linux-kernel - Re: ntp audit spew.

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Date:   Mon, 23 Sep 2019 12:14:14 -0400
From:   Paul Moore <paul@...l-moore.com>
To:     Dave Jones <davej@...emonkey.org.uk>
Cc:     Linux Kernel <linux-kernel@...r.kernel.org>,
        Eric Paris <eparis@...hat.com>, linux-audit@...hat.com
Subject: Re: ntp audit spew.

On Mon, Sep 23, 2019 at 11:50 AM Dave Jones <davej@...emonkey.org.uk> wrote:
>
> I have some hosts that are constantly spewing audit messages like so:
>
> [46897.591182] audit: type=1333 audit(1569250288.663:220): op=offset old=2543677901372 new=2980866217213
> [46897.591184] audit: type=1333 audit(1569250288.663:221): op=freq old=-2443166611284 new=-2436281764244
> [48850.604005] audit: type=1333 audit(1569252241.675:222): op=offset old=1850302393317 new=3190241577926
> [48850.604008] audit: type=1333 audit(1569252241.675:223): op=freq old=-2436281764244 new=-2413071187316
> [49926.567270] audit: type=1333 audit(1569253317.638:224): op=offset old=2453141035832 new=2372389610455
> [49926.567273] audit: type=1333 audit(1569253317.638:225): op=freq old=-2413071187316 new=-2403561671476
>
> This gets emitted every time ntp makes an adjustment, which is apparently very frequent on some hosts.
>
>
> Audit isn't even enabled on these machines.
>
> # auditctl -l
> No rules

[NOTE: added linux-audit to the CC line]

There is an audit mailing list, please CC it when you have audit
concerns/questions/etc.

What happens when you run 'auditctl -a never,task'?  That *should*
silence those messages as the audit_ntp_log() function has the
requisite audit_dummy_context() check.  FWIW, this is the distro
default for many (most? all?) distros; for example, check
/etc/audit/audit.rules on a stock Fedora system.  A more selective
configuration could simply exclude the TIME_ADJNTPVAL record (type
1333) from the records that the kernel emits.

We could also add a audit_enabled check at the top of
audit_ntp_log()/__audit_ntp_log(), but I imagine some of that depends
on the various security requirements (they can be bizzare and I can't
say I'm up to date on all those - Steve Grubb should be able to
comment on that).

-- 
paul moore
www.paul-moore.com