Audio, AudioOutput: guard against invalid packet types in AudioOutput…

…::addFrameToBuffer().

For packets we receive from Murmur, we check that they're a valid voice
packet on receipt.

However, some packets are not received by Murmur, but generated by the
client itself: packets for RecordUser, and local loopback packets.

If we mess up their type due to a bug, we'd previously allow them into the
AudioOutput system. This commit discards them before they get there.

src/Message.h

@@ -54,6 +54,21 @@ class MessageHandler {
 #undef MUMBLE_MH_MSG
 };
 
+/// UDPMessageTypeIsValidVoicePacket checks whether the given
+/// UDPMessageType is a valid voice packet.
+inline bool UDPMessageTypeIsValidVoicePacket(MessageHandler::UDPMessageType umt) {
+	switch (umt) {
+		case MessageHandler::UDPVoiceCELTAlpha:
+		case MessageHandler::UDPVoiceSpeex:
+		case MessageHandler::UDPVoiceCELTBeta:
+		case MessageHandler::UDPVoiceOpus:
+			return true;
+		case MessageHandler::UDPPing:
+			return false;
+	}
+	return false;
+}
+
 inline QString u8(const ::std::string &str) {
 	return QString::fromUtf8(str.data(), static_cast<int>(str.length()));
 }

src/mumble/AudioOutput.cpp

@@ -160,6 +160,11 @@ void AudioOutput::addFrameToBuffer(ClientUser *user, const QByteArray &qbaPacket
 	qrwlOutputs.lockForRead();
 	AudioOutputSpeech *aop = qobject_cast<AudioOutputSpeech *>(qmOutputs.value(user));
 
+	if (!UDPMessageTypeIsValidVoicePacket(type)) {
+		qWarning("AudioOutput: ignored frame with invalid message type 0x%x in addFrameToBuffer().", static_cast<unsigned char>(type));
+		return;
+	}
+
 	if (! aop || (aop->umtType != type)) {
 		qrwlOutputs.unlock();