src/timesync/timesyncd.c

   1 /* SPDX-License-Identifier: LGPL-2.1+ */
   2
   3 #include <sys/stat.h>
   4 #include <sys/types.h>
   5
   6 #include "sd-daemon.h"
   7 #include "sd-event.h"
   8
   9 #include "capability-util.h"
  10 #include "clock-util.h"
  11 #include "daemon-util.h"
  12 #include "fd-util.h"
  13 #include "fs-util.h"
  14 #include "main-func.h"
  15 #include "mkdir.h"
  16 #include "network-util.h"
  17 #include "process-util.h"
  18 #include "signal-util.h"
  19 #include "timesyncd-bus.h"
  20 #include "timesyncd-conf.h"
  21 #include "timesyncd-manager.h"
  22 #include "user-util.h"
  23
  24 #define STATE_DIR   "/var/lib/systemd/timesync"
  25 #define CLOCK_FILE  STATE_DIR "/clock"
  26
  27 static int load_clock_timestamp(uid_t uid, gid_t gid) {
  28         _cleanup_close_ int fd = -1;
  29         usec_t min = TIME_EPOCH * USEC_PER_SEC;
  30         usec_t ct;
  31         int r;
  32
  33         /* Let's try to make sure that the clock is always
  34          * monotonically increasing, by saving the clock whenever we
  35          * have a new NTP time, or when we shut down, and restoring it
  36          * when we start again. This is particularly helpful on
  37          * systems lacking a battery backed RTC. We also will adjust
  38          * the time to at least the build time of systemd. */
  39
  40         fd = open(CLOCK_FILE, O_RDWR|O_CLOEXEC, 0644);
  41         if (fd >= 0) {
  42                 struct stat st;
  43                 usec_t stamp;
  44
  45                 /* check if the recorded time is later than the compiled-in one */
  46                 r = fstat(fd, &st);
  47                 if (r >= 0) {
  48                         stamp = timespec_load(&st.st_mtim);
  49                         if (stamp > min)
  50                                 min = stamp;
  51                 }
  52
  53                 if (geteuid() == 0) {
  54                         /* Try to fix the access mode, so that we can still
  55                            touch the file after dropping privileges */
  56                         r = fchmod_and_chown(fd, 0644, uid, gid);
  57                         if (r < 0)
  58                                 log_warning_errno(r, "Failed to chmod or chown %s, ignoring: %m", CLOCK_FILE);
  59                 }
  60
  61         } else {
  62                 r = mkdir_safe_label(STATE_DIR, 0755, uid, gid,
  63                                      MKDIR_FOLLOW_SYMLINK | MKDIR_WARN_MODE);
  64                 if (r < 0) {
  65                         log_debug_errno(r, "Failed to create state directory, ignoring: %m");
  66                         goto settime;
  67                 }
  68
  69                 /* create stamp file with the compiled-in date */
  70                 r = touch_file(CLOCK_FILE, false, min, uid, gid, 0644);
  71                 if (r < 0)
  72                         log_debug_errno(r, "Failed to create %s, ignoring: %m", CLOCK_FILE);
  73         }
  74
  75 settime:
  76         ct = now(CLOCK_REALTIME);
  77         if (ct < min) {
  78                 struct timespec ts;
  79                 char date[FORMAT_TIMESTAMP_MAX];
  80
  81                 log_info("System clock time unset or jumped backwards, restoring from recorded timestamp: %s",
  82                          format_timestamp(date, sizeof(date), min));
  83
  84                 if (clock_settime(CLOCK_REALTIME, timespec_store(&ts, min)) < 0)
  85                         log_error_errno(errno, "Failed to restore system clock, ignoring: %m");
  86         }
  87
  88         return 0;
  89 }
  90
  91 static int run(int argc, char *argv[]) {
  92         _cleanup_(manager_freep) Manager *m = NULL;
  93         _cleanup_(notify_on_cleanup) const char *notify_message = NULL;
  94         const char *user = "systemd-timesync";
  95         uid_t uid, uid_current;
  96         gid_t gid;
  97         int r;
  98
  99         log_set_facility(LOG_CRON);
 100         log_setup_service();
 101
 102         umask(0022);
 103
 104         if (argc != 1)
 105                 return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "This program does not take arguments.");
 106
 107         uid = uid_current = geteuid();
 108         gid = getegid();
 109
 110         if (uid_current == 0) {
 111                 r = get_user_creds(&user, &uid, &gid, NULL, NULL, 0);
 112                 if (r < 0)
 113                         return log_error_errno(r, "Cannot resolve user name %s: %m", user);
 114         }
 115
 116         r = load_clock_timestamp(uid, gid);
 117         if (r < 0)
 118                 return r;
 119
 120         /* Drop privileges, but only if we have been started as root. If we are not running as root we assume all
 121          * privileges are already dropped. */
 122         if (uid_current == 0) {
 123                 r = drop_privileges(uid, gid, (1ULL << CAP_SYS_TIME));
 124                 if (r < 0)
 125                         return log_error_errno(r, "Failed to drop privileges: %m");
 126         }
 127
 128         assert_se(sigprocmask_many(SIG_BLOCK, NULL, SIGTERM, SIGINT, -1) >= 0);
 129
 130         r = manager_new(&m);
 131         if (r < 0)
 132                 return log_error_errno(r, "Failed to allocate manager: %m");
 133
 134         r = manager_connect_bus(m);
 135         if (r < 0)
 136                 return log_error_errno(r, "Could not connect to bus: %m");
 137
 138         if (clock_is_localtime(NULL) > 0) {
 139                 log_info("The system is configured to read the RTC time in the local time zone. "
 140                          "This mode cannot be fully supported. All system time to RTC updates are disabled.");
 141                 m->rtc_local_time = true;
 142         }
 143
 144         r = manager_parse_config_file(m);
 145         if (r < 0)
 146                 log_warning_errno(r, "Failed to parse configuration file: %m");
 147
 148         r = manager_parse_fallback_string(m, NTP_SERVERS);
 149         if (r < 0)
 150                 return log_error_errno(r, "Failed to parse fallback server strings: %m");
 151
 152         log_debug("systemd-timesyncd running as pid " PID_FMT, getpid_cached());
 153
 154         notify_message = notify_start("READY=1\n"
 155                                       "STATUS=Daemon is running",
 156                                       NOTIFY_STOPPING);
 157
 158         if (network_is_online()) {
 159                 r = manager_connect(m);
 160                 if (r < 0)
 161                         return r;
 162         }
 163
 164         r = sd_event_loop(m->event);
 165         if (r < 0)
 166                 return log_error_errno(r, "Failed to run event loop: %m");
 167
 168         /* if we got an authoritative time, store it in the file system */
 169         if (m->sync) {
 170                 r = touch(CLOCK_FILE);
 171                 if (r < 0)
 172                         log_debug_errno(r, "Failed to touch %s, ignoring: %m", CLOCK_FILE);
 173         }
 174
 175         return 0;
 176 }
 177
 178 DEFINE_MAIN_FUNCTION(run);