Should audit_seccomp check audit_enabled?

[Andy Lutomirski]

On Fri, Oct 23, 2015 at 2:22 PM, Kees Cook <keescook at chromium.org> wrote:
> On Fri, Oct 23, 2015 at 2:07 PM, Andy Lutomirski <luto at amacapital.net> wrote:
>> On Oct 23, 2015 10:01 AM, "Kees Cook" <keescook at chromium.org> wrote:
>>>
>>> On Fri, Oct 23, 2015 at 9:19 AM, Andy Lutomirski <luto at amacapital.net> wrote:
>>> > I would argue that, if auditing is off, audit_seccomp shouldn't do
>>> > anything.  After all, unlike e.g. selinux, seccomp is not a systemwide
>>> > policy, and seccomp signals might be ordinary behavior that's internal
>>> > to the seccomp-using application.  IOW, for people with audit compiled
>>> > in and subscribed by journald but switched off, I think that the
>>> > records shouldn't be emitted.
>>> >
>>> > If you agree, I can send the two-line patch.
>>>
>>> I think signr==0 states (which I would identify as "intended
>>> behavior") don't need to be reported under any situation, but audit
>>> folks wanted to keep it around.
>>
>> Even if there is a nonzero signr, it could just be a program opting to
>> trap and emulate one of its own syscalls.
>
> At present, that is a rare situation. Programs tend to be ptrace
> managed externally. Is there anything catching SIGSYS itself?
>

I wrote one once.  I also wrote a whole set of patches for libseccomp
to make it easier that never went anywhere -- I should dust those off
and package them into their own library.

--Andy