diff options
authorAlban Crequy <>2014-05-20 14:37:37 +0100
committerSimon McVittie <>2014-06-05 14:36:17 +0100
commit24c590703ca47eb71ddef453de43126b90954567 (patch)
parent416898324decb7b6d86083a6e2ddc71e8d835feb (diff)
CVE-2014-3477: deliver activation errors correctly, fixing Denial of Service
How it should work: When a D-Bus message activates a service, LSMs (SELinux or AppArmor) check whether the message can be delivered after the service has been activated. The service is considered activated when its well-known name is requested with org.freedesktop.DBus.RequestName. When the message delivery is denied, the service stays activated but should not receive the activating message (the message which triggered the activation). dbus-daemon is supposed to drop the activating message and reply to the sender with a D-Bus error message. However, it does not work as expected: 1. The error message is delivered to the service instead of being delivered to the sender. As an example, the error message could be something like: An SELinux policy prevents this sender from sending this message to this recipient, [...] member="MaliciousMethod" If the sender and the service are malicious confederates and agree on a protocol to insert information in the member name, the sender can leak information to the service, even though the LSM attempted to block the communication between the sender and the service. 2. The error message is delivered as a reply to the RequestName call from service. It means the activated service will believe it cannot request the name and might exit. The sender could activate the service frequently and systemd will give up activating it. Thus the denial of service. The following changes fix the bug: - bus_activation_send_pending_auto_activation_messages() only returns an error in case of OOM. The prototype is changed to return TRUE, or FALSE on OOM (and its only caller sets the OOM error). - When a client is not allowed to talk to the service, a D-Bus error message is pre-allocated to be delivered to the client as part of the transaction. The error is not propagated to the caller so RequestName will not fail (except on OOM). [fixed a misleading comment -smcv] Bug: Reviewed-by: Simon McVittie <> Reviewed-by: Colin Walters <>
3 files changed, 24 insertions, 11 deletions
diff --git a/bus/activation.c b/bus/activation.c
index fa6c1568..149cca8a 100644
--- a/bus/activation.c
+++ b/bus/activation.c
@@ -1162,14 +1162,11 @@ bus_activation_service_created (BusActivation *activation,
bus_activation_send_pending_auto_activation_messages (BusActivation *activation,
BusService *service,
- BusTransaction *transaction,
- DBusError *error)
+ BusTransaction *transaction)
BusPendingActivation *pending_activation;
DBusList *link;
/* Check if it's a pending activation */
pending_activation = _dbus_hash_table_lookup_string (activation->pending_activations,
bus_service_get_name (service));
@@ -1186,6 +1183,9 @@ bus_activation_send_pending_auto_activation_messages (BusActivation *activation
if (entry->auto_activation && (entry->connection == NULL || dbus_connection_get_is_connected (entry->connection)))
DBusConnection *addressed_recipient;
+ DBusError error;
+ dbus_error_init (&error);
addressed_recipient = bus_service_get_primary_owners_connection (service);
@@ -1193,8 +1193,22 @@ bus_activation_send_pending_auto_activation_messages (BusActivation *activation
if (!bus_dispatch_matches (transaction,
- entry->activation_message, error))
- goto error;
+ entry->activation_message, &error))
+ {
+ /* If permission is denied, we just want to return the error
+ * to the original method invoker; in particular, we don't
+ * want to make the RequestName call fail with that error
+ * (see fd.o #78979, CVE-2014-3477). */
+ if (!bus_transaction_send_error_reply (transaction, entry->connection,
+ &error, entry->activation_message))
+ {
+ bus_connection_send_oom_error (entry->connection,
+ entry->activation_message);
+ }
+ link = next;
+ continue;
+ }
link = next;
@@ -1203,7 +1217,6 @@ bus_activation_send_pending_auto_activation_messages (BusActivation *activation
if (!add_restore_pending_to_transaction (transaction, pending_activation))
_dbus_verbose ("Could not add cancel hook to transaction to revert removing pending activation\n");
- BUS_SET_OOM (error);
goto error;
diff --git a/bus/activation.h b/bus/activation.h
index 97f25b1f..fc5d426f 100644
--- a/bus/activation.h
+++ b/bus/activation.h
@@ -62,8 +62,7 @@ dbus_bool_t dbus_activation_systemd_failure (BusActivation *activation,
dbus_bool_t bus_activation_send_pending_auto_activation_messages (BusActivation *activation,
BusService *service,
- BusTransaction *transaction,
- DBusError *error);
+ BusTransaction *transaction);
#endif /* BUS_ACTIVATION_H */
diff --git a/bus/services.c b/bus/services.c
index 01a720ed..584485b1 100644
--- a/bus/services.c
+++ b/bus/services.c
@@ -588,8 +588,9 @@ bus_registry_acquire_service (BusRegistry *registry,
activation = bus_context_get_activation (registry->context);
retval = bus_activation_send_pending_auto_activation_messages (activation,
- transaction,
- error);
+ transaction);
+ if (!retval)
+ BUS_SET_OOM (error);
return retval;