Re: [PATCH ghak10 v7 2/2] 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%

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(a)redhat.com&gt;

--- include/linux/audit.h | 54 ++++++++++++++++++++++++++++++++++++++ include/uapi/linux/audit.h | 1 + kernel/auditsc.c | 23 ++++++++++++++++ kernel/time/ntp.c | 22 +++++++++++++--- kernel/time/ntp_internal.h | 4 ++- kernel/time/timekeeping.c | 7 ++++- 6 files changed, 106 insertions(+), 5 deletions(-) diff --git a/include/linux/audit.h b/include/linux/audit.h index 2c62c0468888..1c372ad7ebe9 100644 --- a/include/linux/audit.h +++ b/include/linux/audit.h @@ -86,6 +86,26 @@ struct audit_field { u32 op; }; +#define AUDIT_NTP_OFFSET 0 +#define AUDIT_NTP_FREQ 1 +#define AUDIT_NTP_STATUS 2 +#define AUDIT_NTP_TAI 3 +#define AUDIT_NTP_TICK 4 +#define AUDIT_NTP_ADJUST 5 +#define AUDIT_NTP_NVALS 6 /* count */ + +#ifdef CONFIG_AUDITSYSCALL +struct audit_ntp_val { + s64 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 +386,7 @@ 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 +499,27 @@ 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, int id, s64 val) +{ + ad->vals[id].oldval = val; +} + +static inline void audit_ntp_set_new(struct audit_ntp_data *ad, int id, s64 val) +{ + ad->vals[id].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 +636,18 @@ 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, int id, s64 val) +{ } + +static inline void audit_ntp_set_new(struct audit_ntp_data *ad, int id, s64 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 diff --git a/include/uapi/linux/audit.h b/include/uapi/linux/audit.h index ab58d67baf4d..a1280af20336 100644 --- a/include/uapi/linux/audit.h +++ b/include/uapi/linux/audit.h @@ -115,6 +115,7 @@ #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_TIME_ADJNTPVAL 1333 /* NTP value adjustment */ #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 80dfe0cdc636..519ada7522ad 100644 --- a/kernel/auditsc.c +++ b/kernel/auditsc.c @@ -2518,6 +2518,29 @@ void __audit_tk_injoffset(struct timespec64 offset) "sec=%lli nsec=%li", (long long)offset.tv_sec, offset.tv_nsec); } +static void audit_log_ntp_val(const struct audit_ntp_data *ad, + const char *type, int id) +{ + const struct audit_ntp_val *val = &ad->vals[id]; + + if (val->newval == val->oldval) + return; + + audit_log(audit_context(), GFP_KERNEL, AUDIT_TIME_ADJNTPVAL, + "op=%s old=%lli new=%lli", type, + (long long)val->oldval, (long long)val->newval); +} + +void __audit_ntp_log(const struct audit_ntp_data *ad) +{ + audit_log_ntp_val(ad, "offset", AUDIT_NTP_OFFSET); + audit_log_ntp_val(ad, "freq", AUDIT_NTP_FREQ); + audit_log_ntp_val(ad, "status", AUDIT_NTP_STATUS); + audit_log_ntp_val(ad, "tai", AUDIT_NTP_TAI); + audit_log_ntp_val(ad, "tick", AUDIT_NTP_TICK); + audit_log_ntp_val(ad, "adjust", AUDIT_NTP_ADJUST); +} + static void audit_log_task(struct audit_buffer *ab) { kuid_t auid, uid; diff --git a/kernel/time/ntp.c b/kernel/time/ntp.c index 92a90014a925..ac5555e25733 100644 --- a/kernel/time/ntp.c +++ b/kernel/time/ntp.c @@ -17,6 +17,7 @@ #include <linux/mm.h> #include <linux/module.h> #include <linux/rtc.h> +#include <linux/audit.h> #include "ntp_internal.h" #include "timekeeping_internal.h" @@ -709,7 +710,7 @@ static inline void process_adjtimex_modes(const struct __kernel_timex *txc, * kernel time-keeping variables. used by xntpd. */ int __do_adjtimex(struct __kernel_timex *txc, const struct timespec64 *ts, - s32 *time_tai) + s32 *time_tai, struct audit_ntp_data *ad) { int result; @@ -720,14 +721,29 @@ int __do_adjtimex(struct __kernel_timex *txc, const struct timespec64 *ts, /* adjtime() is independent from ntp_adjtime() */ time_adjust = txc->offset; ntp_update_frequency(); + + audit_ntp_set_old(ad, AUDIT_NTP_ADJUST, save_adjust); + audit_ntp_set_new(ad, AUDIT_NTP_ADJUST, time_adjust); } txc->offset = save_adjust; } else { - /* If there are input parameters, then process them: */ - if (txc->modes) + if (txc->modes) { + audit_ntp_set_old(ad, AUDIT_NTP_OFFSET, time_offset); + audit_ntp_set_old(ad, AUDIT_NTP_FREQ, time_freq); + audit_ntp_set_old(ad, AUDIT_NTP_STATUS, time_status); + audit_ntp_set_old(ad, AUDIT_NTP_TAI, *time_tai); + audit_ntp_set_old(ad, AUDIT_NTP_TICK, tick_usec); + process_adjtimex_modes(txc, time_tai); + audit_ntp_set_new(ad, AUDIT_NTP_OFFSET, time_offset); + audit_ntp_set_new(ad, AUDIT_NTP_FREQ, time_freq); + audit_ntp_set_new(ad, AUDIT_NTP_STATUS, time_status); + audit_ntp_set_new(ad, AUDIT_NTP_TAI, *time_tai); + audit_ntp_set_new(ad, AUDIT_NTP_TICK, tick_usec); + } + txc->offset = shift_right(time_offset * NTP_INTERVAL_FREQ, NTP_SCALE_SHIFT); if (!(time_status & STA_NANO)) diff --git a/kernel/time/ntp_internal.h b/kernel/time/ntp_internal.h index 40e6122e634e..908ecaa65fc3 100644 --- a/kernel/time/ntp_internal.h +++ b/kernel/time/ntp_internal.h @@ -8,6 +8,8 @@ extern void ntp_clear(void); extern u64 ntp_tick_length(void); extern ktime_t ntp_get_next_leap(void); extern int second_overflow(time64_t secs); -extern int __do_adjtimex(struct __kernel_timex *txc, const struct timespec64 *ts, s32 *time_tai); +extern int __do_adjtimex(struct __kernel_timex *txc, + const struct timespec64 *ts, + s32 *time_tai, struct audit_ntp_data *ad); extern void __hardpps(const struct timespec64 *phase_ts, const struct timespec64 *raw_ts); #endif /* _LINUX_NTP_INTERNAL_H */ diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c index 3d24be4cd607..f366f2fdf1b0 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); -- 2.20.1