    done

    #
    # Set sysctl config file which to save the desired value
    #

    SYSCONFIG_FILE="/etc/sysctl.conf"

    sysctl_net_ipv4_conf_all_log_martians_value='1'

    #
    # Set runtime for net.ipv4.conf.all.log_martians
    #
    if [[ "$OSCAP_BOOTC_BUILD" != "YES" ]] ; then
        /sbin/sysctl -q -n -w net.ipv4.conf.all.log_martians="$sysctl_net_ipv4_conf_all_log_martians_value"
    fi

    #
    # If net.ipv4.conf.all.log_martians present in /etc/sysctl.conf, change value to appropriate value
    #	else, add "net.ipv4.conf.all.log_martians = value" to /etc/sysctl.conf
    #

    # Strip any search characters in the key arg so that the key can be replaced without
    # adding any search characters to the config file.
    stripped_key=$(sed 's/[\^=\$,;+]*//g' <<< "^net.ipv4.conf.all.log_martians")

    # shellcheck disable=SC2059
    printf -v formatted_output "%s = %s" "$stripped_key" "$sysctl_net_ipv4_conf_all_log_martians_value"

    # If the key exists, change it. Otherwise, add it to the config_file.
    # We search for the key string followed by a word boundary (matched by \>),
    # so if we search for 'setting', 'setting2' won't match.
    if LC_ALL=C grep -q -m 1 -i -e "^net.ipv4.conf.all.log_martians\\>" "${SYSCONFIG_FILE}"; then
        escaped_formatted_output=$(sed -e 's|/|\\/|g' <<< "$formatted_output")
        LC_ALL=C sed -i --follow-symlinks "s/^net.ipv4.conf.all.log_martians\\>.*/$escaped_formatted_output/gi" "${SYSCONFIG_FILE}"
    else
        if [[ -s "${SYSCONFIG_FILE}" ]] && [[ -n "$(tail -c 1 -- "${SYSCONFIG_FILE}" || true)" ]]; then
            LC_ALL=C sed -i --follow-symlinks '$a'\\ "${SYSCONFIG_FILE}"
        fi
        printf '%s\n' "$formatted_output" >> "${SYSCONFIG_FILE}"
    fi

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | medium
Reboot: | true
Strategy: | disable

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-SC-5(3)(a)
      - disable_strategy
      - low_complexity
      - medium_disruption
      - reboot_required
      - sysctl_net_ipv4_conf_all_log_martians
      - unknown_severity

    - name: List /etc/sysctl.d/*.conf files
      find:
        paths:
        - /etc/sysctl.d/
        - /run/sysctl.d/
        - /usr/local/lib/sysctl.d/
        contains: ^[\s]*net.ipv4.conf.all.log_martians.*$
        patterns: '*.conf'
        file_type: any
      register: find_sysctl_d
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-SC-5(3)(a)
      - disable_strategy
      - low_complexity
      - medium_disruption
      - reboot_required
      - sysctl_net_ipv4_conf_all_log_martians
      - unknown_severity

    - name: Comment out any occurrences of net.ipv4.conf.all.log_martians from config
        files
      replace:
        path: '{{ item.path }}'
        regexp: ^[\s]*net.ipv4.conf.all.log_martians
        replace: '#net.ipv4.conf.all.log_martians'
      loop: '{{ find_sysctl_d.files }}'
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-SC-5(3)(a)
      - disable_strategy
      - low_complexity
      - medium_disruption
      - reboot_required
      - sysctl_net_ipv4_conf_all_log_martians
      - unknown_severity
    - name: XCCDF Value sysctl_net_ipv4_conf_all_log_martians_value # promote to variable
      set_fact:
        sysctl_net_ipv4_conf_all_log_martians_value: !!str 1
      tags:
        - always

    - name: Ensure sysctl net.ipv4.conf.all.log_martians is set
      sysctl:
        name: net.ipv4.conf.all.log_martians
        value: '{{ sysctl_net_ipv4_conf_all_log_martians_value }}'
        sysctl_file: /etc/sysctl.conf
        state: present
        reload: true
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-SC-5(3)(a)
      - disable_strategy
      - low_complexity
      - medium_disruption
      - reboot_required
      - sysctl_net_ipv4_conf_all_log_martians
      - unknown_severity

#### Rule Enable Kernel Parameter to Use Reverse Path Filtering on all IPv4 Interfaces [ref]

To set the runtime status of the `net.ipv4.conf.all.rp_filter` kernel parameter, run the following command:

    $ sudo sysctl -w net.ipv4.conf.all.rp_filter=1

To make sure that the setting is persistent, add the following line to a file in the directory `/etc/sysctl.d`:

    net.ipv4.conf.all.rp_filter = 1

Rationale: | Enabling reverse path filtering drops packets with source addresses that should not have been able to be received on the interface they were received on. It should not be used on systems which are routers for complicated networks, but is helpful for end hosts and routers serving small networks.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_sysctl_net_ipv4_conf_all_rp_filter

References:

cis-csc | 1, 12, 13, 14, 15, 16, 18, 2, 4, 6, 7, 8, 9
cobit5 | APO01.06, APO13.01, BAI04.04, DSS01.03, DSS01.05, DSS03.01, DSS03.05, DSS05.02, DSS05.04, DSS05.07, DSS06.02
cui | 3.1.20
disa | CCI-000366
isa-62443-2009 | 4.2.3.4, 4.3.3.4, 4.4.3.3
isa-62443-2013 | SR 3.1, SR 3.5, SR 3.8, SR 4.1, SR 4.3, SR 5.1, SR 5.2, SR 5.3, SR 6.2, SR 7.1, SR 7.2, SR 7.6
iso27001-2013 | A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.12.1.1, A.12.1.2, A.12.1.3, A.13.1.1, A.13.1.2, A.13.1.3, A.13.2.1, A.13.2.2, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, A.17.2.1, A.6.1.2, A.7.1.1, A.7.1.2, A.7.3.1, A.8.2.2, A.8.2.3, A.9.1.1, A.9.1.2, A.9.2.3, A.9.4.1, A.9.4.4, A.9.4.5
nist | CM-7(a), CM-7(b), CM-6(a), SC-7(a)
nist-csf | DE.AE-1, DE.CM-1, ID.AM-3, PR.AC-5, PR.DS-4, PR.DS-5, PR.PT-4
pcidss | Req-1.4.3
os-srg | SRG-OS-000480-GPOS-00227
cis | 3.3.7
anssi | R12
pcidss4 | 1.4.3, 1.4

Remediation Shell script ⇲

Complexity: | low
Disruption: | medium
Reboot: | true
Strategy: | disable

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    # Comment out any occurrences of net.ipv4.conf.all.rp_filter from /etc/sysctl.d/*.conf files

    for f in /etc/sysctl.d/*.conf /run/sysctl.d/*.conf /usr/local/lib/sysctl.d/*.conf; do

      # skip systemd-sysctl symlink (/etc/sysctl.d/99-sysctl.conf -> /etc/sysctl.conf)
      if [[ "$(readlink -f "$f")" == "/etc/sysctl.conf" ]]; then continue; fi

      matching_list=$(grep -P '^(?!#).*[\s]*net.ipv4.conf.all.rp_filter.*$' $f | uniq )
      if ! test -z "$matching_list"; then
        while IFS= read -r entry; do
          escaped_entry=$(sed -e 's|/|\\/|g' <<< "$entry")
          # comment out "net.ipv4.conf.all.rp_filter" matches to preserve user data
          sed -i --follow-symlinks "s/^${escaped_entry}$/# &/g" $f
        done <<< "$matching_list"
      fi
    done

    #
    # Set sysctl config file which to save the desired value
    #

    SYSCONFIG_FILE="/etc/sysctl.conf"

    sysctl_net_ipv4_conf_all_rp_filter_value='1'

    #
    # Set runtime for net.ipv4.conf.all.rp_filter
    #
    if [[ "$OSCAP_BOOTC_BUILD" != "YES" ]] ; then
        /sbin/sysctl -q -n -w net.ipv4.conf.all.rp_filter="$sysctl_net_ipv4_conf_all_rp_filter_value"
    fi

    #
    # If net.ipv4.conf.all.rp_filter present in /etc/sysctl.conf, change value to appropriate value
    #	else, add "net.ipv4.conf.all.rp_filter = value" to /etc/sysctl.conf
    #

    # Strip any search characters in the key arg so that the key can be replaced without
    # adding any search characters to the config file.
    stripped_key=$(sed 's/[\^=\$,;+]*//g' <<< "^net.ipv4.conf.all.rp_filter")

    # shellcheck disable=SC2059
    printf -v formatted_output "%s = %s" "$stripped_key" "$sysctl_net_ipv4_conf_all_rp_filter_value"

    # If the key exists, change it. Otherwise, add it to the config_file.
    # We search for the key string followed by a word boundary (matched by \>),
    # so if we search for 'setting', 'setting2' won't match.
    if LC_ALL=C grep -q -m 1 -i -e "^net.ipv4.conf.all.rp_filter\\>" "${SYSCONFIG_FILE}"; then
        escaped_formatted_output=$(sed -e 's|/|\\/|g' <<< "$formatted_output")
        LC_ALL=C sed -i --follow-symlinks "s/^net.ipv4.conf.all.rp_filter\\>.*/$escaped_formatted_output/gi" "${SYSCONFIG_FILE}"
    else
        if [[ -s "${SYSCONFIG_FILE}" ]] && [[ -n "$(tail -c 1 -- "${SYSCONFIG_FILE}" || true)" ]]; then
            LC_ALL=C sed -i --follow-symlinks '$a'\\ "${SYSCONFIG_FILE}"
        fi
        printf '%s\n' "$formatted_output" >> "${SYSCONFIG_FILE}"
    fi

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | medium
Reboot: | true
Strategy: | disable

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-SC-7(a)
      - PCI-DSS-Req-1.4.3
      - PCI-DSSv4-1.4
      - PCI-DSSv4-1.4.3
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_net_ipv4_conf_all_rp_filter

    - name: List /etc/sysctl.d/*.conf files
      find:
        paths:
        - /etc/sysctl.d/
        - /run/sysctl.d/
        - /usr/local/lib/sysctl.d/
        contains: ^[\s]*net.ipv4.conf.all.rp_filter.*$
        patterns: '*.conf'
        file_type: any
      register: find_sysctl_d
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-SC-7(a)
      - PCI-DSS-Req-1.4.3
      - PCI-DSSv4-1.4
      - PCI-DSSv4-1.4.3
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_net_ipv4_conf_all_rp_filter

    - name: Comment out any occurrences of net.ipv4.conf.all.rp_filter from config files
      replace:
        path: '{{ item.path }}'
        regexp: ^[\s]*net.ipv4.conf.all.rp_filter
        replace: '#net.ipv4.conf.all.rp_filter'
      loop: '{{ find_sysctl_d.files }}'
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-SC-7(a)
      - PCI-DSS-Req-1.4.3
      - PCI-DSSv4-1.4
      - PCI-DSSv4-1.4.3
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_net_ipv4_conf_all_rp_filter
    - name: XCCDF Value sysctl_net_ipv4_conf_all_rp_filter_value # promote to variable
      set_fact:
        sysctl_net_ipv4_conf_all_rp_filter_value: !!str 1
      tags:
        - always

    - name: Ensure sysctl net.ipv4.conf.all.rp_filter is set
      sysctl:
        name: net.ipv4.conf.all.rp_filter
        value: '{{ sysctl_net_ipv4_conf_all_rp_filter_value }}'
        sysctl_file: /etc/sysctl.conf
        state: present
        reload: true
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-SC-7(a)
      - PCI-DSS-Req-1.4.3
      - PCI-DSSv4-1.4
      - PCI-DSSv4-1.4.3
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_net_ipv4_conf_all_rp_filter

#### Rule Disable Kernel Parameter for Accepting Secure ICMP Redirects on all IPv4 Interfaces [ref]

To set the runtime status of the `net.ipv4.conf.all.secure_redirects` kernel parameter, run the following command:

    $ sudo sysctl -w net.ipv4.conf.all.secure_redirects=0

To make sure that the setting is persistent, add the following line to a file in the directory `/etc/sysctl.d`:

    net.ipv4.conf.all.secure_redirects = 0

Rationale: | Accepting "secure" ICMP redirects (from those gateways listed as default gateways) has few legitimate uses. It should be disabled unless it is absolutely required.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_sysctl_net_ipv4_conf_all_secure_redirects

References:

cis-csc | 1, 11, 12, 13, 14, 15, 16, 18, 2, 3, 4, 6, 7, 8, 9
cobit5 | APO01.06, APO13.01, BAI04.04, BAI10.01, BAI10.02, BAI10.03, BAI10.05, DSS01.03, DSS01.05, DSS03.01, DSS03.05, DSS05.02, DSS05.04, DSS05.05, DSS05.07, DSS06.02, DSS06.06
cui | 3.1.20
disa | CCI-001503, CCI-001551
isa-62443-2009 | 4.2.3.4, 4.3.3.4, 4.3.3.5.1, 4.3.3.5.2, 4.3.3.5.3, 4.3.3.5.4, 4.3.3.5.5, 4.3.3.5.6, 4.3.3.5.7, 4.3.3.5.8, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.1, 4.3.3.7.2, 4.3.3.7.3, 4.3.3.7.4, 4.3.4.3.2, 4.3.4.3.3, 4.4.3.3
isa-62443-2013 | SR 1.1, SR 1.10, SR 1.11, SR 1.12, SR 1.13, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.6, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 2.2, SR 2.3, SR 2.4, SR 2.5, SR 2.6, SR 2.7, SR 3.1, SR 3.5, SR 3.8, SR 4.1, SR 4.3, SR 5.1, SR 5.2, SR 5.3, SR 6.2, SR 7.1, SR 7.2, SR 7.6
iso27001-2013 | A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.12.1.1, A.12.1.2, A.12.1.3, A.12.5.1, A.12.6.2, A.13.1.1, A.13.1.2, A.13.1.3, A.13.2.1, A.13.2.2, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, A.14.2.2, A.14.2.3, A.14.2.4, A.17.2.1, A.6.1.2, A.7.1.1, A.7.1.2, A.7.3.1, A.8.2.2, A.8.2.3, A.9.1.1, A.9.1.2, A.9.2.3, A.9.4.1, A.9.4.4, A.9.4.5
nist | CM-7(a), CM-7(b), CM-6(a), SC-7(a)
nist-csf | DE.AE-1, DE.CM-1, ID.AM-3, PR.AC-5, PR.DS-4, PR.DS-5, PR.IP-1, PR.PT-3, PR.PT-4
pcidss | Req-1.4.3
os-srg | SRG-OS-000480-GPOS-00227
cis | 3.3.3
anssi | R12
pcidss4 | 1.4.3, 1.4

Remediation Shell script ⇲

Complexity: | low
Disruption: | medium
Reboot: | true
Strategy: | disable

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    # Comment out any occurrences of net.ipv4.conf.all.secure_redirects from /etc/sysctl.d/*.conf files

    for f in /etc/sysctl.d/*.conf /run/sysctl.d/*.conf /usr/local/lib/sysctl.d/*.conf; do

      # skip systemd-sysctl symlink (/etc/sysctl.d/99-sysctl.conf -> /etc/sysctl.conf)
      if [[ "$(readlink -f "$f")" == "/etc/sysctl.conf" ]]; then continue; fi

      matching_list=$(grep -P '^(?!#).*[\s]*net.ipv4.conf.all.secure_redirects.*$' $f | uniq )
      if ! test -z "$matching_list"; then
        while IFS= read -r entry; do
          escaped_entry=$(sed -e 's|/|\\/|g' <<< "$entry")
          # comment out "net.ipv4.conf.all.secure_redirects" matches to preserve user data
          sed -i --follow-symlinks "s/^${escaped_entry}$/# &/g" $f
        done <<< "$matching_list"
      fi
    done

    #
    # Set sysctl config file which to save the desired value
    #

    SYSCONFIG_FILE="/etc/sysctl.conf"

    sysctl_net_ipv4_conf_all_secure_redirects_value='0'

    #
    # Set runtime for net.ipv4.conf.all.secure_redirects
    #
    if [[ "$OSCAP_BOOTC_BUILD" != "YES" ]] ; then
        /sbin/sysctl -q -n -w net.ipv4.conf.all.secure_redirects="$sysctl_net_ipv4_conf_all_secure_redirects_value"
    fi

    #
    # If net.ipv4.conf.all.secure_redirects present in /etc/sysctl.conf, change value to appropriate value
    #	else, add "net.ipv4.conf.all.secure_redirects = value" to /etc/sysctl.conf
    #

    # Strip any search characters in the key arg so that the key can be replaced without
    # adding any search characters to the config file.
    stripped_key=$(sed 's/[\^=\$,;+]*//g' <<< "^net.ipv4.conf.all.secure_redirects")

    # shellcheck disable=SC2059
    printf -v formatted_output "%s = %s" "$stripped_key" "$sysctl_net_ipv4_conf_all_secure_redirects_value"

    # If the key exists, change it. Otherwise, add it to the config_file.
    # We search for the key string followed by a word boundary (matched by \>),
    # so if we search for 'setting', 'setting2' won't match.
    if LC_ALL=C grep -q -m 1 -i -e "^net.ipv4.conf.all.secure_redirects\\>" "${SYSCONFIG_FILE}"; then
        escaped_formatted_output=$(sed -e 's|/|\\/|g' <<< "$formatted_output")
        LC_ALL=C sed -i --follow-symlinks "s/^net.ipv4.conf.all.secure_redirects\\>.*/$escaped_formatted_output/gi" "${SYSCONFIG_FILE}"
    else
        if [[ -s "${SYSCONFIG_FILE}" ]] && [[ -n "$(tail -c 1 -- "${SYSCONFIG_FILE}" || true)" ]]; then
            LC_ALL=C sed -i --follow-symlinks '$a'\\ "${SYSCONFIG_FILE}"
        fi
        printf '%s\n' "$formatted_output" >> "${SYSCONFIG_FILE}"
    fi

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | medium
Reboot: | true
Strategy: | disable

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-SC-7(a)
      - PCI-DSS-Req-1.4.3
      - PCI-DSSv4-1.4
      - PCI-DSSv4-1.4.3
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_net_ipv4_conf_all_secure_redirects

    - name: List /etc/sysctl.d/*.conf files
      find:
        paths:
        - /etc/sysctl.d/
        - /run/sysctl.d/
        - /usr/local/lib/sysctl.d/
        contains: ^[\s]*net.ipv4.conf.all.secure_redirects.*$
        patterns: '*.conf'
        file_type: any
      register: find_sysctl_d
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-SC-7(a)
      - PCI-DSS-Req-1.4.3
      - PCI-DSSv4-1.4
      - PCI-DSSv4-1.4.3
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_net_ipv4_conf_all_secure_redirects

    - name: Comment out any occurrences of net.ipv4.conf.all.secure_redirects from config
        files
      replace:
        path: '{{ item.path }}'
        regexp: ^[\s]*net.ipv4.conf.all.secure_redirects
        replace: '#net.ipv4.conf.all.secure_redirects'
      loop: '{{ find_sysctl_d.files }}'
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-SC-7(a)
      - PCI-DSS-Req-1.4.3
      - PCI-DSSv4-1.4
      - PCI-DSSv4-1.4.3
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_net_ipv4_conf_all_secure_redirects
    - name: XCCDF Value sysctl_net_ipv4_conf_all_secure_redirects_value # promote to variable
      set_fact:
        sysctl_net_ipv4_conf_all_secure_redirects_value: !!str 0
      tags:
        - always

    - name: Ensure sysctl net.ipv4.conf.all.secure_redirects is set
      sysctl:
        name: net.ipv4.conf.all.secure_redirects
        value: '{{ sysctl_net_ipv4_conf_all_secure_redirects_value }}'
        sysctl_file: /etc/sysctl.conf
        state: present
        reload: true
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-SC-7(a)
      - PCI-DSS-Req-1.4.3
      - PCI-DSSv4-1.4
      - PCI-DSSv4-1.4.3
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_net_ipv4_conf_all_secure_redirects

#### Rule Disable Kernel Parameter for Accepting ICMP Redirects by Default on IPv4 Interfaces [ref]

To set the runtime status of the `net.ipv4.conf.default.accept_redirects` kernel parameter, run the following command:

    $ sudo sysctl -w net.ipv4.conf.default.accept_redirects=0

To make sure that the setting is persistent, add the following line to a file in the directory `/etc/sysctl.d`:

    net.ipv4.conf.default.accept_redirects = 0

Rationale: | ICMP redirect messages are used by routers to inform hosts that a more direct route exists for a particular destination. These messages modify the host's route table and are unauthenticated. An illicit ICMP redirect message could result in a man-in-the-middle attack. This feature of the IPv4 protocol has few legitimate uses. It should be disabled unless absolutely required.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_sysctl_net_ipv4_conf_default_accept_redirects

References:

cis-csc | 1, 11, 12, 13, 14, 15, 16, 18, 2, 3, 4, 6, 7, 8, 9
cjis | 5.10.1.1
cobit5 | APO01.06, APO13.01, BAI04.04, BAI10.01, BAI10.02, BAI10.03, BAI10.05, DSS01.03, DSS01.05, DSS03.01, DSS03.05, DSS05.02, DSS05.04, DSS05.05, DSS05.07, DSS06.02, DSS06.06
cui | 3.1.20
disa | CCI-000366
isa-62443-2009 | 4.2.3.4, 4.3.3.4, 4.3.3.5.1, 4.3.3.5.2, 4.3.3.5.3, 4.3.3.5.4, 4.3.3.5.5, 4.3.3.5.6, 4.3.3.5.7, 4.3.3.5.8, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.1, 4.3.3.7.2, 4.3.3.7.3, 4.3.3.7.4, 4.3.4.3.2, 4.3.4.3.3, 4.4.3.3
isa-62443-2013 | SR 1.1, SR 1.10, SR 1.11, SR 1.12, SR 1.13, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.6, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 2.2, SR 2.3, SR 2.4, SR 2.5, SR 2.6, SR 2.7, SR 3.1, SR 3.5, SR 3.8, SR 4.1, SR 4.3, SR 5.1, SR 5.2, SR 5.3, SR 6.2, SR 7.1, SR 7.2, SR 7.6
iso27001-2013 | A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.12.1.1, A.12.1.2, A.12.1.3, A.12.5.1, A.12.6.2, A.13.1.1, A.13.1.2, A.13.1.3, A.13.2.1, A.13.2.2, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, A.14.2.2, A.14.2.3, A.14.2.4, A.17.2.1, A.6.1.2, A.7.1.1, A.7.1.2, A.7.3.1, A.8.2.2, A.8.2.3, A.9.1.1, A.9.1.2, A.9.2.3, A.9.4.1, A.9.4.4, A.9.4.5
nist | CM-7(a), CM-7(b), CM-6(a), SC-7(a)
nist-csf | DE.AE-1, DE.CM-1, ID.AM-3, PR.AC-5, PR.DS-4, PR.DS-5, PR.IP-1, PR.PT-3, PR.PT-4
pcidss | Req-1.4.3
os-srg | SRG-OS-000480-GPOS-00227
cis | 3.3.2
anssi | R12
pcidss4 | 1.4.3, 1.4

Remediation Shell script ⇲

Complexity: | low
Disruption: | medium
Reboot: | true
Strategy: | disable

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    # Comment out any occurrences of net.ipv4.conf.default.accept_redirects from /etc/sysctl.d/*.conf files

    for f in /etc/sysctl.d/*.conf /run/sysctl.d/*.conf /usr/local/lib/sysctl.d/*.conf; do

      # skip systemd-sysctl symlink (/etc/sysctl.d/99-sysctl.conf -> /etc/sysctl.conf)
      if [[ "$(readlink -f "$f")" == "/etc/sysctl.conf" ]]; then continue; fi

      matching_list=$(grep -P '^(?!#).*[\s]*net.ipv4.conf.default.accept_redirects.*$' $f | uniq )
      if ! test -z "$matching_list"; then
        while IFS= read -r entry; do
          escaped_entry=$(sed -e 's|/|\\/|g' <<< "$entry")
          # comment out "net.ipv4.conf.default.accept_redirects" matches to preserve user data
          sed -i --follow-symlinks "s/^${escaped_entry}$/# &/g" $f
        done <<< "$matching_list"
      fi
    done

    #
    # Set sysctl config file which to save the desired value
    #

    SYSCONFIG_FILE="/etc/sysctl.conf"

    sysctl_net_ipv4_conf_default_accept_redirects_value='0'

    #
    # Set runtime for net.ipv4.conf.default.accept_redirects
    #
    if [[ "$OSCAP_BOOTC_BUILD" != "YES" ]] ; then
        /sbin/sysctl -q -n -w net.ipv4.conf.default.accept_redirects="$sysctl_net_ipv4_conf_default_accept_redirects_value"
    fi

    #
    # If net.ipv4.conf.default.accept_redirects present in /etc/sysctl.conf, change value to appropriate value
    #	else, add "net.ipv4.conf.default.accept_redirects = value" to /etc/sysctl.conf
    #

    # Strip any search characters in the key arg so that the key can be replaced without
    # adding any search characters to the config file.
    stripped_key=$(sed 's/[\^=\$,;+]*//g' <<< "^net.ipv4.conf.default.accept_redirects")

    # shellcheck disable=SC2059
    printf -v formatted_output "%s = %s" "$stripped_key" "$sysctl_net_ipv4_conf_default_accept_redirects_value"

    # If the key exists, change it. Otherwise, add it to the config_file.
    # We search for the key string followed by a word boundary (matched by \>),
    # so if we search for 'setting', 'setting2' won't match.
    if LC_ALL=C grep -q -m 1 -i -e "^net.ipv4.conf.default.accept_redirects\\>" "${SYSCONFIG_FILE}"; then
        escaped_formatted_output=$(sed -e 's|/|\\/|g' <<< "$formatted_output")
        LC_ALL=C sed -i --follow-symlinks "s/^net.ipv4.conf.default.accept_redirects\\>.*/$escaped_formatted_output/gi" "${SYSCONFIG_FILE}"
    else
        if [[ -s "${SYSCONFIG_FILE}" ]] && [[ -n "$(tail -c 1 -- "${SYSCONFIG_FILE}" || true)" ]]; then
            LC_ALL=C sed -i --follow-symlinks '$a'\\ "${SYSCONFIG_FILE}"
        fi
        printf '%s\n' "$formatted_output" >> "${SYSCONFIG_FILE}"
    fi

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | medium
Reboot: | true
Strategy: | disable

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - CJIS-5.10.1.1
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-SC-7(a)
      - PCI-DSS-Req-1.4.3
      - PCI-DSSv4-1.4
      - PCI-DSSv4-1.4.3
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_net_ipv4_conf_default_accept_redirects

    - name: List /etc/sysctl.d/*.conf files
      find:
        paths:
        - /etc/sysctl.d/
        - /run/sysctl.d/
        - /usr/local/lib/sysctl.d/
        contains: ^[\s]*net.ipv4.conf.default.accept_redirects.*$
        patterns: '*.conf'
        file_type: any
      register: find_sysctl_d
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - CJIS-5.10.1.1
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-SC-7(a)
      - PCI-DSS-Req-1.4.3
      - PCI-DSSv4-1.4
      - PCI-DSSv4-1.4.3
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_net_ipv4_conf_default_accept_redirects

    - name: Comment out any occurrences of net.ipv4.conf.default.accept_redirects from
        config files
      replace:
        path: '{{ item.path }}'
        regexp: ^[\s]*net.ipv4.conf.default.accept_redirects
        replace: '#net.ipv4.conf.default.accept_redirects'
      loop: '{{ find_sysctl_d.files }}'
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - CJIS-5.10.1.1
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-SC-7(a)
      - PCI-DSS-Req-1.4.3
      - PCI-DSSv4-1.4
      - PCI-DSSv4-1.4.3
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_net_ipv4_conf_default_accept_redirects
    - name: XCCDF Value sysctl_net_ipv4_conf_default_accept_redirects_value # promote to variable
      set_fact:
        sysctl_net_ipv4_conf_default_accept_redirects_value: !!str 0
      tags:
        - always

    - name: Ensure sysctl net.ipv4.conf.default.accept_redirects is set
      sysctl:
        name: net.ipv4.conf.default.accept_redirects
        value: '{{ sysctl_net_ipv4_conf_default_accept_redirects_value }}'
        sysctl_file: /etc/sysctl.conf
        state: present
        reload: true
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - CJIS-5.10.1.1
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-SC-7(a)
      - PCI-DSS-Req-1.4.3
      - PCI-DSSv4-1.4
      - PCI-DSSv4-1.4.3
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_net_ipv4_conf_default_accept_redirects

#### Rule Disable Kernel Parameter for Accepting Source-Routed Packets on IPv4 Interfaces by Default [ref]

To set the runtime status of the `net.ipv4.conf.default.accept_source_route` kernel parameter, run the following command:

    $ sudo sysctl -w net.ipv4.conf.default.accept_source_route=0

To make sure that the setting is persistent, add the following line to a file in the directory `/etc/sysctl.d`:

    net.ipv4.conf.default.accept_source_route = 0

Rationale:

Source-routed packets allow the source of the packet to suggest routers forward the packet along a different path than configured on the router, which can be used to bypass network security measures.
Accepting source-routed packets in the IPv4 protocol has few legitimate uses. It should be disabled unless it is absolutely required, such as when IPv4 forwarding is enabled and the system is legitimately functioning as a router.

Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_sysctl_net_ipv4_conf_default_accept_source_route

References:

cis-csc | 1, 11, 12, 13, 14, 15, 16, 18, 2, 3, 4, 6, 7, 8, 9
cjis | 5.10.1.1
cobit5 | APO01.06, APO13.01, BAI04.04, BAI10.01, BAI10.02, BAI10.03, BAI10.05, DSS01.03, DSS01.05, DSS03.01, DSS03.05, DSS05.02, DSS05.04, DSS05.05, DSS05.07, DSS06.02, DSS06.06
cui | 3.1.20
disa | CCI-000366
isa-62443-2009 | 4.2.3.4, 4.3.3.4, 4.3.3.5.1, 4.3.3.5.2, 4.3.3.5.3, 4.3.3.5.4, 4.3.3.5.5, 4.3.3.5.6, 4.3.3.5.7, 4.3.3.5.8, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.1, 4.3.3.7.2, 4.3.3.7.3, 4.3.3.7.4, 4.3.4.3.2, 4.3.4.3.3, 4.4.3.3
isa-62443-2013 | SR 1.1, SR 1.10, SR 1.11, SR 1.12, SR 1.13, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.6, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 2.2, SR 2.3, SR 2.4, SR 2.5, SR 2.6, SR 2.7, SR 3.1, SR 3.5, SR 3.8, SR 4.1, SR 4.3, SR 5.1, SR 5.2, SR 5.3, SR 6.2, SR 7.1, SR 7.2, SR 7.6
iso27001-2013 | A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.12.1.1, A.12.1.2, A.12.1.3, A.12.5.1, A.12.6.2, A.13.1.1, A.13.1.2, A.13.1.3, A.13.2.1, A.13.2.2, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, A.14.2.2, A.14.2.3, A.14.2.4, A.17.2.1, A.6.1.2, A.7.1.1, A.7.1.2, A.7.3.1, A.8.2.2, A.8.2.3, A.9.1.1, A.9.1.2, A.9.2.3, A.9.4.1, A.9.4.4, A.9.4.5
nerc-cip | CIP-007-3 R4, CIP-007-3 R4.1, CIP-007-3 R4.2, CIP-007-3 R5.1
nist | CM-7(a), CM-7(b), SC-5, SC-7(a)
nist-csf | DE.AE-1, DE.CM-1, ID.AM-3, PR.AC-5, PR.DS-4, PR.DS-5, PR.IP-1, PR.PT-3, PR.PT-4
os-srg | SRG-OS-000480-GPOS-00227
cis | 3.3.1
anssi | R12

Remediation Shell script ⇲

Complexity: | low
Disruption: | medium
Reboot: | true
Strategy: | disable

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    # Comment out any occurrences of net.ipv4.conf.default.accept_source_route from /etc/sysctl.d/*.conf files

    for f in /etc/sysctl.d/*.conf /run/sysctl.d/*.conf /usr/local/lib/sysctl.d/*.conf; do

      # skip systemd-sysctl symlink (/etc/sysctl.d/99-sysctl.conf -> /etc/sysctl.conf)
      if [[ "$(readlink -f "$f")" == "/etc/sysctl.conf" ]]; then continue; fi

      matching_list=$(grep -P '^(?!#).*[\s]*net.ipv4.conf.default.accept_source_route.*$' $f | uniq )
      if ! test -z "$matching_list"; then
        while IFS= read -r entry; do
          escaped_entry=$(sed -e 's|/|\\/|g' <<< "$entry")
          # comment out "net.ipv4.conf.default.accept_source_route" matches to preserve user data
          sed -i --follow-symlinks "s/^${escaped_entry}$/# &/g" $f
        done <<< "$matching_list"
      fi
    done

    #
    # Set sysctl config file which to save the desired value
    #

    SYSCONFIG_FILE="/etc/sysctl.conf"

    sysctl_net_ipv4_conf_default_accept_source_route_value='0'

    #
    # Set runtime for net.ipv4.conf.default.accept_source_route
    #
    if [[ "$OSCAP_BOOTC_BUILD" != "YES" ]] ; then
        /sbin/sysctl -q -n -w net.ipv4.conf.default.accept_source_route="$sysctl_net_ipv4_conf_default_accept_source_route_value"
    fi

    #
    # If net.ipv4.conf.default.accept_source_route present in /etc/sysctl.conf, change value to appropriate value
    #	else, add "net.ipv4.conf.default.accept_source_route = value" to /etc/sysctl.conf
    #

    # Strip any search characters in the key arg so that the key can be replaced without
    # adding any search characters to the config file.
    stripped_key=$(sed 's/[\^=\$,;+]*//g' <<< "^net.ipv4.conf.default.accept_source_route")

    # shellcheck disable=SC2059
    printf -v formatted_output "%s = %s" "$stripped_key" "$sysctl_net_ipv4_conf_default_accept_source_route_value"

    # If the key exists, change it. Otherwise, add it to the config_file.
    # We search for the key string followed by a word boundary (matched by \>),
    # so if we search for 'setting', 'setting2' won't match.
    if LC_ALL=C grep -q -m 1 -i -e "^net.ipv4.conf.default.accept_source_route\\>" "${SYSCONFIG_FILE}"; then
        escaped_formatted_output=$(sed -e 's|/|\\/|g' <<< "$formatted_output")
        LC_ALL=C sed -i --follow-symlinks "s/^net.ipv4.conf.default.accept_source_route\\>.*/$escaped_formatted_output/gi" "${SYSCONFIG_FILE}"
    else
        if [[ -s "${SYSCONFIG_FILE}" ]] && [[ -n "$(tail -c 1 -- "${SYSCONFIG_FILE}" || true)" ]]; then
            LC_ALL=C sed -i --follow-symlinks '$a'\\ "${SYSCONFIG_FILE}"
        fi
        printf '%s\n' "$formatted_output" >> "${SYSCONFIG_FILE}"
    fi

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | medium
Reboot: | true
Strategy: | disable

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - CJIS-5.10.1.1
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-SC-5
      - NIST-800-53-SC-7(a)
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_net_ipv4_conf_default_accept_source_route

    - name: List /etc/sysctl.d/*.conf files
      find:
        paths:
        - /etc/sysctl.d/
        - /run/sysctl.d/
        - /usr/local/lib/sysctl.d/
        contains: ^[\s]*net.ipv4.conf.default.accept_source_route.*$
        patterns: '*.conf'
        file_type: any
      register: find_sysctl_d
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - CJIS-5.10.1.1
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-SC-5
      - NIST-800-53-SC-7(a)
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_net_ipv4_conf_default_accept_source_route

    - name: Comment out any occurrences of net.ipv4.conf.default.accept_source_route from
        config files
      replace:
        path: '{{ item.path }}'
        regexp: ^[\s]*net.ipv4.conf.default.accept_source_route
        replace: '#net.ipv4.conf.default.accept_source_route'
      loop: '{{ find_sysctl_d.files }}'
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - CJIS-5.10.1.1
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-SC-5
      - NIST-800-53-SC-7(a)
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_net_ipv4_conf_default_accept_source_route
    - name: XCCDF Value sysctl_net_ipv4_conf_default_accept_source_route_value # promote to variable
      set_fact:
        sysctl_net_ipv4_conf_default_accept_source_route_value: !!str 0
      tags:
        - always

    - name: Ensure sysctl net.ipv4.conf.default.accept_source_route is set
      sysctl:
        name: net.ipv4.conf.default.accept_source_route
        value: '{{ sysctl_net_ipv4_conf_default_accept_source_route_value }}'
        sysctl_file: /etc/sysctl.conf
        state: present
        reload: true
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - CJIS-5.10.1.1
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-SC-5
      - NIST-800-53-SC-7(a)
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_net_ipv4_conf_default_accept_source_route

#### Rule Enable Kernel Paremeter to Log Martian Packets on all IPv4 Interfaces by Default [ref]

To set the runtime status of the `net.ipv4.conf.default.log_martians` kernel parameter, run the following command:

    $ sudo sysctl -w net.ipv4.conf.default.log_martians=1

To make sure that the setting is persistent, add the following line to a file in the directory `/etc/sysctl.d`:

    net.ipv4.conf.default.log_martians = 1

Rationale: | The presence of "martian" packets (which have impossible addresses) as well as spoofed packets, source-routed packets, and redirects could be a sign of nefarious network activity. Logging these packets enables this activity to be detected.
Severity: | unknown
Rule ID: | xccdf_org.ssgproject.content_rule_sysctl_net_ipv4_conf_default_log_martians

References:

cis-csc | 1, 11, 12, 13, 14, 15, 16, 2, 3, 7, 8, 9
cobit5 | APO13.01, BAI04.04, BAI10.01, BAI10.02, BAI10.03, BAI10.05, DSS01.03, DSS01.04, DSS03.05, DSS05.02, DSS05.03, DSS05.05, DSS05.07, DSS06.06
cui | 3.1.20
disa | CCI-000366
isa-62443-2009 | 4.3.3.5.1, 4.3.3.5.2, 4.3.3.5.3, 4.3.3.5.4, 4.3.3.5.5, 4.3.3.5.6, 4.3.3.5.7, 4.3.3.5.8, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.1, 4.3.3.7.2, 4.3.3.7.3, 4.3.3.7.4, 4.3.4.3.2, 4.3.4.3.3
isa-62443-2013 | SR 1.1, SR 1.10, SR 1.11, SR 1.12, SR 1.13, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.6, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 2.2, SR 2.3, SR 2.4, SR 2.5, SR 2.6, SR 2.7, SR 3.1, SR 3.5, SR 3.8, SR 4.1, SR 4.3, SR 5.1, SR 5.2, SR 5.3, SR 6.2, SR 7.1, SR 7.2, SR 7.6
iso27001-2013 | A.11.2.6, A.12.1.2, A.12.1.3, A.12.5.1, A.12.6.2, A.13.1.1, A.13.2.1, A.14.1.3, A.14.2.2, A.14.2.3, A.14.2.4, A.17.2.1, A.6.2.1, A.6.2.2, A.9.1.2
nist | CM-7(a), CM-7(b), SC-5(3)(a)
nist-csf | DE.CM-1, PR.AC-3, PR.DS-4, PR.IP-1, PR.PT-3, PR.PT-4
os-srg | SRG-OS-000480-GPOS-00227
cis | 3.3.4

Remediation Shell script ⇲

Complexity: | low
Disruption: | medium
Reboot: | true
Strategy: | disable

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    # Comment out any occurrences of net.ipv4.conf.default.log_martians from /etc/sysctl.d/*.conf files

    for f in /etc/sysctl.d/*.conf /run/sysctl.d/*.conf /usr/local/lib/sysctl.d/*.conf; do

      # skip systemd-sysctl symlink (/etc/sysctl.d/99-sysctl.conf -> /etc/sysctl.conf)
      if [[ "$(readlink -f "$f")" == "/etc/sysctl.conf" ]]; then continue; fi

      matching_list=$(grep -P '^(?!#).*[\s]*net.ipv4.conf.default.log_martians.*$' $f | uniq )
      if ! test -z "$matching_list"; then
        while IFS= read -r entry; do
          escaped_entry=$(sed -e 's|/|\\/|g' <<< "$entry")
          # comment out "net.ipv4.conf.default.log_martians" matches to preserve user data
          sed -i --follow-symlinks "s/^${escaped_entry}$/# &/g" $f
        done <<< "$matching_list"
      fi
    done

    #
    # Set sysctl config file which to save the desired value
    #

    SYSCONFIG_FILE="/etc/sysctl.conf"

    sysctl_net_ipv4_conf_default_log_martians_value='1'

    #
    # Set runtime for net.ipv4.conf.default.log_martians
    #
    if [[ "$OSCAP_BOOTC_BUILD" != "YES" ]] ; then
        /sbin/sysctl -q -n -w net.ipv4.conf.default.log_martians="$sysctl_net_ipv4_conf_default_log_martians_value"
    fi

    #
    # If net.ipv4.conf.default.log_martians present in /etc/sysctl.conf, change value to appropriate value
    #	else, add "net.ipv4.conf.default.log_martians = value" to /etc/sysctl.conf
    #

    # Strip any search characters in the key arg so that the key can be replaced without
    # adding any search characters to the config file.
    stripped_key=$(sed 's/[\^=\$,;+]*//g' <<< "^net.ipv4.conf.default.log_martians")

    # shellcheck disable=SC2059
    printf -v formatted_output "%s = %s" "$stripped_key" "$sysctl_net_ipv4_conf_default_log_martians_value"

    # If the key exists, change it. Otherwise, add it to the config_file.
    # We search for the key string followed by a word boundary (matched by \>),
    # so if we search for 'setting', 'setting2' won't match.
    if LC_ALL=C grep -q -m 1 -i -e "^net.ipv4.conf.default.log_martians\\>" "${SYSCONFIG_FILE}"; then
        escaped_formatted_output=$(sed -e 's|/|\\/|g' <<< "$formatted_output")
        LC_ALL=C sed -i --follow-symlinks "s/^net.ipv4.conf.default.log_martians\\>.*/$escaped_formatted_output/gi" "${SYSCONFIG_FILE}"
    else
        if [[ -s "${SYSCONFIG_FILE}" ]] && [[ -n "$(tail -c 1 -- "${SYSCONFIG_FILE}" || true)" ]]; then
            LC_ALL=C sed -i --follow-symlinks '$a'\\ "${SYSCONFIG_FILE}"
        fi
        printf '%s\n' "$formatted_output" >> "${SYSCONFIG_FILE}"
    fi

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | medium
Reboot: | true
Strategy: | disable

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-SC-5(3)(a)
      - disable_strategy
      - low_complexity
      - medium_disruption
      - reboot_required
      - sysctl_net_ipv4_conf_default_log_martians
      - unknown_severity

    - name: List /etc/sysctl.d/*.conf files
      find:
        paths:
        - /etc/sysctl.d/
        - /run/sysctl.d/
        - /usr/local/lib/sysctl.d/
        contains: ^[\s]*net.ipv4.conf.default.log_martians.*$
        patterns: '*.conf'
        file_type: any
      register: find_sysctl_d
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-SC-5(3)(a)
      - disable_strategy
      - low_complexity
      - medium_disruption
      - reboot_required
      - sysctl_net_ipv4_conf_default_log_martians
      - unknown_severity

    - name: Comment out any occurrences of net.ipv4.conf.default.log_martians from config
        files
      replace:
        path: '{{ item.path }}'
        regexp: ^[\s]*net.ipv4.conf.default.log_martians
        replace: '#net.ipv4.conf.default.log_martians'
      loop: '{{ find_sysctl_d.files }}'
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-SC-5(3)(a)
      - disable_strategy
      - low_complexity
      - medium_disruption
      - reboot_required
      - sysctl_net_ipv4_conf_default_log_martians
      - unknown_severity
    - name: XCCDF Value sysctl_net_ipv4_conf_default_log_martians_value # promote to variable
      set_fact:
        sysctl_net_ipv4_conf_default_log_martians_value: !!str 1
      tags:
        - always

    - name: Ensure sysctl net.ipv4.conf.default.log_martians is set
      sysctl:
        name: net.ipv4.conf.default.log_martians
        value: '{{ sysctl_net_ipv4_conf_default_log_martians_value }}'
        sysctl_file: /etc/sysctl.conf
        state: present
        reload: true
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-SC-5(3)(a)
      - disable_strategy
      - low_complexity
      - medium_disruption
      - reboot_required
      - sysctl_net_ipv4_conf_default_log_martians
      - unknown_severity

#### Rule Enable Kernel Parameter to Use Reverse Path Filtering on all IPv4 Interfaces by Default [ref]

To set the runtime status of the `net.ipv4.conf.default.rp_filter` kernel parameter, run the following command:

    $ sudo sysctl -w net.ipv4.conf.default.rp_filter=1

To make sure that the setting is persistent, add the following line to a file in the directory `/etc/sysctl.d`:

    net.ipv4.conf.default.rp_filter = 1

Rationale: | Enabling reverse path filtering drops packets with source addresses that should not have been able to be received on the interface they were received on. It should not be used on systems which are routers for complicated networks, but is helpful for end hosts and routers serving small networks.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_sysctl_net_ipv4_conf_default_rp_filter

References:

cis-csc | 1, 12, 13, 14, 15, 16, 18, 2, 4, 6, 7, 8, 9
cobit5 | APO01.06, APO13.01, BAI04.04, DSS01.03, DSS01.05, DSS03.01, DSS03.05, DSS05.02, DSS05.04, DSS05.07, DSS06.02
cui | 3.1.20
disa | CCI-000366
isa-62443-2009 | 4.2.3.4, 4.3.3.4, 4.4.3.3
isa-62443-2013 | SR 3.1, SR 3.5, SR 3.8, SR 4.1, SR 4.3, SR 5.1, SR 5.2, SR 5.3, SR 6.2, SR 7.1, SR 7.2, SR 7.6
iso27001-2013 | A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.12.1.1, A.12.1.2, A.12.1.3, A.13.1.1, A.13.1.2, A.13.1.3, A.13.2.1, A.13.2.2, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, A.17.2.1, A.6.1.2, A.7.1.1, A.7.1.2, A.7.3.1, A.8.2.2, A.8.2.3, A.9.1.1, A.9.1.2, A.9.2.3, A.9.4.1, A.9.4.4, A.9.4.5
nist | CM-7(a), CM-7(b), CM-6(a), SC-7(a)
nist-csf | DE.AE-1, DE.CM-1, ID.AM-3, PR.AC-5, PR.DS-4, PR.DS-5, PR.PT-4
os-srg | SRG-OS-000480-GPOS-00227
cis | 3.3.7
anssi | R12

Remediation Shell script ⇲

Complexity: | low
Disruption: | medium
Reboot: | true
Strategy: | disable

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    # Comment out any occurrences of net.ipv4.conf.default.rp_filter from /etc/sysctl.d/*.conf files

    for f in /etc/sysctl.d/*.conf /run/sysctl.d/*.conf /usr/local/lib/sysctl.d/*.conf; do

      # skip systemd-sysctl symlink (/etc/sysctl.d/99-sysctl.conf -> /etc/sysctl.conf)
      if [[ "$(readlink -f "$f")" == "/etc/sysctl.conf" ]]; then continue; fi

      matching_list=$(grep -P '^(?!#).*[\s]*net.ipv4.conf.default.rp_filter.*$' $f | uniq )
      if ! test -z "$matching_list"; then
        while IFS= read -r entry; do
          escaped_entry=$(sed -e 's|/|\\/|g' <<< "$entry")
          # comment out "net.ipv4.conf.default.rp_filter" matches to preserve user data
          sed -i --follow-symlinks "s/^${escaped_entry}$/# &/g" $f
        done <<< "$matching_list"
      fi
    done

    #
    # Set sysctl config file which to save the desired value
    #

    SYSCONFIG_FILE="/etc/sysctl.conf"

    sysctl_net_ipv4_conf_default_rp_filter_value='1'

    #
    # Set runtime for net.ipv4.conf.default.rp_filter
    #
    if [[ "$OSCAP_BOOTC_BUILD" != "YES" ]] ; then
        /sbin/sysctl -q -n -w net.ipv4.conf.default.rp_filter="$sysctl_net_ipv4_conf_default_rp_filter_value"
    fi

    #
    # If net.ipv4.conf.default.rp_filter present in /etc/sysctl.conf, change value to appropriate value
    #	else, add "net.ipv4.conf.default.rp_filter = value" to /etc/sysctl.conf
    #

    # Strip any search characters in the key arg so that the key can be replaced without
    # adding any search characters to the config file.
    stripped_key=$(sed 's/[\^=\$,;+]*//g' <<< "^net.ipv4.conf.default.rp_filter")

    # shellcheck disable=SC2059
    printf -v formatted_output "%s = %s" "$stripped_key" "$sysctl_net_ipv4_conf_default_rp_filter_value"

    # If the key exists, change it. Otherwise, add it to the config_file.
    # We search for the key string followed by a word boundary (matched by \>),
    # so if we search for 'setting', 'setting2' won't match.
    if LC_ALL=C grep -q -m 1 -i -e "^net.ipv4.conf.default.rp_filter\\>" "${SYSCONFIG_FILE}"; then
        escaped_formatted_output=$(sed -e 's|/|\\/|g' <<< "$formatted_output")
        LC_ALL=C sed -i --follow-symlinks "s/^net.ipv4.conf.default.rp_filter\\>.*/$escaped_formatted_output/gi" "${SYSCONFIG_FILE}"
    else
        if [[ -s "${SYSCONFIG_FILE}" ]] && [[ -n "$(tail -c 1 -- "${SYSCONFIG_FILE}" || true)" ]]; then
            LC_ALL=C sed -i --follow-symlinks '$a'\\ "${SYSCONFIG_FILE}"
        fi
        printf '%s\n' "$formatted_output" >> "${SYSCONFIG_FILE}"
    fi

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | medium
Reboot: | true
Strategy: | disable

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-SC-7(a)
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_net_ipv4_conf_default_rp_filter

    - name: List /etc/sysctl.d/*.conf files
      find:
        paths:
        - /etc/sysctl.d/
        - /run/sysctl.d/
        - /usr/local/lib/sysctl.d/
        contains: ^[\s]*net.ipv4.conf.default.rp_filter.*$
        patterns: '*.conf'
        file_type: any
      register: find_sysctl_d
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-SC-7(a)
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_net_ipv4_conf_default_rp_filter

    - name: Comment out any occurrences of net.ipv4.conf.default.rp_filter from config
        files
      replace:
        path: '{{ item.path }}'
        regexp: ^[\s]*net.ipv4.conf.default.rp_filter
        replace: '#net.ipv4.conf.default.rp_filter'
      loop: '{{ find_sysctl_d.files }}'
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-SC-7(a)
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_net_ipv4_conf_default_rp_filter
    - name: XCCDF Value sysctl_net_ipv4_conf_default_rp_filter_value # promote to variable
      set_fact:
        sysctl_net_ipv4_conf_default_rp_filter_value: !!str 1
      tags:
        - always

    - name: Ensure sysctl net.ipv4.conf.default.rp_filter is set
      sysctl:
        name: net.ipv4.conf.default.rp_filter
        value: '{{ sysctl_net_ipv4_conf_default_rp_filter_value }}'
        sysctl_file: /etc/sysctl.conf
        state: present
        reload: true
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-SC-7(a)
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_net_ipv4_conf_default_rp_filter

#### Rule Configure Kernel Parameter for Accepting Secure Redirects By Default [ref]

To set the runtime status of the `net.ipv4.conf.default.secure_redirects` kernel parameter, run the following command:

    $ sudo sysctl -w net.ipv4.conf.default.secure_redirects=0

To make sure that the setting is persistent, add the following line to a file in the directory `/etc/sysctl.d`:

    net.ipv4.conf.default.secure_redirects = 0

Rationale: | Accepting "secure" ICMP redirects (from those gateways listed as default gateways) has few legitimate uses. It should be disabled unless it is absolutely required.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_sysctl_net_ipv4_conf_default_secure_redirects

References:

cis-csc | 1, 11, 12, 13, 14, 15, 16, 18, 2, 3, 4, 6, 7, 8, 9
cobit5 | APO01.06, APO13.01, BAI04.04, BAI10.01, BAI10.02, BAI10.03, BAI10.05, DSS01.03, DSS01.05, DSS03.01, DSS03.05, DSS05.02, DSS05.04, DSS05.05, DSS05.07, DSS06.02, DSS06.06
cui | 3.1.20
disa | CCI-001551
isa-62443-2009 | 4.2.3.4, 4.3.3.4, 4.3.3.5.1, 4.3.3.5.2, 4.3.3.5.3, 4.3.3.5.4, 4.3.3.5.5, 4.3.3.5.6, 4.3.3.5.7, 4.3.3.5.8, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.1, 4.3.3.7.2, 4.3.3.7.3, 4.3.3.7.4, 4.3.4.3.2, 4.3.4.3.3, 4.4.3.3
isa-62443-2013 | SR 1.1, SR 1.10, SR 1.11, SR 1.12, SR 1.13, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.6, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 2.2, SR 2.3, SR 2.4, SR 2.5, SR 2.6, SR 2.7, SR 3.1, SR 3.5, SR 3.8, SR 4.1, SR 4.3, SR 5.1, SR 5.2, SR 5.3, SR 6.2, SR 7.1, SR 7.2, SR 7.6
iso27001-2013 | A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.12.1.1, A.12.1.2, A.12.1.3, A.12.5.1, A.12.6.2, A.13.1.1, A.13.1.2, A.13.1.3, A.13.2.1, A.13.2.2, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, A.14.2.2, A.14.2.3, A.14.2.4, A.17.2.1, A.6.1.2, A.7.1.1, A.7.1.2, A.7.3.1, A.8.2.2, A.8.2.3, A.9.1.1, A.9.1.2, A.9.2.3, A.9.4.1, A.9.4.4, A.9.4.5
nerc-cip | CIP-007-3 R4, CIP-007-3 R4.1, CIP-007-3 R4.2, CIP-007-3 R5.1
nist | CM-7(a), CM-7(b), SC-5, SC-7(a)
nist-csf | DE.AE-1, DE.CM-1, ID.AM-3, PR.AC-5, PR.DS-4, PR.DS-5, PR.IP-1, PR.PT-3, PR.PT-4
os-srg | SRG-OS-000480-GPOS-00227
cis | 3.3.3
anssi | R12

Remediation Shell script ⇲

Complexity: | low
Disruption: | medium
Reboot: | true
Strategy: | disable

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    # Comment out any occurrences of net.ipv4.conf.default.secure_redirects from /etc/sysctl.d/*.conf files

    for f in /etc/sysctl.d/*.conf /run/sysctl.d/*.conf /usr/local/lib/sysctl.d/*.conf; do

      # skip systemd-sysctl symlink (/etc/sysctl.d/99-sysctl.conf -> /etc/sysctl.conf)
      if [[ "$(readlink -f "$f")" == "/etc/sysctl.conf" ]]; then continue; fi

      matching_list=$(grep -P '^(?!#).*[\s]*net.ipv4.conf.default.secure_redirects.*$' $f | uniq )
      if ! test -z "$matching_list"; then
        while IFS= read -r entry; do
          escaped_entry=$(sed -e 's|/|\\/|g' <<< "$entry")
          # comment out "net.ipv4.conf.default.secure_redirects" matches to preserve user data
          sed -i --follow-symlinks "s/^${escaped_entry}$/# &/g" $f
        done <<< "$matching_list"
      fi
    done

    #
    # Set sysctl config file which to save the desired value
    #

    SYSCONFIG_FILE="/etc/sysctl.conf"

    sysctl_net_ipv4_conf_default_secure_redirects_value='0'

    #
    # Set runtime for net.ipv4.conf.default.secure_redirects
    #
    if [[ "$OSCAP_BOOTC_BUILD" != "YES" ]] ; then
        /sbin/sysctl -q -n -w net.ipv4.conf.default.secure_redirects="$sysctl_net_ipv4_conf_default_secure_redirects_value"
    fi

    #
    # If net.ipv4.conf.default.secure_redirects present in /etc/sysctl.conf, change value to appropriate value
    #	else, add "net.ipv4.conf.default.secure_redirects = value" to /etc/sysctl.conf
    #

    # Strip any search characters in the key arg so that the key can be replaced without
    # adding any search characters to the config file.
    stripped_key=$(sed 's/[\^=\$,;+]*//g' <<< "^net.ipv4.conf.default.secure_redirects")

    # shellcheck disable=SC2059
    printf -v formatted_output "%s = %s" "$stripped_key" "$sysctl_net_ipv4_conf_default_secure_redirects_value"

    # If the key exists, change it. Otherwise, add it to the config_file.
    # We search for the key string followed by a word boundary (matched by \>),
    # so if we search for 'setting', 'setting2' won't match.
    if LC_ALL=C grep -q -m 1 -i -e "^net.ipv4.conf.default.secure_redirects\\>" "${SYSCONFIG_FILE}"; then
        escaped_formatted_output=$(sed -e 's|/|\\/|g' <<< "$formatted_output")
        LC_ALL=C sed -i --follow-symlinks "s/^net.ipv4.conf.default.secure_redirects\\>.*/$escaped_formatted_output/gi" "${SYSCONFIG_FILE}"
    else
        if [[ -s "${SYSCONFIG_FILE}" ]] && [[ -n "$(tail -c 1 -- "${SYSCONFIG_FILE}" || true)" ]]; then
            LC_ALL=C sed -i --follow-symlinks '$a'\\ "${SYSCONFIG_FILE}"
        fi
        printf '%s\n' "$formatted_output" >> "${SYSCONFIG_FILE}"
    fi

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | medium
Reboot: | true
Strategy: | disable

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-SC-5
      - NIST-800-53-SC-7(a)
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_net_ipv4_conf_default_secure_redirects

    - name: List /etc/sysctl.d/*.conf files
      find:
        paths:
        - /etc/sysctl.d/
        - /run/sysctl.d/
        - /usr/local/lib/sysctl.d/
        contains: ^[\s]*net.ipv4.conf.default.secure_redirects.*$
        patterns: '*.conf'
        file_type: any
      register: find_sysctl_d
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-SC-5
      - NIST-800-53-SC-7(a)
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_net_ipv4_conf_default_secure_redirects

    - name: Comment out any occurrences of net.ipv4.conf.default.secure_redirects from
        config files
      replace:
        path: '{{ item.path }}'
        regexp: ^[\s]*net.ipv4.conf.default.secure_redirects
        replace: '#net.ipv4.conf.default.secure_redirects'
      loop: '{{ find_sysctl_d.files }}'
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-SC-5
      - NIST-800-53-SC-7(a)
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_net_ipv4_conf_default_secure_redirects
    - name: XCCDF Value sysctl_net_ipv4_conf_default_secure_redirects_value # promote to variable
      set_fact:
        sysctl_net_ipv4_conf_default_secure_redirects_value: !!str 0
      tags:
        - always

    - name: Ensure sysctl net.ipv4.conf.default.secure_redirects is set
      sysctl:
        name: net.ipv4.conf.default.secure_redirects
        value: '{{ sysctl_net_ipv4_conf_default_secure_redirects_value }}'
        sysctl_file: /etc/sysctl.conf
        state: present
        reload: true
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-SC-5
      - NIST-800-53-SC-7(a)
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_net_ipv4_conf_default_secure_redirects

#### Rule Enable Kernel Parameter to Ignore ICMP Broadcast Echo Requests on IPv4 Interfaces [ref]

To set the runtime status of the `net.ipv4.icmp_echo_ignore_broadcasts` kernel parameter, run the following command:

    $ sudo sysctl -w net.ipv4.icmp_echo_ignore_broadcasts=1

To make sure that the setting is persistent, add the following line to a file in the directory `/etc/sysctl.d`:

    net.ipv4.icmp_echo_ignore_broadcasts = 1

Rationale: | Responding to broadcast (ICMP) echoes facilitates network mapping and provides a vector for amplification attacks. Ignoring ICMP echo requests (pings) sent to broadcast or multicast addresses makes the system slightly more difficult to enumerate on the network.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_sysctl_net_ipv4_icmp_echo_ignore_broadcasts

References:

cis-csc | 1, 11, 12, 13, 14, 15, 16, 18, 2, 3, 4, 6, 7, 8, 9
cjis | 5.10.1.1
cobit5 | APO01.06, APO13.01, BAI04.04, BAI10.01, BAI10.02, BAI10.03, BAI10.05, DSS01.03, DSS01.05, DSS03.01, DSS03.05, DSS05.02, DSS05.04, DSS05.05, DSS05.07, DSS06.02, DSS06.06
cui | 3.1.20
disa | CCI-000366
isa-62443-2009 | 4.2.3.4, 4.3.3.4, 4.3.3.5.1, 4.3.3.5.2, 4.3.3.5.3, 4.3.3.5.4, 4.3.3.5.5, 4.3.3.5.6, 4.3.3.5.7, 4.3.3.5.8, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.1, 4.3.3.7.2, 4.3.3.7.3, 4.3.3.7.4, 4.3.4.3.2, 4.3.4.3.3, 4.4.3.3
isa-62443-2013 | SR 1.1, SR 1.10, SR 1.11, SR 1.12, SR 1.13, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.6, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 2.2, SR 2.3, SR 2.4, SR 2.5, SR 2.6, SR 2.7, SR 3.1, SR 3.5, SR 3.8, SR 4.1, SR 4.3, SR 5.1, SR 5.2, SR 5.3, SR 6.2, SR 7.1, SR 7.2, SR 7.6
iso27001-2013 | A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.12.1.1, A.12.1.2, A.12.1.3, A.12.5.1, A.12.6.2, A.13.1.1, A.13.1.2, A.13.1.3, A.13.2.1, A.13.2.2, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, A.14.2.2, A.14.2.3, A.14.2.4, A.17.2.1, A.6.1.2, A.7.1.1, A.7.1.2, A.7.3.1, A.8.2.2, A.8.2.3, A.9.1.1, A.9.1.2, A.9.2.3, A.9.4.1, A.9.4.4, A.9.4.5
nerc-cip | CIP-007-3 R4, CIP-007-3 R4.1, CIP-007-3 R4.2, CIP-007-3 R5.1
nist | CM-7(a), CM-7(b), SC-5
nist-csf | DE.AE-1, DE.CM-1, ID.AM-3, PR.AC-5, PR.DS-4, PR.DS-5, PR.IP-1, PR.PT-3, PR.PT-4
pcidss | Req-1.4.3
os-srg | SRG-OS-000480-GPOS-00227
cis | 3.3.5
pcidss4 | 1.4.2, 1.4

Remediation Shell script ⇲

Complexity: | low
Disruption: | medium
Reboot: | true
Strategy: | disable

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    # Comment out any occurrences of net.ipv4.icmp_echo_ignore_broadcasts from /etc/sysctl.d/*.conf files

    for f in /etc/sysctl.d/*.conf /run/sysctl.d/*.conf /usr/local/lib/sysctl.d/*.conf; do

      # skip systemd-sysctl symlink (/etc/sysctl.d/99-sysctl.conf -> /etc/sysctl.conf)
      if [[ "$(readlink -f "$f")" == "/etc/sysctl.conf" ]]; then continue; fi

      matching_list=$(grep -P '^(?!#).*[\s]*net.ipv4.icmp_echo_ignore_broadcasts.*$' $f | uniq )
      if ! test -z "$matching_list"; then
        while IFS= read -r entry; do
          escaped_entry=$(sed -e 's|/|\\/|g' <<< "$entry")
          # comment out "net.ipv4.icmp_echo_ignore_broadcasts" matches to preserve user data
          sed -i --follow-symlinks "s/^${escaped_entry}$/# &/g" $f
        done <<< "$matching_list"
      fi
    done

    #
    # Set sysctl config file which to save the desired value
    #

    SYSCONFIG_FILE="/etc/sysctl.conf"

    sysctl_net_ipv4_icmp_echo_ignore_broadcasts_value='1'

    #
    # Set runtime for net.ipv4.icmp_echo_ignore_broadcasts
    #
    if [[ "$OSCAP_BOOTC_BUILD" != "YES" ]] ; then
        /sbin/sysctl -q -n -w net.ipv4.icmp_echo_ignore_broadcasts="$sysctl_net_ipv4_icmp_echo_ignore_broadcasts_value"
    fi

    #
    # If net.ipv4.icmp_echo_ignore_broadcasts present in /etc/sysctl.conf, change value to appropriate value
    #	else, add "net.ipv4.icmp_echo_ignore_broadcasts = value" to /etc/sysctl.conf
    #

    # Strip any search characters in the key arg so that the key can be replaced without
    # adding any search characters to the config file.
    stripped_key=$(sed 's/[\^=\$,;+]*//g' <<< "^net.ipv4.icmp_echo_ignore_broadcasts")

    # shellcheck disable=SC2059
    printf -v formatted_output "%s = %s" "$stripped_key" "$sysctl_net_ipv4_icmp_echo_ignore_broadcasts_value"

    # If the key exists, change it. Otherwise, add it to the config_file.
    # We search for the key string followed by a word boundary (matched by \>),
    # so if we search for 'setting', 'setting2' won't match.
    if LC_ALL=C grep -q -m 1 -i -e "^net.ipv4.icmp_echo_ignore_broadcasts\\>" "${SYSCONFIG_FILE}"; then
        escaped_formatted_output=$(sed -e 's|/|\\/|g' <<< "$formatted_output")
        LC_ALL=C sed -i --follow-symlinks "s/^net.ipv4.icmp_echo_ignore_broadcasts\\>.*/$escaped_formatted_output/gi" "${SYSCONFIG_FILE}"
    else
        if [[ -s "${SYSCONFIG_FILE}" ]] && [[ -n "$(tail -c 1 -- "${SYSCONFIG_FILE}" || true)" ]]; then
            LC_ALL=C sed -i --follow-symlinks '$a'\\ "${SYSCONFIG_FILE}"
        fi
        printf '%s\n' "$formatted_output" >> "${SYSCONFIG_FILE}"
    fi

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | medium
Reboot: | true
Strategy: | disable

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - CJIS-5.10.1.1
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-SC-5
      - PCI-DSS-Req-1.4.3
      - PCI-DSSv4-1.4
      - PCI-DSSv4-1.4.2
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_net_ipv4_icmp_echo_ignore_broadcasts

    - name: List /etc/sysctl.d/*.conf files
      find:
        paths:
        - /etc/sysctl.d/
        - /run/sysctl.d/
        - /usr/local/lib/sysctl.d/
        contains: ^[\s]*net.ipv4.icmp_echo_ignore_broadcasts.*$
        patterns: '*.conf'
        file_type: any
      register: find_sysctl_d
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - CJIS-5.10.1.1
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-SC-5
      - PCI-DSS-Req-1.4.3
      - PCI-DSSv4-1.4
      - PCI-DSSv4-1.4.2
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_net_ipv4_icmp_echo_ignore_broadcasts

    - name: Comment out any occurrences of net.ipv4.icmp_echo_ignore_broadcasts from config
        files
      replace:
        path: '{{ item.path }}'
        regexp: ^[\s]*net.ipv4.icmp_echo_ignore_broadcasts
        replace: '#net.ipv4.icmp_echo_ignore_broadcasts'
      loop: '{{ find_sysctl_d.files }}'
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - CJIS-5.10.1.1
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-SC-5
      - PCI-DSS-Req-1.4.3
      - PCI-DSSv4-1.4
      - PCI-DSSv4-1.4.2
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_net_ipv4_icmp_echo_ignore_broadcasts
    - name: XCCDF Value sysctl_net_ipv4_icmp_echo_ignore_broadcasts_value # promote to variable
      set_fact:
        sysctl_net_ipv4_icmp_echo_ignore_broadcasts_value: !!str 1
      tags:
        - always

    - name: Ensure sysctl net.ipv4.icmp_echo_ignore_broadcasts is set
      sysctl:
        name: net.ipv4.icmp_echo_ignore_broadcasts
        value: '{{ sysctl_net_ipv4_icmp_echo_ignore_broadcasts_value }}'
        sysctl_file: /etc/sysctl.conf
        state: present
        reload: true
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - CJIS-5.10.1.1
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-SC-5
      - PCI-DSS-Req-1.4.3
      - PCI-DSSv4-1.4
      - PCI-DSSv4-1.4.2
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_net_ipv4_icmp_echo_ignore_broadcasts

#### Rule Enable Kernel Parameter to Ignore Bogus ICMP Error Responses on IPv4 Interfaces [ref]

To set the runtime status of the `net.ipv4.icmp_ignore_bogus_error_responses` kernel parameter, run the following command:

    $ sudo sysctl -w net.ipv4.icmp_ignore_bogus_error_responses=1

To make sure that the setting is persistent, add the following line to a file in the directory `/etc/sysctl.d`:

    net.ipv4.icmp_ignore_bogus_error_responses = 1

Rationale: | Ignoring bogus ICMP error responses reduces log size, although some activity would not be logged.
Severity: | unknown
Rule ID: | xccdf_org.ssgproject.content_rule_sysctl_net_ipv4_icmp_ignore_bogus_error_responses

References:

cis-csc | 1, 11, 12, 13, 14, 15, 16, 2, 3, 7, 8, 9
cobit5 | APO13.01, BAI04.04, BAI10.01, BAI10.02, BAI10.03, BAI10.05, DSS01.03, DSS03.05, DSS05.02, DSS05.05, DSS05.07, DSS06.06
cui | 3.1.20
disa | CCI-000366
isa-62443-2009 | 4.3.3.5.1, 4.3.3.5.2, 4.3.3.5.3, 4.3.3.5.4, 4.3.3.5.5, 4.3.3.5.6, 4.3.3.5.7, 4.3.3.5.8, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.1, 4.3.3.7.2, 4.3.3.7.3, 4.3.3.7.4, 4.3.4.3.2, 4.3.4.3.3
isa-62443-2013 | SR 1.1, SR 1.10, SR 1.11, SR 1.12, SR 1.13, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.6, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 2.2, SR 2.3, SR 2.4, SR 2.5, SR 2.6, SR 2.7, SR 6.2, SR 7.1, SR 7.2, SR 7.6
iso27001-2013 | A.12.1.2, A.12.1.3, A.12.5.1, A.12.6.2, A.14.2.2, A.14.2.3, A.14.2.4, A.17.2.1, A.9.1.2
nerc-cip | CIP-007-3 R4, CIP-007-3 R4.1, CIP-007-3 R4.2, CIP-007-3 R5.1
nist | CM-7(a), CM-7(b), SC-5
nist-csf | DE.CM-1, PR.DS-4, PR.IP-1, PR.PT-3
pcidss | Req-1.4.3
os-srg | SRG-OS-000480-GPOS-00227
cis | 3.3.6
anssi | R12
pcidss4 | 1.4.2, 1.4

Remediation Shell script ⇲

Complexity: | low
Disruption: | medium
Reboot: | true
Strategy: | disable

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    # Comment out any occurrences of net.ipv4.icmp_ignore_bogus_error_responses from /etc/sysctl.d/*.conf files

    for f in /etc/sysctl.d/*.conf /run/sysctl.d/*.conf /usr/local/lib/sysctl.d/*.conf; do

      # skip systemd-sysctl symlink (/etc/sysctl.d/99-sysctl.conf -> /etc/sysctl.conf)
      if [[ "$(readlink -f "$f")" == "/etc/sysctl.conf" ]]; then continue; fi

      matching_list=$(grep -P '^(?!#).*[\s]*net.ipv4.icmp_ignore_bogus_error_responses.*$' $f | uniq )
      if ! test -z "$matching_list"; then
        while IFS= read -r entry; do
          escaped_entry=$(sed -e 's|/|\\/|g' <<< "$entry")
          # comment out "net.ipv4.icmp_ignore_bogus_error_responses" matches to preserve user data
          sed -i --follow-symlinks "s/^${escaped_entry}$/# &/g" $f
        done <<< "$matching_list"
      fi
    done

    #
    # Set sysctl config file which to save the desired value
    #

    SYSCONFIG_FILE="/etc/sysctl.conf"

    sysctl_net_ipv4_icmp_ignore_bogus_error_responses_value='1'

    #
    # Set runtime for net.ipv4.icmp_ignore_bogus_error_responses
    #
    if [[ "$OSCAP_BOOTC_BUILD" != "YES" ]] ; then
        /sbin/sysctl -q -n -w net.ipv4.icmp_ignore_bogus_error_responses="$sysctl_net_ipv4_icmp_ignore_bogus_error_responses_value"
    fi

    #
    # If net.ipv4.icmp_ignore_bogus_error_responses present in /etc/sysctl.conf, change value to appropriate value
    #	else, add "net.ipv4.icmp_ignore_bogus_error_responses = value" to /etc/sysctl.conf
    #

    # Strip any search characters in the key arg so that the key can be replaced without
    # adding any search characters to the config file.
    stripped_key=$(sed 's/[\^=\$,;+]*//g' <<< "^net.ipv4.icmp_ignore_bogus_error_responses")

    # shellcheck disable=SC2059
    printf -v formatted_output "%s = %s" "$stripped_key" "$sysctl_net_ipv4_icmp_ignore_bogus_error_responses_value"

    # If the key exists, change it. Otherwise, add it to the config_file.
    # We search for the key string followed by a word boundary (matched by \>),
    # so if we search for 'setting', 'setting2' won't match.
    if LC_ALL=C grep -q -m 1 -i -e "^net.ipv4.icmp_ignore_bogus_error_responses\\>" "${SYSCONFIG_FILE}"; then
        escaped_formatted_output=$(sed -e 's|/|\\/|g' <<< "$formatted_output")
        LC_ALL=C sed -i --follow-symlinks "s/^net.ipv4.icmp_ignore_bogus_error_responses\\>.*/$escaped_formatted_output/gi" "${SYSCONFIG_FILE}"
    else
        if [[ -s "${SYSCONFIG_FILE}" ]] && [[ -n "$(tail -c 1 -- "${SYSCONFIG_FILE}" || true)" ]]; then
            LC_ALL=C sed -i --follow-symlinks '$a'\\ "${SYSCONFIG_FILE}"
        fi
        printf '%s\n' "$formatted_output" >> "${SYSCONFIG_FILE}"
    fi

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | medium
Reboot: | true
Strategy: | disable

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-SC-5
      - PCI-DSS-Req-1.4.3
      - PCI-DSSv4-1.4
      - PCI-DSSv4-1.4.2
      - disable_strategy
      - low_complexity
      - medium_disruption
      - reboot_required
      - sysctl_net_ipv4_icmp_ignore_bogus_error_responses
      - unknown_severity

    - name: List /etc/sysctl.d/*.conf files
      find:
        paths:
        - /etc/sysctl.d/
        - /run/sysctl.d/
        - /usr/local/lib/sysctl.d/
        contains: ^[\s]*net.ipv4.icmp_ignore_bogus_error_responses.*$
        patterns: '*.conf'
        file_type: any
      register: find_sysctl_d
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-SC-5
      - PCI-DSS-Req-1.4.3
      - PCI-DSSv4-1.4
      - PCI-DSSv4-1.4.2
      - disable_strategy
      - low_complexity
      - medium_disruption
      - reboot_required
      - sysctl_net_ipv4_icmp_ignore_bogus_error_responses
      - unknown_severity

    - name: Comment out any occurrences of net.ipv4.icmp_ignore_bogus_error_responses
        from config files
      replace:
        path: '{{ item.path }}'
        regexp: ^[\s]*net.ipv4.icmp_ignore_bogus_error_responses
        replace: '#net.ipv4.icmp_ignore_bogus_error_responses'
      loop: '{{ find_sysctl_d.files }}'
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-SC-5
      - PCI-DSS-Req-1.4.3
      - PCI-DSSv4-1.4
      - PCI-DSSv4-1.4.2
      - disable_strategy
      - low_complexity
      - medium_disruption
      - reboot_required
      - sysctl_net_ipv4_icmp_ignore_bogus_error_responses
      - unknown_severity
    - name: XCCDF Value sysctl_net_ipv4_icmp_ignore_bogus_error_responses_value # promote to variable
      set_fact:
        sysctl_net_ipv4_icmp_ignore_bogus_error_responses_value: !!str 1
      tags:
        - always

    - name: Ensure sysctl net.ipv4.icmp_ignore_bogus_error_responses is set
      sysctl:
        name: net.ipv4.icmp_ignore_bogus_error_responses
        value: '{{ sysctl_net_ipv4_icmp_ignore_bogus_error_responses_value }}'
        sysctl_file: /etc/sysctl.conf
        state: present
        reload: true
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-SC-5
      - PCI-DSS-Req-1.4.3
      - PCI-DSSv4-1.4
      - PCI-DSSv4-1.4.2
      - disable_strategy
      - low_complexity
      - medium_disruption
      - reboot_required
      - sysctl_net_ipv4_icmp_ignore_bogus_error_responses
      - unknown_severity

#### Rule Enable Kernel Parameter to Use TCP Syncookies on Network Interfaces [ref]

To set the runtime status of the `net.ipv4.tcp_syncookies` kernel parameter, run the following command:

    $ sudo sysctl -w net.ipv4.tcp_syncookies=1

To make sure that the setting is persistent, add the following line to a file in the directory `/etc/sysctl.d`:

    net.ipv4.tcp_syncookies = 1

Rationale:

A TCP SYN flood attack can cause a denial of service by filling a system's TCP connection table with connections in the SYN_RCVD state. Syncookies can be used to track a connection when a subsequent ACK is received, verifying the initiator is attempting a valid connection and is not a flood source. This feature is activated when a flood condition is detected, and enables the system to continue servicing valid connection requests.

Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_sysctl_net_ipv4_tcp_syncookies

References:

cis-csc | 1, 12, 13, 14, 15, 16, 18, 2, 4, 6, 7, 8, 9
cjis | 5.10.1.1
cobit5 | APO01.06, APO13.01, BAI04.04, DSS01.03, DSS01.05, DSS03.01, DSS03.05, DSS05.02, DSS05.04, DSS05.07, DSS06.02
cui | 3.1.20
disa | CCI-001095, CCI-000366, CCI-002385
isa-62443-2009 | 4.2.3.4, 4.3.3.4, 4.4.3.3
isa-62443-2013 | SR 3.1, SR 3.5, SR 3.8, SR 4.1, SR 4.3, SR 5.1, SR 5.2, SR 5.3, SR 6.2, SR 7.1, SR 7.2, SR 7.6
iso27001-2013 | A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.12.1.1, A.12.1.2, A.12.1.3, A.13.1.1, A.13.1.2, A.13.1.3, A.13.2.1, A.13.2.2, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, A.17.2.1, A.6.1.2, A.7.1.1, A.7.1.2, A.7.3.1, A.8.2.2, A.8.2.3, A.9.1.1, A.9.1.2, A.9.2.3, A.9.4.1, A.9.4.4, A.9.4.5
nist | CM-7(a), CM-7(b), SC-5(1), SC-5(2), SC-5(3)(a), CM-6(a)
nist-csf | DE.AE-1, DE.CM-1, ID.AM-3, PR.AC-5, PR.DS-4, PR.DS-5, PR.PT-4
pcidss | Req-1.4.1
os-srg | SRG-OS-000480-GPOS-00227, SRG-OS-000420-GPOS-00186, SRG-OS-000142-GPOS-00071
stigid | UBTU-20-010412
cis | 3.3.8
anssi | R12
pcidss4 | 1.4.3, 1.4
stigref | SV-238333r654174_rule

Remediation Shell script ⇲

Complexity: | low
Disruption: | medium
Reboot: | true
Strategy: | disable

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    # Comment out any occurrences of net.ipv4.tcp_syncookies from /etc/sysctl.d/*.conf files

    for f in /etc/sysctl.d/*.conf /run/sysctl.d/*.conf /usr/local/lib/sysctl.d/*.conf; do

      # skip systemd-sysctl symlink (/etc/sysctl.d/99-sysctl.conf -> /etc/sysctl.conf)
      if [[ "$(readlink -f "$f")" == "/etc/sysctl.conf" ]]; then continue; fi

      matching_list=$(grep -P '^(?!#).*[\s]*net.ipv4.tcp_syncookies.*$' $f | uniq )
      if ! test -z "$matching_list"; then
        while IFS= read -r entry; do
          escaped_entry=$(sed -e 's|/|\\/|g' <<< "$entry")
          # comment out "net.ipv4.tcp_syncookies" matches to preserve user data
          sed -i --follow-symlinks "s/^${escaped_entry}$/# &/g" $f
        done <<< "$matching_list"
      fi
    done

    #
    # Set sysctl config file which to save the desired value
    #

    SYSCONFIG_FILE="/etc/sysctl.conf"

    sysctl_net_ipv4_tcp_syncookies_value='1'

    #
    # Set runtime for net.ipv4.tcp_syncookies
    #
    if [[ "$OSCAP_BOOTC_BUILD" != "YES" ]] ; then
        /sbin/sysctl -q -n -w net.ipv4.tcp_syncookies="$sysctl_net_ipv4_tcp_syncookies_value"
    fi

    #
    # If net.ipv4.tcp_syncookies present in /etc/sysctl.conf, change value to appropriate value
    #	else, add "net.ipv4.tcp_syncookies = value" to /etc/sysctl.conf
    #

    # Strip any search characters in the key arg so that the key can be replaced without
    # adding any search characters to the config file.
    stripped_key=$(sed 's/[\^=\$,;+]*//g' <<< "^net.ipv4.tcp_syncookies")

    # shellcheck disable=SC2059
    printf -v formatted_output "%s = %s" "$stripped_key" "$sysctl_net_ipv4_tcp_syncookies_value"

    # If the key exists, change it. Otherwise, add it to the config_file.
    # We search for the key string followed by a word boundary (matched by \>),
    # so if we search for 'setting', 'setting2' won't match.
    if LC_ALL=C grep -q -m 1 -i -e "^net.ipv4.tcp_syncookies\\>" "${SYSCONFIG_FILE}"; then
        escaped_formatted_output=$(sed -e 's|/|\\/|g' <<< "$formatted_output")
        LC_ALL=C sed -i --follow-symlinks "s/^net.ipv4.tcp_syncookies\\>.*/$escaped_formatted_output/gi" "${SYSCONFIG_FILE}"
    else
        if [[ -s "${SYSCONFIG_FILE}" ]] && [[ -n "$(tail -c 1 -- "${SYSCONFIG_FILE}" || true)" ]]; then
            LC_ALL=C sed -i --follow-symlinks '$a'\\ "${SYSCONFIG_FILE}"
        fi
        printf '%s\n' "$formatted_output" >> "${SYSCONFIG_FILE}"
    fi

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | medium
Reboot: | true
Strategy: | disable

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - CJIS-5.10.1.1
      - DISA-STIG-UBTU-20-010412
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-SC-5(1)
      - NIST-800-53-SC-5(2)
      - NIST-800-53-SC-5(3)(a)
      - PCI-DSS-Req-1.4.1
      - PCI-DSSv4-1.4
      - PCI-DSSv4-1.4.3
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_net_ipv4_tcp_syncookies

    - name: List /etc/sysctl.d/*.conf files
      find:
        paths:
        - /etc/sysctl.d/
        - /run/sysctl.d/
        - /usr/local/lib/sysctl.d/
        contains: ^[\s]*net.ipv4.tcp_syncookies.*$
        patterns: '*.conf'
        file_type: any
      register: find_sysctl_d
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - CJIS-5.10.1.1
      - DISA-STIG-UBTU-20-010412
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-SC-5(1)
      - NIST-800-53-SC-5(2)
      - NIST-800-53-SC-5(3)(a)
      - PCI-DSS-Req-1.4.1
      - PCI-DSSv4-1.4
      - PCI-DSSv4-1.4.3
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_net_ipv4_tcp_syncookies

    - name: Comment out any occurrences of net.ipv4.tcp_syncookies from config files
      replace:
        path: '{{ item.path }}'
        regexp: ^[\s]*net.ipv4.tcp_syncookies
        replace: '#net.ipv4.tcp_syncookies'
      loop: '{{ find_sysctl_d.files }}'
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - CJIS-5.10.1.1
      - DISA-STIG-UBTU-20-010412
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-SC-5(1)
      - NIST-800-53-SC-5(2)
      - NIST-800-53-SC-5(3)(a)
      - PCI-DSS-Req-1.4.1
      - PCI-DSSv4-1.4
      - PCI-DSSv4-1.4.3
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_net_ipv4_tcp_syncookies
    - name: XCCDF Value sysctl_net_ipv4_tcp_syncookies_value # promote to variable
      set_fact:
        sysctl_net_ipv4_tcp_syncookies_value: !!str 1
      tags:
        - always

    - name: Ensure sysctl net.ipv4.tcp_syncookies is set
      sysctl:
        name: net.ipv4.tcp_syncookies
        value: '{{ sysctl_net_ipv4_tcp_syncookies_value }}'
        sysctl_file: /etc/sysctl.conf
        state: present
        reload: true
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - CJIS-5.10.1.1
      - DISA-STIG-UBTU-20-010412
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-SC-5(1)
      - NIST-800-53-SC-5(2)
      - NIST-800-53-SC-5(3)(a)
      - PCI-DSS-Req-1.4.1
      - PCI-DSSv4-1.4
      - PCI-DSSv4-1.4.3
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_net_ipv4_tcp_syncookies

Group Network Parameters for Hosts Only Group contains 3 rules
[ref] If the system is not going to be used as a router, then setting certain kernel parameters ensure that the host will not perform routing of network traffic.

#### Rule Disable Kernel Parameter for Sending ICMP Redirects on all IPv4 Interfaces [ref]

To set the runtime status of the `net.ipv4.conf.all.send_redirects` kernel parameter, run the following command:

    $ sudo sysctl -w net.ipv4.conf.all.send_redirects=0

To make sure that the setting is persistent, add the following line to a file in the directory `/etc/sysctl.d`:

    net.ipv4.conf.all.send_redirects = 0

Rationale: | ICMP redirect messages are used by routers to inform hosts that a more direct route exists for a particular destination. These messages contain information from the system's route table possibly revealing portions of the network topology. The ability to send ICMP redirects is only appropriate for systems acting as routers.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_sysctl_net_ipv4_conf_all_send_redirects

References:

cis-csc | 1, 11, 12, 13, 14, 15, 16, 18, 2, 3, 4, 6, 7, 8, 9
cjis | 5.10.1.1
cobit5 | APO01.06, APO13.01, BAI04.04, BAI10.01, BAI10.02, BAI10.03, BAI10.05, DSS01.03, DSS01.05, DSS03.01, DSS03.05, DSS05.02, DSS05.04, DSS05.05, DSS05.07, DSS06.02, DSS06.06
cui | 3.1.20
disa | CCI-000366
isa-62443-2009 | 4.2.3.4, 4.3.3.4, 4.3.3.5.1, 4.3.3.5.2, 4.3.3.5.3, 4.3.3.5.4, 4.3.3.5.5, 4.3.3.5.6, 4.3.3.5.7, 4.3.3.5.8, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.1, 4.3.3.7.2, 4.3.3.7.3, 4.3.3.7.4, 4.3.4.3.2, 4.3.4.3.3, 4.4.3.3
isa-62443-2013 | SR 1.1, SR 1.10, SR 1.11, SR 1.12, SR 1.13, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.6, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 2.2, SR 2.3, SR 2.4, SR 2.5, SR 2.6, SR 2.7, SR 3.1, SR 3.5, SR 3.8, SR 4.1, SR 4.3, SR 5.1, SR 5.2, SR 5.3, SR 6.2, SR 7.1, SR 7.2, SR 7.6
iso27001-2013 | A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.12.1.1, A.12.1.2, A.12.1.3, A.12.5.1, A.12.6.2, A.13.1.1, A.13.1.2, A.13.1.3, A.13.2.1, A.13.2.2, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, A.14.2.2, A.14.2.3, A.14.2.4, A.17.2.1, A.6.1.2, A.7.1.1, A.7.1.2, A.7.3.1, A.8.2.2, A.8.2.3, A.9.1.1, A.9.1.2, A.9.2.3, A.9.4.1, A.9.4.4, A.9.4.5
nerc-cip | CIP-007-3 R4, CIP-007-3 R4.1, CIP-007-3 R4.2, CIP-007-3 R5.1
nist | CM-7(a), CM-7(b), SC-5, CM-6(a), SC-7(a)
nist-csf | DE.AE-1, DE.CM-1, ID.AM-3, PR.AC-5, PR.DS-4, PR.DS-5, PR.IP-1, PR.PT-3, PR.PT-4
os-srg | SRG-OS-000480-GPOS-00227
cis | 3.2.1
anssi | R12
pcidss4 | 1.4.5, 1.4

Remediation Shell script ⇲

Complexity: | low
Disruption: | medium
Reboot: | true
Strategy: | disable

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    # Comment out any occurrences of net.ipv4.conf.all.send_redirects from /etc/sysctl.d/*.conf files

    for f in /etc/sysctl.d/*.conf /run/sysctl.d/*.conf /usr/local/lib/sysctl.d/*.conf; do

      # skip systemd-sysctl symlink (/etc/sysctl.d/99-sysctl.conf -> /etc/sysctl.conf)
      if [[ "$(readlink -f "$f")" == "/etc/sysctl.conf" ]]; then continue; fi

      matching_list=$(grep -P '^(?!#).*[\s]*net.ipv4.conf.all.send_redirects.*$' $f | uniq )
      if ! test -z "$matching_list"; then
        while IFS= read -r entry; do
          escaped_entry=$(sed -e 's|/|\\/|g' <<< "$entry")
          # comment out "net.ipv4.conf.all.send_redirects" matches to preserve user data
          sed -i --follow-symlinks "s/^${escaped_entry}$/# &/g" $f
        done <<< "$matching_list"
      fi
    done

    #
    # Set sysctl config file which to save the desired value
    #

    SYSCONFIG_FILE="/etc/sysctl.conf"

    #
    # Set runtime for net.ipv4.conf.all.send_redirects
    #
    if [[ "$OSCAP_BOOTC_BUILD" != "YES" ]] ; then
        /sbin/sysctl -q -n -w net.ipv4.conf.all.send_redirects="0"
    fi

    #
    # If net.ipv4.conf.all.send_redirects present in /etc/sysctl.conf, change value to "0"
    #	else, add "net.ipv4.conf.all.send_redirects = 0" to /etc/sysctl.conf
    #

    # Strip any search characters in the key arg so that the key can be replaced without
    # adding any search characters to the config file.
    stripped_key=$(sed 's/[\^=\$,;+]*//g' <<< "^net.ipv4.conf.all.send_redirects")

    # shellcheck disable=SC2059
    printf -v formatted_output "%s = %s" "$stripped_key" "0"

    # If the key exists, change it. Otherwise, add it to the config_file.
    # We search for the key string followed by a word boundary (matched by \>),
    # so if we search for 'setting', 'setting2' won't match.
    if LC_ALL=C grep -q -m 1 -i -e "^net.ipv4.conf.all.send_redirects\\>" "${SYSCONFIG_FILE}"; then
        escaped_formatted_output=$(sed -e 's|/|\\/|g' <<< "$formatted_output")
        LC_ALL=C sed -i --follow-symlinks "s/^net.ipv4.conf.all.send_redirects\\>.*/$escaped_formatted_output/gi" "${SYSCONFIG_FILE}"
    else
        if [[ -s "${SYSCONFIG_FILE}" ]] && [[ -n "$(tail -c 1 -- "${SYSCONFIG_FILE}" || true)" ]]; then
            LC_ALL=C sed -i --follow-symlinks '$a'\\ "${SYSCONFIG_FILE}"
        fi
        printf '%s\n' "$formatted_output" >> "${SYSCONFIG_FILE}"
    fi

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | medium
Reboot: | true
Strategy: | disable

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - CJIS-5.10.1.1
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-SC-5
      - NIST-800-53-SC-7(a)
      - PCI-DSSv4-1.4
      - PCI-DSSv4-1.4.5
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_net_ipv4_conf_all_send_redirects

    - name: List /etc/sysctl.d/*.conf files
      find:
        paths:
        - /etc/sysctl.d/
        - /run/sysctl.d/
        - /usr/local/lib/sysctl.d/
        contains: ^[\s]*net.ipv4.conf.all.send_redirects.*$
        patterns: '*.conf'
        file_type: any
      register: find_sysctl_d
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - CJIS-5.10.1.1
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-SC-5
      - NIST-800-53-SC-7(a)
      - PCI-DSSv4-1.4
      - PCI-DSSv4-1.4.5
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_net_ipv4_conf_all_send_redirects

    - name: Comment out any occurrences of net.ipv4.conf.all.send_redirects from config
        files
      replace:
        path: '{{ item.path }}'
        regexp: ^[\s]*net.ipv4.conf.all.send_redirects
        replace: '#net.ipv4.conf.all.send_redirects'
      loop: '{{ find_sysctl_d.files }}'
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - CJIS-5.10.1.1
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-SC-5
      - NIST-800-53-SC-7(a)
      - PCI-DSSv4-1.4
      - PCI-DSSv4-1.4.5
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_net_ipv4_conf_all_send_redirects

    - name: Ensure sysctl net.ipv4.conf.all.send_redirects is set to 0
      sysctl:
        name: net.ipv4.conf.all.send_redirects
        value: '0'
        sysctl_file: /etc/sysctl.conf
        state: present
        reload: true
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - CJIS-5.10.1.1
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-SC-5
      - NIST-800-53-SC-7(a)
      - PCI-DSSv4-1.4
      - PCI-DSSv4-1.4.5
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_net_ipv4_conf_all_send_redirects

#### Rule Disable Kernel Parameter for Sending ICMP Redirects on all IPv4 Interfaces by Default [ref]

To set the runtime status of the `net.ipv4.conf.default.send_redirects` kernel parameter, run the following command:

    $ sudo sysctl -w net.ipv4.conf.default.send_redirects=0

To make sure that the setting is persistent, add the following line to a file in the directory `/etc/sysctl.d`:

    net.ipv4.conf.default.send_redirects = 0

Rationale: | ICMP redirect messages are used by routers to inform hosts that a more direct route exists for a particular destination. These messages contain information from the system's route table possibly revealing portions of the network topology. The ability to send ICMP redirects is only appropriate for systems acting as routers.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_sysctl_net_ipv4_conf_default_send_redirects

References:

cis-csc | 1, 11, 12, 13, 14, 15, 16, 18, 2, 3, 4, 6, 7, 8, 9
cjis | 5.10.1.1
cobit5 | APO01.06, APO13.01, BAI04.04, BAI10.01, BAI10.02, BAI10.03, BAI10.05, DSS01.03, DSS01.05, DSS03.01, DSS03.05, DSS05.02, DSS05.04, DSS05.05, DSS05.07, DSS06.02, DSS06.06
cui | 3.1.20
disa | CCI-000366
isa-62443-2009 | 4.2.3.4, 4.3.3.4, 4.3.3.5.1, 4.3.3.5.2, 4.3.3.5.3, 4.3.3.5.4, 4.3.3.5.5, 4.3.3.5.6, 4.3.3.5.7, 4.3.3.5.8, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.1, 4.3.3.7.2, 4.3.3.7.3, 4.3.3.7.4, 4.3.4.3.2, 4.3.4.3.3, 4.4.3.3
isa-62443-2013 | SR 1.1, SR 1.10, SR 1.11, SR 1.12, SR 1.13, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.6, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 2.2, SR 2.3, SR 2.4, SR 2.5, SR 2.6, SR 2.7, SR 3.1, SR 3.5, SR 3.8, SR 4.1, SR 4.3, SR 5.1, SR 5.2, SR 5.3, SR 6.2, SR 7.1, SR 7.2, SR 7.6
iso27001-2013 | A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.12.1.1, A.12.1.2, A.12.1.3, A.12.5.1, A.12.6.2, A.13.1.1, A.13.1.2, A.13.1.3, A.13.2.1, A.13.2.2, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, A.14.2.2, A.14.2.3, A.14.2.4, A.17.2.1, A.6.1.2, A.7.1.1, A.7.1.2, A.7.3.1, A.8.2.2, A.8.2.3, A.9.1.1, A.9.1.2, A.9.2.3, A.9.4.1, A.9.4.4, A.9.4.5
nerc-cip | CIP-007-3 R4, CIP-007-3 R4.1, CIP-007-3 R4.2, CIP-007-3 R5.1
nist | CM-7(a), CM-7(b), SC-5, CM-6(a), SC-7(a)
nist-csf | DE.AE-1, DE.CM-1, ID.AM-3, PR.AC-5, PR.DS-4, PR.DS-5, PR.IP-1, PR.PT-3, PR.PT-4
os-srg | SRG-OS-000480-GPOS-00227
cis | 3.2.1
anssi | R12
pcidss4 | 1.4.5, 1.4

Remediation Shell script ⇲

Complexity: | low
Disruption: | medium
Reboot: | true
Strategy: | disable

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    # Comment out any occurrences of net.ipv4.conf.default.send_redirects from /etc/sysctl.d/*.conf files

    for f in /etc/sysctl.d/*.conf /run/sysctl.d/*.conf /usr/local/lib/sysctl.d/*.conf; do

      # skip systemd-sysctl symlink (/etc/sysctl.d/99-sysctl.conf -> /etc/sysctl.conf)
      if [[ "$(readlink -f "$f")" == "/etc/sysctl.conf" ]]; then continue; fi

      matching_list=$(grep -P '^(?!#).*[\s]*net.ipv4.conf.default.send_redirects.*$' $f | uniq )
      if ! test -z "$matching_list"; then
        while IFS= read -r entry; do
          escaped_entry=$(sed -e 's|/|\\/|g' <<< "$entry")
          # comment out "net.ipv4.conf.default.send_redirects" matches to preserve user data
          sed -i --follow-symlinks "s/^${escaped_entry}$/# &/g" $f
        done <<< "$matching_list"
      fi
    done

    #
    # Set sysctl config file which to save the desired value
    #

    SYSCONFIG_FILE="/etc/sysctl.conf"

    #
    # Set runtime for net.ipv4.conf.default.send_redirects
    #
    if [[ "$OSCAP_BOOTC_BUILD" != "YES" ]] ; then
        /sbin/sysctl -q -n -w net.ipv4.conf.default.send_redirects="0"
    fi

    #
    # If net.ipv4.conf.default.send_redirects present in /etc/sysctl.conf, change value to "0"
    #	else, add "net.ipv4.conf.default.send_redirects = 0" to /etc/sysctl.conf
    #

    # Strip any search characters in the key arg so that the key can be replaced without
    # adding any search characters to the config file.
    stripped_key=$(sed 's/[\^=\$,;+]*//g' <<< "^net.ipv4.conf.default.send_redirects")

    # shellcheck disable=SC2059
    printf -v formatted_output "%s = %s" "$stripped_key" "0"

    # If the key exists, change it. Otherwise, add it to the config_file.
    # We search for the key string followed by a word boundary (matched by \>),
    # so if we search for 'setting', 'setting2' won't match.
    if LC_ALL=C grep -q -m 1 -i -e "^net.ipv4.conf.default.send_redirects\\>" "${SYSCONFIG_FILE}"; then
        escaped_formatted_output=$(sed -e 's|/|\\/|g' <<< "$formatted_output")
        LC_ALL=C sed -i --follow-symlinks "s/^net.ipv4.conf.default.send_redirects\\>.*/$escaped_formatted_output/gi" "${SYSCONFIG_FILE}"
    else
        if [[ -s "${SYSCONFIG_FILE}" ]] && [[ -n "$(tail -c 1 -- "${SYSCONFIG_FILE}" || true)" ]]; then
            LC_ALL=C sed -i --follow-symlinks '$a'\\ "${SYSCONFIG_FILE}"
        fi
        printf '%s\n' "$formatted_output" >> "${SYSCONFIG_FILE}"
    fi

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | medium
Reboot: | true
Strategy: | disable

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - CJIS-5.10.1.1
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-SC-5
      - NIST-800-53-SC-7(a)
      - PCI-DSSv4-1.4
      - PCI-DSSv4-1.4.5
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_net_ipv4_conf_default_send_redirects

    - name: List /etc/sysctl.d/*.conf files
      find:
        paths:
        - /etc/sysctl.d/
        - /run/sysctl.d/
        - /usr/local/lib/sysctl.d/
        contains: ^[\s]*net.ipv4.conf.default.send_redirects.*$
        patterns: '*.conf'
        file_type: any
      register: find_sysctl_d
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - CJIS-5.10.1.1
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-SC-5
      - NIST-800-53-SC-7(a)
      - PCI-DSSv4-1.4
      - PCI-DSSv4-1.4.5
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_net_ipv4_conf_default_send_redirects

    - name: Comment out any occurrences of net.ipv4.conf.default.send_redirects from config
        files
      replace:
        path: '{{ item.path }}'
        regexp: ^[\s]*net.ipv4.conf.default.send_redirects
        replace: '#net.ipv4.conf.default.send_redirects'
      loop: '{{ find_sysctl_d.files }}'
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - CJIS-5.10.1.1
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-SC-5
      - NIST-800-53-SC-7(a)
      - PCI-DSSv4-1.4
      - PCI-DSSv4-1.4.5
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_net_ipv4_conf_default_send_redirects

    - name: Ensure sysctl net.ipv4.conf.default.send_redirects is set to 0
      sysctl:
        name: net.ipv4.conf.default.send_redirects
        value: '0'
        sysctl_file: /etc/sysctl.conf
        state: present
        reload: true
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - CJIS-5.10.1.1
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-SC-5
      - NIST-800-53-SC-7(a)
      - PCI-DSSv4-1.4
      - PCI-DSSv4-1.4.5
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_net_ipv4_conf_default_send_redirects

#### Rule Disable Kernel Parameter for IP Forwarding on IPv4 Interfaces [ref]

To set the runtime status of the `net.ipv4.ip_forward` kernel parameter, run the following command:

    $ sudo sysctl -w net.ipv4.ip_forward=0

To make sure that the setting is persistent, add the following line to a file in the directory `/etc/sysctl.d`:

    net.ipv4.ip_forward = 0

Warning: Certain technologies such as virtual machines, containers, etc. rely on IPv4 forwarding to enable and use networking. Disabling IPv4 forwarding would cause those technologies to stop working. Therefore, this rule should not be used in profiles or benchmarks that target usage of IPv4 forwarding.

Rationale: | Routing protocol daemons are typically used on routers to exchange network topology information with other routers. If this capability is used when not required, system network information may be unnecessarily transmitted across the network.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_sysctl_net_ipv4_ip_forward

References:

cis-csc | 1, 11, 12, 13, 14, 15, 16, 2, 3, 7, 8, 9
cobit5 | APO13.01, BAI04.04, BAI10.01, BAI10.02, BAI10.03, BAI10.05, DSS01.03, DSS03.05, DSS05.02, DSS05.05, DSS05.07, DSS06.06
cui | 3.1.20
disa | CCI-000366
isa-62443-2009 | 4.3.3.5.1, 4.3.3.5.2, 4.3.3.5.3, 4.3.3.5.4, 4.3.3.5.5, 4.3.3.5.6, 4.3.3.5.7, 4.3.3.5.8, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.1, 4.3.3.7.2, 4.3.3.7.3, 4.3.3.7.4, 4.3.4.3.2, 4.3.4.3.3
isa-62443-2013 | SR 1.1, SR 1.10, SR 1.11, SR 1.12, SR 1.13, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.6, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 2.2, SR 2.3, SR 2.4, SR 2.5, SR 2.6, SR 2.7, SR 3.1, SR 3.5, SR 3.8, SR 4.1, SR 4.3, SR 5.1, SR 5.2, SR 5.3, SR 6.2, SR 7.1, SR 7.2, SR 7.6
iso27001-2013 | A.12.1.2, A.12.1.3, A.12.5.1, A.12.6.2, A.13.1.1, A.13.2.1, A.14.1.3, A.14.2.2, A.14.2.3, A.14.2.4, A.17.2.1, A.9.1.2
nerc-cip | CIP-007-3 R4, CIP-007-3 R4.1, CIP-007-3 R4.2, CIP-007-3 R5.1
nist | CM-7(a), CM-7(b), SC-5, CM-6(a), SC-7(a)
nist-csf | DE.CM-1, PR.DS-4, PR.IP-1, PR.PT-3, PR.PT-4
pcidss | Req-1.3.1, Req-1.3.2
os-srg | SRG-OS-000480-GPOS-00227
cis | 3.2.2
anssi | R12
pcidss4 | 1.4.3, 1.4

Remediation Shell script ⇲

Complexity: | low
Disruption: | medium
Reboot: | true
Strategy: | disable

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    # Comment out any occurrences of net.ipv4.ip_forward from /etc/sysctl.d/*.conf files

    for f in /etc/sysctl.d/*.conf /run/sysctl.d/*.conf /usr/local/lib/sysctl.d/*.conf; do

      # skip systemd-sysctl symlink (/etc/sysctl.d/99-sysctl.conf -> /etc/sysctl.conf)
      if [[ "$(readlink -f "$f")" == "/etc/sysctl.conf" ]]; then continue; fi

      matching_list=$(grep -P '^(?!#).*[\s]*net.ipv4.ip_forward.*$' $f | uniq )
      if ! test -z "$matching_list"; then
        while IFS= read -r entry; do
          escaped_entry=$(sed -e 's|/|\\/|g' <<< "$entry")
          # comment out "net.ipv4.ip_forward" matches to preserve user data
          sed -i --follow-symlinks "s/^${escaped_entry}$/# &/g" $f
        done <<< "$matching_list"
      fi
    done

    #
    # Set sysctl config file which to save the desired value
    #

    SYSCONFIG_FILE="/etc/sysctl.conf"

    #
    # Set runtime for net.ipv4.ip_forward
    #
    if [[ "$OSCAP_BOOTC_BUILD" != "YES" ]] ; then
        /sbin/sysctl -q -n -w net.ipv4.ip_forward="0"
    fi

    #
    # If net.ipv4.ip_forward present in /etc/sysctl.conf, change value to "0"
    #	else, add "net.ipv4.ip_forward = 0" to /etc/sysctl.conf
    #

    # Strip any search characters in the key arg so that the key can be replaced without
    # adding any search characters to the config file.
    stripped_key=$(sed 's/[\^=\$,;+]*//g' <<< "^net.ipv4.ip_forward")

    # shellcheck disable=SC2059
    printf -v formatted_output "%s = %s" "$stripped_key" "0"

    # If the key exists, change it. Otherwise, add it to the config_file.
    # We search for the key string followed by a word boundary (matched by \>),
    # so if we search for 'setting', 'setting2' won't match.
    if LC_ALL=C grep -q -m 1 -i -e "^net.ipv4.ip_forward\\>" "${SYSCONFIG_FILE}"; then
        escaped_formatted_output=$(sed -e 's|/|\\/|g' <<< "$formatted_output")
        LC_ALL=C sed -i --follow-symlinks "s/^net.ipv4.ip_forward\\>.*/$escaped_formatted_output/gi" "${SYSCONFIG_FILE}"
    else
        if [[ -s "${SYSCONFIG_FILE}" ]] && [[ -n "$(tail -c 1 -- "${SYSCONFIG_FILE}" || true)" ]]; then
            LC_ALL=C sed -i --follow-symlinks '$a'\\ "${SYSCONFIG_FILE}"
        fi
        printf '%s\n' "$formatted_output" >> "${SYSCONFIG_FILE}"
    fi

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | medium
Reboot: | true
Strategy: | disable

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-SC-5
      - NIST-800-53-SC-7(a)
      - PCI-DSS-Req-1.3.1
      - PCI-DSS-Req-1.3.2
      - PCI-DSSv4-1.4
      - PCI-DSSv4-1.4.3
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_net_ipv4_ip_forward

    - name: List /etc/sysctl.d/*.conf files
      find:
        paths:
        - /etc/sysctl.d/
        - /run/sysctl.d/
        - /usr/local/lib/sysctl.d/
        contains: ^[\s]*net.ipv4.ip_forward.*$
        patterns: '*.conf'
        file_type: any
      register: find_sysctl_d
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-SC-5
      - NIST-800-53-SC-7(a)
      - PCI-DSS-Req-1.3.1
      - PCI-DSS-Req-1.3.2
      - PCI-DSSv4-1.4
      - PCI-DSSv4-1.4.3
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_net_ipv4_ip_forward

    - name: Comment out any occurrences of net.ipv4.ip_forward from config files
      replace:
        path: '{{ item.path }}'
        regexp: ^[\s]*net.ipv4.ip_forward
        replace: '#net.ipv4.ip_forward'
      loop: '{{ find_sysctl_d.files }}'
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-SC-5
      - NIST-800-53-SC-7(a)
      - PCI-DSS-Req-1.3.1
      - PCI-DSS-Req-1.3.2
      - PCI-DSSv4-1.4
      - PCI-DSSv4-1.4.3
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_net_ipv4_ip_forward

    - name: Ensure sysctl net.ipv4.ip_forward is set to 0
      sysctl:
        name: net.ipv4.ip_forward
        value: '0'
        sysctl_file: /etc/sysctl.conf
        state: present
        reload: true
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-171-3.1.20
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-SC-5
      - NIST-800-53-SC-7(a)
      - PCI-DSS-Req-1.3.1
      - PCI-DSS-Req-1.3.2
      - PCI-DSSv4-1.4
      - PCI-DSSv4-1.4.3
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_net_ipv4_ip_forward

Group nftables Group contains 9 rules

[ref] `If firewalld or iptables are being used in your environment, please follow the guidance in their respective section and pass-over the guidance in this section.`
nftables is a subsystem of the Linux kernel providing filtering and classification of network packets/datagrams/frames and is the successor to iptables. The biggest change with the successor nftables is its simplicity. With iptables, we have to configure every single rule and use the syntax which can be compared with normal commands. With nftables, the simpler syntax, much like BPF (Berkely Packet Filter) means shorter lines and less repetition. Support for nftables should also be compiled into the kernel, together with the related nftables modules.
It is available in Linux kernels >= 3.13. Please ensure that your kernel supports nftables before choosing this option.

#### Rule Install nftables Package [ref]

nftables provides a new in-kernel packet classification framework that is based on a network-specific Virtual Machine (VM) and a new nft userspace command line tool. nftables reuses the existing Netfilter subsystems such as the existing hook infrastructure, the connection tracking system, NAT, userspace queuing and logging subsystem. The `nftables` package can be installed with the following command:

    $ apt-get install nftables

Rationale: | `nftables` is a subsystem of the Linux kernel that can protect against threats originating from within a corporate network to include malicious mobile code and poorly configured software on a host.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_package_nftables_installed

References:

cis | 3.5.2.1
pcidss4 | 1.2.1, 1.2

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | enable

    # Remediation is applicable only in certain platforms
    if ( dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed ); then

    DEBIAN_FRONTEND=noninteractive apt-get install -y "nftables"

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation OSBuild Blueprint snippet ⇲

    [[packages]]
    name = "nftables"
    version = "*"

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | enable

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - PCI-DSSv4-1.2
      - PCI-DSSv4-1.2.1
      - enable_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - package_nftables_installed

    - name: Ensure nftables is installed
      package:
        name: nftables
        state: present
      when: ( "linux-base" in ansible_facts.packages )
      tags:
      - PCI-DSSv4-1.2
      - PCI-DSSv4-1.2.1
      - enable_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - package_nftables_installed

Remediation Puppet snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | enable

    include install_nftables

    class install_nftables {
      package { 'nftables':
        ensure => 'installed',
      }
    }

#### Rule Uninstall nftables package [ref]

nftables is a subsystem of the Linux kernel providing filtering and classification of network packets/datagrams/frames and is the successor to iptables. The `nftables` package can be removed with the following command:

    $ apt-get remove nftables

Rationale: | Running both `firewalld` and `nftables` may lead to conflict.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_package_nftables_removed

References:

cis | 3.5.3.1.2

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    # CAUTION: This remediation script will remove nftables
    #	   from the system, and may remove any packages
    #	   that depend on nftables. Execute this
    #	   remediation AFTER testing on a non-production
    #	   system!

    DEBIAN_FRONTEND=noninteractive apt-get remove -y "nftables"

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    - name: Ensure nftables is removed
      package:
        name: nftables
        state: absent
      tags:
      - disable_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - package_nftables_removed

Remediation Puppet snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    include remove_nftables

    class remove_nftables {
      package { 'nftables':
        ensure => 'purged',
      }
    }

#### Rule Verify nftables Service is Enabled [ref]

The nftables service allows for the loading of nftables rulesets during boot, or starting on the nftables service The `nftables` service can be enabled with the following command:

    $ sudo systemctl enable nftables.service

Rationale: | The nftables service restores the nftables rules from the rules files referenced in the `/etc/sysconfig/nftables.conf` file during boot or the starting of the nftables service
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_service_nftables_enabled

References:

cis | 3.5.2.9

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | enable

    # Remediation is applicable only in certain platforms
    if ( dpkg-query --show --showformat='${db:Status-Status}\n' 'nftables' 2>/dev/null | grep -q '^installed' && dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed ); then

    SYSTEMCTL_EXEC='/usr/bin/systemctl'
    "$SYSTEMCTL_EXEC" unmask 'nftables.service'
    if [[ $("$SYSTEMCTL_EXEC" is-system-running) != "offline" ]]; then
      "$SYSTEMCTL_EXEC" start 'nftables.service'
    fi
    "$SYSTEMCTL_EXEC" enable 'nftables.service'

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation OSBuild Blueprint snippet ⇲

    [customizations.services]
    enabled = ["nftables"]

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | enable

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - enable_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - service_nftables_enabled

    - name: Verify nftables Service is Enabled - Enable service nftables
      block:

      - name: Gather the package facts
        package_facts:
          manager: auto

      - name: Verify nftables Service is Enabled - Enable Service nftables
        ansible.builtin.systemd:
          name: nftables
          enabled: true
          state: started
          masked: false
        when:
        - '"nftables" in ansible_facts.packages'
      when: ( "nftables" in ansible_facts.packages and "linux-base" in ansible_facts.packages
        )
      tags:
      - enable_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - service_nftables_enabled

Remediation Puppet snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | enable

    include enable_nftables

    class enable_nftables {
      service {'nftables':
        enable => true,
        ensure => 'running',
      }
    }

#### Rule Verify nftables Service is Disabled [ref]

nftables is a subsystem of the Linux kernel providing filtering and classification of network packets/datagrams/frames and is the successor to iptables. The `nftables` service can be disabled with the following command:

    systemctl disable nftables

Rationale: | Running both `firewalld` and `nftables` may lead to conflict. `nftables` is actually one of the backends for `firewalld` management tools.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_service_nftables_disabled

References:

cis | 3.5.3.1.2
pcidss4 | 1.2.1, 1.2

Remediation Kubernetes snippet ⇲

Complexity: | low
Disruption: | medium
Reboot: | true
Strategy: | disable

    apiVersion: machineconfiguration.openshift.io/v1
    kind: MachineConfig
    spec:
      config:
        ignition:
          version: 3.1.0
        systemd:
          units:
          - name: nftables.service
            enabled: false
            mask: true
          - name: nftables.socket
            enabled: false
            mask: true

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    # Remediation is applicable only in certain platforms
    if ( dpkg-query --show --showformat='${db:Status-Status}\n' 'firewalld' 2>/dev/null | grep -q '^installed' && dpkg-query --show --showformat='${db:Status-Status}\n' 'nftables' 2>/dev/null | grep -q '^installed' && dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed ); then

    SYSTEMCTL_EXEC='/usr/bin/systemctl'
    if [[ $("$SYSTEMCTL_EXEC" is-system-running) != "offline" ]]; then
      "$SYSTEMCTL_EXEC" stop 'nftables.service'
    fi
    "$SYSTEMCTL_EXEC" disable 'nftables.service'
    "$SYSTEMCTL_EXEC" mask 'nftables.service'
    # Disable socket activation if we have a unit file for it
    if "$SYSTEMCTL_EXEC" -q list-unit-files nftables.socket; then
        if [[ $("$SYSTEMCTL_EXEC" is-system-running) != "offline" ]]; then
          "$SYSTEMCTL_EXEC" stop 'nftables.socket'
        fi
        "$SYSTEMCTL_EXEC" mask 'nftables.socket'
    fi
    # The service may not be running because it has been started and failed,
    # so let's reset the state so OVAL checks pass.
    # Service should be 'inactive', not 'failed' after reboot though.
    "$SYSTEMCTL_EXEC" reset-failed 'nftables.service' || true

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation OSBuild Blueprint snippet ⇲

    [customizations.services]
    masked = ["nftables"]

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - PCI-DSSv4-1.2
      - PCI-DSSv4-1.2.1
      - disable_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - service_nftables_disabled

    - name: Verify nftables Service is Disabled - Collect systemd Services Present in
        the System
      ansible.builtin.command: systemctl -q list-unit-files --type service
      register: service_exists
      changed_when: false
      failed_when: service_exists.rc not in [0, 1]
      check_mode: false
      when: ( "firewalld" in ansible_facts.packages and "nftables" in ansible_facts.packages
        and "linux-base" in ansible_facts.packages )
      tags:
      - PCI-DSSv4-1.2
      - PCI-DSSv4-1.2.1
      - disable_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - service_nftables_disabled

    - name: Verify nftables Service is Disabled - Ensure nftables.service is Masked
      ansible.builtin.systemd:
        name: nftables.service
        state: stopped
        enabled: false
        masked: true
      when:
      - ( "firewalld" in ansible_facts.packages and "nftables" in ansible_facts.packages
        and "linux-base" in ansible_facts.packages )
      - service_exists.stdout_lines is search("nftables.service", multiline=True)
      tags:
      - PCI-DSSv4-1.2
      - PCI-DSSv4-1.2.1
      - disable_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - service_nftables_disabled

    - name: Unit Socket Exists - nftables.socket
      ansible.builtin.command: systemctl -q list-unit-files nftables.socket
      register: socket_file_exists
      changed_when: false
      failed_when: socket_file_exists.rc not in [0, 1]
      check_mode: false
      when: ( "firewalld" in ansible_facts.packages and "nftables" in ansible_facts.packages
        and "linux-base" in ansible_facts.packages )
      tags:
      - PCI-DSSv4-1.2
      - PCI-DSSv4-1.2.1
      - disable_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - service_nftables_disabled

    - name: Verify nftables Service is Disabled - Disable Socket nftables
      ansible.builtin.systemd:
        name: nftables.socket
        enabled: false
        state: stopped
        masked: true
      when:
      - ( "firewalld" in ansible_facts.packages and "nftables" in ansible_facts.packages
        and "linux-base" in ansible_facts.packages )
      - socket_file_exists.stdout_lines is search("nftables.socket", multiline=True)
      tags:
      - PCI-DSSv4-1.2
      - PCI-DSSv4-1.2.1
      - disable_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - service_nftables_disabled

Remediation Puppet snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | enable

    include disable_nftables

    class disable_nftables {
      service {'nftables':
        enable => false,
        ensure => 'stopped',
      }
    }

#### Rule Ensure nftables Default Deny Firewall Policy [ref]

Base chain policy is the default verdict that will be applied to packets reaching the end of the chain. There are two policies: accept (Default) and drop. If the policy is set to accept, the firewall will accept any packet that is not configured to be denied and the packet will continue traversing the network stack. {% if 'ubuntu' in product %} Run the following commands and verify that base chains contain a policy of DROP.

    $ nft list ruleset | grep 'hook input'
    type filter hook input priority 0; policy drop;
    $ nft list ruleset | grep 'hook forward'
    type filter hook forward priority 0; policy drop;
    $ nft list ruleset | grep 'hook output'
    type filter hook output priority 0; policy drop;

Warning: Changing firewall settings while connected over network can result in being locked out of the system.

Rationale: | It is easier to allow acceptable usage than to block unacceptable usage.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_nftables_ensure_default_deny_policy

References:

cis | 3.5.2.8
pcidss4 | 1.3.1, 1.3

#### Rule Ensure nftables Rules are Permanent [ref]

nftables is a subsystem of the Linux kernel providing filtering and classification of network packets/datagrams/frames. The nftables service reads the /etc/nftables.conf file for a nftables file or files to include in the nftables ruleset. A nftables ruleset containing the input, forward, and output base chains allow network traffic to be filtered.
Rationale: | Changes made to nftables ruleset only affect the live system, you will also need to configure the nftables ruleset to apply on boot
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_nftables_rules_permanent

References:

cis | 3.5.2.10

Remediation Shell script ⇲

Complexity: | low
Disruption: | high
Reboot: | false
Strategy: | restrict

    # Remediation is applicable only in certain platforms
    if ( dpkg-query --show --showformat='${db:Status-Status}\n' 'nftables' 2>/dev/null | grep -q '^installed' ); then

    var_nftables_master_config_file='/etc/nftables.conf'

    var_nftables_family='inet'

    if [ ! -f "${var_nftables_master_config_file}" ]; then
        touch "${var_nftables_master_config_file}"
    fi

    nft list ruleset > "/etc/${var_nftables_family}-filter.rules"

    grep -qxF 'include "/etc/'"${var_nftables_family}"'-filter.rules"' "${var_nftables_master_config_file}" \
        || echo 'include "/etc/'"${var_nftables_family}"'-filter.rules"' >> "${var_nftables_master_config_file}"

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

#### Rule Ensure Base Chains Exist for Nftables [ref]

Tables in nftables hold chains. Each table only has one address family and only applies to packets of this family. Tables can have one of six families. Chains are containers for rules. They exist in two kinds, base chains and regular chains. A base chain is an entry point for packets from the networking stack, a regular chain may be used as jump target and is used for better rule organization.
Warning: Configuring rules over ssh, by creating a base chain with policy drop will cause loss of connectivity. Ensure that a rule allowing ssh has been added to the base chain prior to setting the base cahin's policy to drop

Rationale: | If a base chain doesn't exist with a hook for input, forward, and delete, packets that would flow through those chains will not be touched by nftables.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_set_nftables_base_chain

References:

cis | 3.5.2.5

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | restrict

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}\n' 'nftables' 2>/dev/null | grep -q '^installed'; then

    #Name of the table
    var_nftables_table='filter'

    #Familiy of the table
    var_nftables_family='inet'

    #Name(s) of base chain
    var_nftables_base_chain_names='input,forward,output'

    #Type(s) of base chain
    var_nftables_base_chain_types='filter,filter,filter'

    # Hooks for base chain
    var_nftables_base_chain_hooks='input,forward,output'

    #Priority
    var_nftables_base_chain_priorities='0,0,0'

    #Policy
    var_nftables_base_chain_policies='accept,accept,accept'

    #Transfer some of strings to arrays
    IFS="," read -r -a  names <<< "$var_nftables_base_chain_names"
    IFS="," read -r -a  types <<< "$var_nftables_base_chain_types"
    IFS="," read -r -a  hooks <<< "$var_nftables_base_chain_hooks"
    IFS="," read -r -a  priorities <<< "$var_nftables_base_chain_priorities"
    IFS="," read -r -a  policies <<< "$var_nftables_base_chain_policies"

    my_cmd="nft list tables | grep '$var_nftables_family $var_nftables_table'"
    eval IS_TABLE_EXIST=\$\($my_cmd\)
    if [ -z "$IS_TABLE_EXIST" ]
    then
      # We create a table and add chains to it
      nft create table "$var_nftables_family" "$var_nftables_table"
      num_of_chains=${#names[@]}
      for ((i=0; i < num_of_chains; i++))
      do
       chain_to_add="add chain $var_nftables_family $var_nftables_table ${names[$i]} { type ${types[$i]} hook ${hooks[$i]} priority ${priorities[$i]} ; policy ${policies[$i]} ; }"
       my_cmd="nft '$chain_to_add'"
       eval $my_cmd
      done
    else
      # We add missing chains to the existing table
      num_of_chains=${#names[@]}
      for ((i=0; i < num_of_chains; i++))
      do
        IS_CHAIN_EXIST=$(nft list table "$var_nftables_family" "$var_nftables_table" | grep "hook ${hooks[$i]}")
        if [ -z "$IS_CHAIN_EXIST" ]
          then
            chain_to_add="add chain '$var_nftables_family' '$var_nftables_table' ${names[$i]} { type ${types[$i]} hook ${hooks[$i]} priority ${priorities[$i]} ; policy ${policies[$i]} ; }"
            my_cmd="nft '$chain_to_add'"
            eval $my_cmd
        fi
      done
    fi

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | restrict

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy
      - set_nftables_base_chain
    - name: XCCDF Value var_nftables_table # promote to variable
      set_fact:
        var_nftables_table: !!str filter
      tags:
        - always
    - name: XCCDF Value var_nftables_family # promote to variable
      set_fact:
        var_nftables_family: !!str inet
      tags:
        - always
    - name: XCCDF Value var_nftables_base_chain_names # promote to variable
      set_fact:
        var_nftables_base_chain_names: !!str input,forward,output
      tags:
        - always
    - name: XCCDF Value var_nftables_base_chain_types # promote to variable
      set_fact:
        var_nftables_base_chain_types: !!str filter,filter,filter
      tags:
        - always
    - name: XCCDF Value var_nftables_base_chain_hooks # promote to variable
      set_fact:
        var_nftables_base_chain_hooks: !!str input,forward,output
      tags:
        - always
    - name: XCCDF Value var_nftables_base_chain_priorities # promote to variable
      set_fact:
        var_nftables_base_chain_priorities: !!str 0,0,0
      tags:
        - always
    - name: XCCDF Value var_nftables_base_chain_policies # promote to variable
      set_fact:
        var_nftables_base_chain_policies: !!str accept,accept,accept
      tags:
        - always

    - name: Ensure Base Chains Exist for Nftables - Check Existence of Nftables Table
      ansible.builtin.shell: nft list tables | grep '{{ var_nftables_family }} {{ var_nftables_table
        }}'
      register: existing_nftables
      changed_when: false
      failed_when: false
      when: '"nftables" in ansible_facts.packages'
      tags:
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy
      - set_nftables_base_chain

    - name: Ensure Base Chains Exist for Nftables - Set NFTables Table
      ansible.builtin.command: nft create table {{ var_nftables_family }} {{ var_nftables_table
        }}
      when:
      - '"nftables" in ansible_facts.packages'
      - existing_nftables is not skipped and existing_nftables.rc > 0
      tags:
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy
      - set_nftables_base_chain

    - name: Ensure Base Chains Exist for Nftables - Add Base Chains
      ansible.builtin.command: nft 'add chain {{ var_nftables_family }} {{ var_nftables_table
        }} {{ item.0 }} { type {{ item.1 }} hook {{ item.2 }} priority {{ item.3 }} ;
        policy {{ item.4 }} ; }'
      with_together:
      - '{{ var_nftables_base_chain_names.split(",") }}'
      - '{{ var_nftables_base_chain_types.split(",") }}'
      - '{{ var_nftables_base_chain_hooks.split(",") }}'
      - '{{ var_nftables_base_chain_priorities.split(",") }}'
      - '{{ var_nftables_base_chain_policies.split(",") }}'
      when: '"nftables" in ansible_facts.packages'
      tags:
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy
      - set_nftables_base_chain

#### Rule Set nftables Configuration for Loopback Traffic [ref]

Configure the loopback interface to accept traffic. Configure all other interfaces to deny traffic to the loopback network.
Warning: Changing firewall settings while connected over network can result in being locked out of the system. Keep in mind the remediation makes changes only to the running system, in order to keep the changes need to take care to save the nft settings to the relvant configutation files.

Rationale: | Loopback traffic is generated between processes on machine and is typically critical to operation of the system. The loopback interface is the only place that loopback network traffic should be seen, all other interfaces should ignore traffic on this network as an anti-spoofing measure.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_set_nftables_loopback_traffic

References:

pcidss | Req-1.4.1
cis | 3.5.2.6

Remediation Shell script ⇲

    # Remediation is applicable only in certain platforms
    if ( dpkg-query --show --showformat='${db:Status-Status}\n' 'nftables' 2>/dev/null | grep -q '^installed' ); then

    var_nftables_family='inet'

    grubfile="/boot/grub/grub.cfg"

    # Implement the loopback rules:
    nft add rule inet filter input iif lo accept
    nft add rule inet filter input ip saddr 127.0.0.0/8 counter drop

    # Check IPv6 is disabled, if false implement IPv6 loopback rules
    disabled="false"
    [ -f "$grubfile" ] && ! grep "^\s*linux" "$grubfile" | grep -vq "ipv6.disable=1" && disabled="true"

    grep -Eq "^\s*net\.ipv6\.conf\.all\.disable_ipv6\s*=\s*1\b(\s+#.*)?$" \
    /etc/sysctl.conf /etc/sysctl.d/*.conf && \
    grep -Eq "^\s*net\.ipv6\.conf\.default\.disable_ipv6\s*=\s*1\b(\s+#.*)?$" \
    /etc/sysctl.conf /etc/sysctl.d/*.conf && sysctl net.ipv6.conf.all.disable_ipv6 | \
    grep -Eq "^\s*net\.ipv6\.conf\.all\.disable_ipv6\s*=\s*1\b(\s+#.*)?$" && \
    sysctl net.ipv6.conf.default.disable_ipv6 | \
    grep -Eq "^\s*net\.ipv6\.conf\.default\.disable_ipv6\s*=\s*1\b(\s+#.*)?$" && disabled="true"

    # Is IPv6 Disabled? (true/false)
    if [ "$disabled" = false ] ; then
        nft add rule inet filter input ip6 saddr ::1 counter drop
    fi

    nft list ruleset > "/etc/${var_nftables_family}-filter.rules"

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | restrict

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - PCI-DSS-Req-1.4.1
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy
      - set_nftables_loopback_traffic

    - name: Implement Loopback Rules
      ansible.builtin.command: nft add rule inet filter input iif lo accept
      when: ( "nftables" in ansible_facts.packages )
      tags:
      - PCI-DSS-Req-1.4.1
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy
      - set_nftables_loopback_traffic

    - name: Create Rule to Drop Input IP Address from Loopback
      ansible.builtin.command: nft add rule inet filter input ip saddr 127.0.0.0/8 counter
        drop
      when: ( "nftables" in ansible_facts.packages )
      tags:
      - PCI-DSS-Req-1.4.1
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy
      - set_nftables_loopback_traffic

    - name: Check if IPv6 is Disabled in grub Configuration
      ansible.builtin.shell: |
        [ -z "$(grep "^\s*linux" /boot/grub2/grub.cfg | grep -v ipv6.disabled=1)" ]
      register: ipv6_status
      when: ( "nftables" in ansible_facts.packages )
      tags:
      - PCI-DSS-Req-1.4.1
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy
      - set_nftables_loopback_traffic

    - name: Check sysctl value of net.ipv6.conf.all.disable_ipv6
      sysctl:
        name: net.ipv6.conf.all.disable_ipv6
        state: present
        value: '1'
      check_mode: true
      register: sysctl_ipv6_all
      when: ( "nftables" in ansible_facts.packages )
      tags:
      - PCI-DSS-Req-1.4.1
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy
      - set_nftables_loopback_traffic

    - name: Check sysctl value of net.ipv6.conf.default.disable_ipv6
      sysctl:
        name: net.ipv6.conf.default.disable_ipv6
        state: present
        value: '1'
      check_mode: true
      register: sysctl_ipv6_default
      when: ( "nftables" in ansible_facts.packages )
      tags:
      - PCI-DSS-Req-1.4.1
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy
      - set_nftables_loopback_traffic

    - name: Implement IPv6 loopback rules
      ansible.builtin.command: nft add rule inet filter input ip6 saddr ::1 counter drop
      when:
      - ( "nftables" in ansible_facts.packages )
      - ipv6_status is not skipped
      - sysctl_ipv6_default is not skipped
      - sysctl_ipv6_all is not skipped
      - ipv6_status.rc == 0 or sysctl_ipv6_all.found > 0 or sysctl_ipv6_default.found
        > 0
      tags:
      - PCI-DSS-Req-1.4.1
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy
      - set_nftables_loopback_traffic

#### Rule Ensure a Table Exists for Nftables [ref]

Tables in nftables hold chains. Each table only has one address family and only applies to packets of this family. Tables can have one of six families.
Warning: Adding or editing rules in a running nftables can cause loss of connectivity to the system.
Warning: Both the SCE check and remediation for this rule only consider runtime settings. There is no specific file to check as it depends on each site's policy. Therefore, check and remediation use the nft command directly. The fix is not persistent across system reboots.
Warning: SCE check does not support variables, therefore the SCE check in this rule only checks the address family, regardless of the table name.

Rationale: | Nftables doesn't have any default tables. Without a table being built, nftables will not filter network traffic.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_set_nftables_table

References:

cis | 3.5.2.4

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | restrict

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}\n' 'nftables' 2>/dev/null | grep -q '^installed'; then

    var_nftables_family='inet'

    var_nftables_table='filter'

    if ! nft list table $var_nftables_family $var_nftables_table; then
      nft create table "$var_nftables_family" "$var_nftables_table"
    fi

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | restrict

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy
      - set_nftables_table
    - name: XCCDF Value var_nftables_family # promote to variable
      set_fact:
        var_nftables_family: !!str inet
      tags:
        - always
    - name: XCCDF Value var_nftables_table # promote to variable
      set_fact:
        var_nftables_table: !!str filter
      tags:
        - always

    - name: Collect Existing Nftables
      ansible.builtin.command: nft list table {{ var_nftables_family }} {{ var_nftables_table
        }}
      register: result_nftables_table_family
      changed_when: false
      failed_when: result_nftables_table_family.rc not in [0, 1]
      when: '"nftables" in ansible_facts.packages'
      tags:
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy
      - set_nftables_table

    - name: Set Nftable Table
      ansible.builtin.command: nft create table {{ var_nftables_family }} {{ var_nftables_table
        }}
      when:
      - '"nftables" in ansible_facts.packages'
      - result_nftables_table_family is not skipped
      - result_nftables_table_family.rc != 0
      tags:
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy
      - set_nftables_table

Group Uncomplicated Firewall (ufw) Group contains 5 rules

[ref] The Linux kernel in Ubuntu provides a packet filtering system called netfilter, and the traditional interface for manipulating netfilter are the iptables suite of commands. iptables provide a complete firewall solution that is both highly configurable and highly flexible. Becoming proficient in iptables takes time, and getting started with netfilter firewalling using only iptables can be a daunting task. As a result, many frontends for iptables have been created over the years, each trying to achieve a different result and targeting a different audience. The Uncomplicated Firewall (ufw) is a frontend for iptables and is particularly well-suited for host-based firewalls. ufw provides a framework for managing netfilter, as well as a command-line interface for manipulating the firewall. ufw aims to provide an easy to use interface for people unfamiliar with firewall concepts, while at the same time simplifies complicated iptables commands to help an administrator who knows what he or she is doing. ufw is an upstream for other distributions and graphical frontends.

#### Rule Install ufw Package [ref]

The `ufw` package can be installed with the following command:

    $ apt-get install ufw

Rationale: | `ufw` controls the Linux kernel network packet filtering code. `ufw` allows system operators to set up firewalls and IP masquerading, etc.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_package_ufw_installed

References:

disa | CCI-002314
os-srg | SRG-OS-000297-GPOS-00115
stigid | UBTU-20-010433
cis | 3.5.1.1
stigref | SV-238354r853429_rule

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | enable

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    DEBIAN_FRONTEND=noninteractive apt-get install -y "ufw"

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation OSBuild Blueprint snippet ⇲

    [[packages]]
    name = "ufw"
    version = "*"

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | enable

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - DISA-STIG-UBTU-20-010433
      - enable_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - package_ufw_installed

    - name: Ensure ufw is installed
      package:
        name: ufw
        state: present
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - DISA-STIG-UBTU-20-010433
      - enable_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - package_ufw_installed

Remediation Puppet snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | enable

    include install_ufw

    class install_ufw {
      package { 'ufw':
        ensure => 'installed',
      }
    }

#### Rule Remove ufw Package [ref]

The `ufw` package can be removed with the following command:

    $ apt-get remove ufw

Rationale: | Running `iptables.persistent` with `ufw` enabled may lead to conflict and unexpected results.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_package_ufw_removed

References:

cis | 3.5.2.2

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    # CAUTION: This remediation script will remove ufw
    #	   from the system, and may remove any packages
    #	   that depend on ufw. Execute this
    #	   remediation AFTER testing on a non-production
    #	   system!

    DEBIAN_FRONTEND=noninteractive apt-get remove -y "ufw"

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - disable_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - package_ufw_removed

    - name: Ensure ufw is removed
      package:
        name: ufw
        state: absent
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - disable_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - package_ufw_removed

Remediation Puppet snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    include remove_ufw

    class remove_ufw {
      package { 'ufw':
        ensure => 'purged',
      }
    }

#### Rule Verify ufw Enabled [ref]

The `ufw` service can be enabled with the following command:

    $ sudo systemctl enable ufw.service

Rationale: | The ufw service must be enabled and running in order for ufw to protect the system
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_service_ufw_enabled

References:

disa | CCI-002314
os-srg | SRG-OS-000297-GPOS-00115
stigid | UBTU-20-010434
cis | 3.5.1.3
stigref | SV-238355r853430_rule

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | enable

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed && { ( dpkg-query --show --showformat='${db:Status-Status}\n' 'ufw' 2>/dev/null | grep -q '^installed' && dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed ); }; then

    SYSTEMCTL_EXEC='/usr/bin/systemctl'
    "$SYSTEMCTL_EXEC" unmask 'ufw.service'
    if [[ $("$SYSTEMCTL_EXEC" is-system-running) != "offline" ]]; then
      "$SYSTEMCTL_EXEC" start 'ufw.service'
    fi
    "$SYSTEMCTL_EXEC" enable 'ufw.service'

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation OSBuild Blueprint snippet ⇲

    [customizations.services]
    enabled = ["ufw"]

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | enable

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - DISA-STIG-UBTU-20-010434
      - enable_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - service_ufw_enabled

    - name: Verify ufw Enabled - Enable service ufw
      block:

      - name: Gather the package facts
        package_facts:
          manager: auto

      - name: Verify ufw Enabled - Enable Service ufw
        ansible.builtin.systemd:
          name: ufw
          enabled: true
          state: started
          masked: false
        when:
        - '"ufw" in ansible_facts.packages'
      when:
      - '"linux-base" in ansible_facts.packages'
      - ( "ufw" in ansible_facts.packages and "linux-base" in ansible_facts.packages )
      tags:
      - DISA-STIG-UBTU-20-010434
      - enable_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - service_ufw_enabled

Remediation Puppet snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | enable

    include enable_ufw

    class enable_ufw {
      service {'ufw':
        enable => true,
        ensure => 'running',
      }
    }

#### Rule Ensure ufw Default Deny Firewall Policy [ref]

A default deny policy on connections ensures that any unconfigured network usage will be rejected. Note: Any port or protocol without a explicit allow before the default deny will be blocked. Warning: Changing firewall settings while connected over network can result in being locked out of the system.
Rationale: | With a default accept policy the firewall will accept any packet that is not configured to be denied. It is easier to allow acceptable usage than to block unacceptable usage.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_set_ufw_default_rule

References:

cis | 3.5.1.7

#### Rule Set UFW Loopback Traffic [ref]

Configure the loopback interface to accept traffic. Configure all other interfaces to deny traffic to the loopback network. Warning: Changing firewall settings while connected over network can result in being locked out of the system.
Rationale: | Loopback traffic is generated between processes on machine and is typically critical to operation of the system. The loopback interface is the only place that loopback network traffic should be seen, all other interfaces should ignore traffic on this network as an anti-spoofing measure.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_set_ufw_loopback_traffic

References:

cis | 3.5.1.4

Remediation Shell script ⇲

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed && { dpkg-query --show --showformat='${db:Status-Status}\n' 'ufw' 2>/dev/null | grep -q '^installed'; }; then

    ufw allow in on lo
    ufw allow out on lo
    ufw deny in from 127.0.0.0/8
    ufw deny in from ::1

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Group Wireless Networking Group contains 1 group and 1 rule

[ref] Wireless networking, such as 802.11 (WiFi) and Bluetooth, can present a security risk to sensitive or classified systems and networks. Wireless networking hardware is much more likely to be included in laptop or portable systems than in desktops or servers.
Removal of hardware provides the greatest assurance that the wireless capability remains disabled. Acquisition policies often include provisions to prevent the purchase of equipment that will be used in sensitive spaces and includes wireless capabilities. If it is impractical to remove the wireless hardware, and policy permits the device to enter sensitive spaces as long as wireless is disabled, efforts should instead focus on disabling wireless capability via software.

Group Disable Wireless Through Software Configuration Group contains 1 rule
[ref] If it is impossible to remove the wireless hardware from the device in question, disable as much of it as possible through software. The following methods can disable software support for wireless networking, but note that these methods do not prevent malicious software or careless users from re-activating the devices.

#### Rule Deactivate Wireless Network Interfaces [ref]

Deactivating wireless network interfaces should prevent normal usage of the wireless capability.
Verify that there are no wireless interfaces configured on the system with the following command:

    $ ls -L -d /sys/class/net/*/wireless | xargs dirname | xargs basename -a

Rationale:

The use of wireless networking can introduce many different attack vectors into the organization's network. Common attack vectors such as malicious association and ad hoc networks will allow an attacker to spoof a wireless access point (AP), allowing validated systems to connect to the malicious AP and enabling the attacker to monitor and record network traffic. These malicious APs can also serve to create a man-in-the-middle attack or be used to create a denial of service to valid network resources.

Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_wireless_disable_interfaces

References:

cis-csc | 11, 12, 14, 15, 3, 8, 9
cobit5 | APO13.01, BAI10.01, BAI10.02, BAI10.03, BAI10.05, DSS01.04, DSS05.02, DSS05.03, DSS05.05, DSS06.06
cui | 3.1.16
disa | CCI-001443, CCI-001444, CCI-002421, CCI-002418
isa-62443-2009 | 4.3.3.5.1, 4.3.3.5.2, 4.3.3.5.3, 4.3.3.5.4, 4.3.3.5.5, 4.3.3.5.6, 4.3.3.5.7, 4.3.3.5.8, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.1, 4.3.3.7.2, 4.3.3.7.3, 4.3.3.7.4, 4.3.4.3.2, 4.3.4.3.3
isa-62443-2013 | SR 1.1, SR 1.10, SR 1.11, SR 1.12, SR 1.13, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.6, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 2.2, SR 2.3, SR 2.4, SR 2.5, SR 2.6, SR 2.7, SR 3.1, SR 3.5, SR 3.8, SR 4.1, SR 4.3, SR 5.1, SR 5.2, SR 5.3, SR 7.1, SR 7.6
ism | 1315, 1319
iso27001-2013 | A.11.2.6, A.12.1.2, A.12.5.1, A.12.6.2, A.13.1.1, A.13.2.1, A.14.1.3, A.14.2.2, A.14.2.3, A.14.2.4, A.6.2.1, A.6.2.2, A.9.1.2
nist | AC-18(a), AC-18(3), CM-7(a), CM-7(b), CM-6(a), MP-7
nist-csf | PR.AC-3, PR.IP-1, PR.PT-3, PR.PT-4
pcidss | Req-1.3.3
os-srg | SRG-OS-000299-GPOS-00117, SRG-OS-000300-GPOS-00118, SRG-OS-000424-GPOS-00188, SRG-OS-000481-GPOS-000481
stigid | UBTU-20-010455
cis | 3.1.2
pcidss4 | 1.3.3, 1.3
stigref | SV-252704r942848_rule

Remediation Shell script ⇲

    if [ -n "$(find /sys/class/net/*/ -type d -name wireless)" ]; then
        interfaces=$(find /sys/class/net/*/wireless -type d -name wireless | xargs -0 dirname | xargs basename)

        for i in $interfaces; do
            ip link set dev "$i" down
            drivers=$(basename "$(readlink -f /sys/class/net/"$i"/device/driver)")
            echo "install $drivers /bin/false" >> /etc/modprobe.d/disable_wireless.conf
            modprobe -r "$drivers"
         done
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | medium
Reboot: | false
Strategy: | unknown

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - DISA-STIG-UBTU-20-010455
      - NIST-800-171-3.1.16
      - NIST-800-53-AC-18(3)
      - NIST-800-53-AC-18(a)
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-MP-7
      - PCI-DSS-Req-1.3.3
      - PCI-DSSv4-1.3
      - PCI-DSSv4-1.3.3
      - low_complexity
      - medium_disruption
      - medium_severity
      - no_reboot_needed
      - unknown_strategy
      - wireless_disable_interfaces

    - name: Service facts
      ansible.builtin.service_facts: null
      tags:
      - DISA-STIG-UBTU-20-010455
      - NIST-800-171-3.1.16
      - NIST-800-53-AC-18(3)
      - NIST-800-53-AC-18(a)
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-MP-7
      - PCI-DSS-Req-1.3.3
      - PCI-DSSv4-1.3
      - PCI-DSSv4-1.3.3
      - low_complexity
      - medium_disruption
      - medium_severity
      - no_reboot_needed
      - unknown_strategy
      - wireless_disable_interfaces

    - name: Ensure NetworkManager is installed
      ansible.builtin.package:
        name: '{{ item }}'
        state: present
      with_items:
      - NetworkManager
      tags:
      - DISA-STIG-UBTU-20-010455
      - NIST-800-171-3.1.16
      - NIST-800-53-AC-18(3)
      - NIST-800-53-AC-18(a)
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-MP-7
      - PCI-DSS-Req-1.3.3
      - PCI-DSSv4-1.3
      - PCI-DSSv4-1.3.3
      - low_complexity
      - medium_disruption
      - medium_severity
      - no_reboot_needed
      - unknown_strategy
      - wireless_disable_interfaces

    - name: NetworkManager Deactivate Wireless Network Interfaces
      command: nmcli radio wifi off
      when:
      - '''NetworkManager'' in ansible_facts.packages'
      - ansible_facts.services['NetworkManager.service'].state == 'running'
      tags:
      - DISA-STIG-UBTU-20-010455
      - NIST-800-171-3.1.16
      - NIST-800-53-AC-18(3)
      - NIST-800-53-AC-18(a)
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-MP-7
      - PCI-DSS-Req-1.3.3
      - PCI-DSSv4-1.3
      - PCI-DSSv4-1.3.3
      - low_complexity
      - medium_disruption
      - medium_severity
      - no_reboot_needed
      - unknown_strategy
      - wireless_disable_interfaces

Group File Permissions and Masks Group contains 7 groups and 50 rules

[ref] Traditional Unix security relies heavily on file and directory permissions to prevent unauthorized users from reading or modifying files to which they should not have access.
Several of the commands in this section search filesystems for files or directories with certain characteristics, and are intended to be run on every local partition on a given system. When the variable PART appears in one of the commands below, it means that the command is intended to be run repeatedly, with the name of each local partition substituted for PART in turn.
The following command prints a list of all xfs partitions on the local system, which is the default filesystem for Ubuntu 20.04 installations:

    $ mount -t xfs | awk '{print $3}'

For any systems that use a different local filesystem type, modify this command as appropriate.

Group Verify Permissions on Important Files and Directories Group contains 1 group and 29 rules
[ref] Permissions for many files on a system must be set restrictively to ensure sensitive information is properly protected. This section discusses important permission restrictions which can be verified to ensure that no harmful discrepancies have arisen.
Group Verify Permissions on Files with Local Account Information and Credentials Group contains 24 rules
[ref] The default restrictive permissions for files which act as important security databases such as `passwd`, `shadow`, `group`, and `gshadow` files must be maintained. Many utilities need read access to the `passwd` file in order to function properly, but read access to the `shadow` file allows malicious attacks against system passwords, and should never be enabled.

#### Rule Verify Group Who Owns Backup group File [ref]

To properly set the group owner of `/etc/group-`, run the command:

    $ sudo chgrp root /etc/group-

Rationale: | The `/etc/group-` file is a backup file of `/etc/group`, and as such, it contains information regarding groups that are configured on the system. Protection of this file is important for system security.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_file_groupowner_backup_etc_group

References:

disa | CCI-000366
nist | AC-6 (1)
pcidss | Req-8.7
os-srg | SRG-OS-000480-GPOS-00227
cis | 6.1.8
pcidss4 | 2.2.6, 2.2

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    chgrp 0 /etc/group-

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    - name: Test for existence /etc/group-
      stat:
        path: /etc/group-
      register: file_exists
      tags:
      - NIST-800-53-AC-6 (1)
      - PCI-DSS-Req-8.7
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_groupowner_backup_etc_group
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Ensure group owner 0 on /etc/group-
      file:
        path: /etc/group-
        group: '0'
      when: file_exists.stat is defined and file_exists.stat.exists
      tags:
      - NIST-800-53-AC-6 (1)
      - PCI-DSS-Req-8.7
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_groupowner_backup_etc_group
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

#### Rule Verify Group Who Owns Backup gshadow File [ref]

To properly set the group owner of `/etc/gshadow-`, run the command:

    $ sudo chgrp shadow /etc/gshadow-

Rationale: | The `/etc/gshadow-` file is a backup of `/etc/gshadow`, and as such, it contains group password hashes. Protection of this file is critical for system security.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_file_groupowner_backup_etc_gshadow

References:

disa | CCI-000366
nist | AC-6 (1)
pcidss | Req-8.7
os-srg | SRG-OS-000480-GPOS-00227
cis | 6.1.3

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    chgrp 42 /etc/gshadow-

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    - name: Test for existence /etc/gshadow-
      stat:
        path: /etc/gshadow-
      register: file_exists
      tags:
      - NIST-800-53-AC-6 (1)
      - PCI-DSS-Req-8.7
      - configure_strategy
      - file_groupowner_backup_etc_gshadow
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Ensure group owner 42 on /etc/gshadow-
      file:
        path: /etc/gshadow-
        group: '42'
      when: file_exists.stat is defined and file_exists.stat.exists
      tags:
      - NIST-800-53-AC-6 (1)
      - PCI-DSS-Req-8.7
      - configure_strategy
      - file_groupowner_backup_etc_gshadow
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

#### Rule Verify Group Who Owns Backup passwd File [ref]

To properly set the group owner of `/etc/passwd-`, run the command:

    $ sudo chgrp root /etc/passwd-

Rationale: | The `/etc/passwd-` file is a backup file of `/etc/passwd`, and as such, it contains information about the users that are configured on the system. Protection of this file is critical for system security.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_file_groupowner_backup_etc_passwd

References:

disa | CCI-000366
nist | AC-6 (1)
pcidss | Req-8.7
os-srg | SRG-OS-000480-GPOS-00227
cis | 6.1.6
pcidss4 | 2.2.6, 2.2

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    chgrp 0 /etc/passwd-

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    - name: Test for existence /etc/passwd-
      stat:
        path: /etc/passwd-
      register: file_exists
      tags:
      - NIST-800-53-AC-6 (1)
      - PCI-DSS-Req-8.7
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_groupowner_backup_etc_passwd
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Ensure group owner 0 on /etc/passwd-
      file:
        path: /etc/passwd-
        group: '0'
      when: file_exists.stat is defined and file_exists.stat.exists
      tags:
      - NIST-800-53-AC-6 (1)
      - PCI-DSS-Req-8.7
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_groupowner_backup_etc_passwd
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

#### Rule Verify User Who Owns Backup shadow File [ref]

To properly set the group owner of `/etc/shadow-`, run the command:

    $ sudo chgrp shadow /etc/shadow-

Rationale: | The `/etc/shadow-` file is a backup file of `/etc/shadow`, and as such, it contains the list of local system accounts and password hashes. Protection of this file is critical for system security.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_file_groupowner_backup_etc_shadow

References:

disa | CCI-000366
pcidss | Req-8.7
os-srg | SRG-OS-000480-GPOS-00227
cis | 6.1.7
pcidss4 | 2.2.6, 2.2

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    chgrp 42 /etc/shadow-

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    - name: Test for existence /etc/shadow-
      stat:
        path: /etc/shadow-
      register: file_exists
      tags:
      - PCI-DSS-Req-8.7
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_groupowner_backup_etc_shadow
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Ensure group owner 42 on /etc/shadow-
      file:
        path: /etc/shadow-
        group: '42'
      when: file_exists.stat is defined and file_exists.stat.exists
      tags:
      - PCI-DSS-Req-8.7
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_groupowner_backup_etc_shadow
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

#### Rule Verify Group Who Owns group File [ref]

To properly set the group owner of `/etc/group`, run the command:

    $ sudo chgrp root /etc/group

Rationale: | The `/etc/group` file contains information regarding groups that are configured on the system. Protection of this file is important for system security.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_file_groupowner_etc_group

References:

cis-csc | 12, 13, 14, 15, 16, 18, 3, 5
cjis | 5.5.2.2
cobit5 | APO01.06, DSS05.04, DSS05.07, DSS06.02
disa | CCI-000366
isa-62443-2009 | 4.3.3.7.3
isa-62443-2013 | SR 2.1, SR 5.2
iso27001-2013 | A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.13.1.1, A.13.1.3, A.13.2.1, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, A.6.1.2, A.7.1.1, A.7.1.2, A.7.3.1, A.8.2.2, A.8.2.3, A.9.1.1, A.9.1.2, A.9.2.3, A.9.4.1, A.9.4.4, A.9.4.5
nerc-cip | CIP-003-8 R5.1.1, CIP-003-8 R5.3, CIP-004-6 R2.3, CIP-007-3 R2.1, CIP-007-3 R2.2, CIP-007-3 R2.3, CIP-007-3 R5.1, CIP-007-3 R5.1.1, CIP-007-3 R5.1.2
nist | CM-6(a), AC-6(1)
nist-csf | PR.AC-4, PR.DS-5
pcidss | Req-8.7.c
os-srg | SRG-OS-000480-GPOS-00227
cis | 6.1.5
anssi | R50
pcidss4 | 2.2.6, 2.2

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    chgrp 0 /etc/group

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    - name: Test for existence /etc/group
      stat:
        path: /etc/group
      register: file_exists
      tags:
      - CJIS-5.5.2.2
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - PCI-DSS-Req-8.7.c
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_groupowner_etc_group
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Ensure group owner 0 on /etc/group
      file:
        path: /etc/group
        group: '0'
      when: file_exists.stat is defined and file_exists.stat.exists
      tags:
      - CJIS-5.5.2.2
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - PCI-DSS-Req-8.7.c
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_groupowner_etc_group
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

#### Rule Verify Group Who Owns gshadow File [ref]

To properly set the group owner of `/etc/gshadow`, run the command:

    $ sudo chgrp shadow /etc/gshadow

Rationale: | The `/etc/gshadow` file contains group password hashes. Protection of this file is critical for system security.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_file_groupowner_etc_gshadow

References:

cis-csc | 12, 13, 14, 15, 16, 18, 3, 5
cobit5 | APO01.06, DSS05.04, DSS05.07, DSS06.02
disa | CCI-000366
isa-62443-2009 | 4.3.3.7.3
isa-62443-2013 | SR 2.1, SR 5.2
iso27001-2013 | A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.13.1.1, A.13.1.3, A.13.2.1, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, A.6.1.2, A.7.1.1, A.7.1.2, A.7.3.1, A.8.2.2, A.8.2.3, A.9.1.1, A.9.1.2, A.9.2.3, A.9.4.1, A.9.4.4, A.9.4.5
nerc-cip | CIP-003-8 R5.1.1, CIP-003-8 R5.3, CIP-004-6 R2.3, CIP-007-3 R2.1, CIP-007-3 R2.2, CIP-007-3 R2.3, CIP-007-3 R5.1, CIP-007-3 R5.1.1, CIP-007-3 R5.1.2
nist | CM-6(a), AC-6(1)
nist-csf | PR.AC-4, PR.DS-5
os-srg | SRG-OS-000480-GPOS-00227
cis | 6.1.9
anssi | R50

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    chgrp 42 /etc/gshadow

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    - name: Test for existence /etc/gshadow
      stat:
        path: /etc/gshadow
      register: file_exists
      tags:
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - configure_strategy
      - file_groupowner_etc_gshadow
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Ensure group owner 42 on /etc/gshadow
      file:
        path: /etc/gshadow
        group: '42'
      when: file_exists.stat is defined and file_exists.stat.exists
      tags:
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - configure_strategy
      - file_groupowner_etc_gshadow
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

#### Rule Verify Group Who Owns passwd File [ref]

To properly set the group owner of `/etc/passwd`, run the command:

    $ sudo chgrp root /etc/passwd

Rationale: | The `/etc/passwd` file contains information about the users that are configured on the system. Protection of this file is critical for system security.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_file_groupowner_etc_passwd

References:

cis-csc | 12, 13, 14, 15, 16, 18, 3, 5
cjis | 5.5.2.2
cobit5 | APO01.06, DSS05.04, DSS05.07, DSS06.02
disa | CCI-000366
isa-62443-2009 | 4.3.3.7.3
isa-62443-2013 | SR 2.1, SR 5.2
iso27001-2013 | A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.13.1.1, A.13.1.3, A.13.2.1, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, A.6.1.2, A.7.1.1, A.7.1.2, A.7.3.1, A.8.2.2, A.8.2.3, A.9.1.1, A.9.1.2, A.9.2.3, A.9.4.1, A.9.4.4, A.9.4.5
nerc-cip | CIP-003-8 R5.1.1, CIP-003-8 R5.3, CIP-004-6 R2.3, CIP-007-3 R2.1, CIP-007-3 R2.2, CIP-007-3 R2.3, CIP-007-3 R5.1, CIP-007-3 R5.1.1, CIP-007-3 R5.1.2
nist | CM-6(a), AC-6(1)
nist-csf | PR.AC-4, PR.DS-5
pcidss | Req-8.7.c
os-srg | SRG-OS-000480-GPOS-00227
cis | 6.1.2
anssi | R50
pcidss4 | 2.2.6, 2.2

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    chgrp 0 /etc/passwd

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    - name: Test for existence /etc/passwd
      stat:
        path: /etc/passwd
      register: file_exists
      tags:
      - CJIS-5.5.2.2
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - PCI-DSS-Req-8.7.c
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_groupowner_etc_passwd
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Ensure group owner 0 on /etc/passwd
      file:
        path: /etc/passwd
        group: '0'
      when: file_exists.stat is defined and file_exists.stat.exists
      tags:
      - CJIS-5.5.2.2
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - PCI-DSS-Req-8.7.c
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_groupowner_etc_passwd
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

#### Rule Verify Group Who Owns shadow File [ref]

To properly set the group owner of `/etc/shadow`, run the command:

    $ sudo chgrp shadow /etc/shadow

Rationale: | The `/etc/shadow` file stores password hashes. Protection of this file is critical for system security.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_file_groupowner_etc_shadow

References:

cis-csc | 12, 13, 14, 15, 16, 18, 3, 5
cjis | 5.5.2.2
cobit5 | APO01.06, DSS05.04, DSS05.07, DSS06.02
disa | CCI-000366
isa-62443-2009 | 4.3.3.7.3
isa-62443-2013 | SR 2.1, SR 5.2
iso27001-2013 | A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.13.1.1, A.13.1.3, A.13.2.1, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, A.6.1.2, A.7.1.1, A.7.1.2, A.7.3.1, A.8.2.2, A.8.2.3, A.9.1.1, A.9.1.2, A.9.2.3, A.9.4.1, A.9.4.4, A.9.4.5
nerc-cip | CIP-003-8 R5.1.1, CIP-003-8 R5.3, CIP-004-6 R2.3, CIP-007-3 R2.1, CIP-007-3 R2.2, CIP-007-3 R2.3, CIP-007-3 R5.1, CIP-007-3 R5.1.1, CIP-007-3 R5.1.2
nist | CM-6(a), AC-6(1)
nist-csf | PR.AC-4, PR.DS-5
pcidss | Req-8.7.c
os-srg | SRG-OS-000480-GPOS-00227
cis | 6.1.4
anssi | R50
pcidss4 | 2.2.6, 2.2

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    chgrp 42 /etc/shadow

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    - name: Test for existence /etc/shadow
      stat:
        path: /etc/shadow
      register: file_exists
      tags:
      - CJIS-5.5.2.2
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - PCI-DSS-Req-8.7.c
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_groupowner_etc_shadow
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Ensure group owner 42 on /etc/shadow
      file:
        path: /etc/shadow
        group: '42'
      when: file_exists.stat is defined and file_exists.stat.exists
      tags:
      - CJIS-5.5.2.2
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - PCI-DSS-Req-8.7.c
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_groupowner_etc_shadow
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

#### Rule Verify User Who Owns Backup group File [ref]

To properly set the owner of `/etc/group-`, run the command:

    $ sudo chown root /etc/group-

Rationale: | The `/etc/group-` file is a backup file of `/etc/group`, and as such, it contains information regarding groups that are configured on the system. Protection of this file is important for system security.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_file_owner_backup_etc_group

References:

disa | CCI-000366
nist | AC-6 (1)
pcidss | Req-8.7.c
os-srg | SRG-OS-000480-GPOS-00227
cis | 6.1.8
pcidss4 | 2.2.6, 2.2

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    chown 0 /etc/group-

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    - name: Test for existence /etc/group-
      stat:
        path: /etc/group-
      register: file_exists
      tags:
      - NIST-800-53-AC-6 (1)
      - PCI-DSS-Req-8.7.c
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_owner_backup_etc_group
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Ensure owner 0 on /etc/group-
      file:
        path: /etc/group-
        owner: '0'
      when: file_exists.stat is defined and file_exists.stat.exists
      tags:
      - NIST-800-53-AC-6 (1)
      - PCI-DSS-Req-8.7.c
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_owner_backup_etc_group
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

#### Rule Verify User Who Owns Backup gshadow File [ref]

To properly set the owner of `/etc/gshadow-`, run the command:

    $ sudo chown root /etc/gshadow-

Rationale: | The `/etc/gshadow-` file is a backup of `/etc/gshadow`, and as such, it contains group password hashes. Protection of this file is critical for system security.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_file_owner_backup_etc_gshadow

References:

disa | CCI-000366
nist | AC-6 (1)
pcidss | Req-8.7
os-srg | SRG-OS-000480-GPOS-00227
cis | 6.1.3

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    chown 0 /etc/gshadow-

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    - name: Test for existence /etc/gshadow-
      stat:
        path: /etc/gshadow-
      register: file_exists
      tags:
      - NIST-800-53-AC-6 (1)
      - PCI-DSS-Req-8.7
      - configure_strategy
      - file_owner_backup_etc_gshadow
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Ensure owner 0 on /etc/gshadow-
      file:
        path: /etc/gshadow-
        owner: '0'
      when: file_exists.stat is defined and file_exists.stat.exists
      tags:
      - NIST-800-53-AC-6 (1)
      - PCI-DSS-Req-8.7
      - configure_strategy
      - file_owner_backup_etc_gshadow
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

#### Rule Verify User Who Owns Backup passwd File [ref]

To properly set the owner of `/etc/passwd-`, run the command:

    $ sudo chown root /etc/passwd-

Rationale: | The `/etc/passwd-` file is a backup file of `/etc/passwd`, and as such, it contains information about the users that are configured on the system. Protection of this file is critical for system security.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_file_owner_backup_etc_passwd

References:

disa | CCI-000366
nist | AC-6 (1)
pcidss | Req-8.7.c
os-srg | SRG-OS-000480-GPOS-00227
cis | 6.1.6
pcidss4 | 2.2.6, 2.2

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    chown 0 /etc/passwd-

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    - name: Test for existence /etc/passwd-
      stat:
        path: /etc/passwd-
      register: file_exists
      tags:
      - NIST-800-53-AC-6 (1)
      - PCI-DSS-Req-8.7.c
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_owner_backup_etc_passwd
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Ensure owner 0 on /etc/passwd-
      file:
        path: /etc/passwd-
        owner: '0'
      when: file_exists.stat is defined and file_exists.stat.exists
      tags:
      - NIST-800-53-AC-6 (1)
      - PCI-DSS-Req-8.7.c
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_owner_backup_etc_passwd
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

#### Rule Verify Group Who Owns Backup shadow File [ref]

To properly set the owner of `/etc/shadow-`, run the command:

    $ sudo chown root /etc/shadow-

Rationale: | The `/etc/shadow-` file is a backup file of `/etc/shadow`, and as such, it contains the list of local system accounts and password hashes. Protection of this file is critical for system security.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_file_owner_backup_etc_shadow

References:

disa | CCI-000366
nist | AC-6 (1)
pcidss | Req-8.7.c
os-srg | SRG-OS-000480-GPOS-00227
cis | 6.1.7
pcidss4 | 2.2.6, 2.2

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    chown 0 /etc/shadow-

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    - name: Test for existence /etc/shadow-
      stat:
        path: /etc/shadow-
      register: file_exists
      tags:
      - NIST-800-53-AC-6 (1)
      - PCI-DSS-Req-8.7.c
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_owner_backup_etc_shadow
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Ensure owner 0 on /etc/shadow-
      file:
        path: /etc/shadow-
        owner: '0'
      when: file_exists.stat is defined and file_exists.stat.exists
      tags:
      - NIST-800-53-AC-6 (1)
      - PCI-DSS-Req-8.7.c
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_owner_backup_etc_shadow
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

#### Rule Verify User Who Owns group File [ref]

To properly set the owner of `/etc/group`, run the command:

    $ sudo chown root /etc/group

Rationale: | The `/etc/group` file contains information regarding groups that are configured on the system. Protection of this file is important for system security.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_file_owner_etc_group

References:

cis-csc | 12, 13, 14, 15, 16, 18, 3, 5
cjis | 5.5.2.2
cobit5 | APO01.06, DSS05.04, DSS05.07, DSS06.02
disa | CCI-000366
isa-62443-2009 | 4.3.3.7.3
isa-62443-2013 | SR 2.1, SR 5.2
iso27001-2013 | A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.13.1.1, A.13.1.3, A.13.2.1, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, A.6.1.2, A.7.1.1, A.7.1.2, A.7.3.1, A.8.2.2, A.8.2.3, A.9.1.1, A.9.1.2, A.9.2.3, A.9.4.1, A.9.4.4, A.9.4.5
nerc-cip | CIP-003-8 R5.1.1, CIP-003-8 R5.3, CIP-004-6 R2.3, CIP-007-3 R2.1, CIP-007-3 R2.2, CIP-007-3 R2.3, CIP-007-3 R5.1, CIP-007-3 R5.1.1, CIP-007-3 R5.1.2
nist | CM-6(a), AC-6(1)
nist-csf | PR.AC-4, PR.DS-5
pcidss | Req-8.7.c
os-srg | SRG-OS-000480-GPOS-00227
cis | 6.1.5
anssi | R50
pcidss4 | 2.2.6, 2.2

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    chown 0 /etc/group

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    - name: Test for existence /etc/group
      stat:
        path: /etc/group
      register: file_exists
      tags:
      - CJIS-5.5.2.2
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - PCI-DSS-Req-8.7.c
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_owner_etc_group
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Ensure owner 0 on /etc/group
      file:
        path: /etc/group
        owner: '0'
      when: file_exists.stat is defined and file_exists.stat.exists
      tags:
      - CJIS-5.5.2.2
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - PCI-DSS-Req-8.7.c
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_owner_etc_group
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

#### Rule Verify User Who Owns gshadow File [ref]

To properly set the owner of `/etc/gshadow`, run the command:

    $ sudo chown root /etc/gshadow

Rationale: | The `/etc/gshadow` file contains group password hashes. Protection of this file is critical for system security.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_file_owner_etc_gshadow

References:

cis-csc | 12, 13, 14, 15, 16, 18, 3, 5
cobit5 | APO01.06, DSS05.04, DSS05.07, DSS06.02
disa | CCI-000366
isa-62443-2009 | 4.3.3.7.3
isa-62443-2013 | SR 2.1, SR 5.2
iso27001-2013 | A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.13.1.1, A.13.1.3, A.13.2.1, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, A.6.1.2, A.7.1.1, A.7.1.2, A.7.3.1, A.8.2.2, A.8.2.3, A.9.1.1, A.9.1.2, A.9.2.3, A.9.4.1, A.9.4.4, A.9.4.5
nerc-cip | CIP-003-8 R5.1.1, CIP-003-8 R5.3, CIP-004-6 R2.3, CIP-007-3 R2.1, CIP-007-3 R2.2, CIP-007-3 R2.3, CIP-007-3 R5.1, CIP-007-3 R5.1.1, CIP-007-3 R5.1.2
nist | CM-6(a), AC-6(1)
nist-csf | PR.AC-4, PR.DS-5
os-srg | SRG-OS-000480-GPOS-00227
cis | 6.1.9
anssi | R50

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    chown 0 /etc/gshadow

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    - name: Test for existence /etc/gshadow
      stat:
        path: /etc/gshadow
      register: file_exists
      tags:
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - configure_strategy
      - file_owner_etc_gshadow
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Ensure owner 0 on /etc/gshadow
      file:
        path: /etc/gshadow
        owner: '0'
      when: file_exists.stat is defined and file_exists.stat.exists
      tags:
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - configure_strategy
      - file_owner_etc_gshadow
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

#### Rule Verify User Who Owns passwd File [ref]

To properly set the owner of `/etc/passwd`, run the command:

    $ sudo chown root /etc/passwd

Rationale: | The `/etc/passwd` file contains information about the users that are configured on the system. Protection of this file is critical for system security.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_file_owner_etc_passwd

References:

cis-csc | 12, 13, 14, 15, 16, 18, 3, 5
cjis | 5.5.2.2
cobit5 | APO01.06, DSS05.04, DSS05.07, DSS06.02
disa | CCI-000366
isa-62443-2009 | 4.3.3.7.3
isa-62443-2013 | SR 2.1, SR 5.2
iso27001-2013 | A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.13.1.1, A.13.1.3, A.13.2.1, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, A.6.1.2, A.7.1.1, A.7.1.2, A.7.3.1, A.8.2.2, A.8.2.3, A.9.1.1, A.9.1.2, A.9.2.3, A.9.4.1, A.9.4.4, A.9.4.5
nerc-cip | CIP-003-8 R5.1.1, CIP-003-8 R5.3, CIP-004-6 R2.3, CIP-007-3 R2.1, CIP-007-3 R2.2, CIP-007-3 R2.3, CIP-007-3 R5.1, CIP-007-3 R5.1.1, CIP-007-3 R5.1.2
nist | CM-6(a), AC-6(1)
nist-csf | PR.AC-4, PR.DS-5
pcidss | Req-8.7.c
os-srg | SRG-OS-000480-GPOS-00227
cis | 6.1.2
anssi | R50
pcidss4 | 2.2.6, 2.2

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    chown 0 /etc/passwd

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    - name: Test for existence /etc/passwd
      stat:
        path: /etc/passwd
      register: file_exists
      tags:
      - CJIS-5.5.2.2
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - PCI-DSS-Req-8.7.c
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_owner_etc_passwd
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Ensure owner 0 on /etc/passwd
      file:
        path: /etc/passwd
        owner: '0'
      when: file_exists.stat is defined and file_exists.stat.exists
      tags:
      - CJIS-5.5.2.2
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - PCI-DSS-Req-8.7.c
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_owner_etc_passwd
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

#### Rule Verify User Who Owns shadow File [ref]

To properly set the owner of `/etc/shadow`, run the command:

    $ sudo chown root /etc/shadow

Rationale: | The `/etc/shadow` file contains the list of local system accounts and stores password hashes. Protection of this file is critical for system security. Failure to give ownership of this file to root provides the designated owner with access to sensitive information which could weaken the system security posture.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_file_owner_etc_shadow

References:

cis-csc | 12, 13, 14, 15, 16, 18, 3, 5
cjis | 5.5.2.2
cobit5 | APO01.06, DSS05.04, DSS05.07, DSS06.02
disa | CCI-000366
isa-62443-2009 | 4.3.3.7.3
isa-62443-2013 | SR 2.1, SR 5.2
iso27001-2013 | A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.13.1.1, A.13.1.3, A.13.2.1, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, A.6.1.2, A.7.1.1, A.7.1.2, A.7.3.1, A.8.2.2, A.8.2.3, A.9.1.1, A.9.1.2, A.9.2.3, A.9.4.1, A.9.4.4, A.9.4.5
nerc-cip | CIP-003-8 R5.1.1, CIP-003-8 R5.3, CIP-004-6 R2.3, CIP-007-3 R2.1, CIP-007-3 R2.2, CIP-007-3 R2.3, CIP-007-3 R5.1, CIP-007-3 R5.1.1, CIP-007-3 R5.1.2
nist | CM-6(a), AC-6(1)
nist-csf | PR.AC-4, PR.DS-5
pcidss | Req-8.7.c
os-srg | SRG-OS-000480-GPOS-00227
cis | 6.1.4
anssi | R50
pcidss4 | 2.2.6, 2.2

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    chown 0 /etc/shadow

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    - name: Test for existence /etc/shadow
      stat:
        path: /etc/shadow
      register: file_exists
      tags:
      - CJIS-5.5.2.2
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - PCI-DSS-Req-8.7.c
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_owner_etc_shadow
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Ensure owner 0 on /etc/shadow
      file:
        path: /etc/shadow
        owner: '0'
      when: file_exists.stat is defined and file_exists.stat.exists
      tags:
      - CJIS-5.5.2.2
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - PCI-DSS-Req-8.7.c
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_owner_etc_shadow
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

#### Rule Verify Permissions on Backup group File [ref]

To properly set the permissions of `/etc/group-`, run the command:

    $ sudo chmod 0644 /etc/group-

Rationale: | The `/etc/group-` file is a backup file of `/etc/group`, and as such, it contains information regarding groups that are configured on the system. Protection of this file is important for system security.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_file_permissions_backup_etc_group

References:

disa | CCI-000366
nist | AC-6 (1)
pcidss | Req-8.7.c
os-srg | SRG-OS-000480-GPOS-00227
cis | 6.1.8
pcidss4 | 2.2.6, 2.2

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    chmod u-xs,g-xws,o-xwt /etc/group-

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    - name: Test for existence /etc/group-
      stat:
        path: /etc/group-
      register: file_exists
      tags:
      - NIST-800-53-AC-6 (1)
      - PCI-DSS-Req-8.7.c
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_permissions_backup_etc_group
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Ensure permission u-xs,g-xws,o-xwt on /etc/group-
      file:
        path: /etc/group-
        mode: u-xs,g-xws,o-xwt
      when: file_exists.stat is defined and file_exists.stat.exists
      tags:
      - NIST-800-53-AC-6 (1)
      - PCI-DSS-Req-8.7.c
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_permissions_backup_etc_group
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

#### Rule Verify Permissions on Backup gshadow File [ref]

To properly set the permissions of `/etc/gshadow-`, run the command:

    $ sudo chmod 0640 /etc/gshadow-

Rationale: | The `/etc/gshadow-` file is a backup of `/etc/gshadow`, and as such, it contains group password hashes. Protection of this file is critical for system security.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_file_permissions_backup_etc_gshadow

References:

disa | CCI-000366
nist | AC-6 (1)
os-srg | SRG-OS-000480-GPOS-00227
cis | 6.1.3

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    chmod u-xs,g-xws,o-xwrt /etc/gshadow-

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    - name: Test for existence /etc/gshadow-
      stat:
        path: /etc/gshadow-
      register: file_exists
      tags:
      - NIST-800-53-AC-6 (1)
      - configure_strategy
      - file_permissions_backup_etc_gshadow
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Ensure permission u-xs,g-xws,o-xwrt on /etc/gshadow-
      file:
        path: /etc/gshadow-
        mode: u-xs,g-xws,o-xwrt
      when: file_exists.stat is defined and file_exists.stat.exists
      tags:
      - NIST-800-53-AC-6 (1)
      - configure_strategy
      - file_permissions_backup_etc_gshadow
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

#### Rule Verify Permissions on Backup passwd File [ref]

To properly set the permissions of `/etc/passwd-`, run the command:

    $ sudo chmod 0644 /etc/passwd-

Rationale: | The `/etc/passwd-` file is a backup file of `/etc/passwd`, and as such, it contains information about the users that are configured on the system. Protection of this file is critical for system security.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_file_permissions_backup_etc_passwd

References:

disa | CCI-000366
nist | AC-6 (1)
pcidss | Req-8.7.c
os-srg | SRG-OS-000480-GPOS-00227
cis | 6.1.6
pcidss4 | 2.2.6, 2.2

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    chmod u-xs,g-xws,o-xwt /etc/passwd-

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    - name: Test for existence /etc/passwd-
      stat:
        path: /etc/passwd-
      register: file_exists
      tags:
      - NIST-800-53-AC-6 (1)
      - PCI-DSS-Req-8.7.c
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_permissions_backup_etc_passwd
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Ensure permission u-xs,g-xws,o-xwt on /etc/passwd-
      file:
        path: /etc/passwd-
        mode: u-xs,g-xws,o-xwt
      when: file_exists.stat is defined and file_exists.stat.exists
      tags:
      - NIST-800-53-AC-6 (1)
      - PCI-DSS-Req-8.7.c
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_permissions_backup_etc_passwd
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

#### Rule Verify Permissions on Backup shadow File [ref]

To properly set the permissions of `/etc/shadow-`, run the command:

    $ sudo chmod 0640 /etc/shadow-

Rationale: | The `/etc/shadow-` file is a backup file of `/etc/shadow`, and as such, it contains the list of local system accounts and password hashes. Protection of this file is critical for system security.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_file_permissions_backup_etc_shadow

References:

disa | CCI-000366
nist | AC-6 (1)
pcidss | Req-8.7.c
os-srg | SRG-OS-000480-GPOS-00227
cis | 6.1.7
pcidss4 | 2.2.6, 2.2

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    chmod u-xs,g-xws,o-xwrt /etc/shadow-

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    - name: Test for existence /etc/shadow-
      stat:
        path: /etc/shadow-
      register: file_exists
      tags:
      - NIST-800-53-AC-6 (1)
      - PCI-DSS-Req-8.7.c
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_permissions_backup_etc_shadow
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Ensure permission u-xs,g-xws,o-xwrt on /etc/shadow-
      file:
        path: /etc/shadow-
        mode: u-xs,g-xws,o-xwrt
      when: file_exists.stat is defined and file_exists.stat.exists
      tags:
      - NIST-800-53-AC-6 (1)
      - PCI-DSS-Req-8.7.c
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_permissions_backup_etc_shadow
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

#### Rule Verify Permissions on group File [ref]

To properly set the permissions of `/etc/group`, run the command:

    $ sudo chmod 0644 /etc/group

Rationale: | The `/etc/group` file contains information regarding groups that are configured on the system. Protection of this file is important for system security.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_file_permissions_etc_group

References:

cis-csc | 12, 13, 14, 15, 16, 18, 3, 5
cjis | 5.5.2.2
cobit5 | APO01.06, DSS05.04, DSS05.07, DSS06.02
disa | CCI-000366
isa-62443-2009 | 4.3.3.7.3
isa-62443-2013 | SR 2.1, SR 5.2
iso27001-2013 | A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.13.1.1, A.13.1.3, A.13.2.1, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, A.6.1.2, A.7.1.1, A.7.1.2, A.7.3.1, A.8.2.2, A.8.2.3, A.9.1.1, A.9.1.2, A.9.2.3, A.9.4.1, A.9.4.4, A.9.4.5
nerc-cip | CIP-003-8 R5.1.1, CIP-003-8 R5.3, CIP-004-6 R2.3, CIP-007-3 R2.1, CIP-007-3 R2.2, CIP-007-3 R2.3, CIP-007-3 R5.1, CIP-007-3 R5.1.1, CIP-007-3 R5.1.2
nist | CM-6(a), AC-6(1)
nist-csf | PR.AC-4, PR.DS-5
pcidss | Req-8.7.c
os-srg | SRG-OS-000480-GPOS-00227
cis | 6.1.5
anssi | R50
pcidss4 | 2.2.6, 2.2

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    chmod u-xs,g-xws,o-xwt /etc/group

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    - name: Test for existence /etc/group
      stat:
        path: /etc/group
      register: file_exists
      tags:
      - CJIS-5.5.2.2
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - PCI-DSS-Req-8.7.c
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_permissions_etc_group
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Ensure permission u-xs,g-xws,o-xwt on /etc/group
      file:
        path: /etc/group
        mode: u-xs,g-xws,o-xwt
      when: file_exists.stat is defined and file_exists.stat.exists
      tags:
      - CJIS-5.5.2.2
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - PCI-DSS-Req-8.7.c
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_permissions_etc_group
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

#### Rule Verify Permissions on gshadow File [ref]

To properly set the permissions of `/etc/gshadow`, run the command:

    $ sudo chmod 0640 /etc/gshadow

Rationale: | The `/etc/gshadow` file contains group password hashes. Protection of this file is critical for system security.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_file_permissions_etc_gshadow

References:

cis-csc | 12, 13, 14, 15, 16, 18, 3, 5
cobit5 | APO01.06, DSS05.04, DSS05.07, DSS06.02
disa | CCI-000366
isa-62443-2009 | 4.3.3.7.3
isa-62443-2013 | SR 2.1, SR 5.2
iso27001-2013 | A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.13.1.1, A.13.1.3, A.13.2.1, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, A.6.1.2, A.7.1.1, A.7.1.2, A.7.3.1, A.8.2.2, A.8.2.3, A.9.1.1, A.9.1.2, A.9.2.3, A.9.4.1, A.9.4.4, A.9.4.5
nerc-cip | CIP-003-8 R5.1.1, CIP-003-8 R5.3, CIP-004-6 R2.3, CIP-007-3 R2.1, CIP-007-3 R2.2, CIP-007-3 R2.3, CIP-007-3 R5.1, CIP-007-3 R5.1.1, CIP-007-3 R5.1.2
nist | CM-6(a), AC-6(1)
nist-csf | PR.AC-4, PR.DS-5
os-srg | SRG-OS-000480-GPOS-00227
cis | 6.1.9
anssi | R50

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    chmod u-xs,g-xws,o-xwrt /etc/gshadow

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    - name: Test for existence /etc/gshadow
      stat:
        path: /etc/gshadow
      register: file_exists
      tags:
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - configure_strategy
      - file_permissions_etc_gshadow
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Ensure permission u-xs,g-xws,o-xwrt on /etc/gshadow
      file:
        path: /etc/gshadow
        mode: u-xs,g-xws,o-xwrt
      when: file_exists.stat is defined and file_exists.stat.exists
      tags:
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - configure_strategy
      - file_permissions_etc_gshadow
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

#### Rule Verify Permissions on passwd File [ref]

To properly set the permissions of `/etc/passwd`, run the command:

    $ sudo chmod 0644 /etc/passwd

Rationale: | If the `/etc/passwd` file is writable by a group-owner or the world the risk of its compromise is increased. The file contains the list of accounts on the system and associated information, and protection of this file is critical for system security.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_file_permissions_etc_passwd

References:

cis-csc | 12, 13, 14, 15, 16, 18, 3, 5
cjis | 5.5.2.2
cobit5 | APO01.06, DSS05.04, DSS05.07, DSS06.02
disa | CCI-000366
isa-62443-2009 | 4.3.3.7.3
isa-62443-2013 | SR 2.1, SR 5.2
iso27001-2013 | A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.13.1.1, A.13.1.3, A.13.2.1, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, A.6.1.2, A.7.1.1, A.7.1.2, A.7.3.1, A.8.2.2, A.8.2.3, A.9.1.1, A.9.1.2, A.9.2.3, A.9.4.1, A.9.4.4, A.9.4.5
nerc-cip | CIP-003-8 R5.1.1, CIP-003-8 R5.3, CIP-004-6 R2.3, CIP-007-3 R2.1, CIP-007-3 R2.2, CIP-007-3 R2.3, CIP-007-3 R5.1, CIP-007-3 R5.1.1, CIP-007-3 R5.1.2
nist | CM-6(a), AC-6(1)
nist-csf | PR.AC-4, PR.DS-5
pcidss | Req-8.7.c
os-srg | SRG-OS-000480-GPOS-00227
cis | 6.1.2
anssi | R50
pcidss4 | 2.2.6, 2.2

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    chmod u-xs,g-xws,o-xwt /etc/passwd

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    - name: Test for existence /etc/passwd
      stat:
        path: /etc/passwd
      register: file_exists
      tags:
      - CJIS-5.5.2.2
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - PCI-DSS-Req-8.7.c
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_permissions_etc_passwd
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Ensure permission u-xs,g-xws,o-xwt on /etc/passwd
      file:
        path: /etc/passwd
        mode: u-xs,g-xws,o-xwt
      when: file_exists.stat is defined and file_exists.stat.exists
      tags:
      - CJIS-5.5.2.2
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - PCI-DSS-Req-8.7.c
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_permissions_etc_passwd
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

#### Rule Verify Permissions on shadow File [ref]

To properly set the permissions of `/etc/shadow`, run the command:

    $ sudo chmod 0640 /etc/shadow

Rationale: | The `/etc/shadow` file contains the list of local system accounts and stores password hashes. Protection of this file is critical for system security. Failure to give ownership of this file to root provides the designated owner with access to sensitive information which could weaken the system security posture.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_file_permissions_etc_shadow

References:

cis-csc | 12, 13, 14, 15, 16, 18, 3, 5
cjis | 5.5.2.2
cobit5 | APO01.06, DSS05.04, DSS05.07, DSS06.02
disa | CCI-000366
isa-62443-2009 | 4.3.3.7.3
isa-62443-2013 | SR 2.1, SR 5.2
iso27001-2013 | A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.13.1.1, A.13.1.3, A.13.2.1, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, A.6.1.2, A.7.1.1, A.7.1.2, A.7.3.1, A.8.2.2, A.8.2.3, A.9.1.1, A.9.1.2, A.9.2.3, A.9.4.1, A.9.4.4, A.9.4.5
nerc-cip | CIP-003-8 R5.1.1, CIP-003-8 R5.3, CIP-004-6 R2.3, CIP-007-3 R2.1, CIP-007-3 R2.2, CIP-007-3 R2.3, CIP-007-3 R5.1, CIP-007-3 R5.1.1, CIP-007-3 R5.1.2
nist | CM-6(a), AC-6(1)
nist-csf | PR.AC-4, PR.DS-5
pcidss | Req-8.7.c
os-srg | SRG-OS-000480-GPOS-00227
cis | 6.1.4
anssi | R50
pcidss4 | 2.2.6, 2.2

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    chmod u-xs,g-xws,o-xwrt /etc/shadow

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    - name: Test for existence /etc/shadow
      stat:
        path: /etc/shadow
      register: file_exists
      tags:
      - CJIS-5.5.2.2
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - PCI-DSS-Req-8.7.c
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_permissions_etc_shadow
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Ensure permission u-xs,g-xws,o-xwrt on /etc/shadow
      file:
        path: /etc/shadow
        mode: u-xs,g-xws,o-xwrt
      when: file_exists.stat is defined and file_exists.stat.exists
      tags:
      - CJIS-5.5.2.2
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - PCI-DSS-Req-8.7.c
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_permissions_etc_shadow
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

#### Rule Verify that All World-Writable Directories Have Sticky Bits Set [ref]

When the so-called 'sticky bit' is set on a directory, only the owner of a given file may remove that file from the directory. Without the sticky bit, any user with write access to a directory may remove any file in the directory. Setting the sticky bit prevents users from removing each other's files. In cases where there is no reason for a directory to be world-writable, a better solution is to remove that permission rather than to set the sticky bit. However, if a directory is used by a particular application, consult that application's documentation instead of blindly changing modes.
To set the sticky bit on a world-writable directory DIR, run the following command:

    $ sudo chmod +t DIR

Warning: This rule can take a long time to perform the check and might consume a considerable amount of resources depending on the number of directories present on the system. It is not a problem in most cases, but especially systems with a large number of directories can be affected. See `https://access.redhat.com/articles/6999111`.

Rationale:

Failing to set the sticky bit on public directories allows unauthorized users to delete files in the directory structure.
The only authorized public directories are those temporary directories supplied with the system, or those designed to be temporary file repositories. The setting is normally reserved for directories used by the system, by users for temporary file storage (such as `/tmp`), and for directories requiring global read/write access.

Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_dir_perms_world_writable_sticky_bits

References:

cis-csc | 12, 13, 14, 15, 16, 18, 3, 5
cobit5 | APO01.06, DSS05.04, DSS05.07, DSS06.02
disa | CCI-001090
isa-62443-2009 | 4.3.3.7.3
isa-62443-2013 | SR 2.1, SR 5.2
iso27001-2013 | A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.13.1.1, A.13.1.3, A.13.2.1, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, A.6.1.2, A.7.1.1, A.7.1.2, A.7.3.1, A.8.2.2, A.8.2.3, A.9.1.1, A.9.1.2, A.9.2.3, A.9.4.1, A.9.4.4, A.9.4.5
nerc-cip | CIP-003-8 R5.1.1, CIP-003-8 R5.3, CIP-004-6 R2.3, CIP-007-3 R2.1, CIP-007-3 R2.2, CIP-007-3 R2.3, CIP-007-3 R5.1, CIP-007-3 R5.1.1, CIP-007-3 R5.1.2
nist | CM-6(a), AC-6(1)
nist-csf | PR.AC-4, PR.DS-5
os-srg | SRG-OS-000138-GPOS-00069
stigid | UBTU-20-010411
cis | 1.1.22
anssi | R54
pcidss4 | 2.2.6, 2.2
stigref | SV-238332r654171_rule

Remediation Shell script ⇲

    df --local -P | awk '{if (NR!=1) print $6}' \
    | xargs -I '$6' find '$6' -xdev -type d \
    \( -perm -0002 -a ! -perm -1000 \) 2>/dev/null \
    -exec chmod a+t {} +

#### Rule Ensure No World-Writable Files Exist [ref]

It is generally a good idea to remove global (other) write access to a file when it is discovered. However, check with documentation for specific applications before making changes. Also, monitor for recurring world-writable files, as these may be symptoms of a misconfigured application or user account. Finally, this applies to real files and not virtual files that are a part of pseudo file systems such as `sysfs` or `procfs`.
Warning: This rule can take a long time to perform the check and might consume a considerable amount of resources depending on the number of files present on the system. It is not a problem in most cases, but especially systems with a large number of files can be affected. See `https://access.redhat.com/articles/6999111`.

Rationale: | Data in world-writable files can be modified by any user on the system. In almost all circumstances, files can be configured using a combination of user and group permissions to support whatever legitimate access is needed without the risk caused by world-writable files.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_file_permissions_unauthorized_world_writable

References:

cis-csc | 12, 13, 14, 15, 16, 18, 3, 5
cobit5 | APO01.06, DSS05.04, DSS05.07, DSS06.02
isa-62443-2009 | 4.3.3.7.3
isa-62443-2013 | SR 2.1, SR 5.2
iso27001-2013 | A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.13.1.1, A.13.1.3, A.13.2.1, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, A.6.1.2, A.7.1.1, A.7.1.2, A.7.3.1, A.8.2.2, A.8.2.3, A.9.1.1, A.9.1.2, A.9.2.3, A.9.4.1, A.9.4.4, A.9.4.5
nerc-cip | CIP-003-8 R5.1.1, CIP-003-8 R5.3, CIP-004-6 R2.3, CIP-007-3 R2.1, CIP-007-3 R2.2, CIP-007-3 R2.3, CIP-007-3 R5.1, CIP-007-3 R5.1.1, CIP-007-3 R5.1.2
nist | CM-6(a), AC-6(1)
nist-csf | PR.AC-4, PR.DS-5
cis | 6.1.10
anssi | R54
pcidss4 | 2.2.6, 2.2

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    FILTER_NODEV=$(awk '/nodev/ { print $2 }' /proc/filesystems | paste -sd,)

    # Do not consider /sysroot partition because it contains only the physical
    # read-only root on bootable containers.
    PARTITIONS=$(findmnt -n -l -k -it $FILTER_NODEV | awk '{ print $1 }' | grep -v "/sysroot")

    for PARTITION in $PARTITIONS; do
      find "${PARTITION}" -xdev -type f -perm -002 -exec chmod o-w {} \; 2>/dev/null
    done

    # Ensure /tmp is also fixed when tmpfs is used.
    if grep "^tmpfs /tmp" /proc/mounts; then
      find /tmp -xdev -type f -perm -002 -exec chmod o-w {} \; 2>/dev/null
    fi

#### Rule Ensure All Files Are Owned by a Group [ref]

If any file is not group-owned by a valid defined group, the cause of the lack of group-ownership must be investigated. Following this, those files should be deleted or assigned to an appropriate group. The groups need to be defined in `/etc/group` or in `/usr/lib/group` if `nss-altfiles` are configured to be used in `/etc/nsswitch.conf`. Locate the mount points related to local devices by the following command:

    $ findmnt -n -l -k -it $(awk '/nodev/ { print $2 }' /proc/filesystems | paste -sd,)

For all mount points listed by the previous command, it is necessary to search for files which do not belong to a valid group using the following command:

    $ sudo find MOUNTPOINT -xdev -nogroup 2>/dev/null

Warning: This rule only considers local groups as valid groups. If you have your groups defined outside `/etc/group` or `/usr/lib/group`, the rule won't consider those.
Warning: This rule can take a long time to perform the check and might consume a considerable amount of resources depending on the number of files present on the system. It is not a problem in most cases, but especially systems with a large number of files can be affected. See `https://access.redhat.com/articles/6999111`.

Rationale:

Unowned files do not directly imply a security problem, but they are generally a sign that something is amiss. They may be caused by an intruder, by incorrect software installation or draft software removal, or by failure to remove all files belonging to a deleted account, or other similar cases. The files should be repaired so they will not cause problems when accounts are created in the future, and the cause should be discovered and addressed.

Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_file_permissions_ungroupowned

References:

cis-csc | 1, 11, 12, 13, 14, 15, 16, 18, 3, 5
cobit5 | APO01.06, DSS05.02, DSS05.04, DSS05.05, DSS05.07, DSS05.10, DSS06.02, DSS06.03, DSS06.06, DSS06.10
disa | CCI-000366
isa-62443-2009 | 4.3.3.2.2, 4.3.3.5.1, 4.3.3.5.2, 4.3.3.5.3, 4.3.3.5.4, 4.3.3.5.5, 4.3.3.5.6, 4.3.3.5.7, 4.3.3.5.8, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.1, 4.3.3.7.2, 4.3.3.7.3, 4.3.3.7.4
isa-62443-2013 | SR 1.1, SR 1.10, SR 1.11, SR 1.12, SR 1.13, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.6, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 2.2, SR 2.3, SR 2.4, SR 2.5, SR 2.6, SR 2.7, SR 5.2
iso27001-2013 | A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.13.1.1, A.13.1.3, A.13.2.1, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, A.18.1.4, A.6.1.2, A.7.1.1, A.7.1.2, A.7.3.1, A.8.2.2, A.8.2.3, A.9.1.1, A.9.1.2, A.9.2.1, A.9.2.2, A.9.2.3, A.9.2.4, A.9.2.6, A.9.3.1, A.9.4.1, A.9.4.2, A.9.4.3, A.9.4.4, A.9.4.5
nist | CM-6(a), AC-6(1)
nist-csf | PR.AC-1, PR.AC-4, PR.AC-6, PR.AC-7, PR.DS-5, PR.PT-3
os-srg | SRG-OS-000480-GPOS-00227
cis | 6.1.12
anssi | R53
pcidss4 | 2.2.6, 2.2

#### Rule Ensure All Files Are Owned by a User [ref]

If any files are not owned by a user, then the cause of their lack of ownership should be investigated. Following this, the files should be deleted or assigned to an appropriate user. Locate the mount points related to local devices by the following command:

    $ findmnt -n -l -k -it $(awk '/nodev/ { print $2 }' /proc/filesystems | paste -sd,)

For all mount points listed by the previous command, it is necessary to search for files which do not belong to a valid user using the following command:

    $ sudo find MOUNTPOINT -xdev -nouser 2>/dev/null

Warning: For this rule to evaluate centralized user accounts, `getent` must be working properly so that running the command

    getent passwd

returns a list of all users in your organization. If using the System Security Services Daemon (SSSD),

    enumerate = true

must be configured in your organization's domain to return a complete list of users
Warning: This rule can take a long time to perform the check and might consume a considerable amount of resources depending on the number of files present on the system. It is not a problem in most cases, but especially systems with a large number of files can be affected. See `https://access.redhat.com/articles/6999111`.

Rationale:

Unowned files do not directly imply a security problem, but they are generally a sign that something is amiss. They may be caused by an intruder, by incorrect software installation or draft software removal, or by failure to remove all files belonging to a deleted account, or other similar cases. The files should be repaired so they will not cause problems when accounts are created in the future, and the cause should be discovered and addressed.

Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_no_files_unowned_by_user

References:

cis-csc | 11, 12, 13, 14, 15, 16, 18, 3, 5, 9
cobit5 | APO01.06, BAI10.01, BAI10.02, BAI10.03, BAI10.05, DSS05.02, DSS05.04, DSS05.05, DSS05.07, DSS06.02, DSS06.03, DSS06.06
disa | CCI-000366
isa-62443-2009 | 4.3.3.2.2, 4.3.3.5.1, 4.3.3.5.2, 4.3.3.5.3, 4.3.3.5.4, 4.3.3.5.5, 4.3.3.5.6, 4.3.3.5.7, 4.3.3.5.8, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.1, 4.3.3.7.2, 4.3.3.7.3, 4.3.3.7.4, 4.3.4.3.2, 4.3.4.3.3
isa-62443-2013 | SR 1.1, SR 1.10, SR 1.11, SR 1.12, SR 1.13, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.6, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 2.2, SR 2.3, SR 2.4, SR 2.5, SR 2.6, SR 2.7, SR 5.2, SR 7.6
iso27001-2013 | A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.12.1.2, A.12.5.1, A.12.6.2, A.13.1.1, A.13.1.3, A.13.2.1, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, A.14.2.2, A.14.2.3, A.14.2.4, A.6.1.2, A.7.1.1, A.7.1.2, A.7.3.1, A.8.2.2, A.8.2.3, A.9.1.1, A.9.1.2, A.9.2.1, A.9.2.3, A.9.4.1, A.9.4.4, A.9.4.5
nist | CM-6(a), AC-6(1)
nist-csf | PR.AC-4, PR.AC-6, PR.DS-5, PR.IP-1, PR.PT-3
os-srg | SRG-OS-000480-GPOS-00227
cis | 6.1.11
anssi | R53
pcidss4 | 2.2.6, 2.2

#### Rule Verify permissions of log files [ref]

Any operating system providing too much information in error messages risks compromising the data and security of the structure, and content of error messages needs to be carefully considered by the organization. Organizations carefully consider the structure/content of error messages. The extent to which information systems are able to identify and handle error conditions is guided by organizational policy and operational requirements. Information that could be exploited by adversaries includes, for example, erroneous logon attempts with passwords entered by mistake as the username, mission/business information that can be derived from (if not stated explicitly by) information recorded, and personal information, such as account numbers, social security numbers, and credit card numbers.

Rationale: | The Ubuntu 20.04 must generate error messages that provide information necessary for corrective actions without revealing information that could be exploited by adversaries.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_permissions_local_var_log

References:

disa | CCI-001312
nist | SI-11(a), SI-11(b), SI-11.1(iii)
nist-csf | PR.AC-4, PR.DS-5
os-srg | SRG-OS-000205-GPOS-00083
stigid | UBTU-20-010416
cis | 4.2.3
pcidss4 | 10.3.1, 10.3
stigref | SV-238337r880876_rule

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    find  /var/log/  -perm /u+xs,g+xws,o+xwrt ! -name 'history.log' ! -name 'eipp.log.xz' ! -name '*[bw]tmp' ! -name '*lastlog' -type f -regextype posix-extended -regex '.*' -exec chmod u-xs,g-xws,o-xwrt {} \;

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    - name: Find /var/log/ file(s) recursively
      command: find -H /var/log/  -perm /u+xs,g+xws,o+xwrt ! -name "history.log" ! -name
        "eipp.log.xz" ! -name "*[bw]tmp" ! -name "*lastlog" -type f -regextype posix-extended
        -regex ".*"
      register: files_found
      changed_when: false
      failed_when: false
      check_mode: false
      tags:
      - DISA-STIG-UBTU-20-010416
      - NIST-800-53-SI-11(a)
      - NIST-800-53-SI-11(b)
      - NIST-800-53-SI-11.1(iii)
      - PCI-DSSv4-10.3
      - PCI-DSSv4-10.3.1
      - configure_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - permissions_local_var_log

    - name: Set permissions for /var/log/ file(s)
      file:
        path: '{{ item }}'
        mode: u-xs,g-xws,o-xwrt
        state: file
      with_items:
      - '{{ files_found.stdout_lines }}'
      tags:
      - DISA-STIG-UBTU-20-010416
      - NIST-800-53-SI-11(a)
      - NIST-800-53-SI-11(b)
      - NIST-800-53-SI-11.1(iii)
      - PCI-DSSv4-10.3
      - PCI-DSSv4-10.3.1
      - configure_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - permissions_local_var_log

Group Restrict Dynamic Mounting and Unmounting of Filesystems Group contains 8 rules

[ref] Linux includes a number of facilities for the automated addition and removal of filesystems on a running system. These facilities may be necessary in many environments, but this capability also carries some risk -- whether direct risk from allowing users to introduce arbitrary filesystems, or risk that software flaws in the automated mount facility itself could allow an attacker to compromise the system.
This command can be used to list the types of filesystems that are available to the currently executing kernel:

    $ find /lib/modules/`uname -r`/kernel/fs -type f -name '*.ko'

If these filesystems are not required then they can be explicitly disabled in a configuratio file in `/etc/modprobe.d`.

#### Rule Disable the Automounter [ref]

The `autofs` daemon mounts and unmounts filesystems, such as user home directories shared via NFS, on demand. In addition, autofs can be used to handle removable media, and the default configuration provides the cdrom device as `/misc/cd`. However, this method of providing access to removable media is not common, so autofs can almost always be disabled if NFS is not in use. Even if NFS is required, it may be possible to configure filesystem mounts statically by editing `/etc/fstab` rather than relying on the automounter.
The `autofs` service can be disabled with the following command:

    $ sudo systemctl mask --now autofs.service

Rationale: | Disabling the automounter permits the administrator to statically control filesystem mounting through `/etc/fstab`. Additionally, automatically mounting filesystems permits easy introduction of unknown devices, thereby facilitating malicious activity.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_service_autofs_disabled

References:

cis-csc | 1, 12, 15, 16, 5
cobit5 | APO13.01, DSS01.04, DSS05.03, DSS05.04, DSS05.05, DSS05.07, DSS05.10, DSS06.03, DSS06.10
cui | 3.4.6
disa | CCI-000778, CCI-000366, CCI-001958
hipaa | 164.308(a)(3)(i), 164.308(a)(3)(ii)(A), 164.310(d)(1), 164.310(d)(2), 164.312(a)(1), 164.312(a)(2)(iv), 164.312(b)
isa-62443-2009 | 4.3.3.2.2, 4.3.3.5.1, 4.3.3.5.2, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.2, 4.3.3.7.4
isa-62443-2013 | SR 1.1, SR 1.10, SR 1.13, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 2.6
iso27001-2013 | A.11.2.6, A.13.1.1, A.13.2.1, A.18.1.4, A.6.2.1, A.6.2.2, A.7.1.1, A.9.2.1, A.9.2.2, A.9.2.3, A.9.2.4, A.9.2.6, A.9.3.1, A.9.4.2, A.9.4.3
nist | CM-7(a), CM-7(b), CM-6(a), MP-7
nist-csf | PR.AC-1, PR.AC-3, PR.AC-6, PR.AC-7
os-srg | SRG-OS-000114-GPOS-00059, SRG-OS-000378-GPOS-00163, SRG-OS-000480-GPOS-00227
cis | 1.1.23

Remediation Kubernetes snippet ⇲

Complexity: | low
Disruption: | medium
Reboot: | true
Strategy: | disable

    apiVersion: machineconfiguration.openshift.io/v1
    kind: MachineConfig
    spec:
      config:
        ignition:
          version: 3.1.0
        systemd:
          units:
          - name: autofs.service
            enabled: false
            mask: true
          - name: autofs.socket
            enabled: false
            mask: true

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    # Remediation is applicable only in certain platforms
    if ( dpkg-query --show --showformat='${db:Status-Status}\n' 'autofs' 2>/dev/null | grep -q '^installed' && dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed ); then

    SYSTEMCTL_EXEC='/usr/bin/systemctl'
    if [[ $("$SYSTEMCTL_EXEC" is-system-running) != "offline" ]]; then
      "$SYSTEMCTL_EXEC" stop 'autofs.service'
    fi
    "$SYSTEMCTL_EXEC" disable 'autofs.service'
    "$SYSTEMCTL_EXEC" mask 'autofs.service'
    # Disable socket activation if we have a unit file for it
    if "$SYSTEMCTL_EXEC" -q list-unit-files autofs.socket; then
        if [[ $("$SYSTEMCTL_EXEC" is-system-running) != "offline" ]]; then
          "$SYSTEMCTL_EXEC" stop 'autofs.socket'
        fi
        "$SYSTEMCTL_EXEC" mask 'autofs.socket'
    fi
    # The service may not be running because it has been started and failed,
    # so let's reset the state so OVAL checks pass.
    # Service should be 'inactive', not 'failed' after reboot though.
    "$SYSTEMCTL_EXEC" reset-failed 'autofs.service' || true

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation OSBuild Blueprint snippet ⇲

    [customizations.services]
    masked = ["autofs"]

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - NIST-800-171-3.4.6
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-MP-7
      - disable_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - service_autofs_disabled

    - name: Disable the Automounter - Collect systemd Services Present in the System
      ansible.builtin.command: systemctl -q list-unit-files --type service
      register: service_exists
      changed_when: false
      failed_when: service_exists.rc not in [0, 1]
      check_mode: false
      when: ( "autofs" in ansible_facts.packages and "linux-base" in ansible_facts.packages
        )
      tags:
      - NIST-800-171-3.4.6
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-MP-7
      - disable_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - service_autofs_disabled

    - name: Disable the Automounter - Ensure autofs.service is Masked
      ansible.builtin.systemd:
        name: autofs.service
        state: stopped
        enabled: false
        masked: true
      when:
      - ( "autofs" in ansible_facts.packages and "linux-base" in ansible_facts.packages
        )
      - service_exists.stdout_lines is search("autofs.service", multiline=True)
      tags:
      - NIST-800-171-3.4.6
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-MP-7
      - disable_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - service_autofs_disabled

    - name: Unit Socket Exists - autofs.socket
      ansible.builtin.command: systemctl -q list-unit-files autofs.socket
      register: socket_file_exists
      changed_when: false
      failed_when: socket_file_exists.rc not in [0, 1]
      check_mode: false
      when: ( "autofs" in ansible_facts.packages and "linux-base" in ansible_facts.packages
        )
      tags:
      - NIST-800-171-3.4.6
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-MP-7
      - disable_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - service_autofs_disabled

    - name: Disable the Automounter - Disable Socket autofs
      ansible.builtin.systemd:
        name: autofs.socket
        enabled: false
        state: stopped
        masked: true
      when:
      - ( "autofs" in ansible_facts.packages and "linux-base" in ansible_facts.packages
        )
      - socket_file_exists.stdout_lines is search("autofs.socket", multiline=True)
      tags:
      - NIST-800-171-3.4.6
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-MP-7
      - disable_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - service_autofs_disabled

Remediation Puppet snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | enable

    include disable_autofs

    class disable_autofs {
      service {'autofs':
        enable => false,
        ensure => 'stopped',
      }
    }

#### Rule Disable Mounting of cramfs [ref]

To configure the system to prevent the `cramfs` kernel module from being loaded, add the following line to the file `/etc/modprobe.d/cramfs.conf`:

    install cramfs /bin/false

This effectively prevents usage of this uncommon filesystem. The `cramfs` filesystem type is a compressed read-only Linux filesystem embedded in small footprint systems. A `cramfs` image can be used without having to first decompress the image.

Rationale: | Removing support for unneeded filesystem types reduces the local attack surface of the server.
Severity: | low
Rule ID: | xccdf_org.ssgproject.content_rule_kernel_module_cramfs_disabled

References:

cis-csc | 11, 14, 3, 9
cobit5 | BAI10.01, BAI10.02, BAI10.03, BAI10.05, DSS05.02, DSS05.05, DSS06.06
cui | 3.4.6
disa | CCI-000381
isa-62443-2009 | 4.3.3.5.1, 4.3.3.5.2, 4.3.3.5.3, 4.3.3.5.4, 4.3.3.5.5, 4.3.3.5.6, 4.3.3.5.7, 4.3.3.5.8, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.1, 4.3.3.7.2, 4.3.3.7.3, 4.3.3.7.4, 4.3.4.3.2, 4.3.4.3.3
isa-62443-2013 | SR 1.1, SR 1.10, SR 1.11, SR 1.12, SR 1.13, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.6, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 2.2, SR 2.3, SR 2.4, SR 2.5, SR 2.6, SR 2.7, SR 7.6
iso27001-2013 | A.12.1.2, A.12.5.1, A.12.6.2, A.14.2.2, A.14.2.3, A.14.2.4, A.9.1.2
nist | CM-7(a), CM-7(b), CM-6(a)
nist-csf | PR.IP-1, PR.PT-3
os-srg | SRG-OS-000095-GPOS-00049
cis | 1.1.1.1

Remediation Shell script ⇲

Complexity: | low
Disruption: | medium
Reboot: | true
Strategy: | disable

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    if LC_ALL=C grep -q -m 1 "^install cramfs" /etc/modprobe.d/cramfs.conf ; then

    	sed -i 's#^install cramfs.*#install cramfs /bin/false#g' /etc/modprobe.d/cramfs.conf
    else
    	echo -e "\n# Disable per security requirements" >> /etc/modprobe.d/cramfs.conf
    	echo "install cramfs /bin/false" >> /etc/modprobe.d/cramfs.conf
    fi

    if ! LC_ALL=C grep -q -m 1 "^blacklist cramfs$" /etc/modprobe.d/cramfs.conf ; then
    	echo "blacklist cramfs" >> /etc/modprobe.d/cramfs.conf
    fi

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | medium
Reboot: | true
Strategy: | disable

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - NIST-800-171-3.4.6
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - disable_strategy
      - kernel_module_cramfs_disabled
      - low_complexity
      - low_severity
      - medium_disruption
      - reboot_required

    - name: Ensure kernel module 'cramfs' is disabled
      lineinfile:
        create: true
        dest: /etc/modprobe.d/cramfs.conf
        regexp: install\s+cramfs
        line: install cramfs /bin/false
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-171-3.4.6
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - disable_strategy
      - kernel_module_cramfs_disabled
      - low_complexity
      - low_severity
      - medium_disruption
      - reboot_required

    - name: Ensure kernel module 'cramfs' is blacklisted
      lineinfile:
        create: true
        dest: /etc/modprobe.d/cramfs.conf
        regexp: ^blacklist cramfs$
        line: blacklist cramfs
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-171-3.4.6
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - disable_strategy
      - kernel_module_cramfs_disabled
      - low_complexity
      - low_severity
      - medium_disruption
      - reboot_required

#### Rule Disable Mounting of freevxfs [ref]

To configure the system to prevent the `freevxfs` kernel module from being loaded, add the following line to the file `/etc/modprobe.d/freevxfs.conf`:

    install freevxfs /bin/false

This effectively prevents usage of this uncommon filesystem.

Rationale: | Linux kernel modules which implement filesystems that are not needed by the local system should be disabled.
Severity: | low
Rule ID: | xccdf_org.ssgproject.content_rule_kernel_module_freevxfs_disabled

References:

cis-csc | 11, 14, 3, 9
cobit5 | BAI10.01, BAI10.02, BAI10.03, BAI10.05, DSS05.02, DSS05.05, DSS06.06
cui | 3.4.6
isa-62443-2009 | 4.3.3.5.1, 4.3.3.5.2, 4.3.3.5.3, 4.3.3.5.4, 4.3.3.5.5, 4.3.3.5.6, 4.3.3.5.7, 4.3.3.5.8, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.1, 4.3.3.7.2, 4.3.3.7.3, 4.3.3.7.4, 4.3.4.3.2, 4.3.4.3.3
isa-62443-2013 | SR 1.1, SR 1.10, SR 1.11, SR 1.12, SR 1.13, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.6, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 2.2, SR 2.3, SR 2.4, SR 2.5, SR 2.6, SR 2.7, SR 7.6
iso27001-2013 | A.12.1.2, A.12.5.1, A.12.6.2, A.14.2.2, A.14.2.3, A.14.2.4, A.9.1.2
nist | CM-7(a), CM-7(b), CM-6(a)
nist-csf | PR.IP-1, PR.PT-3
cis | 1.1.1.2

Remediation Shell script ⇲

Complexity: | low
Disruption: | medium
Reboot: | true
Strategy: | disable

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    if LC_ALL=C grep -q -m 1 "^install freevxfs" /etc/modprobe.d/freevxfs.conf ; then

    	sed -i 's#^install freevxfs.*#install freevxfs /bin/false#g' /etc/modprobe.d/freevxfs.conf
    else
    	echo -e "\n# Disable per security requirements" >> /etc/modprobe.d/freevxfs.conf
    	echo "install freevxfs /bin/false" >> /etc/modprobe.d/freevxfs.conf
    fi

    if ! LC_ALL=C grep -q -m 1 "^blacklist freevxfs$" /etc/modprobe.d/freevxfs.conf ; then
    	echo "blacklist freevxfs" >> /etc/modprobe.d/freevxfs.conf
    fi

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | medium
Reboot: | true
Strategy: | disable

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - NIST-800-171-3.4.6
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - disable_strategy
      - kernel_module_freevxfs_disabled
      - low_complexity
      - low_severity
      - medium_disruption
      - reboot_required

    - name: Ensure kernel module 'freevxfs' is disabled
      lineinfile:
        create: true
        dest: /etc/modprobe.d/freevxfs.conf
        regexp: install\s+freevxfs
        line: install freevxfs /bin/false
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-171-3.4.6
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - disable_strategy
      - kernel_module_freevxfs_disabled
      - low_complexity
      - low_severity
      - medium_disruption
      - reboot_required

    - name: Ensure kernel module 'freevxfs' is blacklisted
      lineinfile:
        create: true
        dest: /etc/modprobe.d/freevxfs.conf
        regexp: ^blacklist freevxfs$
        line: blacklist freevxfs
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-171-3.4.6
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - disable_strategy
      - kernel_module_freevxfs_disabled
      - low_complexity
      - low_severity
      - medium_disruption
      - reboot_required

#### Rule Disable Mounting of hfs [ref]

To configure the system to prevent the `hfs` kernel module from being loaded, add the following line to the file `/etc/modprobe.d/hfs.conf`:

    install hfs /bin/false

This effectively prevents usage of this uncommon filesystem.

