linux-kernel - Re: [PATCH ghak10 v5 1/2] audit: Add functions to log time adjustments

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Message-ID: <20180914151643.gwvm5te4nvion5ex@madcap2.tricolour.ca>
Date:   Fri, 14 Sep 2018 11:16:43 -0400
From:   Richard Guy Briggs <rgb@...hat.com>
To:     Paul Moore <paul@...l-moore.com>
Cc:     omosnace@...hat.com, linux-audit@...hat.com, sgrubb@...hat.com,
        mlichvar@...hat.com, john.stultz@...aro.org, tglx@...utronix.de,
        sboyd@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH ghak10 v5 1/2] audit: Add functions to log time
 adjustments

On 2018-09-13 23:18, Paul Moore wrote:
> On Fri, Aug 24, 2018 at 8:00 AM Ondrej Mosnacek <omosnace@...hat.com> wrote:
> > This patch adds two auxiliary record types that will be used to annotate
> > the adjtimex SYSCALL records with the NTP/timekeeping values that have
> > been changed.
> >
> > Next, it adds two functions to the audit interface:
> >  - audit_tk_injoffset(), which will be called whenever a timekeeping
> >    offset is injected by a syscall from userspace,
> >  - audit_ntp_adjust(), which will be called whenever an NTP internal
> >    variable is changed by a syscall from userspace.
> >
> > Quick reference for the fields of the new records:
> >     AUDIT_TIME_INJOFFSET
> >         sec - the 'seconds' part of the offset
> >         nsec - the 'nanoseconds' part of the offset
> >     AUDIT_TIME_ADJNTPVAL
> >         op - which value was adjusted:
> >             offset - corresponding to the time_offset variable
> >             freq   - corresponding to the time_freq variable
> >             status - corresponding to the time_status variable
> >             adjust - corresponding to the time_adjust variable
> >             tick   - corresponding to the tick_usec variable
> >             tai    - corresponding to the timekeeping's TAI offset
> 
> I understand that reusing "op" is tempting, but the above aren't
> really operations, they are state variables which are being changed.
> Using the CONFIG_CHANGE record as a basis, I wonder if we are better
> off with something like the following:
> 
>  type=TIME_CHANGE <var>=<value_new> old=<value_old>
> 
> ... you might need to preface the variable names with something like
> "ntp_" or "offset_".  You'll notice I'm also suggesting we use a
> single record type here; is there any reason why two records types are
> required?

Why not do something like:

	 type=TIME_CHANGE var=<var> new=<value_new> old=<value_old>

So that we don't pollute the field namespace *and* create 8 variants on
the same record format?  This shouldn't be much of a concern with binary
record formats, but we're stuck with the current parsing scheme for now.

> >         old - the old value
> >         new - the new value
> >
> > Signed-off-by: Ondrej Mosnacek <omosnace@...hat.com>
> > ---
> >  include/linux/audit.h      | 21 +++++++++++++++++++++
> >  include/uapi/linux/audit.h |  2 ++
> >  kernel/auditsc.c           | 15 +++++++++++++++
> >  3 files changed, 38 insertions(+)
> 
> A reminder that we need tests for these new records and a RFE page on the wiki:
> 
> * https://github.com/linux-audit/audit-testsuite
> * https://github.com/linux-audit/audit-kernel/wiki
> 
> -- 
> paul moore
> www.paul-moore.com

- RGB

--
Richard Guy Briggs <rgb@...hat.com>
Sr. S/W Engineer, Kernel Security, Base Operating Systems
Remote, Ottawa, Red Hat Canada
IRC: rgb, SunRaycer
Voice: +1.647.777.2635, Internal: (81) 32635