/* SPDX-License-Identifier: LGPL-2.1-or-later */ #include #include #include "sd-daemon.h" #include "sd-event.h" #include "sd-messages.h" #include "capability-util.h" #include "clock-util.h" #include "daemon-util.h" #include "fd-util.h" #include "fs-util.h" #include "main-func.h" #include "mkdir-label.h" #include "network-util.h" #include "process-util.h" #include "signal-util.h" #include "timesyncd-bus.h" #include "timesyncd-conf.h" #include "timesyncd-manager.h" #include "user-util.h" static int advance_tstamp(int fd, const struct stat *st) { assert_se(fd >= 0); assert_se(st); /* So here's the problem: whenever we read the timestamp we'd like to ensure the next time we won't * restore the exact same time again, but one at least one step further (so that comparing mtimes of * the timestamp file is a reliable check that timesync did its thing). But file systems have * different timestamp accuracy: traditional fat has 2s granularity, and even ext2 and friends expose * different granularity depending on selected inode size during formatting! Hence, to ensure the * timestamp definitely is increased, here's what we'll do: we'll first try to increase the timestamp * by 1μs, write that and read it back. If it was updated, great. But if it was not, we'll instead * increase the timestamp by 10μs, and do the same, then 100μs, then 1ms, and so on, until it works, * or we reach 10s. If it still didn't work then, the fs is just broken and we give up. */ usec_t target = MAX3(now(CLOCK_REALTIME), TIME_EPOCH * USEC_PER_SEC, timespec_load(&st->st_mtim)); for (usec_t a = 1; a <= 10 * USEC_PER_SEC; a *= 10) { /* 1μs, 10μs, 100μs, 1ms, … 10s */ struct timespec ts[2]; struct stat new_st; /* Bump to the maximum of the old timestamp advanced by the specified unit, */ usec_t c = usec_add(target, a); timespec_store(&ts[0], c); ts[1] = ts[0]; if (futimens(fd, ts) < 0) { /* If this doesn't work at all, log, don't fail but give up */ log_warning_errno(errno, "Unable to update mtime of timestamp file, ignoring: %m"); return 0; } if (fstat(fd, &new_st) < 0) return log_error_errno(errno, "Failed to stat timestamp file: %m"); if (timespec_load(&new_st.st_mtim) > target) { log_debug("Successfully bumped timestamp file."); return 1; } log_debug("Tried to advance timestamp file by " USEC_FMT ", but this didn't work, file system timestamp granularity too coarse?", a); } log_debug("Gave up trying to advance timestamp file."); return 0; } static int load_clock_timestamp(uid_t uid, gid_t gid) { usec_t min = TIME_EPOCH * USEC_PER_SEC, ct; _cleanup_close_ int fd = -EBADF; int r; /* Let's try to make sure that the clock is always monotonically increasing, by saving the clock * whenever we have a new NTP time, or when we shut down, and restoring it when we start again. This * is particularly helpful on systems lacking a battery backed RTC. We also will adjust the time to * at least the build time of systemd. */ fd = open(CLOCK_FILE, O_RDWR|O_CLOEXEC, 0644); if (fd < 0) { if (errno != ENOENT) log_debug_errno(errno, "Unable to open timestamp file '" CLOCK_FILE "', ignoring: %m"); r = mkdir_safe_label(STATE_DIR, 0755, uid, gid, MKDIR_FOLLOW_SYMLINK | MKDIR_WARN_MODE); if (r < 0) log_debug_errno(r, "Failed to create state directory, ignoring: %m"); /* create stamp file with the compiled-in date */ r = touch_file(CLOCK_FILE, /* parents= */ false, min, uid, gid, 0644); if (r < 0) log_debug_errno(r, "Failed to create %s, ignoring: %m", CLOCK_FILE); } else { struct stat st; usec_t stamp; /* check if the recorded