Rationale: | Linux kernel modules which implement filesystems that are not needed by the local system should be disabled.
Severity: | low
Rule ID: | xccdf_org.ssgproject.content_rule_kernel_module_hfs_disabled

References:

cis-csc | 11, 14, 3, 9
cobit5 | BAI10.01, BAI10.02, BAI10.03, BAI10.05, DSS05.02, DSS05.05, DSS06.06
cui | 3.4.6
isa-62443-2009 | 4.3.3.5.1, 4.3.3.5.2, 4.3.3.5.3, 4.3.3.5.4, 4.3.3.5.5, 4.3.3.5.6, 4.3.3.5.7, 4.3.3.5.8, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.1, 4.3.3.7.2, 4.3.3.7.3, 4.3.3.7.4, 4.3.4.3.2, 4.3.4.3.3
isa-62443-2013 | SR 1.1, SR 1.10, SR 1.11, SR 1.12, SR 1.13, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.6, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 2.2, SR 2.3, SR 2.4, SR 2.5, SR 2.6, SR 2.7, SR 7.6
iso27001-2013 | A.12.1.2, A.12.5.1, A.12.6.2, A.14.2.2, A.14.2.3, A.14.2.4, A.9.1.2
nist | CM-7(a), CM-7(b), CM-6(a)
nist-csf | PR.IP-1, PR.PT-3
cis | 1.1.1.4

Remediation Shell script ⇲

Complexity: | low
Disruption: | medium
Reboot: | true
Strategy: | disable

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    if LC_ALL=C grep -q -m 1 "^install hfs" /etc/modprobe.d/hfs.conf ; then

    	sed -i 's#^install hfs.*#install hfs /bin/false#g' /etc/modprobe.d/hfs.conf
    else
    	echo -e "\n# Disable per security requirements" >> /etc/modprobe.d/hfs.conf
    	echo "install hfs /bin/false" >> /etc/modprobe.d/hfs.conf
    fi

    if ! LC_ALL=C grep -q -m 1 "^blacklist hfs$" /etc/modprobe.d/hfs.conf ; then
    	echo "blacklist hfs" >> /etc/modprobe.d/hfs.conf
    fi

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | medium
Reboot: | true
Strategy: | disable

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - NIST-800-171-3.4.6
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - disable_strategy
      - kernel_module_hfs_disabled
      - low_complexity
      - low_severity
      - medium_disruption
      - reboot_required

    - name: Ensure kernel module 'hfs' is disabled
      lineinfile:
        create: true
        dest: /etc/modprobe.d/hfs.conf
        regexp: install\s+hfs
        line: install hfs /bin/false
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-171-3.4.6
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - disable_strategy
      - kernel_module_hfs_disabled
      - low_complexity
      - low_severity
      - medium_disruption
      - reboot_required

    - name: Ensure kernel module 'hfs' is blacklisted
      lineinfile:
        create: true
        dest: /etc/modprobe.d/hfs.conf
        regexp: ^blacklist hfs$
        line: blacklist hfs
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-171-3.4.6
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - disable_strategy
      - kernel_module_hfs_disabled
      - low_complexity
      - low_severity
      - medium_disruption
      - reboot_required

#### Rule Disable Mounting of hfsplus [ref]

To configure the system to prevent the `hfsplus` kernel module from being loaded, add the following line to the file `/etc/modprobe.d/hfsplus.conf`:

    install hfsplus /bin/false

This effectively prevents usage of this uncommon filesystem.

Rationale: | Linux kernel modules which implement filesystems that are not needed by the local system should be disabled.
Severity: | low
Rule ID: | xccdf_org.ssgproject.content_rule_kernel_module_hfsplus_disabled

References:

cis-csc | 11, 14, 3, 9
cobit5 | BAI10.01, BAI10.02, BAI10.03, BAI10.05, DSS05.02, DSS05.05, DSS06.06
cui | 3.4.6
isa-62443-2009 | 4.3.3.5.1, 4.3.3.5.2, 4.3.3.5.3, 4.3.3.5.4, 4.3.3.5.5, 4.3.3.5.6, 4.3.3.5.7, 4.3.3.5.8, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.1, 4.3.3.7.2, 4.3.3.7.3, 4.3.3.7.4, 4.3.4.3.2, 4.3.4.3.3
isa-62443-2013 | SR 1.1, SR 1.10, SR 1.11, SR 1.12, SR 1.13, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.6, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 2.2, SR 2.3, SR 2.4, SR 2.5, SR 2.6, SR 2.7, SR 7.6
iso27001-2013 | A.12.1.2, A.12.5.1, A.12.6.2, A.14.2.2, A.14.2.3, A.14.2.4, A.9.1.2
nist | CM-7(a), CM-7(b), CM-6(a)
nist-csf | PR.IP-1, PR.PT-3
cis | 1.1.1.5

Remediation Shell script ⇲

Complexity: | low
Disruption: | medium
Reboot: | true
Strategy: | disable

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    if LC_ALL=C grep -q -m 1 "^install hfsplus" /etc/modprobe.d/hfsplus.conf ; then

    	sed -i 's#^install hfsplus.*#install hfsplus /bin/false#g' /etc/modprobe.d/hfsplus.conf
    else
    	echo -e "\n# Disable per security requirements" >> /etc/modprobe.d/hfsplus.conf
    	echo "install hfsplus /bin/false" >> /etc/modprobe.d/hfsplus.conf
    fi

    if ! LC_ALL=C grep -q -m 1 "^blacklist hfsplus$" /etc/modprobe.d/hfsplus.conf ; then
    	echo "blacklist hfsplus" >> /etc/modprobe.d/hfsplus.conf
    fi

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | medium
Reboot: | true
Strategy: | disable

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - NIST-800-171-3.4.6
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - disable_strategy
      - kernel_module_hfsplus_disabled
      - low_complexity
      - low_severity
      - medium_disruption
      - reboot_required

    - name: Ensure kernel module 'hfsplus' is disabled
      lineinfile:
        create: true
        dest: /etc/modprobe.d/hfsplus.conf
        regexp: install\s+hfsplus
        line: install hfsplus /bin/false
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-171-3.4.6
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - disable_strategy
      - kernel_module_hfsplus_disabled
      - low_complexity
      - low_severity
      - medium_disruption
      - reboot_required

    - name: Ensure kernel module 'hfsplus' is blacklisted
      lineinfile:
        create: true
        dest: /etc/modprobe.d/hfsplus.conf
        regexp: ^blacklist hfsplus$
        line: blacklist hfsplus
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-171-3.4.6
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - disable_strategy
      - kernel_module_hfsplus_disabled
      - low_complexity
      - low_severity
      - medium_disruption
      - reboot_required

#### Rule Disable Mounting of jffs2 [ref]

To configure the system to prevent the `jffs2` kernel module from being loaded, add the following line to the file `/etc/modprobe.d/jffs2.conf`:

    install jffs2 /bin/false

This effectively prevents usage of this uncommon filesystem.

Rationale: | Linux kernel modules which implement filesystems that are not needed by the local system should be disabled.
Severity: | low
Rule ID: | xccdf_org.ssgproject.content_rule_kernel_module_jffs2_disabled

References:

cis-csc | 11, 14, 3, 9
cobit5 | BAI10.01, BAI10.02, BAI10.03, BAI10.05, DSS05.02, DSS05.05, DSS06.06
cui | 3.4.6
isa-62443-2009 | 4.3.3.5.1, 4.3.3.5.2, 4.3.3.5.3, 4.3.3.5.4, 4.3.3.5.5, 4.3.3.5.6, 4.3.3.5.7, 4.3.3.5.8, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.1, 4.3.3.7.2, 4.3.3.7.3, 4.3.3.7.4, 4.3.4.3.2, 4.3.4.3.3
isa-62443-2013 | SR 1.1, SR 1.10, SR 1.11, SR 1.12, SR 1.13, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.6, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 2.2, SR 2.3, SR 2.4, SR 2.5, SR 2.6, SR 2.7, SR 7.6
iso27001-2013 | A.12.1.2, A.12.5.1, A.12.6.2, A.14.2.2, A.14.2.3, A.14.2.4, A.9.1.2
nist | CM-7(a), CM-7(b), CM-6(a)
nist-csf | PR.IP-1, PR.PT-3
cis | 1.1.1.3

Remediation Shell script ⇲

Complexity: | low
Disruption: | medium
Reboot: | true
Strategy: | disable

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    if LC_ALL=C grep -q -m 1 "^install jffs2" /etc/modprobe.d/jffs2.conf ; then

    	sed -i 's#^install jffs2.*#install jffs2 /bin/false#g' /etc/modprobe.d/jffs2.conf
    else
    	echo -e "\n# Disable per security requirements" >> /etc/modprobe.d/jffs2.conf
    	echo "install jffs2 /bin/false" >> /etc/modprobe.d/jffs2.conf
    fi

    if ! LC_ALL=C grep -q -m 1 "^blacklist jffs2$" /etc/modprobe.d/jffs2.conf ; then
    	echo "blacklist jffs2" >> /etc/modprobe.d/jffs2.conf
    fi

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | medium
Reboot: | true
Strategy: | disable

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - NIST-800-171-3.4.6
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - disable_strategy
      - kernel_module_jffs2_disabled
      - low_complexity
      - low_severity
      - medium_disruption
      - reboot_required

    - name: Ensure kernel module 'jffs2' is disabled
      lineinfile:
        create: true
        dest: /etc/modprobe.d/jffs2.conf
        regexp: install\s+jffs2
        line: install jffs2 /bin/false
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-171-3.4.6
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - disable_strategy
      - kernel_module_jffs2_disabled
      - low_complexity
      - low_severity
      - medium_disruption
      - reboot_required

    - name: Ensure kernel module 'jffs2' is blacklisted
      lineinfile:
        create: true
        dest: /etc/modprobe.d/jffs2.conf
        regexp: ^blacklist jffs2$
        line: blacklist jffs2
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-171-3.4.6
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - disable_strategy
      - kernel_module_jffs2_disabled
      - low_complexity
      - low_severity
      - medium_disruption
      - reboot_required

#### Rule Disable Mounting of udf [ref]

To configure the system to prevent the `udf` kernel module from being loaded, add the following line to the file `/etc/modprobe.d/udf.conf`:

    install udf /bin/false

This effectively prevents usage of this uncommon filesystem. The `udf` filesystem type is the universal disk format used to implement the ISO/IEC 13346 and ECMA-167 specifications. This is an open vendor filesystem type for data storage on a broad range of media. This filesystem type is neccessary to support writing DVDs and newer optical disc formats.

Rationale: | Removing support for unneeded filesystem types reduces the local attack surface of the system.
Severity: | low
Rule ID: | xccdf_org.ssgproject.content_rule_kernel_module_udf_disabled

References:

cis-csc | 11, 14, 3, 9
cobit5 | BAI10.01, BAI10.02, BAI10.03, BAI10.05, DSS05.02, DSS05.05, DSS06.06
cui | 3.4.6
isa-62443-2009 | 4.3.3.5.1, 4.3.3.5.2, 4.3.3.5.3, 4.3.3.5.4, 4.3.3.5.5, 4.3.3.5.6, 4.3.3.5.7, 4.3.3.5.8, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.1, 4.3.3.7.2, 4.3.3.7.3, 4.3.3.7.4, 4.3.4.3.2, 4.3.4.3.3
isa-62443-2013 | SR 1.1, SR 1.10, SR 1.11, SR 1.12, SR 1.13, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.6, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 2.2, SR 2.3, SR 2.4, SR 2.5, SR 2.6, SR 2.7, SR 7.6
iso27001-2013 | A.12.1.2, A.12.5.1, A.12.6.2, A.14.2.2, A.14.2.3, A.14.2.4, A.9.1.2
nist | CM-7(a), CM-7(b), CM-6(a)
nist-csf | PR.IP-1, PR.PT-3
cis | 1.1.1.6

Remediation Shell script ⇲

Complexity: | low
Disruption: | medium
Reboot: | true
Strategy: | disable

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    if LC_ALL=C grep -q -m 1 "^install udf" /etc/modprobe.d/udf.conf ; then

    	sed -i 's#^install udf.*#install udf /bin/false#g' /etc/modprobe.d/udf.conf
    else
    	echo -e "\n# Disable per security requirements" >> /etc/modprobe.d/udf.conf
    	echo "install udf /bin/false" >> /etc/modprobe.d/udf.conf
    fi

    if ! LC_ALL=C grep -q -m 1 "^blacklist udf$" /etc/modprobe.d/udf.conf ; then
    	echo "blacklist udf" >> /etc/modprobe.d/udf.conf
    fi

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | medium
Reboot: | true
Strategy: | disable

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - NIST-800-171-3.4.6
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - disable_strategy
      - kernel_module_udf_disabled
      - low_complexity
      - low_severity
      - medium_disruption
      - reboot_required

    - name: Ensure kernel module 'udf' is disabled
      lineinfile:
        create: true
        dest: /etc/modprobe.d/udf.conf
        regexp: install\s+udf
        line: install udf /bin/false
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-171-3.4.6
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - disable_strategy
      - kernel_module_udf_disabled
      - low_complexity
      - low_severity
      - medium_disruption
      - reboot_required

    - name: Ensure kernel module 'udf' is blacklisted
      lineinfile:
        create: true
        dest: /etc/modprobe.d/udf.conf
        regexp: ^blacklist udf$
        line: blacklist udf
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-171-3.4.6
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - disable_strategy
      - kernel_module_udf_disabled
      - low_complexity
      - low_severity
      - medium_disruption
      - reboot_required

#### Rule Disable Modprobe Loading of USB Storage Driver [ref]

To prevent USB storage devices from being used, configure the kernel module loading system to prevent automatic loading of the USB storage driver. To configure the system to prevent the `usb-storage` kernel module from being loaded, add the following line to the file `/etc/modprobe.d/usb-storage.conf`:

    install usb-storage /bin/false

This will prevent the `modprobe` program from loading the `usb-storage` module, but will not prevent an administrator (or another program) from using the `insmod` program to load the module manually.

Rationale: | USB storage devices such as thumb drives can be used to introduce malicious software.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_kernel_module_usb-storage_disabled

References:

cis-csc | 1, 12, 15, 16, 5
cobit5 | APO13.01, DSS01.04, DSS05.03, DSS05.04, DSS05.05, DSS05.07, DSS05.10, DSS06.03, DSS06.10
cui | 3.1.21
disa | CCI-000778, CCI-001958, CCI-003959
hipaa | 164.308(a)(3)(i), 164.308(a)(3)(ii)(A), 164.310(d)(1), 164.310(d)(2), 164.312(a)(1), 164.312(a)(2)(iv), 164.312(b)
isa-62443-2009 | 4.3.3.2.2, 4.3.3.5.1, 4.3.3.5.2, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.2, 4.3.3.7.4
isa-62443-2013 | SR 1.1, SR 1.10, SR 1.13, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 2.6
iso27001-2013 | A.11.2.6, A.13.1.1, A.13.2.1, A.18.1.4, A.6.2.1, A.6.2.2, A.7.1.1, A.9.2.1, A.9.2.2, A.9.2.3, A.9.2.4, A.9.2.6, A.9.3.1, A.9.4.2, A.9.4.3
nist | CM-7(a), CM-7(b), CM-6(a), MP-7
nist-csf | PR.AC-1, PR.AC-3, PR.AC-6, PR.AC-7
os-srg | SRG-OS-000114-GPOS-00059, SRG-OS-000378-GPOS-00163, SRG-OS-000480-GPOS-00227
app-srg-ctr | SRG-APP-000141-CTR-000315
stigid | UBTU-20-010461
cis | 1.1.24
pcidss4 | 3.4.2, 3.4
stigref | SV-251505r942851_rule

Remediation Shell script ⇲

Complexity: | low
Disruption: | medium
Reboot: | true
Strategy: | disable

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    if LC_ALL=C grep -q -m 1 "^install usb-storage" /etc/modprobe.d/usb-storage.conf ; then

    	sed -i 's#^install usb-storage.*#install usb-storage /bin/false#g' /etc/modprobe.d/usb-storage.conf
    else
    	echo -e "\n# Disable per security requirements" >> /etc/modprobe.d/usb-storage.conf
    	echo "install usb-storage /bin/false" >> /etc/modprobe.d/usb-storage.conf
    fi

    if ! LC_ALL=C grep -q -m 1 "^blacklist usb-storage$" /etc/modprobe.d/usb-storage.conf ; then
    	echo "blacklist usb-storage" >> /etc/modprobe.d/usb-storage.conf
    fi

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | medium
Reboot: | true
Strategy: | disable

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - DISA-STIG-UBTU-20-010461
      - NIST-800-171-3.1.21
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-MP-7
      - PCI-DSSv4-3.4
      - PCI-DSSv4-3.4.2
      - disable_strategy
      - kernel_module_usb-storage_disabled
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required

    - name: Ensure kernel module 'usb-storage' is disabled
      lineinfile:
        create: true
        dest: /etc/modprobe.d/usb-storage.conf
        regexp: install\s+usb-storage
        line: install usb-storage /bin/false
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - DISA-STIG-UBTU-20-010461
      - NIST-800-171-3.1.21
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-MP-7
      - PCI-DSSv4-3.4
      - PCI-DSSv4-3.4.2
      - disable_strategy
      - kernel_module_usb-storage_disabled
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required

    - name: Ensure kernel module 'usb-storage' is blacklisted
      lineinfile:
        create: true
        dest: /etc/modprobe.d/usb-storage.conf
        regexp: ^blacklist usb-storage$
        line: blacklist usb-storage
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - DISA-STIG-UBTU-20-010461
      - NIST-800-171-3.1.21
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-MP-7
      - PCI-DSSv4-3.4
      - PCI-DSSv4-3.4.2
      - disable_strategy
      - kernel_module_usb-storage_disabled
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required

Group Restrict Partition Mount Options Group contains 10 rules
[ref] System partitions can be mounted with certain options that limit what files on those partitions can do. These options are set in the `/etc/fstab` configuration file, and can be used to make certain types of malicious behavior more difficult.

#### Rule Add nodev Option to /dev/shm [ref]

The `nodev` mount option can be used to prevent creation of device files in `/dev/shm`. Legitimate character and block devices should not exist within temporary directories like `/dev/shm`. Add the `nodev` option to the fourth column of `/etc/fstab` for the line which controls mounting of `/dev/shm`.
Rationale: | The only legitimate location for device files is the `/dev` directory located on the root partition. The only exception to this is chroot jails.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_mount_option_dev_shm_nodev

References:

cis-csc | 11, 13, 14, 3, 8, 9
cobit5 | APO13.01, BAI10.01, BAI10.02, BAI10.03, BAI10.05, DSS05.02, DSS05.05, DSS05.06, DSS06.06
disa | CCI-001764
isa-62443-2009 | 4.3.3.5.1, 4.3.3.5.2, 4.3.3.5.3, 4.3.3.5.4, 4.3.3.5.5, 4.3.3.5.6, 4.3.3.5.7, 4.3.3.5.8, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.1, 4.3.3.7.2, 4.3.3.7.3, 4.3.3.7.4, 4.3.4.3.2, 4.3.4.3.3
isa-62443-2013 | SR 1.1, SR 1.10, SR 1.11, SR 1.12, SR 1.13, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.6, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 2.2, SR 2.3, SR 2.4, SR 2.5, SR 2.6, SR 2.7, SR 7.6
iso27001-2013 | A.11.2.9, A.12.1.2, A.12.5.1, A.12.6.2, A.14.2.2, A.14.2.3, A.14.2.4, A.8.2.1, A.8.2.2, A.8.2.3, A.8.3.1, A.8.3.3, A.9.1.2
nerc-cip | CIP-003-8 R5.1.1, CIP-003-8 R5.3, CIP-004-6 R2.3, CIP-007-3 R2.1, CIP-007-3 R2.2, CIP-007-3 R2.3, CIP-007-3 R5.1, CIP-007-3 R5.1.1, CIP-007-3 R5.1.2
nist | CM-7(a), CM-7(b), CM-6(a), AC-6, AC-6(1), MP-7
nist-csf | PR.IP-1, PR.PT-2, PR.PT-3
os-srg | SRG-OS-000368-GPOS-00154
cis | 1.1.7

Remediation Shell script ⇲

Reboot: | false

    # Remediation is applicable only in certain platforms
    if ! ( [ -f /.dockerenv ] || [ -f /run/.containerenv ] ); then

    function perform_remediation {

        mount_point_match_regexp="$(printf "^[[:space:]]*[^#].*[[:space:]]%s[[:space:]]" /dev/shm)"

        # If the mount point is not in /etc/fstab, get previous mount options from /etc/mtab
        if ! grep -q "$mount_point_match_regexp" /etc/fstab; then
            # runtime opts without some automatic kernel/userspace-added defaults
            previous_mount_opts=$(grep "$mount_point_match_regexp" /etc/mtab | head -1 |  awk '{print $4}' \
                        | sed -E "s/(rw|defaults|seclabel|nodev)(,|$)//g;s/,$//")
            [ "$previous_mount_opts" ] && previous_mount_opts+=","
            # In iso9660 filesystems mtab could describe a "blocksize" value, this should be reflected in
            # fstab as "block".  The next variable is to satisfy shellcheck SC2050.
            fs_type="tmpfs"
            if [  "$fs_type" == "iso9660" ] ; then
                previous_mount_opts=$(sed 's/blocksize=/block=/' <<< "$previous_mount_opts")
            fi
            echo "tmpfs /dev/shm tmpfs defaults,${previous_mount_opts}nodev 0 0" >> /etc/fstab
        # If the mount_opt option is not already in the mount point's /etc/fstab entry, add it
        elif ! grep "$mount_point_match_regexp" /etc/fstab | grep -q "nodev"; then
            previous_mount_opts=$(grep "$mount_point_match_regexp" /etc/fstab | awk '{print $4}')
            sed -i "s|\(${mount_point_match_regexp}.*${previous_mount_opts}\)|\1,nodev|" /etc/fstab
        fi

        if mkdir -p "/dev/shm"; then
            if mountpoint -q "/dev/shm"; then
                mount -o remount --target "/dev/shm"
            fi
        fi
    }

    perform_remediation

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | high
Reboot: | false
Strategy: | configure

    - name: 'Add nodev Option to /dev/shm: Check information associated to mountpoint'
      command: findmnt  '/dev/shm'
      register: device_name
      failed_when: device_name.rc > 1
      changed_when: false
      when: not ( ansible_virtualization_type in ["docker", "lxc", "openvz", "podman",
        "container"] )
      tags:
      - NIST-800-53-AC-6
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-MP-7
      - configure_strategy
      - high_disruption
      - low_complexity
      - medium_severity
      - mount_option_dev_shm_nodev
      - no_reboot_needed

    - name: 'Add nodev Option to /dev/shm: Create mount_info dictionary variable'
      set_fact:
        mount_info: '{{ mount_info|default({})|combine({item.0: item.1}) }}'
      with_together:
      - '{{ device_name.stdout_lines[0].split() | list | lower }}'
      - '{{ device_name.stdout_lines[1].split() | list }}'
      when:
      - not ( ansible_virtualization_type in ["docker", "lxc", "openvz", "podman", "container"]
        )
      - device_name.stdout is defined and device_name.stdout_lines is defined
      - (device_name.stdout | length > 0)
      tags:
      - NIST-800-53-AC-6
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-MP-7
      - configure_strategy
      - high_disruption
      - low_complexity
      - medium_severity
      - mount_option_dev_shm_nodev
      - no_reboot_needed

    - name: 'Add nodev Option to /dev/shm: If /dev/shm not mounted, craft mount_info manually'
      set_fact:
        mount_info: '{{ mount_info|default({})|combine({item.0: item.1}) }}'
      with_together:
      - - target
        - source
        - fstype
        - options
      - - /dev/shm
        - tmpfs
        - tmpfs
        - defaults
      when:
      - not ( ansible_virtualization_type in ["docker", "lxc", "openvz", "podman", "container"]
        )
      - ("" | length == 0)
      - device_name.stdout is defined and device_name.stdout_lines is defined
      - (device_name.stdout | length == 0)
      tags:
      - NIST-800-53-AC-6
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-MP-7
      - configure_strategy
      - high_disruption
      - low_complexity
      - medium_severity
      - mount_option_dev_shm_nodev
      - no_reboot_needed

    - name: 'Add nodev Option to /dev/shm: Make sure nodev option is part of the to /dev/shm
        options'
      set_fact:
        mount_info: '{{ mount_info | combine( {''options'':''''~mount_info.options~'',nodev''
          }) }}'
      when:
      - not ( ansible_virtualization_type in ["docker", "lxc", "openvz", "podman", "container"]
        )
      - mount_info is defined and "nodev" not in mount_info.options
      tags:
      - NIST-800-53-AC-6
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-MP-7
      - configure_strategy
      - high_disruption
      - low_complexity
      - medium_severity
      - mount_option_dev_shm_nodev
      - no_reboot_needed

    - name: 'Add nodev Option to /dev/shm: Ensure /dev/shm is mounted with nodev option'
      mount:
        path: /dev/shm
        src: '{{ mount_info.source }}'
        opts: '{{ mount_info.options }}'
        state: mounted
        fstype: '{{ mount_info.fstype }}'
      when:
      - not ( ansible_virtualization_type in ["docker", "lxc", "openvz", "podman", "container"]
        )
      - mount_info is defined
      - (device_name.stdout is defined and (device_name.stdout | length > 0)) or ("" |
        length == 0)
      tags:
      - NIST-800-53-AC-6
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-MP-7
      - configure_strategy
      - high_disruption
      - low_complexity
      - medium_severity
      - mount_option_dev_shm_nodev
      - no_reboot_needed

#### Rule Add noexec Option to /dev/shm [ref]

The `noexec` mount option can be used to prevent binaries from being executed out of `/dev/shm`. It can be dangerous to allow the execution of binaries from world-writable temporary storage directories such as `/dev/shm`. Add the `noexec` option to the fourth column of `/etc/fstab` for the line which controls mounting of `/dev/shm`.
Rationale: | Allowing users to execute binaries from world-writable directories such as `/dev/shm` can expose the system to potential compromise.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_mount_option_dev_shm_noexec

References:

cis-csc | 11, 13, 14, 3, 8, 9
cobit5 | APO13.01, BAI10.01, BAI10.02, BAI10.03, BAI10.05, DSS05.02, DSS05.05, DSS05.06, DSS06.06
disa | CCI-001764
isa-62443-2009 | 4.3.3.5.1, 4.3.3.5.2, 4.3.3.5.3, 4.3.3.5.4, 4.3.3.5.5, 4.3.3.5.6, 4.3.3.5.7, 4.3.3.5.8, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.1, 4.3.3.7.2, 4.3.3.7.3, 4.3.3.7.4, 4.3.4.3.2, 4.3.4.3.3
isa-62443-2013 | SR 1.1, SR 1.10, SR 1.11, SR 1.12, SR 1.13, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.6, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 2.2, SR 2.3, SR 2.4, SR 2.5, SR 2.6, SR 2.7, SR 7.6
iso27001-2013 | A.11.2.9, A.12.1.2, A.12.5.1, A.12.6.2, A.14.2.2, A.14.2.3, A.14.2.4, A.8.2.1, A.8.2.2, A.8.2.3, A.8.3.1, A.8.3.3, A.9.1.2
nerc-cip | CIP-003-8 R5.1.1, CIP-003-8 R5.3, CIP-004-6 R2.3, CIP-007-3 R2.1, CIP-007-3 R2.2, CIP-007-3 R2.3, CIP-007-3 R5.1, CIP-007-3 R5.1.1, CIP-007-3 R5.1.2
nist | CM-7(a), CM-7(b), CM-6(a), AC-6, AC-6(1), MP-7
nist-csf | PR.IP-1, PR.PT-2, PR.PT-3
os-srg | SRG-OS-000368-GPOS-00154
cis | 1.1.9

Remediation Shell script ⇲

Reboot: | false

    # Remediation is applicable only in certain platforms
    if ! ( [ -f /.dockerenv ] || [ -f /run/.containerenv ] ); then

    function perform_remediation {

        mount_point_match_regexp="$(printf "^[[:space:]]*[^#].*[[:space:]]%s[[:space:]]" /dev/shm)"

        # If the mount point is not in /etc/fstab, get previous mount options from /etc/mtab
        if ! grep -q "$mount_point_match_regexp" /etc/fstab; then
            # runtime opts without some automatic kernel/userspace-added defaults
            previous_mount_opts=$(grep "$mount_point_match_regexp" /etc/mtab | head -1 |  awk '{print $4}' \
                        | sed -E "s/(rw|defaults|seclabel|noexec)(,|$)//g;s/,$//")
            [ "$previous_mount_opts" ] && previous_mount_opts+=","
            # In iso9660 filesystems mtab could describe a "blocksize" value, this should be reflected in
            # fstab as "block".  The next variable is to satisfy shellcheck SC2050.
            fs_type="tmpfs"
            if [  "$fs_type" == "iso9660" ] ; then
                previous_mount_opts=$(sed 's/blocksize=/block=/' <<< "$previous_mount_opts")
            fi
            echo "tmpfs /dev/shm tmpfs defaults,${previous_mount_opts}noexec 0 0" >> /etc/fstab
        # If the mount_opt option is not already in the mount point's /etc/fstab entry, add it
        elif ! grep "$mount_point_match_regexp" /etc/fstab | grep -q "noexec"; then
            previous_mount_opts=$(grep "$mount_point_match_regexp" /etc/fstab | awk '{print $4}')
            sed -i "s|\(${mount_point_match_regexp}.*${previous_mount_opts}\)|\1,noexec|" /etc/fstab
        fi

        if mkdir -p "/dev/shm"; then
            if mountpoint -q "/dev/shm"; then
                mount -o remount --target "/dev/shm"
            fi
        fi
    }

    perform_remediation

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | high
Reboot: | false
Strategy: | configure

    - name: 'Add noexec Option to /dev/shm: Check information associated to mountpoint'
      command: findmnt  '/dev/shm'
      register: device_name
      failed_when: device_name.rc > 1
      changed_when: false
      when: not ( ansible_virtualization_type in ["docker", "lxc", "openvz", "podman",
        "container"] )
      tags:
      - NIST-800-53-AC-6
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-MP-7
      - configure_strategy
      - high_disruption
      - low_complexity
      - medium_severity
      - mount_option_dev_shm_noexec
      - no_reboot_needed

    - name: 'Add noexec Option to /dev/shm: Create mount_info dictionary variable'
      set_fact:
        mount_info: '{{ mount_info|default({})|combine({item.0: item.1}) }}'
      with_together:
      - '{{ device_name.stdout_lines[0].split() | list | lower }}'
      - '{{ device_name.stdout_lines[1].split() | list }}'
      when:
      - not ( ansible_virtualization_type in ["docker", "lxc", "openvz", "podman", "container"]
        )
      - device_name.stdout is defined and device_name.stdout_lines is defined
      - (device_name.stdout | length > 0)
      tags:
      - NIST-800-53-AC-6
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-MP-7
      - configure_strategy
      - high_disruption
      - low_complexity
      - medium_severity
      - mount_option_dev_shm_noexec
      - no_reboot_needed

    - name: 'Add noexec Option to /dev/shm: If /dev/shm not mounted, craft mount_info
        manually'
      set_fact:
        mount_info: '{{ mount_info|default({})|combine({item.0: item.1}) }}'
      with_together:
      - - target
        - source
        - fstype
        - options
      - - /dev/shm
        - tmpfs
        - tmpfs
        - defaults
      when:
      - not ( ansible_virtualization_type in ["docker", "lxc", "openvz", "podman", "container"]
        )
      - ("" | length == 0)
      - device_name.stdout is defined and device_name.stdout_lines is defined
      - (device_name.stdout | length == 0)
      tags:
      - NIST-800-53-AC-6
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-MP-7
      - configure_strategy
      - high_disruption
      - low_complexity
      - medium_severity
      - mount_option_dev_shm_noexec
      - no_reboot_needed

    - name: 'Add noexec Option to /dev/shm: Make sure noexec option is part of the to
        /dev/shm options'
      set_fact:
        mount_info: '{{ mount_info | combine( {''options'':''''~mount_info.options~'',noexec''
          }) }}'
      when:
      - not ( ansible_virtualization_type in ["docker", "lxc", "openvz", "podman", "container"]
        )
      - mount_info is defined and "noexec" not in mount_info.options
      tags:
      - NIST-800-53-AC-6
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-MP-7
      - configure_strategy
      - high_disruption
      - low_complexity
      - medium_severity
      - mount_option_dev_shm_noexec
      - no_reboot_needed

    - name: 'Add noexec Option to /dev/shm: Ensure /dev/shm is mounted with noexec option'
      mount:
        path: /dev/shm
        src: '{{ mount_info.source }}'
        opts: '{{ mount_info.options }}'
        state: mounted
        fstype: '{{ mount_info.fstype }}'
      when:
      - not ( ansible_virtualization_type in ["docker", "lxc", "openvz", "podman", "container"]
        )
      - mount_info is defined
      - (device_name.stdout is defined and (device_name.stdout | length > 0)) or ("" |
        length == 0)
      tags:
      - NIST-800-53-AC-6
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-MP-7
      - configure_strategy
      - high_disruption
      - low_complexity
      - medium_severity
      - mount_option_dev_shm_noexec
      - no_reboot_needed

#### Rule Add nosuid Option to /dev/shm [ref]

The `nosuid` mount option can be used to prevent execution of setuid programs in `/dev/shm`. The SUID and SGID permissions should not be required in these world-writable directories. Add the `nosuid` option to the fourth column of `/etc/fstab` for the line which controls mounting of `/dev/shm`.
Rationale: | The presence of SUID and SGID executables should be tightly controlled. Users should not be able to execute SUID or SGID binaries from temporary storage partitions.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_mount_option_dev_shm_nosuid

References:

cis-csc | 11, 13, 14, 3, 8, 9
cobit5 | APO13.01, BAI10.01, BAI10.02, BAI10.03, BAI10.05, DSS05.02, DSS05.05, DSS05.06, DSS06.06
disa | CCI-001764
isa-62443-2009 | 4.3.3.5.1, 4.3.3.5.2, 4.3.3.5.3, 4.3.3.5.4, 4.3.3.5.5, 4.3.3.5.6, 4.3.3.5.7, 4.3.3.5.8, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.1, 4.3.3.7.2, 4.3.3.7.3, 4.3.3.7.4, 4.3.4.3.2, 4.3.4.3.3
isa-62443-2013 | SR 1.1, SR 1.10, SR 1.11, SR 1.12, SR 1.13, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.6, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 2.2, SR 2.3, SR 2.4, SR 2.5, SR 2.6, SR 2.7, SR 7.6
iso27001-2013 | A.11.2.9, A.12.1.2, A.12.5.1, A.12.6.2, A.14.2.2, A.14.2.3, A.14.2.4, A.8.2.1, A.8.2.2, A.8.2.3, A.8.3.1, A.8.3.3, A.9.1.2
nerc-cip | CIP-003-8 R5.1.1, CIP-003-8 R5.3, CIP-004-6 R2.3, CIP-007-3 R2.1, CIP-007-3 R2.2, CIP-007-3 R2.3, CIP-007-3 R5.1, CIP-007-3 R5.1.1, CIP-007-3 R5.1.2
nist | CM-7(a), CM-7(b), CM-6(a), AC-6, AC-6(1), MP-7
nist-csf | PR.IP-1, PR.PT-2, PR.PT-3
os-srg | SRG-OS-000368-GPOS-00154
cis | 1.1.8

Remediation Shell script ⇲

Reboot: | false

    # Remediation is applicable only in certain platforms
    if ! ( [ -f /.dockerenv ] || [ -f /run/.containerenv ] ); then

    function perform_remediation {

        mount_point_match_regexp="$(printf "^[[:space:]]*[^#].*[[:space:]]%s[[:space:]]" /dev/shm)"

        # If the mount point is not in /etc/fstab, get previous mount options from /etc/mtab
        if ! grep -q "$mount_point_match_regexp" /etc/fstab; then
            # runtime opts without some automatic kernel/userspace-added defaults
            previous_mount_opts=$(grep "$mount_point_match_regexp" /etc/mtab | head -1 |  awk '{print $4}' \
                        | sed -E "s/(rw|defaults|seclabel|nosuid)(,|$)//g;s/,$//")
            [ "$previous_mount_opts" ] && previous_mount_opts+=","
            # In iso9660 filesystems mtab could describe a "blocksize" value, this should be reflected in
            # fstab as "block".  The next variable is to satisfy shellcheck SC2050.
            fs_type="tmpfs"
            if [  "$fs_type" == "iso9660" ] ; then
                previous_mount_opts=$(sed 's/blocksize=/block=/' <<< "$previous_mount_opts")
            fi
            echo "tmpfs /dev/shm tmpfs defaults,${previous_mount_opts}nosuid 0 0" >> /etc/fstab
        # If the mount_opt option is not already in the mount point's /etc/fstab entry, add it
        elif ! grep "$mount_point_match_regexp" /etc/fstab | grep -q "nosuid"; then
            previous_mount_opts=$(grep "$mount_point_match_regexp" /etc/fstab | awk '{print $4}')
            sed -i "s|\(${mount_point_match_regexp}.*${previous_mount_opts}\)|\1,nosuid|" /etc/fstab
        fi

        if mkdir -p "/dev/shm"; then
            if mountpoint -q "/dev/shm"; then
                mount -o remount --target "/dev/shm"
            fi
        fi
    }

    perform_remediation

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | high
Reboot: | false
Strategy: | configure

    - name: 'Add nosuid Option to /dev/shm: Check information associated to mountpoint'
      command: findmnt  '/dev/shm'
      register: device_name
      failed_when: device_name.rc > 1
      changed_when: false
      when: not ( ansible_virtualization_type in ["docker", "lxc", "openvz", "podman",
        "container"] )
      tags:
      - NIST-800-53-AC-6
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-MP-7
      - configure_strategy
      - high_disruption
      - low_complexity
      - medium_severity
      - mount_option_dev_shm_nosuid
      - no_reboot_needed

    - name: 'Add nosuid Option to /dev/shm: Create mount_info dictionary variable'
      set_fact:
        mount_info: '{{ mount_info|default({})|combine({item.0: item.1}) }}'
      with_together:
      - '{{ device_name.stdout_lines[0].split() | list | lower }}'
      - '{{ device_name.stdout_lines[1].split() | list }}'
      when:
      - not ( ansible_virtualization_type in ["docker", "lxc", "openvz", "podman", "container"]
        )
      - device_name.stdout is defined and device_name.stdout_lines is defined
      - (device_name.stdout | length > 0)
      tags:
      - NIST-800-53-AC-6
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-MP-7
      - configure_strategy
      - high_disruption
      - low_complexity
      - medium_severity
      - mount_option_dev_shm_nosuid
      - no_reboot_needed

    - name: 'Add nosuid Option to /dev/shm: If /dev/shm not mounted, craft mount_info
        manually'
      set_fact:
        mount_info: '{{ mount_info|default({})|combine({item.0: item.1}) }}'
      with_together:
      - - target
        - source
        - fstype
        - options
      - - /dev/shm
        - tmpfs
        - tmpfs
        - defaults
      when:
      - not ( ansible_virtualization_type in ["docker", "lxc", "openvz", "podman", "container"]
        )
      - ("" | length == 0)
      - device_name.stdout is defined and device_name.stdout_lines is defined
      - (device_name.stdout | length == 0)
      tags:
      - NIST-800-53-AC-6
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-MP-7
      - configure_strategy
      - high_disruption
      - low_complexity
      - medium_severity
      - mount_option_dev_shm_nosuid
      - no_reboot_needed

    - name: 'Add nosuid Option to /dev/shm: Make sure nosuid option is part of the to
        /dev/shm options'
      set_fact:
        mount_info: '{{ mount_info | combine( {''options'':''''~mount_info.options~'',nosuid''
          }) }}'
      when:
      - not ( ansible_virtualization_type in ["docker", "lxc", "openvz", "podman", "container"]
        )
      - mount_info is defined and "nosuid" not in mount_info.options
      tags:
      - NIST-800-53-AC-6
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-MP-7
      - configure_strategy
      - high_disruption
      - low_complexity
      - medium_severity
      - mount_option_dev_shm_nosuid
      - no_reboot_needed

    - name: 'Add nosuid Option to /dev/shm: Ensure /dev/shm is mounted with nosuid option'
      mount:
        path: /dev/shm
        src: '{{ mount_info.source }}'
        opts: '{{ mount_info.options }}'
        state: mounted
        fstype: '{{ mount_info.fstype }}'
      when:
      - not ( ansible_virtualization_type in ["docker", "lxc", "openvz", "podman", "container"]
        )
      - mount_info is defined
      - (device_name.stdout is defined and (device_name.stdout | length > 0)) or ("" |
        length == 0)
      tags:
      - NIST-800-53-AC-6
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-MP-7
      - configure_strategy
      - high_disruption
      - low_complexity
      - medium_severity
      - mount_option_dev_shm_nosuid
      - no_reboot_needed

#### Rule Add nodev Option to /home [ref]

The `nodev` mount option can be used to prevent device files from being created in `/home`. Legitimate character and block devices should exist only in the `/dev` directory on the root partition or within chroot jails built for system services. Add the `nodev` option to the fourth column of `/etc/fstab` for the line which controls mounting of `/home`.
Rationale: | The only legitimate location for device files is the `/dev` directory located on the root partition. The only exception to this is chroot jails.
Severity: | unknown
Rule ID: | xccdf_org.ssgproject.content_rule_mount_option_home_nodev

References:

disa | CCI-001764
os-srg | SRG-OS-000368-GPOS-00154
cis | 1.1.18

Remediation Shell script ⇲

Reboot: | false

    # Remediation is applicable only in certain platforms
    if ! ( [ -f /.dockerenv ] || [ -f /run/.containerenv ] ) && { findmnt --kernel "/home" > /dev/null || findmnt --fstab "/home" > /dev/null; }; then

    function perform_remediation {

            # the mount point /home has to be defined in /etc/fstab
            # before this remediation can be executed. In case it is not defined, the
            # remediation aborts and no changes regarding the mount point are done.
            mount_point_match_regexp="$(printf "^[[:space:]]*[^#].*[[:space:]]%s[[:space:]]" "/home")"

        grep "$mount_point_match_regexp" -q /etc/fstab \
            || { echo "The mount point '/home' is not even in /etc/fstab, so we can't set up mount options" >&2;
                    echo "Not remediating, because there is no record of /home in /etc/fstab" >&2; return 1; }

        mount_point_match_regexp="$(printf "^[[:space:]]*[^#].*[[:space:]]%s[[:space:]]" /home)"

        # If the mount point is not in /etc/fstab, get previous mount options from /etc/mtab
        if ! grep -q "$mount_point_match_regexp" /etc/fstab; then
            # runtime opts without some automatic kernel/userspace-added defaults
            previous_mount_opts=$(grep "$mount_point_match_regexp" /etc/mtab | head -1 |  awk '{print $4}' \
                        | sed -E "s/(rw|defaults|seclabel|nodev)(,|$)//g;s/,$//")
            [ "$previous_mount_opts" ] && previous_mount_opts+=","
            # In iso9660 filesystems mtab could describe a "blocksize" value, this should be reflected in
            # fstab as "block".  The next variable is to satisfy shellcheck SC2050.
            fs_type=""
            if [  "$fs_type" == "iso9660" ] ; then
                previous_mount_opts=$(sed 's/blocksize=/block=/' <<< "$previous_mount_opts")
            fi
            echo " /home  defaults,${previous_mount_opts}nodev 0 0" >> /etc/fstab
        # If the mount_opt option is not already in the mount point's /etc/fstab entry, add it
        elif ! grep "$mount_point_match_regexp" /etc/fstab | grep -q "nodev"; then
            previous_mount_opts=$(grep "$mount_point_match_regexp" /etc/fstab | awk '{print $4}')
            sed -i "s|\(${mount_point_match_regexp}.*${previous_mount_opts}\)|\1,nodev|" /etc/fstab
        fi

        if mkdir -p "/home"; then
            if mountpoint -q "/home"; then
                mount -o remount --target "/home"
            fi
        fi
    }

    perform_remediation

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | high
Reboot: | false
Strategy: | configure

    - name: 'Add nodev Option to /home: Check information associated to mountpoint'
      command: findmnt --fstab '/home'
      register: device_name
      failed_when: device_name.rc > 1
      changed_when: false
      when:
      - not ( ansible_virtualization_type in ["docker", "lxc", "openvz", "podman", "container"]
        )
      - '"/home" in ansible_mounts | map(attribute="mount") | list'
      tags:
      - configure_strategy
      - high_disruption
      - low_complexity
      - mount_option_home_nodev
      - no_reboot_needed
      - unknown_severity

    - name: 'Add nodev Option to /home: Create mount_info dictionary variable'
      set_fact:
        mount_info: '{{ mount_info|default({})|combine({item.0: item.1}) }}'
      with_together:
      - '{{ device_name.stdout_lines[0].split() | list | lower }}'
      - '{{ device_name.stdout_lines[1].split() | list }}'
      when:
      - not ( ansible_virtualization_type in ["docker", "lxc", "openvz", "podman", "container"]
        )
      - '"/home" in ansible_mounts | map(attribute="mount") | list'
      - device_name.stdout is defined and device_name.stdout_lines is defined
      - (device_name.stdout | length > 0)
      tags:
      - configure_strategy
      - high_disruption
      - low_complexity
      - mount_option_home_nodev
      - no_reboot_needed
      - unknown_severity

    - name: 'Add nodev Option to /home: If /home not mounted, craft mount_info manually'
      set_fact:
        mount_info: '{{ mount_info|default({})|combine({item.0: item.1}) }}'
      with_together:
      - - target
        - source
        - fstype
        - options
      - - /home
        - ''
        - ''
        - defaults
      when:
      - not ( ansible_virtualization_type in ["docker", "lxc", "openvz", "podman", "container"]
        )
      - '"/home" in ansible_mounts | map(attribute="mount") | list'
      - ("--fstab" | length == 0)
      - device_name.stdout is defined and device_name.stdout_lines is defined
      - (device_name.stdout | length == 0)
      tags:
      - configure_strategy
      - high_disruption
      - low_complexity
      - mount_option_home_nodev
      - no_reboot_needed
      - unknown_severity

    - name: 'Add nodev Option to /home: Make sure nodev option is part of the to /home
        options'
      set_fact:
        mount_info: '{{ mount_info | combine( {''options'':''''~mount_info.options~'',nodev''
          }) }}'
      when:
      - not ( ansible_virtualization_type in ["docker", "lxc", "openvz", "podman", "container"]
        )
      - '"/home" in ansible_mounts | map(attribute="mount") | list'
      - mount_info is defined and "nodev" not in mount_info.options
      tags:
      - configure_strategy
      - high_disruption
      - low_complexity
      - mount_option_home_nodev
      - no_reboot_needed
      - unknown_severity

    - name: 'Add nodev Option to /home: Ensure /home is mounted with nodev option'
      mount:
        path: /home
        src: '{{ mount_info.source }}'
        opts: '{{ mount_info.options }}'
        state: mounted
        fstype: '{{ mount_info.fstype }}'
      when:
      - not ( ansible_virtualization_type in ["docker", "lxc", "openvz", "podman", "container"]
        )
      - '"/home" in ansible_mounts | map(attribute="mount") | list'
      - mount_info is defined
      - (device_name.stdout is defined and (device_name.stdout | length > 0)) or ("--fstab"
        | length == 0)
      tags:
      - configure_strategy
      - high_disruption
      - low_complexity
      - mount_option_home_nodev
      - no_reboot_needed
      - unknown_severity

#### Rule Add nodev Option to /tmp [ref]

The `nodev` mount option can be used to prevent device files from being created in `/tmp`. Legitimate character and block devices should not exist within temporary directories like `/tmp`. Add the `nodev` option to the fourth column of `/etc/fstab` for the line which controls mounting of `/tmp`.
Rationale: | The only legitimate location for device files is the `/dev` directory located on the root partition. The only exception to this is chroot jails.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_mount_option_tmp_nodev

References:

cis-csc | 11, 13, 14, 3, 8, 9
cobit5 | APO13.01, BAI10.01, BAI10.02, BAI10.03, BAI10.05, DSS05.02, DSS05.05, DSS05.06, DSS06.06
disa | CCI-001764
isa-62443-2009 | 4.3.3.5.1, 4.3.3.5.2, 4.3.3.5.3, 4.3.3.5.4, 4.3.3.5.5, 4.3.3.5.6, 4.3.3.5.7, 4.3.3.5.8, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.1, 4.3.3.7.2, 4.3.3.7.3, 4.3.3.7.4, 4.3.4.3.2, 4.3.4.3.3
isa-62443-2013 | SR 1.1, SR 1.10, SR 1.11, SR 1.12, SR 1.13, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.6, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 2.2, SR 2.3, SR 2.4, SR 2.5, SR 2.6, SR 2.7, SR 7.6
iso27001-2013 | A.11.2.9, A.12.1.2, A.12.5.1, A.12.6.2, A.14.2.2, A.14.2.3, A.14.2.4, A.8.2.1, A.8.2.2, A.8.2.3, A.8.3.1, A.8.3.3, A.9.1.2
nerc-cip | CIP-003-8 R5.1.1, CIP-003-8 R5.3, CIP-004-6 R2.3, CIP-007-3 R2.1, CIP-007-3 R2.2, CIP-007-3 R2.3, CIP-007-3 R5.1, CIP-007-3 R5.1.1, CIP-007-3 R5.1.2
nist | CM-7(a), CM-7(b), CM-6(a), AC-6, AC-6(1), MP-7
nist-csf | PR.IP-1, PR.PT-2, PR.PT-3
os-srg | SRG-OS-000368-GPOS-00154
cis | 1.1.3

Remediation Shell script ⇲

Reboot: | false

    # Remediation is applicable only in certain platforms
    if ! ( [ -f /.dockerenv ] || [ -f /run/.containerenv ] ) && { findmnt --kernel "/tmp" > /dev/null || findmnt --fstab "/tmp" > /dev/null; }; then

    function perform_remediation {

            # the mount point /tmp has to be defined in /etc/fstab
            # before this remediation can be executed. In case it is not defined, the
            # remediation aborts and no changes regarding the mount point are done.
            mount_point_match_regexp="$(printf "^[[:space:]]*[^#].*[[:space:]]%s[[:space:]]" "/tmp")"

        grep "$mount_point_match_regexp" -q /etc/fstab \
            || { echo "The mount point '/tmp' is not even in /etc/fstab, so we can't set up mount options" >&2;
                    echo "Not remediating, because there is no record of /tmp in /etc/fstab" >&2; return 1; }

        mount_point_match_regexp="$(printf "^[[:space:]]*[^#].*[[:space:]]%s[[:space:]]" /tmp)"

        # If the mount point is not in /etc/fstab, get previous mount options from /etc/mtab
        if ! grep -q "$mount_point_match_regexp" /etc/fstab; then
            # runtime opts without some automatic kernel/userspace-added defaults
            previous_mount_opts=$(grep "$mount_point_match_regexp" /etc/mtab | head -1 |  awk '{print $4}' \
                        | sed -E "s/(rw|defaults|seclabel|nodev)(,|$)//g;s/,$//")
            [ "$previous_mount_opts" ] && previous_mount_opts+=","
            # In iso9660 filesystems mtab could describe a "blocksize" value, this should be reflected in
            # fstab as "block".  The next variable is to satisfy shellcheck SC2050.
            fs_type=""
            if [  "$fs_type" == "iso9660" ] ; then
                previous_mount_opts=$(sed 's/blocksize=/block=/' <<< "$previous_mount_opts")
            fi
            echo " /tmp  defaults,${previous_mount_opts}nodev 0 0" >> /etc/fstab
        # If the mount_opt option is not already in the mount point's /etc/fstab entry, add it
        elif ! grep "$mount_point_match_regexp" /etc/fstab | grep -q "nodev"; then
            previous_mount_opts=$(grep "$mount_point_match_regexp" /etc/fstab | awk '{print $4}')
            sed -i "s|\(${mount_point_match_regexp}.*${previous_mount_opts}\)|\1,nodev|" /etc/fstab
        fi

        if mkdir -p "/tmp"; then
            if mountpoint -q "/tmp"; then
                mount -o remount --target "/tmp"
            fi
        fi
    }

    perform_remediation

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | high
Reboot: | false
Strategy: | configure

    - name: 'Add nodev Option to /tmp: Check information associated to mountpoint'
      command: findmnt --fstab '/tmp'
      register: device_name
      failed_when: device_name.rc > 1
      changed_when: false
      when:
      - not ( ansible_virtualization_type in ["docker", "lxc", "openvz", "podman", "container"]
        )
      - '"/tmp" in ansible_mounts | map(attribute="mount") | list'
      tags:
      - NIST-800-53-AC-6
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-MP-7
      - configure_strategy
      - high_disruption
      - low_complexity
      - medium_severity
      - mount_option_tmp_nodev
      - no_reboot_needed

    - name: 'Add nodev Option to /tmp: Create mount_info dictionary variable'
      set_fact:
        mount_info: '{{ mount_info|default({})|combine({item.0: item.1}) }}'
      with_together:
      - '{{ device_name.stdout_lines[0].split() | list | lower }}'
      - '{{ device_name.stdout_lines[1].split() | list }}'
      when:
      - not ( ansible_virtualization_type in ["docker", "lxc", "openvz", "podman", "container"]
        )
      - '"/tmp" in ansible_mounts | map(attribute="mount") | list'
      - device_name.stdout is defined and device_name.stdout_lines is defined
      - (device_name.stdout | length > 0)
      tags:
      - NIST-800-53-AC-6
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-MP-7
      - configure_strategy
      - high_disruption
      - low_complexity
      - medium_severity
      - mount_option_tmp_nodev
      - no_reboot_needed

    - name: 'Add nodev Option to /tmp: If /tmp not mounted, craft mount_info manually'
      set_fact:
        mount_info: '{{ mount_info|default({})|combine({item.0: item.1}) }}'
      with_together:
      - - target
        - source
        - fstype
        - options
      - - /tmp
        - ''
        - ''
        - defaults
      when:
      - not ( ansible_virtualization_type in ["docker", "lxc", "openvz", "podman", "container"]
        )
      - '"/tmp" in ansible_mounts | map(attribute="mount") | list'
      - ("--fstab" | length == 0)
      - device_name.stdout is defined and device_name.stdout_lines is defined
      - (device_name.stdout | length == 0)
      tags:
      - NIST-800-53-AC-6
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-MP-7
      - configure_strategy
      - high_disruption
      - low_complexity
      - medium_severity
      - mount_option_tmp_nodev
      - no_reboot_needed

    - name: 'Add nodev Option to /tmp: Make sure nodev option is part of the to /tmp options'
      set_fact:
        mount_info: '{{ mount_info | combine( {''options'':''''~mount_info.options~'',nodev''
          }) }}'
      when:
      - not ( ansible_virtualization_type in ["docker", "lxc", "openvz", "podman", "container"]
        )
      - '"/tmp" in ansible_mounts | map(attribute="mount") | list'
      - mount_info is defined and "nodev" not in mount_info.options
      tags:
      - NIST-800-53-AC-6
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-MP-7
      - configure_strategy
      - high_disruption
      - low_complexity
      - medium_severity
      - mount_option_tmp_nodev
      - no_reboot_needed

    - name: 'Add nodev Option to /tmp: Ensure /tmp is mounted with nodev option'
      mount:
        path: /tmp
        src: '{{ mount_info.source }}'
        opts: '{{ mount_info.options }}'
        state: mounted
        fstype: '{{ mount_info.fstype }}'
      when:
      - not ( ansible_virtualization_type in ["docker", "lxc", "openvz", "podman", "container"]
        )
      - '"/tmp" in ansible_mounts | map(attribute="mount") | list'
      - mount_info is defined
      - (device_name.stdout is defined and (device_name.stdout | length > 0)) or ("--fstab"
        | length == 0)
      tags:
      - NIST-800-53-AC-6
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-MP-7
      - configure_strategy
      - high_disruption
      - low_complexity
      - medium_severity
      - mount_option_tmp_nodev
      - no_reboot_needed

#### Rule Add noexec Option to /tmp [ref]

The `noexec` mount option can be used to prevent binaries from being executed out of `/tmp`. Add the `noexec` option to the fourth column of `/etc/fstab` for the line which controls mounting of `/tmp`.
Rationale: | Allowing users to execute binaries from world-writable directories such as `/tmp` should never be necessary in normal operation and can expose the system to potential compromise.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_mount_option_tmp_noexec

References:

cis-csc | 11, 13, 14, 3, 8, 9
cobit5 | APO13.01, BAI10.01, BAI10.02, BAI10.03, BAI10.05, DSS05.02, DSS05.05, DSS05.06, DSS06.06
disa | CCI-001764
isa-62443-2009 | 4.3.3.5.1, 4.3.3.5.2, 4.3.3.5.3, 4.3.3.5.4, 4.3.3.5.5, 4.3.3.5.6, 4.3.3.5.7, 4.3.3.5.8, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.1, 4.3.3.7.2, 4.3.3.7.3, 4.3.3.7.4, 4.3.4.3.2, 4.3.4.3.3
isa-62443-2013 | SR 1.1, SR 1.10, SR 1.11, SR 1.12, SR 1.13, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.6, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 2.2, SR 2.3, SR 2.4, SR 2.5, SR 2.6, SR 2.7, SR 7.6
iso27001-2013 | A.11.2.9, A.12.1.2, A.12.5.1, A.12.6.2, A.14.2.2, A.14.2.3, A.14.2.4, A.8.2.1, A.8.2.2, A.8.2.3, A.8.3.1, A.8.3.3, A.9.1.2
nerc-cip | CIP-003-8 R5.1.1, CIP-003-8 R5.3, CIP-004-6 R2.3, CIP-007-3 R2.1, CIP-007-3 R2.2, CIP-007-3 R2.3, CIP-007-3 R5.1, CIP-007-3 R5.1.1, CIP-007-3 R5.1.2
nist | CM-7(a), CM-7(b), CM-6(a), AC-6, AC-6(1), MP-7
nist-csf | PR.IP-1, PR.PT-2, PR.PT-3
os-srg | SRG-OS-000368-GPOS-00154
cis | 1.1.5
anssi | R28

Remediation Shell script ⇲

Reboot: | false

    # Remediation is applicable only in certain platforms
    if ! ( [ -f /.dockerenv ] || [ -f /run/.containerenv ] ) && { findmnt --kernel "/tmp" > /dev/null || findmnt --fstab "/tmp" > /dev/null; }; then

    function perform_remediation {

            # the mount point /tmp has to be defined in /etc/fstab
            # before this remediation can be executed. In case it is not defined, the
            # remediation aborts and no changes regarding the mount point are done.
            mount_point_match_regexp="$(printf "^[[:space:]]*[^#].*[[:space:]]%s[[:space:]]" "/tmp")"

        grep "$mount_point_match_regexp" -q /etc/fstab \
            || { echo "The mount point '/tmp' is not even in /etc/fstab, so we can't set up mount options" >&2;
                    echo "Not remediating, because there is no record of /tmp in /etc/fstab" >&2; return 1; }

        mount_point_match_regexp="$(printf "^[[:space:]]*[^#].*[[:space:]]%s[[:space:]]" /tmp)"

        # If the mount point is not in /etc/fstab, get previous mount options from /etc/mtab
        if ! grep -q "$mount_point_match_regexp" /etc/fstab; then
            # runtime opts without some automatic kernel/userspace-added defaults
            previous_mount_opts=$(grep "$mount_point_match_regexp" /etc/mtab | head -1 |  awk '{print $4}' \
                        | sed -E "s/(rw|defaults|seclabel|noexec)(,|$)//g;s/,$//")
            [ "$previous_mount_opts" ] && previous_mount_opts+=","
            # In iso9660 filesystems mtab could describe a "blocksize" value, this should be reflected in
            # fstab as "block".  The next variable is to satisfy shellcheck SC2050.
            fs_type=""
            if [  "$fs_type" == "iso9660" ] ; then
                previous_mount_opts=$(sed 's/blocksize=/block=/' <<< "$previous_mount_opts")
            fi
            echo " /tmp  defaults,${previous_mount_opts}noexec 0 0" >> /etc/fstab
        # If the mount_opt option is not already in the mount point's /etc/fstab entry, add it
        elif ! grep "$mount_point_match_regexp" /etc/fstab | grep -q "noexec"; then
            previous_mount_opts=$(grep "$mount_point_match_regexp" /etc/fstab | awk '{print $4}')
            sed -i "s|\(${mount_point_match_regexp}.*${previous_mount_opts}\)|\1,noexec|" /etc/fstab
        fi

        if mkdir -p "/tmp"; then
            if mountpoint -q "/tmp"; then
                mount -o remount --target "/tmp"
            fi
        fi
    }

    perform_remediation

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | high
Reboot: | false
Strategy: | configure

    - name: 'Add noexec Option to /tmp: Check information associated to mountpoint'
      command: findmnt --fstab '/tmp'
      register: device_name
      failed_when: device_name.rc > 1
      changed_when: false
      when:
      - not ( ansible_virtualization_type in ["docker", "lxc", "openvz", "podman", "container"]
        )
      - '"/tmp" in ansible_mounts | map(attribute="mount") | list'
      tags:
      - NIST-800-53-AC-6
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-MP-7
      - configure_strategy
      - high_disruption
      - low_complexity
      - medium_severity
      - mount_option_tmp_noexec
      - no_reboot_needed

    - name: 'Add noexec Option to /tmp: Create mount_info dictionary variable'
      set_fact:
        mount_info: '{{ mount_info|default({})|combine({item.0: item.1}) }}'
      with_together:
      - '{{ device_name.stdout_lines[0].split() | list | lower }}'
      - '{{ device_name.stdout_lines[1].split() | list }}'
      when:
      - not ( ansible_virtualization_type in ["docker", "lxc", "openvz", "podman", "container"]
        )
      - '"/tmp" in ansible_mounts | map(attribute="mount") | list'
      - device_name.stdout is defined and device_name.stdout_lines is defined
      - (device_name.stdout | length > 0)
      tags:
      - NIST-800-53-AC-6
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-MP-7
      - configure_strategy
      - high_disruption
      - low_complexity
      - medium_severity
      - mount_option_tmp_noexec
      - no_reboot_needed

    - name: 'Add noexec Option to /tmp: If /tmp not mounted, craft mount_info manually'
      set_fact:
        mount_info: '{{ mount_info|default({})|combine({item.0: item.1}) }}'
      with_together:
      - - target
        - source
        - fstype
        - options
      - - /tmp
        - ''
        - ''
        - defaults
      when:
      - not ( ansible_virtualization_type in ["docker", "lxc", "openvz", "podman", "container"]
        )
      - '"/tmp" in ansible_mounts | map(attribute="mount") | list'
      - ("--fstab" | length == 0)
      - device_name.stdout is defined and device_name.stdout_lines is defined
      - (device_name.stdout | length == 0)
      tags:
      - NIST-800-53-AC-6
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-MP-7
      - configure_strategy
      - high_disruption
      - low_complexity
      - medium_severity
      - mount_option_tmp_noexec
      - no_reboot_needed

    - name: 'Add noexec Option to /tmp: Make sure noexec option is part of the to /tmp
        options'
      set_fact:
        mount_info: '{{ mount_info | combine( {''options'':''''~mount_info.options~'',noexec''
          }) }}'
      when:
      - not ( ansible_virtualization_type in ["docker", "lxc", "openvz", "podman", "container"]
        )
      - '"/tmp" in ansible_mounts | map(attribute="mount") | list'
      - mount_info is defined and "noexec" not in mount_info.options
      tags:
      - NIST-800-53-AC-6
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-MP-7
      - configure_strategy
      - high_disruption
      - low_complexity
      - medium_severity
      - mount_option_tmp_noexec
      - no_reboot_needed

    - name: 'Add noexec Option to /tmp: Ensure /tmp is mounted with noexec option'
      mount:
        path: /tmp
        src: '{{ mount_info.source }}'
        opts: '{{ mount_info.options }}'
        state: mounted
        fstype: '{{ mount_info.fstype }}'
      when:
      - not ( ansible_virtualization_type in ["docker", "lxc", "openvz", "podman", "container"]
        )
      - '"/tmp" in ansible_mounts | map(attribute="mount") | list'
      - mount_info is defined
      - (device_name.stdout is defined and (device_name.stdout | length > 0)) or ("--fstab"
        | length == 0)
      tags:
      - NIST-800-53-AC-6
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-MP-7
      - configure_strategy
      - high_disruption
      - low_complexity
      - medium_severity
      - mount_option_tmp_noexec
      - no_reboot_needed

#### Rule Add nosuid Option to /tmp [ref]

The `nosuid` mount option can be used to prevent execution of setuid programs in `/tmp`. The SUID and SGID permissions should not be required in these world-writable directories. Add the `nosuid` option to the fourth column of `/etc/fstab` for the line which controls mounting of `/tmp`.
Rationale: | The presence of SUID and SGID executables should be tightly controlled. Users should not be able to execute SUID or SGID binaries from temporary storage partitions.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_mount_option_tmp_nosuid

References:

cis-csc | 11, 13, 14, 3, 8, 9
cobit5 | APO13.01, BAI10.01, BAI10.02, BAI10.03, BAI10.05, DSS05.02, DSS05.05, DSS05.06, DSS06.06
disa | CCI-001764
isa-62443-2009 | 4.3.3.5.1, 4.3.3.5.2, 4.3.3.5.3, 4.3.3.5.4, 4.3.3.5.5, 4.3.3.5.6, 4.3.3.5.7, 4.3.3.5.8, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.1, 4.3.3.7.2, 4.3.3.7.3, 4.3.3.7.4, 4.3.4.3.2, 4.3.4.3.3
isa-62443-2013 | SR 1.1, SR 1.10, SR 1.11, SR 1.12, SR 1.13, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.6, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 2.2, SR 2.3, SR 2.4, SR 2.5, SR 2.6, SR 2.7, SR 7.6
iso27001-2013 | A.11.2.9, A.12.1.2, A.12.5.1, A.12.6.2, A.14.2.2, A.14.2.3, A.14.2.4, A.8.2.1, A.8.2.2, A.8.2.3, A.8.3.1, A.8.3.3, A.9.1.2
nerc-cip | CIP-003-8 R5.1.1, CIP-003-8 R5.3, CIP-004-6 R2.3, CIP-007-3 R2.1, CIP-007-3 R2.2, CIP-007-3 R2.3, CIP-007-3 R5.1, CIP-007-3 R5.1.1, CIP-007-3 R5.1.2
nist | CM-7(a), CM-7(b), CM-6(a), AC-6, AC-6(1), MP-7
nist-csf | PR.IP-1, PR.PT-2, PR.PT-3
os-srg | SRG-OS-000368-GPOS-00154
cis | 1.1.4
anssi | R28

Remediation Shell script ⇲

Reboot: | false

    # Remediation is applicable only in certain platforms
    if ! ( [ -f /.dockerenv ] || [ -f /run/.containerenv ] ) && { findmnt --kernel "/tmp" > /dev/null || findmnt --fstab "/tmp" > /dev/null; }; then

    function perform_remediation {

            # the mount point /tmp has to be defined in /etc/fstab
            # before this remediation can be executed. In case it is not defined, the
            # remediation aborts and no changes regarding the mount point are done.
            mount_point_match_regexp="$(printf "^[[:space:]]*[^#].*[[:space:]]%s[[:space:]]" "/tmp")"

        grep "$mount_point_match_regexp" -q /etc/fstab \
            || { echo "The mount point '/tmp' is not even in /etc/fstab, so we can't set up mount options" >&2;
                    echo "Not remediating, because there is no record of /tmp in /etc/fstab" >&2; return 1; }

        mount_point_match_regexp="$(printf "^[[:space:]]*[^#].*[[:space:]]%s[[:space:]]" /tmp)"

        # If the mount point is not in /etc/fstab, get previous mount options from /etc/mtab
        if ! grep -q "$mount_point_match_regexp" /etc/fstab; then
            # runtime opts without some automatic kernel/userspace-added defaults
            previous_mount_opts=$(grep "$mount_point_match_regexp" /etc/mtab | head -1 |  awk '{print $4}' \
                        | sed -E "s/(rw|defaults|seclabel|nosuid)(,|$)//g;s/,$//")
            [ "$previous_mount_opts" ] && previous_mount_opts+=","
            # In iso9660 filesystems mtab could describe a "blocksize" value, this should be reflected in
            # fstab as "block".  The next variable is to satisfy shellcheck SC2050.
            fs_type=""
            if [  "$fs_type" == "iso9660" ] ; then
                previous_mount_opts=$(sed 's/blocksize=/block=/' <<< "$previous_mount_opts")
            fi
            echo " /tmp  defaults,${previous_mount_opts}nosuid 0 0" >> /etc/fstab
        # If the mount_opt option is not already in the mount point's /etc/fstab entry, add it
        elif ! grep "$mount_point_match_regexp" /etc/fstab | grep -q "nosuid"; then
            previous_mount_opts=$(grep "$mount_point_match_regexp" /etc/fstab | awk '{print $4}')
            sed -i "s|\(${mount_point_match_regexp}.*${previous_mount_opts}\)|\1,nosuid|" /etc/fstab
        fi

        if mkdir -p "/tmp"; then
            if mountpoint -q "/tmp"; then
                mount -o remount --target "/tmp"
            fi
        fi
    }

    perform_remediation

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | high
Reboot: | false
Strategy: | configure

    - name: 'Add nosuid Option to /tmp: Check information associated to mountpoint'
      command: findmnt --fstab '/tmp'
      register: device_name
      failed_when: device_name.rc > 1
      changed_when: false
      when:
      - not ( ansible_virtualization_type in ["docker", "lxc", "openvz", "podman", "container"]
        )
      - '"/tmp" in ansible_mounts | map(attribute="mount") | list'
      tags:
      - NIST-800-53-AC-6
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-MP-7
      - configure_strategy
      - high_disruption
      - low_complexity
      - medium_severity
      - mount_option_tmp_nosuid
      - no_reboot_needed

    - name: 'Add nosuid Option to /tmp: Create mount_info dictionary variable'
      set_fact:
        mount_info: '{{ mount_info|default({})|combine({item.0: item.1}) }}'
      with_together:
      - '{{ device_name.stdout_lines[0].split() | list | lower }}'
      - '{{ device_name.stdout_lines[1].split() | list }}'
      when:
      - not ( ansible_virtualization_type in ["docker", "lxc", "openvz", "podman", "container"]
        )
      - '"/tmp" in ansible_mounts | map(attribute="mount") | list'
      - device_name.stdout is defined and device_name.stdout_lines is defined
      - (device_name.stdout | length > 0)
      tags:
      - NIST-800-53-AC-6
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-MP-7
      - configure_strategy
      - high_disruption
      - low_complexity
      - medium_severity
      - mount_option_tmp_nosuid
      - no_reboot_needed

    - name: 'Add nosuid Option to /tmp: If /tmp not mounted, craft mount_info manually'
      set_fact:
        mount_info: '{{ mount_info|default({})|combine({item.0: item.1}) }}'
      with_together:
      - - target
        - source
        - fstype
        - options
      - - /tmp
        - ''
        - ''
        - defaults
      when:
      - not ( ansible_virtualization_type in ["docker", "lxc", "openvz", "podman", "container"]
        )
      - '"/tmp" in ansible_mounts | map(attribute="mount") | list'
      - ("--fstab" | length == 0)
      - device_name.stdout is defined and device_name.stdout_lines is defined
      - (device_name.stdout | length == 0)
      tags:
      - NIST-800-53-AC-6
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-MP-7
      - configure_strategy
      - high_disruption
      - low_complexity
      - medium_severity
      - mount_option_tmp_nosuid
      - no_reboot_needed

    - name: 'Add nosuid Option to /tmp: Make sure nosuid option is part of the to /tmp
        options'
      set_fact:
        mount_info: '{{ mount_info | combine( {''options'':''''~mount_info.options~'',nosuid''
          }) }}'
      when:
      - not ( ansible_virtualization_type in ["docker", "lxc", "openvz", "podman", "container"]
        )
      - '"/tmp" in ansible_mounts | map(attribute="mount") | list'
      - mount_info is defined and "nosuid" not in mount_info.options
      tags:
      - NIST-800-53-AC-6
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-MP-7
      - configure_strategy
      - high_disruption
      - low_complexity
      - medium_severity
      - mount_option_tmp_nosuid
      - no_reboot_needed

