From: Miroslav Lichvar <mlichvar@redhat.com>
To: Ondrej Mosnacek <omosnace@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>,
linux-audit@redhat.com, Paul Moore <paul@paul-moore.com>,
Richard Guy Briggs <rgb@redhat.com>,
Steve Grubb <sgrubb@redhat.com>,
John Stultz <john.stultz@linaro.org>,
Stephen Boyd <sboyd@kernel.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [RFC PATCH ghak10 v4 0/2] audit: Log modifying adjtimex(2) calls
Date: Tue, 21 Aug 2018 09:21:14 +0200 [thread overview]
Message-ID: <20180821072114.GC23069@localhost> (raw)
In-Reply-To: <alpine.DEB.2.21.1808201721350.1551@nanos.tec.linutronix.de>
> On Mon, 20 Aug 2018, Ondrej Mosnacek wrote:
> > @John or other timekeeping/NTP folks: We had a discussion on the audit
> > ML on which of the internal timekeeping/NTP variables we should actually
> > log changes for. We are only interested in variables that can (directly
> > or indirectly) cause noticeable changes to the system clock, but since we
> > have only limited understanding of the NTP code, we would like to ask
> > you for advice on which variables are security relevant.
I guess that mostly depends on whether you consider setting the clock
to run faster or slower than real time to be an important event for
the audit.
> > - NTP value adjustments:
> > - time_offset (probably important)
This can adjust the clock by up to 0.5 seconds per call and also speed
it up or slow down by up to about 0.05% (43 seconds per day).
> > - time_freq (maybe not important?)
This can speed up or slow down by up to about 0.05%.
> > - time_status (likely important, can cause leap second injection)
Yes, it can insert/delete leap seconds and it also enables/disables
synchronization of the hardware real-time clock.
> > - time_maxerror (maybe not important?)
> > - time_esterror (maybe not important?)
These two change the error estimates that are reported to applications
using ntp_gettime()/adjtimex(). If an application was periodically
checking that the clock is synchronized with some specified accuracy
and setting the maxerror to a larger value would cause the application
to abort, would it be an important event in the audit?
> > - time_constant (???)
This controls the speed of the clock adjustments that are made when
time_offset is set. Probably not important for the audit.
> > - time_adjust (sounds important)
This is similar to time_freq. It can temporarily speed up or slow down
the clock by up to 0.05%.
> > - tick_usec (???)
This is a more extreme version of time_freq. It can speed up or slow
down the clock by up to 10%.
--
Miroslav Lichvar
next prev parent reply other threads:[~2018-08-21 7:21 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-08-20 12:38 [RFC PATCH ghak10 v4 0/2] audit: Log modifying adjtimex(2) calls Ondrej Mosnacek
2018-08-20 12:38 ` [RFC PATCH ghak10 v4 1/2] audit: Add functions to log time adjustments Ondrej Mosnacek
2018-08-20 12:38 ` [RFC PATCH ghak10 v4 2/2] timekeeping/ntp: Audit clock/NTP params adjustments Ondrej Mosnacek
2018-08-20 15:21 ` [RFC PATCH ghak10 v4 0/2] audit: Log modifying adjtimex(2) calls Thomas Gleixner
2018-08-21 7:21 ` Miroslav Lichvar [this message]
2018-08-22 21:27 ` Paul Moore
2018-08-23 9:14 ` Ondrej Mosnacek
2018-08-23 11:50 ` Paul Moore
2018-08-24 14:56 ` Steve Grubb
2018-09-13 13:58 ` Ondrej Mosnacek
2018-09-13 14:07 ` Steve Grubb
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