Add support for audio stream encryption

Clients must opt-in using the new encryptionFlags field

src/AudioStream.c

@@ -13,6 +13,8 @@ static PLT_THREAD udpPingThread;
 static PLT_THREAD receiveThread;
 static PLT_THREAD decoderThread;
 
+static PPLT_CRYPTO_CONTEXT audioDecryptionCtx;
+
 static unsigned short lastSeq;
 
 static bool receivedDataFromPeer;
@@ -65,6 +67,7 @@ int initializeAudioStream(void) {
     RtpqInitializeQueue(&rtpReorderQueue, RTPQ_DEFAULT_MAX_SIZE, RTPQ_DEFAULT_QUEUE_TIME);
     lastSeq = 0;
     receivedDataFromPeer = false;
+    audioDecryptionCtx = PltCreateCryptoContext();
 
     // For GFE 3.22 compatibility, we must start the audio ping thread before the RTSP handshake.
     // It will not reply to our RTSP PLAY request until the audio ping has been received.
@@ -109,6 +112,7 @@ void destroyAudioStream(void) {
         rtpSocket = INVALID_SOCKET;
     }
 
+    PltDestroyCryptoContext(audioDecryptionCtx);
     freePacketList(LbqDestroyLinkedBlockingQueue(&packetQueue));
     RtpqCleanupQueue(&rtpReorderQueue);
 }
@@ -144,7 +148,36 @@ static void decodeInputData(PQUEUED_AUDIO_PACKET packet) {
 
     lastSeq = rtp->sequenceNumber;
 
-    AudioCallbacks.decodeAndPlaySample((char*)(rtp + 1), packet->size - sizeof(*rtp));
+    if (AudioEncryptionEnabled) {
+        // We must have room for the AES padding which may be written to the buffer
+        unsigned char decryptedOpusData[MAX_PACKET_SIZE+16];
+        unsigned char iv[16] = {};
+        int dataLength = packet->size - sizeof(*rtp);
+
+        LC_ASSERT(dataLength <= MAX_PACKET_SIZE);
+
+        // The IV is the avkeyid (equivalent to the rikeyid) +
+        // the RTP sequence number, in big endian.
+        uint32_t ivSeq = BE32(*(uint32_t*)StreamConfig.remoteInputAesIv);
+        ivSeq += rtp->sequenceNumber;
+        ivSeq = BE32(ivSeq);
+
+        memcpy(iv, &ivSeq, sizeof(ivSeq));
+
+        if (!PltDecryptMessage(audioDecryptionCtx, ALGORITHM_AES_CBC, CIPHER_FLAG_RESET_IV | CIPHER_FLAG_FINISH,
+                               (unsigned char*)StreamConfig.remoteInputAesKey, sizeof(StreamConfig.remoteInputAesKey),
+                               iv, sizeof(iv),
+                               NULL, 0,
+                               (unsigned char*)(rtp + 1), dataLength,
+                               decryptedOpusData, &dataLength)) {
+            return;
+        }
+
+        AudioCallbacks.decodeAndPlaySample((char*)decryptedOpusData, dataLength);
+    }
+    else {
+        AudioCallbacks.decodeAndPlaySample((char*)(rtp + 1), packet->size - sizeof(*rtp));
+    }
 }
 
 static void ReceiveThreadProc(void* context) {

src/Connection.c

@@ -24,6 +24,7 @@ OPUS_MULTISTREAM_CONFIGURATION NormalQualityOpusConfig;
 OPUS_MULTISTREAM_CONFIGURATION HighQualityOpusConfig;
 int OriginalVideoBitrate;
 int AudioPacketDuration;
+bool AudioEncryptionEnabled;
 
 // Connection stages
 static const char* stageNames[STAGE_MAX] = {

src/Limelight-internal.h

@@ -27,6 +27,7 @@ extern OPUS_MULTISTREAM_CONFIGURATION NormalQualityOpusConfig;
 extern OPUS_MULTISTREAM_CONFIGURATION HighQualityOpusConfig;
 extern int OriginalVideoBitrate;
 extern int AudioPacketDuration;
+extern bool AudioEncryptionEnabled;
 
 #ifndef UINT24_MAX
 #define UINT24_MAX 0xFFFFFF

src/Limelight.h

@@ -29,6 +29,11 @@ extern "C" {
 #define COLOR_RANGE_LIMITED  0
 #define COLOR_RANGE_FULL     1
 
+// Values for 'encryptionFlags' field below
+#define ENCFLG_NONE  0x00000000
+#define ENCFLG_AUDIO 0x00000001
+#define ENCFLG_ALL   0xFFFFFFFF
+
 typedef struct _STREAM_CONFIGURATION {
     // Dimensions in pixels of the desired video stream
     int width;
@@ -87,6 +92,14 @@ typedef struct _STREAM_CONFIGURATION {
     // option (listed above). If not set, the encoder will default to Limited.
     int colorRange;
 
+    // Specifies the data streams where encryption may be enabled if supported
+    // by the host PC. Ideally, you would pass ENCFLG_ALL to encrypt everything
+    // that we support encrypting. However, lower performance hardware may not
+    // be able to support encrypting heavy stuff like video or audio data, so
+    // that encryption may be disabled here. Remote input encryption is always
+    // enabled.
+    int encryptionFlags;
+
     // AES encryption data for the remote input stream. This must be
     // the same as what was passed as rikey and rikeyid
     // in /launch and /resume requests.

src/RtspConnection.c

@@ -607,6 +607,7 @@ int performRtspHandshake(void) {
     currentSeqNumber = 1;
     hasSessionId = false;
     controlStreamId = APP_VERSION_AT_LEAST(7, 1, 431) ? "streamid=control/13/0" : "streamid=control/1/0";
+    AudioEncryptionEnabled = false;
 
     switch (AppVersionQuad[0]) {
         case 3:

src/SdpGenerator.c

@@ -139,13 +139,31 @@ static int addGen4Options(PSDP_OPTION* head, char* addrStr) {
     return err;
 }
 
+#define NVFF_BASE             0x07
+#define NVFF_AUDIO_ENCRYPTION 0x20
+#define NVFF_RI_ENCRYPTION    0x80
+
 static int addGen5Options(PSDP_OPTION* head) {
     int err = 0;
+    char payloadStr[32];
+
+    // This must be initialized to false already
+    LC_ASSERT(!AudioEncryptionEnabled);
 
     if (APP_VERSION_AT_LEAST(7, 1, 431)) {
-        // 0x20 enables audio encryption (which we don't support yet)
-        // 0x80 enables remote input encryption (which we do want)
-        err |= addAttributeString(head, "x-nv-general.featureFlags", "135");
+        unsigned int featureFlags;
+
+        // RI encryption is always enabled
+        featureFlags = NVFF_BASE | NVFF_RI_ENCRYPTION;
+
+        // Enable audio encryption if the client opted in
+        if (StreamConfig.encryptionFlags & ENCFLG_AUDIO) {
+            featureFlags |= NVFF_AUDIO_ENCRYPTION;
+            AudioEncryptionEnabled = true;
+        }
+
+        sprintf(payloadStr, "%u", featureFlags);
+        err |= addAttributeString(head, "x-nv-general.featureFlags", payloadStr);
 
         // Ask for the encrypted control protocol to ensure remote input will be encrypted.
         // This used to be done via separate RI encryption, but now it is all or nothing.