Adding upstream version 255.4.upstream/255.4

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 231 insertions, 0 deletions

diff --git a/src/timesync/timesyncd.c b/src/timesync/timesyncd.c
new file mode 100644
index 0000000..1d8ebec
--- /dev/null
+++ b/src/timesync/timesyncd.c
@@ -0,0 +1,231 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <sys/stat.h>
+#include <sys/types.h>
+
+#include "sd-daemon.h"
+#include "sd-event.h"
+#include "sd-messages.h"
+
+#include "capability-util.h"
+#include "clock-util.h"
+#include "daemon-util.h"
+#include "fd-util.h"
+#include "fs-util.h"
+#include "main-func.h"
+#include "mkdir-label.h"
+#include "network-util.h"
+#include "process-util.h"
+#include "signal-util.h"
+#include "timesyncd-bus.h"
+#include "timesyncd-conf.h"
+#include "timesyncd-manager.h"
+#include "user-util.h"
+
+static int advance_tstamp(int fd, const struct stat *st) {
+        assert_se(fd >= 0);
+        assert_se(st);
+
+        /* So here's the problem: whenever we read the timestamp we'd like to ensure the next time we won't
+         * restore the exact same time again, but one at least one step further (so that comparing mtimes of
+         * the timestamp file is a reliable check that timesync did its thing). But file systems have
+         * different timestamp accuracy: traditional fat has 2s granularity, and even ext2 and friends expose
+         * different granularity depending on selected inode size during formatting! Hence, to ensure the
+         * timestamp definitely is increased, here's what we'll do: we'll first try to increase the timestamp
+         * by 1μs, write that and read it back. If it was updated, great. But if it was not, we'll instead
+         * increase the timestamp by 10μs, and do the same, then 100μs, then 1ms, and so on, until it works,
+         * or we reach 10s. If it still didn't work then, the fs is just broken and we give up. */
+
+        usec_t target = MAX3(now(CLOCK_REALTIME),
+                             TIME_EPOCH * USEC_PER_SEC,
+                             timespec_load(&st->st_mtim));
+
+        for (usec_t a = 1; a <= 10 * USEC_PER_SEC; a *= 10) { /* 1μs, 10μs, 100μs, 1ms, … 10s */
+                struct timespec ts[2];
+                struct stat new_st;
+
+                /* Bump to the maximum of the old timestamp advanced by the specified unit,  */
+                usec_t c = usec_add(target, a);
+
+                timespec_store(&ts[0], c);
+                ts[1] = ts[0];
+
+                if (futimens(fd, ts) < 0) {
+                        /* If this doesn't work at all, log, don't fail but give up */
+                        log_warning_errno(errno, "Unable to update mtime of timestamp file, ignoring: %m");
+                        return 0;
+                }
+
+                if (fstat(fd, &new_st) < 0)
+                        return log_error_errno(errno, "Failed to stat timestamp file: %m");
+
+                if (timespec_load(&new_st.st_mtim) > target) {
+                        log_debug("Successfully bumped timestamp file.");
+                        return 1;
+                }
+
+                log_debug("Tried to advance timestamp file by " USEC_FMT ", but this didn't work, file system timestamp granularity too coarse?", a);
+        }
+
+        log_debug("Gave up trying to advance timestamp file.");
+        return 0;
+}
+
+static int load_clock_timestamp(uid_t uid, gid_t gid) {
+        usec_t min = TIME_EPOCH * USEC_PER_SEC, ct;
+        _cleanup_close_ int fd = -EBADF;
+        int r;
+
+        /* Let's try to make sure that the clock is always monotonically increasing, by saving the clock
+         * whenever we have a new NTP time, or when we shut down, and restoring it when we start again. This
+         * is particularly helpful on systems lacking a battery backed RTC. We also will adjust the time to
+         * at least the build time of systemd. */
+
+        fd = open(CLOCK_FILE, O_RDWR|O_CLOEXEC, 0644);
+        if (fd < 0) {
+                if (errno != ENOENT)
+                        log_debug_errno(errno, "Unable to open timestamp file '" CLOCK_FILE "', ignoring: %m");
+
+                r = mkdir_safe_label(STATE_DIR, 0755, uid, gid,
+                                     MKDIR_FOLLOW_SYMLINK | MKDIR_WARN_MODE);
+                if (r < 0)
+                        log_debug_errno(r, "Failed to create state directory, ignoring: %m");
+
+                /* create stamp file with the compiled-in date */
+                r = touch_file(CLOCK_FILE, /* parents= */ false, min, uid, gid, 0644);
+                if (r < 0)
+                        log_debug_errno(r, "Failed to create %s, ignoring: %m", CLOCK_FILE);
+        } else {
+                struct stat st;
+                usec_t stamp;
+
+                /* check if the recorded time is later than the compiled-in one */
+                if (fstat(fd, &st) < 0)
