Add video encryption support

src/Limelight.h

@@ -32,6 +32,7 @@ extern "C" {
 // Values for 'encryptionFlags' field below
 #define ENCFLG_NONE  0x00000000
 #define ENCFLG_AUDIO 0x00000001
+#define ENCFLG_VIDEO 0x00000002
 #define ENCFLG_ALL   0xFFFFFFFF
 
 // This function returns a string that you SHOULD append to the /launch and /resume

src/SdpGenerator.c

@@ -276,6 +276,18 @@ static PSDP_OPTION getAttributesList(char*urlSafeAddr) {
         if (EncryptionFeaturesSupported & SS_ENC_CONTROL_V2) {
             EncryptionFeaturesEnabled |= SS_ENC_CONTROL_V2;
         }
+
+        // If video encryption is supported by the host and desired by the client, use it
+        if ((EncryptionFeaturesSupported & SS_ENC_VIDEO) && (StreamConfig.encryptionFlags & ENCFLG_VIDEO)) {
+            EncryptionFeaturesEnabled |= SS_ENC_VIDEO;
+        }
+        else if ((EncryptionFeaturesRequested & SS_ENC_VIDEO) && !(StreamConfig.encryptionFlags & ENCFLG_VIDEO)) {
+            // If video encryption is explicitly requested by the host but *not* by the client,
+            // we'll encrypt anyway (since we are capable of doing so) and print a warning.
+            Limelog("Enabling video encryption by host request despite client opt-out. Performance may suffer!");
+            EncryptionFeaturesEnabled |= SS_ENC_VIDEO;
+        }
+
         snprintf(payloadStr, sizeof(payloadStr), "%u", EncryptionFeaturesEnabled);
         err |= addAttributeString(&optionHead, "x-ss-general.encryptionEnabled", payloadStr);
     }

src/Video.h

@@ -9,6 +9,11 @@ typedef struct _QUEUED_DECODE_UNIT {
 
 #pragma pack(push, 1)
 
+typedef struct _ENC_VIDEO_HEADER {
+    uint8_t iv[16];
+    uint8_t tag[16];
+} ENC_VIDEO_HEADER, *PENC_VIDEO_HEADER;
+
 #define FLAG_CONTAINS_PIC_DATA 0x1
 #define FLAG_EOF 0x2
 #define FLAG_SOF 0x4

src/VideoStream.c

@@ -10,6 +10,8 @@ static RTP_VIDEO_QUEUE rtpQueue;
 static SOCKET rtpSocket = INVALID_SOCKET;
 static SOCKET firstFrameSocket = INVALID_SOCKET;
 
+static PPLT_CRYPTO_CONTEXT decryptionCtx;
+
 static PLT_THREAD udpPingThread;
 static PLT_THREAD receiveThread;
 static PLT_THREAD decoderThread;
@@ -36,6 +38,7 @@ static bool receivedFullFrame;
 void initializeVideoStream(void) {
     initializeVideoDepacketizer(StreamConfig.packetSize);
     RtpvInitializeQueue(&rtpQueue);
+    decryptionCtx = PltCreateCryptoContext();
     receivedDataFromPeer = false;
     firstDataTimeMs = 0;
     receivedFullFrame = false;
@@ -43,6 +46,7 @@ void initializeVideoStream(void) {
 
 // Clean up the video stream
 void destroyVideoStream(void) {
+    PltDestroyCryptoContext(decryptionCtx);
     destroyVideoDepacketizer();
     RtpvCleanupQueue(&rtpQueue);
 }
@@ -80,14 +84,19 @@ static void VideoPingThreadProc(void* context) {
 // Receive thread proc
 static void VideoReceiveThreadProc(void* context) {
     int err;
-    int bufferSize, receiveSize;
+    int bufferSize, receiveSize, decryptedSize, minSize;
     char* buffer;
+    char* encryptedBuffer;
     int queueStatus;
     bool useSelect;
     int waitingForVideoMs;
+    bool encrypted;
 
