noble (5) auditd-plugins.5.gz

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 configuration 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 default 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: inbound  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 configured. 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  auditd.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 metrics 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 itself. You
       will need to adjust your signal mask, sigaction, umask, and environmental variables. 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