activation-helper: Ensure DBUS_STARTER_ADDRESS is set correctly

The fix for CVE-2012-3524 filters out all environment variables if
libdbus is used from a setuid program, to prevent various spoofing
attacks.

Unfortunately, the activation helper is a setuid program linking
libdbus, and this creates a regression for launched programs using
DBUS_STARTER_ADDRESS, since it will no longer exist.

Fix this by hardcoding the starter address to the default system bus
address.

Signed-off-by: Geoffrey Thomas <gthomas@mokafive.com>
Signed-off-by: Colin Walters <walters@verbum.org>

diff --git a/bus/activation-helper.c b/bus/activation-helper.c
index 7864e0f..cbc00d2 100644 (file)
--- a/bus/activation-helper.c
+++ b/bus/activation-helper.c
@@ -140,15 +140,12 @@ out_all:
   return desktop_file;
 }
 
-/* Clears the environment, except for DBUS_STARTER_x */
+/* Clears the environment, except for DBUS_STARTER_x,
+ * which we hardcode to the system bus.
+ */
 static dbus_bool_t
 clear_environment (DBusError *error)
 {
-  const char *starter_env = NULL;
-
-  /* we save the starter */
-  starter_env = _dbus_getenv ("DBUS_STARTER_ADDRESS");
-
 #ifndef ACTIVATION_LAUNCHER_TEST
   /* totally clear the environment */
   if (!_dbus_clearenv ())
@@ -159,11 +156,8 @@ clear_environment (DBusError *error)
     }
 #endif
 
-  /* restore the starter */
-  if (starter_env)
-    _dbus_setenv ("DBUS_STARTER_ADDRESS", starter_env);
-
-  /* set the type, which must be system if we got this far */
+  /* Ensure the bus is set to system */
+  _dbus_setenv ("DBUS_STARTER_ADDRESS", DBUS_SYSTEM_BUS_DEFAULT_ADDRESS);
   _dbus_setenv ("DBUS_STARTER_BUS_TYPE", "system");
 
   return TRUE;