linux-kernel - Re: Should audit_seccomp check audit

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Date:	Fri, 23 Oct 2015 14:08:25 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	Paul Moore <paul@...l-moore.com>
Cc:	Steve Grubb <sgrubb@...hat.com>, Kees Cook <keescook@...omium.org>,
	Richard Guy Briggs <rgb@...hat.com>, linux-audit@...hat.com,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: Should audit_seccomp check audit_enabled?

On Fri, Oct 23, 2015 at 1:58 PM, Paul Moore <paul@...l-moore.com> wrote:
> On Fri, Oct 23, 2015 at 4:51 PM, Steve Grubb <sgrubb@...hat.com> wrote:
>> On Friday, October 23, 2015 03:38:05 PM Paul Moore wrote:
>>> On Fri, Oct 23, 2015 at 1:01 PM, Kees Cook <keescook@...omium.org> wrote:
>>> > On Fri, Oct 23, 2015 at 9:19 AM, Andy Lutomirski <luto@...capital.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.
>>>
>>> Wearing my libseccomp hat, I would like some logging when the seccomp
>>> filter triggers a result other than allow.  I don't care if this is
>>> via audit or printk(), I just want some notification.  If we go the
>>> printk route and people really don't want to see anything in their
>>> logs, I suppose we could always add a sysctl knob to turn off the
>>> message completely (we would still need to do whatever audit records
>>> are required, see below).
>>>
>>> Wearing my audit hat, I want to make sure we tick off all the right
>>> boxes for the various certifications that people care about.  Steve
>>> Grubb has commented on what he needs in the past, although I'm not
>>> sure it was on-list, so I'll ask him to repeat it here.
>>
>> I went back and reviewed my notes since this came up in the current Common
>> Criteria evaluation. What we decided to do is treat syscall failures which
>> failed due to seccomp the same as syscall failures caused by dropping
>> capabilities. Both are opt-in DAC policies. That means we don't care. Do
>> whatever you like. :-)
>
> Thanks Steve.
>
> Andy, is your objection that you don't want to see any seccomp
> messages, or just seccomp audit records when audit is disabled?
>

My objection is that people who have audit compiled in but disabled at
runtime shouldn't have the overhead or the log noise from these
messages.  If people want the messages, then I think they should turn
on audit (auditctl -e 1 or whatever).

--Andy
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