Fix NACK messages corruption

Author: paullouisageneau

include/rtc/message.hpp

@@ -59,6 +59,8 @@ RTC_CPP_EXPORT message_ptr make_message(binary &&data, Message::Type type = Mess
                                         unsigned int stream = 0,
                                         shared_ptr<Reliability> reliability = nullptr);
 
+RTC_CPP_EXPORT message_ptr make_message(size_t size, message_ptr orig);
+
 RTC_CPP_EXPORT message_ptr make_message(message_variant data);
 
 #if RTC_ENABLE_MEDIA

src/impl/dtlssrtptransport.cpp

@@ -104,7 +104,8 @@ bool DtlsSrtpTransport::sendMedia(message_ptr message) {
 
 	// srtp_protect() and srtp_protect_rtcp() assume that they can write SRTP_MAX_TRAILER_LEN (for
 	// the authentication tag) into the location in memory immediately following the RTP packet.
-	message->resize(size + SRTP_MAX_TRAILER_LEN);
+	// Copy instead of resizing so we don't interfere with media handlers keeping references
+	message = make_message(message->size() + SRTP_MAX_TRAILER_LEN, message);
 
 	if (IsRtcp(*message)) { // Demultiplex RTCP and RTP using payload type
 		if (srtp_err_status_t err = srtp_protect_rtcp(mSrtpOut, message->data(), &size)) {

src/message.cpp

@@ -26,6 +26,17 @@ message_ptr make_message(binary &&data, Message::Type type, unsigned int stream,
 	return message;
 }
 
+message_ptr make_message(size_t size, message_ptr orig) {
+	if(!orig)
+		return nullptr;
+
+	auto message = std::make_shared<Message>(size, orig->type);
+	std::copy(orig->begin(), std::min(orig->end(), orig->begin() + size), message->begin());
+	message->stream = orig->stream;
+	message->reliability = orig->reliability;
+	return message;
+}
+
 message_ptr make_message(message_variant data) {
 	return std::visit( //
 	    overloaded{