src/timesync/timesyncd.c

   1 /* SPDX-License-Identifier: LGPL-2.1+ */
   2 /***
   3   Copyright 2014 Kay Sievers, Lennart Poettering
   4 ***/
   5
   6 #include "sd-daemon.h"
   7 #include "sd-event.h"
   8
   9 #include "capability-util.h"
  10 #include "clock-util.h"
  11 #include "fd-util.h"
  12 #include "fs-util.h"
  13 #include "mkdir.h"
  14 #include "network-util.h"
  15 #include "process-util.h"
  16 #include "signal-util.h"
  17 #include "timesyncd-bus.h"
  18 #include "timesyncd-conf.h"
  19 #include "timesyncd-manager.h"
  20 #include "user-util.h"
  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("/var/lib/systemd/timesync/clock", 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(fd, 0644);
  52                         if (r < 0)
  53                                 return log_error_errno(errno, "Failed to change file access mode: %m");
  54                         r = fchown(fd, uid, gid);
  55                         if (r < 0)
  56                                 return log_error_errno(errno, "Failed to change file owner: %m");
  57                 }
  58
  59         } else {
  60                 r = mkdir_safe_label("/var/lib/systemd/timesync", 0755, uid, gid,
  61                                      MKDIR_FOLLOW_SYMLINK | MKDIR_WARN_MODE);
  62                 if (r < 0)
  63                         return log_error_errno(r, "Failed to create state directory: %m");
  64
  65                 /* create stamp file with the compiled-in date */
  66                 (void) touch_file("/var/lib/systemd/timesync/clock", false, min, uid, gid, 0644);
  67         }
  68
  69         ct = now(CLOCK_REALTIME);
  70         if (ct < min) {
  71                 struct timespec ts;
  72                 char date[FORMAT_TIMESTAMP_MAX];
  73
  74                 log_info("System clock time unset or jumped backwards, restoring from recorded timestamp: %s",
  75                          format_timestamp(date, sizeof(date), min));
  76
  77                 if (clock_settime(CLOCK_REALTIME, timespec_store(&ts, min)) < 0)
  78                         log_error_errno(errno, "Failed to restore system clock: %m");
  79         }
  80
  81         return 0;
  82 }
  83
  84 int main(int argc, char *argv[]) {
  85         _cleanup_(manager_freep) Manager *m = NULL;
  86         const char *user = "systemd-timesync";
  87         uid_t uid, uid_current;
  88         gid_t gid;
  89         int r;
  90
  91         log_set_target(LOG_TARGET_AUTO);
  92         log_set_facility(LOG_CRON);
  93         log_parse_environment();
  94         log_open();
  95
  96         umask(0022);
  97
  98         if (argc != 1) {
  99                 log_error("This program does not take arguments.");
 100                 r = -EINVAL;
 101                 goto finish;
 102         }
 103
 104         uid = uid_current = geteuid();
 105         gid = getegid();
 106
 107         if (uid_current == 0) {
 108                 r = get_user_creds(&user, &uid, &gid, NULL, NULL);
 109                 if (r < 0) {
 110                         log_error_errno(r, "Cannot resolve user name %s: %m", user);
 111                         goto finish;
 112                 }
 113         }
 114
 115         r = load_clock_timestamp(uid, gid);
 116         if (r < 0)
 117                 goto finish;
 118
 119         /* Drop privileges, but only if we have been started as root. If we are not running as root we assume all
 120          * privileges are already dropped. */
 121         if (uid_current == 0) {
 122                 r = drop_privileges(uid, gid, (1ULL << CAP_SYS_TIME));
 123                 if (r < 0)
 124                         goto finish;
 125         }
 126
 127         assert_se(sigprocmask_many(SIG_BLOCK, NULL, SIGTERM, SIGINT, -1) >= 0);
 128
 129         r = manager_new(&m);
 130         if (r < 0) {
 131                 log_error_errno(r, "Failed to allocate manager: %m");
 132                 goto finish;
 133         }
 134
 135         r = manager_connect_bus(m);
 136         if (r < 0) {
 137                 log_error_errno(r, "Could not connect to bus: %m");
 138                 goto finish;
 139         }
 140
 141         if (clock_is_localtime(NULL) > 0) {
 142                 log_info("The system is configured to read the RTC time in the local time zone. "
 143                          "This mode cannot be fully supported. All system time to RTC updates are disabled.");
 144                 m->rtc_local_time = true;
 145         }
 146
 147         r = manager_parse_config_file(m);
 148         if (r < 0)
 149                 log_warning_errno(r, "Failed to parse configuration file: %m");
 150
 151         r = manager_parse_fallback_string(m, NTP_SERVERS);
 152         if (r < 0) {
 153                 log_error_errno(r, "Failed to parse fallback server strings: %m");
 154                 goto finish;
 155         }
 156
 157         log_debug("systemd-timesyncd running as pid " PID_FMT, getpid_cached());
 158         sd_notify(false,
 159                   "READY=1\n"
 160                   "STATUS=Daemon is running");
 161
 162         if (network_is_online()) {
 163                 r = manager_connect(m);
 164                 if (r < 0)
 165                         goto finish;
 166         }
 167
 168         r = sd_event_loop(m->event);
 169         if (r < 0) {
 170                 log_error_errno(r, "Failed to run event loop: %m");
 171                 goto finish;
 172         }
 173
 174         /* if we got an authoritative time, store it in the file system */
 175         if (m->sync)
 176                 (void) touch("/var/lib/systemd/timesync/clock");
 177
 178         sd_event_get_exit_code(m->event, &r);
 179
 180 finish:
 181         sd_notify(false,
 182                   "STOPPING=1\n"
 183                   "STATUS=Shutting down...");
 184
 185         return r < 0 ? EXIT_FAILURE : EXIT_SUCCESS;
 186 }