Complete UDP audio protocol handling

gumble/gumble/client.go

@@ -78,6 +78,7 @@ type Client struct {
 	udpCryptoOut      *cryptState15
 	udpCryptoIn       *cryptState15
 	udpFrameNumber    uint64
+	udpProtobuf       bool
 	udpFallbackLogged atomic.Bool
 	udpFirstRecv      atomic.Bool
 	cryptOut          cryptState // client→server encryption
@@ -350,7 +351,7 @@ func (c *Client) EnableStereoEncoder() {
 func (c *Client) WriteAudio(format, target byte, sequence int64, final bool, data []byte, X, Y, Z *float32) error {
 	// Try Mumble 1.5 native UDP first (unless disabled)
 	if !c.Config.DisableUDP {
-		if sent, err := c.WriteAudioUDP15(uint32(target), data, final); sent {
+		if sent, err := c.WriteAudioUDP15(format, uint32(target), sequence, data, final, X, Y, Z); sent {
 			if err != nil {
 				log.Error("UDP15 send error: %v", err)
 			}

gumble/gumble/conn.go

@@ -80,7 +80,10 @@ func (c *Conn) WriteAudio(format, target byte, sequence int64, final bool, data
 	header := buff[:1+n+m]
 
 	var positionalLength int
-	if X != nil {
+	if X != nil || Y != nil || Z != nil {
+		if X == nil || Y == nil || Z == nil {
+			return errors.New("gumble: positional audio requires X, Y, and Z")
+		}
 		positionalLength = 3 * 4
 	}
 

gumble/gumble/handlers.go

@@ -74,6 +74,13 @@ func (c *Client) handleVersion(buffer []byte) error {
 	if err := proto.Unmarshal(buffer, &packet); err != nil {
 		return err
 	}
+	// Mumble 1.5 introduced protobuf UDP audio. Older servers retain the
+	// legacy UDP payload inside the same encrypted envelope.
+	if packet.VersionV1 != nil {
+		c.udpMu.Lock()
+		c.udpProtobuf = *packet.VersionV1 >= ClientVersion
+		c.udpMu.Unlock()
+	}
 	return nil
 }
 

gumble/gumble/udp15.go

@@ -63,7 +63,7 @@ func pbDecodeVarint(buf []byte) (uint64, int) {
 // encodeUDPAudio builds a MumbleUDP.Audio protobuf message.
 // If session == 0, sender_session is omitted (used for outbound).
 // Uses standard protobuf varint encoding, not Mumble's custom varint.
-func encodeUDPAudio(target uint32, frameNumber uint64, opusData []byte, terminator bool) []byte {
+func encodeUDPAudio(target uint32, frameNumber uint64, opusData []byte, terminator bool, X, Y, Z *float32) []byte {
 	var buf bytes.Buffer
 	var tmp [10]byte // max protobuf varint size
 
@@ -84,6 +84,17 @@ func encodeUDPAudio(target uint32, frameNumber uint64, opusData []byte, terminat
 		buf.Write(tmp[:n])
 		buf.Write(opusData)
 	}
+	if X != nil && Y != nil && Z != nil {
+		n := pbEncodeVarint(tmp[:], uint64((6<<3)|2))
+		buf.Write(tmp[:n])
+		n = pbEncodeVarint(tmp[:], 12)
+		buf.Write(tmp[:n])
+		for _, value := range []float32{*X, *Y, *Z} {
+			var fixed [4]byte
+			binary.LittleEndian.PutUint32(fixed[:], math.Float32bits(value))
+			buf.Write(fixed[:])
+		}
+	}
 	if terminator {
 		n := pbEncodeVarint(tmp[:], uint64((16<<3)|0))
 		buf.Write(tmp[:n])
@@ -367,11 +378,28 @@ func ocb15Encrypt(key, nonce, plaintext []byte) (ciphertext, tag []byte) {
 	for remaining > 16 {
 		shift2inplace(delta)
 
+		// Mitigate the XEX* forgery attack (eprint 2019/311), matching
+		// Mumble's CryptStateOCB2 implementation.
+		flipBit := remaining <= 32
+		if flipBit {
+			for _, b := range plaintext[pos : pos+15] {
+				if b != 0 {
+					flipBit = false
+					break
+				}
+			}
+		}
 		xor16(checksum, checksum, plaintext[pos:pos+16])
+		if flipBit {
+			checksum[0] ^= 1
+		}
 
 		// C = delta XOR AES_K(delta XOR plaintext)
 		tmp := make([]byte, 16)
 		xorBytes(tmp, plaintext[pos:pos+16], delta)
+		if flipBit {
+			tmp[0] ^= 1
+		}
 		block.Encrypt(tmp, tmp)
 		xorBytes(tmp, tmp, delta)
 
@@ -460,6 +488,18 @@ func ocb15Decrypt(key, nonce, ciphertext []byte) (plaintext, tag []byte, err err
 	xor16(csTemp, csTemp, pad)
 	xor16(checksum, checksum, csTemp)
 
+	// Reject the XEX* forgery pattern before authenticating the tag.
+	matchesDelta := true
+	for i := 0; i < 15; i++ {
+		if csTemp[i] != delta[i] {
+			matchesDelta = false
+			break
+		}
+	}
+	if matchesDelta {
+		return nil, nil, errors.New("gumble: OCB XEX* forgery detected")
+	}
+
 	// Tag = AES_K(3*delta XOR checksum)
 	shift3inplace(delta)
 	xor16(delta, delta, checksum)
@@ -535,10 +575,32 @@ func (c *Client) setUDP15Crypto(key, clientNonce, serverNonce []byte) error {
 	return nil
 }
 
