reactive audit proposal

[Richard Guy Briggs]

On 2020-05-14 10:47, Steve Grubb wrote:
> Hello,
> 
> Answering both emails at once.
> 
> On Thursday, May 14, 2020 9:32:21 AM EDT Richard Guy Briggs wrote:
> > On 2020-05-14 18:55, Burn Alting wrote:
> > > I also endorse such a change.
> > > There is a significant gap in recoding removable media activity (see
> > > https://bugzilla.redhat.com/show_bug.cgi?id=967241) and the on_mount
> > > could go a reasonable  way to address this, including making use of the
> > > NETLUNK_KOBJECT_UEVENTnetlink group or  /sys/block polling to assist with
> > > device discovery.
> 
> libudev has a function that looks up device from a path. I was planning to use that.
> 
> > > Secondly, being able to react to a login/logout event also opens up
> > > interesting opportunity for targetedevent generation.
> > > That said, I believe that Juro Hlista did some work on this back around
> > > 2010. He did this via a plugin. His solutionwas a little more generic.
> > > Should we be looking at that as a solution as well?
> 
> I really don't know that code. It was done as a summer research project for
> a thesis. I do not know if it is production ready, supportable, or
> sustainable. While it may be more general, I remember the code base being
> large. Large means complicated. I'd rather narrow the scope and have a small
> amount of code that serves a single purpose.
> 
> > > One element I do
> > > remember from hiswork, was that there was a potential gap in the time to
> > > react to a trigger firing and the result was that one was notguaranteed
> > > to implement the new rules immediately. I assume to treat this gap, the
> > > rules could be preloaded and the 'trigger' action could just move the
> > > 'dormant' rules, already in core, to the 'active' list.
> 
> I was going to make them memory resident so that searching them is fast.
> Watching for mount changes will probably be faster that the general system
> because it does not depend on a mount syscall rule to trickle down and then
> react. 
> 
> In the user case, we would watch for the login event. It should be
> able to react before the whole pam cycle finishes. Although we would want to
> monitor the progress of pam so that we don't place a rule when the session
> never starts due to pam_time voting no. And we'll have to handle a login and
> cron jobs differently.
>  
> > I was going to say, this one feels like there are a set of rules that
> > should just be present from the get-go and not dynamic.  If we already
> > know what we are looking for (monitor a specific user, or monitor a
> > specific device) then just add those rules to the permenent set.
> 
> OK, lets give that a try
> 
> # auditctl -a always,exit -F dir=/run/media/sgrubb/sandisk/ -F perm=rx -F key=usb-drive
> Error sending add rule data request (No such file or directory)
> 
> We can't. Also, every single rule we add slows down the system.

True on both counts.  However, that is also true of the device
monitoring list to a lesser degree...

GHAK12 ( https://github.com/linux-audit/audit-kernel/issues/12 ) may
help with this and the idea has been discussed previously to find a way
to overcome this current limitation of kaudit.

> -Steve
> 
> > This makes it easier to lock things down too.
> > 
> > > Burn
> > > 
> > > On Wed, 2020-05-13 at 14:03 -0400, Steve Grubb wrote:
> > > > On Wednesday, May 13, 2020 1:17:02 PM EDT Joe Wulf wrote:
> > > > > What you propose is a sound enhancement.I have no preference for the
> > > > > choice between incorporate this in the auditdaemon versus a
> > > > > plugin.What would be the effort to switch from one to theother if
> > > > > later on you should find the first choice wasn't as optimal?
> > > > 
> > > > Well, the main idea for a plugin is not to stop processing events. Busy
> > > > systems need to keep focused on unloading the kernel backlog.
> > > > 
> > > > > I wonder about the case where a system is booted with new media
> > > > > alreadyattached.> > 
> > > > During initialization, it runs through the mount table just as if the
> > > > mount table was changed. So, it has the opportunity to apply rules
> > > > during init. I'm borrowing code from fapolicyd which has this nicely
> > > > solved. (It's one of my other projects.) -Steve
> > 
> > - RGB

- RGB

--
Richard Guy Briggs <rgb at redhat.com>
Sr. S/W Engineer, Kernel Security, Base Operating Systems
Remote, Ottawa, Red Hat Canada
IRC: rgb, SunRaycer
Voice: +1.647.777.2635, Internal: (81) 32635