Re: exclude filter action ignored?
On Sunday, May 15, 2016 04:38:27 PM Richard Guy Briggs wrote:
Hi Steve,
Can you confirm that the exclude filter action parameter is ignored?
The exclude filter was supposed to do only 1 thing, delete events. It was
needed to create a pure CAPP system back in the lspp days. There are things
like selinux which sends events whether you wanted them or not. For a pure
CAPP system you just tell it the msgtype of selinux events and then they are
gone. People found other uses later like getting rid of cron job pam messages.
But its always been used to remove events rather than trigger them.
I can't find any evidence in the kernel or in userspace that the
action
value is actually honoured. In fact, looking at the manpage for
auditctl(8), the wording of the action contradicts the intuitive meaning
of that filter name. And as a matter of fact, I find discussion of it
here:
https://www.redhat.com/archives/linux-audit/2005-October/msg00020.html
In auditctl, setopt() calls audit_rule_setup() which calls lookup_filter()
and lookup_action(), then calls audit_rule_fieldpair_data() none of which
check when parsing the AUDIT_MSGTYPE field.
During rule addition, in kernel/auditfilter.c:audit_rule_change() and
callees AUDIT_FILTER_TYPE is never checked for either action but simply
copied.
When called from audit_log_start() in
kernel/auditfilter.c:audit_filter_type(), the state is never checked, so
either AUDIT_NEVER or AUDIT_ALWAYS actions gives the same result which
is to ignore that message type.
Which should delete the event from being emitted.
-Steve