+// encodeLegacyUDPAudio builds the pre-1.5 UDPVoice packet payload.
+func encodeLegacyUDPAudio(format, target byte, sequence int64, data []byte, final bool, X, Y, Z *float32) []byte {
+	var header [1 + varint.MaxVarintLen*2]byte
+	header[0] = format<<5 | target
+	n := varint.Encode(header[1:], sequence)
+	length := int64(len(data))
+	if final {
+		length |= 0x2000
+	}
+	m := varint.Encode(header[1+n:], length)
+	payload := append([]byte(nil), header[:1+n+m]...)
+	payload = append(payload, data...)
+	if X != nil && Y != nil && Z != nil {
+		for _, value := range []float32{*X, *Y, *Z} {
+			var fixed [4]byte
+			binary.LittleEndian.PutUint32(fixed[:], math.Float32bits(value))
+			payload = append(payload, fixed[:]...)
+		}
+	}
+	return payload
+}
+
 // ---------------------------------------------------------------------------
-// WriteAudioUDP15 writes an encrypted audio packet using Mumble 1.5 native UDP.
+// WriteAudioUDP15 writes encrypted UDP audio in the negotiated payload format.
 // Returns true if sent, false if TCP should be used.
-func (c *Client) WriteAudioUDP15(target uint32, data []byte, final bool) (bool, error) {
+func (c *Client) WriteAudioUDP15(format byte, target uint32, sequence int64, data []byte, final bool, X, Y, Z *float32) (bool, error) {
 	// Encryption and socket writes must remain ordered: otherwise a later
 	// packet can reach the server before the packet with the preceding IV.
 	c.udpWriteMu.Lock()
@@ -546,13 +608,21 @@ func (c *Client) WriteAudioUDP15(target uint32, data []byte, final bool) (bool,
 	c.udpMu.Lock()
 	cs, udpConn := c.udpCryptoOut, c.udpConn
 	frameNum := c.udpFrameNumber
-	c.udpFrameNumber++
+	protobuf := c.udpProtobuf
+	if protobuf {
+		c.udpFrameNumber++
+	}
 	c.udpMu.Unlock()
 	if cs == nil || udpConn == nil {
 		return false, nil
 	}
 
-	payload := append([]byte{0x00}, encodeUDPAudio(target, frameNum, data, final)...)
+	var payload []byte
+	if protobuf {
+		payload = append([]byte{0x00}, encodeUDPAudio(target, frameNum, data, final, X, Y, Z)...)
+	} else {
+		payload = encodeLegacyUDPAudio(format, byte(target), sequence, data, final, X, Y, Z)
+	}
 	encrypted, err := cs.encrypt15(payload)
 	if err != nil {
 		log.Error("UDP15 encrypt failed: %v", err)

gumble/gumble/udp15_test.go

@@ -142,7 +142,7 @@ func TestUDPAudioProtobuf(t *testing.T) {
 	}
 
 	for _, tt := range tests {
-		encoded := encodeUDPAudio(uint32(tt.session), uint64(tt.frameNumber), tt.opusData, tt.terminator)
+		encoded := encodeUDPAudio(uint32(tt.session), uint64(tt.frameNumber), tt.opusData, tt.terminator, nil, nil, nil)
 		session, frameNum, opusData, terminator, _, _, _ := decodeUDPAudio(encoded)
 
 		if session != 0 {

gumble/gumbleopenal/stream.go

@@ -512,6 +512,20 @@ func (s *Stream) OnAudioStream(e *gumble.AudioStreamEvent) {
 	}(e)
 }
 
+func applyVolumeAdjustment(sample int16, adjustment float32) int16 {
+	if adjustment == 0 || adjustment == 1 {
+		return sample
+	}
+	adjusted := float32(sample) * adjustment
+	if adjusted > 32767 {
+		return 32767
+	}
+	if adjusted < -32768 {
+		return -32768
+	}
+	return int16(adjusted)
+}
+
 // processAudioPacket decodes and queues a single audio packet for playback.
 // Returns the updated emptyBufs slice after consuming a buffer.
 // The caller must call reclaim() before invoking this to ensure buffers
@@ -544,7 +558,7 @@ func (s *Stream) processAudioPacket(packet *gumble.AudioPacket, user *gumble.Use
 		// Process stereo samples as pairs
 		for i := 0; i < samples*2; i += 2 {
 			// Process left channel with saturation protection
-			sample := packet.AudioBuffer[i]
+			sample := applyVolumeAdjustment(packet.AudioBuffer[i], packet.VolumeAdjustment)
 			if boost > 1 {
 				boosted := int32(sample) * int32(boost)
 				if boosted > 32767 {
@@ -563,7 +577,7 @@ func (s *Stream) processAudioPacket(packet *gumble.AudioPacket, user *gumble.Use
 			rawPtr += 2
 
 			// Process right channel with saturation protection
-			sample = packet.AudioBuffer[i+1]
+			sample = applyVolumeAdjustment(packet.AudioBuffer[i+1], packet.VolumeAdjustment)
 			if boost > 1 {
 				boosted := int32(sample) * int32(boost)
 				if boosted > 32767 {
@@ -584,7 +598,7 @@ func (s *Stream) processAudioPacket(packet *gumble.AudioPacket, user *gumble.Use
 	} else {
 		// Process mono samples with saturation protection
 		for i := 0; i < samples; i++ {
-			sample := packet.AudioBuffer[i]
+			sample := applyVolumeAdjustment(packet.AudioBuffer[i], packet.VolumeAdjustment)
 			if boost > 1 {
 				boosted := int32(sample) * int32(boost)
 				if boosted > 32767 {