-    receiveSize = StreamConfig.packetSize + MAX_RTP_HEADER_SIZE;
-    bufferSize = receiveSize + sizeof(RTPV_QUEUE_ENTRY);
+    encrypted = !!(EncryptionFeaturesEnabled & SS_ENC_VIDEO);
+    decryptedSize = StreamConfig.packetSize + MAX_RTP_HEADER_SIZE;
+    minSize = sizeof(RTP_PACKET) + ((EncryptionFeaturesEnabled & SS_ENC_VIDEO) ? sizeof(ENC_VIDEO_HEADER) : 0);
+    receiveSize = decryptedSize + ((EncryptionFeaturesEnabled & SS_ENC_VIDEO) ? sizeof(ENC_VIDEO_HEADER) : 0);
+    bufferSize = decryptedSize + sizeof(RTPV_QUEUE_ENTRY);
     buffer = NULL;
 
     if (setNonFatalRecvTimeoutMs(rtpSocket, UDP_RECV_POLL_TIMEOUT_MS) < 0) {
@@ -99,6 +108,19 @@ static void VideoReceiveThreadProc(void* context) {
         useSelect = false;
     }
 
+    // Allocate a staging buffer to use for each received packet
+    if (encrypted) {
+        encryptedBuffer = (char*)malloc(receiveSize);
+        if (encryptedBuffer == NULL) {
+            Limelog("Video Receive: malloc() failed\n");
+            ListenerCallbacks.connectionTerminated(-1);
+            return;
+        }
+    }
+    else {
+        encryptedBuffer = NULL;
+    }
+
     waitingForVideoMs = 0;
     while (!PltIsThreadInterrupted(&receiveThread)) {
         PRTP_PACKET packet;
@@ -108,11 +130,14 @@ static void VideoReceiveThreadProc(void* context) {
             if (buffer == NULL) {
                 Limelog("Video Receive: malloc() failed\n");
                 ListenerCallbacks.connectionTerminated(-1);
-                return;
+                break;
             }
         }
 
-        err = recvUdpSocket(rtpSocket, buffer, receiveSize, useSelect);
+        err = recvUdpSocket(rtpSocket,
+                            encrypted ? encryptedBuffer : buffer,
+                            receiveSize,
+                            useSelect);
         if (err < 0) {
             Limelog("Video Receive: recvUdpSocket() failed: %d\n", (int)LastSocketError());
             ListenerCallbacks.connectionTerminated(LastSocketFail());
@@ -153,18 +178,33 @@ static void VideoReceiveThreadProc(void* context) {
         }
 #endif
 
-        if (err < (int)sizeof(RTP_PACKET)) {
+        if (err < minSize) {
             // Runt packet
             continue;
         }
 
+        // Decrypt the packet into the buffer if encryption is enabled
+        if (encrypted) {
+            PENC_VIDEO_HEADER encHeader = (PENC_VIDEO_HEADER)encryptedBuffer;
+
+            if (!PltDecryptMessage(decryptionCtx, ALGORITHM_AES_GCM, 0,
+                                   (unsigned char*)StreamConfig.remoteInputAesKey, sizeof(StreamConfig.remoteInputAesKey),
+                                   encHeader->iv, sizeof(encHeader->iv),
+                                   encHeader->tag, sizeof(encHeader->tag),
+                                   ((unsigned char*)(encHeader + 1)), err - sizeof(ENC_VIDEO_HEADER), // The ciphertext is after the header
+                                   (unsigned char*)buffer, &err)) {
+                Limelog("Failed to decrypt video packet!\n");
+                continue;
+            }
+        }
+
         // Convert fields to host byte-order
         packet = (PRTP_PACKET)&buffer[0];
         packet->sequenceNumber = BE16(packet->sequenceNumber);
         packet->timestamp = BE32(packet->timestamp);
         packet->ssrc = BE32(packet->ssrc);
 
-        queueStatus = RtpvAddPacket(&rtpQueue, packet, err, (PRTPV_QUEUE_ENTRY)&buffer[receiveSize]);
+        queueStatus = RtpvAddPacket(&rtpQueue, packet, err, (PRTPV_QUEUE_ENTRY)&buffer[decryptedSize]);
 
         if (queueStatus == RTPF_RET_QUEUED) {
             // The queue owns the buffer
@@ -175,6 +215,10 @@ static void VideoReceiveThreadProc(void* context) {
     if (buffer != NULL) {
         free(buffer);
     }
+
+    if (encryptedBuffer != NULL) {
+        free(encryptedBuffer);
+    }
 }
 
 void notifyKeyFrameReceived(void) {