# Generating the machine certificate

In this step, we generate certificates for each of the machines. Please note that both clients and servers need certificates. The certificate identifies each machine to the remote peer. The DNSName specified inside the certificate can

be specified inside the $<object>PermittedPeer config statements.

For now, we assume that a single person (or group) is responsible for the whole rsyslog system and thus it is OK if that single person is in possession of all machine’s private keys. This simplification permits us to use a somewhat less complicated way of generating the machine certificates. So, we generate both the private and public key on the CA (which is NOT a server!) and then copy them over to the respective machines.

If the roles of machine and CA administrators are split, the private key must be generated by the machine administrator. This is done via a certificate request. This request is then sent to the CA admin, which in turn generates the certificate (containing the public key). The CA admin then sends back the certificate to the machine admin, who installs it. That way, the CA admin never gets hold of the machine’s private key. Instructions for this mode will be given in a later revision of this document.

In any case, it is vital that the machine’s private key is protected. Anybody able to obtain that private key can impersonate as the machine to which it belongs, thus breaching your security.

## Sample Screen Session

Text in red is user input. Please note that for some questions, there is no user input given. This means the default was accepted by simply pressing the enter key.

Please note: you need to substitute the names specified below with values that match your environment. Most importantly, machine.example.net must be replaced by the actual name of the machine that will be using this certificate. For example, if you generate a certificate for a machine named “server.example.com”, you need to use that name. If you generate a certificate for “client.example.com”, you need to use this name. Make sure that each machine certificate has a unique name. If not, you can not apply proper access control.

    [root@rgf9dev sample]# certtool --generate-privkey --outfile key.pem --bits 2048
    Generating a 2048 bit RSA private key...
    [root@rgf9dev sample]# certtool --generate-request --load-privkey key.pem --outfile request.pem
    Generating a PKCS #10 certificate request...
    Country name (2 chars): US
    Organization name: SomeOrg
    Organizational unit name: SomeOU
    Locality name: Somewhere
    State or province name: CA
    Common name: machine.example.net
    UID:
    Enter a dnsName of the subject of the certificate:
    Enter the IP address of the subject of the certificate:
    Enter the e-mail of the subject of the certificate:
    Enter a challenge password:
    Does the certificate belong to an authority? (y/N): n
    Will the certificate be used for signing (DHE and RSA-EXPORT ciphersuites)? (y/N):
    Will the certificate be used for encryption (RSA ciphersuites)? (y/N):
    Is this a TLS web client certificate? (y/N): y
    Is this also a TLS web server certificate? (y/N): y
    [root@rgf9dev sample]# certtool --generate-certificate --load-request request.pem --outfile cert.pem --load-ca-certificate ca.pem --load-ca-privkey ca-key.pem
    Generating a signed certificate...
    Enter the certificate's serial number (decimal):

    Activation/Expiration time.
    The certificate will expire in (days): 1000

    Extensions.
    Do you want to honour the extensions from the request? (y/N):
    Does the certificate belong to an authority? (Y/N): n
    Will the certificate be used for IPsec IKE operations? (y/N):
    Is this a TLS web client certificate? (Y/N): y
    Is this also a TLS web server certificate? (Y/N): y
    Enter the dnsName of the subject of the certificate: machine.example.net {This is the name of the machine that will use the certificate}
    Enter the IP address of the subject of certificate:
    Will the certificate be used for signing (DHE and RSA-EXPORT ciphersuites)? (Y/N):
    Will the certificate be used for encryption (RSA ciphersuites)? (Y/N):
    X.509 Certificate Information:
        Version: 3
        Serial Number (hex): 485a3819
        Validity:
            Not Before: Thu Jun 19 10:42:54 UTC 2008
            Not After: Wed Mar 16 10:42:57 UTC 2011
        Subject: C=US,O=SomeOrg,OU=SomeOU,L=Somewhere,ST=CA,CN=machine.example.net
        Subject Public Key Algorithm: RSA
            Modulus (bits 2048):
                b2:4e:5b:a9:48:1e:ff:2e:73:a1:33:ee:d8:a2:af:ae
                2f:23:76:91:b8:39:94:00:23:f2:6f:25:ad:c9:6a:ab
                2d:e6:f3:62:d8:3e:6e:8a:d6:1e:3f:72:e5:d8:b9:e0
                d0:79:c2:94:21:65:0b:10:53:66:b0:36:a6:a7:cd:46
                1e:2c:6a:9b:79:c6:ee:c6:e2:ed:b0:a9:59:e2:49:da
                c7:e3:f0:1c:e0:53:98:87:0d:d5:28:db:a4:82:36:ed
                3a:1e:d1:5c:07:13:95:5d:b3:28:05:17:2a:2b:b6:8e
                8e:78:d2:cf:ac:87:13:15:fc:17:43:6b:15:c3:7d:b9
            Exponent:
                01:00:01
        Extensions:
            Basic Constraints (critical):
                Certificate Authority (CA): FALSE
            Key Purpose (not critical):
                TLS WWW Client.
                TLS WWW Server.
            Subject Alternative Name (not critical):
                DNSname: machine.example.net
            Subject Key Identifier (not critical):
                0ce1c3dbd19d31fa035b07afe2e0ef22d90b28ac
            Authority Key Identifier (not critical):
                fbfe968d10a73ae5b70d7b434886c8f872997b89
    Other Information:
        Public Key Id:
            0ce1c3dbd19d31fa035b07afe2e0ef22d90b28ac

    Is the above information ok? (Y/N): y

    Signing certificate...
    [root@rgf9dev sample]# rm -f request.pem
    [root@rgf9dev sample]# ls -l
    total 16
    -r-------- 1 root root  887 2008-06-19 12:33 ca-key.pem
    -rw-r--r-- 1 root root 1029 2008-06-19 12:36 ca.pem
    -rw-r--r-- 1 root root 1074 2008-06-19 12:43 cert.pem
    -rw-r--r-- 1 root root  887 2008-06-19 12:40 key.pem
    [root@rgf9dev sample]# # it may be a good idea to rename the files to indicate where they belong to
    [root@rgf9dev sample]# mv cert.pem machine-cert.pem
    [root@rgf9dev sample]# mv key.pem machine-key.pem
    [root@rgf9dev sample]#

## Distributing Files

Provide the machine with:

- a copy of ca.pem
- cert.pem
- key.pem

This is how the relevant part of rsyslog.conf looks on the target machine:

    global(
    DefaultNetstreamDriver="gtls"
    DefaultNetstreamDriverCAFile="/path/to/contrib/gnutls/ca.pem"
    DefaultNetstreamDriverCertFile="/path/to/contrib/gnutls/cert.pem"
    DefaultNetstreamDriverKeyFile="/path/to/contrib/gnutls/key.pem"
    )

Never provide anyone with ca-key.pem! Also, make sure nobody but the machine in question gets hold of key.pem.

See also

Help with configuring/using `Rsyslog`:

- Mailing list - best route for general questions
- GitHub: rsyslog source project - detailed questions, reporting issues that are believed to be bugs with `Rsyslog`
- Stack Exchange (View, Ask) - experimental support from rsyslog community

See also

Contributing to `Rsyslog`:

- Source project: rsyslog project README.
- Documentation: rsyslog-doc project README

Copyright 2008-2020 Rainer Gerhards (Großrinderfeld), and Others.