src/timesync/timesyncd.c

   1 /* SPDX-License-Identifier: LGPL-2.1+ */
   2
   3 #include "sd-daemon.h"
   4 #include "sd-event.h"
   5
   6 #include "capability-util.h"
   7 #include "clock-util.h"
   8 #include "fd-util.h"
   9 #include "fs-util.h"
  10 #include "mkdir.h"
  11 #include "network-util.h"
  12 #include "process-util.h"
  13 #include "signal-util.h"
  14 #include "timesyncd-bus.h"
  15 #include "timesyncd-conf.h"
  16 #include "timesyncd-manager.h"
  17 #include "user-util.h"
  18
  19 #define STATE_DIR   "/var/lib/systemd/timesync"
  20 #define CLOCK_FILE  STATE_DIR "/clock"
  21
  22 static int load_clock_timestamp(uid_t uid, gid_t gid) {
  23         _cleanup_close_ int fd = -1;
  24         usec_t min = TIME_EPOCH * USEC_PER_SEC;
  25         usec_t ct;
  26         int r;
  27
  28         /* Let's try to make sure that the clock is always
  29          * monotonically increasing, by saving the clock whenever we
  30          * have a new NTP time, or when we shut down, and restoring it
  31          * when we start again. This is particularly helpful on
  32          * systems lacking a battery backed RTC. We also will adjust
  33          * the time to at least the build time of systemd. */
  34
  35         fd = open(CLOCK_FILE, O_RDWR|O_CLOEXEC, 0644);
  36         if (fd >= 0) {
  37                 struct stat st;
  38                 usec_t stamp;
  39
  40                 /* check if the recorded time is later than the compiled-in one */
  41                 r = fstat(fd, &st);
  42                 if (r >= 0) {
  43                         stamp = timespec_load(&st.st_mtim);
  44                         if (stamp > min)
  45                                 min = stamp;
  46                 }
  47
  48                 if (geteuid() == 0) {
  49                         /* Try to fix the access mode, so that we can still
  50                            touch the file after dropping priviliges */
  51                         r = fchmod_and_chown(fd, 0644, uid, gid);
  52                         if (r < 0)
  53                                 log_warning_errno(r, "Failed to chmod or chown %s, ignoring: %m", CLOCK_FILE);
  54                 }
  55
  56         } else {
  57                 r = mkdir_safe_label(STATE_DIR, 0755, uid, gid,
  58                                      MKDIR_FOLLOW_SYMLINK | MKDIR_WARN_MODE);
  59                 if (r < 0) {
  60                         log_debug_errno(r, "Failed to create state directory, ignoring: %m");
  61                         goto settime;
  62                 }
  63
  64                 /* create stamp file with the compiled-in date */
  65                 r = touch_file(CLOCK_FILE, false, min, uid, gid, 0644);
  66                 if (r < 0)
  67                         log_debug_errno(r, "Failed to create %s, ignoring: %m", CLOCK_FILE);
  68         }
  69
  70 settime:
  71         ct = now(CLOCK_REALTIME);
  72         if (ct < min) {
  73                 struct timespec ts;
  74                 char date[FORMAT_TIMESTAMP_MAX];
  75
  76                 log_info("System clock time unset or jumped backwards, restoring from recorded timestamp: %s",
  77                          format_timestamp(date, sizeof(date), min));
  78
  79                 if (clock_settime(CLOCK_REALTIME, timespec_store(&ts, min)) < 0)
  80                         log_error_errno(errno, "Failed to restore system clock, ignoring: %m");
  81         }
  82
  83         return 0;
  84 }
  85
  86 int main(int argc, char *argv[]) {
  87         _cleanup_(manager_freep) Manager *m = NULL;
  88         const char *user = "systemd-timesync";
  89         uid_t uid, uid_current;
  90         gid_t gid;
  91         int r;
  92
  93         log_set_target(LOG_TARGET_AUTO);
  94         log_set_facility(LOG_CRON);
  95         log_parse_environment();
  96         log_open();
  97
  98         umask(0022);
  99
 100         if (argc != 1) {
 101                 log_error("This program does not take arguments.");
 102                 r = -EINVAL;
 103                 goto finish;
 104         }
 105
 106         uid = uid_current = geteuid();
 107         gid = getegid();
 108
 109         if (uid_current == 0) {
 110                 r = get_user_creds(&user, &uid, &gid, NULL, NULL, 0);
 111                 if (r < 0) {
 112                         log_error_errno(r, "Cannot resolve user name %s: %m", user);
 113                         goto finish;
 114                 }
 115         }
 116
 117         r = load_clock_timestamp(uid, gid);
 118         if (r < 0)
 119                 goto finish;
 120
 121         /* Drop privileges, but only if we have been started as root. If we are not running as root we assume all
 122          * privileges are already dropped. */
 123         if (uid_current == 0) {
 124                 r = drop_privileges(uid, gid, (1ULL << CAP_SYS_TIME));
 125                 if (r < 0)
 126                         goto finish;
 127         }
 128
 129         assert_se(sigprocmask_many(SIG_BLOCK, NULL, SIGTERM, SIGINT, -1) >= 0);
 130
 131         r = manager_new(&m);
 132         if (r < 0) {
 133                 log_error_errno(r, "Failed to allocate manager: %m");
 134                 goto finish;
 135         }
 136
 137         r = manager_connect_bus(m);
 138         if (r < 0) {
 139                 log_error_errno(r, "Could not connect to bus: %m");
 140                 goto finish;
 141         }
 142
 143         if (clock_is_localtime(NULL) > 0) {
 144                 log_info("The system is configured to read the RTC time in the local time zone. "
 145                          "This mode cannot be fully supported. All system time to RTC updates are disabled.");
 146                 m->rtc_local_time = true;
 147         }
 148
 149         r = manager_parse_config_file(m);
 150         if (r < 0)
 151                 log_warning_errno(r, "Failed to parse configuration file: %m");
 152
 153         r = manager_parse_fallback_string(m, NTP_SERVERS);
 154         if (r < 0) {
 155                 log_error_errno(r, "Failed to parse fallback server strings: %m");
 156                 goto finish;
 157         }
 158
 159         log_debug("systemd-timesyncd running as pid " PID_FMT, getpid_cached());
 160         sd_notify(false,
 161                   "READY=1\n"
 162                   "STATUS=Daemon is running");
 163
 164         if (network_is_online()) {
 165                 r = manager_connect(m);
 166                 if (r < 0)
 167                         goto finish;
 168         }
 169
 170         r = sd_event_loop(m->event);
 171         if (r < 0) {
 172                 log_error_errno(r, "Failed to run event loop: %m");
 173                 goto finish;
 174         }
 175
 176         /* if we got an authoritative time, store it in the file system */
 177         if (m->sync) {
 178                 r = touch(CLOCK_FILE);
 179                 if (r < 0)
 180                         log_debug_errno(r, "Failed to touch %s, ignoring: %m", CLOCK_FILE);
 181         }
 182
 183         sd_event_get_exit_code(m->event, &r);
 184
 185 finish:
 186         sd_notify(false,
 187                   "STOPPING=1\n"
 188                   "STATUS=Shutting down...");
 189
 190         return r < 0 ? EXIT_FAILURE : EXIT_SUCCESS;
 191 }