src/resolve/resolved.c

   1 /* SPDX-License-Identifier: LGPL-2.1+ */
   2
   3 #include "sd-daemon.h"
   4 #include "sd-event.h"
   5
   6 #include "capability-util.h"
   7 #include "mkdir.h"
   8 #include "resolved-conf.h"
   9 #include "resolved-manager.h"
  10 #include "resolved-resolv-conf.h"
  11 #include "selinux-util.h"
  12 #include "signal-util.h"
  13 #include "user-util.h"
  14
  15 int main(int argc, char *argv[]) {
  16         _cleanup_(manager_freep) Manager *m = NULL;
  17         const char *user = "systemd-resolve";
  18         uid_t uid;
  19         gid_t gid;
  20         int r;
  21
  22         log_setup_service();
  23
  24         if (argc != 1) {
  25                 log_error("This program takes no arguments.");
  26                 r = -EINVAL;
  27                 goto finish;
  28         }
  29
  30         umask(0022);
  31
  32         r = mac_selinux_init();
  33         if (r < 0) {
  34                 log_error_errno(r, "SELinux setup failed: %m");
  35                 goto finish;
  36         }
  37
  38         r = get_user_creds(&user, &uid, &gid, NULL, NULL, 0);
  39         if (r < 0) {
  40                 log_error_errno(r, "Cannot resolve user name %s: %m", user);
  41                 goto finish;
  42         }
  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                 log_error_errno(r, "Could not create runtime directory: %m");
  48                 goto finish;
  49         }
  50
  51         /* Drop privileges, but only if we have been started as root. If we are not running as root we assume most
  52          * privileges are already dropped. */
  53         if (getuid() == 0) {
  54
  55                 /* Drop privileges, but keep three caps. Note that we drop those too, later on (see below) */
  56                 r = drop_privileges(uid, gid,
  57                                     (UINT64_C(1) << CAP_NET_RAW)|          /* needed for SO_BINDTODEVICE */
  58                                     (UINT64_C(1) << CAP_NET_BIND_SERVICE)| /* needed to bind on port 53 */
  59                                     (UINT64_C(1) << CAP_SETPCAP)           /* needed in order to drop the caps later */);
  60                 if (r < 0)
  61                         goto finish;
  62         }
  63
  64         assert_se(sigprocmask_many(SIG_BLOCK, NULL, SIGTERM, SIGINT, SIGUSR1, SIGUSR2, SIGRTMIN+1, -1) >= 0);
  65
  66         r = manager_new(&m);
  67         if (r < 0) {
  68                 log_error_errno(r, "Could not create manager: %m");
  69                 goto finish;
  70         }
  71
  72         r = manager_start(m);
  73         if (r < 0) {
  74                 log_error_errno(r, "Failed to start manager: %m");
  75                 goto finish;
  76         }
  77
  78         /* Write finish default resolv.conf to avoid a dangling symlink */
  79         (void) manager_write_resolv_conf(m);
  80
  81         (void) manager_check_resolv_conf(m);
  82
  83         /* Let's drop the remaining caps now */
  84         r = capability_bounding_set_drop(0, true);
  85         if (r < 0) {
  86                 log_error_errno(r, "Failed to drop remaining caps: %m");
  87                 goto finish;
  88         }
  89
  90         sd_notify(false,
  91                   "READY=1\n"
  92                   "STATUS=Processing requests...");
  93
  94         r = sd_event_loop(m->event);
  95         if (r < 0) {
  96                 log_error_errno(r, "Event loop failed: %m");
  97                 goto finish;
  98         }
  99
 100         sd_event_get_exit_code(m->event, &r);
 101
 102 finish:
 103         sd_notify(false,
 104                   "STOPPING=1\n"
 105                   "STATUS=Shutting down...");
 106
 107         return r < 0 ? EXIT_FAILURE : EXIT_SUCCESS;
 108 }