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, 61 insertions, 0 deletions

diff --git a/include/linux/audit.h b/include/linux/audit.h
index 2c62c0468888..43a23e28ba23 100644
--- a/include/linux/audit.h
+++ b/include/linux/audit.h
@@ -86,6 +86,29 @@ struct audit_field {
 	u32				op;
 };
 
+enum audit_ntp_type {
+	AUDIT_NTP_OFFSET,
+	AUDIT_NTP_FREQ,
+	AUDIT_NTP_STATUS,
+	AUDIT_NTP_TAI,
+	AUDIT_NTP_TICK,
+	AUDIT_NTP_ADJUST,
+
+	AUDIT_NTP_NVALS /* count */
+};
+
+#ifdef CONFIG_AUDITSYSCALL
+struct audit_ntp_val {
+	long long oldval, newval;
+};
+
+struct audit_ntp_data {
+	struct audit_ntp_val vals[AUDIT_NTP_NVALS];
+};
+#else
+struct audit_ntp_data {};
+#endif
+
 extern int is_audit_feature_set(int which);
 
 extern int __init audit_register_class(int class, unsigned *list);
@@ -366,6 +389,7 @@ extern void __audit_mmap_fd(int fd, int flags);
 extern void __audit_log_kern_module(char *name);
 extern void __audit_fanotify(unsigned int response);
 extern void __audit_tk_injoffset(struct timespec64 offset);
+extern void __audit_ntp_log(const struct audit_ntp_data *ad);
 
 static inline void audit_ipc_obj(struct kern_ipc_perm *ipcp)
 {
@@ -478,6 +502,29 @@ static inline void audit_tk_injoffset(struct timespec64 offset)
 		__audit_tk_injoffset(offset);
 }
 
+static inline void audit_ntp_init(struct audit_ntp_data *ad)
+{
+	memset(ad, 0, sizeof(*ad));
+}
+
+static inline void audit_ntp_set_old(struct audit_ntp_data *ad,
+				     enum audit_ntp_type type, long long val)
+{
+	ad->vals[type].oldval = val;
+}
+
+static inline void audit_ntp_set_new(struct audit_ntp_data *ad,
+				     enum audit_ntp_type type, long long val)
+{
+	ad->vals[type].newval = val;
+}
+
+static inline void audit_ntp_log(const struct audit_ntp_data *ad)
+{
+	if (!audit_dummy_context())
+		__audit_ntp_log(ad);
+}
+
 extern int audit_n_rules;
 extern int audit_signals;
 #else /* CONFIG_AUDITSYSCALL */
@@ -594,6 +641,20 @@ static inline void audit_fanotify(unsigned int response)
 static inline void audit_tk_injoffset(struct timespec64 offset)
 { }
 
+static inline void audit_ntp_init(struct audit_ntp_data *ad)
+{ }
+
+static inline void audit_ntp_set_old(struct audit_ntp_data *ad,
+				     enum audit_ntp_type type, long long val)
+{ }
+
+static inline void audit_ntp_set_new(struct audit_ntp_data *ad,
+				     enum audit_ntp_type type, long long val)
+{ }
+
+static inline void audit_ntp_log(const struct audit_ntp_data *ad)
+{ }
+
 static inline void audit_ptrace(struct task_struct *t)
 { }
 #define audit_n_rules 0