    - name: 'Add nosuid Option to /tmp: Ensure /tmp is mounted with nosuid option'
      mount:
        path: /tmp
        src: '{{ mount_info.source }}'
        opts: '{{ mount_info.options }}'
        state: mounted
        fstype: '{{ mount_info.fstype }}'
      when:
      - not ( ansible_virtualization_type in ["docker", "lxc", "openvz", "podman", "container"]
        )
      - '"/tmp" in ansible_mounts | map(attribute="mount") | list'
      - mount_info is defined
      - (device_name.stdout is defined and (device_name.stdout | length > 0)) or ("--fstab"
        | length == 0)
      tags:
      - NIST-800-53-AC-6
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-MP-7
      - configure_strategy
      - high_disruption
      - low_complexity
      - medium_severity
      - mount_option_tmp_nosuid
      - no_reboot_needed

#### Rule Add nodev Option to /var/tmp [ref]

The `nodev` mount option can be used to prevent device files from being created in `/var/tmp`. Legitimate character and block devices should not exist within temporary directories like `/var/tmp`. Add the `nodev` option to the fourth column of `/etc/fstab` for the line which controls mounting of `/var/tmp`.
Rationale: | The only legitimate location for device files is the `/dev` directory located on the root partition. The only exception to this is chroot jails.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_mount_option_var_tmp_nodev

References:

disa | CCI-001764
os-srg | SRG-OS-000368-GPOS-00154
cis | 1.1.12

Remediation Shell script ⇲

Reboot: | false

    # Remediation is applicable only in certain platforms
    if ! ( [ -f /.dockerenv ] || [ -f /run/.containerenv ] ) && { findmnt --kernel "/var/tmp" > /dev/null || findmnt --fstab "/var/tmp" > /dev/null; }; then

    function perform_remediation {

            # the mount point /var/tmp has to be defined in /etc/fstab
            # before this remediation can be executed. In case it is not defined, the
            # remediation aborts and no changes regarding the mount point are done.
            mount_point_match_regexp="$(printf "^[[:space:]]*[^#].*[[:space:]]%s[[:space:]]" "/var/tmp")"

        grep "$mount_point_match_regexp" -q /etc/fstab \
            || { echo "The mount point '/var/tmp' is not even in /etc/fstab, so we can't set up mount options" >&2;
                    echo "Not remediating, because there is no record of /var/tmp in /etc/fstab" >&2; return 1; }

        mount_point_match_regexp="$(printf "^[[:space:]]*[^#].*[[:space:]]%s[[:space:]]" /var/tmp)"

        # If the mount point is not in /etc/fstab, get previous mount options from /etc/mtab
        if ! grep -q "$mount_point_match_regexp" /etc/fstab; then
            # runtime opts without some automatic kernel/userspace-added defaults
            previous_mount_opts=$(grep "$mount_point_match_regexp" /etc/mtab | head -1 |  awk '{print $4}' \
                        | sed -E "s/(rw|defaults|seclabel|nodev)(,|$)//g;s/,$//")
            [ "$previous_mount_opts" ] && previous_mount_opts+=","
            # In iso9660 filesystems mtab could describe a "blocksize" value, this should be reflected in
            # fstab as "block".  The next variable is to satisfy shellcheck SC2050.
            fs_type=""
            if [  "$fs_type" == "iso9660" ] ; then
                previous_mount_opts=$(sed 's/blocksize=/block=/' <<< "$previous_mount_opts")
            fi
            echo " /var/tmp  defaults,${previous_mount_opts}nodev 0 0" >> /etc/fstab
        # If the mount_opt option is not already in the mount point's /etc/fstab entry, add it
        elif ! grep "$mount_point_match_regexp" /etc/fstab | grep -q "nodev"; then
            previous_mount_opts=$(grep "$mount_point_match_regexp" /etc/fstab | awk '{print $4}')
            sed -i "s|\(${mount_point_match_regexp}.*${previous_mount_opts}\)|\1,nodev|" /etc/fstab
        fi

        if mkdir -p "/var/tmp"; then
            if mountpoint -q "/var/tmp"; then
                mount -o remount --target "/var/tmp"
            fi
        fi
    }

    perform_remediation

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | high
Reboot: | false
Strategy: | configure

    - name: 'Add nodev Option to /var/tmp: Check information associated to mountpoint'
      command: findmnt --fstab '/var/tmp'
      register: device_name
      failed_when: device_name.rc > 1
      changed_when: false
      when:
      - not ( ansible_virtualization_type in ["docker", "lxc", "openvz", "podman", "container"]
        )
      - '"/var/tmp" in ansible_mounts | map(attribute="mount") | list'
      tags:
      - configure_strategy
      - high_disruption
      - low_complexity
      - medium_severity
      - mount_option_var_tmp_nodev
      - no_reboot_needed

    - name: 'Add nodev Option to /var/tmp: Create mount_info dictionary variable'
      set_fact:
        mount_info: '{{ mount_info|default({})|combine({item.0: item.1}) }}'
      with_together:
      - '{{ device_name.stdout_lines[0].split() | list | lower }}'
      - '{{ device_name.stdout_lines[1].split() | list }}'
      when:
      - not ( ansible_virtualization_type in ["docker", "lxc", "openvz", "podman", "container"]
        )
      - '"/var/tmp" in ansible_mounts | map(attribute="mount") | list'
      - device_name.stdout is defined and device_name.stdout_lines is defined
      - (device_name.stdout | length > 0)
      tags:
      - configure_strategy
      - high_disruption
      - low_complexity
      - medium_severity
      - mount_option_var_tmp_nodev
      - no_reboot_needed

    - name: 'Add nodev Option to /var/tmp: If /var/tmp not mounted, craft mount_info manually'
      set_fact:
        mount_info: '{{ mount_info|default({})|combine({item.0: item.1}) }}'
      with_together:
      - - target
        - source
        - fstype
        - options
      - - /var/tmp
        - ''
        - ''
        - defaults
      when:
      - not ( ansible_virtualization_type in ["docker", "lxc", "openvz", "podman", "container"]
        )
      - '"/var/tmp" in ansible_mounts | map(attribute="mount") | list'
      - ("--fstab" | length == 0)
      - device_name.stdout is defined and device_name.stdout_lines is defined
      - (device_name.stdout | length == 0)
      tags:
      - configure_strategy
      - high_disruption
      - low_complexity
      - medium_severity
      - mount_option_var_tmp_nodev
      - no_reboot_needed

    - name: 'Add nodev Option to /var/tmp: Make sure nodev option is part of the to /var/tmp
        options'
      set_fact:
        mount_info: '{{ mount_info | combine( {''options'':''''~mount_info.options~'',nodev''
          }) }}'
      when:
      - not ( ansible_virtualization_type in ["docker", "lxc", "openvz", "podman", "container"]
        )
      - '"/var/tmp" in ansible_mounts | map(attribute="mount") | list'
      - mount_info is defined and "nodev" not in mount_info.options
      tags:
      - configure_strategy
      - high_disruption
      - low_complexity
      - medium_severity
      - mount_option_var_tmp_nodev
      - no_reboot_needed

    - name: 'Add nodev Option to /var/tmp: Ensure /var/tmp is mounted with nodev option'
      mount:
        path: /var/tmp
        src: '{{ mount_info.source }}'
        opts: '{{ mount_info.options }}'
        state: mounted
        fstype: '{{ mount_info.fstype }}'
      when:
      - not ( ansible_virtualization_type in ["docker", "lxc", "openvz", "podman", "container"]
        )
      - '"/var/tmp" in ansible_mounts | map(attribute="mount") | list'
      - mount_info is defined
      - (device_name.stdout is defined and (device_name.stdout | length > 0)) or ("--fstab"
        | length == 0)
      tags:
      - configure_strategy
      - high_disruption
      - low_complexity
      - medium_severity
      - mount_option_var_tmp_nodev
      - no_reboot_needed

#### Rule Add noexec Option to /var/tmp [ref]

The `noexec` mount option can be used to prevent binaries from being executed out of `/var/tmp`. Add the `noexec` option to the fourth column of `/etc/fstab` for the line which controls mounting of `/var/tmp`.
Rationale: | Allowing users to execute binaries from world-writable directories such as `/var/tmp` should never be necessary in normal operation and can expose the system to potential compromise.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_mount_option_var_tmp_noexec

References:

disa | CCI-001764
os-srg | SRG-OS-000368-GPOS-00154
cis | 1.1.14
anssi | R28

Remediation Shell script ⇲

Reboot: | false

    # Remediation is applicable only in certain platforms
    if ! ( [ -f /.dockerenv ] || [ -f /run/.containerenv ] ) && { findmnt --kernel "/var/tmp" > /dev/null || findmnt --fstab "/var/tmp" > /dev/null; }; then

    function perform_remediation {

            # the mount point /var/tmp has to be defined in /etc/fstab
            # before this remediation can be executed. In case it is not defined, the
            # remediation aborts and no changes regarding the mount point are done.
            mount_point_match_regexp="$(printf "^[[:space:]]*[^#].*[[:space:]]%s[[:space:]]" "/var/tmp")"

        grep "$mount_point_match_regexp" -q /etc/fstab \
            || { echo "The mount point '/var/tmp' is not even in /etc/fstab, so we can't set up mount options" >&2;
                    echo "Not remediating, because there is no record of /var/tmp in /etc/fstab" >&2; return 1; }

        mount_point_match_regexp="$(printf "^[[:space:]]*[^#].*[[:space:]]%s[[:space:]]" /var/tmp)"

        # If the mount point is not in /etc/fstab, get previous mount options from /etc/mtab
        if ! grep -q "$mount_point_match_regexp" /etc/fstab; then
            # runtime opts without some automatic kernel/userspace-added defaults
            previous_mount_opts=$(grep "$mount_point_match_regexp" /etc/mtab | head -1 |  awk '{print $4}' \
                        | sed -E "s/(rw|defaults|seclabel|noexec)(,|$)//g;s/,$//")
            [ "$previous_mount_opts" ] && previous_mount_opts+=","
            # In iso9660 filesystems mtab could describe a "blocksize" value, this should be reflected in
            # fstab as "block".  The next variable is to satisfy shellcheck SC2050.
            fs_type=""
            if [  "$fs_type" == "iso9660" ] ; then
                previous_mount_opts=$(sed 's/blocksize=/block=/' <<< "$previous_mount_opts")
            fi
            echo " /var/tmp  defaults,${previous_mount_opts}noexec 0 0" >> /etc/fstab
        # If the mount_opt option is not already in the mount point's /etc/fstab entry, add it
        elif ! grep "$mount_point_match_regexp" /etc/fstab | grep -q "noexec"; then
            previous_mount_opts=$(grep "$mount_point_match_regexp" /etc/fstab | awk '{print $4}')
            sed -i "s|\(${mount_point_match_regexp}.*${previous_mount_opts}\)|\1,noexec|" /etc/fstab
        fi

        if mkdir -p "/var/tmp"; then
            if mountpoint -q "/var/tmp"; then
                mount -o remount --target "/var/tmp"
            fi
        fi
    }

    perform_remediation

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | high
Reboot: | false
Strategy: | configure

    - name: 'Add noexec Option to /var/tmp: Check information associated to mountpoint'
      command: findmnt --fstab '/var/tmp'
      register: device_name
      failed_when: device_name.rc > 1
      changed_when: false
      when:
      - not ( ansible_virtualization_type in ["docker", "lxc", "openvz", "podman", "container"]
        )
      - '"/var/tmp" in ansible_mounts | map(attribute="mount") | list'
      tags:
      - configure_strategy
      - high_disruption
      - low_complexity
      - medium_severity
      - mount_option_var_tmp_noexec
      - no_reboot_needed

    - name: 'Add noexec Option to /var/tmp: Create mount_info dictionary variable'
      set_fact:
        mount_info: '{{ mount_info|default({})|combine({item.0: item.1}) }}'
      with_together:
      - '{{ device_name.stdout_lines[0].split() | list | lower }}'
      - '{{ device_name.stdout_lines[1].split() | list }}'
      when:
      - not ( ansible_virtualization_type in ["docker", "lxc", "openvz", "podman", "container"]
        )
      - '"/var/tmp" in ansible_mounts | map(attribute="mount") | list'
      - device_name.stdout is defined and device_name.stdout_lines is defined
      - (device_name.stdout | length > 0)
      tags:
      - configure_strategy
      - high_disruption
      - low_complexity
      - medium_severity
      - mount_option_var_tmp_noexec
      - no_reboot_needed

    - name: 'Add noexec Option to /var/tmp: If /var/tmp not mounted, craft mount_info
        manually'
      set_fact:
        mount_info: '{{ mount_info|default({})|combine({item.0: item.1}) }}'
      with_together:
      - - target
        - source
        - fstype
        - options
      - - /var/tmp
        - ''
        - ''
        - defaults
      when:
      - not ( ansible_virtualization_type in ["docker", "lxc", "openvz", "podman", "container"]
        )
      - '"/var/tmp" in ansible_mounts | map(attribute="mount") | list'
      - ("--fstab" | length == 0)
      - device_name.stdout is defined and device_name.stdout_lines is defined
      - (device_name.stdout | length == 0)
      tags:
      - configure_strategy
      - high_disruption
      - low_complexity
      - medium_severity
      - mount_option_var_tmp_noexec
      - no_reboot_needed

    - name: 'Add noexec Option to /var/tmp: Make sure noexec option is part of the to
        /var/tmp options'
      set_fact:
        mount_info: '{{ mount_info | combine( {''options'':''''~mount_info.options~'',noexec''
          }) }}'
      when:
      - not ( ansible_virtualization_type in ["docker", "lxc", "openvz", "podman", "container"]
        )
      - '"/var/tmp" in ansible_mounts | map(attribute="mount") | list'
      - mount_info is defined and "noexec" not in mount_info.options
      tags:
      - configure_strategy
      - high_disruption
      - low_complexity
      - medium_severity
      - mount_option_var_tmp_noexec
      - no_reboot_needed

    - name: 'Add noexec Option to /var/tmp: Ensure /var/tmp is mounted with noexec option'
      mount:
        path: /var/tmp
        src: '{{ mount_info.source }}'
        opts: '{{ mount_info.options }}'
        state: mounted
        fstype: '{{ mount_info.fstype }}'
      when:
      - not ( ansible_virtualization_type in ["docker", "lxc", "openvz", "podman", "container"]
        )
      - '"/var/tmp" in ansible_mounts | map(attribute="mount") | list'
      - mount_info is defined
      - (device_name.stdout is defined and (device_name.stdout | length > 0)) or ("--fstab"
        | length == 0)
      tags:
      - configure_strategy
      - high_disruption
      - low_complexity
      - medium_severity
      - mount_option_var_tmp_noexec
      - no_reboot_needed

#### Rule Add nosuid Option to /var/tmp [ref]

The `nosuid` mount option can be used to prevent execution of setuid programs in `/var/tmp`. The SUID and SGID permissions should not be required in these world-writable directories. Add the `nosuid` option to the fourth column of `/etc/fstab` for the line which controls mounting of `/var/tmp`.
Rationale: | The presence of SUID and SGID executables should be tightly controlled. Users should not be able to execute SUID or SGID binaries from temporary storage partitions.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_mount_option_var_tmp_nosuid

References:

disa | CCI-001764
os-srg | SRG-OS-000368-GPOS-00154
cis | 1.1.13
anssi | R28

Remediation Shell script ⇲

Reboot: | false

    # Remediation is applicable only in certain platforms
    if ! ( [ -f /.dockerenv ] || [ -f /run/.containerenv ] ) && { findmnt --kernel "/var/tmp" > /dev/null || findmnt --fstab "/var/tmp" > /dev/null; }; then

    function perform_remediation {

            # the mount point /var/tmp has to be defined in /etc/fstab
            # before this remediation can be executed. In case it is not defined, the
            # remediation aborts and no changes regarding the mount point are done.
            mount_point_match_regexp="$(printf "^[[:space:]]*[^#].*[[:space:]]%s[[:space:]]" "/var/tmp")"

        grep "$mount_point_match_regexp" -q /etc/fstab \
            || { echo "The mount point '/var/tmp' is not even in /etc/fstab, so we can't set up mount options" >&2;
                    echo "Not remediating, because there is no record of /var/tmp in /etc/fstab" >&2; return 1; }

        mount_point_match_regexp="$(printf "^[[:space:]]*[^#].*[[:space:]]%s[[:space:]]" /var/tmp)"

        # If the mount point is not in /etc/fstab, get previous mount options from /etc/mtab
        if ! grep -q "$mount_point_match_regexp" /etc/fstab; then
            # runtime opts without some automatic kernel/userspace-added defaults
            previous_mount_opts=$(grep "$mount_point_match_regexp" /etc/mtab | head -1 |  awk '{print $4}' \
                        | sed -E "s/(rw|defaults|seclabel|nosuid)(,|$)//g;s/,$//")
            [ "$previous_mount_opts" ] && previous_mount_opts+=","
            # In iso9660 filesystems mtab could describe a "blocksize" value, this should be reflected in
            # fstab as "block".  The next variable is to satisfy shellcheck SC2050.
            fs_type=""
            if [  "$fs_type" == "iso9660" ] ; then
                previous_mount_opts=$(sed 's/blocksize=/block=/' <<< "$previous_mount_opts")
            fi
            echo " /var/tmp  defaults,${previous_mount_opts}nosuid 0 0" >> /etc/fstab
        # If the mount_opt option is not already in the mount point's /etc/fstab entry, add it
        elif ! grep "$mount_point_match_regexp" /etc/fstab | grep -q "nosuid"; then
            previous_mount_opts=$(grep "$mount_point_match_regexp" /etc/fstab | awk '{print $4}')
            sed -i "s|\(${mount_point_match_regexp}.*${previous_mount_opts}\)|\1,nosuid|" /etc/fstab
        fi

        if mkdir -p "/var/tmp"; then
            if mountpoint -q "/var/tmp"; then
                mount -o remount --target "/var/tmp"
            fi
        fi
    }

    perform_remediation

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | high
Reboot: | false
Strategy: | configure

    - name: 'Add nosuid Option to /var/tmp: Check information associated to mountpoint'
      command: findmnt --fstab '/var/tmp'
      register: device_name
      failed_when: device_name.rc > 1
      changed_when: false
      when:
      - not ( ansible_virtualization_type in ["docker", "lxc", "openvz", "podman", "container"]
        )
      - '"/var/tmp" in ansible_mounts | map(attribute="mount") | list'
      tags:
      - configure_strategy
      - high_disruption
      - low_complexity
      - medium_severity
      - mount_option_var_tmp_nosuid
      - no_reboot_needed

    - name: 'Add nosuid Option to /var/tmp: Create mount_info dictionary variable'
      set_fact:
        mount_info: '{{ mount_info|default({})|combine({item.0: item.1}) }}'
      with_together:
      - '{{ device_name.stdout_lines[0].split() | list | lower }}'
      - '{{ device_name.stdout_lines[1].split() | list }}'
      when:
      - not ( ansible_virtualization_type in ["docker", "lxc", "openvz", "podman", "container"]
        )
      - '"/var/tmp" in ansible_mounts | map(attribute="mount") | list'
      - device_name.stdout is defined and device_name.stdout_lines is defined
      - (device_name.stdout | length > 0)
      tags:
      - configure_strategy
      - high_disruption
      - low_complexity
      - medium_severity
      - mount_option_var_tmp_nosuid
      - no_reboot_needed

    - name: 'Add nosuid Option to /var/tmp: If /var/tmp not mounted, craft mount_info
        manually'
      set_fact:
        mount_info: '{{ mount_info|default({})|combine({item.0: item.1}) }}'
      with_together:
      - - target
        - source
        - fstype
        - options
      - - /var/tmp
        - ''
        - ''
        - defaults
      when:
      - not ( ansible_virtualization_type in ["docker", "lxc", "openvz", "podman", "container"]
        )
      - '"/var/tmp" in ansible_mounts | map(attribute="mount") | list'
      - ("--fstab" | length == 0)
      - device_name.stdout is defined and device_name.stdout_lines is defined
      - (device_name.stdout | length == 0)
      tags:
      - configure_strategy
      - high_disruption
      - low_complexity
      - medium_severity
      - mount_option_var_tmp_nosuid
      - no_reboot_needed

    - name: 'Add nosuid Option to /var/tmp: Make sure nosuid option is part of the to
        /var/tmp options'
      set_fact:
        mount_info: '{{ mount_info | combine( {''options'':''''~mount_info.options~'',nosuid''
          }) }}'
      when:
      - not ( ansible_virtualization_type in ["docker", "lxc", "openvz", "podman", "container"]
        )
      - '"/var/tmp" in ansible_mounts | map(attribute="mount") | list'
      - mount_info is defined and "nosuid" not in mount_info.options
      tags:
      - configure_strategy
      - high_disruption
      - low_complexity
      - medium_severity
      - mount_option_var_tmp_nosuid
      - no_reboot_needed

    - name: 'Add nosuid Option to /var/tmp: Ensure /var/tmp is mounted with nosuid option'
      mount:
        path: /var/tmp
        src: '{{ mount_info.source }}'
        opts: '{{ mount_info.options }}'
        state: mounted
        fstype: '{{ mount_info.fstype }}'
      when:
      - not ( ansible_virtualization_type in ["docker", "lxc", "openvz", "podman", "container"]
        )
      - '"/var/tmp" in ansible_mounts | map(attribute="mount") | list'
      - mount_info is defined
      - (device_name.stdout is defined and (device_name.stdout | length > 0)) or ("--fstab"
        | length == 0)
      tags:
      - configure_strategy
      - high_disruption
      - low_complexity
      - medium_severity
      - mount_option_var_tmp_nosuid
      - no_reboot_needed

Group Restrict Programs from Dangerous Execution Patterns Group contains 2 groups and 3 rules
[ref] The recommendations in this section are designed to ensure that the system's features to protect against potentially dangerous program execution are activated. These protections are applied at the system initialization or kernel level, and defend against certain types of badly-configured or compromised programs.
Group Disable Core Dumps Group contains 2 rules

[ref] A core dump file is the memory image of an executable program when it was terminated by the operating system due to errant behavior. In most cases, only software developers legitimately need to access these files. The core dump files may also contain sensitive information, or unnecessarily occupy large amounts of disk space.
Once a hard limit is set in `/etc/security/limits.conf`, or to a file within the `/etc/security/limits.d/` directory, a user cannot increase that limit within his or her own session. If access to core dumps is required, consider restricting them to only certain users or groups. See the `limits.conf` man page for more information.
The core dumps of setuid programs are further protected. The `sysctl` variable `fs.suid_dumpable` controls whether the kernel allows core dumps from these programs at all. The default value of 0 is recommended.

#### Rule Disable Core Dumps for All Users [ref]

To disable core dumps for all users, add the following line to `/etc/security/limits.conf`, or to a file within the `/etc/security/limits.d/` directory:

    *     hard   core    0

Rationale: | A core dump includes a memory image taken at the time the operating system terminates an application. The memory image could contain sensitive data and is generally useful only for developers trying to debug problems.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_disable_users_coredumps

References:

cis-csc | 1, 12, 13, 15, 16, 2, 7, 8
cobit5 | APO13.01, BAI04.04, DSS01.03, DSS03.05, DSS05.07
disa | CCI-000366
isa-62443-2013 | SR 6.2, SR 7.1, SR 7.2
iso27001-2013 | A.12.1.3, A.17.2.1
nist | CM-6, SC-7(10)
nist-csf | DE.CM-1, PR.DS-4
os-srg | SRG-OS-000480-GPOS-00227
cis | 1.6.4
pcidss4 | 3.3.1.1, 3.3.1, 3.3

Remediation Shell script ⇲

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}\n' 'libpam-runtime' 2>/dev/null | grep -q '^installed'; then

    SECURITY_LIMITS_FILE="/etc/security/limits.conf"

    if grep -qE '^\s*\*\s+hard\s+core' $SECURITY_LIMITS_FILE; then
            sed -ri 's/(hard\s+core\s+)[[:digit:]]+/\1 0/' $SECURITY_LIMITS_FILE
    else
            echo "*     hard   core    0" >> $SECURITY_LIMITS_FILE
    fi

    if ls /etc/security/limits.d/*.conf > /dev/null; then
            sed -ri '/^\s*\*\s+hard\s+core/d' /etc/security/limits.d/*.conf
    fi

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | restrict

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - NIST-800-53-CM-6
      - NIST-800-53-SC-7(10)
      - PCI-DSSv4-3.3
      - PCI-DSSv4-3.3.1
      - PCI-DSSv4-3.3.1.1
      - disable_users_coredumps
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy

    - name: Disable core dumps with limits
      lineinfile:
        dest: /etc/security/limits.conf
        regexp: ^[^#].*core
        line: '*        hard       core      0'
        create: true
      when: '"libpam-runtime" in ansible_facts.packages'
      tags:
      - NIST-800-53-CM-6
      - NIST-800-53-SC-7(10)
      - PCI-DSSv4-3.3
      - PCI-DSSv4-3.3.1
      - PCI-DSSv4-3.3.1.1
      - disable_users_coredumps
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy

#### Rule Disable Core Dumps for SUID programs [ref]

To set the runtime status of the `fs.suid_dumpable` kernel parameter, run the following command:

    $ sudo sysctl -w fs.suid_dumpable=0

To make sure that the setting is persistent, add the following line to a file in the directory `/etc/sysctl.d`:

    fs.suid_dumpable = 0

Rationale: | The core dump of a setuid program is more likely to contain sensitive data, as the program itself runs with greater privileges than the user who initiated execution of the program. Disabling the ability for any setuid program to write a core file decreases the risk of unauthorized access of such data.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_sysctl_fs_suid_dumpable

References:

hipaa | 164.308(a)(1)(ii)(D), 164.308(a)(3), 164.308(a)(4), 164.310(b), 164.310(c), 164.312(a), 164.312(e)
nist | SI-11(a), SI-11(b)
cis | 1.6.4
anssi | R14
pcidss4 | 3.3.1.1, 3.3.1, 3.3

Remediation Shell script ⇲

Complexity: | low
Disruption: | medium
Reboot: | true
Strategy: | disable

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    # Comment out any occurrences of fs.suid_dumpable from /etc/sysctl.d/*.conf files

    for f in /etc/sysctl.d/*.conf /run/sysctl.d/*.conf /usr/local/lib/sysctl.d/*.conf; do

      # skip systemd-sysctl symlink (/etc/sysctl.d/99-sysctl.conf -> /etc/sysctl.conf)
      if [[ "$(readlink -f "$f")" == "/etc/sysctl.conf" ]]; then continue; fi

      matching_list=$(grep -P '^(?!#).*[\s]*fs.suid_dumpable.*$' $f | uniq )
      if ! test -z "$matching_list"; then
        while IFS= read -r entry; do
          escaped_entry=$(sed -e 's|/|\\/|g' <<< "$entry")
          # comment out "fs.suid_dumpable" matches to preserve user data
          sed -i --follow-symlinks "s/^${escaped_entry}$/# &/g" $f
        done <<< "$matching_list"
      fi
    done

    #
    # Set sysctl config file which to save the desired value
    #

    SYSCONFIG_FILE="/etc/sysctl.conf"

    #
    # Set runtime for fs.suid_dumpable
    #
    if [[ "$OSCAP_BOOTC_BUILD" != "YES" ]] ; then
        /sbin/sysctl -q -n -w fs.suid_dumpable="0"
    fi

    #
    # If fs.suid_dumpable present in /etc/sysctl.conf, change value to "0"
    #	else, add "fs.suid_dumpable = 0" to /etc/sysctl.conf
    #

    # Strip any search characters in the key arg so that the key can be replaced without
    # adding any search characters to the config file.
    stripped_key=$(sed 's/[\^=\$,;+]*//g' <<< "^fs.suid_dumpable")

    # shellcheck disable=SC2059
    printf -v formatted_output "%s = %s" "$stripped_key" "0"

    # If the key exists, change it. Otherwise, add it to the config_file.
    # We search for the key string followed by a word boundary (matched by \>),
    # so if we search for 'setting', 'setting2' won't match.
    if LC_ALL=C grep -q -m 1 -i -e "^fs.suid_dumpable\\>" "${SYSCONFIG_FILE}"; then
        escaped_formatted_output=$(sed -e 's|/|\\/|g' <<< "$formatted_output")
        LC_ALL=C sed -i --follow-symlinks "s/^fs.suid_dumpable\\>.*/$escaped_formatted_output/gi" "${SYSCONFIG_FILE}"
    else
        if [[ -s "${SYSCONFIG_FILE}" ]] && [[ -n "$(tail -c 1 -- "${SYSCONFIG_FILE}" || true)" ]]; then
            LC_ALL=C sed -i --follow-symlinks '$a'\\ "${SYSCONFIG_FILE}"
        fi
        printf '%s\n' "$formatted_output" >> "${SYSCONFIG_FILE}"
    fi

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | medium
Reboot: | true
Strategy: | disable

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - NIST-800-53-SI-11(a)
      - NIST-800-53-SI-11(b)
      - PCI-DSSv4-3.3
      - PCI-DSSv4-3.3.1
      - PCI-DSSv4-3.3.1.1
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_fs_suid_dumpable

    - name: List /etc/sysctl.d/*.conf files
      find:
        paths:
        - /etc/sysctl.d/
        - /run/sysctl.d/
        - /usr/local/lib/sysctl.d/
        contains: ^[\s]*fs.suid_dumpable.*$
        patterns: '*.conf'
        file_type: any
      register: find_sysctl_d
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-53-SI-11(a)
      - NIST-800-53-SI-11(b)
      - PCI-DSSv4-3.3
      - PCI-DSSv4-3.3.1
      - PCI-DSSv4-3.3.1.1
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_fs_suid_dumpable

    - name: Comment out any occurrences of fs.suid_dumpable from config files
      replace:
        path: '{{ item.path }}'
        regexp: ^[\s]*fs.suid_dumpable
        replace: '#fs.suid_dumpable'
      loop: '{{ find_sysctl_d.files }}'
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-53-SI-11(a)
      - NIST-800-53-SI-11(b)
      - PCI-DSSv4-3.3
      - PCI-DSSv4-3.3.1
      - PCI-DSSv4-3.3.1.1
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_fs_suid_dumpable

    - name: Ensure sysctl fs.suid_dumpable is set to 0
      sysctl:
        name: fs.suid_dumpable
        value: '0'
        sysctl_file: /etc/sysctl.conf
        state: present
        reload: true
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-53-SI-11(a)
      - NIST-800-53-SI-11(b)
      - PCI-DSSv4-3.3
      - PCI-DSSv4-3.3.1
      - PCI-DSSv4-3.3.1.1
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_fs_suid_dumpable

Group Enable ExecShield Group contains 1 rule

[ref] ExecShield describes kernel features that provide protection against exploitation of memory corruption errors such as buffer overflows. These features include random placement of the stack and other memory regions, prevention of execution in memory that should only hold data, and special handling of text buffers. These protections are enabled by default on 32-bit systems and controlled through `sysctl` variables `kernel.exec-shield` and `kernel.randomize_va_space`. On the latest 64-bit systems, `kernel.exec-shield` cannot be enabled or disabled with `sysctl`.

#### Rule Enable Randomized Layout of Virtual Address Space [ref]

To set the runtime status of the `kernel.randomize_va_space` kernel parameter, run the following command:

    $ sudo sysctl -w kernel.randomize_va_space=2

To make sure that the setting is persistent, add the following line to a file in the directory `/etc/sysctl.d`:

    kernel.randomize_va_space = 2

Rationale: | Address space layout randomization (ASLR) makes it more difficult for an attacker to predict the location of attack code they have introduced into a process's address space during an attempt at exploitation. Additionally, ASLR makes it more difficult for an attacker to know the location of existing code in order to re-purpose it using return oriented programming (ROP) techniques.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_sysctl_kernel_randomize_va_space

References:

cui | 3.1.7
disa | CCI-000366, CCI-002824
hipaa | 164.308(a)(1)(ii)(D), 164.308(a)(3), 164.308(a)(4), 164.310(b), 164.310(c), 164.312(a), 164.312(e)
nerc-cip | CIP-002-5 R1.1, CIP-002-5 R1.2, CIP-003-8 R5.1.1, CIP-003-8 R5.3, CIP-004-6 4.1, CIP-004-6 4.2, CIP-004-6 R2.2.3, CIP-004-6 R2.2.4, CIP-004-6 R2.3, CIP-004-6 R4, CIP-005-6 R1, CIP-005-6 R1.1, CIP-005-6 R1.2, CIP-007-3 R3, CIP-007-3 R3.1, CIP-007-3 R5.1, CIP-007-3 R5.1.2, CIP-007-3 R5.1.3, CIP-007-3 R5.2.1, CIP-007-3 R5.2.3, CIP-007-3 R8.4, CIP-009-6 R.1.1, CIP-009-6 R4
nist | SC-30, SC-30(2), CM-6(a)
pcidss | Req-2.2.1
os-srg | SRG-OS-000433-GPOS-00193, SRG-OS-000480-GPOS-00227
app-srg-ctr | SRG-APP-000450-CTR-001105
stigid | UBTU-20-010448
cis | 1.6.2
anssi | R9
pcidss4 | 3.3.1.1, 3.3.1, 3.3
stigref | SV-238369r853446_rule

Remediation Shell script ⇲

Complexity: | low
Disruption: | medium
Reboot: | true
Strategy: | disable

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    # Comment out any occurrences of kernel.randomize_va_space from /etc/sysctl.d/*.conf files

    for f in /etc/sysctl.d/*.conf /run/sysctl.d/*.conf /usr/local/lib/sysctl.d/*.conf; do

      # skip systemd-sysctl symlink (/etc/sysctl.d/99-sysctl.conf -> /etc/sysctl.conf)
      if [[ "$(readlink -f "$f")" == "/etc/sysctl.conf" ]]; then continue; fi

      matching_list=$(grep -P '^(?!#).*[\s]*kernel.randomize_va_space.*$' $f | uniq )
      if ! test -z "$matching_list"; then
        while IFS= read -r entry; do
          escaped_entry=$(sed -e 's|/|\\/|g' <<< "$entry")
          # comment out "kernel.randomize_va_space" matches to preserve user data
          sed -i --follow-symlinks "s/^${escaped_entry}$/# &/g" $f
        done <<< "$matching_list"
      fi
    done

    #
    # Set sysctl config file which to save the desired value
    #

    SYSCONFIG_FILE="/etc/sysctl.conf"

    #
    # Set runtime for kernel.randomize_va_space
    #
    if [[ "$OSCAP_BOOTC_BUILD" != "YES" ]] ; then
        /sbin/sysctl -q -n -w kernel.randomize_va_space="2"
    fi

    #
    # If kernel.randomize_va_space present in /etc/sysctl.conf, change value to "2"
    #	else, add "kernel.randomize_va_space = 2" to /etc/sysctl.conf
    #

    # Strip any search characters in the key arg so that the key can be replaced without
    # adding any search characters to the config file.
    stripped_key=$(sed 's/[\^=\$,;+]*//g' <<< "^kernel.randomize_va_space")

    # shellcheck disable=SC2059
    printf -v formatted_output "%s = %s" "$stripped_key" "2"

    # If the key exists, change it. Otherwise, add it to the config_file.
    # We search for the key string followed by a word boundary (matched by \>),
    # so if we search for 'setting', 'setting2' won't match.
    if LC_ALL=C grep -q -m 1 -i -e "^kernel.randomize_va_space\\>" "${SYSCONFIG_FILE}"; then
        escaped_formatted_output=$(sed -e 's|/|\\/|g' <<< "$formatted_output")
        LC_ALL=C sed -i --follow-symlinks "s/^kernel.randomize_va_space\\>.*/$escaped_formatted_output/gi" "${SYSCONFIG_FILE}"
    else
        if [[ -s "${SYSCONFIG_FILE}" ]] && [[ -n "$(tail -c 1 -- "${SYSCONFIG_FILE}" || true)" ]]; then
            LC_ALL=C sed -i --follow-symlinks '$a'\\ "${SYSCONFIG_FILE}"
        fi
        printf '%s\n' "$formatted_output" >> "${SYSCONFIG_FILE}"
    fi

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | medium
Reboot: | true
Strategy: | disable

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - DISA-STIG-UBTU-20-010448
      - NIST-800-171-3.1.7
      - NIST-800-53-CM-6(a)
      - NIST-800-53-SC-30
      - NIST-800-53-SC-30(2)
      - PCI-DSS-Req-2.2.1
      - PCI-DSSv4-3.3
      - PCI-DSSv4-3.3.1
      - PCI-DSSv4-3.3.1.1
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_kernel_randomize_va_space

    - name: List /etc/sysctl.d/*.conf files
      find:
        paths:
        - /etc/sysctl.d/
        - /run/sysctl.d/
        - /usr/local/lib/sysctl.d/
        contains: ^[\s]*kernel.randomize_va_space.*$
        patterns: '*.conf'
        file_type: any
      register: find_sysctl_d
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - DISA-STIG-UBTU-20-010448
      - NIST-800-171-3.1.7
      - NIST-800-53-CM-6(a)
      - NIST-800-53-SC-30
      - NIST-800-53-SC-30(2)
      - PCI-DSS-Req-2.2.1
      - PCI-DSSv4-3.3
      - PCI-DSSv4-3.3.1
      - PCI-DSSv4-3.3.1.1
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_kernel_randomize_va_space

    - name: Comment out any occurrences of kernel.randomize_va_space from config files
      replace:
        path: '{{ item.path }}'
        regexp: ^[\s]*kernel.randomize_va_space
        replace: '#kernel.randomize_va_space'
      loop: '{{ find_sysctl_d.files }}'
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - DISA-STIG-UBTU-20-010448
      - NIST-800-171-3.1.7
      - NIST-800-53-CM-6(a)
      - NIST-800-53-SC-30
      - NIST-800-53-SC-30(2)
      - PCI-DSS-Req-2.2.1
      - PCI-DSSv4-3.3
      - PCI-DSSv4-3.3.1
      - PCI-DSSv4-3.3.1.1
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_kernel_randomize_va_space

    - name: Ensure sysctl kernel.randomize_va_space is set to 2
      sysctl:
        name: kernel.randomize_va_space
        value: '2'
        sysctl_file: /etc/sysctl.conf
        state: present
        reload: true
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - DISA-STIG-UBTU-20-010448
      - NIST-800-171-3.1.7
      - NIST-800-53-CM-6(a)
      - NIST-800-53-SC-30
      - NIST-800-53-SC-30(2)
      - PCI-DSS-Req-2.2.1
      - PCI-DSSv4-3.3
      - PCI-DSSv4-3.3.1
      - PCI-DSSv4-3.3.1.1
      - disable_strategy
      - low_complexity
      - medium_disruption
      - medium_severity
      - reboot_required
      - sysctl_kernel_randomize_va_space

Group Services Group contains 42 groups and 84 rules

[ref] The best protection against vulnerable software is running less software. This section describes how to review the software which Ubuntu 20.04 installs on a system and disable software which is not needed. It then enumerates the software packages installed on a default Ubuntu 20.04 system and provides guidance about which ones can be safely disabled.
Ubuntu 20.04 provides a convenient minimal install option that essentially installs the bare necessities for a functional system. When building Ubuntu 20.04 systems, it is highly recommended to select the minimal packages and then build up the system from there.

Group Avahi Server Group contains 1 group and 2 rules
[ref] The Avahi daemon implements the DNS Service Discovery and Multicast DNS protocols, which provide service and host discovery on a network. It allows a system to automatically identify resources on the network, such as printers or web servers. This capability is also known as mDNSresponder and is a major part of Zeroconf networking.
Group Disable Avahi Server if Possible Group contains 2 rules
[ref] Because the Avahi daemon service keeps an open network port, it is subject to network attacks. Disabling it can reduce the system's vulnerability to such attacks.

#### Rule Uninstall avahi Server Package [ref]

If the system does not need to have an Avahi server which implements the DNS Service Discovery and Multicast DNS protocols, the avahi-autoipd and avahi packages can be uninstalled.
Rationale: | Automatic discovery of network services is not normally required for system functionality. It is recommended to remove this package to reduce the potential attack surface.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_package_avahi_removed

References:

cis-csc | 11, 14, 3, 9
cobit5 | BAI10.01, BAI10.02, BAI10.03, BAI10.05, DSS05.02, DSS05.05, DSS06.06
disa | CCI-000366
isa-62443-2009 | 4.3.3.5.1, 4.3.3.5.2, 4.3.3.5.3, 4.3.3.5.4, 4.3.3.5.5, 4.3.3.5.6, 4.3.3.5.7, 4.3.3.5.8, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.1, 4.3.3.7.2, 4.3.3.7.3, 4.3.3.7.4, 4.3.4.3.2, 4.3.4.3.3
isa-62443-2013 | SR 1.1, SR 1.10, SR 1.11, SR 1.12, SR 1.13, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.6, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 2.2, SR 2.3, SR 2.4, SR 2.5, SR 2.6, SR 2.7, SR 7.6
iso27001-2013 | A.12.1.2, A.12.5.1, A.12.6.2, A.14.2.2, A.14.2.3, A.14.2.4, A.9.1.2
nist | CM-7(a), CM-7(b), CM-6(a)
nist-csf | PR.IP-1, PR.PT-3
cis | 2.2.3

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    # CAUTION: This remediation script will remove avahi-daemon
    #	   from the system, and may remove any packages
    #	   that depend on avahi-daemon. Execute this
    #	   remediation AFTER testing on a non-production
    #	   system!

    DEBIAN_FRONTEND=noninteractive apt-get remove -y "avahi-daemon"

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    - name: Ensure avahi-daemon is removed
      package:
        name: avahi-daemon
        state: absent
      tags:
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - disable_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - package_avahi_removed

Remediation Puppet snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    include remove_avahi-daemon

    class remove_avahi-daemon {
      package { 'avahi-daemon':
        ensure => 'purged',
      }
    }

#### Rule Disable Avahi Server Software [ref]

The `avahi-daemon` service can be disabled with the following command:

    $ sudo systemctl mask --now avahi-daemon.service

Rationale: | Because the Avahi daemon service keeps an open network port, it is subject to network attacks. Its functionality is convenient but is only appropriate if the local network can be trusted.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_service_avahi-daemon_disabled

References:

cis-csc | 11, 14, 3, 9
cobit5 | BAI10.01, BAI10.02, BAI10.03, BAI10.05, DSS05.02, DSS05.05, DSS06.06
disa | CCI-000366
isa-62443-2009 | 4.3.3.5.1, 4.3.3.5.2, 4.3.3.5.3, 4.3.3.5.4, 4.3.3.5.5, 4.3.3.5.6, 4.3.3.5.7, 4.3.3.5.8, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.1, 4.3.3.7.2, 4.3.3.7.3, 4.3.3.7.4, 4.3.4.3.2, 4.3.4.3.3
isa-62443-2013 | SR 1.1, SR 1.10, SR 1.11, SR 1.12, SR 1.13, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.6, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 2.2, SR 2.3, SR 2.4, SR 2.5, SR 2.6, SR 2.7, SR 7.6
iso27001-2013 | A.12.1.2, A.12.5.1, A.12.6.2, A.14.2.2, A.14.2.3, A.14.2.4, A.9.1.2
nist | CM-7(a), CM-7(b), CM-6(a)
nist-csf | PR.IP-1, PR.PT-3
cis | 2.2.3
pcidss4 | 2.2.4, 2.2

Remediation Kubernetes snippet ⇲

Complexity: | low
Disruption: | medium
Reboot: | true
Strategy: | disable

    apiVersion: machineconfiguration.openshift.io/v1
    kind: MachineConfig
    spec:
      config:
        ignition:
          version: 3.1.0
        systemd:
          units:
          - name: avahi-daemon.service
            enabled: false
            mask: true
          - name: avahi-daemon.socket
            enabled: false
            mask: true

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    # Remediation is applicable only in certain platforms
    if ( dpkg-query --show --showformat='${db:Status-Status}\n' 'avahi-daemon' 2>/dev/null | grep -q '^installed' && dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed ); then

    SYSTEMCTL_EXEC='/usr/bin/systemctl'
    if [[ $("$SYSTEMCTL_EXEC" is-system-running) != "offline" ]]; then
      "$SYSTEMCTL_EXEC" stop 'avahi-daemon.service'
    fi
    "$SYSTEMCTL_EXEC" disable 'avahi-daemon.service'
    "$SYSTEMCTL_EXEC" mask 'avahi-daemon.service'
    # Disable socket activation if we have a unit file for it
    if "$SYSTEMCTL_EXEC" -q list-unit-files avahi-daemon.socket; then
        if [[ $("$SYSTEMCTL_EXEC" is-system-running) != "offline" ]]; then
          "$SYSTEMCTL_EXEC" stop 'avahi-daemon.socket'
        fi
        "$SYSTEMCTL_EXEC" mask 'avahi-daemon.socket'
    fi
    # The service may not be running because it has been started and failed,
    # so let's reset the state so OVAL checks pass.
    # Service should be 'inactive', not 'failed' after reboot though.
    "$SYSTEMCTL_EXEC" reset-failed 'avahi-daemon.service' || true

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation OSBuild Blueprint snippet ⇲

    [customizations.services]
    masked = ["avahi-daemon"]

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.4
      - disable_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - service_avahi-daemon_disabled

    - name: Disable Avahi Server Software - Collect systemd Services Present in the System
      ansible.builtin.command: systemctl -q list-unit-files --type service
      register: service_exists
      changed_when: false
      failed_when: service_exists.rc not in [0, 1]
      check_mode: false
      when: ( "avahi-daemon" in ansible_facts.packages and "linux-base" in ansible_facts.packages
        )
      tags:
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.4
      - disable_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - service_avahi-daemon_disabled

    - name: Disable Avahi Server Software - Ensure avahi-daemon.service is Masked
      ansible.builtin.systemd:
        name: avahi-daemon.service
        state: stopped
        enabled: false
        masked: true
      when:
      - ( "avahi-daemon" in ansible_facts.packages and "linux-base" in ansible_facts.packages
        )
      - service_exists.stdout_lines is search("avahi-daemon.service", multiline=True)
      tags:
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.4
      - disable_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - service_avahi-daemon_disabled

    - name: Unit Socket Exists - avahi-daemon.socket
      ansible.builtin.command: systemctl -q list-unit-files avahi-daemon.socket
      register: socket_file_exists
      changed_when: false
      failed_when: socket_file_exists.rc not in [0, 1]
      check_mode: false
      when: ( "avahi-daemon" in ansible_facts.packages and "linux-base" in ansible_facts.packages
        )
      tags:
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.4
      - disable_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - service_avahi-daemon_disabled

    - name: Disable Avahi Server Software - Disable Socket avahi-daemon
      ansible.builtin.systemd:
        name: avahi-daemon.socket
        enabled: false
        state: stopped
        masked: true
      when:
      - ( "avahi-daemon" in ansible_facts.packages and "linux-base" in ansible_facts.packages
        )
      - socket_file_exists.stdout_lines is search("avahi-daemon.socket", multiline=True)
      tags:
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.4
      - disable_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - service_avahi-daemon_disabled

Remediation Puppet snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | enable

    include disable_avahi-daemon

    class disable_avahi-daemon {
      service {'avahi-daemon':
        enable => false,
        ensure => 'stopped',
      }
    }

Group Cron and At Daemons Group contains 1 group and 25 rules
[ref] The cron and at services are used to allow commands to be executed at a later time. The cron service is required by almost all systems to perform necessary maintenance tasks, while at may or may not be required on a given system. Both daemons should be configured defensively.
Group Restrict at and cron to Authorized Users if Necessary Group contains 6 rules

[ref] The `/etc/cron.allow` and `/etc/at.allow` files contain lists of users who are allowed to use `cron` and at to delay execution of processes. If these files exist and if the corresponding files `/etc/cron.deny` and `/etc/at.deny` do not exist, then only users listed in the relevant allow files can run the crontab and `at` commands to submit jobs to be run at scheduled intervals. On many systems, only the system administrator needs the ability to schedule jobs. Note that even if a given user is not listed in `cron.allow`, cron jobs can still be run as that user. The `cron.allow` file controls only administrative access to the crontab command for scheduling and modifying cron jobs.
To restrict `at` and `cron` to only authorized users:

- Remove the `cron.deny` file:

      $ sudo rm /etc/cron.deny

- Edit `/etc/cron.allow`, adding one line for each user allowed to use the crontab command to create cron jobs.
- Remove the `at.deny` file:

      $ sudo rm /etc/at.deny

- Edit `/etc/at.allow`, adding one line for each user allowed to use the at command to create at jobs.

#### Rule Verify Group Who Owns /etc/at.allow file [ref]

If `/etc/at.allow` exists, it must be group-owned by `root`. To properly set the group owner of `/etc/at.allow`, run the command:

    $ sudo chgrp root /etc/at.allow

Rationale: | If the owner of the at.allow file is not set to root, the possibility exists for an unauthorized user to view or edit sensitive information.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_file_groupowner_at_allow

References:

cis | 5.1.9
pcidss4 | 2.2.6, 2.2

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    chgrp 0 /etc/at.allow

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_groupowner_at_allow
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Test for existence /etc/at.allow
      stat:
        path: /etc/at.allow
      register: file_exists
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_groupowner_at_allow
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Ensure group owner 0 on /etc/at.allow
      file:
        path: /etc/at.allow
        group: '0'
      when:
      - '"linux-base" in ansible_facts.packages'
      - file_exists.stat is defined and file_exists.stat.exists
      tags:
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_groupowner_at_allow
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

#### Rule Verify Group Who Owns /etc/cron.allow file [ref]

If `/etc/cron.allow` exists, it must be group-owned by `crontab`. To properly set the group owner of `/etc/cron.allow`, run the command:

    $ sudo chgrp crontab /etc/cron.allow

Rationale: | If the owner of the cron.allow file is not set to crontab, the possibility exists for an unauthorized user to view or edit sensitive information.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_file_groupowner_cron_allow

References:

cis-csc | 12, 13, 14, 15, 16, 18, 3, 5
cobit5 | APO01.06, DSS05.04, DSS05.07, DSS06.02
disa | CCI-000366
isa-62443-2009 | 4.3.3.7.3
isa-62443-2013 | SR 2.1, SR 5.2
iso27001-2013 | A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.13.1.1, A.13.1.3, A.13.2.1, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, A.6.1.2, A.7.1.1, A.7.1.2, A.7.3.1, A.8.2.2, A.8.2.3, A.9.1.1, A.9.1.2, A.9.2.3, A.9.4.1, A.9.4.4, A.9.4.5
nist | CM-6(a), AC-6(1)
nist-csf | PR.AC-4, PR.DS-5
os-srg | SRG-OS-000480-GPOS-00227
cis | 5.1.8
pcidss4 | 2.2.6, 2.2

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    chgrp crontab /etc/cron.allow

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_groupowner_cron_allow
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Test for existence /etc/cron.allow
      stat:
        path: /etc/cron.allow
      register: file_exists
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_groupowner_cron_allow
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Ensure group owner crontab on /etc/cron.allow
      file:
        path: /etc/cron.allow
        group: crontab
      when:
      - '"linux-base" in ansible_facts.packages'
      - file_exists.stat is defined and file_exists.stat.exists
      tags:
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_groupowner_cron_allow
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

#### Rule Verify User Who Owns /etc/at.allow file [ref]

If `/etc/at.allow` exists, it must be owned by `root`. To properly set the owner of `/etc/at.allow`, run the command:

    $ sudo chown root /etc/at.allow

Rationale: | If the owner of the at.allow file is not set to root, the possibility exists for an unauthorized user to view or edit sensitive information.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_file_owner_at_allow

References:

cis | 5.1.9
pcidss4 | 2.2.6, 2.2

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    chown 0 /etc/at.allow

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_owner_at_allow
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Test for existence /etc/at.allow
      stat:
        path: /etc/at.allow
      register: file_exists
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_owner_at_allow
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Ensure owner 0 on /etc/at.allow
      file:
        path: /etc/at.allow
        owner: '0'
      when:
      - '"linux-base" in ansible_facts.packages'
      - file_exists.stat is defined and file_exists.stat.exists
      tags:
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_owner_at_allow
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

#### Rule Verify User Who Owns /etc/cron.allow file [ref]

If `/etc/cron.allow` exists, it must be owned by `root`. To properly set the owner of `/etc/cron.allow`, run the command:

    $ sudo chown root /etc/cron.allow

Rationale: | If the owner of the cron.allow file is not set to root, the possibility exists for an unauthorized user to view or edit sensitive information.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_file_owner_cron_allow

References:

cis-csc | 12, 13, 14, 15, 16, 18, 3, 5
cobit5 | APO01.06, DSS05.04, DSS05.07, DSS06.02
disa | CCI-000366
isa-62443-2009 | 4.3.3.7.3
isa-62443-2013 | SR 2.1, SR 5.2
iso27001-2013 | A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.13.1.1, A.13.1.3, A.13.2.1, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, A.6.1.2, A.7.1.1, A.7.1.2, A.7.3.1, A.8.2.2, A.8.2.3, A.9.1.1, A.9.1.2, A.9.2.3, A.9.4.1, A.9.4.4, A.9.4.5
nist | CM-6(a), AC-6(1)
nist-csf | PR.AC-4, PR.DS-5
os-srg | SRG-OS-000480-GPOS-00227
cis | 5.1.8
pcidss4 | 2.2.6, 2.2

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    chown 0 /etc/cron.allow

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_owner_cron_allow
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Test for existence /etc/cron.allow
      stat:
        path: /etc/cron.allow
      register: file_exists
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_owner_cron_allow
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Ensure owner 0 on /etc/cron.allow
      file:
        path: /etc/cron.allow
        owner: '0'
      when:
      - '"linux-base" in ansible_facts.packages'
      - file_exists.stat is defined and file_exists.stat.exists
      tags:
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_owner_cron_allow
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

#### Rule Verify Permissions on /etc/at.allow file [ref]

If `/etc/at.allow` exists, it must have permissions `0640` or more restrictive. To properly set the permissions of `/etc/at.allow`, run the command:

    $ sudo chmod 0640 /etc/at.allow

Rationale: | If the permissions of the at.allow file are not set to 0640 or more restrictive, the possibility exists for an unauthorized user to view or edit sensitive information.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_file_permissions_at_allow

References:

cis | 5.1.9
pcidss4 | 2.2.6, 2.2

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    chmod u-xs,g-xws,o-xwrt /etc/at.allow

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_permissions_at_allow
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Test for existence /etc/at.allow
      stat:
        path: /etc/at.allow
      register: file_exists
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_permissions_at_allow
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Ensure permission u-xs,g-xws,o-xwrt on /etc/at.allow
      file:
        path: /etc/at.allow
        mode: u-xs,g-xws,o-xwrt
      when:
      - '"linux-base" in ansible_facts.packages'
      - file_exists.stat is defined and file_exists.stat.exists
      tags:
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_permissions_at_allow
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

#### Rule Verify Permissions on /etc/cron.allow file [ref]

If `/etc/cron.allow` exists, it must have permissions `0640` or more restrictive. To properly set the permissions of `/etc/cron.allow`, run the command:

    $ sudo chmod 0640 /etc/cron.allow

Rationale: | If the permissions of the cron.allow file are not set to 0640 or more restrictive, the possibility exists for an unauthorized user to view or edit sensitive information.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_file_permissions_cron_allow

References:

disa | CCI-000366
os-srg | SRG-OS-000480-GPOS-00227
cis | 5.1.8
pcidss4 | 2.2.6, 2.2

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    chmod u-xs,g-xws,o-xwrt /etc/cron.allow

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_permissions_cron_allow
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Test for existence /etc/cron.allow
      stat:
        path: /etc/cron.allow
      register: file_exists
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_permissions_cron_allow
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Ensure permission u-xs,g-xws,o-xwrt on /etc/cron.allow
      file:
        path: /etc/cron.allow
        mode: u-xs,g-xws,o-xwrt
      when:
      - '"linux-base" in ansible_facts.packages'
      - file_exists.stat is defined and file_exists.stat.exists
      tags:
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_permissions_cron_allow
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

#### Rule Enable cron Service [ref]

The `crond` service is used to execute commands at preconfigured times. It is required by almost all systems to perform necessary maintenance tasks, such as notifying root of system activity. The `cron` service can be enabled with the following command:

    $ sudo systemctl enable cron.service

Rationale: | Due to its usage for maintenance and security-supporting tasks, enabling the cron daemon is essential.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_service_cron_enabled

References:

cis-csc | 11, 14, 3, 9
cobit5 | BAI10.01, BAI10.02, BAI10.03, BAI10.05, DSS05.02, DSS05.05, DSS06.06
hipaa | 164.308(a)(4)(i), 164.308(b)(1), 164.308(b)(3), 164.310(b), 164.312(e)(1), 164.312(e)(2)(ii)
isa-62443-2009 | 4.3.3.5.1, 4.3.3.5.2, 4.3.3.5.3, 4.3.3.5.4, 4.3.3.5.5, 4.3.3.5.6, 4.3.3.5.7, 4.3.3.5.8, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.1, 4.3.3.7.2, 4.3.3.7.3, 4.3.3.7.4, 4.3.4.3.2, 4.3.4.3.3
isa-62443-2013 | SR 1.1, SR 1.10, SR 1.11, SR 1.12, SR 1.13, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.6, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 2.2, SR 2.3, SR 2.4, SR 2.5, SR 2.6, SR 2.7, SR 7.6
iso27001-2013 | A.12.1.2, A.12.5.1, A.12.6.2, A.14.2.2, A.14.2.3, A.14.2.4, A.9.1.2
nist | CM-6(a)
nist-csf | PR.IP-1, PR.PT-3
cis | 5.1.1

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | enable

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    SYSTEMCTL_EXEC='/usr/bin/systemctl'
    "$SYSTEMCTL_EXEC" unmask 'cron.service'
    if [[ $("$SYSTEMCTL_EXEC" is-system-running) != "offline" ]]; then
      "$SYSTEMCTL_EXEC" start 'cron.service'
    fi
    "$SYSTEMCTL_EXEC" enable 'cron.service'

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation OSBuild Blueprint snippet ⇲

    [customizations.services]
    enabled = ["cron"]

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | enable

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - NIST-800-53-CM-6(a)
      - enable_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - service_cron_enabled

    - name: Enable cron Service - Enable service cron
      block:

      - name: Gather the package facts
        package_facts:
          manager: auto

      - name: Enable cron Service - Enable Service cron
        ansible.builtin.systemd:
          name: cron
          enabled: true
          state: started
          masked: false
        when:
        - '"cron" in ansible_facts.packages'
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-53-CM-6(a)
      - enable_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - service_cron_enabled

Remediation Puppet snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | enable

    include enable_cron

    class enable_cron {
      service {'cron':
        enable => true,
        ensure => 'running',
      }
    }

#### Rule Verify Group Who Owns cron.d [ref]

To properly set the group owner of `/etc/cron.d`, run the command:

    $ sudo chgrp root /etc/cron.d

Rationale: | Service configuration files enable or disable features of their respective services that if configured incorrectly can lead to insecure and vulnerable configurations. Therefore, service configuration files should be owned by the correct group to prevent unauthorized changes.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_file_groupowner_cron_d

References:

cis-csc | 12, 13, 14, 15, 16, 18, 3, 5
cobit5 | APO01.06, DSS05.04, DSS05.07, DSS06.02
disa | CCI-000366
isa-62443-2009 | 4.3.3.7.3
isa-62443-2013 | SR 2.1, SR 5.2
iso27001-2013 | A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.13.1.1, A.13.1.3, A.13.2.1, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, A.6.1.2, A.7.1.1, A.7.1.2, A.7.3.1, A.8.2.2, A.8.2.3, A.9.1.1, A.9.1.2, A.9.2.3, A.9.4.1, A.9.4.4, A.9.4.5
nist | CM-6(a), AC-6(1)
nist-csf | PR.AC-4, PR.DS-5
os-srg | SRG-OS-000480-GPOS-00227
cis | 5.1.7
pcidss4 | 2.2.6, 2.2

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    find -H /etc/cron.d/ -maxdepth 1 -type d -exec chgrp -L 0 {} \;

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_groupowner_cron_d
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Ensure group owner on /etc/cron.d/
      file:
        path: /etc/cron.d/
        state: directory
        group: '0'
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_groupowner_cron_d
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

#### Rule Verify Group Who Owns cron.daily [ref]

To properly set the group owner of `/etc/cron.daily`, run the command:

    $ sudo chgrp root /etc/cron.daily

Rationale: | Service configuration files enable or disable features of their respective services that if configured incorrectly can lead to insecure and vulnerable configurations. Therefore, service configuration files should be owned by the correct group to prevent unauthorized changes.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_file_groupowner_cron_daily

References:

cis-csc | 12, 13, 14, 15, 16, 18, 3, 5
cobit5 | APO01.06, DSS05.04, DSS05.07, DSS06.02
disa | CCI-000366
isa-62443-2009 | 4.3.3.7.3
isa-62443-2013 | SR 2.1, SR 5.2
iso27001-2013 | A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.13.1.1, A.13.1.3, A.13.2.1, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, A.6.1.2, A.7.1.1, A.7.1.2, A.7.3.1, A.8.2.2, A.8.2.3, A.9.1.1, A.9.1.2, A.9.2.3, A.9.4.1, A.9.4.4, A.9.4.5
nist | CM-6(a), AC-6(1)
nist-csf | PR.AC-4, PR.DS-5
os-srg | SRG-OS-000480-GPOS-00227
cis | 5.1.4
pcidss4 | 2.2.6, 2.2

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    find -H /etc/cron.daily/ -maxdepth 1 -type d -exec chgrp -L 0 {} \;

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_groupowner_cron_daily
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Ensure group owner on /etc/cron.daily/
      file:
        path: /etc/cron.daily/
        state: directory
        group: '0'
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_groupowner_cron_daily
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

#### Rule Verify Group Who Owns cron.hourly [ref]

To properly set the group owner of `/etc/cron.hourly`, run the command:

    $ sudo chgrp root /etc/cron.hourly

Rationale: | Service configuration files enable or disable features of their respective services that if configured incorrectly can lead to insecure and vulnerable configurations. Therefore, service configuration files should be owned by the correct group to prevent unauthorized changes.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_file_groupowner_cron_hourly

References:

cis-csc | 12, 13, 14, 15, 16, 18, 3, 5
cobit5 | APO01.06, DSS05.04, DSS05.07, DSS06.02
disa | CCI-000366
isa-62443-2009 | 4.3.3.7.3
isa-62443-2013 | SR 2.1, SR 5.2
iso27001-2013 | A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.13.1.1, A.13.1.3, A.13.2.1, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, A.6.1.2, A.7.1.1, A.7.1.2, A.7.3.1, A.8.2.2, A.8.2.3, A.9.1.1, A.9.1.2, A.9.2.3, A.9.4.1, A.9.4.4, A.9.4.5
nist | CM-6(a), AC-6(1)
nist-csf | PR.AC-4, PR.DS-5
os-srg | SRG-OS-000480-GPOS-00227
cis | 5.1.3
pcidss4 | 2.2.6, 2.2

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    find -H /etc/cron.hourly/ -maxdepth 1 -type d -exec chgrp -L 0 {} \;

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_groupowner_cron_hourly
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Ensure group owner on /etc/cron.hourly/
      file:
        path: /etc/cron.hourly/
        state: directory
        group: '0'
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_groupowner_cron_hourly
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

#### Rule Verify Group Who Owns cron.monthly [ref]

To properly set the group owner of `/etc/cron.monthly`, run the command:

    $ sudo chgrp root /etc/cron.monthly

Rationale: | Service configuration files enable or disable features of their respective services that if configured incorrectly can lead to insecure and vulnerable configurations. Therefore, service configuration files should be owned by the correct group to prevent unauthorized changes.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_file_groupowner_cron_monthly

References:

cis-csc | 12, 13, 14, 15, 16, 18, 3, 5
cobit5 | APO01.06, DSS05.04, DSS05.07, DSS06.02
disa | CCI-000366
isa-62443-2009 | 4.3.3.7.3
isa-62443-2013 | SR 2.1, SR 5.2
iso27001-2013 | A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.13.1.1, A.13.1.3, A.13.2.1, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, A.6.1.2, A.7.1.1, A.7.1.2, A.7.3.1, A.8.2.2, A.8.2.3, A.9.1.1, A.9.1.2, A.9.2.3, A.9.4.1, A.9.4.4, A.9.4.5
nist | CM-6(a), AC-6(1)
nist-csf | PR.AC-4, PR.DS-5
os-srg | SRG-OS-000480-GPOS-00227
cis | 5.1.6
pcidss4 | 2.2.6, 2.2

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    find -H /etc/cron.monthly/ -maxdepth 1 -type d -exec chgrp -L 0 {} \;

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_groupowner_cron_monthly
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Ensure group owner on /etc/cron.monthly/
      file:
        path: /etc/cron.monthly/
        state: directory
        group: '0'
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_groupowner_cron_monthly
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

#### Rule Verify Group Who Owns cron.weekly [ref]

To properly set the group owner of `/etc/cron.weekly`, run the command:

    $ sudo chgrp root /etc/cron.weekly

Rationale: | Service configuration files enable or disable features of their respective services that if configured incorrectly can lead to insecure and vulnerable configurations. Therefore, service configuration files should be owned by the correct group to prevent unauthorized changes.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_file_groupowner_cron_weekly

References:

cis-csc | 12, 13, 14, 15, 16, 18, 3, 5
cobit5 | APO01.06, DSS05.04, DSS05.07, DSS06.02
disa | CCI-000366
isa-62443-2009 | 4.3.3.7.3
isa-62443-2013 | SR 2.1, SR 5.2
iso27001-2013 | A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.13.1.1, A.13.1.3, A.13.2.1, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, A.6.1.2, A.7.1.1, A.7.1.2, A.7.3.1, A.8.2.2, A.8.2.3, A.9.1.1, A.9.1.2, A.9.2.3, A.9.4.1, A.9.4.4, A.9.4.5
nist | CM-6(a), AC-6(1)
nist-csf | PR.AC-4, PR.DS-5
os-srg | SRG-OS-000480-GPOS-00227
cis | 5.1.5
pcidss4 | 2.2.6, 2.2

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    find -H /etc/cron.weekly/ -maxdepth 1 -type d -exec chgrp -L 0 {} \;

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_groupowner_cron_weekly
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Ensure group owner on /etc/cron.weekly/
      file:
        path: /etc/cron.weekly/
        state: directory
        group: '0'
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_groupowner_cron_weekly
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

#### Rule Verify Group Who Owns Crontab [ref]

To properly set the group owner of `/etc/crontab`, run the command:

    $ sudo chgrp root /etc/crontab

Rationale: | Service configuration files enable or disable features of their respective services that if configured incorrectly can lead to insecure and vulnerable configurations. Therefore, service configuration files should be owned by the correct group to prevent unauthorized changes.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_file_groupowner_crontab

References:

cis-csc | 12, 13, 14, 15, 16, 18, 3, 5
cobit5 | APO01.06, DSS05.04, DSS05.07, DSS06.02
disa | CCI-000366
isa-62443-2009 | 4.3.3.7.3
isa-62443-2013 | SR 2.1, SR 5.2
iso27001-2013 | A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.13.1.1, A.13.1.3, A.13.2.1, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, A.6.1.2, A.7.1.1, A.7.1.2, A.7.3.1, A.8.2.2, A.8.2.3, A.9.1.1, A.9.1.2, A.9.2.3, A.9.4.1, A.9.4.4, A.9.4.5
nist | CM-6(a), AC-6(1)
nist-csf | PR.AC-4, PR.DS-5
os-srg | SRG-OS-000480-GPOS-00227
cis | 5.1.2
pcidss4 | 2.2.6, 2.2

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    chgrp 0 /etc/crontab

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_groupowner_crontab
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Test for existence /etc/crontab
      stat:
        path: /etc/crontab
      register: file_exists
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_groupowner_crontab
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Ensure group owner 0 on /etc/crontab
      file:
        path: /etc/crontab
        group: '0'
      when:
      - '"linux-base" in ansible_facts.packages'
      - file_exists.stat is defined and file_exists.stat.exists
      tags:
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_groupowner_crontab
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

#### Rule Verify Owner on cron.d [ref]

To properly set the owner of `/etc/cron.d`, run the command:

    $ sudo chown root /etc/cron.d

Rationale: | Service configuration files enable or disable features of their respective services that if configured incorrectly can lead to insecure and vulnerable configurations. Therefore, service configuration files should be owned by the correct user to prevent unauthorized changes.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_file_owner_cron_d

References:

cis-csc | 12, 13, 14, 15, 16, 18, 3, 5
cobit5 | APO01.06, DSS05.04, DSS05.07, DSS06.02
disa | CCI-000366
isa-62443-2009 | 4.3.3.7.3
isa-62443-2013 | SR 2.1, SR 5.2
iso27001-2013 | A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.13.1.1, A.13.1.3, A.13.2.1, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, A.6.1.2, A.7.1.1, A.7.1.2, A.7.3.1, A.8.2.2, A.8.2.3, A.9.1.1, A.9.1.2, A.9.2.3, A.9.4.1, A.9.4.4, A.9.4.5
nist | CM-6(a), AC-6(1)
nist-csf | PR.AC-4, PR.DS-5
os-srg | SRG-OS-000480-GPOS-00227
cis | 5.1.7
pcidss4 | 2.2.6, 2.2

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    find -H /etc/cron.d/ -maxdepth 1 -type d -exec chown -L 0 {} \;

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_owner_cron_d
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Ensure owner on directory /etc/cron.d/
      file:
        path: /etc/cron.d/
        state: directory
        owner: '0'
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_owner_cron_d
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

#### Rule Verify Owner on cron.daily [ref]

To properly set the owner of `/etc/cron.daily`, run the command:

    $ sudo chown root /etc/cron.daily

Rationale: | Service configuration files enable or disable features of their respective services that if configured incorrectly can lead to insecure and vulnerable configurations. Therefore, service configuration files should be owned by the correct user to prevent unauthorized changes.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_file_owner_cron_daily

References:

cis-csc | 12, 13, 14, 15, 16, 18, 3, 5
cobit5 | APO01.06, DSS05.04, DSS05.07, DSS06.02
disa | CCI-000366
isa-62443-2009 | 4.3.3.7.3
isa-62443-2013 | SR 2.1, SR 5.2
iso27001-2013 | A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.13.1.1, A.13.1.3, A.13.2.1, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, A.6.1.2, A.7.1.1, A.7.1.2, A.7.3.1, A.8.2.2, A.8.2.3, A.9.1.1, A.9.1.2, A.9.2.3, A.9.4.1, A.9.4.4, A.9.4.5
nist | CM-6(a), AC-6(1)
nist-csf | PR.AC-4, PR.DS-5
os-srg | SRG-OS-000480-GPOS-00227
cis | 5.1.4
pcidss4 | 2.2.6, 2.2

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    find -H /etc/cron.daily/ -maxdepth 1 -type d -exec chown -L 0 {} \;

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_owner_cron_daily
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Ensure owner on directory /etc/cron.daily/
      file:
        path: /etc/cron.daily/
        state: directory
        owner: '0'
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_owner_cron_daily
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

#### Rule Verify Owner on cron.hourly [ref]

To properly set the owner of `/etc/cron.hourly`, run the command:

    $ sudo chown root /etc/cron.hourly

Rationale: | Service configuration files enable or disable features of their respective services that if configured incorrectly can lead to insecure and vulnerable configurations. Therefore, service configuration files should be owned by the correct user to prevent unauthorized changes.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_file_owner_cron_hourly

