10.3.1. Procedure – Configuring TLS on the syslog-ng clients

Purpose: 

Complete the following steps on every syslog-ng client host. Examples are provided using both the legacy BSD-syslog protocol (using the network() driver) and the new IETF-syslog protocol standard (using the syslog() driver):

Steps: 

  1. Create an X.509 certificate for the syslog-ng client.

  2. Copy the certificate (for example client_cert.pem) and the matching private key (for example client.key) to the syslog-ng client host, for example into the /opt/syslog-ng/etc/syslog-ng/cert.d directory. The certificate must be a valid X.509 certificate in PEM format and must not be password-protected.

  3. Copy the CA certificate of the Certificate Authority (for example cacert.pem) that issued the certificate of the syslog-ng server (or the self-signed certificate of the syslog-ng server) to the syslog-ng client hosts, for example into the /opt/syslog-ng/etc/syslog-ng/ca.d directory.

    Issue the following command on the certificate: openssl x509 -noout -hash -in cacert.pem The result is a hash (for example 6d2962a8), a series of alphanumeric characters based on the Distinguished Name of the certificate.

    Issue the following command to create a symbolic link to the certificate that uses the hash returned by the previous command and the .0 suffix.

    ln -s cacert.pem 6d2962a8.0

  4. Add a destination statement to the syslog-ng configuration file that uses the tls( ca-dir(path_to_ca_directory) ) option and specify the directory using the CA certificate. The destination must use the network() or the syslog() destination driver, and the IP address and port parameters of the driver must point to the syslog-ng server. Include the client's certificate and private key in the tls() options.

    Example 10.4. A destination statement using mutual authentication

    The following destination encrypts the log messages using TLS and sends them to the 1999/TCP port of the syslog-ng server having the 10.1.2.3 IP address. The private key and the certificate file authenticating the client is also specified.

    destination demo_tls_destination {
        network("10.1.2.3" port(1999)
            transport("tls")
            tls( ca-dir("/opt/syslog-ng/etc/syslog-ng/ca.d")
                 key-file("/opt/syslog-ng/etc/syslog-ng/key.d/client.key")
                 cert-file("/opt/syslog-ng/etc/syslog-ng/cert.d/client_cert.pem")) ); };
    destination demo_tls_syslog_destination {
        syslog("10.1.2.3" port(1999)
            transport("tls")
                tls( ca-dir("/opt/syslog-ng/etc/syslog-ng/ca.d")
                     key-file("/opt/syslog-ng/etc/syslog-ng/key.d/client.key")
                     cert-file("/opt/syslog-ng/etc/syslog-ng/cert.d/client_cert.pem")) ); };
  5. Include the destination created in Step 2 in a log statement.

    Warning

    The encrypted connection between the server and the client fails if the Common Name or the subject_alt_name parameter of the server certificate does not the hostname or the IP address (as resolved from the syslog-ng clients and relays) of the server.

    Do not forget to update the certificate files when they expire.