Avoid unnecessary reallocation of the IV for every packet

src/stream.cpp

@@ -246,16 +246,13 @@ namespace stream {
   // return bytes written on success
   // return -1 on error
   static inline int
-  encode_audio(bool encrypted, const audio::buffer_t &plaintext, audio_packet_t &destination, std::uint32_t avRiKeyIv, crypto::cipher::cbc_t &cbc) {
+  encode_audio(bool encrypted, const audio::buffer_t &plaintext, audio_packet_t &destination, crypto::aes_t &iv, crypto::cipher::cbc_t &cbc) {
     // If encryption isn't enabled
     if (!encrypted) {
       std::copy(std::begin(plaintext), std::end(plaintext), destination->payload());
       return plaintext.size();
     }
 
-    crypto::aes_t iv(16);
-    *(std::uint32_t *) iv.data() = util::endian::big<std::uint32_t>(avRiKeyIv + destination->rtp.sequenceNumber);
-
     return cbc.encrypt(std::string_view { (char *) std::begin(plaintext), plaintext.size() }, destination->payload(), &iv);
   }
 
@@ -401,6 +398,8 @@ namespace stream {
     struct {
       crypto::cipher::gcm_t cipher;
       crypto::aes_t legacy_input_enc_iv;  // Only used when the client doesn't support full control stream encryption
+      crypto::aes_t incoming_iv;
+      crypto::aes_t outgoing_iv;
 
       std::uint32_t connect_data;  // Used for new clients with ML_FF_SESSION_ID_V1
       std::string expected_peer_address;  // Only used for legacy clients without ML_FF_SESSION_ID_V1
@@ -437,7 +436,7 @@ namespace stream {
 
     auto seq = session->control.seq++;
 
-    crypto::aes_t iv;
+    auto &iv = session->control.outgoing_iv;
     if (session->config.encryptionFlagsEnabled & SS_ENC_CONTROL_V2) {
       // We use the deterministic IV construction algorithm specified in NIST SP 800-38D
       // Section 8.2.1. The sequence number is our "invocation" field and the 'CH' in the
@@ -977,7 +976,7 @@ namespace stream {
       std::string_view tagged_cipher { (char *) header->payload(), (size_t) tagged_cipher_length };
 
       auto &cipher = session->control.cipher;
-      crypto::aes_t iv;
+      auto &iv = session->control.incoming_iv;
       if (session->config.encryptionFlagsEnabled & SS_ENC_CONTROL_V2) {
         // We use the deterministic IV construction algorithm specified in NIST SP 800-38D
         // Section 8.2.1. The sequence number is our "invocation" field and the 'CC' in the
@@ -1241,6 +1240,7 @@ namespace stream {
     platf::adjust_thread_priority(platf::thread_priority_e::high);
 
     stat_trackers::min_max_avg_tracker<uint16_t> frame_processing_latency_tracker;
+    crypto::aes_t iv(12);
 
     while (auto packet = packets->pop()) {
       if (shutdown_event->peek()) {
@@ -1413,7 +1413,6 @@ namespace stream {
               //
               // The IV counter is 64 bits long which allows for 2^64 encrypted video packets
               // to be sent to each client before the IV repeats.
-              crypto::aes_t iv(12);
               std::copy_n((uint8_t *) &session->video.gcm_iv_counter, sizeof(session->video.gcm_iv_counter), std::begin(iv));
               iv[11] = 'V';  // Video stream
               session->video.gcm_iv_counter++;
@@ -1486,6 +1485,7 @@ namespace stream {
 
     audio_packet_t audio_packet { (audio_packet_raw_t *) malloc(sizeof(audio_packet_raw_t) + max_block_size) };
     fec::rs_t rs { reed_solomon_new(RTPA_DATA_SHARDS, RTPA_FEC_SHARDS) };
+    crypto::aes_t iv(16);
 
     // For unknown reasons, the RS parity matrix computed by our RS implementation
     // doesn't match the one Nvidia uses for audio data. I'm not exactly sure why,
@@ -1513,11 +1513,9 @@ namespace stream {
       auto sequenceNumber = session->audio.sequenceNumber;
       auto timestamp = session->audio.timestamp;
 
-      // This will be mapped to big-endianness later
+      *(std::uint32_t *) iv.data() = util::endian::big<std::uint32_t>(session->audio.avRiKeyId + sequenceNumber);
-      // For now, encode_audio needs it to be the proper sequenceNumber
-      audio_packet->rtp.sequenceNumber = sequenceNumber;
 
-      auto bytes = encode_audio(session->config.encryptionFlagsEnabled & SS_ENC_AUDIO, packet_data, audio_packet, session->audio.avRiKeyId, session->audio.cipher);
+      auto bytes = encode_audio(session->config.encryptionFlagsEnabled & SS_ENC_AUDIO, packet_data, audio_packet, iv, session->audio.cipher);
       if (bytes < 0) {
         BOOST_LOG(error) << "Couldn't encode audio packet"sv;
         break;