Fix TURN server permissions enforcement when relaying

Author: paullouisageneau

src/server.c

@@ -478,6 +478,21 @@ int server_forward(juice_server_t *server, server_turn_alloc_t *alloc) {
 		}
 		addr_unmap_inet6_v4mapped((struct sockaddr *)&record.addr, &record.len);
 
+		// RFC 5766 8. Permissions:
+		// When a UDP datagram arrives at the relayed transport address for the allocation, the
+		// server extracts the source IP address from the IP header. The server then compares this
+		// address with the IP address associated with each permission in the list of permissions
+		// for the allocation. If no match is found, relaying is not permitted, and the server
+		// silently discards the UDP datagram.
+		if (!turn_has_permission(&alloc->map, &record)) {
+			if (JLOG_DEBUG_ENABLED) {
+				char record_str[ADDR_MAX_STRING_LEN];
+				addr_record_to_string(&record, record_str, ADDR_MAX_STRING_LEN);
+				JLOG_DEBUG("No permission for remote address %s, discarding", record_str);
+			}
+			return -1;
+		}
+
 		uint16_t channel;
 		if (turn_get_bound_channel(&alloc->map, &record, &channel)) {
 			// Use ChannelData
@@ -1063,12 +1078,21 @@ int server_process_turn_channel_bind(juice_server_t *server, const stun_message_
 		                                credentials);
 	}
 
+	// RFC 5766 11.3. Receiving a ChannelBind Response
+	// When the client receives a ChannelBind success response, it updates its data structures to
+	// record that the channel binding is now active. It also updates its data structures to record
+	// that the corresponding permission has been installed or refreshed.
 	const addr_record_t *peer = msg->peers;
 	if (!turn_bind_channel(&alloc->map, peer, msg->transaction_id, channel, BIND_LIFETIME)) {
 		server_answer_stun_error(server, msg->transaction_id, src, msg->msg_method, 500,
 		                         credentials);
 		return -1;
 	}
+	if (!turn_set_permission(&alloc->map, msg->transaction_id, peer, PERMISSION_LIFETIME)) {
+		server_answer_stun_error(server, msg->transaction_id, src, msg->msg_method, 500,
+		                         credentials);
+		return -1;
+	}
 
 	stun_message_t ans;
 	memset(&ans, 0, sizeof(ans));
@@ -1105,7 +1129,11 @@ int server_process_turn_send(juice_server_t *server, const stun_message_t *msg,
 
 	const addr_record_t *peer = msg->peers;
 	if (!turn_has_permission(&alloc->map, peer)) {
-		JLOG_WARN("No permission for peer address");
+		if (JLOG_WARN_ENABLED) {
+			char peer_str[ADDR_MAX_STRING_LEN];
+			addr_record_to_string(peer, peer_str, ADDR_MAX_STRING_LEN);
+			JLOG_WARN("No permission for peer address %s", peer_str);
+		}
 		return -1;
 	}
 

src/turn.c

@@ -156,12 +156,14 @@ static void delete_entry(turn_map_t *map, turn_entry_t *entry) {
 */
 static turn_entry_t *find_entry(turn_map_t *map, const addr_record_t *record,
                                 turn_entry_type_t type, bool allow_deleted) {
-	unsigned long key = (addr_record_hash(record, false) + (int)type) % map->map_size;
+	// RFC 5766: only addresses are compared and port numbers are not considered.
+	unsigned long key = (addr_record_hash(record, false /*no port*/) + (int)type) % map->map_size;
 	unsigned long pos = key;
 	while (true) {
 		turn_entry_t *entry = map->map + pos;
 		if (entry->type == TURN_ENTRY_TYPE_EMPTY ||
-		    (entry->type == type && addr_record_is_equal(&entry->record, record, false)))
+		    (entry->type == type &&
+		     addr_record_is_equal(&entry->record, record, false /*no port*/)))
 			break;
 
 		if (allow_deleted && entry->type == TURN_ENTRY_TYPE_DELETED)
@@ -241,6 +243,13 @@ void turn_destroy_map(turn_map_t *map) {
 
 bool turn_set_permission(turn_map_t *map, const uint8_t *transaction_id,
                          const addr_record_t *record, timediff_t duration) {
+	if (record) {
+		if (JLOG_DEBUG_ENABLED) {
+			char record_str[ADDR_MAX_STRING_LEN];
+			addr_record_to_string(record, record_str, ADDR_MAX_STRING_LEN);
+			JLOG_DEBUG("Updating TURN permission for address %s", record_str);
+		}
+	}
 	return update_timestamp(map, TURN_ENTRY_TYPE_PERMISSION, transaction_id, record, duration);
 }
 
@@ -254,6 +263,15 @@ bool turn_has_permission(turn_map_t *map, const addr_record_t *record) {
 
 bool turn_bind_channel(turn_map_t *map, const addr_record_t *record, const uint8_t *transaction_id,
                        uint16_t channel, timediff_t duration) {
+	if(!record)
+		return false;
+
+	if (JLOG_DEBUG_ENABLED) {
+		char record_str[ADDR_MAX_STRING_LEN];
+		addr_record_to_string(record, record_str, ADDR_MAX_STRING_LEN);
+		JLOG_DEBUG("Binding TURN channel %hu to address %s", channel, record_str);
+	}
+
 	if (!is_valid_channel(channel)) {
 		JLOG_ERROR("Invalid channel number: 0x%hX", channel);
 		return false;