X-Git-Url: https://www.chiark.greenend.org.uk/ucgi/~ianmdlvl/git?a=blobdiff_plain;f=src%2Ftimesync%2Ftimesyncd.c;h=b13db1a3ec16e974eb558fceb0b9d6ec7aef1c45;hb=a57a27b2effe92f749a565df4f1276376b2d6dbc;hp=d26e8cbd6bbddef8ca01458b38ad6d597237d956;hpb=59a9fce47b3304bc9ce5d31b04ade5447b3910a4;p=elogind.git diff --git a/src/timesync/timesyncd.c b/src/timesync/timesyncd.c index d26e8cbd6..b13db1a3e 100644 --- a/src/timesync/timesyncd.c +++ b/src/timesync/timesyncd.c @@ -33,6 +33,9 @@ #include #include #include +#include +#include +#include #include "missing.h" #include "util.h" @@ -49,6 +52,8 @@ #include "sd-network.h" #include "event-util.h" #include "network-util.h" +#include "capability.h" +#include "mkdir.h" #include "timesyncd.h" #define TIME_T_MAX (time_t)((1UL << ((sizeof(time_t) << 3) - 1)) - 1) @@ -130,6 +135,78 @@ static int manager_clock_watch_setup(Manager *m); static int manager_connect(Manager *m); static void manager_disconnect(Manager *m); +static int load_clock(uid_t uid, gid_t gid) { + usec_t nt = TIME_EPOCH * USEC_PER_SEC, ct; + _cleanup_close_ int fd = -1; + + /* 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. */ + + mkdir_p("/var/lib/systemd", 0755); + + /* First, we try to create the clock file if it doesn't exist yet */ + fd = open("/var/lib/systemd/clock", O_RDWR|O_CLOEXEC|O_EXCL, 0644); + if (fd < 0) { + + fd = open("/var/lib/systemd/clock", O_RDWR|O_CLOEXEC|O_CREAT, 0644); + if (fd < 0) { + log_error("Failed to create /var/lib/systemd/clock: %m"); + return -errno; + } + + } else { + struct stat st; + usec_t ft; + + if (fstat(fd, &st) < 0) { + log_error("fstat() failed: %m"); + return -errno; + } + + ft = timespec_load(&st.st_mtim); + if (ft > nt) + nt = ft; + } + + ct = now(CLOCK_REALTIME); + if (nt > ct) { + struct timespec ts; + log_info("System clock time unset or jumped backwards, restoring."); + + if (clock_settime(CLOCK_REALTIME, timespec_store(&ts, nt)) < 0) + log_error("Failed to restore system clock: %m"); + } + + /* Try to fix the access mode, so that we can still + touch the file after dropping priviliges */ + fchmod(fd, 0644); + fchown(fd, uid, gid); + + return 0; +} + +static int save_clock(void) { + + static const struct timespec ts[2] = { + { .tv_sec = 0, .tv_nsec = UTIME_NOW }, + { .tv_sec = 0, .tv_nsec = UTIME_NOW }, + }; + + int r; + + r = utimensat(-1, "/var/lib/systemd/clock", ts, AT_SYMLINK_NOFOLLOW); + if (r < 0) { + log_warning("Failed to touch /var/lib/systemd/clock: %m"); + return -errno; + } + + return 0; +} + static double ntp_ts_to_d(const struct ntp_ts *ts) { return be32toh(ts->sec) + ((double)be32toh(ts->frac) / UINT_MAX); } @@ -205,7 +282,7 @@ static int manager_send_request(Manager *m) { return manager_connect(m); } - /* re-arm timer with incresing timeout, in case the packets never arrive back */ + /* re-arm timer with increasing timeout, in case the packets never arrive back */ if (m->retry_interval > 0) { if (m->retry_interval < NTP_POLL_INTERVAL_MAX_SEC * USEC_PER_SEC) m->retry_interval *= 2; @@ -369,6 +446,9 @@ static int manager_adjust_clock(Manager *m, double offset, int leap_sec) { } r = clock_adjtime(CLOCK_REALTIME, &tmx); + + save_clock(); + if (r < 0) return r; @@ -972,8 +1052,10 @@ static int manager_new(Manager **ret) { if (r < 0) return