Re: [RFC PATCH ghak10 v4 0/2] audit: Log modifying adjtimex(2) calls

> 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%.