src/dbus-common.c

   1 /*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
   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 #include "util.h"
  31
  32 int bus_check_peercred(DBusConnection *c) {
  33         int fd;
  34         struct ucred ucred;
  35         socklen_t l;
  36
  37         assert(c);
  38
  39         assert_se(dbus_connection_get_unix_fd(c, &fd));
  40
  41         l = sizeof(struct ucred);
  42         if (getsockopt(fd, SOL_SOCKET, SO_PEERCRED, &ucred, &l) < 0) {
  43                 log_error("SO_PEERCRED failed: %m");
  44                 return -errno;
  45         }
  46
  47         if (l != sizeof(struct ucred)) {
  48                 log_error("SO_PEERCRED returned wrong size.");
  49                 return -E2BIG;
  50         }
  51
  52         if (ucred.uid != 0)
  53                 return -EPERM;
  54
  55         return 1;
  56 }
  57
  58 int bus_connect(DBusBusType t, DBusConnection **_bus, bool *private, DBusError *error) {
  59         DBusConnection *bus;
  60
  61         assert(_bus);
  62
  63 #define TIMEOUT_USEC (60*USEC_PER_SEC)
  64
  65         /* If we are root, then let's not go via the bus */
  66         if (geteuid() == 0 && t == DBUS_BUS_SYSTEM) {
  67                 usec_t begin, tstamp;
  68
  69                 if (!(bus = dbus_connection_open_private("unix:abstract=/org/freedesktop/systemd1/private", error)))
  70                         return -EIO;
  71
  72                 if (bus_check_peercred(bus) < 0) {
  73                         dbus_connection_close(bus);
  74                         dbus_connection_unref(bus);
  75
  76                         dbus_set_error_const(error, DBUS_ERROR_ACCESS_DENIED, "Failed to verify owner of bus.");
  77                         return -EACCES;
  78                 }
  79
  80                 /* This complexity should probably move into D-Bus itself:
  81                  *
  82                  * https://bugs.freedesktop.org/show_bug.cgi?id=35189 */
  83                 begin = tstamp = now(CLOCK_MONOTONIC);
  84                 for (;;) {
  85
  86                         if (tstamp > begin + TIMEOUT_USEC)
  87                                 break;
  88
  89                         if (dbus_connection_get_is_authenticated(bus))
  90                                 break;
  91
  92                         if (!dbus_connection_read_write_dispatch(bus, ((begin + TIMEOUT_USEC - tstamp) + USEC_PER_MSEC - 1) / USEC_PER_MSEC))
  93                                 break;
  94
  95                         tstamp = now(CLOCK_MONOTONIC);
  96                 }
  97
  98                 if (!dbus_connection_get_is_connected(bus)) {
  99                         dbus_connection_close(bus);
 100                         dbus_connection_unref(bus);
 101
 102                         dbus_set_error_const(error, DBUS_ERROR_NO_SERVER, "Connection terminated during authentication.");
 103                         return -ECONNREFUSED;
 104                 }
 105
 106                 if (!dbus_connection_get_is_authenticated(bus)) {
 107                         dbus_connection_close(bus);
 108                         dbus_connection_unref(bus);
 109
 110                         dbus_set_error_const(error, DBUS_ERROR_TIMEOUT, "Failed to authenticate in time.");
 111                         return -EACCES;
 112                 }
 113
 114                 if (private)
 115                         *private = true;
 116
 117         } else {
 118                 if (!(bus = dbus_bus_get_private(t, error)))
 119                         return -EIO;
 120
 121                 if (private)
 122                         *private = false;
 123         }
 124
 125         dbus_connection_set_exit_on_disconnect(bus, FALSE);
 126
 127         *_bus = bus;
 128         return 0;
 129 }
 130
 131 const char *bus_error_message(const DBusError *error) {
 132         assert(error);
 133
 134         /* Sometimes the D-Bus server is a little bit too verbose with
 135          * its error messages, so let's override them here */
 136         if (dbus_error_has_name(error, DBUS_ERROR_ACCESS_DENIED))
 137                 return "Access denied";
 138
 139         return error->message;
 140 }