Created the DtlsSrtpTransport.

pc/dtlssrtptransport.cc

+/*
+ *  Copyright 2017 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "pc/dtlssrtptransport.h"
+
+#include <memory>
+#include <string>
+#include <utility>
+
+#include "media/base/rtputils.h"
+#include "rtc_base/sslstreamadapter.h"
+
+namespace {
+// Value specified in RFC 5764.
+static const char kDtlsSrtpExporterLabel[] = "EXTRACTOR-dtls_srtp";
+}  // namespace
+
+namespace webrtc {
+
+DtlsSrtpTransport::DtlsSrtpTransport(
+    std::unique_ptr<webrtc::SrtpTransport> transport)
+    : srtp_transport_(std::move(transport)) {
+  ConnectToSrtpTransport();
+}
+
+void DtlsSrtpTransport::ConnectToSrtpTransport() {
+  RTC_DCHECK(srtp_transport_);
+  srtp_transport_->SignalPacketReceived.connect(
+      this, &DtlsSrtpTransport::OnPacketReceived);
+  srtp_transport_->SignalReadyToSend.connect(this,
+                                             &DtlsSrtpTransport::OnReadyToSend);
+}
+
+void DtlsSrtpTransport::OnPacketReceived(bool rtcp,
+                                         rtc::CopyOnWriteBuffer* packet,
+                                         const rtc::PacketTime& packet_time) {
+  SignalPacketReceived(rtcp, packet, packet_time);
+}
+
+void DtlsSrtpTransport::OnReadyToSend(bool ready) {
+  SignalReadyToSend(ready);
+}
+
+bool DtlsSrtpTransport::SetupDtlsSrtp(bool rtcp) {
+  bool ret = false;
+
+  cricket::DtlsTransportInternal* transport =
+      rtcp ? rtcp_dtls_transport_ : rtp_dtls_transport_;
+  RTC_DCHECK(transport);
+  RTC_DCHECK(transport->IsDtlsActive());
+
+  int selected_crypto_suite;
+
+  if (!transport->GetSrtpCryptoSuite(&selected_crypto_suite)) {
+    LOG(LS_ERROR) << "No DTLS-SRTP selected crypto suite";
+    return false;
+  }
+
+  LOG(LS_INFO) << "Installing keys from DTLS-SRTP on "
+               << cricket::RtpRtcpStringLiteral(rtcp);
+
+  int key_len;
+  int salt_len;
+  if (!rtc::GetSrtpKeyAndSaltLengths(selected_crypto_suite, &key_len,
+                                     &salt_len)) {
+    LOG(LS_ERROR) << "Unknown DTLS-SRTP crypto suite" << selected_crypto_suite;
+    return false;
+  }
+
+  // OK, we're now doing DTLS (RFC 5764)
+  std::vector<unsigned char> dtls_buffer(key_len * 2 + salt_len * 2);
+
+  // RFC 5705 exporter using the RFC 5764 parameters
+  if (!transport->ExportKeyingMaterial(kDtlsSrtpExporterLabel, NULL, 0, false,
+                                       &dtls_buffer[0], dtls_buffer.size())) {
+    LOG(LS_WARNING) << "DTLS-SRTP key export failed";
+    RTC_NOTREACHED();  // This should never happen
+    return false;
+  }
+
+  // Sync up the keys with the DTLS-SRTP interface
+  std::vector<unsigned char> client_write_key(key_len + salt_len);
+  std::vector<unsigned char> server_write_key(key_len + salt_len);
+  size_t offset = 0;
+  memcpy(&client_write_key[0], &dtls_buffer[offset], key_len);
+  offset += key_len;
+  memcpy(&server_write_key[0], &dtls_buffer[offset], key_len);
+  offset += key_len;
+  memcpy(&client_write_key[key_len], &dtls_buffer[offset], salt_len);
+  offset += salt_len;
+  memcpy(&server_write_key[key_len], &dtls_buffer[offset], salt_len);
+
+  std::vector<unsigned char>*send_key, *recv_key;
+  rtc::SSLRole role;
+  if (!transport->GetSslRole(&role)) {
+    LOG(LS_WARNING) << "GetSslRole failed";
+    return false;
+  }
+
+  if (role == rtc::SSL_SERVER) {
+    send_key = &server_write_key;
+    recv_key = &client_write_key;
+  } else {
+    send_key = &client_write_key;
+    recv_key = &server_write_key;
+  }
+
+  if (rtcp) {
+    if (!IsActive()) {
+      RTC_DCHECK(srtp_transport_);
+      ret = srtp_transport_->SetRtcpParams(
+          selected_crypto_suite, &(*send_key)[0],
+          static_cast<int>(send_key->size()), selected_crypto_suite,
+          &(*recv_key)[0], static_cast<int>(recv_key->size()));
+    } else {
+      // RTCP doesn't need to call SetRtpParam because it is only used
+      // to make the updated encrypted RTP header extension IDs take effect.
+      ret = true;
+    }
+  } else {
+    RTC_DCHECK(srtp_transport_);
+    ret = srtp_transport_->SetRtpParams(selected_crypto_suite, &(*send_key)[0],
+                                        static_cast<int>(send_key->size()),
+                                        selected_crypto_suite, &(*recv_key)[0],
+                                        static_cast<int>(recv_key->size()));
+  }
+
+  if (!ret) {
+    LOG(LS_WARNING) << "DTLS-SRTP key installation failed";
+  }
+  active_ = ret;
+  return ret;
+}
+
+void DtlsSrtpTransport::SetSendEncryptedHeaderExtensionIds(

[Taylor Brandstetter, 2017/09/27 23:54:48]

In a previous code review I mentioned that it may be useful to make an
RtpTransportAdapter helper class, similar to AsyncSocketAdapter. Now that we
have two classes that do this forwarding, it may now be a good time. Could you
at least add a TODO, if you agree?

