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

[Jiri Olsa <jolsa@redhat.com>]

On Thu, Nov 21, 2019 at 06:41:31PM -0500, Paul Moore wrote:
> On Wed, Nov 20, 2019 at 4:49 PM Alexei Starovoitov
> <alexei.starovoitov@gmail.com> wrote:
> > On Wed, Nov 20, 2019 at 1:46 PM Daniel Borkmann <daniel@iogearbox.net> wrote:
> > > On 11/20/19 10:38 PM, Jiri Olsa wrote:
> > > > From: Daniel Borkmann <daniel@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@iogearbox.net>
> > > > Signed-off-by: Jiri Olsa <jolsa@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?

my bad sorry, I included only maintainers
there was previous RFC post:
  https://lore.kernel.org/netdev/20191120143810.8852-1-jolsa@kernel.org/

but I guess the patch followed up too fast

> 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.

the original audit approach for BPF notification was declined
in favor of perf-based approach:
  https://marc.info/?l=linux-netdev&m=153866106418036&w=2

We tried to add perf based notification support to auditd,
but it did not fit and was nack-ed by audit guys:
  https://www.redhat.com/archives/linux-audit/2019-August/msg00004.html

so we returned to the original approach

> 
> Audit userspace PR:
> * https://github.com/linux-audit/audit-userspace/pull/104

this is the perf-based notification approach, that got nacked

> 
> Audit test suite:
> * https://github.com/linux-audit/audit-testsuite

I'll check on these

thanks,
jirka