src/resolve/resolved.c

   1 /* SPDX-License-Identifier: LGPL-2.1+ */
   2
   3 #include <sys/stat.h>
   4 #include <sys/types.h>
   5 #include <unistd.h>
   6
   7 #include "sd-daemon.h"
   8 #include "sd-event.h"
   9
  10 #include "capability-util.h"
  11 #include "daemon-util.h"
  12 #include "main-func.h"
  13 #include "mkdir.h"
  14 #include "resolved-conf.h"
  15 #include "resolved-manager.h"
  16 #include "resolved-resolv-conf.h"
  17 #include "selinux-util.h"
  18 #include "signal-util.h"
  19 #include "user-util.h"
  20
  21 static int run(int argc, char *argv[]) {
  22         _cleanup_(notify_on_cleanup) const char *notify_stop = NULL;
  23         _cleanup_(manager_freep) Manager *m = NULL;
  24         const char *user = "systemd-resolve";
  25         uid_t uid;
  26         gid_t gid;
  27         int r;
  28
  29         log_setup_service();
  30
  31         if (argc != 1)
  32                 return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "This program takes no arguments.");
  33
  34         umask(0022);
  35
  36         r = mac_selinux_init();
  37         if (r < 0)
  38                 return log_error_errno(r, "SELinux setup failed: %m");
  39
  40         r = get_user_creds(&user, &uid, &gid, NULL, NULL, 0);
  41         if (r < 0)
  42                 return log_error_errno(r, "Cannot resolve user name %s: %m", user);
  43
  44         /* Always create the directory where resolv.conf will live */
  45         r = mkdir_safe_label("/run/systemd/resolve", 0755, uid, gid, MKDIR_WARN_MODE);
  46         if (r < 0)
  47                 return log_error_errno(r, "Could not create runtime directory: %m");
  48
  49         /* Drop privileges, but only if we have been started as root. If we are not running as root we assume most
  50          * privileges are already dropped. */
  51         if (getuid() == 0) {
  52
  53                 /* Drop privileges, but keep three caps. Note that we drop those too, later on (see below) */
  54                 r = drop_privileges(uid, gid,
  55                                     (UINT64_C(1) << CAP_NET_RAW)|          /* needed for SO_BINDTODEVICE */
  56                                     (UINT64_C(1) << CAP_NET_BIND_SERVICE)| /* needed to bind on port 53 */
  57                                     (UINT64_C(1) << CAP_SETPCAP)           /* needed in order to drop the caps later */);
  58                 if (r < 0)
  59                         return log_error_errno(r, "Failed to drop privileges: %m");
  60         }
  61
  62         assert_se(sigprocmask_many(SIG_BLOCK, NULL, SIGTERM, SIGINT, SIGUSR1, SIGUSR2, SIGRTMIN+1, -1) >= 0);
  63
  64         r = manager_new(&m);
  65         if (r < 0)
  66                 return log_error_errno(r, "Could not create manager: %m");
  67
  68         r = manager_start(m);
  69         if (r < 0)
  70                 return log_error_errno(r, "Failed to start manager: %m");
  71
  72         /* Write finish default resolv.conf to avoid a dangling symlink */
  73         (void) manager_write_resolv_conf(m);
  74
  75         (void) manager_check_resolv_conf(m);
  76
  77         /* Let's drop the remaining caps now */
  78         r = capability_bounding_set_drop(0, true);
  79         if (r < 0)
  80                 return log_error_errno(r, "Failed to drop remaining caps: %m");
  81
  82         notify_stop = notify_start(NOTIFY_READY, NOTIFY_STOPPING);
  83
  84         r = sd_event_loop(m->event);
  85         if (r < 0)
  86                 return log_error_errno(r, "Event loop failed: %m");
  87
  88         return 0;
  89 }
  90
  91 DEFINE_MAIN_FUNCTION(run);