+    const std::vector<int>& send_extension_ids) {
+  RTC_DCHECK(srtp_transport_);

[Taylor Brandstetter, 2017/09/27 23:54:48]

nit: I don't know if adding these DCHECKS everywhere adds much; the only real
place I'd say it's necessary is the constructor, which doesn't have one.

+  srtp_transport_->SetSendEncryptedHeaderExtensionIds(send_extension_ids);
+}
+
+void DtlsSrtpTransport::SetRecvEncryptedHeaderExtensionIds(
+    const std::vector<int>& recv_extension_ids) {
+  RTC_DCHECK(srtp_transport_);
+  srtp_transport_->SetRecvEncryptedHeaderExtensionIds(recv_extension_ids);
+}
+
+void DtlsSrtpTransport::SetRtcpMuxEnabled(bool enable) {
+  RTC_DCHECK(srtp_transport_);
+  srtp_transport_->SetRtcpMuxEnabled(enable);
+}
+
+rtc::PacketTransportInternal* DtlsSrtpTransport::rtp_packet_transport() const {
+  RTC_DCHECK(srtp_transport_);
+  return srtp_transport_->rtp_packet_transport();
+}
+
+void DtlsSrtpTransport::SetRtpPacketTransport(
+    rtc::PacketTransportInternal* rtp) {
+  RTC_DCHECK(srtp_transport_);
+  srtp_transport_->SetRtpPacketTransport(rtp);
+}
+
+PacketTransportInterface* DtlsSrtpTransport::GetRtpPacketTransport() const {
+  RTC_DCHECK(srtp_transport_);
+  return srtp_transport_->GetRtpPacketTransport();
+}
+
+rtc::PacketTransportInternal* DtlsSrtpTransport::rtcp_packet_transport() const {
+  RTC_DCHECK(srtp_transport_);
+  return srtp_transport_->rtcp_packet_transport();
+}
+
+void DtlsSrtpTransport::SetRtcpPacketTransport(
+    rtc::PacketTransportInternal* rtcp) {
+  RTC_DCHECK(srtp_transport_);
+  srtp_transport_->SetRtcpPacketTransport(rtcp);
+}
+
+PacketTransportInterface* DtlsSrtpTransport::GetRtcpPacketTransport() const {
+  RTC_DCHECK(srtp_transport_);
+  return srtp_transport_->GetRtcpPacketTransport();
+}
+
+bool DtlsSrtpTransport::IsWritable(bool rtcp) const {
+  RTC_DCHECK(srtp_transport_);
+  return srtp_transport_->IsWritable(rtcp);
+}
+
+bool DtlsSrtpTransport::SendRtpPacket(rtc::CopyOnWriteBuffer* packet,
+                                      const rtc::PacketOptions& options,
+                                      int flags) {
+  RTC_DCHECK(srtp_transport_);
+  return srtp_transport_->SendRtpPacket(packet, options, flags);
+}
+
+bool DtlsSrtpTransport::SendRtcpPacket(rtc::CopyOnWriteBuffer* packet,
+                                       const rtc::PacketOptions& options,
+                                       int flags) {
+  RTC_DCHECK(srtp_transport_);
+  return srtp_transport_->SendRtcpPacket(packet, options, flags);
+}
+
+bool DtlsSrtpTransport::HandlesPayloadType(int payload_type) const {
+  RTC_DCHECK(srtp_transport_);
+  return srtp_transport_->HandlesPayloadType(payload_type);
+}
+
+void DtlsSrtpTransport::AddHandledPayloadType(int payload_type) {
+  RTC_DCHECK(srtp_transport_);
+  srtp_transport_->AddHandledPayloadType(payload_type);
+}
+
+void DtlsSrtpTransport::ResetParams() {
+  active_ = false;
+  if (srtp_transport_) {

[Taylor Brandstetter, 2017/09/27 23:54:48]

When will it be null?

+    srtp_transport_->ResetParams();
+  }
+}
+
+RTCError DtlsSrtpTransport::SetParameters(
+    const RtpTransportParameters& parameters) {
+  RTC_DCHECK(srtp_transport_);
+  return srtp_transport_->SetParameters(parameters);
+}
+
+RtpTransportParameters DtlsSrtpTransport::GetParameters() const {
+  RTC_DCHECK(srtp_transport_);
+  return srtp_transport_->GetParameters();
+}
+
+}  // namespace webrtc