src/resolve/resolved.c

   1 /* SPDX-License-Identifier: LGPL-2.1-or-later */
   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 "bus-log-control-api.h"
  11 #include "capability-util.h"
  12 #include "daemon-util.h"
  13 #include "main-func.h"
  14 #include "mkdir-label.h"
  15 #include "resolved-bus.h"
  16 #include "resolved-conf.h"
  17 #include "resolved-manager.h"
  18 #include "resolved-resolv-conf.h"
  19 #include "selinux-util.h"
  20 #include "service-util.h"
  21 #include "signal-util.h"
  22 #include "user-util.h"
  23
  24 static int run(int argc, char *argv[]) {
  25         _cleanup_(manager_freep) Manager *m = NULL;
  26         _unused_ _cleanup_(notify_on_cleanup) const char *notify_stop = NULL;
  27         int r;
  28
  29         log_setup();
  30
  31         r = service_parse_argv("systemd-resolved.service",
  32                                "Provide name resolution with caching using DNS, mDNS, LLMNR.",
  33                                BUS_IMPLEMENTATIONS(&manager_object,
  34                                                    &log_control_object),
  35                                argc, argv);
  36         if (r <= 0)
  37                 return r;
  38
  39         umask(0022);
  40
  41         r = mac_init();
  42         if (r < 0)
  43                 return r;
  44
  45         /* Drop privileges, but only if we have been started as root. If we are not running as root we assume most
  46          * privileges are already dropped and we can't create our directory. */
  47         if (getuid() == 0) {
  48                 const char *user = "systemd-resolve";
  49                 uid_t uid;
  50                 gid_t gid;
  51
  52                 r = get_user_creds(&user, &uid, &gid, NULL, NULL, 0);
  53                 if (r < 0)
  54                         return log_error_errno(r, "Cannot resolve user name %s: %m", user);
  55
  56                 /* As we're root, we can create the directory where resolv.conf will live */
  57                 r = mkdir_safe_label("/run/systemd/resolve", 0755, uid, gid, MKDIR_WARN_MODE);
  58                 if (r < 0)
  59                         return log_error_errno(r, "Could not create runtime directory: %m");
  60
  61                 /* Drop privileges, but keep three caps. Note that we drop two of those too, later on (see below) */
  62                 r = drop_privileges(uid, gid,
  63                                     (UINT64_C(1) << CAP_NET_RAW)|          /* needed for SO_BINDTODEVICE */
  64                                     (UINT64_C(1) << CAP_NET_BIND_SERVICE)| /* needed to bind on port 53 */
  65                                     (UINT64_C(1) << CAP_SETPCAP)           /* needed in order to drop the caps later */);
  66                 if (r < 0)
  67                         return log_error_errno(r, "Failed to drop privileges: %m");
  68         }
  69
  70         assert_se(sigprocmask_many(SIG_BLOCK, NULL, SIGTERM, SIGINT, SIGUSR1, SIGUSR2, SIGRTMIN+1, SIGRTMIN+18, -1) >= 0);
  71
  72         r = manager_new(&m);
  73         if (r < 0)
  74                 return log_error_errno(r, "Could not create manager: %m");
  75
  76         r = manager_start(m);
  77         if (r < 0)
  78                 return log_error_errno(r, "Failed to start manager: %m");
  79
  80         /* Write finish default resolv.conf to avoid a dangling symlink */
  81         (void) manager_write_resolv_conf(m);
  82
  83         (void) manager_check_resolv_conf(m);
  84
  85         /* Let's drop the remaining caps now */
  86         r = capability_bounding_set_drop((UINT64_C(1) << CAP_NET_RAW), true);
  87         if (r < 0)
  88                 return log_error_errno(r, "Failed to drop remaining caps: %m");
  89
  90         notify_stop = notify_start(NOTIFY_READY, NOTIFY_STOPPING);
  91
  92         r = sd_event_loop(m->event);
  93         if (r < 0)
  94                 return log_error_errno(r, "Event loop failed: %m");
  95
  96         return 0;
  97 }
  98
  99 DEFINE_MAIN_FUNCTION(run);