Re: [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-auditi... > > Testing: Passed audit-testuite; functional tests TBD Reviewed-by: Richard Guy Briggs <rgb(a)redhat.com&gt; 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(a)redhat.com&gt; 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