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SubjectRe: [RFC PATCH ghak10 v6 0/2] audit: Log changes that can affect the system clock
On 2019-03-07 13:32, Ondrej Mosnacek wrote:
> This patchset implements auditing of (syscall-triggered) changes that
> can modify or indirectly affect the system clock. Some of these
> changes can already be detected by simply logging relevant syscalls,
> but this has some disadvantages:
> a) It is usually not possible to find out from the syscall records
> the amount by which the time was shifted.
> b) Syscalls like adjtimex(2) or clock_adjtime(2) can be used also
> for read-only operations, which might flood the audit log with
> false positives. (Note that these patches don't solve this
> problem yet due to the limitations of current record filtering
> capabilities.)
>
> The main motivation is to provide better reliability of timestamps
> on the system as mandated by the FPT_STM.1 security functional
> requirement from Common Criteria. This requirement apparently demands
> that it is possible to reconstruct from audit trail the old and new
> values of the time when it is adjusted (see [1]).
>
> The current version of the patchset logs the following changes:
> - direct setting of system time to a given value
> - direct injection of timekeeping offset
> - adjustment of timekeeping's TAI offset
> - NTP value adjustments:
> - time_offset
> - time_freq
> - time_status
> - time_adjust
> - tick_usec
>
> Changes to the following NTP values are not logged, as they are not
> important for security:
> - time_maxerror
> - time_esterror
> - time_constant
>
> Audit kernel GitHub issue: https://github.com/linux-audit/audit-kernel/issues/10
> Audit kernel RFE page: https://github.com/linux-audit/audit-kernel/wiki/RFE-More-detailed-auditing-of-changes-to-system-clock
>
> Testing: Passed audit-testuite; functional tests TBD

Reviewed-by: Richard Guy Briggs <rgb@redhat.com>

How do you plan to test this in the audit-testsuite?

> Changes in v6:
> - Reorganized the patches to group changes by record type, not
> kernel subsytem, as suggested in earlier discussions
> - Added checks to ignore no-change events (new value == old value)
> - Added TIME_INJOFFSET logging also to do_settimeofday64() to cover
> syscalls such as settimeofday(2), stime(2), clock_settime(2)
> - Created an RFE page on audit-kernel GitHub
> TODO:
> - tests for audit-testsuite
>
> v5: https://www.redhat.com/archives/linux-audit/2018-August/msg00039.html
> Changes in v5:
> - Dropped logging of some less important changes and update commit messages
> - No longer mark the patchset as RFC
>
> v4: https://www.redhat.com/archives/linux-audit/2018-August/msg00023.html
> Changes in v4:
> - Squashed first two patches into one
> - Renamed ADJNTPVAL's "type" field to "op" to align with audit record
> conventions
> - Minor commit message editing
> - Cc timekeeping/NTP people for feedback
>
> v3: https://www.redhat.com/archives/linux-audit/2018-July/msg00001.html
> Changes in v3:
> - Switched to separate records for each variable
> - Both old and new value is now reported for each change
> - Injecting offset is reported via a separate record (since this
> offset consists of two values and is added directly to the clock,
> i.e. it doesn't make sense to log old and new value)
> - Added example records produced by chronyd -q (see the commit message
> of the last patch)
>
> v2: https://www.redhat.com/archives/linux-audit/2018-June/msg00114.html
> Changes in v2:
> - The audit_adjtime() function has been modified to only log those
> fields that contain values that are actually used, resulting in more
> compact records.
> - The audit_adjtime() call has been moved to do_adjtimex() in
> timekeeping.c
> - Added an additional patch (for review) that simplifies the detection
> if the syscall is read-only.
>
> v1: https://www.redhat.com/archives/linux-audit/2018-June/msg00095.html
>
> [1] https://www.niap-ccevs.org/MMO/PP/pp_ca_v2.1.pdf -- section 5.1,
> table 4
>
> Ondrej Mosnacek (2):
> timekeeping: Audit clock adjustments
> ntp: Audit NTP parameters adjustment
>
> include/linux/audit.h | 29 +++++++++++++++++++++++++++++
> include/uapi/linux/audit.h | 2 ++
> kernel/auditsc.c | 15 +++++++++++++++
> kernel/time/ntp.c | 38 ++++++++++++++++++++++++++++++--------
> kernel/time/timekeeping.c | 6 ++++++
> 5 files changed, 82 insertions(+), 8 deletions(-)
>
> --
> 2.20.1
>

- RGB

--
Richard Guy Briggs <rgb@redhat.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

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