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From:   Steve Grubb <sgrubb@redhat.com>
To:     Richard Guy Briggs <rgb@redhat.com>
Cc:     Paul Moore <paul@paul-moore.com>,
        Linux-Audit Mailing List <linux-audit@redhat.com>,
        LKML <linux-kernel@vger.kernel.org>,
        netfilter-devel@vger.kernel.org, omosnace@redhat.com, fw@strlen.de,
        twoerner@redhat.com, Eric Paris <eparis@parisplace.org>,
        ebiederm@xmission.com, tgraf@infradead.org
Subject: Re: [PATCH ghak25 v4 3/3] audit: add subj creds to NETFILTER_CFG record to cover async unregister
Date:   Wed, 06 May 2020 17:26:25 -0400
Message-ID: <3250272.v6NOfJhyum@x2>
Organization: Red Hat
In-Reply-To: <20200429213247.6ewxqf66i2apgyuz@madcap2.tricolour.ca>
References: <cover.1587500467.git.rgb@redhat.com> <3348737.k9gCtgYObn@x2> <20200429213247.6ewxqf66i2apgyuz@madcap2.tricolour.ca>
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On Wednesday, April 29, 2020 5:32:47 PM EDT Richard Guy Briggs wrote:
> On 2020-04-29 14:47, Steve Grubb wrote:
> > On Wednesday, April 29, 2020 10:31:46 AM EDT Richard Guy Briggs 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>
> >=20
> > 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=3DNETFILTER_CFG msg=3Daudit(2020-03-11 21:25:21.491:269) :
> > > > > table=3Dnat
> > > > > family=3Dbridge entries=3D0 op=3Dunregister pid=3D153 uid=3Droot =
auid=3Dunset
> > > > > tty=3D(none) ses=3Dunset subj=3Dsystem_u:system_r:kernel_t:s0
> > > > > comm=3Dkworker/u4:2 exe=3D(null)>
> > > >=20
> > > > [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 t=
he
> > > > records.]
> > > >=20
> > > > 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?
> > >=20
> > > From the ghak28 discussion, this list and order was selected due to
> > > Steve's preference for the "kernel" record convention, so deviating
> > > from this will create yet a new field list.  I'll defer to Steve on
> > > this. It also has to do with the searchability of fields if they are
> > > missing.
> > >=20
> > > I do agree that some fields will be superfluous in the kernel case.
> > > The most important field would be "subj", but then "pid" and "comm", I
> > > would think.  Based on this contents of the "subj" field, I'd think
> > > that "uid", "auid", "tty", "ses" and "exe" are not needed.
> >=20
> > We can't be adding deleting fields based on how its triggered. If they
> > are unset, that is fine. The main issue is they have to behave the same.
>=20
> I don't think the intent was to have fields swing in and out depending
> on trigger.  The idea is to potentially permanently not include them in
> this record type only.  The justification is that where they aren't
> needed for the kernel trigger situation it made sense to delete them
> because if it is a user context event it will be accompanied by a
> syscall record that already has that information and there would be no
> sense in duplicating it.

We should not be adding syscall records to anything that does not result fr=
om=20
a syscall rule triggering the event. Its very wasteful. More wasteful than=
=20
just adding the necessary fields.

I also wished we had a coding specification that put this in writing so tha=
t=20
every event is not a committee decision. That anyone can look at the docume=
nt=20
and Do The Right Thing =E2=84=A2.

If I add a section to Writing-Good-Events outlining the expected ordering o=
f=20
fields, would that be enough that we do not have long discussions about eve=
nt=20
format? I'm thinking this would also help new people that want to contribut=
e.

=2DSteve