ntp: Audit NTP parameters adjustment

Emit an audit record every time selected NTP parameters are modified
from userspace (via adjtimex(2) or clock_adjtime(2)). These parameters
may be used to indirectly change system clock, and thus their
modifications should be audited.

Such events will now generate records of type AUDIT_TIME_ADJNTPVAL
containing the following fields:
  - 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
  - old -- the old value
  - new -- the new value

Example records:

type=TIME_ADJNTPVAL msg=audit(1530616044.507:7): op=status old=64 new=8256
type=TIME_ADJNTPVAL msg=audit(1530616044.511:11): op=freq old=0 new=49180377088000

The records of this type will be associated with the corresponding
syscall records.

An overview of parameter changes that can be done via do_adjtimex()
(based on information from Miroslav Lichvar) and whether they are
audited:
  __timekeeping_set_tai_offset() -- sets the offset from the
                                    International Atomic Time
                                    (AUDITED)
  NTP variables:
    time_offset -- 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) (AUDITED)
    time_freq -- can speed up or slow down by up to about 0.05%
                 (AUDITED)
    time_status -- can insert/delete leap seconds and it also enables/
                   disables synchronization of the hardware real-time
                   clock (AUDITED)
    time_maxerror, time_esterror -- change error estimates used to
                                    inform userspace applications
                                    (NOT AUDITED)
    time_constant -- controls the speed of the clock adjustments that
                     are made when time_offset is set (NOT AUDITED)
    time_adjust -- can temporarily speed up or slow down the clock by up
                   to 0.05% (AUDITED)
    tick_usec -- a more extreme version of time_freq; can speed up or
                 slow down the clock by up to 10% (AUDITED)

Signed-off-by: Ondrej Mosnacek <omosnace@redhat.com>
Reviewed-by: Richard Guy Briggs <rgb@redhat.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Paul Moore <paul@paul-moore.com>

1 files changed, 6 insertions, 1 deletions

diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 3d24be4cd60793..f366f2fdf1b052 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -2307,6 +2307,7 @@ static int timekeeping_validate_timex(const struct __kernel_timex *txc)
 int do_adjtimex(struct __kernel_timex *txc)
 {
 	struct timekeeper *tk = &tk_core.timekeeper;
+	struct audit_ntp_data ad;
 	unsigned long flags;
 	struct timespec64 ts;
 	s32 orig_tai, tai;
@@ -2330,13 +2331,15 @@ int do_adjtimex(struct __kernel_timex *txc)
 		audit_tk_injoffset(delta);
 	}
 
+	audit_ntp_init(&ad);
+
 	ktime_get_real_ts64(&ts);
 
 	raw_spin_lock_irqsave(&timekeeper_lock, flags);
 	write_seqcount_begin(&tk_core.seq);
 
 	orig_tai = tai = tk->tai_offset;
-	ret = __do_adjtimex(txc, &ts, &tai);
+	ret = __do_adjtimex(txc, &ts, &tai, &ad);
 
 	if (tai != orig_tai) {
 		__timekeeping_set_tai_offset(tk, tai);
@@ -2347,6 +2350,8 @@ int do_adjtimex(struct __kernel_timex *txc)
 	write_seqcount_end(&tk_core.seq);
 	raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
 
+	audit_ntp_log(&ad);
+
 	/* Update the multiplier immediately if frequency was set directly */
 	if (txc->modes & (ADJ_FREQUENCY | ADJ_TICK))
 		timekeeping_advance(TK_ADV_FREQ);