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 <stdio.h>
  27 #include <stdlib.h>
  28 #include <dbus/dbus.h>
  29
  30 #include "log.h"
  31 #include "dbus-common.h"
  32 #include "util.h"
  33 #include "def.h"
  34
  35 int bus_check_peercred(DBusConnection *c) {
  36         int fd;
  37         struct ucred ucred;
  38         socklen_t l;
  39
  40         assert(c);
  41
  42         assert_se(dbus_connection_get_unix_fd(c, &fd));
  43
  44         l = sizeof(struct ucred);
  45         if (getsockopt(fd, SOL_SOCKET, SO_PEERCRED, &ucred, &l) < 0) {
  46                 log_error("SO_PEERCRED failed: %m");
  47                 return -errno;
  48         }
  49
  50         if (l != sizeof(struct ucred)) {
  51                 log_error("SO_PEERCRED returned wrong size.");
  52                 return -E2BIG;
  53         }
  54
  55         if (ucred.uid != 0)
  56                 return -EPERM;
  57
  58         return 1;
  59 }
  60
  61 static int sync_auth(DBusConnection *bus, DBusError *error) {
  62         usec_t begin, tstamp;
  63
  64         assert(bus);
  65
  66         /* This complexity should probably move into D-Bus itself:
  67          *
  68          * https://bugs.freedesktop.org/show_bug.cgi?id=35189 */
  69
  70         begin = tstamp = now(CLOCK_MONOTONIC);
  71         for (;;) {
  72
  73                 if (tstamp > begin + DEFAULT_TIMEOUT_USEC)
  74                         break;
  75
  76                 if (dbus_connection_get_is_authenticated(bus))
  77                         break;
  78
  79                 if (!dbus_connection_read_write_dispatch(bus, ((begin + DEFAULT_TIMEOUT_USEC - tstamp) + USEC_PER_MSEC - 1) / USEC_PER_MSEC))
  80                         break;
  81
  82                 tstamp = now(CLOCK_MONOTONIC);
  83         }
  84
  85         if (!dbus_connection_get_is_connected(bus)) {
  86                 dbus_set_error_const(error, DBUS_ERROR_NO_SERVER, "Connection terminated during authentication.");
  87                 return -ECONNREFUSED;
  88         }
  89
  90         if (!dbus_connection_get_is_authenticated(bus)) {
  91                 dbus_set_error_const(error, DBUS_ERROR_TIMEOUT, "Failed to authenticate in time.");
  92                 return -EACCES;
  93         }
  94
  95         return 0;
  96 }
  97
  98 int bus_connect(DBusBusType t, DBusConnection **_bus, bool *private, DBusError *error) {
  99         DBusConnection *bus;
 100         int r;
 101
 102         assert(_bus);
 103
 104         /* If we are root, then let's not go via the bus */
 105         if (geteuid() == 0 && t == DBUS_BUS_SYSTEM) {
 106
 107                 if (!(bus = dbus_connection_open_private("unix:path=/dev/.run/systemd/private", error))) {
 108 #ifndef LEGACY
 109                         dbus_error_free(error);
 110
 111                         /* Retry with the pre v21 socket name, to ease upgrades */
 112                         if (!(bus = dbus_connection_open_private("unix:abstract=/org/freedesktop/systemd1/private", error)))
 113 #endif
 114                                 return -EIO;
 115                 }
 116
 117                 dbus_connection_set_exit_on_disconnect(bus, FALSE);
 118
 119                 if (bus_check_peercred(bus) < 0) {
 120                         dbus_connection_close(bus);
 121                         dbus_connection_unref(bus);
 122
 123                         dbus_set_error_const(error, DBUS_ERROR_ACCESS_DENIED, "Failed to verify owner of bus.");
 124                         return -EACCES;
 125                 }
 126
 127                 if (private)
 128                         *private = true;
 129
 130         } else {
 131                 if (!(bus = dbus_bus_get_private(t, error)))
 132                         return -EIO;
 133
 134                 dbus_connection_set_exit_on_disconnect(bus, FALSE);
 135
 136                 if (private)
 137                         *private = false;
 138         }
 139
 140         if ((r = sync_auth(bus, error)) < 0) {
 141                 dbus_connection_close(bus);
 142                 dbus_connection_unref(bus);
 143                 return r;
 144         }
 145
 146         *_bus = bus;
 147         return 0;
 148 }
 149
 150 int bus_connect_system_ssh(const char *user, const char *host, DBusConnection **_bus, DBusError *error) {
 151         DBusConnection *bus;
 152         char *p = NULL;
 153         int r;
 154
 155         assert(_bus);
 156         assert(user || host);
 157
 158         if (user && host)
 159                 asprintf(&p, "exec:path=ssh,argv1=-xT,argv2=%s@%s,argv3=systemd-stdio-bridge", user, host);
 160         else if (user)
 161                 asprintf(&p, "exec:path=ssh,argv1=-xT,argv2=%s@localhost,argv3=systemd-stdio-bridge", user);
 162         else if (host)
 163                 asprintf(&p, "exec:path=ssh,argv1=-xT,argv2=%s,argv3=systemd-stdio-bridge", host);
 164
 165         if (!p) {
 166                 dbus_set_error_const(error, DBUS_ERROR_NO_MEMORY, NULL);
 167                 return -ENOMEM;
 168         }
 169
 170         bus = dbus_connection_open_private(p, error);
 171         free(p);
 172
 173         if (!bus)
 174                 return -EIO;
 175
 176         dbus_connection_set_exit_on_disconnect(bus, FALSE);
 177
 178         if ((r = sync_auth(bus, error)) < 0) {
 179                 dbus_connection_close(bus);
 180                 dbus_connection_unref(bus);
 181                 return r;
 182         }
 183
 184         if (!dbus_bus_register(bus, error)) {
 185                 dbus_connection_close(bus);
 186                 dbus_connection_unref(bus);
 187                 return r;
 188         }
 189
 190         *_bus = bus;
 191         return 0;
 192 }
 193
 194 int bus_connect_system_polkit(DBusConnection **_bus, DBusError *error) {
 195         DBusConnection *bus;
 196         int r;
 197
 198         assert(_bus);
 199
 200         /* Don't bother with PolicyKit if we are root */
 201         if (geteuid() == 0)
 202                 return bus_connect(DBUS_BUS_SYSTEM, _bus, NULL, error);
 203
 204         if (!(bus = dbus_connection_open_private("exec:path=pkexec,argv1=" SYSTEMD_STDIO_BRIDGE_BINARY_PATH, error)))
 205                 return -EIO;
 206
 207         dbus_connection_set_exit_on_disconnect(bus, FALSE);
 208
 209         if ((r = sync_auth(bus, error)) < 0) {
 210                 dbus_connection_close(bus);
 211                 dbus_connection_unref(bus);
 212                 return r;
 213         }
 214
 215         if (!dbus_bus_register(bus, error)) {
 216                 dbus_connection_close(bus);
 217                 dbus_connection_unref(bus);
 218                 return r;
 219         }
 220
 221         *_bus = bus;
 222         return 0;
 223 }
 224
 225 const char *bus_error_message(const DBusError *error) {
 226         assert(error);
 227
 228         /* Sometimes the D-Bus server is a little bit too verbose with
 229          * its error messages, so let's override them here */
 230         if (dbus_error_has_name(error, DBUS_ERROR_ACCESS_DENIED))
 231                 return "Access denied";
 232
 233         return error->message;
 234 }