Running multiple audit service clients

[Steve Grubb]

On Wednesday, February 10, 2016 04:28:26 PM Max Timchenko wrote:
> I have a situation where there are two audit clients on the same machine:
> one of them is auditd, and another one is an IDS client that uses the audit
> subsystem directly. 

It should not be designed that way. For compliance purposes many people have 
to save the audit logs. I have given several speeches on how to do this so 
that everyone has a correct model to work from. The latest speech on audit+IDS 
is here:

http://people.redhat.com/sgrubb/audit/audit_ids_2011.pdf

The main idea is that auditd has a builtin facility for sharing events, 
auditspd. The IDS system can clip into it and get the event stream. If it 
wants events as they come "off the wire" they should set the format option to 
BINARY and they will get it exactly as it was handed to auditd. More typical 
is to use STRING format so that they can use auparse to dissect the event for 
processing.


> By looking at the source (
> http://lxr.free-electrons.com/source/kernel/audit.c?v=3.13#L787), I suspect
> that there might be no provision in the kernel for multiple audit subsystem
> userland daemons running in parallel (only one pid, only one netlink socket
> in the kernel). I could not find any documentation confirming or denying
> that.

There is not. Nor should there be. With the ease in which analysis programs 
can get the audit stream, they should not have to resort to exclusive access. 
For example, setroubleshooter plugin puts something in /etc/audisp/plugins.d/ 
so that it can see events in realtime. Its a good example of "doing it right".


> Has anyone tried that before? What would actually happen if two different
> audit clients tried to use the same interface to the audit subsystem in the
> kernel?

Last one wins.

-Steve