References:

cis-csc | 12, 13, 14, 15, 16, 18, 3, 5
cobit5 | APO01.06, DSS05.04, DSS05.07, DSS06.02
disa | CCI-000366
isa-62443-2009 | 4.3.3.7.3
isa-62443-2013 | SR 2.1, SR 5.2
iso27001-2013 | A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.13.1.1, A.13.1.3, A.13.2.1, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, A.6.1.2, A.7.1.1, A.7.1.2, A.7.3.1, A.8.2.2, A.8.2.3, A.9.1.1, A.9.1.2, A.9.2.3, A.9.4.1, A.9.4.4, A.9.4.5
nist | CM-6(a), AC-6(1)
nist-csf | PR.AC-4, PR.DS-5
os-srg | SRG-OS-000480-GPOS-00227
cis | 5.1.3
pcidss4 | 2.2.6, 2.2

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    find -H /etc/cron.hourly/ -maxdepth 1 -type d -exec chown -L 0 {} \;

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_owner_cron_hourly
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Ensure owner on directory /etc/cron.hourly/
      file:
        path: /etc/cron.hourly/
        state: directory
        owner: '0'
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_owner_cron_hourly
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

#### Rule Verify Owner on cron.monthly [ref]

To properly set the owner of `/etc/cron.monthly`, run the command:

    $ sudo chown root /etc/cron.monthly

Rationale: | Service configuration files enable or disable features of their respective services that if configured incorrectly can lead to insecure and vulnerable configurations. Therefore, service configuration files should be owned by the correct user to prevent unauthorized changes.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_file_owner_cron_monthly

References:

cis-csc | 12, 13, 14, 15, 16, 18, 3, 5
cobit5 | APO01.06, DSS05.04, DSS05.07, DSS06.02
disa | CCI-000366
isa-62443-2009 | 4.3.3.7.3
isa-62443-2013 | SR 2.1, SR 5.2
iso27001-2013 | A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.13.1.1, A.13.1.3, A.13.2.1, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, A.6.1.2, A.7.1.1, A.7.1.2, A.7.3.1, A.8.2.2, A.8.2.3, A.9.1.1, A.9.1.2, A.9.2.3, A.9.4.1, A.9.4.4, A.9.4.5
nist | CM-6(a), AC-6(1)
nist-csf | PR.AC-4, PR.DS-5
os-srg | SRG-OS-000480-GPOS-00227
cis | 5.1.6
pcidss4 | 2.2.6, 2.2

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    find -H /etc/cron.monthly/ -maxdepth 1 -type d -exec chown -L 0 {} \;

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_owner_cron_monthly
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Ensure owner on directory /etc/cron.monthly/
      file:
        path: /etc/cron.monthly/
        state: directory
        owner: '0'
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_owner_cron_monthly
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

#### Rule Verify Owner on cron.weekly [ref]

To properly set the owner of `/etc/cron.weekly`, run the command:

    $ sudo chown root /etc/cron.weekly

Rationale: | Service configuration files enable or disable features of their respective services that if configured incorrectly can lead to insecure and vulnerable configurations. Therefore, service configuration files should be owned by the correct user to prevent unauthorized changes.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_file_owner_cron_weekly

References:

cis-csc | 12, 13, 14, 15, 16, 18, 3, 5
cobit5 | APO01.06, DSS05.04, DSS05.07, DSS06.02
disa | CCI-000366
isa-62443-2009 | 4.3.3.7.3
isa-62443-2013 | SR 2.1, SR 5.2
iso27001-2013 | A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.13.1.1, A.13.1.3, A.13.2.1, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, A.6.1.2, A.7.1.1, A.7.1.2, A.7.3.1, A.8.2.2, A.8.2.3, A.9.1.1, A.9.1.2, A.9.2.3, A.9.4.1, A.9.4.4, A.9.4.5
nist | CM-6(a), AC-6(1)
nist-csf | PR.AC-4, PR.DS-5
os-srg | SRG-OS-000480-GPOS-00227
cis | 5.1.5
pcidss4 | 2.2.6, 2.2

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    find -H /etc/cron.weekly/ -maxdepth 1 -type d -exec chown -L 0 {} \;

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_owner_cron_weekly
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Ensure owner on directory /etc/cron.weekly/
      file:
        path: /etc/cron.weekly/
        state: directory
        owner: '0'
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_owner_cron_weekly
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

#### Rule Verify Owner on crontab [ref]

To properly set the owner of `/etc/crontab`, run the command:

    $ sudo chown root /etc/crontab

Rationale: | Service configuration files enable or disable features of their respective services that if configured incorrectly can lead to insecure and vulnerable configurations. Therefore, service configuration files should be owned by the correct user to prevent unauthorized changes.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_file_owner_crontab

References:

cis-csc | 12, 13, 14, 15, 16, 18, 3, 5
cobit5 | APO01.06, DSS05.04, DSS05.07, DSS06.02
disa | CCI-000366
isa-62443-2009 | 4.3.3.7.3
isa-62443-2013 | SR 2.1, SR 5.2
iso27001-2013 | A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.13.1.1, A.13.1.3, A.13.2.1, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, A.6.1.2, A.7.1.1, A.7.1.2, A.7.3.1, A.8.2.2, A.8.2.3, A.9.1.1, A.9.1.2, A.9.2.3, A.9.4.1, A.9.4.4, A.9.4.5
nist | CM-6(a), AC-6(1)
nist-csf | PR.AC-4, PR.DS-5
os-srg | SRG-OS-000480-GPOS-00227
cis | 5.1.2
pcidss4 | 2.2.6, 2.2

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    chown 0 /etc/crontab

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_owner_crontab
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Test for existence /etc/crontab
      stat:
        path: /etc/crontab
      register: file_exists
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_owner_crontab
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Ensure owner 0 on /etc/crontab
      file:
        path: /etc/crontab
        owner: '0'
      when:
      - '"linux-base" in ansible_facts.packages'
      - file_exists.stat is defined and file_exists.stat.exists
      tags:
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_owner_crontab
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

#### Rule Verify Permissions on cron.d [ref]

To properly set the permissions of `/etc/cron.d`, run the command:

    $ sudo chmod 0700 /etc/cron.d

Rationale: | Service configuration files enable or disable features of their respective services that if configured incorrectly can lead to insecure and vulnerable configurations. Therefore, service configuration files should have the correct access rights to prevent unauthorized changes.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_file_permissions_cron_d

References:

cis-csc | 12, 13, 14, 15, 16, 18, 3, 5
cobit5 | APO01.06, DSS05.04, DSS05.07, DSS06.02
disa | CCI-000366
isa-62443-2009 | 4.3.3.7.3
isa-62443-2013 | SR 2.1, SR 5.2
iso27001-2013 | A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.13.1.1, A.13.1.3, A.13.2.1, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, A.6.1.2, A.7.1.1, A.7.1.2, A.7.3.1, A.8.2.2, A.8.2.3, A.9.1.1, A.9.1.2, A.9.2.3, A.9.4.1, A.9.4.4, A.9.4.5
nist | CM-6(a), AC-6(1)
nist-csf | PR.AC-4, PR.DS-5
os-srg | SRG-OS-000480-GPOS-00227
cis | 5.1.7
pcidss4 | 2.2.6, 2.2

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    find -H /etc/cron.d/ -maxdepth 1 -perm /u+s,g+xwrs,o+xwrt -type d -exec chmod u-s,g-xwrs,o-xwrt {} \;

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_permissions_cron_d
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Find /etc/cron.d/ file(s)
      command: 'find -H /etc/cron.d/ -maxdepth 1 -perm /u+s,g+xwrs,o+xwrt  -type d '
      register: files_found
      changed_when: false
      failed_when: false
      check_mode: false
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_permissions_cron_d
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Set permissions for /etc/cron.d/ file(s)
      file:
        path: '{{ item }}'
        mode: u-s,g-xwrs,o-xwrt
        state: directory
      with_items:
      - '{{ files_found.stdout_lines }}'
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_permissions_cron_d
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

#### Rule Verify Permissions on cron.daily [ref]

To properly set the permissions of `/etc/cron.daily`, run the command:

    $ sudo chmod 0700 /etc/cron.daily

Rationale: | Service configuration files enable or disable features of their respective services that if configured incorrectly can lead to insecure and vulnerable configurations. Therefore, service configuration files should have the correct access rights to prevent unauthorized changes.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_file_permissions_cron_daily

References:

cis-csc | 12, 13, 14, 15, 16, 18, 3, 5
cobit5 | APO01.06, DSS05.04, DSS05.07, DSS06.02
disa | CCI-000366
isa-62443-2009 | 4.3.3.7.3
isa-62443-2013 | SR 2.1, SR 5.2
iso27001-2013 | A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.13.1.1, A.13.1.3, A.13.2.1, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, A.6.1.2, A.7.1.1, A.7.1.2, A.7.3.1, A.8.2.2, A.8.2.3, A.9.1.1, A.9.1.2, A.9.2.3, A.9.4.1, A.9.4.4, A.9.4.5
nist | CM-6(a), AC-6(1)
nist-csf | PR.AC-4, PR.DS-5
os-srg | SRG-OS-000480-GPOS-00227
cis | 5.1.4
pcidss4 | 2.2.6, 2.2

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    find -H /etc/cron.daily/ -maxdepth 1 -perm /u+s,g+xwrs,o+xwrt -type d -exec chmod u-s,g-xwrs,o-xwrt {} \;

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_permissions_cron_daily
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Find /etc/cron.daily/ file(s)
      command: 'find -H /etc/cron.daily/ -maxdepth 1 -perm /u+s,g+xwrs,o+xwrt  -type d '
      register: files_found
      changed_when: false
      failed_when: false
      check_mode: false
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_permissions_cron_daily
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Set permissions for /etc/cron.daily/ file(s)
      file:
        path: '{{ item }}'
        mode: u-s,g-xwrs,o-xwrt
        state: directory
      with_items:
      - '{{ files_found.stdout_lines }}'
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_permissions_cron_daily
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

#### Rule Verify Permissions on cron.hourly [ref]

To properly set the permissions of `/etc/cron.hourly`, run the command:

    $ sudo chmod 0700 /etc/cron.hourly

Rationale: | Service configuration files enable or disable features of their respective services that if configured incorrectly can lead to insecure and vulnerable configurations. Therefore, service configuration files should have the correct access rights to prevent unauthorized changes.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_file_permissions_cron_hourly

References:

cis-csc | 12, 13, 14, 15, 16, 18, 3, 5
cobit5 | APO01.06, DSS05.04, DSS05.07, DSS06.02
disa | CCI-000366
isa-62443-2009 | 4.3.3.7.3
isa-62443-2013 | SR 2.1, SR 5.2
iso27001-2013 | A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.13.1.1, A.13.1.3, A.13.2.1, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, A.6.1.2, A.7.1.1, A.7.1.2, A.7.3.1, A.8.2.2, A.8.2.3, A.9.1.1, A.9.1.2, A.9.2.3, A.9.4.1, A.9.4.4, A.9.4.5
nist | CM-6(a), AC-6(1)
nist-csf | PR.AC-4, PR.DS-5
os-srg | SRG-OS-000480-GPOS-00227
cis | 5.1.3
pcidss4 | 2.2.6, 2.2

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    find -H /etc/cron.hourly/ -maxdepth 1 -perm /u+s,g+xwrs,o+xwrt -type d -exec chmod u-s,g-xwrs,o-xwrt {} \;

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_permissions_cron_hourly
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Find /etc/cron.hourly/ file(s)
      command: 'find -H /etc/cron.hourly/ -maxdepth 1 -perm /u+s,g+xwrs,o+xwrt  -type
        d '
      register: files_found
      changed_when: false
      failed_when: false
      check_mode: false
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_permissions_cron_hourly
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Set permissions for /etc/cron.hourly/ file(s)
      file:
        path: '{{ item }}'
        mode: u-s,g-xwrs,o-xwrt
        state: directory
      with_items:
      - '{{ files_found.stdout_lines }}'
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_permissions_cron_hourly
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

#### Rule Verify Permissions on cron.monthly [ref]

To properly set the permissions of `/etc/cron.monthly`, run the command:

    $ sudo chmod 0700 /etc/cron.monthly

Rationale: | Service configuration files enable or disable features of their respective services that if configured incorrectly can lead to insecure and vulnerable configurations. Therefore, service configuration files should have the correct access rights to prevent unauthorized changes.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_file_permissions_cron_monthly

References:

cis-csc | 12, 13, 14, 15, 16, 18, 3, 5
cobit5 | APO01.06, DSS05.04, DSS05.07, DSS06.02
disa | CCI-000366
isa-62443-2009 | 4.3.3.7.3
isa-62443-2013 | SR 2.1, SR 5.2
iso27001-2013 | A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.13.1.1, A.13.1.3, A.13.2.1, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, A.6.1.2, A.7.1.1, A.7.1.2, A.7.3.1, A.8.2.2, A.8.2.3, A.9.1.1, A.9.1.2, A.9.2.3, A.9.4.1, A.9.4.4, A.9.4.5
nist | CM-6(a), AC-6(1)
nist-csf | PR.AC-4, PR.DS-5
os-srg | SRG-OS-000480-GPOS-00227
cis | 5.1.6
pcidss4 | 2.2.6, 2.2

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    find -H /etc/cron.monthly/ -maxdepth 1 -perm /u+s,g+xwrs,o+xwrt -type d -exec chmod u-s,g-xwrs,o-xwrt {} \;

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_permissions_cron_monthly
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Find /etc/cron.monthly/ file(s)
      command: 'find -H /etc/cron.monthly/ -maxdepth 1 -perm /u+s,g+xwrs,o+xwrt  -type
        d '
      register: files_found
      changed_when: false
      failed_when: false
      check_mode: false
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_permissions_cron_monthly
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Set permissions for /etc/cron.monthly/ file(s)
      file:
        path: '{{ item }}'
        mode: u-s,g-xwrs,o-xwrt
        state: directory
      with_items:
      - '{{ files_found.stdout_lines }}'
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_permissions_cron_monthly
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

#### Rule Verify Permissions on cron.weekly [ref]

To properly set the permissions of `/etc/cron.weekly`, run the command:

    $ sudo chmod 0700 /etc/cron.weekly

Rationale: | Service configuration files enable or disable features of their respective services that if configured incorrectly can lead to insecure and vulnerable configurations. Therefore, service configuration files should have the correct access rights to prevent unauthorized changes.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_file_permissions_cron_weekly

References:

cis-csc | 12, 13, 14, 15, 16, 18, 3, 5
cobit5 | APO01.06, DSS05.04, DSS05.07, DSS06.02
disa | CCI-000366
isa-62443-2009 | 4.3.3.7.3
isa-62443-2013 | SR 2.1, SR 5.2
iso27001-2013 | A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.13.1.1, A.13.1.3, A.13.2.1, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, A.6.1.2, A.7.1.1, A.7.1.2, A.7.3.1, A.8.2.2, A.8.2.3, A.9.1.1, A.9.1.2, A.9.2.3, A.9.4.1, A.9.4.4, A.9.4.5
nist | CM-6(a), AC-6(1)
nist-csf | PR.AC-4, PR.DS-5
os-srg | SRG-OS-000480-GPOS-00227
cis | 5.1.5
pcidss4 | 2.2.6, 2.2

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    find -H /etc/cron.weekly/ -maxdepth 1 -perm /u+s,g+xwrs,o+xwrt -type d -exec chmod u-s,g-xwrs,o-xwrt {} \;

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_permissions_cron_weekly
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Find /etc/cron.weekly/ file(s)
      command: 'find -H /etc/cron.weekly/ -maxdepth 1 -perm /u+s,g+xwrs,o+xwrt  -type
        d '
      register: files_found
      changed_when: false
      failed_when: false
      check_mode: false
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_permissions_cron_weekly
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Set permissions for /etc/cron.weekly/ file(s)
      file:
        path: '{{ item }}'
        mode: u-s,g-xwrs,o-xwrt
        state: directory
      with_items:
      - '{{ files_found.stdout_lines }}'
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_permissions_cron_weekly
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

#### Rule Verify Permissions on crontab [ref]

To properly set the permissions of `/etc/crontab`, run the command:

    $ sudo chmod 0600 /etc/crontab

Rationale: | Service configuration files enable or disable features of their respective services that if configured incorrectly can lead to insecure and vulnerable configurations. Therefore, service configuration files should have the correct access rights to prevent unauthorized changes.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_file_permissions_crontab

References:

cis-csc | 12, 13, 14, 15, 16, 18, 3, 5
cobit5 | APO01.06, DSS05.04, DSS05.07, DSS06.02
disa | CCI-000366
isa-62443-2009 | 4.3.3.7.3
isa-62443-2013 | SR 2.1, SR 5.2
iso27001-2013 | A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.13.1.1, A.13.1.3, A.13.2.1, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, A.6.1.2, A.7.1.1, A.7.1.2, A.7.3.1, A.8.2.2, A.8.2.3, A.9.1.1, A.9.1.2, A.9.2.3, A.9.4.1, A.9.4.4, A.9.4.5
nist | CM-6(a), AC-6(1)
nist-csf | PR.AC-4, PR.DS-5
os-srg | SRG-OS-000480-GPOS-00227
cis | 5.1.2
pcidss4 | 2.2.6, 2.2

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    chmod u-xs,g-xwrs,o-xwrt /etc/crontab

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_permissions_crontab
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Test for existence /etc/crontab
      stat:
        path: /etc/crontab
      register: file_exists
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_permissions_crontab
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Ensure permission u-xs,g-xwrs,o-xwrt on /etc/crontab
      file:
        path: /etc/crontab
        mode: u-xs,g-xwrs,o-xwrt
      when:
      - '"linux-base" in ansible_facts.packages'
      - file_exists.stat is defined and file_exists.stat.exists
      tags:
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_permissions_crontab
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

Group Deprecated services Group contains 1 rule
[ref] Some deprecated software services impact the overall system security due to their behavior (leak of confidentiality in network exchange, usage as uncontrolled communication channel, risk associated with the service due to its old age, etc.

#### Rule Uninstall the nis package [ref]

The support for Yellowpages should not be installed unless it is required.
Rationale: | NIS is the historical SUN service for central account management, more and more replaced by LDAP. NIS does not support efficiently security constraints, ACL, etc. and should not be used.
Severity: | low
Rule ID: | xccdf_org.ssgproject.content_rule_package_nis_removed

References:

cis | 2.2.17

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    # CAUTION: This remediation script will remove nis
    #	   from the system, and may remove any packages
    #	   that depend on nis. Execute this
    #	   remediation AFTER testing on a non-production
    #	   system!

    DEBIAN_FRONTEND=noninteractive apt-get remove -y "nis"

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    - name: Ensure nis is removed
      package:
        name: nis
        state: absent
      tags:
      - disable_strategy
      - low_complexity
      - low_disruption
      - low_severity
      - no_reboot_needed
      - package_nis_removed

Remediation Puppet snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    include remove_nis

    class remove_nis {
      package { 'nis':
        ensure => 'purged',
      }
    }

Group DHCP Group contains 1 group and 1 rule

[ref] The Dynamic Host Configuration Protocol (DHCP) allows systems to request and obtain an IP address and other configuration parameters from a server.
This guide recommends configuring networking on clients by manually editing the appropriate files under `/etc/sysconfig`. Use of DHCP can make client systems vulnerable to compromise by rogue DHCP servers, and should be avoided unless necessary. If using DHCP is necessary, however, there are best practices that should be followed to minimize security risk.

Group Disable DHCP Server Group contains 1 rule
[ref] The DHCP server `dhcpd` is not installed or activated by default. If the software was installed and activated, but the system does not need to act as a DHCP server, it should be disabled and removed.

#### Rule Uninstall DHCP Server Package [ref]

If the system does not need to act as a DHCP server, the dhcp package can be uninstalled. The `isc-dhcp-server` package can be removed with the following command:

    $ apt-get remove isc-dhcp-server

Rationale: | Removing the DHCP server ensures that it cannot be easily or accidentally reactivated and disrupt network operation.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_package_dhcp_removed

References:

cis-csc | 11, 14, 3, 9
cobit5 | BAI10.01, BAI10.02, BAI10.03, BAI10.05, DSS05.02, DSS05.05, DSS06.06
disa | CCI-000366
isa-62443-2009 | 4.3.3.5.1, 4.3.3.5.2, 4.3.3.5.3, 4.3.3.5.4, 4.3.3.5.5, 4.3.3.5.6, 4.3.3.5.7, 4.3.3.5.8, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.1, 4.3.3.7.2, 4.3.3.7.3, 4.3.3.7.4, 4.3.4.3.2, 4.3.4.3.3
isa-62443-2013 | SR 1.1, SR 1.10, SR 1.11, SR 1.12, SR 1.13, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.6, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 2.2, SR 2.3, SR 2.4, SR 2.5, SR 2.6, SR 2.7, SR 7.6
iso27001-2013 | A.12.1.2, A.12.5.1, A.12.6.2, A.14.2.2, A.14.2.3, A.14.2.4, A.9.1.2
nist | CM-7(a), CM-7(b), CM-6(a)
nist-csf | PR.IP-1, PR.PT-3
cis | 2.2.5
anssi | R62
pcidss4 | 2.2.4, 2.2

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    # CAUTION: This remediation script will remove isc-dhcp-server
    #	   from the system, and may remove any packages
    #	   that depend on isc-dhcp-server. Execute this
    #	   remediation AFTER testing on a non-production
    #	   system!

    DEBIAN_FRONTEND=noninteractive apt-get remove -y "isc-dhcp-server"

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    - name: Ensure isc-dhcp-server is removed
      package:
        name: isc-dhcp-server
        state: absent
      tags:
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.4
      - disable_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - package_dhcp_removed

Remediation Puppet snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    include remove_isc-dhcp-server

    class remove_isc-dhcp-server {
      package { 'isc-dhcp-server':
        ensure => 'purged',
      }
    }

Group DNS Server Group contains 1 group and 1 rule
[ref] Most organizations have an operational need to run at least one nameserver. However, there are many common attacks involving DNS server software, and this server software should be disabled on any system on which it is not needed.
Group Disable DNS Server Group contains 1 rule
[ref] DNS software should be disabled on any systems which does not need to be a nameserver. Note that the BIND DNS server software is not installed on Ubuntu 20.04 by default. The remainder of this section discusses secure configuration of systems which must be nameservers.

#### Rule Uninstall bind Package [ref]

The `named` service is provided by the `bind` package. The `bind` package can be removed with the following command:

    $ apt-get remove bind

Rationale: | If there is no need to make DNS server software available, removing it provides a safeguard against its activation.
Severity: | low
Rule ID: | xccdf_org.ssgproject.content_rule_package_bind_removed

References:

cis-csc | 11, 14, 3, 9
cobit5 | BAI10.01, BAI10.02, BAI10.03, BAI10.05, DSS05.02, DSS05.05, DSS06.06
disa | CCI-000366
isa-62443-2009 | 4.3.3.5.1, 4.3.3.5.2, 4.3.3.5.3, 4.3.3.5.4, 4.3.3.5.5, 4.3.3.5.6, 4.3.3.5.7, 4.3.3.5.8, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.1, 4.3.3.7.2, 4.3.3.7.3, 4.3.3.7.4, 4.3.4.3.2, 4.3.4.3.3
isa-62443-2013 | SR 1.1, SR 1.10, SR 1.11, SR 1.12, SR 1.13, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.6, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 2.2, SR 2.3, SR 2.4, SR 2.5, SR 2.6, SR 2.7, SR 7.6
iso27001-2013 | A.12.1.2, A.12.5.1, A.12.6.2, A.14.2.2, A.14.2.3, A.14.2.4, A.9.1.2
nist | CM-7(a), CM-7(b), CM-6(a)
nist-csf | PR.IP-1, PR.PT-3
cis | 2.2.8

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    # CAUTION: This remediation script will remove bind9
    #	   from the system, and may remove any packages
    #	   that depend on bind9. Execute this
    #	   remediation AFTER testing on a non-production
    #	   system!

    DEBIAN_FRONTEND=noninteractive apt-get remove -y "bind9"

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    - name: Ensure bind9 is removed
      package:
        name: bind9
        state: absent
      tags:
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - disable_strategy
      - low_complexity
      - low_disruption
      - low_severity
      - no_reboot_needed
      - package_bind_removed

Remediation Puppet snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    include remove_bind9

    class remove_bind9 {
      package { 'bind9':
        ensure => 'purged',
      }
    }

Group FTP Server Group contains 1 group and 1 rule

[ref] FTP is a common method for allowing remote access to files. Like telnet, the FTP protocol is unencrypted, which means that passwords and other data transmitted during the session can be captured and that the session is vulnerable to hijacking. Therefore, running the FTP server software is not recommended.
However, there are some FTP server configurations which may be appropriate for some environments, particularly those which allow only read-only anonymous access as a means of downloading data available to the public.

Group Disable vsftpd if Possible Group contains 1 rule
[ref] To minimize attack surface, disable vsftpd if at all possible.

#### Rule Uninstall vsftpd Package [ref]

The `vsftpd` package can be removed with the following command:

     $ apt-get remove vsftpd

Rationale: | Removing the `vsftpd` package decreases the risk of its accidental activation.
Severity: | high
Rule ID: | xccdf_org.ssgproject.content_rule_package_vsftpd_removed

References:

cis-csc | 11, 14, 3, 9
cobit5 | BAI10.01, BAI10.02, BAI10.03, BAI10.05, DSS05.02, DSS05.05, DSS06.06
disa | CCI-000366, CCI-000197, CCI-000381
isa-62443-2009 | 4.3.3.5.1, 4.3.3.5.2, 4.3.3.5.3, 4.3.3.5.4, 4.3.3.5.5, 4.3.3.5.6, 4.3.3.5.7, 4.3.3.5.8, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.1, 4.3.3.7.2, 4.3.3.7.3, 4.3.3.7.4, 4.3.4.3.2, 4.3.4.3.3
isa-62443-2013 | SR 1.1, SR 1.10, SR 1.11, SR 1.12, SR 1.13, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.6, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 2.2, SR 2.3, SR 2.4, SR 2.5, SR 2.6, SR 2.7, SR 7.6
iso27001-2013 | A.12.1.2, A.12.5.1, A.12.6.2, A.14.2.2, A.14.2.3, A.14.2.4, A.9.1.2
nist | CM-7(a), CM-7(b), CM-6(a), IA-5(1)(c), IA-5(1).1(v), CM-7, CM-7.1(ii)
nist-csf | PR.IP-1, PR.PT-3
os-srg | SRG-OS-000074-GPOS-00042, SRG-OS-000095-GPOS-00049, SRG-OS-000480-GPOS-00227
cis | 2.2.9

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    # CAUTION: This remediation script will remove vsftpd
    #	   from the system, and may remove any packages
    #	   that depend on vsftpd. Execute this
    #	   remediation AFTER testing on a non-production
    #	   system!

    DEBIAN_FRONTEND=noninteractive apt-get remove -y "vsftpd"

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    - name: Ensure vsftpd is removed
      package:
        name: vsftpd
        state: absent
      tags:
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-CM-7.1(ii)
      - NIST-800-53-IA-5(1)(c)
      - NIST-800-53-IA-5(1).1(v)
      - disable_strategy
      - high_severity
      - low_complexity
      - low_disruption
      - no_reboot_needed
      - package_vsftpd_removed

Remediation Puppet snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    include remove_vsftpd

    class remove_vsftpd {
      package { 'vsftpd':
        ensure => 'purged',
      }
    }

Group Web Server Group contains 2 groups and 2 rules

[ref] The web server is responsible for providing access to content via the HTTP protocol. Web servers represent a significant security risk because:

- The HTTP port is commonly probed by malicious sources
- Web server software is very complex, and includes a long history of vulnerabilities
- The HTTP protocol is unencrypted and vulnerable to passive monitoring

The system's default web server software is Apache 2 and is provided in the RPM package `httpd`.

Group Disable Apache if Possible Group contains 1 rule
[ref] If Apache was installed and activated, but the system does not need to act as a web server, then it should be disabled and removed from the system.

#### Rule Uninstall apache2 Package [ref]

The `apache2` package can be removed with the following command:

    $ apt-get remove apache2

Rationale: | If there is no need to make the web server software available, removing it provides a safeguard against its activation.
Severity: | unknown
Rule ID: | xccdf_org.ssgproject.content_rule_package_httpd_removed

References:

cis-csc | 11, 14, 3, 9
cobit5 | BAI10.01, BAI10.02, BAI10.03, BAI10.05, DSS05.02, DSS05.05, DSS06.06
isa-62443-2009 | 4.3.3.5.1, 4.3.3.5.2, 4.3.3.5.3, 4.3.3.5.4, 4.3.3.5.5, 4.3.3.5.6, 4.3.3.5.7, 4.3.3.5.8, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.1, 4.3.3.7.2, 4.3.3.7.3, 4.3.3.7.4, 4.3.4.3.2, 4.3.4.3.3
isa-62443-2013 | SR 1.1, SR 1.10, SR 1.11, SR 1.12, SR 1.13, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.6, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 2.2, SR 2.3, SR 2.4, SR 2.5, SR 2.6, SR 2.7, SR 7.6
iso27001-2013 | A.12.1.2, A.12.5.1, A.12.6.2, A.14.2.2, A.14.2.3, A.14.2.4, A.9.1.2
nist | CM-7(a), CM-7(b), CM-6(a)
nist-csf | PR.IP-1, PR.PT-3
cis | 2.2.10

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    # CAUTION: This remediation script will remove apache2
    #	   from the system, and may remove any packages
    #	   that depend on apache2. Execute this
    #	   remediation AFTER testing on a non-production
    #	   system!

    DEBIAN_FRONTEND=noninteractive apt-get remove -y "apache2"

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    - name: Ensure apache2 is removed
      package:
        name: apache2
        state: absent
      tags:
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - disable_strategy
      - low_complexity
      - low_disruption
      - no_reboot_needed
      - package_httpd_removed
      - unknown_severity

Remediation Puppet snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    include remove_apache2

    class remove_apache2 {
      package { 'apache2':
        ensure => 'purged',
      }
    }

Group Disable NGINX if Possible Group contains 1 rule
[ref] If NGINX was installed and activated, but the system does not need to act as a web server, then it should be removed from the system.

#### Rule Uninstall nginx Package [ref]

The `nginx` package can be removed with the following command:

    $ apt-get remove nginx

Rationale: | If there is no need to make the web server software available, removing it provides a safeguard against its activation.
Severity: | unknown
Rule ID: | xccdf_org.ssgproject.content_rule_package_nginx_removed

References:

cobit5 | BAI10.01, BAI10.02, BAI10.03, BAI10.05, DSS05.02, DSS05.05, DSS06.06
isa-62443-2009 | 4.3.3.5.1, 4.3.3.5.2, 4.3.3.5.3, 4.3.3.5.4, 4.3.3.5.5, 4.3.3.5.6, 4.3.3.5.7, 4.3.3.5.8, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.1, 4.3.3.7.2, 4.3.3.7.3, 4.3.3.7.4, 4.3.4.3.2, 4.3.4.3.3
isa-62443-2013 | SR 1.1, SR 1.10, SR 1.11, SR 1.12, SR 1.13, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.6, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 2.2, SR 2.3, SR 2.4, SR 2.5, SR 2.6, SR 2.7, SR 7.6
iso27001-2013 | A.12.1.2, A.12.5.1, A.12.6.2, A.14.2.2, A.14.2.3, A.14.2.4, A.9.1.2
nist | CM-7(a), CM-7(b), CM-6(a)
nist-csf | PR.IP-1, PR.PT-3
cis | 2.2.10

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    # CAUTION: This remediation script will remove nginx
    #	   from the system, and may remove any packages
    #	   that depend on nginx. Execute this
    #	   remediation AFTER testing on a non-production
    #	   system!

    DEBIAN_FRONTEND=noninteractive apt-get remove -y "nginx"

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    - name: Ensure nginx is removed
      package:
        name: nginx
        state: absent
      tags:
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - disable_strategy
      - low_complexity
      - low_disruption
      - no_reboot_needed
      - package_nginx_removed
      - unknown_severity

Remediation Puppet snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    include remove_nginx

    class remove_nginx {
      package { 'nginx':
        ensure => 'purged',
      }
    }

Group IMAP and POP3 Server Group contains 2 groups and 2 rules
[ref] Dovecot provides IMAP and POP3 services. It is not installed by default. The project page at http://www.dovecot.org contains more detailed information about Dovecot configuration.
Group Disable Cyrus IMAP Group contains 1 rule
[ref] If the system does not need to operate as an IMAP or POP3 server, the Cyrus IMAP software should be removed.

#### Rule Uninstall cyrus-imapd Package [ref]

The `cyrus-imapd` package can be removed with the following command:

    $ apt-get remove cyrus-imapd

Rationale: | If there is no need to make the cyrus-imapd software available, removing it provides a safeguard against its activation.
Severity: | unknown
Rule ID: | xccdf_org.ssgproject.content_rule_package_cyrus-imapd_removed

References:

cis | 2.2.11

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    # CAUTION: This remediation script will remove cyrus-imapd
    #	   from the system, and may remove any packages
    #	   that depend on cyrus-imapd. Execute this
    #	   remediation AFTER testing on a non-production
    #	   system!

    DEBIAN_FRONTEND=noninteractive apt-get remove -y "cyrus-imapd"

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    - name: Ensure cyrus-imapd is removed
      package:
        name: cyrus-imapd
        state: absent
      tags:
      - disable_strategy
      - low_complexity
      - low_disruption
      - no_reboot_needed
      - package_cyrus-imapd_removed
      - unknown_severity

Remediation Puppet snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    include remove_cyrus-imapd

    class remove_cyrus-imapd {
      package { 'cyrus-imapd':
        ensure => 'purged',
      }
    }

Group Disable Dovecot Group contains 1 rule
[ref] If the system does not need to operate as an IMAP or POP3 server, the dovecot software should be disabled and removed.

#### Rule Uninstall dovecot Package [ref]

The `dovecot-core` package can be removed with the following command:

    $ apt-get remove dovecot-core

Rationale: | If there is no need to make the Dovecot software available, removing it provides a safeguard against its activation.
Severity: | unknown
Rule ID: | xccdf_org.ssgproject.content_rule_package_dovecot_removed

References:

cis | 2.2.11

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    # CAUTION: This remediation script will remove dovecot-core
    #	   from the system, and may remove any packages
    #	   that depend on dovecot-core. Execute this
    #	   remediation AFTER testing on a non-production
    #	   system!

    DEBIAN_FRONTEND=noninteractive apt-get remove -y "dovecot-core"

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    - name: Ensure dovecot-core is removed
      package:
        name: dovecot-core
        state: absent
      tags:
      - disable_strategy
      - low_complexity
      - low_disruption
      - no_reboot_needed
      - package_dovecot_removed
      - unknown_severity

Remediation Puppet snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    include remove_dovecot-core

    class remove_dovecot-core {
      package { 'dovecot-core':
        ensure => 'purged',
      }
    }

Group LDAP Group contains 2 groups and 2 rules
[ref] LDAP is a popular directory service, that is, a standardized way of looking up information from a central database. Ubuntu 20.04 includes software that enables a system to act as both an LDAP client and server.
Group Configure OpenLDAP Clients Group contains 1 rule

[ref] This section provides information on which security settings are important to configure in OpenLDAP clients by manually editing the appropriate configuration files. Ubuntu 20.04 provides an automated configuration tool called authconfig and a graphical wrapper for authconfig called `system-config-authentication`. However, these tools do not provide as much control over configuration as manual editing of configuration files. The authconfig tools do not allow you to specify locations of SSL certificate files, which is useful when trying to use SSL cleanly across several protocols. Installation and configuration of OpenLDAP on Ubuntu 20.04 is available at
Warning: Before configuring any system to be an LDAP client, ensure that a working LDAP server is present on the network.

#### Rule Ensure LDAP client is not installed [ref]

The Lightweight Directory Access Protocol (LDAP) is a service that provides a method for looking up information from a central database. The `lapd-utils` package can be removed with the following command:

    $ apt-get remove lapd-utils

Rationale: | If the system does not need to act as an LDAP client, it is recommended that the software is removed to reduce the potential attack surface.
Severity: | low
Rule ID: | xccdf_org.ssgproject.content_rule_package_openldap-clients_removed

References:

cis | 2.3.5

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    # CAUTION: This remediation script will remove ldap-utils
    #	   from the system, and may remove any packages
    #	   that depend on ldap-utils. Execute this
    #	   remediation AFTER testing on a non-production
    #	   system!

    DEBIAN_FRONTEND=noninteractive apt-get remove -y "ldap-utils"

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    - name: Ensure ldap-utils is removed
      package:
        name: ldap-utils
        state: absent
      tags:
      - disable_strategy
      - low_complexity
      - low_disruption
      - low_severity
      - no_reboot_needed
      - package_openldap-clients_removed

Remediation Puppet snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    include remove_ldap-utils

    class remove_ldap-utils {
      package { 'ldap-utils':
        ensure => 'purged',
      }
    }

Group Configure OpenLDAP Server Group contains 1 rule
[ref] This section details some security-relevant settings for an OpenLDAP server.

#### Rule Uninstall openldap-servers Package [ref]

The slapd package is not installed by default on a Ubuntu 20.04 system. It is needed only by the OpenLDAP server, not by the clients which use LDAP for authentication. If the system is not intended for use as an LDAP Server it should be removed.
Rationale: | Unnecessary packages should not be installed to decrease the attack surface of the system. While this software is clearly essential on an LDAP server, it is not necessary on typical desktop or workstation systems.
Severity: | low
Rule ID: | xccdf_org.ssgproject.content_rule_package_openldap-servers_removed

References:

cis-csc | 11, 14, 3, 9
cobit5 | BAI10.01, BAI10.02, BAI10.03, BAI10.05, DSS05.02, DSS05.05, DSS06.06
disa | CCI-000366
isa-62443-2009 | 4.3.3.5.1, 4.3.3.5.2, 4.3.3.5.3, 4.3.3.5.4, 4.3.3.5.5, 4.3.3.5.6, 4.3.3.5.7, 4.3.3.5.8, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.1, 4.3.3.7.2, 4.3.3.7.3, 4.3.3.7.4, 4.3.4.3.2, 4.3.4.3.3
isa-62443-2013 | SR 1.1, SR 1.10, SR 1.11, SR 1.12, SR 1.13, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.6, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 2.2, SR 2.3, SR 2.4, SR 2.5, SR 2.6, SR 2.7, SR 7.6
iso27001-2013 | A.12.1.2, A.12.5.1, A.12.6.2, A.14.2.2, A.14.2.3, A.14.2.4, A.9.1.2
nist | CM-7(a), CM-7(b), CM-6(a)
nist-csf | PR.IP-1, PR.PT-3
cis | 2.2.6

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    # CAUTION: This remediation script will remove slapd
    #	   from the system, and may remove any packages
    #	   that depend on slapd. Execute this
    #	   remediation AFTER testing on a non-production
    #	   system!

    DEBIAN_FRONTEND=noninteractive apt-get remove -y "slapd"

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    - name: Ensure slapd is removed
      package:
        name: slapd
        state: absent
      tags:
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - disable_strategy
      - low_complexity
      - low_disruption
      - low_severity
      - no_reboot_needed
      - package_openldap-servers_removed

Remediation Puppet snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    include remove_slapd

    class remove_slapd {
      package { 'slapd':
        ensure => 'purged',
      }
    }

Group Mail Server Software Group contains 1 group and 2 rules

[ref] Mail servers are used to send and receive email over the network. Mail is a very common service, and Mail Transfer Agents (MTAs) are obvious targets of network attack. Ensure that systems are not running MTAs unnecessarily, and configure needed MTAs as defensively as possible.
Very few systems at any site should be configured to directly receive email over the network. Users should instead use mail client programs to retrieve email from a central server that supports protocols such as IMAP or POP3. However, it is normal for most systems to be independently capable of sending email, for instance so that cron jobs can report output to an administrator. Most MTAs, including Postfix, support a submission-only mode in which mail can be sent from the local system to a central site MTA (or directly delivered to a local account), but the system still cannot receive mail directly over a network.
The `alternatives` program in Ubuntu 20.04 permits selection of other mail server software (such as Sendmail), but Postfix is the default and is preferred. Postfix was coded with security in mind and can also be more effectively contained by SELinux as its modular design has resulted in separate processes performing specific actions. More information is available on its website, http://www.postfix.org.

Group Configure SMTP For Mail Clients Group contains 1 rule
[ref] This section discusses settings for Postfix in a submission-only e-mail configuration.

#### Rule Disable Postfix Network Listening [ref]

Edit the file `/etc/postfix/main.cf` to ensure that only the following `inet_interfaces` line appears:

    inet_interfaces = loopback-only

Rationale: | This ensures `postfix` accepts mail messages (such as cron job reports) from the local system only, and not from the network, which protects it from network attack.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_postfix_network_listening_disabled

References:

cis-csc | 11, 14, 3, 9
cobit5 | BAI10.01, BAI10.02, BAI10.03, BAI10.05, DSS05.02, DSS05.05, DSS06.06
disa | CCI-000382
isa-62443-2009 | 4.3.3.5.1, 4.3.3.5.2, 4.3.3.5.3, 4.3.3.5.4, 4.3.3.5.5, 4.3.3.5.6, 4.3.3.5.7, 4.3.3.5.8, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.1, 4.3.3.7.2, 4.3.3.7.3, 4.3.3.7.4, 4.3.4.3.2, 4.3.4.3.3
isa-62443-2013 | SR 1.1, SR 1.10, SR 1.11, SR 1.12, SR 1.13, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.6, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 2.2, SR 2.3, SR 2.4, SR 2.5, SR 2.6, SR 2.7, SR 7.6
iso27001-2013 | A.12.1.2, A.12.5.1, A.12.6.2, A.14.2.2, A.14.2.3, A.14.2.4, A.9.1.2
nist | CM-7(a), CM-7(b), CM-6(a)
nist-csf | PR.IP-1, PR.PT-3
cis | 2.2.15
anssi | R74
pcidss4 | 1.4.2, 1.4

Remediation Shell script ⇲

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed && { dpkg-query --show --showformat='${db:Status-Status}\n' 'postfix' 2>/dev/null | grep -q '^installed'; }; then

    var_postfix_inet_interfaces='loopback-only'

    if [ -e "/etc/postfix/main.cf" ] ; then

        LC_ALL=C sed -i "/^\s*inet_interfaces\s\+=\s\+/Id" "/etc/postfix/main.cf"
    else
        touch "/etc/postfix/main.cf"
    fi
    # make sure file has newline at the end
    sed -i -e '$a\' "/etc/postfix/main.cf"

    cp "/etc/postfix/main.cf" "/etc/postfix/main.cf.bak"
    # Insert at the end of the file
    printf '%s\n' "inet_interfaces=$var_postfix_inet_interfaces" >> "/etc/postfix/main.cf"
    # Clean up after ourselves.
    rm "/etc/postfix/main.cf.bak"

    systemctl restart postfix

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

#### Rule Ensure Mail Transfer Agent is not Listening on any non-loopback Address [ref]

Mail Transfer Agents (MTA), such as sendmail and Postfix, are used to listen for incoming mail and transfer the messages to the appropriate user or mail server. If the system is not intended to be a mail server, it is recommended that the MTA be configured to only process local mail.
Rationale: | The software for all Mail Transfer Agents is complex and most have a long history of security issues. While it is important to ensure that the system can process local mail messages, it is not necessary to have the MTA's daemon listening on a port unless the server is intended to be a mail server that receives and processes mail from other systems.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_has_nonlocal_mta

References:

cis | 2.2.15

Group NFS and RPC Group contains 2 groups and 2 rules

[ref] The Network File System is a popular distributed filesystem for the Unix environment, and is very widely deployed. This section discusses the circumstances under which it is possible to disable NFS and its dependencies, and then details steps which should be taken to secure NFS's configuration. This section is relevant to systems operating as NFS clients, as well as to those operating as NFS servers.

Group Disable All NFS Services if Possible Group contains 1 group and 1 rule
[ref] If there is not a reason for the system to operate as either an NFS client or an NFS server, follow all instructions in this section to disable subsystems required by NFS. Warning: The steps in this section will prevent a system from operating as either an NFS client or an NFS server. Only perform these steps on systems which do not need NFS at all.
Group Disable Services Used Only by NFS Group contains 1 rule
[ref] If NFS is not needed, disable the NFS client daemons nfslock, rpcgssd, and rpcidmapd. All of these daemons run with elevated privileges, and many listen for network connections. If they are not needed, they should be disabled to improve system security posture.

#### Rule Uninstall rpcbind Package [ref]

The rpcbind utility maps RPC services to the ports on which they listen. RPC processes notify rpcbind when they start, registering the ports they are listening on and the RPC program numbers they expect to serve. The rpcbind service redirects the client to the proper port number so it can communicate with the requested service. If the system does not require RPC (such as for NFS servers) then this service should be disabled. The `rpcbind` package can be removed with the following command:

    $ apt-get remove rpcbind

Rationale: | If the system does not require rpc based services, it is recommended that rpcbind be disabled to reduce the attack surface.
Severity: | low
Rule ID: | xccdf_org.ssgproject.content_rule_package_rpcbind_removed

References:

cis | 2.3.6

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    # CAUTION: This remediation script will remove rpcbind
    #	   from the system, and may remove any packages
    #	   that depend on rpcbind. Execute this
    #	   remediation AFTER testing on a non-production
    #	   system!

    DEBIAN_FRONTEND=noninteractive apt-get remove -y "rpcbind"

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - disable_strategy
      - low_complexity
      - low_disruption
      - low_severity
      - no_reboot_needed
      - package_rpcbind_removed

    - name: Ensure rpcbind is removed
      package:
        name: rpcbind
        state: absent
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - disable_strategy
      - low_complexity
      - low_disruption
      - low_severity
      - no_reboot_needed
      - package_rpcbind_removed

Remediation Puppet snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    include remove_rpcbind

    class remove_rpcbind {
      package { 'rpcbind':
        ensure => 'purged',
      }
    }

#### Rule Uninstall nfs-kernel-server Package [ref]

The `nfs-kernel-server` package can be removed with the following command:

    $ apt-get remove nfs-kernel-server

Rationale: | If the system does not export NFS shares or act as an NFS client, it is recommended that these services be removed to reduce the remote attack surface.
Severity: | low
Rule ID: | xccdf_org.ssgproject.content_rule_package_nfs-kernel-server_removed

References:

cis | 2.2.7

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    # CAUTION: This remediation script will remove nfs-kernel-server
    #	   from the system, and may remove any packages
    #	   that depend on nfs-kernel-server. Execute this
    #	   remediation AFTER testing on a non-production
    #	   system!

    DEBIAN_FRONTEND=noninteractive apt-get remove -y "nfs-kernel-server"

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    - name: Ensure nfs-kernel-server is removed
      package:
        name: nfs-kernel-server
        state: absent
      tags:
      - disable_strategy
      - low_complexity
      - low_disruption
      - low_severity
      - no_reboot_needed
      - package_nfs-kernel-server_removed

Remediation Puppet snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    include remove_nfs-kernel-server

    class remove_nfs-kernel-server {
      package { 'nfs-kernel-server':
        ensure => 'purged',
      }
    }

Group Network Time Protocol Group contains 8 rules

[ref] The Network Time Protocol is used to manage the system clock over a network. Computer clocks are not very accurate, so time will drift unpredictably on unmanaged systems. Central time protocols can be used both to ensure that time is consistent among a network of systems, and that their time is consistent with the outside world.
If every system on a network reliably reports the same time, then it is much easier to correlate log messages in case of an attack. In addition, a number of cryptographic protocols (such as Kerberos) use timestamps to prevent certain types of attacks. If your network does not have synchronized time, these protocols may be unreliable or even unusable.
Depending on the specifics of the network, global time accuracy may be just as important as local synchronization, or not very important at all. If your network is connected to the Internet, using a public timeserver (or one provided by your enterprise) provides globally accurate timestamps which may be essential in investigating or responding to an attack which originated outside of your network.
A typical network setup involves a small number of internal systems operating as NTP servers, and the remainder obtaining time information from those internal servers.
There is a choice between the daemons `ntpd` and `chronyd`, which are available from the repositories in the `ntp` and `chrony` packages respectively.
The default `chronyd` daemon can work well when external time references are only intermittently accesible, can perform well even when the network is congested for longer periods of time, can usually synchronize the clock faster and with better time accuracy, and quickly adapts to sudden changes in the rate of the clock, for example, due to changes in the temperature of the crystal oscillator. `Chronyd` should be considered for all systems which are frequently suspended or otherwise intermittently disconnected and reconnected to a network. Mobile and virtual systems for example.
The `ntpd` NTP daemon fully supports NTP protocol version 4 (RFC 5905), including broadcast, multicast, manycast clients and servers, and the orphan mode. It also supports extra authentication schemes based on public-key cryptography (RFC 5906). The NTP daemon (`ntpd`) should be considered for systems which are normally kept permanently on. Systems which are required to use broadcast or multicast IP, or to perform authentication of packets with the `Autokey` protocol, should consider using `ntpd`.
Refer to https://help.ubuntu.com/lts/serverguide/NTP.html for more detailed comparison of features of `chronyd` and `ntpd` daemon features respectively, and for further guidance how to choose between the two NTP daemons.
The upstream manual pages at https://chrony-project.org/documentation.html for `chronyd` and http://www.ntp.org for `ntpd` provide additional information on the capabilities and configuration of each of the NTP daemons.

#### Rule The Chrony package is installed [ref]

System time should be synchronized between all systems in an environment. This is typically done by establishing an authoritative time server or set of servers and having all systems synchronize their clocks to them. The `chrony` package can be installed with the following command:

    $ apt-get install chrony

Rationale: | Time synchronization is important to support time sensitive security mechanisms like Kerberos and also ensures log files have consistent time records across the enterprise, which aids in forensic investigations.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_package_chrony_installed

References:

disa | CCI-004923
ism | 0988, 1405
ospp | FMT_SMF_EXT.1
pcidss | Req-10.4
os-srg | SRG-OS-000355-GPOS-00143
stigid | UBTU-20-010435
cis | 2.2.1.1
anssi | R71
pcidss4 | 10.6.1, 10.6
stigref | SV-238356r877038_rule

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | enable

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    DEBIAN_FRONTEND=noninteractive apt-get install -y "chrony"

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation OSBuild Blueprint snippet ⇲

    [[packages]]
    name = "chrony"
    version = "*"

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | enable

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - DISA-STIG-UBTU-20-010435
      - PCI-DSS-Req-10.4
      - PCI-DSSv4-10.6
      - PCI-DSSv4-10.6.1
      - enable_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - package_chrony_installed

    - name: Ensure chrony is installed
      package:
        name: chrony
        state: present
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - DISA-STIG-UBTU-20-010435
      - PCI-DSS-Req-10.4
      - PCI-DSSv4-10.6
      - PCI-DSSv4-10.6.1
      - enable_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - package_chrony_installed

Remediation Puppet snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | enable

    include install_chrony

    class install_chrony {
      package { 'chrony':
        ensure => 'installed',
      }
    }

#### Rule The Chronyd service is enabled [ref]

chrony is a daemon which implements the Network Time Protocol (NTP) is designed to synchronize system clocks across a variety of systems and use a source that is highly accurate. More information on chrony can be found at https://chrony-project.org/. Chrony can be configured to be a client and/or a server. To enable Chronyd service, you can run: `# systemctl enable chronyd.service` This recommendation only applies if chrony is in use on the system.

Rationale: | If chrony is in use on the system proper configuration is vital to ensuring time synchronization is working properly.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_service_chronyd_enabled

References:

disa | CCI-004923
ism | 0988, 1405
os-srg | SRG-OS-000355-GPOS-00143
cis | 2.2.1.3

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | enable

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed && { dpkg-query --show --showformat='${db:Status-Status}\n' 'chrony' 2>/dev/null | grep -q '^installed'; }; then

    SYSTEMCTL_EXEC='/usr/bin/systemctl'
    "$SYSTEMCTL_EXEC" unmask 'chrony.service'
    if [[ $("$SYSTEMCTL_EXEC" is-system-running) != "offline" ]]; then
      "$SYSTEMCTL_EXEC" start 'chrony.service'
    fi
    "$SYSTEMCTL_EXEC" enable 'chrony.service'

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation OSBuild Blueprint snippet ⇲

    [customizations.services]
    enabled = ["chrony"]

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | enable

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - enable_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - service_chronyd_enabled

    - name: The Chronyd service is enabled - Enable service chrony
      block:

      - name: Gather the package facts
        package_facts:
          manager: auto

      - name: The Chronyd service is enabled - Enable Service chrony
        ansible.builtin.systemd:
          name: chrony
          enabled: true
          state: started
          masked: false
        when:
        - '"chrony" in ansible_facts.packages'
      when:
      - '"linux-base" in ansible_facts.packages'
      - '"chrony" in ansible_facts.packages'
      tags:
      - enable_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - service_chronyd_enabled

Remediation Puppet snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | enable

    include enable_chrony

    class enable_chrony {
      service {'chrony':
        enable => true,
        ensure => 'running',
      }
    }

#### Rule Enable the NTP Daemon [ref]

The `ntp` service can be enabled with the following command:

    $ sudo systemctl enable ntp.service

Rationale:

Enabling the `ntp` service ensures that the `ntp` service will be running and that the system will synchronize its time to any servers specified. This is important whether the system is configured to be a client (and synchronize only its own clock) or it is also acting as an NTP server to other systems. Synchronizing time is essential for authentication services such as Kerberos, but it is also important for maintaining accurate logs and auditing possible security breaches.
The NTP daemon offers all of the functionality of `ntpdate`, which is now deprecated.

Severity: | high
Rule ID: | xccdf_org.ssgproject.content_rule_service_ntp_enabled

References:

cis-csc | 1, 14, 15, 16, 3, 5, 6
cobit5 | APO11.04, BAI03.05, DSS05.04, DSS05.07, MEA02.01
disa | CCI-000160
isa-62443-2009 | 4.3.3.3.9, 4.3.3.5.8, 4.3.4.4.7, 4.4.2.1, 4.4.2.2, 4.4.2.4
isa-62443-2013 | SR 2.10, SR 2.11, SR 2.12, SR 2.8, SR 2.9
iso27001-2013 | A.12.4.1, A.12.4.2, A.12.4.3, A.12.4.4, A.12.7.1
nist | CM-6(a), AU-8(1)(a)
nist-csf | PR.PT-1
pcidss | Req-10.4
cis | 2.2.1.4
pcidss4 | 10.6.1, 10.6

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | enable

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed && { dpkg-query --show --showformat='${db:Status-Status}\n' 'ntp' 2>/dev/null | grep -q '^installed'; }; then

    SYSTEMCTL_EXEC='/usr/bin/systemctl'
    "$SYSTEMCTL_EXEC" unmask 'ntp.service'
    if [[ $("$SYSTEMCTL_EXEC" is-system-running) != "offline" ]]; then
      "$SYSTEMCTL_EXEC" start 'ntp.service'
    fi
    "$SYSTEMCTL_EXEC" enable 'ntp.service'

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation OSBuild Blueprint snippet ⇲

    [customizations.services]
    enabled = ["ntp"]

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | enable

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - NIST-800-53-AU-8(1)(a)
      - NIST-800-53-CM-6(a)
      - PCI-DSS-Req-10.4
      - PCI-DSSv4-10.6
      - PCI-DSSv4-10.6.1
      - enable_strategy
      - high_severity
      - low_complexity
      - low_disruption
      - no_reboot_needed
      - service_ntp_enabled

    - name: Enable the NTP Daemon - Enable service ntp
      block:

      - name: Gather the package facts
        package_facts:
          manager: auto

      - name: Enable the NTP Daemon - Enable Service ntp
        ansible.builtin.systemd:
          name: ntp
          enabled: true
          state: started
          masked: false
        when:
        - '"ntp" in ansible_facts.packages'
      when:
      - '"linux-base" in ansible_facts.packages'
      - '"ntp" in ansible_facts.packages'
      tags:
      - NIST-800-53-AU-8(1)(a)
      - NIST-800-53-CM-6(a)
      - PCI-DSS-Req-10.4
      - PCI-DSSv4-10.6
      - PCI-DSSv4-10.6.1
      - enable_strategy
      - high_severity
      - low_complexity
      - low_disruption
      - no_reboot_needed
      - service_ntp_enabled

Remediation Puppet snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | enable

    include enable_ntp

    class enable_ntp {
      service {'ntp':
        enable => true,
        ensure => 'running',
      }
    }

#### Rule Enable systemd_timesyncd Service [ref]

The `systemd_timesyncd` service can be enabled with the following command:

    $ sudo systemctl enable systemd_timesyncd.service

Rationale:

Enabling the `systemd_timesyncd` service ensures that this host uses the ntp protocol to fetch time data from a ntp server. Synchronizing time is essential for authentication services such as Kerberos, but it is also important for maintaining accurate logs and auditing possible security breaches.
Additional information on Ubuntu network time protocol is available at https://help.ubuntu.com/lts/serverguide/NTP.html.en.

Severity: | high
Rule ID: | xccdf_org.ssgproject.content_rule_service_timesyncd_enabled

References:

cis-csc | 1, 14, 15, 16, 3, 5, 6
cobit5 | APO11.04, BAI03.05, DSS05.04, DSS05.07, MEA02.01
disa | CCI-000160
isa-62443-2009 | 4.3.3.3.9, 4.3.3.5.8, 4.3.4.4.7, 4.4.2.1, 4.4.2.2, 4.4.2.4
isa-62443-2013 | SR 2.10, SR 2.11, SR 2.12, SR 2.8, SR 2.9
iso27001-2013 | A.12.4.1, A.12.4.2, A.12.4.3, A.12.4.4, A.12.7.1
nist | CM-6(a), AU-8(1)(a)
nist-csf | PR.PT-1
pcidss | Req-10.4
cis | 2.2.1.2
pcidss4 | 10.6.1, 10.6

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | enable

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed && { ( ! ( dpkg-query --show --showformat='${db:Status-Status}\n' 'chrony' 2>/dev/null | grep -q '^installed' ) && ! ( dpkg-query --show --showformat='${db:Status-Status}\n' 'ntp' 2>/dev/null | grep -q '^installed' ) ); }; then

    SYSTEMCTL_EXEC='/usr/bin/systemctl'
    "$SYSTEMCTL_EXEC" unmask 'systemd-timesyncd.service'
    if [[ $("$SYSTEMCTL_EXEC" is-system-running) != "offline" ]]; then
      "$SYSTEMCTL_EXEC" start 'systemd-timesyncd.service'
    fi
    "$SYSTEMCTL_EXEC" enable 'systemd-timesyncd.service'

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation OSBuild Blueprint snippet ⇲

    [customizations.services]
    enabled = ["systemd-timesyncd"]

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | enable

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - NIST-800-53-AU-8(1)(a)
      - NIST-800-53-CM-6(a)
      - PCI-DSS-Req-10.4
      - PCI-DSSv4-10.6
      - PCI-DSSv4-10.6.1
      - enable_strategy
      - high_severity
      - low_complexity
      - low_disruption
      - no_reboot_needed
      - service_timesyncd_enabled

    - name: Enable systemd_timesyncd Service - Enable service systemd-timesyncd
      block:

      - name: Gather the package facts
        package_facts:
          manager: auto

      - name: Enable systemd_timesyncd Service - Enable Service systemd-timesyncd
        ansible.builtin.systemd:
          name: systemd-timesyncd
          enabled: true
          state: started
          masked: false
        when:
        - '"systemd" in ansible_facts.packages'
      when:
      - '"linux-base" in ansible_facts.packages'
      - ( not ( "chrony" in ansible_facts.packages ) and not ( "ntp" in ansible_facts.packages
        ) )
      tags:
      - NIST-800-53-AU-8(1)(a)
      - NIST-800-53-CM-6(a)
      - PCI-DSS-Req-10.4
      - PCI-DSSv4-10.6
      - PCI-DSSv4-10.6.1
      - enable_strategy
      - high_severity
      - low_complexity
      - low_disruption
      - no_reboot_needed
      - service_timesyncd_enabled

Remediation Puppet snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | enable

    include enable_systemd-timesyncd

    class enable_systemd-timesyncd {
      service {'systemd-timesyncd':
        enable => true,
        ensure => 'running',
      }
    }

#### Rule A remote time server for Chrony is configured [ref]

`Chrony` is a daemon which implements the Network Time Protocol (NTP). It is designed to synchronize system clocks across a variety of systems and use a source that is highly accurate. More information on `chrony` can be found at https://chrony-project.org/. `Chrony` can be configured to be a client and/or a server. Add or edit server or pool lines to `/etc/chrony/chrony.conf` as appropriate:

    server <remote-server>

Multiple servers may be configured.

Rationale: | If `chrony` is in use on the system proper configuration is vital to ensuring time synchronization is working properly.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_chronyd_specify_remote_server

References:

disa | CCI-001890, CCI-004926, CCI-004923
ism | 0988, 1405
nist | CM-6(a), AU-8(1)(a)
pcidss | Req-10.4.3
os-srg | SRG-OS-000355-GPOS-00143
cis | 2.2.1.3
anssi | R71
pcidss4 | 10.6.2, 10.6

Remediation Shell script ⇲

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed && { dpkg-query --show --showformat='${db:Status-Status}\n' 'chrony' 2>/dev/null | grep -q '^installed'; }; then

    var_multiple_time_servers='0.pool.ntp.org,1.pool.ntp.org,2.pool.ntp.org,3.pool.ntp.org'

    config_file="/etc/chrony/chrony.conf"

    if ! grep -q '^[[:space:]]*\(server\|pool\)[[:space:]]\+[[:graph:]]\+' "$config_file" ; then
      if ! grep -q '#[[:space:]]*server' "$config_file" ; then
        for server in $(echo "$var_multiple_time_servers" | tr ',' '\n') ; do
          printf '\nserver %s' "$server" >> "$config_file"
        done
      else
        sed -i 's/#[ \t]*server/server/g' "$config_file"
      fi
    fi

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - NIST-800-53-AU-8(1)(a)
      - NIST-800-53-CM-6(a)
      - PCI-DSS-Req-10.4.3
      - PCI-DSSv4-10.6
      - PCI-DSSv4-10.6.2
      - chronyd_specify_remote_server
      - configure_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
    - name: XCCDF Value var_multiple_time_servers # promote to variable
      set_fact:
        var_multiple_time_servers: !!str 0.pool.ntp.org,1.pool.ntp.org,2.pool.ntp.org,3.pool.ntp.org
      tags:
        - always

    - name: Detect if chrony is already configured with pools or servers
      find:
        path: /etc
        patterns: chrony.conf
        contains: ^[\s]*(?:server|pool)[\s]+[\w]+
      register: chrony_servers
      when:
      - '"linux-base" in ansible_facts.packages'
      - '"chrony" in ansible_facts.packages'
      tags:
      - NIST-800-53-AU-8(1)(a)
      - NIST-800-53-CM-6(a)
      - PCI-DSS-Req-10.4.3
      - PCI-DSSv4-10.6
      - PCI-DSSv4-10.6.2
      - chronyd_specify_remote_server
      - configure_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Configure remote time servers
      lineinfile:
        path: /etc/chrony/chrony.conf
        line: server {{ item }}
        state: present
        create: true
      loop: '{{ var_multiple_time_servers.split(",") }}'
      when:
      - '"linux-base" in ansible_facts.packages'
      - '"chrony" in ansible_facts.packages'
      - chrony_servers.matched == 0
      tags:
      - NIST-800-53-AU-8(1)(a)
      - NIST-800-53-CM-6(a)
      - PCI-DSS-Req-10.4.3
      - PCI-DSSv4-10.6
      - PCI-DSSv4-10.6.2
      - chronyd_specify_remote_server
      - configure_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

#### Rule Ensure that chronyd is running under chrony user account [ref]

chrony is a daemon which implements the Network Time Protocol (NTP). It is designed to synchronize system clocks across a variety of systems and use a source that is highly accurate. More information on chrony can be found at https://chrony-project.org/. Chrony can be configured to be a client and/or a server. To ensure that chronyd is running under chrony user account, `user` variable in `/etc/chrony/chrony.conf` is set to `_chrony` or is absent:

    user _chrony

This recommendation only applies if chrony is in use on the system.

Rationale: | If chrony is in use on the system proper configuration is vital to ensuring time synchronization is working properly.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_chronyd_run_as_chrony_user

References:

cis | 2.2.1.3
pcidss4 | 10.6.3, 10.6

Remediation Shell script ⇲

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed && { dpkg-query --show --showformat='${db:Status-Status}\n' 'chrony' 2>/dev/null | grep -q '^installed'; }; then

    # Strip any search characters in the key arg so that the key can be replaced without
    # adding any search characters to the config file.
    stripped_key=$(sed 's/[\^=\$,;+]*//g' <<< "^user")

    # shellcheck disable=SC2059
    printf -v formatted_output "%s %s" "$stripped_key" "_chrony"

    # If the key exists, change it. Otherwise, add it to the config_file.
    # We search for the key string followed by a word boundary (matched by \>),
    # so if we search for 'setting', 'setting2' won't match.
    if LC_ALL=C grep -q -m 1 -i -e "^user\\>" "/etc/chrony/chrony.conf"; then
        escaped_formatted_output=$(sed -e 's|/|\\/|g' <<< "$formatted_output")
        LC_ALL=C sed -i --follow-symlinks "s/^user\\>.*/$escaped_formatted_output/gi" "/etc/chrony/chrony.conf"
    else
        if [[ -s "/etc/chrony/chrony.conf" ]] && [[ -n "$(tail -c 1 -- "/etc/chrony/chrony.conf" || true)" ]]; then
            LC_ALL=C sed -i --follow-symlinks '$a'\\ "/etc/chrony/chrony.conf"
        fi
        printf '%s\n' "$formatted_output" >> "/etc/chrony/chrony.conf"
    fi

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

#### Rule Configure server restrictions for ntpd [ref]

ntpd is a daemon which implements the Network Time Protocol (NTP). It is designed to synchronize system clocks across a variety of systems and use a source that is highly accurate. More information on NTP can be found at http://www.ntp.org. ntp can be configured to be a client and/or a server. To ensure that ntpd implements correct server restrictions, make sure that the following lines exist in the file `/etc/ntpd.conf`:

    restrict -4 default kod nomodify notrap nopeer noquery

    restrict -6 default kod nomodify notrap nopeer noquery

This recommendation only applies if ntp is in use on the system.

Rationale: | If ntp is in use on the system proper configuration is vital to ensuring time synchronization is working properly.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_ntpd_configure_restrictions

References:

cis | 2.2.1.4

Remediation Shell script ⇲

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed && { dpkg-query --show --showformat='${db:Status-Status}\n' 'ntp' 2>/dev/null | grep -q '^installed'; }; then

    if [ -e "/etc/ntp.conf" ] ; then

        LC_ALL=C sed -i "/^\s*restrict \-4\s\+/Id" "/etc/ntp.conf"
    else
        touch "/etc/ntp.conf"
    fi
    # make sure file has newline at the end
    sed -i -e '$a\' "/etc/ntp.conf"

    cp "/etc/ntp.conf" "/etc/ntp.conf.bak"
    # Insert at the end of the file
    printf '%s\n' "restrict -4 default kod nomodify notrap nopeer noquery" >> "/etc/ntp.conf"
    # Clean up after ourselves.
    rm "/etc/ntp.conf.bak"
    if [ -e "/etc/ntp.conf" ] ; then

        LC_ALL=C sed -i "/^\s*restrict \-6\s\+/Id" "/etc/ntp.conf"
    else
        touch "/etc/ntp.conf"
    fi
    # make sure file has newline at the end
    sed -i -e '$a\' "/etc/ntp.conf"

    cp "/etc/ntp.conf" "/etc/ntp.conf.bak"
    # Insert at the end of the file
    printf '%s\n' "restrict -6 default kod nomodify notrap nopeer noquery" >> "/etc/ntp.conf"
    # Clean up after ourselves.
    rm "/etc/ntp.conf.bak"

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

#### Rule Configure ntpd To Run As ntp User [ref]

ntp is a daemon which implements the Network Time Protocol (NTP). It is designed to synchronize system clocks across a variety of systems and use a source that is highly accurate. More information on NTP can be found at http://www.ntp.org. ntp can be configured to be a client and/or a server. To ensure that ntpd is running as ntp user, Add or edit the `OPTIONS` variable in `/etc/sysconfig/ntpd` to include ' -u ntp:ntp ':

    OPTIONS="-u ntp:ntp"

This recommendation only applies if ntp is in use on the system.

Rationale: | If ntp is in use on the system proper configuration is vital to ensuring time synchronization is working properly. Running ntpd under dedicated user accounts limits the attack surface for potential attacker exploiting security flaws in the daemon or the protocol.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_ntpd_run_as_ntp_user

References:

cis | 2.2.1.4

Remediation Shell script ⇲

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed && { dpkg-query --show --showformat='${db:Status-Status}\n' 'ntp' 2>/dev/null | grep -q '^installed'; }; then

    if grep -q 'OPTIONS=.*' /etc/sysconfig/ntpd; then
    	# trying to solve cases where the parameter after OPTIONS
    	#may or may not be enclosed in quotes
    	sed -i -E 's/^([\s]*OPTIONS=["]?[^"]*)("?)/\1 -u ntp:ntp\2/' /etc/sysconfig/ntpd
    else
    	echo 'OPTIONS="-u ntp:ntp"' >> /etc/sysconfig/ntpd
    fi

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Group Obsolete Services Group contains 4 groups and 6 rules

[ref] This section discusses a number of network-visible services which have historically caused problems for system security, and for which disabling or severely limiting the service has been the best available guidance for some time. As a result of this, many of these services are not installed as part of Ubuntu 20.04 by default.
Organizations which are running these services should switch to more secure equivalents as soon as possible. If it remains absolutely necessary to run one of these services for legacy reasons, care should be taken to restrict the service as much as possible, for instance by configuring host firewall software such as `iptables` to restrict access to the vulnerable service to only those remote hosts which have a known need to use it.

Group Xinetd Group contains 1 rule
[ref] The `xinetd` service acts as a dedicated listener for some network services (mostly, obsolete ones) and can be used to provide access controls and perform some logging. It has been largely obsoleted by other features, and it is not installed by default. The older Inetd service is not even available as part of Ubuntu 20.04.

#### Rule Uninstall xinetd Package [ref]

The `xinetd` package can be removed with the following command:

    $ apt-get remove xinetd

Rationale: | Removing the `xinetd` package decreases the risk of the xinetd service's accidental (or intentional) activation.
Severity: | low
Rule ID: | xccdf_org.ssgproject.content_rule_package_xinetd_removed

References:

cis-csc | 11, 12, 14, 15, 3, 8, 9
cobit5 | APO13.01, BAI10.01, BAI10.02, BAI10.03, BAI10.05, DSS01.04, DSS05.02, DSS05.03, DSS05.05, DSS06.06
disa | CCI-000305
hipaa | 164.308(a)(4)(i), 164.308(b)(1), 164.308(b)(3), 164.310(b), 164.312(e)(1), 164.312(e)(2)(ii)
isa-62443-2009 | 4.3.3.5.1, 4.3.3.5.2, 4.3.3.5.3, 4.3.3.5.4, 4.3.3.5.5, 4.3.3.5.6, 4.3.3.5.7, 4.3.3.5.8, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.1, 4.3.3.7.2, 4.3.3.7.3, 4.3.3.7.4, 4.3.4.3.2, 4.3.4.3.3
isa-62443-2013 | SR 1.1, SR 1.10, SR 1.11, SR 1.12, SR 1.13, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.6, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 2.2, SR 2.3, SR 2.4, SR 2.5, SR 2.6, SR 2.7, SR 3.1, SR 3.5, SR 3.8, SR 4.1, SR 4.3, SR 5.1, SR 5.2, SR 5.3, SR 7.1, SR 7.6
iso27001-2013 | A.11.2.6, A.12.1.2, A.12.5.1, A.12.6.2, A.13.1.1, A.13.2.1, A.14.1.3, A.14.2.2, A.14.2.3, A.14.2.4, A.6.2.1, A.6.2.2, A.9.1.2
nist | CM-7(a), CM-7(b), CM-6(a)
nist-csf | PR.AC-3, PR.IP-1, PR.PT-3, PR.PT-4
cis | 2.1.1
anssi | R62
pcidss4 | 2.2.4, 2.2

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    # CAUTION: This remediation script will remove xinetd
    #	   from the system, and may remove any packages
    #	   that depend on xinetd. Execute this
    #	   remediation AFTER testing on a non-production
    #	   system!

