## Guide to the Secure Configuration of SUSE Linux Enterprise 11

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 SUSE Linux Enterprise 11. 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 for SUSE Linux Enterprise 11, 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 ID | (default)

## Revision History

Current version: 0.1.31

- draft (as of 2017-08-11)

## Platforms

- cpe:/o:suse:linux_enterprise_server:11

## Table of Contents

1. Remediation functions used by the SCAP Security Guide Project
2. Introduction

1. General Principles
2. How to Use This Guide

3. System Settings

1. File Permissions and Masks

## Checklist

### Remediation functions used by the SCAP Security Guide Project [ref]group

XCCDF form of the various remediation functions as used by remediation scripts from the SCAP Security Guide Project

### Introduction [ref]group

The purpose of this guidance is to provide security configuration recommendations and baselines for the SUSE Linux Enterprise 11 operating system. Recommended settings for the basic operating system are provided, as well as for many network services that the system can provide to other systems. The guide is intended for system administrators. Readers are assumed to possess basic system administration skills for Unix-like systems, as well as some familiarity with the product's documentation and administration conventions. Some instructions within this guide are complex. All directions should be followed completely and with understanding of their effects in order to avoid serious adverse effects on the system and its security.

### General Principles [ref]group

The following general principles motivate much of the advice in this guide and should also influence any configuration decisions that are not explicitly covered.

### Encrypt Transmitted Data Whenever Possible [ref]group

Data transmitted over a network, whether wired or wireless, is susceptible to passive monitoring. Whenever practical solutions for encrypting such data exist, they should be applied. Even if data is expected to be transmitted only over a local network, it should still be encrypted. Encrypting authentication data, such as passwords, is particularly important. Networks of SUSE Linux Enterprise 11 machines can and should be configured so that no unencrypted authentication data is ever transmitted between machines.

### Minimize Software to Minimize Vulnerability [ref]group

The simplest way to avoid vulnerabilities in software is to avoid installing that software. On SUSE Linux Enterprise 11, the RPM Package Manager (originally Red Hat Package Manager, abbreviated RPM) allows for careful management of the set of software packages installed on a system. Installed software contributes to system vulnerability in several ways. Packages that include setuid programs may provide local attackers a potential path to privilege escalation. Packages that include network services may give this opportunity to network-based attackers. Packages that include programs which are predictably executed by local users (e.g. after graphical login) may provide opportunities for trojan horses or other attack code to be run undetected. The number of software packages installed on a system can almost always be significantly pruned to include only the software for which there is an environmental or operational need.

### Run Different Network Services on Separate Systems [ref]group

Whenever possible, a server should be dedicated to serving exactly one network service. This limits the number of other services that can be compromised in the event that an attacker is able to successfully exploit a software flaw in one network service.

### Configure Security Tools to Improve System Robustness [ref]group

Several tools exist which can be effectively used to improve a system's resistance to and detection of unknown attacks. These tools can improve robustness against attack at the cost of relatively little configuration effort. In particular, this guide recommends and discusses the use of host-based firewalling, SELinux for protection against vulnerable services, and a logging and auditing infrastructure for detection of problems.

### Least Privilege [ref]group

Grant the least privilege necessary for user accounts and software to perform tasks. For example, `sudo` can be implemented to limit authorization to super user accounts on the system only to designated personnel. Another example is to limit logins on server systems to only those administrators who need to log into them in order to perform administration tasks. Using SELinux also follows the principle of least privilege: SELinux policy can confine software to perform only actions on the system that are specifically allowed. This can be far more restrictive than the actions permissible by the traditional Unix permissions model.

### How to Use This Guide [ref]group

Readers should heed the following points when using the guide.

### Read Sections Completely and in Order [ref]group

Each section may build on information and recommendations discussed in prior sections. Each section should be read and understood completely; instructions should never be blindly applied. Relevant discussion may occur after instructions for an action.

### Test in Non-Production Environment [ref]group

This guidance should always be tested in a non-production environment before deployment. This test environment should simulate the setup in which the system will be deployed as closely as possible.

### Root Shell Environment Assumed [ref]group

Most of the actions listed in this document are written with the assumption that they will be executed by the root user running the `/bin/bash` shell. Commands preceded with a hash mark (#) assume that the administrator will execute the commands as root, i.e. apply the command via `sudo` whenever possible, or use `su` to gain root privileges if `sudo` cannot be used. Commands which can be executed as a non-root user are are preceded by a dollar sign ($) prompt.

### Formatting Conventions [ref]group

Commands intended for shell execution, as well as configuration file text, are featured in a `monospace font`. Italics are used to indicate instances where the system administrator must substitute the appropriate information into a command or configuration file.

### Reboot Required [ref]group

A system reboot is implicitly required after some actions in order to complete the reconfiguration of the system. In many cases, the changes will not take effect until a reboot is performed. In order to ensure that changes are applied properly and to test functionality, always reboot the system after applying a set of recommendations from this guide.

### System Settings [ref]group

Contains rules that check correct system settings.

### File Permissions and Masks [ref]group

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 Red Hat Enterprise Linux 7 installations:

    $ mount -t xfs | awk '{print $3}'

For any systems that use a different local filesystem type, modify this command as appropriate.

### Verify Permissions on Important Files and Directories [ref]group

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.

### Verify Permissions on Files with Local Account Information and Credentials [ref]group

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.

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