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.
Choices are builtin and always. Builtin should always be
given for plugins that are internal to the audit event
dispatcher. These are af_unix and syslog. The option
always should be given for most if not all plugins. The
default setting is always.
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.