    DEBIAN_FRONTEND=noninteractive apt-get remove -y "xinetd"

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.4
      - disable_strategy
      - low_complexity
      - low_disruption
      - low_severity
      - no_reboot_needed
      - package_xinetd_removed

    - name: Ensure xinetd is removed
      package:
        name: xinetd
        state: absent
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.4
      - disable_strategy
      - low_complexity
      - low_disruption
      - low_severity
      - no_reboot_needed
      - package_xinetd_removed

Remediation Puppet snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    include remove_xinetd

    class remove_xinetd {
      package { 'xinetd':
        ensure => 'purged',
      }
    }

Group Rlogin, Rsh, and Rexec Group contains 2 rules
[ref] The Berkeley r-commands are legacy services which allow cleartext remote access and have an insecure trust model.

#### Rule Uninstall rsh Package [ref]

The `rsh-client` package contains the client commands for the rsh services

Rationale:

These legacy clients contain numerous security exposures and have been replaced with the more secure SSH package. Even if the server is removed, it is best to ensure the clients are also removed to prevent users from inadvertently attempting to use these commands and therefore exposing their credentials. Note that removing the `rsh-client` package removes the clients for `rsh`,`rcp`, and `rlogin`.

Severity: | unknown
Rule ID: | xccdf_org.ssgproject.content_rule_package_rsh_removed

References:

cui | 3.1.13
hipaa | 164.308(a)(4)(i), 164.308(b)(1), 164.308(b)(3), 164.310(b), 164.312(e)(1), 164.312(e)(2)(ii)
iso27001-2013 | A.8.2.3, A.13.1.1, A.13.2.1, A.13.2.3, A.14.1.2, A.14.1.3
cis | 2.3.2
anssi | R62
pcidss4 | 2.2.4, 2.2

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    # CAUTION: This remediation script will remove rsh-client
    #	   from the system, and may remove any packages
    #	   that depend on rsh-client. Execute this
    #	   remediation AFTER testing on a non-production
    #	   system!

    DEBIAN_FRONTEND=noninteractive apt-get remove -y "rsh-client"

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    - name: Ensure rsh-client is removed
      package:
        name: rsh-client
        state: absent
      tags:
      - NIST-800-171-3.1.13
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.4
      - disable_strategy
      - low_complexity
      - low_disruption
      - no_reboot_needed
      - package_rsh_removed
      - unknown_severity

Remediation Puppet snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    include remove_rsh-client

    class remove_rsh-client {
      package { 'rsh-client':
        ensure => 'purged',
      }
    }

#### Rule Remove Rsh Trust Files [ref]

The files `/etc/hosts.equiv` and `~/.rhosts` (in each user's home directory) list remote hosts and users that are trusted by the local system when using the rshd daemon. To remove these files, run the following command to delete them from any location:

    $ sudo rm /etc/hosts.equiv

    $ rm ~/.rhosts

Rationale: | This action is only meaningful if `.rhosts` support is permitted through PAM. Trust files are convenient, but when used in conjunction with the R-services, they can allow unauthenticated access to a system.
Severity: | high
Rule ID: | xccdf_org.ssgproject.content_rule_no_rsh_trust_files

References:

cis-csc | 11, 12, 14, 15, 3, 8, 9
cobit5 | APO13.01, BAI10.01, BAI10.02, BAI10.03, BAI10.05, DSS01.04, DSS05.02, DSS05.03, DSS05.05, DSS06.06
disa | CCI-001436
hipaa | 164.308(a)(4)(i), 164.308(b)(1), 164.308(b)(3), 164.310(b), 164.312(e)(1), 164.312(e)(2)(ii)
isa-62443-2009 | 4.3.3.5.1, 4.3.3.5.2, 4.3.3.5.3, 4.3.3.5.4, 4.3.3.5.5, 4.3.3.5.6, 4.3.3.5.7, 4.3.3.5.8, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.1, 4.3.3.7.2, 4.3.3.7.3, 4.3.3.7.4, 4.3.4.3.2, 4.3.4.3.3
isa-62443-2013 | SR 1.1, SR 1.10, SR 1.11, SR 1.12, SR 1.13, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.6, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 2.2, SR 2.3, SR 2.4, SR 2.5, SR 2.6, SR 2.7, SR 3.1, SR 3.5, SR 3.8, SR 4.1, SR 4.3, SR 5.1, SR 5.2, SR 5.3, SR 7.1, SR 7.6
iso27001-2013 | A.11.2.6, A.12.1.2, A.12.5.1, A.12.6.2, A.13.1.1, A.13.2.1, A.14.1.3, A.14.2.2, A.14.2.3, A.14.2.4, A.6.2.1, A.6.2.2, A.9.1.2
nist | CM-7(a), CM-7(b), CM-6(a)
nist-csf | PR.AC-3, PR.IP-1, PR.PT-3, PR.PT-4
cis | 6.2.11

Remediation Shell script ⇲

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}\n' 'rsh-server' 2>/dev/null | grep -q '^installed'; then

    find /root -xdev -type f -name ".rhosts" -exec rm -f {} \;
    find /home -maxdepth 2 -xdev -type f -name ".rhosts" -exec rm -f {} \;
    rm -f /etc/hosts.equiv

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Group Chat/Messaging Services Group contains 1 rule
[ref] The talk software makes it possible for users to send and receive messages across systems through a terminal session.

#### Rule Uninstall talk Package [ref]

The `talk` package contains the client program for the Internet talk protocol, which allows the user to chat with other users on different systems. Talk is a communication program which copies lines from one terminal to the terminal of another user. The `talk` package can be removed with the following command:

    $ apt-get remove talk

Rationale: | The talk software presents a security risk as it uses unencrypted protocols for communications. Removing the `talk` package decreases the risk of the accidental (or intentional) activation of talk client program.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_package_talk_removed

References:

hipaa | 164.308(a)(4)(i), 164.308(b)(1), 164.308(b)(3), 164.310(b), 164.312(e)(1), 164.312(e)(2)(ii)
cis | 2.3.3
anssi | R62
pcidss4 | 2.2.4, 2.2

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    # CAUTION: This remediation script will remove talk
    #	   from the system, and may remove any packages
    #	   that depend on talk. Execute this
    #	   remediation AFTER testing on a non-production
    #	   system!

    DEBIAN_FRONTEND=noninteractive apt-get remove -y "talk"

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    - name: Ensure talk is removed
      package:
        name: talk
        state: absent
      tags:
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.4
      - disable_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - package_talk_removed

Remediation Puppet snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    include remove_talk

    class remove_talk {
      package { 'talk':
        ensure => 'purged',
      }
    }

Group Telnet Group contains 1 rule
[ref] The telnet protocol does not provide confidentiality or integrity for information transmitted on the network. This includes authentication information such as passwords. Organizations which use telnet should be actively working to migrate to a more secure protocol.

#### Rule Remove telnet Clients [ref]

The telnet client allows users to start connections to other systems via the telnet protocol.
Rationale: | The `telnet` protocol is insecure and unencrypted. The use of an unencrypted transmission medium could allow an unauthorized user to steal credentials. The `ssh` package provides an encrypted session and stronger security and is included in Ubuntu 20.04.
Severity: | low
Rule ID: | xccdf_org.ssgproject.content_rule_package_telnet_removed

References:

cui | 3.1.13
hipaa | 164.308(a)(4)(i), 164.308(b)(1), 164.308(b)(3), 164.310(b), 164.312(e)(1), 164.312(e)(2)(ii)
iso27001-2013 | A.8.2.3, A.13.1.1, A.13.2.1, A.13.2.3, A.14.1.2, A.14.1.3
cis | 2.3.4
anssi | R62
pcidss4 | 2.2.4, 2.2

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    # CAUTION: This remediation script will remove telnet
    #	   from the system, and may remove any packages
    #	   that depend on telnet. Execute this
    #	   remediation AFTER testing on a non-production
    #	   system!

    DEBIAN_FRONTEND=noninteractive apt-get remove -y "telnet"

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    - name: Ensure telnet is removed
      package:
        name: telnet
        state: absent
      tags:
      - NIST-800-171-3.1.13
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.4
      - disable_strategy
      - low_complexity
      - low_disruption
      - low_severity
      - no_reboot_needed
      - package_telnet_removed

Remediation Puppet snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    include remove_telnet

    class remove_telnet {
      package { 'telnet':
        ensure => 'purged',
      }
    }

#### Rule Uninstall rsync Package [ref]

The rsyncd service can be used to synchronize files between systems over network links. The `rsync` package can be removed with the following command:

    $ apt-get remove rsync

Rationale: | The rsyncd service presents a security risk as it uses unencrypted protocols for communication.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_package_rsync_removed

References:

cis | 2.2.16

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    # CAUTION: This remediation script will remove rsync
    #	   from the system, and may remove any packages
    #	   that depend on rsync. Execute this
    #	   remediation AFTER testing on a non-production
    #	   system!

    DEBIAN_FRONTEND=noninteractive apt-get remove -y "rsync"

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    - name: Ensure rsync is removed
      package:
        name: rsync
        state: absent
      tags:
      - disable_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - package_rsync_removed

Remediation Puppet snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    include remove_rsync

    class remove_rsync {
      package { 'rsync':
        ensure => 'purged',
      }
    }

Group Print Support Group contains 2 rules

[ref] The Common Unix Printing System (CUPS) service provides both local and network printing support. A system running the CUPS service can accept print jobs from other systems, process them, and send them to the appropriate printer. It also provides an interface for remote administration through a web browser. The CUPS service is installed and activated by default. The project homepage and more detailed documentation are available at http://www.cups.org.

#### Rule Uninstall CUPS Package [ref]

The `cups` package can be removed with the following command:

    $ apt-get remove cups

Rationale: | If the system does not need to print jobs or accept print jobs from other systems, it is recommended that CUPS be removed to reduce the potential attack surface.
Severity: | unknown
Rule ID: | xccdf_org.ssgproject.content_rule_package_cups_removed

References:

cis-csc | 11, 14, 3, 9
cobit5 | BAI10.01, BAI10.02, BAI10.03, BAI10.05, DSS05.02, DSS05.05, DSS06.06
isa-62443-2009 | 4.3.3.5.1, 4.3.3.5.2, 4.3.3.5.3, 4.3.3.5.4, 4.3.3.5.5, 4.3.3.5.6, 4.3.3.5.7, 4.3.3.5.8, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.1, 4.3.3.7.2, 4.3.3.7.3, 4.3.3.7.4, 4.3.4.3.2, 4.3.4.3.3
isa-62443-2013 | SR 1.1, SR 1.10, SR 1.11, SR 1.12, SR 1.13, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.6, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 2.2, SR 2.3, SR 2.4, SR 2.5, SR 2.6, SR 2.7, SR 7.6
iso27001-2013 | A.12.1.2, A.12.5.1, A.12.6.2, A.14.2.2, A.14.2.3, A.14.2.4, A.9.1.2
nist | CM-7(a), CM-7(b), CM-6(a)
nist-csf | PR.IP-1, PR.PT-3
cis | 2.2.4

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    # CAUTION: This remediation script will remove cups
    #	   from the system, and may remove any packages
    #	   that depend on cups. Execute this
    #	   remediation AFTER testing on a non-production
    #	   system!

    DEBIAN_FRONTEND=noninteractive apt-get remove -y "cups"

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    - name: Ensure cups is removed
      package:
        name: cups
        state: absent
      tags:
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - disable_strategy
      - low_complexity
      - low_disruption
      - no_reboot_needed
      - package_cups_removed
      - unknown_severity

Remediation Puppet snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    include remove_cups

    class remove_cups {
      package { 'cups':
        ensure => 'purged',
      }
    }

#### Rule Disable the CUPS Service [ref]

The `cups` service can be disabled with the following command:

    $ sudo systemctl mask --now cups.service

Rationale: | Turn off unneeded services to reduce attack surface.
Severity: | unknown
Rule ID: | xccdf_org.ssgproject.content_rule_service_cups_disabled

References:

cis-csc | 11, 14, 3, 9
cobit5 | BAI10.01, BAI10.02, BAI10.03, BAI10.05, DSS05.02, DSS05.05, DSS06.06
isa-62443-2009 | 4.3.3.5.1, 4.3.3.5.2, 4.3.3.5.3, 4.3.3.5.4, 4.3.3.5.5, 4.3.3.5.6, 4.3.3.5.7, 4.3.3.5.8, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.1, 4.3.3.7.2, 4.3.3.7.3, 4.3.3.7.4, 4.3.4.3.2, 4.3.4.3.3
isa-62443-2013 | SR 1.1, SR 1.10, SR 1.11, SR 1.12, SR 1.13, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.6, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 2.2, SR 2.3, SR 2.4, SR 2.5, SR 2.6, SR 2.7, SR 7.6
iso27001-2013 | A.12.1.2, A.12.5.1, A.12.6.2, A.14.2.2, A.14.2.3, A.14.2.4, A.9.1.2
nist | CM-7(a), CM-7(b), CM-6(a)
nist-csf | PR.IP-1, PR.PT-3
cis | 2.2.4

Remediation Kubernetes snippet ⇲

Complexity: | low
Disruption: | medium
Reboot: | true
Strategy: | disable

    apiVersion: machineconfiguration.openshift.io/v1
    kind: MachineConfig
    spec:
      config:
        ignition:
          version: 3.1.0
        systemd:
          units:
          - name: cups.service
            enabled: false
            mask: true
          - name: cups.socket
            enabled: false
            mask: true

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    SYSTEMCTL_EXEC='/usr/bin/systemctl'
    if [[ $("$SYSTEMCTL_EXEC" is-system-running) != "offline" ]]; then
      "$SYSTEMCTL_EXEC" stop 'cups.service'
    fi
    "$SYSTEMCTL_EXEC" disable 'cups.service'
    "$SYSTEMCTL_EXEC" mask 'cups.service'
    # Disable socket activation if we have a unit file for it
    if "$SYSTEMCTL_EXEC" -q list-unit-files cups.socket; then
        if [[ $("$SYSTEMCTL_EXEC" is-system-running) != "offline" ]]; then
          "$SYSTEMCTL_EXEC" stop 'cups.socket'
        fi
        "$SYSTEMCTL_EXEC" mask 'cups.socket'
    fi
    # The service may not be running because it has been started and failed,
    # so let's reset the state so OVAL checks pass.
    # Service should be 'inactive', not 'failed' after reboot though.
    "$SYSTEMCTL_EXEC" reset-failed 'cups.service' || true

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation OSBuild Blueprint snippet ⇲

    [customizations.services]
    masked = ["cups"]

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - disable_strategy
      - low_complexity
      - low_disruption
      - no_reboot_needed
      - service_cups_disabled
      - unknown_severity

    - name: Disable the CUPS Service - Collect systemd Services Present in the System
      ansible.builtin.command: systemctl -q list-unit-files --type service
      register: service_exists
      changed_when: false
      failed_when: service_exists.rc not in [0, 1]
      check_mode: false
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - disable_strategy
      - low_complexity
      - low_disruption
      - no_reboot_needed
      - service_cups_disabled
      - unknown_severity

    - name: Disable the CUPS Service - Ensure cups.service is Masked
      ansible.builtin.systemd:
        name: cups.service
        state: stopped
        enabled: false
        masked: true
      when:
      - '"linux-base" in ansible_facts.packages'
      - service_exists.stdout_lines is search("cups.service", multiline=True)
      tags:
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - disable_strategy
      - low_complexity
      - low_disruption
      - no_reboot_needed
      - service_cups_disabled
      - unknown_severity

    - name: Unit Socket Exists - cups.socket
      ansible.builtin.command: systemctl -q list-unit-files cups.socket
      register: socket_file_exists
      changed_when: false
      failed_when: socket_file_exists.rc not in [0, 1]
      check_mode: false
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - disable_strategy
      - low_complexity
      - low_disruption
      - no_reboot_needed
      - service_cups_disabled
      - unknown_severity

    - name: Disable the CUPS Service - Disable Socket cups
      ansible.builtin.systemd:
        name: cups.socket
        enabled: false
        state: stopped
        masked: true
      when:
      - '"linux-base" in ansible_facts.packages'
      - socket_file_exists.stdout_lines is search("cups.socket", multiline=True)
      tags:
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - disable_strategy
      - low_complexity
      - low_disruption
      - no_reboot_needed
      - service_cups_disabled
      - unknown_severity

Remediation Puppet snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | enable

    include disable_cups

    class disable_cups {
      service {'cups':
        enable => false,
        ensure => 'stopped',
      }
    }

Group Proxy Server Group contains 1 group and 1 rule

[ref] A proxy server is a very desirable target for a potential adversary because much (or all) sensitive data for a given infrastructure may flow through it. Therefore, if one is required, the system acting as a proxy server should be dedicated to that purpose alone and be stored in a physically secure location. The system's default proxy server software is Squid, and provided in an RPM package of the same name.

Group Disable Squid if Possible Group contains 1 rule
[ref] If Squid was installed and activated, but the system does not need to act as a proxy server, then it should be disabled and removed.

#### Rule Uninstall squid Package [ref]

The `squid` package can be removed with the following command:

     $ apt-get remove squid

Rationale: | If there is no need to make the proxy server software available, removing it provides a safeguard against its activation.
Severity: | unknown
Rule ID: | xccdf_org.ssgproject.content_rule_package_squid_removed

References:

cis | 2.2.13

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    # CAUTION: This remediation script will remove squid
    #	   from the system, and may remove any packages
    #	   that depend on squid. Execute this
    #	   remediation AFTER testing on a non-production
    #	   system!

    DEBIAN_FRONTEND=noninteractive apt-get remove -y "squid"

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    - name: Ensure squid is removed
      package:
        name: squid
        state: absent
      tags:
      - disable_strategy
      - low_complexity
      - low_disruption
      - no_reboot_needed
      - package_squid_removed
      - unknown_severity

Remediation Puppet snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    include remove_squid

    class remove_squid {
      package { 'squid':
        ensure => 'purged',
      }
    }

Group Samba(SMB) Microsoft Windows File Sharing Server Group contains 1 group and 1 rule

[ref] When properly configured, the Samba service allows Linux systems to provide file and print sharing to Microsoft Windows systems. There are two software packages that provide Samba support. The first, `samba-client`, provides a series of command line tools that enable a client system to access Samba shares. The second, simply labeled `samba`, provides the Samba service. It is this second package that allows a Linux system to act as an Active Directory server, a domain controller, or as a domain member. Only the `samba-client` package is installed by default.

Group Disable Samba if Possible Group contains 1 rule
[ref] Even after the Samba server package has been installed, it will remain disabled. Do not enable this service unless it is absolutely necessary to provide Microsoft Windows file and print sharing functionality.

#### Rule Uninstall Samba Package [ref]

The `samba` package can be removed with the following command:

     $ apt-get remove samba

Rationale: | If there is no need to make the Samba software available, removing it provides a safeguard against its activation.
Severity: | unknown
Rule ID: | xccdf_org.ssgproject.content_rule_package_samba_removed

References:

cis | 2.2.12

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    # CAUTION: This remediation script will remove samba
    #	   from the system, and may remove any packages
    #	   that depend on samba. Execute this
    #	   remediation AFTER testing on a non-production
    #	   system!

    DEBIAN_FRONTEND=noninteractive apt-get remove -y "samba"

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    - name: Ensure samba is removed
      package:
        name: samba
        state: absent
      tags:
      - disable_strategy
      - low_complexity
      - low_disruption
      - no_reboot_needed
      - package_samba_removed
      - unknown_severity

Remediation Puppet snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    include remove_samba

    class remove_samba {
      package { 'samba':
        ensure => 'purged',
      }
    }

Group SNMP Server Group contains 1 group and 1 rule
[ref] The Simple Network Management Protocol allows administrators to monitor the state of network devices, including computers. Older versions of SNMP were well-known for weak security, such as plaintext transmission of the community string (used for authentication) and usage of easily-guessable choices for the community string.
Group Disable SNMP Server if Possible Group contains 1 rule
[ref] The system includes an SNMP daemon that allows for its remote monitoring, though it not installed by default. If it was installed and activated but is not needed, the software should be disabled and removed.

#### Rule Uninstall net-snmp Package [ref]

The `snmp` package provides the snmpd service. The `snmp` package can be removed with the following command:

    $ apt-get remove snmp

Rationale: | If there is no need to run SNMP server software, removing the package provides a safeguard against its activation.
Severity: | unknown
Rule ID: | xccdf_org.ssgproject.content_rule_package_net-snmp_removed

References:

cis | 2.2.14
pcidss4 | 2.2.4, 2.2

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    # CAUTION: This remediation script will remove snmp
    #	   from the system, and may remove any packages
    #	   that depend on snmp. Execute this
    #	   remediation AFTER testing on a non-production
    #	   system!

    DEBIAN_FRONTEND=noninteractive apt-get remove -y "snmp"

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    - name: Ensure snmp is removed
      package:
        name: snmp
        state: absent
      tags:
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.4
      - disable_strategy
      - low_complexity
      - low_disruption
      - no_reboot_needed
      - package_net-snmp_removed
      - unknown_severity

Remediation Puppet snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    include remove_snmp

    class remove_snmp {
      package { 'snmp':
        ensure => 'purged',
      }
    }

Group SSH Server Group contains 1 group and 23 rules

[ref] The SSH protocol is recommended for remote login and remote file transfer. SSH provides confidentiality and integrity for data exchanged between two systems, as well as server authentication, through the use of public key cryptography. The implementation included with the system is called OpenSSH, and more detailed documentation is available from its website, https://www.openssh.com. Its server program is called `sshd` and provided by the RPM package `openssh-server`.

Group Configure OpenSSH Server if Necessary Group contains 18 rules
[ref] If the system needs to act as an SSH server, then certain changes should be made to the OpenSSH daemon configuration file `/etc/ssh/sshd_config`. The following recommendations can be applied to this file. See the `sshd_config(5)` man page for more detailed information.

#### Rule Set SSH Client Alive Count Max [ref]

The SSH server sends at most `ClientAliveCountMax` messages during a SSH session and waits for a response from the SSH client. The option `ClientAliveInterval` configures timeout after each `ClientAliveCountMax` message. If the SSH server does not receive a response from the client, then the connection is considered unresponsive and terminated. For SSH earlier than v8.2, a `ClientAliveCountMax` value of `0` causes a timeout precisely when the `ClientAliveInterval` is set. Starting with v8.2, a value of `0` disables the timeout functionality completely. If the option is set to a number greater than `0`, then the session will be disconnected after `ClientAliveInterval * ClientAliveCountMax` seconds without receiving a keep alive message.

Rationale: | This ensures a user login will be terminated as soon as the `ClientAliveInterval` is reached.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_sshd_set_keepalive

References:

cis-csc | 1, 12, 13, 14, 15, 16, 18, 3, 5, 7, 8
cjis | 5.5.6
cobit5 | APO13.01, BAI03.01, BAI03.02, BAI03.03, DSS01.03, DSS03.05, DSS05.04, DSS05.05, DSS05.07, DSS05.10, DSS06.03, DSS06.10
cui | 3.1.11
disa | CCI-001133, CCI-002361
hipaa | 164.308(a)(4)(i), 164.308(b)(1), 164.308(b)(3), 164.310(b), 164.312(e)(1), 164.312(e)(2)(ii)
isa-62443-2009 | 4.3.3.2.2, 4.3.3.5.1, 4.3.3.5.2, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.2, 4.3.3.7.3, 4.3.3.7.4, 4.3.4.3.3
isa-62443-2013 | SR 1.1, SR 1.10, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 6.2
iso27001-2013 | A.12.4.1, A.12.4.3, A.14.1.1, A.14.2.1, A.14.2.5, A.18.1.4, A.6.1.2, A.6.1.5, A.7.1.1, A.9.1.2, A.9.2.1, A.9.2.2, A.9.2.3, A.9.2.4, A.9.2.6, A.9.3.1, A.9.4.1, A.9.4.2, A.9.4.3, A.9.4.4, A.9.4.5
nerc-cip | CIP-004-6 R2.2.3, CIP-007-3 R5.1, CIP-007-3 R5.2, CIP-007-3 R5.3.1, CIP-007-3 R5.3.2, CIP-007-3 R5.3.3
nist | AC-2(5), AC-12, AC-17(a), SC-10, CM-6(a)
nist-csf | DE.CM-1, DE.CM-3, PR.AC-1, PR.AC-4, PR.AC-6, PR.AC-7, PR.IP-2
pcidss | Req-8.1.8
os-srg | SRG-OS-000163-GPOS-00072, SRG-OS-000279-GPOS-00109
stigid | UBTU-20-010036
cis | 5.2.15
pcidss4 | 8.2.8, 8.2
stigref | SV-238212r951466_rule

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | restrict

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    var_sshd_set_keepalive='3'

    mkdir -p /etc/ssh/sshd_config.d
    touch /etc/ssh/sshd_config.d/00-complianceascode-hardening.conf
    chmod 0600 /etc/ssh/sshd_config.d/00-complianceascode-hardening.conf

    LC_ALL=C sed -i "/^\s*ClientAliveCountMax\s\+/Id" "/etc/ssh/sshd_config"
    LC_ALL=C sed -i "/^\s*ClientAliveCountMax\s\+/Id" "/etc/ssh/sshd_config.d"/*.conf
    if [ -e "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf" ] ; then

        LC_ALL=C sed -i "/^\s*ClientAliveCountMax\s\+/Id" "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf"
    else
        touch "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf"
    fi
    # make sure file has newline at the end
    sed -i -e '$a\' "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf"

    cp "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf" "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf.bak"
    # Insert at the beginning of the file
    printf '%s\n' "ClientAliveCountMax $var_sshd_set_keepalive" > "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf"
    cat "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf.bak" >> "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf"
    # Clean up after ourselves.
    rm "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf.bak"

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | restrict

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - CJIS-5.5.6
      - DISA-STIG-UBTU-20-010036
      - NIST-800-171-3.1.11
      - NIST-800-53-AC-12
      - NIST-800-53-AC-17(a)
      - NIST-800-53-AC-2(5)
      - NIST-800-53-CM-6(a)
      - NIST-800-53-SC-10
      - PCI-DSS-Req-8.1.8
      - PCI-DSSv4-8.2
      - PCI-DSSv4-8.2.8
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy
      - sshd_set_keepalive
    - name: XCCDF Value var_sshd_set_keepalive # promote to variable
      set_fact:
        var_sshd_set_keepalive: !!str 3
      tags:
        - always

    - name: Set SSH Client Alive Count Max
      block:

      - name: Deduplicate values from /etc/ssh/sshd_config
        lineinfile:
          path: /etc/ssh/sshd_config
          create: false
          regexp: (?i)(?i)^\s*{{ "ClientAliveCountMax"| regex_escape }}\s+
          state: absent

      - name: Check if /etc/ssh/sshd_config.d exists
        stat:
          path: /etc/ssh/sshd_config.d
        register: _etc_ssh_sshd_config_d_exists

      - name: Check if the parameter ClientAliveCountMax is present in /etc/ssh/sshd_config.d
        find:
          paths: /etc/ssh/sshd_config.d
          recurse: 'yes'
          follow: 'no'
          contains: (?i)^\s*{{ "ClientAliveCountMax"| regex_escape }}\s+
        register: _etc_ssh_sshd_config_d_has_parameter
        when: _etc_ssh_sshd_config_d_exists.stat.isdir is defined and _etc_ssh_sshd_config_d_exists.stat.isdir

      - name: Remove parameter from files in /etc/ssh/sshd_config.d
        lineinfile:
          path: '{{ item.path }}'
          create: false
          regexp: (?i)(?i)^\s*{{ "ClientAliveCountMax"| regex_escape }}\s+
          state: absent
        with_items: '{{ _etc_ssh_sshd_config_d_has_parameter.files }}'
        when: _etc_ssh_sshd_config_d_has_parameter.matched

      - name: Insert correct line to /etc/ssh/sshd_config.d/00-complianceascode-hardening.conf
        lineinfile:
          path: /etc/ssh/sshd_config.d/00-complianceascode-hardening.conf
          create: true
          regexp: (?i)(?i)^\s*{{ "ClientAliveCountMax"| regex_escape }}\s+
          line: ClientAliveCountMax {{ var_sshd_set_keepalive }}
          state: present
          insertbefore: BOF
          validate: /usr/sbin/sshd -t -f %s
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - CJIS-5.5.6
      - DISA-STIG-UBTU-20-010036
      - NIST-800-171-3.1.11
      - NIST-800-53-AC-12
      - NIST-800-53-AC-17(a)
      - NIST-800-53-AC-2(5)
      - NIST-800-53-CM-6(a)
      - NIST-800-53-SC-10
      - PCI-DSS-Req-8.1.8
      - PCI-DSSv4-8.2
      - PCI-DSSv4-8.2.8
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy
      - sshd_set_keepalive

    - name: Set SSH Client Alive Count Max - set file mode for /etc/ssh/sshd_config.d/00-complianceascode-hardening.conf
      ansible.builtin.file:
        path: /etc/ssh/sshd_config.d/00-complianceascode-hardening.conf
        mode: '0600'
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - CJIS-5.5.6
      - DISA-STIG-UBTU-20-010036
      - NIST-800-171-3.1.11
      - NIST-800-53-AC-12
      - NIST-800-53-AC-17(a)
      - NIST-800-53-AC-2(5)
      - NIST-800-53-CM-6(a)
      - NIST-800-53-SC-10
      - PCI-DSS-Req-8.1.8
      - PCI-DSSv4-8.2
      - PCI-DSSv4-8.2.8
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy
      - sshd_set_keepalive

#### Rule Set SSH Client Alive Interval [ref]

SSH allows administrators to set a network responsiveness timeout interval. After this interval has passed, the unresponsive client will be automatically logged out.
To set this timeout interval, edit the following line in `/etc/ssh/sshd_config` as follows:

    ClientAliveInterval 300

The timeout interval is given in seconds. For example, have a timeout of 10 minutes, set interval to 600.
If a shorter timeout has already been set for the login shell, that value will preempt any SSH setting made in `/etc/ssh/sshd_config`. Keep in mind that some processes may stop SSH from correctly detecting that the user is idle.
Warning: SSH disconnecting unresponsive clients will not have desired effect without also configuring ClientAliveCountMax in the SSH service configuration.
Warning: Following conditions may prevent the SSH session to time out:

- Remote processes on the remote machine generates output. As the output has to be transferred over the network to the client, the timeout is reset every time such transfer happens.
- Any `scp` or `sftp` activity by the same user to the host resets the timeout.

Rationale: | Terminating an idle ssh session within a short time period reduces the window of opportunity for unauthorized personnel to take control of a management session enabled on the console or console port that has been let unattended.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_sshd_set_idle_timeout

References:

cis-csc | 1, 12, 13, 14, 15, 16, 18, 3, 5, 7, 8
cjis | 5.5.6
cobit5 | APO13.01, BAI03.01, BAI03.02, BAI03.03, DSS01.03, DSS03.05, DSS05.04, DSS05.05, DSS05.07, DSS05.10, DSS06.03, DSS06.10
cui | 3.1.11
disa | CCI-001133, CCI-002361, CCI-002891
isa-62443-2009 | 4.3.3.2.2, 4.3.3.5.1, 4.3.3.5.2, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.2, 4.3.3.7.3, 4.3.3.7.4, 4.3.4.3.3
isa-62443-2013 | SR 1.1, SR 1.10, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 6.2
iso27001-2013 | A.12.4.1, A.12.4.3, A.14.1.1, A.14.2.1, A.14.2.5, A.18.1.4, A.6.1.2, A.6.1.5, A.7.1.1, A.9.1.2, A.9.2.1, A.9.2.2, A.9.2.3, A.9.2.4, A.9.2.6, A.9.3.1, A.9.4.1, A.9.4.2, A.9.4.3, A.9.4.4, A.9.4.5
nerc-cip | CIP-004-6 R2.2.3, CIP-007-3 R5.1, CIP-007-3 R5.2, CIP-007-3 R5.3.1, CIP-007-3 R5.3.2, CIP-007-3 R5.3.3
nist | CM-6(a), AC-17(a), AC-2(5), AC-12, AC-17(a), SC-10, CM-6(a)
nist-csf | DE.CM-1, DE.CM-3, PR.AC-1, PR.AC-4, PR.AC-6, PR.AC-7, PR.IP-2
pcidss | Req-8.1.8
os-srg | SRG-OS-000126-GPOS-00066, SRG-OS-000163-GPOS-00072, SRG-OS-000279-GPOS-00109, SRG-OS-000395-GPOS-00175
stigid | UBTU-20-010037
cis | 5.2.15
pcidss4 | 8.2.8, 8.2
stigref | SV-238213r951468_rule

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | restrict

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    sshd_idle_timeout_value='300'

    mkdir -p /etc/ssh/sshd_config.d
    touch /etc/ssh/sshd_config.d/00-complianceascode-hardening.conf
    chmod 0600 /etc/ssh/sshd_config.d/00-complianceascode-hardening.conf

    LC_ALL=C sed -i "/^\s*ClientAliveInterval\s\+/Id" "/etc/ssh/sshd_config"
    LC_ALL=C sed -i "/^\s*ClientAliveInterval\s\+/Id" "/etc/ssh/sshd_config.d"/*.conf
    if [ -e "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf" ] ; then

        LC_ALL=C sed -i "/^\s*ClientAliveInterval\s\+/Id" "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf"
    else
        touch "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf"
    fi
    # make sure file has newline at the end
    sed -i -e '$a\' "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf"

    cp "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf" "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf.bak"
    # Insert at the beginning of the file
    printf '%s\n' "ClientAliveInterval $sshd_idle_timeout_value" > "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf"
    cat "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf.bak" >> "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf"
    # Clean up after ourselves.
    rm "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf.bak"

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | restrict

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - CJIS-5.5.6
      - DISA-STIG-UBTU-20-010037
      - NIST-800-171-3.1.11
      - NIST-800-53-AC-12
      - NIST-800-53-AC-17(a)
      - NIST-800-53-AC-17(a)
      - NIST-800-53-AC-2(5)
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-6(a)
      - NIST-800-53-SC-10
      - PCI-DSS-Req-8.1.8
      - PCI-DSSv4-8.2
      - PCI-DSSv4-8.2.8
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy
      - sshd_set_idle_timeout
    - name: XCCDF Value sshd_idle_timeout_value # promote to variable
      set_fact:
        sshd_idle_timeout_value: !!str 300
      tags:
        - always

    - name: Set SSH Client Alive Interval
      block:

      - name: Deduplicate values from /etc/ssh/sshd_config
        lineinfile:
          path: /etc/ssh/sshd_config
          create: false
          regexp: (?i)(?i)^\s*{{ "ClientAliveInterval"| regex_escape }}\s+
          state: absent

      - name: Check if /etc/ssh/sshd_config.d exists
        stat:
          path: /etc/ssh/sshd_config.d
        register: _etc_ssh_sshd_config_d_exists

      - name: Check if the parameter ClientAliveInterval is present in /etc/ssh/sshd_config.d
        find:
          paths: /etc/ssh/sshd_config.d
          recurse: 'yes'
          follow: 'no'
          contains: (?i)^\s*{{ "ClientAliveInterval"| regex_escape }}\s+
        register: _etc_ssh_sshd_config_d_has_parameter
        when: _etc_ssh_sshd_config_d_exists.stat.isdir is defined and _etc_ssh_sshd_config_d_exists.stat.isdir

      - name: Remove parameter from files in /etc/ssh/sshd_config.d
        lineinfile:
          path: '{{ item.path }}'
          create: false
          regexp: (?i)(?i)^\s*{{ "ClientAliveInterval"| regex_escape }}\s+
          state: absent
        with_items: '{{ _etc_ssh_sshd_config_d_has_parameter.files }}'
        when: _etc_ssh_sshd_config_d_has_parameter.matched

      - name: Insert correct line to /etc/ssh/sshd_config.d/00-complianceascode-hardening.conf
        lineinfile:
          path: /etc/ssh/sshd_config.d/00-complianceascode-hardening.conf
          create: true
          regexp: (?i)(?i)^\s*{{ "ClientAliveInterval"| regex_escape }}\s+
          line: ClientAliveInterval {{ sshd_idle_timeout_value }}
          state: present
          insertbefore: BOF
          validate: /usr/sbin/sshd -t -f %s
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - CJIS-5.5.6
      - DISA-STIG-UBTU-20-010037
      - NIST-800-171-3.1.11
      - NIST-800-53-AC-12
      - NIST-800-53-AC-17(a)
      - NIST-800-53-AC-17(a)
      - NIST-800-53-AC-2(5)
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-6(a)
      - NIST-800-53-SC-10
      - PCI-DSS-Req-8.1.8
      - PCI-DSSv4-8.2
      - PCI-DSSv4-8.2.8
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy
      - sshd_set_idle_timeout

    - name: Set SSH Client Alive Interval - set file mode for /etc/ssh/sshd_config.d/00-complianceascode-hardening.conf
      ansible.builtin.file:
        path: /etc/ssh/sshd_config.d/00-complianceascode-hardening.conf
        mode: '0600'
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - CJIS-5.5.6
      - DISA-STIG-UBTU-20-010037
      - NIST-800-171-3.1.11
      - NIST-800-53-AC-12
      - NIST-800-53-AC-17(a)
      - NIST-800-53-AC-17(a)
      - NIST-800-53-AC-2(5)
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-6(a)
      - NIST-800-53-SC-10
      - PCI-DSS-Req-8.1.8
      - PCI-DSSv4-8.2
      - PCI-DSSv4-8.2.8
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy
      - sshd_set_idle_timeout

#### Rule Disable Host-Based Authentication [ref]

SSH's cryptographic host-based authentication is more secure than `.rhosts` authentication. However, it is not recommended that hosts unilaterally trust one another, even within an organization.
The default SSH configuration disables host-based authentication. The appropriate configuration is used if no value is set for `HostbasedAuthentication`.
To explicitly disable host-based authentication, add or correct the following line in `/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf`:

    HostbasedAuthentication no

Rationale: | SSH trust relationships mean a compromise on one host can allow an attacker to move trivially to other hosts.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_disable_host_auth

References:

cis-csc | 11, 12, 14, 15, 16, 18, 3, 5, 9
cjis | 5.5.6
cobit5 | BAI10.01, BAI10.02, BAI10.03, BAI10.05, DSS05.02, DSS05.04, DSS05.05, DSS05.07, DSS06.03, DSS06.06
cui | 3.1.12
disa | CCI-000366
hipaa | 164.308(a)(4)(i), 164.308(b)(1), 164.308(b)(3), 164.310(b), 164.312(e)(1), 164.312(e)(2)(ii)
isa-62443-2009 | 4.3.3.2.2, 4.3.3.5.1, 4.3.3.5.2, 4.3.3.5.3, 4.3.3.5.4, 4.3.3.5.5, 4.3.3.5.6, 4.3.3.5.7, 4.3.3.5.8, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.1, 4.3.3.7.2, 4.3.3.7.3, 4.3.3.7.4, 4.3.4.3.2, 4.3.4.3.3
isa-62443-2013 | SR 1.1, SR 1.10, SR 1.11, SR 1.12, SR 1.13, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.6, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 2.2, SR 2.3, SR 2.4, SR 2.5, SR 2.6, SR 2.7, SR 7.6
ism | 0421, 0422, 0431, 0974, 1173, 1401, 1504, 1505, 1546, 1557, 1558, 1559, 1560, 1561
iso27001-2013 | A.12.1.2, A.12.5.1, A.12.6.2, A.14.2.2, A.14.2.3, A.14.2.4, A.6.1.2, A.7.1.1, A.9.1.2, A.9.2.1, A.9.2.3, A.9.4.1, A.9.4.4, A.9.4.5
nerc-cip | CIP-003-8 R5.1.1, CIP-003-8 R5.3, CIP-004-6 R2.2.3, CIP-004-6 R2.3, CIP-007-3 R5.1, CIP-007-3 R5.1.2, CIP-007-3 R5.2, CIP-007-3 R5.3.1, CIP-007-3 R5.3.2, CIP-007-3 R5.3.3
nist | AC-3, AC-17(a), CM-7(a), CM-7(b), CM-6(a)
nist-csf | PR.AC-4, PR.AC-6, PR.IP-1, PR.PT-3
ospp | FIA_UAU.1
os-srg | SRG-OS-000480-GPOS-00229
cis | 5.2.8
pcidss4 | 8.3.1, 8.3

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | restrict

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    mkdir -p /etc/ssh/sshd_config.d
    touch /etc/ssh/sshd_config.d/01-complianceascode-reinforce-os-defaults.conf
    chmod 0600 /etc/ssh/sshd_config.d/01-complianceascode-reinforce-os-defaults.conf

    LC_ALL=C sed -i "/^\s*HostbasedAuthentication\s\+/Id" "/etc/ssh/sshd_config"
    LC_ALL=C sed -i "/^\s*HostbasedAuthentication\s\+/Id" "/etc/ssh/sshd_config.d"/*.conf
    if [ -e "/etc/ssh/sshd_config.d/01-complianceascode-reinforce-os-defaults.conf" ] ; then

        LC_ALL=C sed -i "/^\s*HostbasedAuthentication\s\+/Id" "/etc/ssh/sshd_config.d/01-complianceascode-reinforce-os-defaults.conf"
    else
        touch "/etc/ssh/sshd_config.d/01-complianceascode-reinforce-os-defaults.conf"
    fi
    # make sure file has newline at the end
    sed -i -e '$a\' "/etc/ssh/sshd_config.d/01-complianceascode-reinforce-os-defaults.conf"

    cp "/etc/ssh/sshd_config.d/01-complianceascode-reinforce-os-defaults.conf" "/etc/ssh/sshd_config.d/01-complianceascode-reinforce-os-defaults.conf.bak"
    # Insert at the beginning of the file
    printf '%s\n' "HostbasedAuthentication no" > "/etc/ssh/sshd_config.d/01-complianceascode-reinforce-os-defaults.conf"
    cat "/etc/ssh/sshd_config.d/01-complianceascode-reinforce-os-defaults.conf.bak" >> "/etc/ssh/sshd_config.d/01-complianceascode-reinforce-os-defaults.conf"
    # Clean up after ourselves.
    rm "/etc/ssh/sshd_config.d/01-complianceascode-reinforce-os-defaults.conf.bak"

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | restrict

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - CJIS-5.5.6
      - NIST-800-171-3.1.12
      - NIST-800-53-AC-17(a)
      - NIST-800-53-AC-3
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - PCI-DSSv4-8.3
      - PCI-DSSv4-8.3.1
      - disable_host_auth
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy

    - name: Disable Host-Based Authentication
      block:

      - name: Deduplicate values from /etc/ssh/sshd_config
        lineinfile:
          path: /etc/ssh/sshd_config
          create: false
          regexp: (?i)(?i)^\s*{{ "HostbasedAuthentication"| regex_escape }}\s+
          state: absent

      - name: Check if /etc/ssh/sshd_config.d exists
        stat:
          path: /etc/ssh/sshd_config.d
        register: _etc_ssh_sshd_config_d_exists

      - name: Check if the parameter HostbasedAuthentication is present in /etc/ssh/sshd_config.d
        find:
          paths: /etc/ssh/sshd_config.d
          recurse: 'yes'
          follow: 'no'
          contains: (?i)^\s*{{ "HostbasedAuthentication"| regex_escape }}\s+
        register: _etc_ssh_sshd_config_d_has_parameter
        when: _etc_ssh_sshd_config_d_exists.stat.isdir is defined and _etc_ssh_sshd_config_d_exists.stat.isdir

      - name: Remove parameter from files in /etc/ssh/sshd_config.d
        lineinfile:
          path: '{{ item.path }}'
          create: false
          regexp: (?i)(?i)^\s*{{ "HostbasedAuthentication"| regex_escape }}\s+
          state: absent
        with_items: '{{ _etc_ssh_sshd_config_d_has_parameter.files }}'
        when: _etc_ssh_sshd_config_d_has_parameter.matched

      - name: Insert correct line to /etc/ssh/sshd_config.d/01-complianceascode-reinforce-os-defaults.conf
        lineinfile:
          path: /etc/ssh/sshd_config.d/01-complianceascode-reinforce-os-defaults.conf
          create: true
          regexp: (?i)(?i)^\s*{{ "HostbasedAuthentication"| regex_escape }}\s+
          line: HostbasedAuthentication no
          state: present
          insertbefore: BOF
          validate: /usr/sbin/sshd -t -f %s
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - CJIS-5.5.6
      - NIST-800-171-3.1.12
      - NIST-800-53-AC-17(a)
      - NIST-800-53-AC-3
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - PCI-DSSv4-8.3
      - PCI-DSSv4-8.3.1
      - disable_host_auth
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy

    - name: Disable Host-Based Authentication - set file mode for /etc/ssh/sshd_config.d/01-complianceascode-reinforce-os-defaults.conf
      ansible.builtin.file:
        path: /etc/ssh/sshd_config.d/01-complianceascode-reinforce-os-defaults.conf
        mode: '0600'
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - CJIS-5.5.6
      - NIST-800-171-3.1.12
      - NIST-800-53-AC-17(a)
      - NIST-800-53-AC-3
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - PCI-DSSv4-8.3
      - PCI-DSSv4-8.3.1
      - disable_host_auth
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy

#### Rule Disable SSH Access via Empty Passwords [ref]

Disallow SSH login with empty passwords. The default SSH configuration disables logins with empty passwords. The appropriate configuration is used if no value is set for `PermitEmptyPasswords`.
To explicitly disallow SSH login from accounts with empty passwords, add or correct the following line in `/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf`:

    PermitEmptyPasswords no

Any accounts with empty passwords should be disabled immediately, and PAM configuration should prevent users from being able to assign themselves empty passwords.

Rationale: | Configuring this setting for the SSH daemon provides additional assurance that remote login via SSH will require a password, even in the event of misconfiguration elsewhere.
Severity: | high
Rule ID: | xccdf_org.ssgproject.content_rule_sshd_disable_empty_passwords

References:

cis-csc | 11, 12, 13, 14, 15, 16, 18, 3, 5, 9
cjis | 5.5.6
cobit5 | APO01.06, BAI10.01, BAI10.02, BAI10.03, BAI10.05, DSS05.02, DSS05.04, DSS05.05, DSS05.07, DSS06.02, DSS06.03, DSS06.06
cui | 3.1.1, 3.1.5
disa | CCI-000766, CCI-000366
hipaa | 164.308(a)(4)(i), 164.308(b)(1), 164.308(b)(3), 164.310(b), 164.312(e)(1), 164.312(e)(2)(ii)
isa-62443-2009 | 4.3.3.2.2, 4.3.3.5.1, 4.3.3.5.2, 4.3.3.5.3, 4.3.3.5.4, 4.3.3.5.5, 4.3.3.5.6, 4.3.3.5.7, 4.3.3.5.8, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.1, 4.3.3.7.2, 4.3.3.7.3, 4.3.3.7.4, 4.3.4.3.2, 4.3.4.3.3
isa-62443-2013 | SR 1.1, SR 1.10, SR 1.11, SR 1.12, SR 1.13, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.6, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 2.2, SR 2.3, SR 2.4, SR 2.5, SR 2.6, SR 2.7, SR 5.2, SR 7.6
iso27001-2013 | A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.12.1.2, A.12.5.1, A.12.6.2, A.13.1.1, A.13.1.3, A.13.2.1, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, A.14.2.2, A.14.2.3, A.14.2.4, A.6.1.2, A.7.1.1, A.7.1.2, A.7.3.1, A.8.2.2, A.8.2.3, A.9.1.1, A.9.1.2, A.9.2.1, A.9.2.3, A.9.4.1, A.9.4.4, A.9.4.5
nist | AC-17(a), CM-7(a), CM-7(b), CM-6(a)
nist-csf | PR.AC-4, PR.AC-6, PR.DS-5, PR.IP-1, PR.PT-3
ospp | FIA_UAU.1
pcidss | Req-2.2.4
os-srg | SRG-OS-000106-GPOS-00053, SRG-OS-000480-GPOS-00229, SRG-OS-000480-GPOS-00227
stigid | UBTU-20-010047
cis | 5.2.10
pcidss4 | 2.2.6, 2.2
stigref | SV-238218r951479_rule

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | restrict

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    mkdir -p /etc/ssh/sshd_config.d
    touch /etc/ssh/sshd_config.d/01-complianceascode-reinforce-os-defaults.conf
    chmod 0600 /etc/ssh/sshd_config.d/01-complianceascode-reinforce-os-defaults.conf

    LC_ALL=C sed -i "/^\s*PermitEmptyPasswords\s\+/Id" "/etc/ssh/sshd_config"
    LC_ALL=C sed -i "/^\s*PermitEmptyPasswords\s\+/Id" "/etc/ssh/sshd_config.d"/*.conf
    if [ -e "/etc/ssh/sshd_config.d/01-complianceascode-reinforce-os-defaults.conf" ] ; then

        LC_ALL=C sed -i "/^\s*PermitEmptyPasswords\s\+/Id" "/etc/ssh/sshd_config.d/01-complianceascode-reinforce-os-defaults.conf"
    else
        touch "/etc/ssh/sshd_config.d/01-complianceascode-reinforce-os-defaults.conf"
    fi
    # make sure file has newline at the end
    sed -i -e '$a\' "/etc/ssh/sshd_config.d/01-complianceascode-reinforce-os-defaults.conf"

    cp "/etc/ssh/sshd_config.d/01-complianceascode-reinforce-os-defaults.conf" "/etc/ssh/sshd_config.d/01-complianceascode-reinforce-os-defaults.conf.bak"
    # Insert at the beginning of the file
    printf '%s\n' "PermitEmptyPasswords no" > "/etc/ssh/sshd_config.d/01-complianceascode-reinforce-os-defaults.conf"
    cat "/etc/ssh/sshd_config.d/01-complianceascode-reinforce-os-defaults.conf.bak" >> "/etc/ssh/sshd_config.d/01-complianceascode-reinforce-os-defaults.conf"
    # Clean up after ourselves.
    rm "/etc/ssh/sshd_config.d/01-complianceascode-reinforce-os-defaults.conf.bak"

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | restrict

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - CJIS-5.5.6
      - DISA-STIG-UBTU-20-010047
      - NIST-800-171-3.1.1
      - NIST-800-171-3.1.5
      - NIST-800-53-AC-17(a)
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - PCI-DSS-Req-2.2.4
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - high_severity
      - low_complexity
      - low_disruption
      - no_reboot_needed
      - restrict_strategy
      - sshd_disable_empty_passwords

    - name: Disable SSH Access via Empty Passwords
      block:

      - name: Deduplicate values from /etc/ssh/sshd_config
        lineinfile:
          path: /etc/ssh/sshd_config
          create: false
          regexp: (?i)(?i)^\s*{{ "PermitEmptyPasswords"| regex_escape }}\s+
          state: absent

      - name: Check if /etc/ssh/sshd_config.d exists
        stat:
          path: /etc/ssh/sshd_config.d
        register: _etc_ssh_sshd_config_d_exists

      - name: Check if the parameter PermitEmptyPasswords is present in /etc/ssh/sshd_config.d
        find:
          paths: /etc/ssh/sshd_config.d
          recurse: 'yes'
          follow: 'no'
          contains: (?i)^\s*{{ "PermitEmptyPasswords"| regex_escape }}\s+
        register: _etc_ssh_sshd_config_d_has_parameter
        when: _etc_ssh_sshd_config_d_exists.stat.isdir is defined and _etc_ssh_sshd_config_d_exists.stat.isdir

      - name: Remove parameter from files in /etc/ssh/sshd_config.d
        lineinfile:
          path: '{{ item.path }}'
          create: false
          regexp: (?i)(?i)^\s*{{ "PermitEmptyPasswords"| regex_escape }}\s+
          state: absent
        with_items: '{{ _etc_ssh_sshd_config_d_has_parameter.files }}'
        when: _etc_ssh_sshd_config_d_has_parameter.matched

      - name: Insert correct line to /etc/ssh/sshd_config.d/01-complianceascode-reinforce-os-defaults.conf
        lineinfile:
          path: /etc/ssh/sshd_config.d/01-complianceascode-reinforce-os-defaults.conf
          create: true
          regexp: (?i)(?i)^\s*{{ "PermitEmptyPasswords"| regex_escape }}\s+
          line: PermitEmptyPasswords no
          state: present
          insertbefore: BOF
          validate: /usr/sbin/sshd -t -f %s
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - CJIS-5.5.6
      - DISA-STIG-UBTU-20-010047
      - NIST-800-171-3.1.1
      - NIST-800-171-3.1.5
      - NIST-800-53-AC-17(a)
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - PCI-DSS-Req-2.2.4
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - high_severity
      - low_complexity
      - low_disruption
      - no_reboot_needed
      - restrict_strategy
      - sshd_disable_empty_passwords

    - name: Disable SSH Access via Empty Passwords - set file mode for /etc/ssh/sshd_config.d/01-complianceascode-reinforce-os-defaults.conf
      ansible.builtin.file:
        path: /etc/ssh/sshd_config.d/01-complianceascode-reinforce-os-defaults.conf
        mode: '0600'
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - CJIS-5.5.6
      - DISA-STIG-UBTU-20-010047
      - NIST-800-171-3.1.1
      - NIST-800-171-3.1.5
      - NIST-800-53-AC-17(a)
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - PCI-DSS-Req-2.2.4
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - high_severity
      - low_complexity
      - low_disruption
      - no_reboot_needed
      - restrict_strategy
      - sshd_disable_empty_passwords

#### Rule Disable SSH Support for .rhosts Files [ref]

SSH can emulate the behavior of the obsolete rsh command in allowing users to enable insecure access to their accounts via `.rhosts` files.
The default SSH configuration disables support for `.rhosts`. The appropriate configuration is used if no value is set for `IgnoreRhosts`.
To explicitly disable support for .rhosts files, add or correct the following line in `/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf`:

    IgnoreRhosts yes

Rationale: | SSH trust relationships mean a compromise on one host can allow an attacker to move trivially to other hosts.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_sshd_disable_rhosts

References:

cis-csc | 11, 12, 14, 15, 16, 18, 3, 5, 9
cjis | 5.5.6
cobit5 | BAI10.01, BAI10.02, BAI10.03, BAI10.05, DSS05.02, DSS05.04, DSS05.05, DSS05.07, DSS06.03, DSS06.06
cui | 3.1.12
disa | CCI-000366
isa-62443-2009 | 4.3.3.2.2, 4.3.3.5.1, 4.3.3.5.2, 4.3.3.5.3, 4.3.3.5.4, 4.3.3.5.5, 4.3.3.5.6, 4.3.3.5.7, 4.3.3.5.8, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.1, 4.3.3.7.2, 4.3.3.7.3, 4.3.3.7.4, 4.3.4.3.2, 4.3.4.3.3
isa-62443-2013 | SR 1.1, SR 1.10, SR 1.11, SR 1.12, SR 1.13, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.6, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 2.2, SR 2.3, SR 2.4, SR 2.5, SR 2.6, SR 2.7, SR 7.6
iso27001-2013 | A.12.1.2, A.12.5.1, A.12.6.2, A.14.2.2, A.14.2.3, A.14.2.4, A.6.1.2, A.7.1.1, A.9.1.2, A.9.2.1, A.9.2.3, A.9.4.1, A.9.4.4, A.9.4.5
nist | AC-17(a), CM-7(a), CM-7(b), CM-6(a)
nist-csf | PR.AC-4, PR.AC-6, PR.IP-1, PR.PT-3
os-srg | SRG-OS-000480-GPOS-00227
cis | 5.2.7
pcidss4 | 2.2.6, 2.2

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | restrict

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    mkdir -p /etc/ssh/sshd_config.d
    touch /etc/ssh/sshd_config.d/01-complianceascode-reinforce-os-defaults.conf
    chmod 0600 /etc/ssh/sshd_config.d/01-complianceascode-reinforce-os-defaults.conf

    LC_ALL=C sed -i "/^\s*IgnoreRhosts\s\+/Id" "/etc/ssh/sshd_config"
    LC_ALL=C sed -i "/^\s*IgnoreRhosts\s\+/Id" "/etc/ssh/sshd_config.d"/*.conf
    if [ -e "/etc/ssh/sshd_config.d/01-complianceascode-reinforce-os-defaults.conf" ] ; then

        LC_ALL=C sed -i "/^\s*IgnoreRhosts\s\+/Id" "/etc/ssh/sshd_config.d/01-complianceascode-reinforce-os-defaults.conf"
    else
        touch "/etc/ssh/sshd_config.d/01-complianceascode-reinforce-os-defaults.conf"
    fi
    # make sure file has newline at the end
    sed -i -e '$a\' "/etc/ssh/sshd_config.d/01-complianceascode-reinforce-os-defaults.conf"

    cp "/etc/ssh/sshd_config.d/01-complianceascode-reinforce-os-defaults.conf" "/etc/ssh/sshd_config.d/01-complianceascode-reinforce-os-defaults.conf.bak"
    # Insert at the beginning of the file
    printf '%s\n' "IgnoreRhosts yes" > "/etc/ssh/sshd_config.d/01-complianceascode-reinforce-os-defaults.conf"
    cat "/etc/ssh/sshd_config.d/01-complianceascode-reinforce-os-defaults.conf.bak" >> "/etc/ssh/sshd_config.d/01-complianceascode-reinforce-os-defaults.conf"
    # Clean up after ourselves.
    rm "/etc/ssh/sshd_config.d/01-complianceascode-reinforce-os-defaults.conf.bak"

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | restrict

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - CJIS-5.5.6
      - NIST-800-171-3.1.12
      - NIST-800-53-AC-17(a)
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy
      - sshd_disable_rhosts

    - name: Disable SSH Support for .rhosts Files
      block:

      - name: Deduplicate values from /etc/ssh/sshd_config
        lineinfile:
          path: /etc/ssh/sshd_config
          create: false
          regexp: (?i)(?i)^\s*{{ "IgnoreRhosts"| regex_escape }}\s+
          state: absent

      - name: Check if /etc/ssh/sshd_config.d exists
        stat:
          path: /etc/ssh/sshd_config.d
        register: _etc_ssh_sshd_config_d_exists

      - name: Check if the parameter IgnoreRhosts is present in /etc/ssh/sshd_config.d
        find:
          paths: /etc/ssh/sshd_config.d
          recurse: 'yes'
          follow: 'no'
          contains: (?i)^\s*{{ "IgnoreRhosts"| regex_escape }}\s+
        register: _etc_ssh_sshd_config_d_has_parameter
        when: _etc_ssh_sshd_config_d_exists.stat.isdir is defined and _etc_ssh_sshd_config_d_exists.stat.isdir

      - name: Remove parameter from files in /etc/ssh/sshd_config.d
        lineinfile:
          path: '{{ item.path }}'
          create: false
          regexp: (?i)(?i)^\s*{{ "IgnoreRhosts"| regex_escape }}\s+
          state: absent
        with_items: '{{ _etc_ssh_sshd_config_d_has_parameter.files }}'
        when: _etc_ssh_sshd_config_d_has_parameter.matched

      - name: Insert correct line to /etc/ssh/sshd_config.d/01-complianceascode-reinforce-os-defaults.conf
        lineinfile:
          path: /etc/ssh/sshd_config.d/01-complianceascode-reinforce-os-defaults.conf
          create: true
          regexp: (?i)(?i)^\s*{{ "IgnoreRhosts"| regex_escape }}\s+
          line: IgnoreRhosts yes
          state: present
          insertbefore: BOF
          validate: /usr/sbin/sshd -t -f %s
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - CJIS-5.5.6
      - NIST-800-171-3.1.12
      - NIST-800-53-AC-17(a)
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy
      - sshd_disable_rhosts

    - name: Disable SSH Support for .rhosts Files - set file mode for /etc/ssh/sshd_config.d/01-complianceascode-reinforce-os-defaults.conf
      ansible.builtin.file:
        path: /etc/ssh/sshd_config.d/01-complianceascode-reinforce-os-defaults.conf
        mode: '0600'
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - CJIS-5.5.6
      - NIST-800-171-3.1.12
      - NIST-800-53-AC-17(a)
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy
      - sshd_disable_rhosts

#### Rule Disable SSH Root Login [ref]

The root user should never be allowed to login to a system directly over a network. To disable root login via SSH, add or correct the following line in `/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf`:

    PermitRootLogin no

Rationale: | Even though the communications channel may be encrypted, an additional layer of security is gained by extending the policy of not logging directly on as root. In addition, logging in with a user-specific account provides individual accountability of actions performed on the system and also helps to minimize direct attack attempts on root's password.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_sshd_disable_root_login

References:

cis-csc | 1, 11, 12, 13, 14, 15, 16, 18, 3, 5
cjis | 5.5.6
cobit5 | APO01.06, DSS05.02, DSS05.04, DSS05.05, DSS05.07, DSS05.10, DSS06.02, DSS06.03, DSS06.06, DSS06.10
cui | 3.1.1, 3.1.5
disa | CCI-000366, CCI-004045
hipaa | 164.308(a)(4)(i), 164.308(b)(1), 164.308(b)(3), 164.310(b), 164.312(e)(1), 164.312(e)(2)(ii)
isa-62443-2009 | 4.3.3.2.2, 4.3.3.5.1, 4.3.3.5.2, 4.3.3.5.3, 4.3.3.5.4, 4.3.3.5.5, 4.3.3.5.6, 4.3.3.5.7, 4.3.3.5.8, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.1, 4.3.3.7.2, 4.3.3.7.3, 4.3.3.7.4
isa-62443-2013 | SR 1.1, SR 1.10, SR 1.11, SR 1.12, SR 1.13, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.6, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 2.2, SR 2.3, SR 2.4, SR 2.5, SR 2.6, SR 2.7, SR 5.2
iso27001-2013 | A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.13.1.1, A.13.1.3, A.13.2.1, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, A.18.1.4, A.6.1.2, A.7.1.1, A.7.1.2, A.7.3.1, A.8.2.2, A.8.2.3, A.9.1.1, A.9.1.2, A.9.2.1, A.9.2.2, A.9.2.3, A.9.2.4, A.9.2.6, A.9.3.1, A.9.4.1, A.9.4.2, A.9.4.3, A.9.4.4, A.9.4.5
nerc-cip | CIP-003-8 R5.1.1, CIP-003-8 R5.3, CIP-004-6 R2.2.3, CIP-004-6 R2.3, CIP-007-3 R2.1, CIP-007-3 R2.2, CIP-007-3 R2.3, CIP-007-3 R5.1, CIP-007-3 R5.1.1, CIP-007-3 R5.1.2, CIP-007-3 R5.2, CIP-007-3 R5.3.1, CIP-007-3 R5.3.2, CIP-007-3 R5.3.3
nist | AC-6(2), AC-17(a), IA-2, IA-2(5), CM-7(a), CM-7(b), CM-6(a)
nist-csf | PR.AC-1, PR.AC-4, PR.AC-6, PR.AC-7, PR.DS-5, PR.PT-3
ospp | FAU_GEN.1
pcidss | Req-2.2.4
os-srg | SRG-OS-000109-GPOS-00056, SRG-OS-000480-GPOS-00227
app-srg-ctr | SRG-APP-000148-CTR-000335, SRG-APP-000190-CTR-000500
cis | 5.2.9
anssi | R33
pcidss4 | 2.2.6, 2.2

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | restrict

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    mkdir -p /etc/ssh/sshd_config.d
    touch /etc/ssh/sshd_config.d/00-complianceascode-hardening.conf
    chmod 0600 /etc/ssh/sshd_config.d/00-complianceascode-hardening.conf

    LC_ALL=C sed -i "/^\s*PermitRootLogin\s\+/Id" "/etc/ssh/sshd_config"
    LC_ALL=C sed -i "/^\s*PermitRootLogin\s\+/Id" "/etc/ssh/sshd_config.d"/*.conf
    if [ -e "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf" ] ; then

        LC_ALL=C sed -i "/^\s*PermitRootLogin\s\+/Id" "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf"
    else
        touch "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf"
    fi
    # make sure file has newline at the end
    sed -i -e '$a\' "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf"

    cp "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf" "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf.bak"
    # Insert at the beginning of the file
    printf '%s\n' "PermitRootLogin no" > "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf"
    cat "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf.bak" >> "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf"
    # Clean up after ourselves.
    rm "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf.bak"

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | restrict

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - CJIS-5.5.6
      - NIST-800-171-3.1.1
      - NIST-800-171-3.1.5
      - NIST-800-53-AC-17(a)
      - NIST-800-53-AC-6(2)
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-IA-2
      - NIST-800-53-IA-2(5)
      - PCI-DSS-Req-2.2.4
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy
      - sshd_disable_root_login

    - name: Disable SSH Root Login
      block:

      - name: Deduplicate values from /etc/ssh/sshd_config
        lineinfile:
          path: /etc/ssh/sshd_config
          create: false
          regexp: (?i)(?i)^\s*{{ "PermitRootLogin"| regex_escape }}\s+
          state: absent

      - name: Check if /etc/ssh/sshd_config.d exists
        stat:
          path: /etc/ssh/sshd_config.d
        register: _etc_ssh_sshd_config_d_exists

      - name: Check if the parameter PermitRootLogin is present in /etc/ssh/sshd_config.d
        find:
          paths: /etc/ssh/sshd_config.d
          recurse: 'yes'
          follow: 'no'
          contains: (?i)^\s*{{ "PermitRootLogin"| regex_escape }}\s+
        register: _etc_ssh_sshd_config_d_has_parameter
        when: _etc_ssh_sshd_config_d_exists.stat.isdir is defined and _etc_ssh_sshd_config_d_exists.stat.isdir

      - name: Remove parameter from files in /etc/ssh/sshd_config.d
        lineinfile:
          path: '{{ item.path }}'
          create: false
          regexp: (?i)(?i)^\s*{{ "PermitRootLogin"| regex_escape }}\s+
          state: absent
        with_items: '{{ _etc_ssh_sshd_config_d_has_parameter.files }}'
        when: _etc_ssh_sshd_config_d_has_parameter.matched

      - name: Insert correct line to /etc/ssh/sshd_config.d/00-complianceascode-hardening.conf
        lineinfile:
          path: /etc/ssh/sshd_config.d/00-complianceascode-hardening.conf
          create: true
          regexp: (?i)(?i)^\s*{{ "PermitRootLogin"| regex_escape }}\s+
          line: PermitRootLogin no
          state: present
          insertbefore: BOF
          validate: /usr/sbin/sshd -t -f %s
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - CJIS-5.5.6
      - NIST-800-171-3.1.1
      - NIST-800-171-3.1.5
      - NIST-800-53-AC-17(a)
      - NIST-800-53-AC-6(2)
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-IA-2
      - NIST-800-53-IA-2(5)
      - PCI-DSS-Req-2.2.4
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy
      - sshd_disable_root_login

    - name: Disable SSH Root Login - set file mode for /etc/ssh/sshd_config.d/00-complianceascode-hardening.conf
      ansible.builtin.file:
        path: /etc/ssh/sshd_config.d/00-complianceascode-hardening.conf
        mode: '0600'
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - CJIS-5.5.6
      - NIST-800-171-3.1.1
      - NIST-800-171-3.1.5
      - NIST-800-53-AC-17(a)
      - NIST-800-53-AC-6(2)
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - NIST-800-53-IA-2
      - NIST-800-53-IA-2(5)
      - PCI-DSS-Req-2.2.4
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy
      - sshd_disable_root_login

#### Rule Do Not Allow SSH Environment Options [ref]

Ensure that users are not able to override environment variables of the SSH daemon.
The default SSH configuration disables environment processing. The appropriate configuration is used if no value is set for `PermitUserEnvironment`.
To explicitly disable Environment options, add or correct the following `/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf`:

    PermitUserEnvironment no

Rationale: | SSH environment options potentially allow users to bypass access restriction in some configurations.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_sshd_do_not_permit_user_env

References:

cis-csc | 11, 3, 9
cjis | 5.5.6
cobit5 | BAI10.01, BAI10.02, BAI10.03, BAI10.05
cui | 3.1.12
disa | CCI-000366
hipaa | 164.308(a)(4)(i), 164.308(b)(1), 164.308(b)(3), 164.310(b), 164.312(e)(1), 164.312(e)(2)(ii)
isa-62443-2009 | 4.3.4.3.2, 4.3.4.3.3
isa-62443-2013 | SR 7.6
iso27001-2013 | A.12.1.2, A.12.5.1, A.12.6.2, A.14.2.2, A.14.2.3, A.14.2.4
nist | AC-17(a), CM-7(a), CM-7(b), CM-6(a)
nist-csf | PR.IP-1
pcidss | Req-2.2.4
os-srg | SRG-OS-000480-GPOS-00229
stigid | UBTU-20-010047
cis | 5.2.11
pcidss4 | 2.2.6, 2.2
stigref | SV-238218r951479_rule

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | restrict

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    mkdir -p /etc/ssh/sshd_config.d
    touch /etc/ssh/sshd_config.d/01-complianceascode-reinforce-os-defaults.conf
    chmod 0600 /etc/ssh/sshd_config.d/01-complianceascode-reinforce-os-defaults.conf

    LC_ALL=C sed -i "/^\s*PermitUserEnvironment\s\+/Id" "/etc/ssh/sshd_config"
    LC_ALL=C sed -i "/^\s*PermitUserEnvironment\s\+/Id" "/etc/ssh/sshd_config.d"/*.conf
    if [ -e "/etc/ssh/sshd_config.d/01-complianceascode-reinforce-os-defaults.conf" ] ; then

        LC_ALL=C sed -i "/^\s*PermitUserEnvironment\s\+/Id" "/etc/ssh/sshd_config.d/01-complianceascode-reinforce-os-defaults.conf"
    else
        touch "/etc/ssh/sshd_config.d/01-complianceascode-reinforce-os-defaults.conf"
    fi
    # make sure file has newline at the end
    sed -i -e '$a\' "/etc/ssh/sshd_config.d/01-complianceascode-reinforce-os-defaults.conf"

    cp "/etc/ssh/sshd_config.d/01-complianceascode-reinforce-os-defaults.conf" "/etc/ssh/sshd_config.d/01-complianceascode-reinforce-os-defaults.conf.bak"
    # Insert at the beginning of the file
    printf '%s\n' "PermitUserEnvironment no" > "/etc/ssh/sshd_config.d/01-complianceascode-reinforce-os-defaults.conf"
    cat "/etc/ssh/sshd_config.d/01-complianceascode-reinforce-os-defaults.conf.bak" >> "/etc/ssh/sshd_config.d/01-complianceascode-reinforce-os-defaults.conf"
    # Clean up after ourselves.
    rm "/etc/ssh/sshd_config.d/01-complianceascode-reinforce-os-defaults.conf.bak"

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | restrict

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - CJIS-5.5.6
      - DISA-STIG-UBTU-20-010047
      - NIST-800-171-3.1.12
      - NIST-800-53-AC-17(a)
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - PCI-DSS-Req-2.2.4
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy
      - sshd_do_not_permit_user_env

    - name: Do Not Allow SSH Environment Options
      block:

      - name: Deduplicate values from /etc/ssh/sshd_config
        lineinfile:
          path: /etc/ssh/sshd_config
          create: false
          regexp: (?i)(?i)^\s*{{ "PermitUserEnvironment"| regex_escape }}\s+
          state: absent

      - name: Check if /etc/ssh/sshd_config.d exists
        stat:
          path: /etc/ssh/sshd_config.d
        register: _etc_ssh_sshd_config_d_exists

      - name: Check if the parameter PermitUserEnvironment is present in /etc/ssh/sshd_config.d
        find:
          paths: /etc/ssh/sshd_config.d
          recurse: 'yes'
          follow: 'no'
          contains: (?i)^\s*{{ "PermitUserEnvironment"| regex_escape }}\s+
        register: _etc_ssh_sshd_config_d_has_parameter
        when: _etc_ssh_sshd_config_d_exists.stat.isdir is defined and _etc_ssh_sshd_config_d_exists.stat.isdir

      - name: Remove parameter from files in /etc/ssh/sshd_config.d
        lineinfile:
          path: '{{ item.path }}'
          create: false
          regexp: (?i)(?i)^\s*{{ "PermitUserEnvironment"| regex_escape }}\s+
          state: absent
        with_items: '{{ _etc_ssh_sshd_config_d_has_parameter.files }}'
        when: _etc_ssh_sshd_config_d_has_parameter.matched

      - name: Insert correct line to /etc/ssh/sshd_config.d/01-complianceascode-reinforce-os-defaults.conf
        lineinfile:
          path: /etc/ssh/sshd_config.d/01-complianceascode-reinforce-os-defaults.conf
          create: true
          regexp: (?i)(?i)^\s*{{ "PermitUserEnvironment"| regex_escape }}\s+
          line: PermitUserEnvironment no
          state: present
          insertbefore: BOF
          validate: /usr/sbin/sshd -t -f %s
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - CJIS-5.5.6
      - DISA-STIG-UBTU-20-010047
      - NIST-800-171-3.1.12
      - NIST-800-53-AC-17(a)
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - PCI-DSS-Req-2.2.4
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy
      - sshd_do_not_permit_user_env

    - name: Do Not Allow SSH Environment Options - set file mode for /etc/ssh/sshd_config.d/01-complianceascode-reinforce-os-defaults.conf
      ansible.builtin.file:
        path: /etc/ssh/sshd_config.d/01-complianceascode-reinforce-os-defaults.conf
        mode: '0600'
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - CJIS-5.5.6
      - DISA-STIG-UBTU-20-010047
      - NIST-800-171-3.1.12
      - NIST-800-53-AC-17(a)
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - PCI-DSS-Req-2.2.4
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy
      - sshd_do_not_permit_user_env

#### Rule Enable PAM [ref]

UsePAM Enables the Pluggable Authentication Module interface. If set to “yes” this will enable PAM authentication using ChallengeResponseAuthentication and PasswordAuthentication in addition to PAM account and session module processing for all authentication types. To enable PAM authentication, add or correct the following line in `/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf`:

    UsePAM yes

Rationale: | When UsePAM is set to yes, PAM runs through account and session types properly. This is important if you want to restrict access to services based off of IP, time or other factors of the account. Additionally, you can make sure users inherit certain environment variables on login or disallow access to the server.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_sshd_enable_pam

References:

disa | CCI-000877
os-srg | SRG-OS-000125-GPOS-00065
stigid | UBTU-20-010035
cis | 5.2.19
pcidss4 | 2.2.6, 2.2
stigref | SV-238211r951464_rule

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | restrict

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    mkdir -p /etc/ssh/sshd_config.d
    touch /etc/ssh/sshd_config.d/00-complianceascode-hardening.conf
    chmod 0600 /etc/ssh/sshd_config.d/00-complianceascode-hardening.conf

    LC_ALL=C sed -i "/^\s*UsePAM\s\+/Id" "/etc/ssh/sshd_config"
    LC_ALL=C sed -i "/^\s*UsePAM\s\+/Id" "/etc/ssh/sshd_config.d"/*.conf
    if [ -e "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf" ] ; then

        LC_ALL=C sed -i "/^\s*UsePAM\s\+/Id" "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf"
    else
        touch "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf"
    fi
    # make sure file has newline at the end
    sed -i -e '$a\' "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf"

    cp "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf" "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf.bak"
    # Insert at the beginning of the file
    printf '%s\n' "UsePAM yes" > "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf"
    cat "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf.bak" >> "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf"
    # Clean up after ourselves.
    rm "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf.bak"

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | restrict

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - DISA-STIG-UBTU-20-010035
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy
      - sshd_enable_pam

    - name: Enable PAM
      block:

      - name: Deduplicate values from /etc/ssh/sshd_config
        lineinfile:
          path: /etc/ssh/sshd_config
          create: false
          regexp: (?i)(?i)^\s*{{ "UsePAM"| regex_escape }}\s+
          state: absent

      - name: Check if /etc/ssh/sshd_config.d exists
        stat:
          path: /etc/ssh/sshd_config.d
        register: _etc_ssh_sshd_config_d_exists

      - name: Check if the parameter UsePAM is present in /etc/ssh/sshd_config.d
        find:
          paths: /etc/ssh/sshd_config.d
          recurse: 'yes'
          follow: 'no'
          contains: (?i)^\s*{{ "UsePAM"| regex_escape }}\s+
        register: _etc_ssh_sshd_config_d_has_parameter
        when: _etc_ssh_sshd_config_d_exists.stat.isdir is defined and _etc_ssh_sshd_config_d_exists.stat.isdir

      - name: Remove parameter from files in /etc/ssh/sshd_config.d
        lineinfile:
          path: '{{ item.path }}'
          create: false
          regexp: (?i)(?i)^\s*{{ "UsePAM"| regex_escape }}\s+
          state: absent
        with_items: '{{ _etc_ssh_sshd_config_d_has_parameter.files }}'
        when: _etc_ssh_sshd_config_d_has_parameter.matched

      - name: Insert correct line to /etc/ssh/sshd_config.d/00-complianceascode-hardening.conf
        lineinfile:
          path: /etc/ssh/sshd_config.d/00-complianceascode-hardening.conf
          create: true
          regexp: (?i)(?i)^\s*{{ "UsePAM"| regex_escape }}\s+
          line: UsePAM yes
          state: present
          insertbefore: BOF
          validate: /usr/sbin/sshd -t -f %s
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - DISA-STIG-UBTU-20-010035
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy
      - sshd_enable_pam

    - name: Enable PAM - set file mode for /etc/ssh/sshd_config.d/00-complianceascode-hardening.conf
      ansible.builtin.file:
        path: /etc/ssh/sshd_config.d/00-complianceascode-hardening.conf
        mode: '0600'
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - DISA-STIG-UBTU-20-010035
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy
      - sshd_enable_pam

#### Rule Enable SSH Warning Banner [ref]

To enable the warning banner and ensure it is consistent across the system, add or correct the following line in `/etc/ssh/sshd_config`:

    Banner /etc/issue.net

Another section contains information on how to create an appropriate system-wide warning banner.

