Remote logging with autitd

[Steve Grubb]

On Saturday, November 01, 2014 10:49:24 PM Wouter van Verre wrote:
> Hi all,
> 
> I am trying to set up logging using the audit framework, but I have some
> questions about how the system works and how the components fit together.

This presentation is a pretty good overview, see slide 5:
http://people.redhat.com/sgrubb/audit/audit_ids_2011.pdf


> My use case is as follows:
> * I would like to have one or more servers on my network capturing data,
> including TTY sessions.
> * I would then like to have these servers (the 'client servers') submit the
> data to another server on the network (the 'central server').
> * This central server would then write the incoming data to disk, and do
> some processing on the data as well.
> 
> My current idea on how to implement this is to:
> * Run auditd + audisp + audisp-remote on every client server.
> * Use pam_tty_audit.so on every client server for the TTY logging.
> * Run auditd on the central server to receive the data and write it to disk.
> * Either implement my processing tool such that it can be used instead of
> the dispatcher, or implement it as a plugin for audisp?

Sure. If necessary in realtime. That same presentation referenced about also 
gives an introduction to the auparse library.

 
> I'd love some feedback on whether this set up makes sense. In particular on
> whether receiving the data with auditd on the central server is the best
> way to go? And on which option is recommended for implementing the
> processing tool? I would think that a custom plugin for audisp would be
> best? If so, is there any documentation on how to go about implementing a
> plugin for audisp that I could read?
> 
> I have already experimented with this set up a bit, and have come to the
> conclusion that I am not sure how things work... I have implemented a
> single client running auditd + audisp + audisp-remote with logging of TTY
> session (using pam_tty_audit.so), and a central server running auditd (with
> auditd configured to listen to port 60).
> 
> This seems to work to an extent:
> * On the client server all the data is logged to /var/log/audit/audit.log
> and I can see it there.
> * On the client server I can run "aureport --tty" and I will see the TTY
> session data represented more easily. 
> * When I am on the central server I can run "aureport --tty" and see the TTY
> session data for session on the client server. My conclusion based on this
> is that the central server must be receiving and storing data properly?

Yes, that sounds right. I'd also mention that if you are doing central 
logging, you need to tell audispd or auditd that you want the node name 
prepended to the event so that at the aggregating server you can tell the 
difference.


> * However, when I look at /var/log/audit/audit.log on the central server I
> can only see audit data for that server.

My first guess is that you don't have the client adding node information. That 
makes it a lot clearer. You should able to search using --node to locate the 
records from the client.


> So my question is, where does the audit data from the client server get 
stored?

In the aggregating server's directory.

> * When I connect a very simple program to the auditd daemon (instead of the
> default dispatcher) it doesn't seem to receive any input at the moment, even
> though "aureport --tty" is showing that the daemon has been receiving data
> in the mean time...

The preferred way of adding analytical applications to make it am auditspd 
plugin. You could make it a dispatcher if you want, but the interface is a bit 
different. The audit tar ball should have an example program of both kinds.

-Steve