time is later than the compiled-in one */ if (fstat(fd, &st) < 0) return log_error_errno(errno, "Unable to stat timestamp file '" CLOCK_FILE "': %m"); stamp = timespec_load(&st.st_mtim); if (stamp > min) min = stamp; /* Try to fix the access mode, so that we can still touch the file after dropping * privileges */ r = fchmod_and_chown(fd, 0644, uid, gid); if (r < 0) log_full_errno(ERRNO_IS_PRIVILEGE(r) ? LOG_DEBUG : LOG_WARNING, r, "Failed to chmod or chown %s, ignoring: %m", CLOCK_FILE); (void) advance_tstamp(fd, &st); } ct = now(CLOCK_REALTIME); if (ct > min) return 0; /* Not that it matters much, but we actually restore the clock to n+1 here rather than n, simply * because we read n as time previously already and we want to progress here, i.e. not report the * same time again. */ if (clock_settime(CLOCK_REALTIME, TIMESPEC_STORE(min+1)) < 0) { log_warning_errno(errno, "Failed to restore system clock, ignoring: %m"); return 0; } log_struct(LOG_INFO, "MESSAGE_ID=" SD_MESSAGE_TIME_BUMP_STR, "REALTIME_USEC=" USEC_FMT, min+1, LOG_MESSAGE("System clock time unset or jumped backwards, restored from recorded timestamp: %s", FORMAT_TIMESTAMP(min+1))); return 0; } static int run(int argc, char *argv[]) { _cleanup_(manager_freep) Manager *m = NULL; _unused_ _cleanup_(notify_on_cleanup) const char *notify_message = NULL; const char *user = "systemd-timesync"; uid_t uid, uid_current; gid_t gid; int r; log_set_facility(LOG_CRON); log_setup(); umask(0022); if (argc != 1) return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "This program does not take arguments."); uid = uid_current = geteuid(); gid = getegid(); if (uid_current == 0) { r = get_user_creds(&user, &uid, &gid, NULL, NULL, 0); if (r < 0) return log_error_errno(r, "Cannot resolve user name %s: %m", user); } r = load_clock_timestamp(uid, gid); if (r < 0) return r; /* Drop privileges, but only if we have been started as root. If we are not running as root we assume all * privileges are already dropped. */ if (uid_current == 0) { r = drop_privileges(uid, gid, (1ULL << CAP_SYS_TIME)); if (r < 0) return log_error_errno(r, "Failed to drop privileges: %m"); } assert_se(sigprocmask_many(SIG_BLOCK, NULL, SIGTERM, SIGINT, SIGRTMIN+18, -1) >= 0); r = manager_new(&m); if (r < 0) return log_error_errno(r, "Failed to allocate manager: %m"); r = manager_connect_bus(m); if (r < 0) return log_error_errno(r, "Could not connect to bus: %m"); if (clock_is_localtime(NULL) > 0) { log_info("The system is configured to read the RTC time in the local time zone. " "This mode cannot be fully supported. All system time to RTC updates are disabled."); m->rtc_local_time = true; } r = manager_parse_config_file(m); if (r < 0) log_warning_errno(r, "Failed to parse configuration file: %m"); r = manager_parse_fallback_string(m, NTP_SERVERS); if (r < 0) return log_error_errno(r, "Failed to parse fallback server strings: %m"); log_debug("systemd-timesyncd running as pid " PID_FMT, getpid_cached()); notify_message = notify_start("READY=1\n" "STATUS=Daemon is running", NOTIFY_STOPPING); r = manager_setup_save_time_event(m); if (r < 0) return r; if (network_is_online()) { r = manager_connect(m); if (r < 0) return r; } r = sd_event_loop(m->event); if (r < 0) return log_error_errno(r, "Failed to run event loop: %m"); /* if we got an authoritative time, store it in the file system */ if (m->save_on_exit) { r = touch(CLOCK_FILE); if (r < 0) log_debug_errno(r, "Failed to touch " CLOCK_FILE ", ignoring: %m"); } return 0; } DEFINE_MAIN_FUNCTION(run);