man > AUDITD-PLUGINS(5)

AUDITD-PLUGINS(5)                  System Administration Utilities                 AUDITD-PLUGINS(5)

NAME
       auditd-plugins - realtime event receivers

DESCRIPTION
       auditd  can multiplex audit events in realtime. It takes audit events and distributes them to
       child programs that want to analyze events in realtime. When  the  audit  daemon  receives  a
       SIGTERM  or  SIGHUP, it passes that signal to its child processes so that can reload the con‐
       figuration or terminate.

       The child programs install a configuration file in a  plugins  directory  which  defaults  to
       /etc/audit/plugins.d. This can be controlled by a auditd.conf config option plugin_dir if the
       admin wished to locate plugins somewhere else. But auditd will install its plugins in the de‐
       fault location.

       The  plugin directory will be scanned and every plugin that is active will be started. If the
       plugin has a problem and exits, it will be started a maximum of max_restarts times  as  found
       in auditd.conf.

       Config file names are not allowed to have more than one '.' in the name or it will be treated
       as  a  backup copy and skipped. Config file options are given one per line with an equal sign
       between the keyword and its value. The available options are as follows:


       active The options for this are yes or no.

       direction
              The option is dictated by the plugin.  In or out are the only choices. You cannot make
              a plugin operate in a way it wasn't designed just by changing this option. This option
              is to give a clue to the event dispatcher about which direction events flow. NOTE: in‐
              bound events are not supported yet.

       path   This is the absolute path to the plugin executable. In the case of  internal  plugins,
              it would be the name of the plugin.

       type   This  tells the dispatcher how the plugin wants to be run. There is currently only one
              option, builtin , which is the default setting.

       args   This allows you to pass arguments to the child program. Generally plugins do not  take
              arguments  and  have their own config file that instructs them how they should be con‐
              figured. At the moment, there is a limit of 2 args.

       format The valid options for this are binary and string.  Binary passes the data  exactly  as
              the  audit event dispatcher gets it from the audit daemon. The string option tells the
              dispatcher to completely change the event into a string suitable for parsing with  the
              audit parsing library. The default value is string.


NOTE
       auditd  has  an  internal  queue  to hold events for plugins. (See the q_depth setting in au‐
       ditd.conf.) Plugins have to watch for and dequeue events as fast as possible and  queue  them
       internally  if  they  can't  be  immediately  processed. If the plugin is not able to dequeue
       records, the auditd internal queue will get filled. At any time, as root,  you  can  run  the
       following to check auditd's metrics:

       auditctl --signal cont ; sleep 1 ; cat /var/run/auditd.state

       If  auditd's  internal  queue fills, it cannot dequeue any events from the kernel backlog. If
       the kernel's backlog fills, it looks at the value of backlog_wait_time to delay all processes
       that generate an event to see if there is eventually room to add the event. This will  likely
       be noticed as slowing down various processes on the machine. The kernel's audit subsystem can
       be checked by running:

       auditctl -s

       When  tuning  the audit system's performance, you'd want to check both kernel and auditd met‐
       rics and adjust accordingly.


NOTES FOR DEVELOPERS
       When the audit daemon starts your plugin, you will be running as root. If  you  do  not  need
       root privileges, you should change uid/gid to lower chances of being a target for exploit. If
       you need to retain capabilities, using libcap-ng is the simplest way.

       Your environment is not going to be clean. You are inheriting many attributes from auditd it‐
       self.  You  will  need  to adjust your signal mask, sigaction, umask, and environmental vari‐
       ables. Look at the auditd man page to see which signals auditd used. Plugins are expected  to
       handle  SIGTERM  and  SIGHUP.  You will also inherit the resource limits of auditd. Note that
       some of these resource limits, such as maximum number of open descriptors, are controlled  by
       systemd.  You  also  inherit auditd's nice value. You might want to adjust that to be sure to
       keep up with incoming audit events.

       Auditd will send events to the plugin on it's stdin. The plugin has to keep  this  descriptor
       empty  so  that  events  don't  back  up. If you do significant processing of each event, you
       should add an internal queue to your design in order to keep events flowing. The auparse_feed
       function is the preferred way to examine whole events if you need to analyze the contents  of
       the events.


FILES
       /etc/auditd/auditd.conf /etc/audit/plugins.d

SEE ALSO
       auditd.conf(5), auditd(8), execve(2), auparse_feed(3).

AUTHOR
       Steve Grubb

Red Hat                                       Apr 2023                             AUDITD-PLUGINS(5)