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Subject[PATCH ghak10 v7 1/2] timekeeping: Audit clock adjustments
Date
Emit an audit record whenever the system clock is changed (i.e. shifted
by a non-zero offset) by a syscall from userspace. The syscalls than can
(at the time of writing) trigger such record are:
- settimeofday(2), stime(2), clock_settime(2) -- via
do_settimeofday64()
- adjtimex(2), clock_adjtime(2) -- via do_adjtimex()

The new records have type AUDIT_TIME_INJOFFSET and contain the following
fields:
- sec -- the 'seconds' part of the offset
- nsec -- the 'nanoseconds' part of the offset

Example record (time was shifted backwards by ~16.125 seconds):

type=TIME_INJOFFSET msg=audit(1530616049.652:13): sec=-16 nsec=124887145

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

Signed-off-by: Ondrej Mosnacek <omosnace@redhat.com>
---
include/linux/audit.h | 14 ++++++++++++++
include/uapi/linux/audit.h | 1 +
kernel/auditsc.c | 6 ++++++
kernel/time/timekeeping.c | 6 ++++++
4 files changed, 27 insertions(+)

diff --git a/include/linux/audit.h b/include/linux/audit.h
index 1e69d9fe16da..2c62c0468888 100644
--- a/include/linux/audit.h
+++ b/include/linux/audit.h
@@ -365,6 +365,7 @@ extern void __audit_log_capset(const struct cred *new, const struct cred *old);
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);

static inline void audit_ipc_obj(struct kern_ipc_perm *ipcp)
{
@@ -467,6 +468,16 @@ static inline void audit_fanotify(unsigned int response)
__audit_fanotify(response);
}

+static inline void audit_tk_injoffset(struct timespec64 offset)
+{
+ /* ignore no-op events */
+ if (offset.tv_sec == 0 && offset.tv_nsec == 0)
+ return;
+
+ if (!audit_dummy_context())
+ __audit_tk_injoffset(offset);
+}
+
extern int audit_n_rules;
extern int audit_signals;
#else /* CONFIG_AUDITSYSCALL */
@@ -580,6 +591,9 @@ static inline void audit_log_kern_module(char *name)
static inline void audit_fanotify(unsigned int response)
{ }

+static inline void audit_tk_injoffset(struct timespec64 offset)
+{ }
+
static inline void audit_ptrace(struct task_struct *t)
{ }
#define audit_n_rules 0
diff --git a/include/uapi/linux/audit.h b/include/uapi/linux/audit.h
index 3901c51c0b93..ab58d67baf4d 100644
--- a/include/uapi/linux/audit.h
+++ b/include/uapi/linux/audit.h
@@ -114,6 +114,7 @@
#define AUDIT_REPLACE 1329 /* Replace auditd if this packet unanswerd */
#define AUDIT_KERN_MODULE 1330 /* Kernel Module events */
#define AUDIT_FANOTIFY 1331 /* Fanotify access decision */
+#define AUDIT_TIME_INJOFFSET 1332 /* Timekeeping offset injected */

#define AUDIT_AVC 1400 /* SE Linux avc denial or grant */
#define AUDIT_SELINUX_ERR 1401 /* Internal SE Linux Errors */
diff --git a/kernel/auditsc.c b/kernel/auditsc.c
index 51a2ceb3a1ca..80dfe0cdc636 100644
--- a/kernel/auditsc.c
+++ b/kernel/auditsc.c
@@ -2512,6 +2512,12 @@ void __audit_fanotify(unsigned int response)
AUDIT_FANOTIFY, "resp=%u", response);
}

+void __audit_tk_injoffset(struct timespec64 offset)
+{
+ audit_log(audit_context(), GFP_KERNEL, AUDIT_TIME_INJOFFSET,
+ "sec=%lli nsec=%li", (long long)offset.tv_sec, offset.tv_nsec);
+}
+
static void audit_log_task(struct audit_buffer *ab)
{
kuid_t auid, uid;
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index f986e1918d12..3d24be4cd607 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -21,6 +21,7 @@
#include <linux/stop_machine.h>
#include <linux/pvclock_gtod.h>
#include <linux/compiler.h>
+#include <linux/audit.h>

#include "tick-internal.h"
#include "ntp_internal.h"
@@ -1250,6 +1251,9 @@ out:
/* signal hrtimers about time change */
clock_was_set();

+ if (!ret)
+ audit_tk_injoffset(ts_delta);
+
return ret;
}
EXPORT_SYMBOL(do_settimeofday64);
@@ -2322,6 +2326,8 @@ int do_adjtimex(struct __kernel_timex *txc)
ret = timekeeping_inject_offset(&delta);
if (ret)
return ret;
+
+ audit_tk_injoffset(delta);
}

ktime_get_real_ts64(&ts);
--
2.20.1
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