feat(gateway): bind Apollo launch to encrypted session work

gateway/apollo_rtsp.go

@@ -18,10 +18,12 @@ var errEncryptedRTSPFrame = errors.New("invalid encrypted RTSP frame")
 // only strictly increasing host sequence numbers, so a replay cannot be fed
 // into the RTSP parser after it has already authenticated once.
 type encryptedRTSPCodec struct {
-	aead         cipher.AEAD
-	nextClient   uint32
-	lastHost     uint32
-	hostReceived bool
+	aead           cipher.AEAD
+	nextClient     uint32
+	lastClient     uint32
+	clientReceived bool
+	lastHost       uint32
+	hostReceived   bool
 }
 
 func newEncryptedRTSPCodec(key []byte) (*encryptedRTSPCodec, error) {
@@ -54,6 +56,17 @@ func (codec *encryptedRTSPCodec) SealClient(plaintext []byte) ([]byte, error) {
 }
 
 func (codec *encryptedRTSPCodec) OpenHost(frame []byte) ([]byte, error) {
+	return codec.open(frame, 'H', 'R', &codec.lastHost, &codec.hostReceived)
+}
+
+// OpenClient validates the client-originated direction. The native gateway
+// only sends this direction, but retaining the inverse lets a bounded fake
+// provider verify the negotiated session key and frame shape.
+func (codec *encryptedRTSPCodec) OpenClient(frame []byte) ([]byte, error) {
+	return codec.open(frame, 'C', 'R', &codec.lastClient, &codec.clientReceived)
+}
+
+func (codec *encryptedRTSPCodec) open(frame []byte, origin, protocol byte, last *uint32, received *bool) ([]byte, error) {
 	if codec == nil || codec.aead == nil || len(frame) < encryptedRTSPHeaderSize {
 		return nil, errEncryptedRTSPFrame
 	}
@@ -62,10 +75,10 @@ func (codec *encryptedRTSPCodec) OpenHost(frame []byte) ([]byte, error) {
 		return nil, errEncryptedRTSPFrame
 	}
 	sequence := binary.BigEndian.Uint32(frame[4:8])
-	if sequence == 0 || (codec.hostReceived && sequence <= codec.lastHost) {
+	if sequence == 0 || (*received && sequence <= *last) {
 		return nil, errEncryptedRTSPFrame
 	}
-	nonce := encryptedRTSPNonce(sequence, 'H', 'R')
+	nonce := encryptedRTSPNonce(sequence, origin, protocol)
 	sealed := make([]byte, int(length&0x7fffffff)+codec.aead.Overhead())
 	copy(sealed, frame[24:])
 	copy(sealed[length&0x7fffffff:], frame[8:24])
@@ -73,7 +86,7 @@ func (codec *encryptedRTSPCodec) OpenHost(frame []byte) ([]byte, error) {
 	if err != nil {
 		return nil, errEncryptedRTSPFrame
 	}
-	codec.lastHost, codec.hostReceived = sequence, true
+	*last, *received = sequence, true
 	return plaintext, nil
 }