r; - sd_event_add_signal(m->event, &m->sigterm, SIGTERM, NULL, NULL); - sd_event_add_signal(m->event, &m->sigint, SIGINT, NULL, NULL); + sd_event_set_watchdog(m->event, true); + + sd_event_add_signal(m->event, NULL, SIGTERM, NULL, NULL); + sd_event_add_signal(m->event, NULL, SIGINT, NULL, NULL); r = sd_resolve_default(&m->resolve); if (r < 0) @@ -1000,9 +1082,6 @@ static void manager_free(Manager *m) { manager_disconnect(m); manager_flush_names(m); - sd_event_source_unref(m->sigint); - sd_event_source_unref(m->sigterm); - sd_event_source_unref(m->event_retry); sd_event_source_unref(m->network_event_source); @@ -1067,7 +1146,7 @@ static bool network_is_online(void) { int r; r = sd_network_get_operational_state(&state); - if (r >= 0 && streq("carrier", state)) + if (r >= 0 && (streq("routable", state) || streq("degraded", state))) return true; else return false; @@ -1138,8 +1217,77 @@ static int manager_network_monitor_listen(Manager *m) { return 0; } +static int drop_privileges(uid_t uid, gid_t gid) { + + static const cap_value_t bits[] = { + CAP_SYS_TIME, + }; + + _cleanup_cap_free_ cap_t d = NULL; + int r; + + /* Unfortunately we cannot leave privilege dropping to PID 1 + * here, since we want to run as user but want to keep te + * CAP_SYS_TIME capability. Since file capabilities have been + * introduced this cannot be done across exec() anymore, + * unless our binary has the capability configured in the file + * system, which we want to avoid. */ + + if (setresgid(gid, gid, gid) < 0) { + log_error("Failed change group ID: %m"); + return -errno; + } + + if (setgroups(0, NULL) < 0) { + log_error("Failed to drop auxiliary groups list: %m"); + return -errno; + } + + if (prctl(PR_SET_KEEPCAPS, 1) < 0) { + log_error("Failed to enable keep capabilities flag: %m"); + return -errno; + } + + r = setresuid(uid, uid, uid); + if (r < 0) { + log_error("Failed change user ID: %m"); + return -errno; + } + + if (prctl(PR_SET_KEEPCAPS, 0) < 0) { + log_error("Failed to disable keep capabilities flag: %m"); + return -errno; + } + + r = capability_bounding_set_drop(~(1ULL << CAP_SYS_TIME), true); + if (r < 0) { + log_error("Failed to drop capabilities: %s", strerror(-r)); + return r; + } + + d = cap_init(); + if (!d) + return log_oom(); + + if (cap_set_flag(d, CAP_EFFECTIVE, ELEMENTSOF(bits), bits, CAP_SET) < 0 || + cap_set_flag(d, CAP_PERMITTED, ELEMENTSOF(bits), bits, CAP_SET) < 0) { + log_error("Failed to enable capabilities bits: %m"); + return -errno; + } + + if (cap_set_proc(d) < 0) { + log_error("Failed to increase capabilities: %m"); + return -errno; + } + + return 0; +} + int main(int argc, char *argv[]) { + const char *user = "systemd-timesync"; _cleanup_manager_free_ Manager *m = NULL; + uid_t uid; + gid_t gid; int r; if (argc > 1) { @@ -1154,6 +1302,20 @@ int main(int argc, char *argv[]) { umask(0022); + r = get_user_creds(&user, &uid, &gid, NULL, NULL); + if (r < 0) { + log_error("Cannot resolve user name %s: %s", user, strerror(-r)); + return r; + } + + r = load_clock(uid, gid); + if (r < 0) + goto out; + + r = drop_privileges(uid, gid); + if (r < 0) + goto out; + assert_se(sigprocmask_many(SIG_BLOCK, SIGTERM, SIGINT, -1) == 0); r = manager_new(&m); @@ -1187,6 +1349,7 @@ int main(int argc, char *argv[]) { } sd_event_get_exit_code(m->event, &r); + save_clock(); out: sd_notify(false, "STATUS=Shutting down...");