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Re: Relying on syscall record for information and useless key/value duplication



Eric Paris wrote:
> So I realized today that we have overlapping information in records and
> I don't like it.  

You realized this just today?? :-)

> A great example would be the MAC_STATUS record and how
> you can get duplicate info.  Looking at that following output.
> 
> type=MAC_STATUS msg=audit(1326314451.473:1018): enforcing=0 old_enforcing=1 auid=4166 ses=2
> type=SYSCALL msg=audit(1326314451.473:1018): arch=c000003e syscall=1 success=yes exit=1 a0=3 a1=7fffc73e1200 a2=1 a3=0 items=0 ppid=3110 pid=21435 auid=4166 uid=0 gid=0 euid=0 suid=0 fsuid=0 egid=0 sgid=0 fsgid=0 tty=pts3 ses=2 comm="setenforce" exe="/usr/sbin/setenforce" subj=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 key=(null)
> 
> What you see is that the MAC_STATUS record tells us more than about the
> mac status.  It also includes the auid and ses.  Why only that info?
> Why not other info like the SELinux context?  What really bothers me is
> that We already get that info (and a lot more info) in the SYSCALL
> record.  I believe this is bogus.  What I'd like to do is to create a
> new record called the 'TASK_INFO' record that will contain:
> 
> ppid pid auid uid gid euid suid fsuid egid sgid fsgid tty ses comm exe
> subj
> 
> And have this record be 'automagically' emitted any time any record is
> emitted.  

Any time any record is emitted?   This doesn't include auxiliary records,
does it?  So at most, one TASK_INFO record associated with any audit
event, regardless of how many records that event generates?  My concern
is for cases like when we flush the IPsec SPD entries.  That's one SYSCALL
that can turn into 10's (or 100's) of MAC_IPSEC_EVENT records.  Would
I get just one TASK_INFO or one per MAC_IPSEC_EVENT record?  We only need
one since all of these records have the same event number anyway so they'd
be identical.

> Thus we don't have information duplication and even if you
> have rules to exclude the SYSCALL record you still get all the info you
> ever needed for the MAC_STATUS record you wanted.
> 
> Does this make sense?  

I'm all for cleaning things up but I have a couple of questions.

Are you also planning to change the basic AVC message so it would require
a TASK_INFO message?

What about audit records that aren't associated with syscalls, such
as all the messages that originate in user space?  Just looking at one
of my systems, I see things like CRYPTO_KEY_USER, DAEMON_START, all
the AUTH-related records, etc.  They have some of the same stuff.

> Is there a reason not to do this?  

Breaking legacy programs?

Will this break programs that are only looking at a specific record type?
For example, the MAC_IPSEC_EVENT record also has an auid, ses, and subj.
The information in that record could be all anyone ever wanted for monitoring
the SPD activity, even though there is also a SYSCALL record with even more
information.  If they never looked at the SYSCALL record before, now they'll
have to look at the TASK_INFO record?

Most importantly (to me), will it break the audit-test suite?  We try to be fuzzy
in the way we look for information but we do have tests that look for
a SYSCALL record looking for subj, auid, success, name and obj fields, for
example.  Our test suite is smart enough to collect all the auxillary records
(CWD, PATH, etc) so if the TASK_INFO is associated with the syscall and the
field names are the same, things might just work.  I'd want to be sure of that.

> It makes the
> code smaller, faster, easier to maintainer, and MUCH easier to prove
> correct and complete.  It logically separates the info that is from the
> task doing the action from the records which are supposed to report on
> individual actions.
> 
> Shouldn't MAC_STATUS be about the mac status?  Shouldn't config change
> records be about the config that changed?  Shouldn't the xfrm records be
> about XFRM?  Obviously attributing these actions to a given task is
> important, but it isn't being put where it belongs.

Would have loved to see this about 6 years ago. :-)

-- ljk
> 
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