Rationale: | The warning message reinforces policy awareness during the logon process and facilitates possible legal action against attackers. Alternatively, systems whose ownership should not be obvious should ensure usage of a banner that does not provide easy attribution.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_sshd_enable_warning_banner_net

References:

cjis | 5.5.6
cobit5 | DSS05.04, DSS05.10, DSS06.10
cui | 3.1.9
disa | CCI-000048, CCI-000050, CCI-001384, CCI-001385, CCI-001386, CCI-001387, CCI-001388
hipaa | 164.308(a)(4)(i), 164.308(b)(1), 164.308(b)(3), 164.310(b), 164.312(e)(1), 164.312(e)(2)(ii)
isa-62443-2009 | 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9
isa-62443-2013 | SR 1.1, SR 1.10, SR 1.2, SR 1.5, SR 1.7, SR 1.8, SR 1.9
iso27001-2013 | A.18.1.4, A.9.2.1, A.9.2.4, A.9.3.1, A.9.4.2, A.9.4.3
nist | AC-8(a), AC-8(c), AC-17(a), CM-6(a)
nist-csf | PR.AC-7
os-srg | SRG-OS-000023-GPOS-00006, SRG-OS-000228-GPOS-00088
stigid | UBTU-20-010038
cis | 5.2.18
stigref | SV-238214r951471_rule

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | restrict

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    mkdir -p /etc/ssh/sshd_config.d
    touch /etc/ssh/sshd_config.d/00-complianceascode-hardening.conf
    chmod 0600 /etc/ssh/sshd_config.d/00-complianceascode-hardening.conf

    LC_ALL=C sed -i "/^\s*Banner\s\+/Id" "/etc/ssh/sshd_config"
    LC_ALL=C sed -i "/^\s*Banner\s\+/Id" "/etc/ssh/sshd_config.d"/*.conf
    if [ -e "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf" ] ; then

        LC_ALL=C sed -i "/^\s*Banner\s\+/Id" "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf"
    else
        touch "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf"
    fi
    # make sure file has newline at the end
    sed -i -e '$a\' "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf"

    cp "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf" "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf.bak"
    # Insert at the beginning of the file
    printf '%s\n' "Banner /etc/issue.net" > "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf"
    cat "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf.bak" >> "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf"
    # Clean up after ourselves.
    rm "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf.bak"

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | restrict

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - CJIS-5.5.6
      - DISA-STIG-UBTU-20-010038
      - NIST-800-171-3.1.9
      - NIST-800-53-AC-17(a)
      - NIST-800-53-AC-8(a)
      - NIST-800-53-AC-8(c)
      - NIST-800-53-CM-6(a)
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy
      - sshd_enable_warning_banner_net

    - name: Enable SSH Warning Banner
      block:

      - name: Deduplicate values from /etc/ssh/sshd_config
        lineinfile:
          path: /etc/ssh/sshd_config
          create: false
          regexp: (?i)(?i)^\s*{{ "Banner"| regex_escape }}\s+
          state: absent

      - name: Check if /etc/ssh/sshd_config.d exists
        stat:
          path: /etc/ssh/sshd_config.d
        register: _etc_ssh_sshd_config_d_exists

      - name: Check if the parameter Banner is present in /etc/ssh/sshd_config.d
        find:
          paths: /etc/ssh/sshd_config.d
          recurse: 'yes'
          follow: 'no'
          contains: (?i)^\s*{{ "Banner"| regex_escape }}\s+
        register: _etc_ssh_sshd_config_d_has_parameter
        when: _etc_ssh_sshd_config_d_exists.stat.isdir is defined and _etc_ssh_sshd_config_d_exists.stat.isdir

      - name: Remove parameter from files in /etc/ssh/sshd_config.d
        lineinfile:
          path: '{{ item.path }}'
          create: false
          regexp: (?i)(?i)^\s*{{ "Banner"| regex_escape }}\s+
          state: absent
        with_items: '{{ _etc_ssh_sshd_config_d_has_parameter.files }}'
        when: _etc_ssh_sshd_config_d_has_parameter.matched

      - name: Insert correct line to /etc/ssh/sshd_config.d/00-complianceascode-hardening.conf
        lineinfile:
          path: /etc/ssh/sshd_config.d/00-complianceascode-hardening.conf
          create: true
          regexp: (?i)(?i)^\s*{{ "Banner"| regex_escape }}\s+
          line: Banner /etc/issue.net
          state: present
          insertbefore: BOF
          validate: /usr/sbin/sshd -t -f %s
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - CJIS-5.5.6
      - DISA-STIG-UBTU-20-010038
      - NIST-800-171-3.1.9
      - NIST-800-53-AC-17(a)
      - NIST-800-53-AC-8(a)
      - NIST-800-53-AC-8(c)
      - NIST-800-53-CM-6(a)
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy
      - sshd_enable_warning_banner_net

    - name: Enable SSH Warning Banner - set file mode for /etc/ssh/sshd_config.d/00-complianceascode-hardening.conf
      ansible.builtin.file:
        path: /etc/ssh/sshd_config.d/00-complianceascode-hardening.conf
        mode: '0600'
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - CJIS-5.5.6
      - DISA-STIG-UBTU-20-010038
      - NIST-800-171-3.1.9
      - NIST-800-53-AC-17(a)
      - NIST-800-53-AC-8(a)
      - NIST-800-53-AC-8(c)
      - NIST-800-53-CM-6(a)
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy
      - sshd_enable_warning_banner_net

#### Rule Limit Users' SSH Access [ref]

By default, the SSH configuration allows any user with an account to access the system. There are several options available to limit which users and group can access the system via SSH. It is recommended that at least one of the following options be leveraged: - AllowUsers variable gives the system administrator the option of allowing specific users to ssh into the system. The list consists of space separated user names. Numeric user IDs are not recognized with this variable. If a system administrator wants to restrict user access further by specifically allowing a user's access only from a particular host, the entry can be specified in the form of user@host. - AllowGroups variable gives the system administrator the option of allowing specific groups of users to ssh into the system. The list consists of space separated group names. Numeric group IDs are not recognized with this variable. - DenyUsers variable gives the system administrator the option of denying specific users to ssh into the system. The list consists of space separated user names. Numeric user IDs are not recognized with this variable. If a system administrator wants to restrict user access further by specifically denying a user's access from a particular host, the entry can be specified in the form of user@host. - DenyGroups variable gives the system administrator the option of denying specific groups of users to ssh into the system. The list consists of space separated group names. Numeric group IDs are not recognized with this variable.
Warning: Automated remediation is not available for this configuration check because each system has unique user names and group names.

Rationale: | Specifying which accounts are allowed SSH access into the system reduces the possibility of unauthorized access to the system.
Severity: | unknown
Rule ID: | xccdf_org.ssgproject.content_rule_sshd_limit_user_access

References:

cis-csc | 11, 12, 14, 15, 16, 18, 3, 5
cobit5 | DSS05.02, DSS05.04, DSS05.05, DSS05.07, DSS06.03, DSS06.06
cui | 3.1.12
isa-62443-2009 | 4.3.3.2.2, 4.3.3.5.1, 4.3.3.5.2, 4.3.3.5.3, 4.3.3.5.4, 4.3.3.5.5, 4.3.3.5.6, 4.3.3.5.7, 4.3.3.5.8, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.1, 4.3.3.7.2, 4.3.3.7.3, 4.3.3.7.4
isa-62443-2013 | SR 1.1, SR 1.10, SR 1.11, SR 1.12, SR 1.13, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.6, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 2.2, SR 2.3, SR 2.4, SR 2.5, SR 2.6, SR 2.7
iso27001-2013 | A.6.1.2, A.7.1.1, A.9.1.2, A.9.2.1, A.9.2.3, A.9.4.1, A.9.4.4, A.9.4.5
nerc-cip | CIP-003-8 R5.1.1, CIP-003-8 R5.3, CIP-004-6 R2.2.3, CIP-004-6 R2.3, CIP-007-3 R5.1, CIP-007-3 R5.1.2, CIP-007-3 R5.2, CIP-007-3 R5.3.1, CIP-007-3 R5.3.2, CIP-007-3 R5.3.3
nist | AC-3, CM-6(a)
nist-csf | PR.AC-4, PR.AC-6, PR.PT-3
pcidss | Req-2.2.4
cis | 5.2.17
pcidss4 | 2.2.6, 2.2

#### Rule Ensure SSH LoginGraceTime is configured [ref]

The `LoginGraceTime` parameter to the SSH server specifies the time allowed for successful authentication to the SSH server. The longer the Grace period is the more open unauthenticated connections can exist. Like other session controls in this session the Grace Period should be limited to appropriate limits to ensure the service is available for needed access.
Rationale: | Setting the `LoginGraceTime` parameter to a low number will minimize the risk of successful brute force attacks to the SSH server. It will also limit the number of concurrent unauthenticated connections.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_sshd_set_login_grace_time

References:

cis | 5.2.16
pcidss4 | 2.2.6, 2.2

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | restrict

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    var_sshd_set_login_grace_time='60'

    mkdir -p /etc/ssh/sshd_config.d
    touch /etc/ssh/sshd_config.d/00-complianceascode-hardening.conf
    chmod 0600 /etc/ssh/sshd_config.d/00-complianceascode-hardening.conf

    LC_ALL=C sed -i "/^\s*LoginGraceTime\s\+/Id" "/etc/ssh/sshd_config"
    LC_ALL=C sed -i "/^\s*LoginGraceTime\s\+/Id" "/etc/ssh/sshd_config.d"/*.conf
    if [ -e "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf" ] ; then

        LC_ALL=C sed -i "/^\s*LoginGraceTime\s\+/Id" "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf"
    else
        touch "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf"
    fi
    # make sure file has newline at the end
    sed -i -e '$a\' "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf"

    cp "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf" "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf.bak"
    # Insert at the beginning of the file
    printf '%s\n' "LoginGraceTime $var_sshd_set_login_grace_time" > "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf"
    cat "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf.bak" >> "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf"
    # Clean up after ourselves.
    rm "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf.bak"

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | restrict

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy
      - sshd_set_login_grace_time
    - name: XCCDF Value var_sshd_set_login_grace_time # promote to variable
      set_fact:
        var_sshd_set_login_grace_time: !!str 60
      tags:
        - always

    - name: Ensure SSH LoginGraceTime is configured
      block:

      - name: Deduplicate values from /etc/ssh/sshd_config
        lineinfile:
          path: /etc/ssh/sshd_config
          create: false
          regexp: (?i)(?i)^\s*{{ "LoginGraceTime"| regex_escape }}\s+
          state: absent

      - name: Check if /etc/ssh/sshd_config.d exists
        stat:
          path: /etc/ssh/sshd_config.d
        register: _etc_ssh_sshd_config_d_exists

      - name: Check if the parameter LoginGraceTime is present in /etc/ssh/sshd_config.d
        find:
          paths: /etc/ssh/sshd_config.d
          recurse: 'yes'
          follow: 'no'
          contains: (?i)^\s*{{ "LoginGraceTime"| regex_escape }}\s+
        register: _etc_ssh_sshd_config_d_has_parameter
        when: _etc_ssh_sshd_config_d_exists.stat.isdir is defined and _etc_ssh_sshd_config_d_exists.stat.isdir

      - name: Remove parameter from files in /etc/ssh/sshd_config.d
        lineinfile:
          path: '{{ item.path }}'
          create: false
          regexp: (?i)(?i)^\s*{{ "LoginGraceTime"| regex_escape }}\s+
          state: absent
        with_items: '{{ _etc_ssh_sshd_config_d_has_parameter.files }}'
        when: _etc_ssh_sshd_config_d_has_parameter.matched

      - name: Insert correct line to /etc/ssh/sshd_config.d/00-complianceascode-hardening.conf
        lineinfile:
          path: /etc/ssh/sshd_config.d/00-complianceascode-hardening.conf
          create: true
          regexp: (?i)(?i)^\s*{{ "LoginGraceTime"| regex_escape }}\s+
          line: LoginGraceTime {{ var_sshd_set_login_grace_time }}
          state: present
          insertbefore: BOF
          validate: /usr/sbin/sshd -t -f %s
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy
      - sshd_set_login_grace_time

    - name: Ensure SSH LoginGraceTime is configured - set file mode for /etc/ssh/sshd_config.d/00-complianceascode-hardening.conf
      ansible.builtin.file:
        path: /etc/ssh/sshd_config.d/00-complianceascode-hardening.conf
        mode: '0600'
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy
      - sshd_set_login_grace_time

#### Rule Set LogLevel to INFO [ref]

The INFO parameter specifices that record login and logout activity will be logged.
The default SSH configuration sets the log level to INFO. The appropriate configuration is used if no value is set for `LogLevel`.
To explicitly specify the log level in SSH, add or correct the following line in `/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf`:

    LogLevel INFO

Rationale:

SSH provides several logging levels with varying amounts of verbosity. `DEBUG` is specifically not recommended other than strictly for debugging SSH communications since it provides so much data that it is difficult to identify important security information. `INFO` level is the basic level that only records login activity of SSH users. In many situations, such as Incident Response, it is important to determine when a particular user was active on a system. The logout record can eliminate those users who disconnected, which helps narrow the field.

Severity: | low
Rule ID: | xccdf_org.ssgproject.content_rule_sshd_set_loglevel_info

References:

nist | AC-17(a), CM-6(a)
cis | 5.2.4

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | restrict

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    mkdir -p /etc/ssh/sshd_config.d
    touch /etc/ssh/sshd_config.d/01-complianceascode-reinforce-os-defaults.conf
    chmod 0600 /etc/ssh/sshd_config.d/01-complianceascode-reinforce-os-defaults.conf

    LC_ALL=C sed -i "/^\s*LogLevel\s\+/Id" "/etc/ssh/sshd_config"
    LC_ALL=C sed -i "/^\s*LogLevel\s\+/Id" "/etc/ssh/sshd_config.d"/*.conf
    if [ -e "/etc/ssh/sshd_config.d/01-complianceascode-reinforce-os-defaults.conf" ] ; then

        LC_ALL=C sed -i "/^\s*LogLevel\s\+/Id" "/etc/ssh/sshd_config.d/01-complianceascode-reinforce-os-defaults.conf"
    else
        touch "/etc/ssh/sshd_config.d/01-complianceascode-reinforce-os-defaults.conf"
    fi
    # make sure file has newline at the end
    sed -i -e '$a\' "/etc/ssh/sshd_config.d/01-complianceascode-reinforce-os-defaults.conf"

    cp "/etc/ssh/sshd_config.d/01-complianceascode-reinforce-os-defaults.conf" "/etc/ssh/sshd_config.d/01-complianceascode-reinforce-os-defaults.conf.bak"
    # Insert at the beginning of the file
    printf '%s\n' "LogLevel INFO" > "/etc/ssh/sshd_config.d/01-complianceascode-reinforce-os-defaults.conf"
    cat "/etc/ssh/sshd_config.d/01-complianceascode-reinforce-os-defaults.conf.bak" >> "/etc/ssh/sshd_config.d/01-complianceascode-reinforce-os-defaults.conf"
    # Clean up after ourselves.
    rm "/etc/ssh/sshd_config.d/01-complianceascode-reinforce-os-defaults.conf.bak"

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | restrict

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - NIST-800-53-AC-17(a)
      - NIST-800-53-CM-6(a)
      - low_complexity
      - low_disruption
      - low_severity
      - no_reboot_needed
      - restrict_strategy
      - sshd_set_loglevel_info

    - name: Set LogLevel to INFO
      block:

      - name: Deduplicate values from /etc/ssh/sshd_config
        lineinfile:
          path: /etc/ssh/sshd_config
          create: false
          regexp: (?i)(?i)^\s*{{ "LogLevel"| regex_escape }}\s+
          state: absent

      - name: Check if /etc/ssh/sshd_config.d exists
        stat:
          path: /etc/ssh/sshd_config.d
        register: _etc_ssh_sshd_config_d_exists

      - name: Check if the parameter LogLevel is present in /etc/ssh/sshd_config.d
        find:
          paths: /etc/ssh/sshd_config.d
          recurse: 'yes'
          follow: 'no'
          contains: (?i)^\s*{{ "LogLevel"| regex_escape }}\s+
        register: _etc_ssh_sshd_config_d_has_parameter
        when: _etc_ssh_sshd_config_d_exists.stat.isdir is defined and _etc_ssh_sshd_config_d_exists.stat.isdir

      - name: Remove parameter from files in /etc/ssh/sshd_config.d
        lineinfile:
          path: '{{ item.path }}'
          create: false
          regexp: (?i)(?i)^\s*{{ "LogLevel"| regex_escape }}\s+
          state: absent
        with_items: '{{ _etc_ssh_sshd_config_d_has_parameter.files }}'
        when: _etc_ssh_sshd_config_d_has_parameter.matched

      - name: Insert correct line to /etc/ssh/sshd_config.d/01-complianceascode-reinforce-os-defaults.conf
        lineinfile:
          path: /etc/ssh/sshd_config.d/01-complianceascode-reinforce-os-defaults.conf
          create: true
          regexp: (?i)(?i)^\s*{{ "LogLevel"| regex_escape }}\s+
          line: LogLevel INFO
          state: present
          insertbefore: BOF
          validate: /usr/sbin/sshd -t -f %s
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-53-AC-17(a)
      - NIST-800-53-CM-6(a)
      - low_complexity
      - low_disruption
      - low_severity
      - no_reboot_needed
      - restrict_strategy
      - sshd_set_loglevel_info

    - name: Set LogLevel to INFO - set file mode for /etc/ssh/sshd_config.d/01-complianceascode-reinforce-os-defaults.conf
      ansible.builtin.file:
        path: /etc/ssh/sshd_config.d/01-complianceascode-reinforce-os-defaults.conf
        mode: '0600'
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-53-AC-17(a)
      - NIST-800-53-CM-6(a)
      - low_complexity
      - low_disruption
      - low_severity
      - no_reboot_needed
      - restrict_strategy
      - sshd_set_loglevel_info

#### Rule Set SSH authentication attempt limit [ref]

The `MaxAuthTries` parameter specifies the maximum number of authentication attempts permitted per connection. Once the number of failures reaches half this value, additional failures are logged. to set MaxAUthTries edit `/etc/ssh/sshd_config` as follows:

    MaxAuthTries 4

Rationale: | Setting the MaxAuthTries parameter to a low number will minimize the risk of successful brute force attacks to the SSH server.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_sshd_set_max_auth_tries

References:

ism | 0421, 0422, 0431, 0974, 1173, 1401, 1504, 1505, 1546, 1557, 1558, 1559, 1560, 1561
cis | 5.2.6
pcidss4 | 2.2.6, 2.2

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | restrict

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    sshd_max_auth_tries_value='4'

    mkdir -p /etc/ssh/sshd_config.d
    touch /etc/ssh/sshd_config.d/00-complianceascode-hardening.conf
    chmod 0600 /etc/ssh/sshd_config.d/00-complianceascode-hardening.conf

    LC_ALL=C sed -i "/^\s*MaxAuthTries\s\+/Id" "/etc/ssh/sshd_config"
    LC_ALL=C sed -i "/^\s*MaxAuthTries\s\+/Id" "/etc/ssh/sshd_config.d"/*.conf
    if [ -e "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf" ] ; then

        LC_ALL=C sed -i "/^\s*MaxAuthTries\s\+/Id" "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf"
    else
        touch "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf"
    fi
    # make sure file has newline at the end
    sed -i -e '$a\' "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf"

    cp "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf" "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf.bak"
    # Insert at the beginning of the file
    printf '%s\n' "MaxAuthTries $sshd_max_auth_tries_value" > "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf"
    cat "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf.bak" >> "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf"
    # Clean up after ourselves.
    rm "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf.bak"

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | restrict

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy
      - sshd_set_max_auth_tries
    - name: XCCDF Value sshd_max_auth_tries_value # promote to variable
      set_fact:
        sshd_max_auth_tries_value: !!str 4
      tags:
        - always

    - name: Set SSH authentication attempt limit
      block:

      - name: Deduplicate values from /etc/ssh/sshd_config
        lineinfile:
          path: /etc/ssh/sshd_config
          create: false
          regexp: (?i)(?i)^\s*{{ "MaxAuthTries"| regex_escape }}\s+
          state: absent

      - name: Check if /etc/ssh/sshd_config.d exists
        stat:
          path: /etc/ssh/sshd_config.d
        register: _etc_ssh_sshd_config_d_exists

      - name: Check if the parameter MaxAuthTries is present in /etc/ssh/sshd_config.d
        find:
          paths: /etc/ssh/sshd_config.d
          recurse: 'yes'
          follow: 'no'
          contains: (?i)^\s*{{ "MaxAuthTries"| regex_escape }}\s+
        register: _etc_ssh_sshd_config_d_has_parameter
        when: _etc_ssh_sshd_config_d_exists.stat.isdir is defined and _etc_ssh_sshd_config_d_exists.stat.isdir

      - name: Remove parameter from files in /etc/ssh/sshd_config.d
        lineinfile:
          path: '{{ item.path }}'
          create: false
          regexp: (?i)(?i)^\s*{{ "MaxAuthTries"| regex_escape }}\s+
          state: absent
        with_items: '{{ _etc_ssh_sshd_config_d_has_parameter.files }}'
        when: _etc_ssh_sshd_config_d_has_parameter.matched

      - name: Insert correct line to /etc/ssh/sshd_config.d/00-complianceascode-hardening.conf
        lineinfile:
          path: /etc/ssh/sshd_config.d/00-complianceascode-hardening.conf
          create: true
          regexp: (?i)(?i)^\s*{{ "MaxAuthTries"| regex_escape }}\s+
          line: MaxAuthTries {{ sshd_max_auth_tries_value }}
          state: present
          insertbefore: BOF
          validate: /usr/sbin/sshd -t -f %s
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy
      - sshd_set_max_auth_tries

    - name: Set SSH authentication attempt limit - set file mode for /etc/ssh/sshd_config.d/00-complianceascode-hardening.conf
      ansible.builtin.file:
        path: /etc/ssh/sshd_config.d/00-complianceascode-hardening.conf
        mode: '0600'
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy
      - sshd_set_max_auth_tries

#### Rule Set SSH MaxSessions limit [ref]

The `MaxSessions` parameter specifies the maximum number of open sessions permitted from a given connection. To set MaxSessions edit `/etc/ssh/sshd_config` as follows:

    MaxSessions 10

Rationale: | To protect a system from denial of service due to a large number of concurrent sessions, use the rate limiting function of MaxSessions to protect availability of sshd logins and prevent overwhelming the daemon.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_sshd_set_max_sessions

References:

cis | 5.2.22
pcidss4 | 2.2.6, 2.2

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | restrict

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    var_sshd_max_sessions='10'

    mkdir -p /etc/ssh/sshd_config.d
    touch /etc/ssh/sshd_config.d/00-complianceascode-hardening.conf
    chmod 0600 /etc/ssh/sshd_config.d/00-complianceascode-hardening.conf

    LC_ALL=C sed -i "/^\s*MaxSessions\s\+/Id" "/etc/ssh/sshd_config"
    LC_ALL=C sed -i "/^\s*MaxSessions\s\+/Id" "/etc/ssh/sshd_config.d"/*.conf
    if [ -e "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf" ] ; then

        LC_ALL=C sed -i "/^\s*MaxSessions\s\+/Id" "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf"
    else
        touch "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf"
    fi
    # make sure file has newline at the end
    sed -i -e '$a\' "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf"

    cp "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf" "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf.bak"
    # Insert at the beginning of the file
    printf '%s\n' "MaxSessions $var_sshd_max_sessions" > "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf"
    cat "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf.bak" >> "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf"
    # Clean up after ourselves.
    rm "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf.bak"

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | restrict

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy
      - sshd_set_max_sessions
    - name: XCCDF Value var_sshd_max_sessions # promote to variable
      set_fact:
        var_sshd_max_sessions: !!str 10
      tags:
        - always

    - name: Set SSH MaxSessions limit
      block:

      - name: Deduplicate values from /etc/ssh/sshd_config
        lineinfile:
          path: /etc/ssh/sshd_config
          create: false
          regexp: (?i)(?i)^\s*{{ "MaxSessions"| regex_escape }}\s+
          state: absent

      - name: Check if /etc/ssh/sshd_config.d exists
        stat:
          path: /etc/ssh/sshd_config.d
        register: _etc_ssh_sshd_config_d_exists

      - name: Check if the parameter MaxSessions is present in /etc/ssh/sshd_config.d
        find:
          paths: /etc/ssh/sshd_config.d
          recurse: 'yes'
          follow: 'no'
          contains: (?i)^\s*{{ "MaxSessions"| regex_escape }}\s+
        register: _etc_ssh_sshd_config_d_has_parameter
        when: _etc_ssh_sshd_config_d_exists.stat.isdir is defined and _etc_ssh_sshd_config_d_exists.stat.isdir

      - name: Remove parameter from files in /etc/ssh/sshd_config.d
        lineinfile:
          path: '{{ item.path }}'
          create: false
          regexp: (?i)(?i)^\s*{{ "MaxSessions"| regex_escape }}\s+
          state: absent
        with_items: '{{ _etc_ssh_sshd_config_d_has_parameter.files }}'
        when: _etc_ssh_sshd_config_d_has_parameter.matched

      - name: Insert correct line to /etc/ssh/sshd_config.d/00-complianceascode-hardening.conf
        lineinfile:
          path: /etc/ssh/sshd_config.d/00-complianceascode-hardening.conf
          create: true
          regexp: (?i)(?i)^\s*{{ "MaxSessions"| regex_escape }}\s+
          line: MaxSessions {{ var_sshd_max_sessions }}
          state: present
          insertbefore: BOF
          validate: /usr/sbin/sshd -t -f %s
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy
      - sshd_set_max_sessions

    - name: Set SSH MaxSessions limit - set file mode for /etc/ssh/sshd_config.d/00-complianceascode-hardening.conf
      ansible.builtin.file:
        path: /etc/ssh/sshd_config.d/00-complianceascode-hardening.conf
        mode: '0600'
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy
      - sshd_set_max_sessions

#### Rule Ensure SSH MaxStartups is configured [ref]

The MaxStartups parameter specifies the maximum number of concurrent unauthenticated connections to the SSH daemon. Additional connections will be dropped until authentication succeeds or the LoginGraceTime expires for a connection. To configure MaxStartups, you should add or edit the following line in the `/etc/ssh/sshd_config` file:

    MaxStartups 10:30:60

Rationale: | To protect a system from denial of service due to a large number of pending authentication connection attempts, use the rate limiting function of MaxStartups to protect availability of sshd logins and prevent overwhelming the daemon.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_sshd_set_maxstartups

References:

cis | 5.2.21
pcidss4 | 2.2.6, 2.2

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | restrict

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    var_sshd_set_maxstartups='10:30:60'

    mkdir -p /etc/ssh/sshd_config.d
    touch /etc/ssh/sshd_config.d/00-complianceascode-hardening.conf
    chmod 0600 /etc/ssh/sshd_config.d/00-complianceascode-hardening.conf

    LC_ALL=C sed -i "/^\s*MaxStartups\s\+/Id" "/etc/ssh/sshd_config"
    LC_ALL=C sed -i "/^\s*MaxStartups\s\+/Id" "/etc/ssh/sshd_config.d"/*.conf
    if [ -e "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf" ] ; then

        LC_ALL=C sed -i "/^\s*MaxStartups\s\+/Id" "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf"
    else
        touch "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf"
    fi
    # make sure file has newline at the end
    sed -i -e '$a\' "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf"

    cp "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf" "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf.bak"
    # Insert at the beginning of the file
    printf '%s\n' "MaxStartups $var_sshd_set_maxstartups" > "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf"
    cat "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf.bak" >> "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf"
    # Clean up after ourselves.
    rm "/etc/ssh/sshd_config.d/00-complianceascode-hardening.conf.bak"

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | restrict

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy
      - sshd_set_maxstartups
    - name: XCCDF Value var_sshd_set_maxstartups # promote to variable
      set_fact:
        var_sshd_set_maxstartups: !!str 10:30:60
      tags:
        - always

    - name: Ensure SSH MaxStartups is configured
      block:

      - name: Deduplicate values from /etc/ssh/sshd_config
        lineinfile:
          path: /etc/ssh/sshd_config
          create: false
          regexp: (?i)(?i)^\s*{{ "MaxStartups"| regex_escape }}\s+
          state: absent

      - name: Check if /etc/ssh/sshd_config.d exists
        stat:
          path: /etc/ssh/sshd_config.d
        register: _etc_ssh_sshd_config_d_exists

      - name: Check if the parameter MaxStartups is present in /etc/ssh/sshd_config.d
        find:
          paths: /etc/ssh/sshd_config.d
          recurse: 'yes'
          follow: 'no'
          contains: (?i)^\s*{{ "MaxStartups"| regex_escape }}\s+
        register: _etc_ssh_sshd_config_d_has_parameter
        when: _etc_ssh_sshd_config_d_exists.stat.isdir is defined and _etc_ssh_sshd_config_d_exists.stat.isdir

      - name: Remove parameter from files in /etc/ssh/sshd_config.d
        lineinfile:
          path: '{{ item.path }}'
          create: false
          regexp: (?i)(?i)^\s*{{ "MaxStartups"| regex_escape }}\s+
          state: absent
        with_items: '{{ _etc_ssh_sshd_config_d_has_parameter.files }}'
        when: _etc_ssh_sshd_config_d_has_parameter.matched

      - name: Insert correct line to /etc/ssh/sshd_config.d/00-complianceascode-hardening.conf
        lineinfile:
          path: /etc/ssh/sshd_config.d/00-complianceascode-hardening.conf
          create: true
          regexp: (?i)(?i)^\s*{{ "MaxStartups"| regex_escape }}\s+
          line: MaxStartups {{ var_sshd_set_maxstartups }}
          state: present
          insertbefore: BOF
          validate: /usr/sbin/sshd -t -f %s
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy
      - sshd_set_maxstartups

    - name: Ensure SSH MaxStartups is configured - set file mode for /etc/ssh/sshd_config.d/00-complianceascode-hardening.conf
      ansible.builtin.file:
        path: /etc/ssh/sshd_config.d/00-complianceascode-hardening.conf
        mode: '0600'
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy
      - sshd_set_maxstartups

#### Rule Use Only FIPS 140-2 Validated Ciphers [ref]

Limit the ciphers to those algorithms which are FIPS-approved. Counter (CTR) mode is also preferred over cipher-block chaining (CBC) mode. The following line in `/etc/ssh/sshd_config` demonstrates use of FIPS-approved ciphers:

    Ciphers aes128-ctr,aes192-ctr,aes256-ctr,aes128-cbc,3des-cbc,aes192-cbc,aes256-cbc

The man page `sshd_config(5)` contains a list of supported ciphers. The rule is parametrized to use the following ciphers: `aes128-ctr,aes192-ctr,aes256-ctr,aes128-cbc,3des-cbc,aes192-cbc,aes256-cbc,rijndael-cbc@lysator.liu.se`.
Warning: The system needs to be rebooted for these changes to take effect.
Warning: System Crypto Modules must be provided by a vendor that undergoes FIPS-140 certifications. FIPS-140 is applicable to all Federal agencies that use cryptographic-based security systems to protect sensitive information in computer and telecommunication systems (including voice systems) as defined in Section 5131 of the Information Technology Management Reform Act of 1996, Public Law 104-106. This standard shall be used in designing and implementing cryptographic modules that Federal departments and agencies operate or are operated for them under contract. See https://nvlpubs.nist.gov/nistpubs/FIPS/NIST.FIPS.140-2.pdf To meet this, the system has to have cryptographic software provided by a vendor that has undergone this certification. This means providing documentation, test results, design information, and independent third party review by an accredited lab. While open source software is capable of meeting this, it does not meet FIPS-140 unless the vendor submits to this process.

Rationale:

Unapproved mechanisms that are used for authentication to the cryptographic module are not verified and therefore cannot be relied upon to provide confidentiality or integrity, and system data may be compromised.
Operating systems utilizing encryption are required to use FIPS-compliant mechanisms for authenticating to cryptographic modules.
FIPS 140-2 is the current standard for validating that mechanisms used to access cryptographic modules utilize authentication that meets industry and government requirements. For government systems, this allows Security Levels 1, 2, 3, or 4 for use on Ubuntu 20.04.

Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_sshd_use_approved_ciphers

References:

cis-csc | 1, 11, 12, 14, 15, 16, 18, 3, 5, 6, 8, 9
cjis | 5.5.6
cobit5 | APO11.04, APO13.01, BAI03.05, BAI10.01, BAI10.02, BAI10.03, BAI10.05, DSS01.04, DSS05.02, DSS05.03, DSS05.04, DSS05.05, DSS05.07, DSS05.10, DSS06.03, DSS06.06, DSS06.10, MEA02.01
cui | 3.1.13, 3.13.11, 3.13.8
disa | CCI-000068, CCI-000366, CCI-000803, CCI-000877, CCI-002890, CCI-003123
hipaa | 164.308(b)(1), 164.308(b)(2), 164.312(e)(1), 164.312(e)(2)(i), 164.312(e)(2)(ii), 164.314(b)(2)(i)
isa-62443-2009 | 4.3.3.2.2, 4.3.3.3.9, 4.3.3.5.1, 4.3.3.5.2, 4.3.3.5.3, 4.3.3.5.4, 4.3.3.5.5, 4.3.3.5.6, 4.3.3.5.7, 4.3.3.5.8, 4.3.3.6.1, 4.3.3.6.2, 4.3.3.6.3, 4.3.3.6.4, 4.3.3.6.5, 4.3.3.6.6, 4.3.3.6.7, 4.3.3.6.8, 4.3.3.6.9, 4.3.3.7.1, 4.3.3.7.2, 4.3.3.7.3, 4.3.3.7.4, 4.3.4.3.2, 4.3.4.3.3, 4.3.4.4.7, 4.4.2.1, 4.4.2.2, 4.4.2.4
isa-62443-2013 | SR 1.1, SR 1.10, SR 1.11, SR 1.12, SR 1.13, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.6, SR 1.7, SR 1.8, SR 1.9, SR 2.1, SR 2.10, SR 2.11, SR 2.12, SR 2.2, SR 2.3, SR 2.4, SR 2.5, SR 2.6, SR 2.7, SR 2.8, SR 2.9, SR 3.1, SR 3.5, SR 3.8, SR 4.1, SR 4.3, SR 5.1, SR 5.2, SR 5.3, SR 7.1, SR 7.6
iso27001-2013 | A.11.2.6, A.12.1.2, A.12.4.1, A.12.4.2, A.12.4.3, A.12.4.4, A.12.5.1, A.12.6.2, A.12.7.1, A.13.1.1, A.13.2.1, A.14.1.3, A.14.2.2, A.14.2.3, A.14.2.4, A.18.1.4, A.6.1.2, A.6.2.1, A.6.2.2, A.7.1.1, A.9.1.2, A.9.2.1, A.9.2.2, A.9.2.3, A.9.2.4, A.9.2.6, A.9.3.1, A.9.4.1, A.9.4.2, A.9.4.3, A.9.4.4, A.9.4.5
nist | CM-6(a), AC-17(a), AC-17(2), SC-13, MA-4(6), IA-5(1)(c), SC-12(2), SC-12(3)
nist-csf | PR.AC-1, PR.AC-3, PR.AC-4, PR.AC-6, PR.AC-7, PR.IP-1, PR.PT-1, PR.PT-3, PR.PT-4
os-srg | SRG-OS-000033-GPOS-00014, SRG-OS-000120-GPOS-00061, SRG-OS-000125-GPOS-00065, SRG-OS-000250-GPOS-00093, SRG-OS-000393-GPOS-00173, SRG-OS-000394-GPOS-00174
cis | 5.2.12
pcidss4 | 2.2.7, 2.2

Remediation Shell script ⇲

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    sshd_approved_ciphers='aes128-ctr,aes192-ctr,aes256-ctr,aes128-cbc,3des-cbc,aes192-cbc,aes256-cbc,rijndael-cbc@lysator.liu.se'

    # Strip any search characters in the key arg so that the key can be replaced without
    # adding any search characters to the config file.
    stripped_key=$(sed 's/[\^=\$,;+]*//g' <<< "^Ciphers")

    # shellcheck disable=SC2059
    printf -v formatted_output "%s %s" "$stripped_key" "$sshd_approved_ciphers"

    # If the key exists, change it. Otherwise, add it to the config_file.
    # We search for the key string followed by a word boundary (matched by \>),
    # so if we search for 'setting', 'setting2' won't match.
    if LC_ALL=C grep -q -m 1 -i -e "^Ciphers\\>" "/etc/ssh/sshd_config"; then
        escaped_formatted_output=$(sed -e 's|/|\\/|g' <<< "$formatted_output")
        LC_ALL=C sed -i --follow-symlinks "s/^Ciphers\\>.*/$escaped_formatted_output/gi" "/etc/ssh/sshd_config"
    else
        if [[ -s "/etc/ssh/sshd_config" ]] && [[ -n "$(tail -c 1 -- "/etc/ssh/sshd_config" || true)" ]]; then
            LC_ALL=C sed -i --follow-symlinks '$a'\\ "/etc/ssh/sshd_config"
        fi
        printf '%s\n' "$formatted_output" >> "/etc/ssh/sshd_config"
    fi

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | restrict

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - CJIS-5.5.6
      - NIST-800-171-3.1.13
      - NIST-800-171-3.13.11
      - NIST-800-171-3.13.8
      - NIST-800-53-AC-17(2)
      - NIST-800-53-AC-17(a)
      - NIST-800-53-CM-6(a)
      - NIST-800-53-IA-5(1)(c)
      - NIST-800-53-MA-4(6)
      - NIST-800-53-SC-12(2)
      - NIST-800-53-SC-12(3)
      - NIST-800-53-SC-13
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.7
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy
      - sshd_use_approved_ciphers
    - name: XCCDF Value sshd_approved_ciphers # promote to variable
      set_fact:
        sshd_approved_ciphers: !!str aes128-ctr,aes192-ctr,aes256-ctr,aes128-cbc,3des-cbc,aes192-cbc,aes256-cbc,rijndael-cbc@lysator.liu.se
      tags:
        - always

    - name: Use Only FIPS 140-2 Validated Ciphers
      block:

      - name: Check for duplicate values
        lineinfile:
          path: /etc/ssh/sshd_config
          create: true
          regexp: (?i)(?i)^\s*Ciphers\s+
          state: absent
        check_mode: true
        changed_when: false
        register: dupes

      - name: Deduplicate values from /etc/ssh/sshd_config
        lineinfile:
          path: /etc/ssh/sshd_config
          create: true
          regexp: (?i)(?i)^\s*Ciphers\s+
          state: absent
        when: dupes.found is defined and dupes.found > 1

      - name: Insert correct line to /etc/ssh/sshd_config
        lineinfile:
          path: /etc/ssh/sshd_config
          create: true
          regexp: (?i)(?i)^\s*Ciphers\s+
          line: Ciphers {{ sshd_approved_ciphers }}
          state: present
          insertbefore: BOF
          validate: /usr/sbin/sshd -t -f %s
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - CJIS-5.5.6
      - NIST-800-171-3.1.13
      - NIST-800-171-3.13.11
      - NIST-800-171-3.13.8
      - NIST-800-53-AC-17(2)
      - NIST-800-53-AC-17(a)
      - NIST-800-53-CM-6(a)
      - NIST-800-53-IA-5(1)(c)
      - NIST-800-53-MA-4(6)
      - NIST-800-53-SC-12(2)
      - NIST-800-53-SC-12(3)
      - NIST-800-53-SC-13
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.7
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy
      - sshd_use_approved_ciphers

#### Rule Use Only FIPS 140-2 Validated MACs [ref]

Limit the MACs to those hash algorithms which are FIPS-approved. The following line in `/etc/ssh/sshd_config` demonstrates use of FIPS-approved MACs:

    MACs hmac-sha2-512,hmac-sha2-256,hmac-sha1

The man page `sshd_config(5)` contains a list of supported MACs. The rule is parametrized to use the following MACs: `hmac-sha2-512,hmac-sha2-256,hmac-sha1,hmac-sha1-etm@openssh.com,hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com`.
Warning: The system needs to be rebooted for these changes to take effect.
Warning: System Crypto Modules must be provided by a vendor that undergoes FIPS-140 certifications. FIPS-140 is applicable to all Federal agencies that use cryptographic-based security systems to protect sensitive information in computer and telecommunication systems (including voice systems) as defined in Section 5131 of the Information Technology Management Reform Act of 1996, Public Law 104-106. This standard shall be used in designing and implementing cryptographic modules that Federal departments and agencies operate or are operated for them under contract. See https://nvlpubs.nist.gov/nistpubs/FIPS/NIST.FIPS.140-2.pdf To meet this, the system has to have cryptographic software provided by a vendor that has undergone this certification. This means providing documentation, test results, design information, and independent third party review by an accredited lab. While open source software is capable of meeting this, it does not meet FIPS-140 unless the vendor submits to this process.

Rationale: | DoD Information Systems are required to use FIPS-approved cryptographic hash functions. The only SSHv2 hash algorithms meeting this requirement is SHA2.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_sshd_use_approved_macs

References:

cis-csc | 1, 12, 13, 15, 16, 5, 8
cobit5 | APO01.06, APO13.01, DSS01.04, DSS05.02, DSS05.03, DSS05.04, DSS05.07, DSS06.02, DSS06.03
cui | 3.1.13, 3.13.11, 3.13.8
disa | CCI-000068, CCI-000803, CCI-000877, CCI-001453, CCI-003123
hipaa | 164.308(b)(1), 164.308(b)(2), 164.312(e)(1), 164.312(e)(2)(i), 164.312(e)(2)(ii), 164.314(b)(2)(i)
isa-62443-2009 | 4.3.3.5.1, 4.3.3.6.6
isa-62443-2013 | SR 1.1, SR 1.13, SR 1.2, SR 1.3, SR 1.4, SR 1.5, SR 1.7, SR 1.8, SR 1.9, SR 2.6, SR 3.1, SR 3.5, SR 3.8, SR 4.1, SR 4.3, SR 5.1, SR 5.2, SR 5.3, SR 7.1, SR 7.6
iso27001-2013 | A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.11.2.6, A.13.1.1, A.13.1.3, A.13.2.1, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, A.6.1.2, A.6.2.1, A.6.2.2, A.7.1.1, A.7.1.2, A.7.3.1, A.8.2.2, A.8.2.3, A.9.1.1, A.9.1.2, A.9.2.1, A.9.2.2, A.9.2.3, A.9.2.4, A.9.2.6, A.9.3.1, A.9.4.1, A.9.4.2, A.9.4.3, A.9.4.4, A.9.4.5
nist | CM-6(a), AC-17(a), AC-17(2), SC-13, MA-4(6), SC-12(2), SC-12(3)
nist-csf | PR.AC-1, PR.AC-3, PR.DS-5, PR.PT-4
os-srg | SRG-OS-000125-GPOS-00065, SRG-OS-000250-GPOS-00093, SRG-OS-000394-GPOS-00174
cis | 5.2.13
pcidss4 | 2.2.7, 2.2

Remediation Shell script ⇲

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    sshd_approved_macs='hmac-sha2-512,hmac-sha2-256,hmac-sha1,hmac-sha1-etm@openssh.com,hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com'

    # Strip any search characters in the key arg so that the key can be replaced without
    # adding any search characters to the config file.
    stripped_key=$(sed 's/[\^=\$,;+]*//g' <<< "^MACs")

    # shellcheck disable=SC2059
    printf -v formatted_output "%s %s" "$stripped_key" "$sshd_approved_macs"

    # If the key exists, change it. Otherwise, add it to the config_file.
    # We search for the key string followed by a word boundary (matched by \>),
    # so if we search for 'setting', 'setting2' won't match.
    if LC_ALL=C grep -q -m 1 -i -e "^MACs\\>" "/etc/ssh/sshd_config"; then
        escaped_formatted_output=$(sed -e 's|/|\\/|g' <<< "$formatted_output")
        LC_ALL=C sed -i --follow-symlinks "s/^MACs\\>.*/$escaped_formatted_output/gi" "/etc/ssh/sshd_config"
    else
        if [[ -s "/etc/ssh/sshd_config" ]] && [[ -n "$(tail -c 1 -- "/etc/ssh/sshd_config" || true)" ]]; then
            LC_ALL=C sed -i --follow-symlinks '$a'\\ "/etc/ssh/sshd_config"
        fi
        printf '%s\n' "$formatted_output" >> "/etc/ssh/sshd_config"
    fi

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

#### Rule Use Only Strong Key Exchange algorithms [ref]

Limit the Key Exchange to strong algorithms. The following line in `/etc/ssh/sshd_config` demonstrates use of those:

    KexAlgorithms curve25519-sha256,curve25519-sha256@libssh.org,ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group16-sha512,diffie-hellman-group18-sha512,diffie-hellman-group14-sha256

Rationale: | Key exchange is any method in cryptography by which cryptographic keys are exchanged between two parties, allowing use of a cryptographic algorithm. If the sender and receiver wish to exchange encrypted messages, each must be equipped to encrypt messages to be sent and decrypt messages received
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_sshd_use_strong_kex

References:

pcidss | Req-2.3
cis | 5.2.14
pcidss4 | 2.2.7, 2.2

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | restrict

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    sshd_strong_kex='curve25519-sha256,curve25519-sha256@libssh.org,ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group16-sha512,diffie-hellman-group18-sha512,diffie-hellman-group14-sha256'

    if [ -e "/etc/ssh/sshd_config" ] ; then

        LC_ALL=C sed -i "/^\s*KexAlgorithms\s\+/Id" "/etc/ssh/sshd_config"
    else
        touch "/etc/ssh/sshd_config"
    fi
    # make sure file has newline at the end
    sed -i -e '$a\' "/etc/ssh/sshd_config"

    cp "/etc/ssh/sshd_config" "/etc/ssh/sshd_config.bak"
    # Insert at the beginning of the file
    printf '%s\n' "KexAlgorithms $sshd_strong_kex" > "/etc/ssh/sshd_config"
    cat "/etc/ssh/sshd_config.bak" >> "/etc/ssh/sshd_config"
    # Clean up after ourselves.
    rm "/etc/ssh/sshd_config.bak"

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | restrict

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - PCI-DSS-Req-2.3
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.7
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy
      - sshd_use_strong_kex
    - name: XCCDF Value sshd_strong_kex # promote to variable
      set_fact:
        sshd_strong_kex: !!str curve25519-sha256,curve25519-sha256@libssh.org,ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group16-sha512,diffie-hellman-group18-sha512,diffie-hellman-group14-sha256
      tags:
        - always

    - name: Use Only Strong Key Exchange algorithms
      block:

      - name: Check for duplicate values
        lineinfile:
          path: /etc/ssh/sshd_config
          create: true
          regexp: (?i)(?i)^\s*KexAlgorithms\s+
          state: absent
        check_mode: true
        changed_when: false
        register: dupes

      - name: Deduplicate values from /etc/ssh/sshd_config
        lineinfile:
          path: /etc/ssh/sshd_config
          create: true
          regexp: (?i)(?i)^\s*KexAlgorithms\s+
          state: absent
        when: dupes.found is defined and dupes.found > 1

      - name: Insert correct line to /etc/ssh/sshd_config
        lineinfile:
          path: /etc/ssh/sshd_config
          create: true
          regexp: (?i)(?i)^\s*KexAlgorithms\s+
          line: KexAlgorithms {{ sshd_strong_kex }}
          state: present
          insertbefore: BOF
          validate: /usr/sbin/sshd -t -f %s
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - PCI-DSS-Req-2.3
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.7
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - restrict_strategy
      - sshd_use_strong_kex

#### Rule Verify Group Who Owns SSH Server config file [ref]

To properly set the group owner of `/etc/ssh/sshd_config`, run the command:

    $ sudo chgrp root /etc/ssh/sshd_config

Rationale: | Service configuration files enable or disable features of their respective services that if configured incorrectly can lead to insecure and vulnerable configurations. Therefore, service configuration files should be owned by the correct group to prevent unauthorized changes.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_file_groupowner_sshd_config

References:

cis-csc | 12, 13, 14, 15, 16, 18, 3, 5
cobit5 | APO01.06, DSS05.04, DSS05.07, DSS06.02
disa | CCI-000366
isa-62443-2009 | 4.3.3.7.3
isa-62443-2013 | SR 2.1, SR 5.2
iso27001-2013 | A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.13.1.1, A.13.1.3, A.13.2.1, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, A.6.1.2, A.7.1.1, A.7.1.2, A.7.3.1, A.8.2.2, A.8.2.3, A.9.1.1, A.9.1.2, A.9.2.3, A.9.4.1, A.9.4.4, A.9.4.5
nerc-cip | CIP-003-8 R5.1.1, CIP-003-8 R5.3, CIP-004-6 R2.3, CIP-007-3 R2.1, CIP-007-3 R2.2, CIP-007-3 R2.3, CIP-007-3 R5.1, CIP-007-3 R5.1.1, CIP-007-3 R5.1.2
nist | AC-17(a), CM-6(a), AC-6(1)
nist-csf | PR.AC-4, PR.DS-5
os-srg | SRG-OS-000480-GPOS-00227
cis | 5.2.1
anssi | R50

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    chgrp 0 /etc/ssh/sshd_config

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - NIST-800-53-AC-17(a)
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - configure_strategy
      - file_groupowner_sshd_config
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Test for existence /etc/ssh/sshd_config
      stat:
        path: /etc/ssh/sshd_config
      register: file_exists
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-53-AC-17(a)
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - configure_strategy
      - file_groupowner_sshd_config
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Ensure group owner 0 on /etc/ssh/sshd_config
      file:
        path: /etc/ssh/sshd_config
        group: '0'
      when:
      - '"linux-base" in ansible_facts.packages'
      - file_exists.stat is defined and file_exists.stat.exists
      tags:
      - NIST-800-53-AC-17(a)
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - configure_strategy
      - file_groupowner_sshd_config
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

#### Rule Verify Owner on SSH Server config file [ref]

To properly set the owner of `/etc/ssh/sshd_config`, run the command:

    $ sudo chown root /etc/ssh/sshd_config

Rationale: | Service configuration files enable or disable features of their respective services that if configured incorrectly can lead to insecure and vulnerable configurations. Therefore, service configuration files should be owned by the correct group to prevent unauthorized changes.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_file_owner_sshd_config

References:

cis-csc | 12, 13, 14, 15, 16, 18, 3, 5
cobit5 | APO01.06, DSS05.04, DSS05.07, DSS06.02
disa | CCI-000366
isa-62443-2009 | 4.3.3.7.3
isa-62443-2013 | SR 2.1, SR 5.2
iso27001-2013 | A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.13.1.1, A.13.1.3, A.13.2.1, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, A.6.1.2, A.7.1.1, A.7.1.2, A.7.3.1, A.8.2.2, A.8.2.3, A.9.1.1, A.9.1.2, A.9.2.3, A.9.4.1, A.9.4.4, A.9.4.5
nerc-cip | CIP-003-8 R5.1.1, CIP-003-8 R5.3, CIP-004-6 R2.3, CIP-007-3 R2.1, CIP-007-3 R2.2, CIP-007-3 R2.3, CIP-007-3 R5.1, CIP-007-3 R5.1.1, CIP-007-3 R5.1.2
nist | AC-17(a), CM-6(a), AC-6(1)
nist-csf | PR.AC-4, PR.DS-5
os-srg | SRG-OS-000480-GPOS-00227
cis | 5.2.1
anssi | R50

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    chown 0 /etc/ssh/sshd_config

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - NIST-800-53-AC-17(a)
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - configure_strategy
      - file_owner_sshd_config
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Test for existence /etc/ssh/sshd_config
      stat:
        path: /etc/ssh/sshd_config
      register: file_exists
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-53-AC-17(a)
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - configure_strategy
      - file_owner_sshd_config
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Ensure owner 0 on /etc/ssh/sshd_config
      file:
        path: /etc/ssh/sshd_config
        owner: '0'
      when:
      - '"linux-base" in ansible_facts.packages'
      - file_exists.stat is defined and file_exists.stat.exists
      tags:
      - NIST-800-53-AC-17(a)
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - configure_strategy
      - file_owner_sshd_config
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

#### Rule Verify Permissions on SSH Server config file [ref]

To properly set the permissions of `/etc/ssh/sshd_config`, run the command:

    $ sudo chmod 0600 /etc/ssh/sshd_config

Rationale: | Service configuration files enable or disable features of their respective services that if configured incorrectly can lead to insecure and vulnerable configurations. Therefore, service configuration files should be owned by the correct group to prevent unauthorized changes.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_file_permissions_sshd_config

References:

cis-csc | 12, 13, 14, 15, 16, 18, 3, 5
cobit5 | APO01.06, DSS05.04, DSS05.07, DSS06.02
disa | CCI-000366
isa-62443-2009 | 4.3.3.7.3
isa-62443-2013 | SR 2.1, SR 5.2
iso27001-2013 | A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.13.1.1, A.13.1.3, A.13.2.1, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, A.6.1.2, A.7.1.1, A.7.1.2, A.7.3.1, A.8.2.2, A.8.2.3, A.9.1.1, A.9.1.2, A.9.2.3, A.9.4.1, A.9.4.4, A.9.4.5
nerc-cip | CIP-003-8 R5.1.1, CIP-003-8 R5.3, CIP-004-6 R2.3, CIP-007-3 R2.1, CIP-007-3 R2.2, CIP-007-3 R2.3, CIP-007-3 R5.1, CIP-007-3 R5.1.1, CIP-007-3 R5.1.2
nist | AC-17(a), CM-6(a), AC-6(1)
nist-csf | PR.AC-4, PR.DS-5
os-srg | SRG-OS-000480-GPOS-00227
cis | 5.2.1
anssi | R50
pcidss4 | 2.2.6, 2.2

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    chmod u-xs,g-xwrs,o-xwrt /etc/ssh/sshd_config

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - NIST-800-53-AC-17(a)
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_permissions_sshd_config
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Test for existence /etc/ssh/sshd_config
      stat:
        path: /etc/ssh/sshd_config
      register: file_exists
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-53-AC-17(a)
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_permissions_sshd_config
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Ensure permission u-xs,g-xwrs,o-xwrt on /etc/ssh/sshd_config
      file:
        path: /etc/ssh/sshd_config
        mode: u-xs,g-xwrs,o-xwrt
      when:
      - '"linux-base" in ansible_facts.packages'
      - file_exists.stat is defined and file_exists.stat.exists
      tags:
      - NIST-800-53-AC-17(a)
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_permissions_sshd_config
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

#### Rule Verify Permissions on SSH Server Private *_key Key Files [ref]

SSH server private keys - files that match the `/etc/ssh/*_key` glob, have to have restricted permissions. If those files are owned by the `root` user and the `root` group, they have to have the `0600` permission or stricter. Warning: Remediation is not possible at bootable container build time because SSH host keys are generated post-deployment.
Rationale: | If an unauthorized user obtains the private SSH host key file, the host could be impersonated.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_file_permissions_sshd_private_key

References:

cis-csc | 12, 13, 14, 15, 16, 18, 3, 5
cobit5 | APO01.06, DSS05.04, DSS05.07, DSS06.02
cui | 3.1.13, 3.13.10
disa | CCI-000366
isa-62443-2009 | 4.3.3.7.3
isa-62443-2013 | SR 2.1, SR 5.2
iso27001-2013 | A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.13.1.1, A.13.1.3, A.13.2.1, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, A.6.1.2, A.7.1.1, A.7.1.2, A.7.3.1, A.8.2.2, A.8.2.3, A.9.1.1, A.9.1.2, A.9.2.3, A.9.4.1, A.9.4.4, A.9.4.5
nerc-cip | CIP-003-8 R5.1.1, CIP-003-8 R5.3, CIP-004-6 R2.3, CIP-007-3 R2.1, CIP-007-3 R2.2, CIP-007-3 R2.3, CIP-007-3 R5.1, CIP-007-3 R5.1.1, CIP-007-3 R5.1.2
nist | AC-17(a), CM-6(a), AC-6(1)
nist-csf | PR.AC-4, PR.DS-5
pcidss | Req-2.2.4
os-srg | SRG-OS-000480-GPOS-00227
cis | 5.2.2
anssi | R50
pcidss4 | 2.2.6, 2.2

Remediation Shell script ⇲

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    for keyfile in /etc/ssh/*_key; do
        test -f "$keyfile" || continue
        if test root:root = "$(stat -c "%U:%G" "$keyfile")"; then

    	chmod u-xs,g-xwrs,o-xwrt "$keyfile"

        else
            echo "Key-like file '$keyfile' is owned by an unexpected user:group combination"
        fi
    done

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - NIST-800-171-3.1.13
      - NIST-800-171-3.13.10
      - NIST-800-53-AC-17(a)
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - PCI-DSS-Req-2.2.4
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_permissions_sshd_private_key
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Find root:root-owned keys
      ansible.builtin.command: find -H /etc/ssh/ -maxdepth 1 -user root -regex ".*_key$"
        -type f -group root -perm /u+xs,g+xwrs,o+xwrt
      register: root_owned_keys
      changed_when: false
      failed_when: false
      check_mode: false
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-171-3.1.13
      - NIST-800-171-3.13.10
      - NIST-800-53-AC-17(a)
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - PCI-DSS-Req-2.2.4
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_permissions_sshd_private_key
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Set permissions for root:root-owned keys
      ansible.builtin.file:
        path: '{{ item }}'
        mode: u-xs,g-xwrs,o-xwrt
        state: file
      with_items:
      - '{{ root_owned_keys.stdout_lines }}'
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-171-3.1.13
      - NIST-800-171-3.13.10
      - NIST-800-53-AC-17(a)
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - PCI-DSS-Req-2.2.4
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_permissions_sshd_private_key
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

Remediation Puppet snippet ⇲

    include ssh_private_key_perms

    class ssh_private_key_perms {
      exec { 'sshd_priv_key':
        command => "chmod 0640 /etc/ssh/*_key",
        path    => '/bin:/usr/bin'
      }
    }

#### Rule Verify Permissions on SSH Server Public *.pub Key Files [ref]

To properly set the permissions of `/etc/ssh/*.pub`, run the command:

    $ sudo chmod 0644 /etc/ssh/*.pub

Warning: Remediation is not possible at bootable container build time because SSH host keys are generated post-deployment.

Rationale: | If a public host key file is modified by an unauthorized user, the SSH service may be compromised.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_file_permissions_sshd_pub_key

References:

cis-csc | 12, 13, 14, 15, 16, 18, 3, 5
cobit5 | APO01.06, DSS05.04, DSS05.07, DSS06.02
cui | 3.1.13, 3.13.10
disa | CCI-000366
isa-62443-2009 | 4.3.3.7.3
isa-62443-2013 | SR 2.1, SR 5.2
iso27001-2013 | A.10.1.1, A.11.1.4, A.11.1.5, A.11.2.1, A.13.1.1, A.13.1.3, A.13.2.1, A.13.2.3, A.13.2.4, A.14.1.2, A.14.1.3, A.6.1.2, A.7.1.1, A.7.1.2, A.7.3.1, A.8.2.2, A.8.2.3, A.9.1.1, A.9.1.2, A.9.2.3, A.9.4.1, A.9.4.4, A.9.4.5
nerc-cip | CIP-003-8 R5.1.1, CIP-003-8 R5.3, CIP-004-6 R2.3, CIP-007-3 R2.1, CIP-007-3 R2.2, CIP-007-3 R2.3, CIP-007-3 R5.1, CIP-007-3 R5.1.1, CIP-007-3 R5.1.2
nist | AC-17(a), CM-6(a), AC-6(1)
nist-csf | PR.AC-4, PR.DS-5
pcidss | Req-2.2.4
os-srg | SRG-OS-000480-GPOS-00227
cis | 5.2.3
anssi | R50
pcidss4 | 2.2.6, 2.2

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    # Remediation is applicable only in certain platforms
    if dpkg-query --show --showformat='${db:Status-Status}
    ' 'linux-base' 2>/dev/null | grep -q ^installed; then

    find -L /etc/ssh/ -maxdepth 1 -perm /u+xs,g+xws,o+xwt  -type f -regextype posix-extended -regex '^.*\.pub$' -exec chmod u-xs,g-xws,o-xwt {} \;

    else
        >&2 echo 'Remediation is not applicable, nothing was done'
    fi

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | configure

    - name: Gather the package facts
      package_facts:
        manager: auto
      tags:
      - NIST-800-171-3.1.13
      - NIST-800-171-3.13.10
      - NIST-800-53-AC-17(a)
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - PCI-DSS-Req-2.2.4
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_permissions_sshd_pub_key
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Find /etc/ssh/ file(s)
      command: find -H /etc/ssh/ -maxdepth 1 -perm /u+xs,g+xws,o+xwt  -type f -regextype
        posix-extended -regex "^.*\.pub$"
      register: files_found
      changed_when: false
      failed_when: false
      check_mode: false
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-171-3.1.13
      - NIST-800-171-3.13.10
      - NIST-800-53-AC-17(a)
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - PCI-DSS-Req-2.2.4
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_permissions_sshd_pub_key
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

    - name: Set permissions for /etc/ssh/ file(s)
      file:
        path: '{{ item }}'
        mode: u-xs,g-xws,o-xwt
        state: file
      with_items:
      - '{{ files_found.stdout_lines }}'
      when: '"linux-base" in ansible_facts.packages'
      tags:
      - NIST-800-171-3.1.13
      - NIST-800-171-3.13.10
      - NIST-800-53-AC-17(a)
      - NIST-800-53-AC-6(1)
      - NIST-800-53-CM-6(a)
      - PCI-DSS-Req-2.2.4
      - PCI-DSSv4-2.2
      - PCI-DSSv4-2.2.6
      - configure_strategy
      - file_permissions_sshd_pub_key
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed

Remediation Puppet snippet ⇲

    include ssh_public_key_perms

    class ssh_public_key_perms {
      exec { 'sshd_pub_key':
        command => "chmod 0644 /etc/ssh/*.pub",
        path    => '/bin:/usr/bin'
      }
    }

Group X Window System Group contains 1 group and 1 rule
[ref] The X Window System implementation included with the system is called X.org.
Group Disable X Windows Group contains 1 rule

[ref] Unless there is a mission-critical reason for the system to run a graphical user interface, ensure X is not set to start automatically at boot and remove the X Windows software packages. There is usually no reason to run X Windows on a dedicated server system, as it increases the system's attack surface and consumes system resources. Administrators of server systems should instead login via SSH or on the text console.

#### Rule Remove the X Windows Package Group [ref]

By removing the xorg-x11-server-common package, the system no longer has X Windows installed. If X Windows is not installed then the system cannot boot into graphical user mode. This prevents the system from being accidentally or maliciously booted into a `graphical.target` mode. To do so, run the following command:

    $ sudo apt_get groupremove "X Window System"

    $ sudo apt_get remove xorg-x11-server-common

Warning: The installation and use of a Graphical User Interface (GUI) increases your attack vector and decreases your overall security posture. Removing the package xorg-x11-server-common package will remove the graphical target which might bring your system to an inconsistent state requiring additional configuration to access the system again. If a GUI is an operational requirement, a tailored profile that removes this rule should used before continuing installation.

Rationale: | Unnecessary service packages must not be installed to decrease the attack surface of the system. X windows has a long history of security vulnerabilities and should not be installed unless approved and documented.
Severity: | medium
Rule ID: | xccdf_org.ssgproject.content_rule_package_xorg-x11-server-common_removed

References:

cis-csc | 12, 15, 8
cobit5 | APO13.01, DSS01.04, DSS05.02, DSS05.03
disa | CCI-000366
isa-62443-2009 | 4.3.3.6.6
isa-62443-2013 | SR 1.13, SR 2.6, SR 3.1, SR 3.5, SR 3.8, SR 4.1, SR 4.3, SR 5.1, SR 5.2, SR 5.3, SR 7.1, SR 7.6
iso27001-2013 | A.11.2.6, A.13.1.1, A.13.2.1, A.14.1.3, A.6.2.1, A.6.2.2
nist | CM-7(a), CM-7(b), CM-6(a)
nist-csf | PR.AC-3, PR.PT-4
os-srg | SRG-OS-000480-GPOS-00227
cis | 2.2.2

Remediation Shell script ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    # CAUTION: This remediation script will remove xserver-xorg
    #	   from the system, and may remove any packages
    #	   that depend on xserver-xorg. Execute this
    #	   remediation AFTER testing on a non-production
    #	   system!

    DEBIAN_FRONTEND=noninteractive apt-get remove -y "xserver-xorg"

Remediation Ansible snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    - name: Ensure xserver-xorg is removed
      package:
        name: xserver-xorg
        state: absent
      tags:
      - NIST-800-53-CM-6(a)
      - NIST-800-53-CM-7(a)
      - NIST-800-53-CM-7(b)
      - disable_strategy
      - low_complexity
      - low_disruption
      - medium_severity
      - no_reboot_needed
      - package_xorg-x11-server-common_removed

Remediation Puppet snippet ⇲

Complexity: | low
Disruption: | low
Reboot: | false
Strategy: | disable

    include remove_xserver-xorg

    class remove_xserver-xorg {
      package { 'xserver-xorg':
        ensure => 'purged',
      }
    }

Red Hat and Red Hat Enterprise Linux are either registered trademarks or trademarks of Red Hat, Inc. in the United States and other countries. All other names are registered trademarks or trademarks of their respective companies.