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                                 return log_error_errno(errno, "Failed to change file owner: %m");
  70                 }
  71
  72         } else {
  73                 r = mkdir_safe_label("/var/lib/systemd/timesync", 0755, uid, gid, true);
  74                 if (r < 0)
  75                         return log_error_errno(r, "Failed to create state directory: %m");
  76
  77                 /* create stamp file with the compiled-in date */
  78                 (void) touch_file("/var/lib/systemd/timesync/clock", false, min, uid, gid, 0644);
  79         }
  80
  81         ct = now(CLOCK_REALTIME);
  82         if (ct < min) {
  83                 struct timespec ts;
  84                 char date[FORMAT_TIMESTAMP_MAX];
  85
  86                 log_info("System clock time unset or jumped backwards, restoring from recorded timestamp: %s",
  87                          format_timestamp(date, sizeof(date), min));
  88
  89                 if (clock_settime(CLOCK_REALTIME, timespec_store(&ts, min)) < 0)
  90                         log_error_errno(errno, "Failed to restore system clock: %m");
  91         }
  92
  93         return 0;
  94 }
  95
  96 int main(int argc, char *argv[]) {
  97         _cleanup_(manager_freep) Manager *m = NULL;
  98         const char *user = "systemd-timesync";
  99         uid_t uid;
 100         gid_t gid;
 101         int r;
 102
 103         log_set_target(LOG_TARGET_AUTO);
 104         log_set_facility(LOG_CRON);
 105         log_parse_environment();
 106         log_open();
 107
 108         umask(0022);
 109
 110         if (argc != 1) {
 111                 log_error("This program does not take arguments.");
 112                 r = -EINVAL;
 113                 goto finish;
 114         }
 115
 116         r = get_user_creds(&user, &uid, &gid, NULL, NULL);
 117         if (r < 0) {
 118                 log_error_errno(r, "Cannot resolve user name %s: %m", user);
 119                 goto finish;
 120         }
 121
 122         r = load_clock_timestamp(uid, gid);
 123         if (r < 0)
 124                 goto finish;
 125
 126         /* Drop privileges, but only if we have been started as root. If we are not running as root we assume all
 127          * privileges are already dropped. */
 128         if (geteuid() == 0) {
 129                 r = drop_privileges(uid, gid, (1ULL << CAP_SYS_TIME));
 130                 if (r < 0)
 131                         goto finish;
 132         }
 133
 134         assert_se(sigprocmask_many(SIG_BLOCK, NULL, SIGTERM, SIGINT, -1) >= 0);
 135
 136         r = manager_new(&m);
 137         if (r < 0) {
 138                 log_error_errno(r, "Failed to allocate manager: %m");
 139                 goto finish;
 140         }
 141
 142         if (clock_is_localtime(NULL) > 0) {
 143                 log_info("The system is configured to read the RTC time in the local time zone. "
 144                          "This mode can not be fully supported. All system time to RTC updates are disabled.");
 145                 m->rtc_local_time = true;
 146         }
 147
 148         r = manager_parse_config_file(m);
 149         if (r < 0)
 150                 log_warning_errno(r, "Failed to parse configuration file: %m");
 151
 152         r = manager_parse_fallback_string(m, NTP_SERVERS);
 153         if (r < 0) {
 154                 log_error_errno(r, "Failed to parse fallback server strings: %m");
 155                 goto finish;
 156         }
 157
 158         log_debug("systemd-timesyncd running as pid " PID_FMT, getpid_cached());
 159         sd_notify(false,
 160                   "READY=1\n"
 161                   "STATUS=Daemon is running");
 162
 163         if (network_is_online()) {
 164                 r = manager_connect(m);
 165                 if (r < 0)
 166                         goto finish;
 167         }
 168
 169         r = sd_event_loop(m->event);
 170         if (r < 0) {
 171                 log_error_errno(r, "Failed to run event loop: %m");
 172                 goto finish;
 173         }
 174
 175         /* if we got an authoritative time, store it in the file system */
 176         if (m->sync)
 177                 (void) touch("/var/lib/systemd/timesync/clock");
 178
 179         sd_event_get_exit_code(m->event, &r);
 180
 181 finish:
 182         sd_notify(false,
 183                   "STOPPING=1\n"
 184                   "STATUS=Shutting down...");
 185
 186         return r < 0 ? EXIT_FAILURE : EXIT_SUCCESS;
 187 }