src/dbus-common.c

   1 /*-*- Mode: C; c-basic-offset: 8 -*-*/
   2
   3 /***
   4   This file is part of systemd.
   5
   6   Copyright 2010 Lennart Poettering
   7
   8   systemd is free software; you can redistribute it and/or modify it
   9   under the terms of the GNU General Public License as published by
  10   the Free Software Foundation; either version 2 of the License, or
  11   (at your option) any later version.
  12
  13   systemd is distributed in the hope that it will be useful, but
  14   WITHOUT ANY WARRANTY; without even the implied warranty of
  15   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  16   General Public License for more details.
  17
  18   You should have received a copy of the GNU General Public License
  19   along with systemd; If not, see <http://www.gnu.org/licenses/>.
  20 ***/
  21
  22 #include <assert.h>
  23 #include <sys/socket.h>
  24 #include <errno.h>
  25 #include <unistd.h>
  26 #include <dbus/dbus.h>
  27
  28 #include "log.h"
  29 #include "dbus-common.h"
  30
  31 int bus_check_peercred(DBusConnection *c) {
  32         int fd;
  33         struct ucred ucred;
  34         socklen_t l;
  35
  36         assert(c);
  37
  38         assert_se(dbus_connection_get_unix_fd(c, &fd));
  39
  40         l = sizeof(struct ucred);
  41         if (getsockopt(fd, SOL_SOCKET, SO_PEERCRED, &ucred, &l) < 0) {
  42                 log_error("SO_PEERCRED failed: %m");
  43                 return -errno;
  44         }
  45
  46         if (l != sizeof(struct ucred)) {
  47                 log_error("SO_PEERCRED returned wrong size.");
  48                 return -E2BIG;
  49         }
  50
  51         if (ucred.uid != 0)
  52                 return -EPERM;
  53
  54         return 1;
  55 }
  56
  57 int bus_connect(DBusBusType t, DBusConnection **_bus, bool *private, DBusError *error) {
  58         DBusConnection *bus;
  59
  60         assert(_bus);
  61
  62         /* If we are root, then let's not go via the bus */
  63         if (geteuid() == 0 && t == DBUS_BUS_SYSTEM) {
  64
  65                 if (!(bus = dbus_connection_open_private("unix:abstract=/org/freedesktop/systemd1/private", error)))
  66                         return -EIO;
  67
  68                 if (bus_check_peercred(bus) < 0) {
  69                         dbus_connection_unref(bus);
  70
  71                         dbus_set_error_const(error, DBUS_ERROR_ACCESS_DENIED, "Failed to verify owner of bus.");
  72                         return -EACCES;
  73                 }
  74
  75                 if (private)
  76                         *private = true;
  77
  78         } else {
  79                 if (!(bus = dbus_bus_get_private(t, error)))
  80                         return -EIO;
  81
  82                 if (private)
  83                         *private = false;
  84         }
  85
  86         dbus_connection_set_exit_on_disconnect(bus, FALSE);
  87
  88         *_bus = bus;
  89         return 0;
  90 }