src/timesync/timesyncd.c

   1 /* SPDX-License-Identifier: LGPL-2.1+ */
   2 /***
   3   This file is part of systemd.
   4
   5   Copyright 2014 Kay Sievers, Lennart Poettering
   6
   7   systemd is free software; you can redistribute it and/or modify it
   8   under the terms of the GNU Lesser General Public License as published by
   9   the Free Software Foundation; either version 2.1 of the License, or
  10   (at your option) any later version.
  11
  12   systemd is distributed in the hope that it will be useful, but
  13   WITHOUT ANY WARRANTY; without even the implied warranty of
  14   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  15   Lesser General Public License for more details.
  16
  17   You should have received a copy of the GNU Lesser General Public License
  18   along with systemd; If not, see <http://www.gnu.org/licenses/>.
  19 ***/
  20
  21 #include "sd-daemon.h"
  22 #include "sd-event.h"
  23
  24 #include "capability-util.h"
  25 #include "clock-util.h"
  26 #include "fd-util.h"
  27 #include "fs-util.h"
  28 #include "mkdir.h"
  29 #include "network-util.h"
  30 #include "process-util.h"
  31 #include "signal-util.h"
  32 #include "timesyncd-conf.h"
  33 #include "timesyncd-manager.h"
  34 #include "user-util.h"
  35
  36 static int load_clock_timestamp(uid_t uid, gid_t gid) {
  37         _cleanup_close_ int fd = -1;
  38         usec_t min = TIME_EPOCH * USEC_PER_SEC;
  39         usec_t ct;
  40         int r;
  41
  42         /* Let's try to make sure that the clock is always
  43          * monotonically increasing, by saving the clock whenever we
  44          * have a new NTP time, or when we shut down, and restoring it
  45          * when we start again. This is particularly helpful on
  46          * systems lacking a battery backed RTC. We also will adjust
  47          * the time to at least the build time of systemd. */
  48
  49         fd = open("/var/lib/systemd/timesync/clock", O_RDWR|O_CLOEXEC, 0644);
  50         if (fd >= 0) {
  51                 struct stat st;
  52                 usec_t stamp;
  53
  54                 /* check if the recorded time is later than the compiled-in one */
  55                 r = fstat(fd, &st);
  56                 if (r >= 0) {
  57                         stamp = timespec_load(&st.st_mtim);
  58                         if (stamp > min)
  59                                 min = stamp;
  60                 }
  61
  62                 if (geteuid() == 0) {
  63                         /* Try to fix the access mode, so that we can still
  64                            touch the file after dropping priviliges */
  65                         r = fchmod(fd, 0644);
  66                         if (r < 0)
  67                                 return log_error_errno(errno, "Failed to change file access mode: %m");
  68                         r = fchown(fd, uid, gid);
  69                         if (r < 0)
  70                                 return log_error_errno(errno, "Failed to change file owner: %m");
  71                 }
  72
  73         } else {
  74                 r = mkdir_safe_label("/var/lib/systemd/timesync", 0755, uid, gid, true);
  75                 if (r < 0)
  76                         return log_error_errno(r, "Failed to create state directory: %m");
  77
  78                 /* create stamp file with the compiled-in date */
  79                 (void) touch_file("/var/lib/systemd/timesync/clock", false, min, uid, gid, 0644);
  80         }
  81
  82         ct = now(CLOCK_REALTIME);
  83         if (ct < min) {
  84                 struct timespec ts;
  85                 char date[FORMAT_TIMESTAMP_MAX];
  86
  87                 log_info("System clock time unset or jumped backwards, restoring from recorded timestamp: %s",
  88                          format_timestamp(date, sizeof(date), min));
  89
  90                 if (clock_settime(CLOCK_REALTIME, timespec_store(&ts, min)) < 0)
  91                         log_error_errno(errno, "Failed to restore system clock: %m");
  92         }
  93
  94         return 0;
  95 }
  96
  97 int main(int argc, char *argv[]) {
  98         _cleanup_(manager_freep) Manager *m = NULL;
  99         const char *user = "systemd-timesync";
 100         uid_t uid, uid_current;
 101         gid_t gid;
 102         int r;
 103
 104         log_set_target(LOG_TARGET_AUTO);
 105         log_set_facility(LOG_CRON);
 106         log_parse_environment();
 107         log_open();
 108
 109         umask(0022);
 110
 111         if (argc != 1) {
 112                 log_error("This program does not take arguments.");
 113                 r = -EINVAL;
 114                 goto finish;
 115         }
 116
 117         uid = uid_current = geteuid();
 118         gid = getegid();
 119
 120         if (uid_current == 0) {
 121                 r = get_user_creds(&user, &uid, &gid, NULL, NULL);
 122                 if (r < 0) {
 123                         log_error_errno(r, "Cannot resolve user name %s: %m", user);
 124                         goto finish;
 125                 }
 126         }
 127
 128         r = load_clock_timestamp(uid, gid);
 129         if (r < 0)
 130                 goto finish;
 131
 132         /* Drop privileges, but only if we have been started as root. If we are not running as root we assume all
 133          * privileges are already dropped. */
 134         if (uid_current == 0) {
 135                 r = drop_privileges(uid, gid, (1ULL << CAP_SYS_TIME));
 136                 if (r < 0)
 137                         goto finish;
 138         }
 139
 140         assert_se(sigprocmask_many(SIG_BLOCK, NULL, SIGTERM, SIGINT, -1) >= 0);
 141
 142         r = manager_new(&m);
 143         if (r < 0) {
 144                 log_error_errno(r, "Failed to allocate manager: %m");
 145                 goto finish;
 146         }
 147
 148         if (clock_is_localtime(NULL) > 0) {
 149                 log_info("The system is configured to read the RTC time in the local time zone. "
 150                          "This mode cannot be fully supported. All system time to RTC updates are disabled.");
 151                 m->rtc_local_time = true;
 152         }
 153
 154         r = manager_parse_config_file(m);
 155         if (r < 0)
 156                 log_warning_errno(r, "Failed to parse configuration file: %m");
 157
 158         r = manager_parse_fallback_string(m, NTP_SERVERS);
 159         if (r < 0) {
 160                 log_error_errno(r, "Failed to parse fallback server strings: %m");
 161                 goto finish;
 162         }
 163
 164         log_debug("systemd-timesyncd running as pid " PID_FMT, getpid_cached());
 165         sd_notify(false,
 166                   "READY=1\n"
 167                   "STATUS=Daemon is running");
 168
 169         if (network_is_online()) {
 170                 r = manager_connect(m);
 171                 if (r < 0)
 172                         goto finish;
 173         }
 174
 175         r = sd_event_loop(m->event);
 176         if (r < 0) {
 177                 log_error_errno(r, "Failed to run event loop: %m");
 178                 goto finish;
 179         }
 180
 181         /* if we got an authoritative time, store it in the file system */
 182         if (m->sync)
 183                 (void) touch("/var/lib/systemd/timesync/clock");
 184
 185         sd_event_get_exit_code(m->event, &r);
 186
 187 finish:
 188         sd_notify(false,
 189                   "STOPPING=1\n"
 190                   "STATUS=Shutting down...");
 191
 192         return r < 0 ? EXIT_FAILURE : EXIT_SUCCESS;
 193 }