src/timesync/timesyncd.c

   1 /***
   2   This file is part of systemd.
   3
   4   Copyright 2014 Kay Sievers, Lennart Poettering
   5
   6   systemd is free software; you can redistribute it and/or modify it
   7   under the terms of the GNU Lesser General Public License as published by
   8   the Free Software Foundation; either version 2.1 of the License, or
   9   (at your option) any later version.
  10
  11   systemd is distributed in the hope that it will be useful, but
  12   WITHOUT ANY WARRANTY; without even the implied warranty of
  13   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  14   Lesser General Public License for more details.
  15
  16   You should have received a copy of the GNU Lesser General Public License
  17   along with systemd; If not, see <http://www.gnu.org/licenses/>.
  18 ***/
  19
  20 #include "sd-daemon.h"
  21 #include "sd-event.h"
  22
  23 #include "capability-util.h"
  24 #include "clock-util.h"
  25 #include "fd-util.h"
  26 #include "fs-util.h"
  27 #include "mkdir.h"
  28 #include "network-util.h"
  29 #include "process-util.h"
  30 #include "signal-util.h"
  31 #include "timesyncd-conf.h"
  32 #include "timesyncd-manager.h"
  33 #include "user-util.h"
  34
  35 static int load_clock_timestamp(uid_t uid, gid_t gid) {
  36         _cleanup_close_ int fd = -1;
  37         usec_t min = TIME_EPOCH * USEC_PER_SEC;
  38         usec_t ct;
  39         int r;
  40
  41         /* Let's try to make sure that the clock is always
  42          * monotonically increasing, by saving the clock whenever we
  43          * have a new NTP time, or when we shut down, and restoring it
  44          * when we start again. This is particularly helpful on
  45          * systems lacking a battery backed RTC. We also will adjust
  46          * the time to at least the build time of systemd. */
  47
  48         fd = open("/var/lib/systemd/timesync/clock", O_RDWR|O_CLOEXEC, 0644);
  49         if (fd >= 0) {
  50                 struct stat st;
  51                 usec_t stamp;
  52
  53                 /* check if the recorded time is later than the compiled-in one */
  54                 r = fstat(fd, &st);
  55                 if (r >= 0) {
  56                         stamp = timespec_load(&st.st_mtim);
  57                         if (stamp > min)
  58                                 min = stamp;
  59                 }
  60
  61                 if (geteuid() == 0) {
  62                         /* Try to fix the access mode, so that we can still
  63                            touch the file after dropping priviliges */
  64                         r = fchmod(fd, 0644);
  65                         if (r < 0)
  66                                 return log_error_errno(errno, "Failed to change file access mode: %m");
  67                         r = fchown(fd, uid, gid);
  68                                 return log_error_errno(errno, "Failed to change file owner: %m");
  69                 }
  70
  71         } else {
  72                 r = mkdir_safe_label("/var/lib/systemd/timesync", 0755, uid, gid, true);
  73                 if (r < 0)
  74                         return log_error_errno(r, "Failed to create state directory: %m");
  75
  76                 /* create stamp file with the compiled-in date */
  77                 (void) touch_file("/var/lib/systemd/timesync/clock", false, min, uid, gid, 0644);
  78         }
  79
  80         ct = now(CLOCK_REALTIME);
  81         if (ct < min) {
  82                 struct timespec ts;
  83                 char date[FORMAT_TIMESTAMP_MAX];
  84
  85                 log_info("System clock time unset or jumped backwards, restoring from recorded timestamp: %s",
  86                          format_timestamp(date, sizeof(date), min));
  87
  88                 if (clock_settime(CLOCK_REALTIME, timespec_store(&ts, min)) < 0)
  89                         log_error_errno(errno, "Failed to restore system clock: %m");
  90         }
  91
  92         return 0;
  93 }
  94
  95 int main(int argc, char *argv[]) {
  96         _cleanup_(manager_freep) Manager *m = NULL;
  97         const char *user = "systemd-timesync";
  98         uid_t uid;
  99         gid_t gid;
 100         int r;
 101
 102         log_set_target(LOG_TARGET_AUTO);
 103         log_set_facility(LOG_CRON);
 104         log_parse_environment();
 105         log_open();
 106
 107         umask(0022);
 108
 109         if (argc != 1) {
 110                 log_error("This program does not take arguments.");
 111                 r = -EINVAL;
 112                 goto finish;
 113         }
 114
 115         r = get_user_creds(&user, &uid, &gid, NULL, NULL);
 116         if (r < 0) {
 117                 log_error_errno(r, "Cannot resolve user name %s: %m", user);
 118                 goto finish;
 119         }
 120
 121         r = load_clock_timestamp(uid, gid);
 122         if (r < 0)
 123                 goto finish;
 124
 125         /* Drop privileges, but only if we have been started as root. If we are not running as root we assume all
 126          * privileges are already dropped. */
 127         if (geteuid() == 0) {
 128                 r = drop_privileges(uid, gid, (1ULL << CAP_SYS_TIME));
 129                 if (r < 0)
 130                         goto finish;
 131         }
 132
 133         assert_se(sigprocmask_many(SIG_BLOCK, NULL, SIGTERM, SIGINT, -1) >= 0);
 134
 135         r = manager_new(&m);
 136         if (r < 0) {
 137                 log_error_errno(r, "Failed to allocate manager: %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 can not 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 }