Re: [RFC PATCH ghak10 v3 0/3] audit: Log modifying adjtimex(2) calls

[Steve Grubb <sgrubb@redhat.com>]

On Wednesday, July 18, 2018 3:59:24 PM EDT Paul Moore wrote:
> On Wed, Jul 18, 2018 at 3:36 PM Steve Grubb <sgrubb@redhat.com> wrote:
> > On Wednesday, July 18, 2018 2:36:11 PM EDT Paul Moore wrote:
> > > > Changes in v2:
> > > > - The audit_adjtime() function has been modified to only log those
> > > > fields that contain values that are actually used, resulting in more
> > > > compact records.
> > > > - The audit_adjtime() call has been moved to do_adjtimex() in
> > > > timekeeping.c
> > > > - Added an additional patch (for review) that simplifies the
> > > > detection
> > > > if the syscall is read-only.
> > > 
> > > Looking at these new records, and trying to guess a bit at the
> > > original intent of the feature request, I think we may be going a bit
> > > overboard with the information we are logging.  I'm thinking all we
> > > really need to capture in the audit log is the system time both before
> > > and after the change (for the sake of simplicity I suggest using a
> > > data format similar to the audit record timestamp).
> > > 
> > > While I created the GH issue for this, I believe the original request
> > > came from a Red Hat BZ that Steve created; Steve, what sort of
> > > certification requirements (if any?) are there for logging system time
> > > changes?
> > 
> > That we record any attempts to change the system time. The problem is
> > that
> > adjtimex passes a data structure that is opaque to user space. So, we
> > can't tell if someone is setting time, adjusting a tolerance, or simply
> > retrieving status.
> > 
> > With stime, we can clearly see the time that was sent into the kernel and
> > it unconditionally sets time. With settimeofday, it uses a data
> > structure that we cannot see, but whatever the contents are we are
> > definitely setting time. Same goes for clock_settime. Only in 1 case do
> > we actually see what the time is. So, that is not really needed. So, I
> > think what we need to know is did the syscall do anything that adjusted
> > the system's notion of time? And that's all.
> 
> So presumably my above suggestion of simply recording the system time
> both before and after the change would be sufficient, yes?

Well, I think that we need to make it obvious that a time setting has changed 
as in a y/n answer. Doing a comparison of the time to get a y/n answer is 
less obvious if you are doing a grep. Also, what time will the event have? I 
presume that the event will have the new time since we are on the exit 
filter. So, do we really need to collect that?

-Steve