+                        return log_error_errno(errno, "Unable to stat timestamp file '" CLOCK_FILE "': %m");
+
+                stamp = timespec_load(&st.st_mtim);
+                if (stamp > min)
+                        min = stamp;
+
+                /* Try to fix the access mode, so that we can still touch the file after dropping
+                 * privileges */
+                r = fchmod_and_chown(fd, 0644, uid, gid);
+                if (r < 0)
+                        log_full_errno(ERRNO_IS_PRIVILEGE(r) ? LOG_DEBUG : LOG_WARNING, r,
+                                       "Failed to chmod or chown %s, ignoring: %m", CLOCK_FILE);
+
+                (void) advance_tstamp(fd, &st);
+        }
+
+        ct = now(CLOCK_REALTIME);
+        if (ct > min)
+                return 0;
+
+        /* Not that it matters much, but we actually restore the clock to n+1 here rather than n, simply
+         * because we read n as time previously already and we want to progress here, i.e. not report the
+         * same time again. */
+        if (clock_settime(CLOCK_REALTIME, TIMESPEC_STORE(min+1)) < 0) {
+                log_warning_errno(errno, "Failed to restore system clock, ignoring: %m");
+                return 0;
+        }
+
+        log_struct(LOG_INFO,
+                   "MESSAGE_ID=" SD_MESSAGE_TIME_BUMP_STR,
+                   "REALTIME_USEC=" USEC_FMT, min+1,
+                   LOG_MESSAGE("System clock time unset or jumped backwards, restored from recorded timestamp: %s",
+                               FORMAT_TIMESTAMP(min+1)));
+        return 0;
+}
+
+static int run(int argc, char *argv[]) {
+        _cleanup_(manager_freep) Manager *m = NULL;
+        _unused_ _cleanup_(notify_on_cleanup) const char *notify_message = NULL;
+        const char *user = "systemd-timesync";
+        uid_t uid, uid_current;
+        gid_t gid;
+        int r;
+
+        log_set_facility(LOG_CRON);
+        log_setup();
+
+        umask(0022);
+
+        if (argc != 1)
+                return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "This program does not take arguments.");
+
+        uid = uid_current = geteuid();
+        gid = getegid();
+
+        if (uid_current == 0) {
+                r = get_user_creds(&user, &uid, &gid, NULL, NULL, 0);
+                if (r < 0)
+                        return log_error_errno(r, "Cannot resolve user name %s: %m", user);
+        }
+
+        r = load_clock_timestamp(uid, gid);
+        if (r < 0)
+                return r;
+
+        /* Drop privileges, but only if we have been started as root. If we are not running as root we assume all
+         * privileges are already dropped. */
+        if (uid_current == 0) {
+                r = drop_privileges(uid, gid, (1ULL << CAP_SYS_TIME));
+                if (r < 0)
+                        return log_error_errno(r, "Failed to drop privileges: %m");
+        }
+
+        assert_se(sigprocmask_many(SIG_BLOCK, NULL, SIGTERM, SIGINT, SIGRTMIN+18, -1) >= 0);
+
+        r = manager_new(&m);
+        if (r < 0)
+                return log_error_errno(r, "Failed to allocate manager: %m");
+
+        r = manager_connect_bus(m);
+        if (r < 0)
+                return log_error_errno(r, "Could not connect to bus: %m");
+
+        if (clock_is_localtime(NULL) > 0) {
+                log_info("The system is configured to read the RTC time in the local time zone. "
+                         "This mode cannot be fully supported. All system time to RTC updates are disabled.");
+                m->rtc_local_time = true;
+        }
+
+        r = manager_parse_config_file(m);
+        if (r < 0)
+                log_warning_errno(r, "Failed to parse configuration file: %m");
+
+        r = manager_parse_fallback_string(m, NTP_SERVERS);
+        if (r < 0)
+                return log_error_errno(r, "Failed to parse fallback server strings: %m");
+
+        log_debug("systemd-timesyncd running as pid " PID_FMT, getpid_cached());
+
+        notify_message = notify_start("READY=1\n"
+                                      "STATUS=Daemon is running",
+                                      NOTIFY_STOPPING);
+
+        r = manager_setup_save_time_event(m);
+        if (r < 0)
+                return r;
+
+        if (network_is_online()) {
+                r = manager_connect(m);
+                if (r < 0)
+                        return r;
+        }
+
+        r = sd_event_loop(m->event);
+        if (r < 0)
+                return log_error_errno(r, "Failed to run event loop: %m");
+
+        /* if we got an authoritative time, store it in the file system */
+        if (m->save_on_exit) {
+                r = touch(CLOCK_FILE);
+                if (r < 0)
+                        log_debug_errno(r, "Failed to touch " CLOCK_FILE ", ignoring: %m");
+        }
+
+        return 0;
+}
+
+DEFINE_MAIN_FUNCTION(run);