[PATCH] bpf: emit audit messages upon successful prog load and unload

[Paul Moore]

On Thu, Nov 21, 2019 at 7:25 PM Daniel Borkmann <daniel at iogearbox.net> wrote:
> On 11/22/19 12:41 AM, Paul Moore wrote:
> > On Wed, Nov 20, 2019 at 4:49 PM Alexei Starovoitov
> > <alexei.starovoitov at gmail.com> wrote:
> >> On Wed, Nov 20, 2019 at 1:46 PM Daniel Borkmann <daniel at iogearbox.net> wrote:
> >>> On 11/20/19 10:38 PM, Jiri Olsa wrote:
> >>>> From: Daniel Borkmann <daniel at iogearbox.net>
> >>>>
> >>>> Allow for audit messages to be emitted upon BPF program load and
> >>>> unload for having a timeline of events. The load itself is in
> >>>> syscall context, so additional info about the process initiating
> >>>> the BPF prog creation can be logged and later directly correlated
> >>>> to the unload event.
> >>>>
> >>>> The only info really needed from BPF side is the globally unique
> >>>> prog ID where then audit user space tooling can query / dump all
> >>>> info needed about the specific BPF program right upon load event
> >>>> and enrich the record, thus these changes needed here can be kept
> >>>> small and non-intrusive to the core.
> >>>>
> >>>> Raw example output:
> >>>>
> >>>>     # auditctl -D
> >>>>     # auditctl -a always,exit -F arch=x86_64 -S bpf
> >>>>     # ausearch --start recent -m 1334
> >>>>     [...]
> >>>>     ----
> >>>>     time->Wed Nov 20 12:45:51 2019
> >>>>     type=PROCTITLE msg=audit(1574271951.590:8974): proctitle="./test_verifier"
> >>>>     type=SYSCALL msg=audit(1574271951.590:8974): arch=c000003e syscall=321 success=yes exit=14 a0=5 a1=7ffe2d923e80 a2=78 a3=0 items=0 ppid=742 pid=949 auid=0 uid=0 gid=0 euid=0 suid=0 fsuid=0 egid=0 sgid=0 fsgid=0 tty=pts0 ses=2 comm="test_verifier" exe="/root/bpf-next/tools/testing/selftests/bpf/test_verifier" subj=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 key=(null)
> >>>>     type=UNKNOWN[1334] msg=audit(1574271951.590:8974): auid=0 uid=0 gid=0 ses=2 subj=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 pid=949 comm="test_verifier" exe="/root/bpf-next/tools/testing/selftests/bpf/test_verifier" prog-id=3260 event=LOAD
> >>>>     ----
> >>>>     time->Wed Nov 20 12:45:51 2019
> >>>> type=UNKNOWN[1334] msg=audit(1574271951.590:8975): prog-id=3260 event=UNLOAD
> >>>>     ----
> >>>>     [...]
> >>>>
> >>>> Signed-off-by: Daniel Borkmann <daniel at iogearbox.net>
> >>>> Signed-off-by: Jiri Olsa <jolsa at kernel.org>
> >>>
> >>> LGTM, thanks for the rebase!
> >>
> >> Applied to bpf-next. Thanks!
> >
> > [NOTE: added linux-audit to the To/CC line]
> >
> > Wait a minute, why was the linux-audit list not CC'd on this?  Why are
> > you merging a patch into -next that adds to the uapi definition *and*
> > creates a new audit record while we are at -rc8?
> >
> > Aside from that I'm concerned that you are relying on audit userspace
> > changes that might not be okay; I see the PR below, but I don't see
> > any comment on it from Steve (it is his audit userspace).  I also
> > don't see a corresponding test added to the audit-testsuite, which is
> > a common requirement for new audit functionality (link below).  I'm
> > also fairly certain we don't want this new BPF record to look like how
> > you've coded it up in bpf_audit_prog(); duplicating the fields with
> > audit_log_task() is wrong, you've either already got them via an
> > associated record (which you get from passing non-NULL as the first
> > parameter to audit_log_start()), or you don't because there is no
> > associated syscall/task (which you get from passing NULL as the first
> > parameter).  Please revert, un-merge, etc. this patch from bpf-next;
> > it should not go into Linus' tree as written.
>
> Fair enough, up to you guys. My impression was that this is mainly coming
> from RHEL use case [0] and given that the original patch was back in Oct
> 2018 [1] that you've sorted it out by now RH internally and agreed to proceed
> with this patch for BPF given the rebase + resend ... seems not then. :(

For the record, I am not currently employed by RH and thus not part of
any RH internal discussions.  Although, even when I was, I would still
bristle at the idea of audit patches going in without CC'ing the audit
list and getting an ACK from the audit folks.  Internal discussions
within a company are fine, but the final discussion and debate should
happen on the public list.

> Given the change is mostly trivial, are there any major objections for Jiri
> to follow-up? Otherwise worst case probably easier to revert in net-next.

See my previous response for more info.  However, for starters the use
of audit_log_task() looks like the wrong thing to do here.  I also
want to see a test for our test suite so we can catch when someone
invariably breaks this in future and fix it.

>    [0] slide 11, https://linuxplumbersconf.org/event/4/contributions/460/attachments/244/426/xdp-distro-view.pdf
>    [1] https://lore.kernel.org/netdev/20181004135038.2876-1-daniel@iogearbox.net/

-- 
paul moore
www.paul-moore.com