Re: [PATCH ghak25 v4 3/3] audit: add subj creds to NETFILTER_CFG record to cover async unregister

From: Paul Moore <paul@paul-moore.com>
To: Richard Guy Briggs <rgb@redhat.com>
Cc: fw@strlen.de, LKML <linux-kernel@vger.kernel.org>,
	Linux-Audit Mailing List <linux-audit@redhat.com>,
	netfilter-devel@vger.kernel.org, ebiederm@xmission.com,
	twoerner@redhat.com, Eric Paris <eparis@parisplace.org>,
	tgraf@infradead.org
Subject: Re: [PATCH ghak25 v4 3/3] audit: add subj creds to NETFILTER_CFG record to cover async unregister
Date: Sun, 17 May 2020 17:50:17 -0400	[thread overview]
Message-ID: <CAHC9VhQVRyJ7GRHrujW5Ri-pvBRBgFM2Y8+OYQxca1bUyv2eyg@mail.gmail.com> (raw)
In-Reply-To: <20200517141515.qqx3jx5ulb2546tx@madcap2.tricolour.ca>

On Sun, May 17, 2020 at 10:15 AM Richard Guy Briggs <rgb@redhat.com> wrote:
> On 2020-04-28 18:25, Paul Moore wrote:
> > On Wed, Apr 22, 2020 at 5:40 PM Richard Guy Briggs <rgb@redhat.com> wrote:
> > > Some table unregister actions seem to be initiated by the kernel to
> > > garbage collect unused tables that are not initiated by any userspace
> > > actions.  It was found to be necessary to add the subject credentials to
> > > cover this case to reveal the source of these actions.  A sample record:
> > >
> > >   type=NETFILTER_CFG msg=audit(2020-03-11 21:25:21.491:269) : table=nat family=bridge entries=0 op=unregister pid=153 uid=root auid=unset tty=(none) ses=unset subj=system_u:system_r:kernel_t:s0 comm=kworker/u4:2 exe=(null)
> >
> > [I'm going to comment up here instead of in the code because it is a
> > bit easier for everyone to see what the actual impact might be on the
> > records.]
> >
> > Steve wants subject info in this case, okay, but let's try to trim out
> > some of the fields which simply don't make sense in this record; I'm
> > thinking of fields that are unset/empty in the kernel case and are
> > duplicates of other records in the userspace/syscall case.  I think
> > that means we can drop "tty", "ses", "comm", and "exe" ... yes?
> >
> > While "auid" is a potential target for removal based on the
> > dup-or-unset criteria, I think it falls under Steve's request for
> > subject info here, even if it is garbage in this case.
>
> Can you explain why auid falls under this criteria but ses does not if
> both are unset?

"While "auid" is a potential target for removal based on the
dup-or-unset criteria, I think it falls under Steve's request for
subject info here, even if it is garbage in this case."

It's a concession to Steve.  As I mentioned previously, I think the
subject info is bogus in this case; either it is valid and we get it
from the SYSCALL record or it simply isn't present in any meaningful
way.

-- 
paul moore
www.paul-moore.com

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