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

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Message-ID: <CAHC9VhRihMi_d-p+ieXyuVBcGMs80SkypVxF4gLE_s45GKP0dg@mail.gmail.com>
Date:   Thu, 21 Nov 2019 19:36:29 -0500
From:   Paul Moore <paul@...l-moore.com>
To:     Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc:     linux-audit@...hat.com, Jiri Olsa <jolsa@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Alexei Starovoitov <ast@...nel.org>,
        Network Development <netdev@...r.kernel.org>,
        bpf <bpf@...r.kernel.org>, Andrii Nakryiko <andriin@...com>,
        Yonghong Song <yhs@...com>, Martin KaFai Lau <kafai@...com>,
        Jakub Kicinski <jakub.kicinski@...ronome.com>,
        Steve Grubb <sgrubb@...hat.com>,
        David Miller <davem@...hat.com>,
        Eric Paris <eparis@...hat.com>, Jiri Benc <jbenc@...hat.com>
Subject: Re: [PATCH] bpf: emit audit messages upon successful prog load and unload

On Thu, Nov 21, 2019 at 7:23 PM Alexei Starovoitov
<alexei.starovoitov@...il.com> wrote:
> 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@...il.com> wrote:
> > > On Wed, Nov 20, 2019 at 1:46 PM Daniel Borkmann <daniel@...earbox.net> wrote:
> > > > On 11/20/19 10:38 PM, Jiri Olsa wrote:
> > > > > From: Daniel Borkmann <daniel@...earbox.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@...earbox.net>
> > > > > Signed-off-by: Jiri Olsa <jolsa@...nel.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.
>
> Sorry I didn't realize there was a disagreement.
>
> Dave, could you please revert it in net-next?
>
> > Audit userspace PR:
> > * https://github.com/linux-audit/audit-userspace/pull/104
>
> This PR does not use this new audit. It's doing everything via existing
> perf_event notification. My understanding of Jiri's email was that netlink
> style is preferred vs perf_event. Did I get it wrong?

Perhaps confusion on my part regarding the audit-userspace PR.  The
commit description mentioned the audit userspace (the daemon most
likely) fetching additional info about the BPF program and this was
the only outstanding audit-userspace PR that had any mention of BPF.

However, getting back to netlink vs perf_event, if you want to
generate an audit record, it should happen via the audit subsystem
(and go up to the audit daemon via netlink).

-- 
paul moore
www.paul-moore.com