pc/srtptransport.h

/*
 *  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.
 */

#ifndef WEBRTC_PC_SRTPTRANSPORT_H_
#define WEBRTC_PC_SRTPTRANSPORT_H_

#include <memory>
#include <string>
#include <utility>

#include "webrtc/pc/rtptransportinternal.h"
#include "webrtc/pc/srtpfilter.h"
#include "webrtc/pc/srtpsession.h"
#include "webrtc/rtc_base/checks.h"

namespace webrtc {

// This class will eventually be a wrapper around RtpTransportInternal
// that protects and unprotects sent and received RTP packets.
class SrtpTransport : public RtpTransportInternal {
 public:
  SrtpTransport(bool rtcp_mux_enabled, const std::string& content_name);

  SrtpTransport(std::unique_ptr<RtpTransportInternal> transport,
                const std::string& content_name);

  void SetRtcpMuxEnabled(bool enable) override {
    rtp_transport_->SetRtcpMuxEnabled(enable);
  }

  rtc::PacketTransportInternal* rtp_packet_transport() const override {
    return rtp_transport_->rtp_packet_transport();
  }

  void SetRtpPacketTransport(rtc::PacketTransportInternal* rtp) override {
    rtp_transport_->SetRtpPacketTransport(rtp);
  }

  PacketTransportInterface* GetRtpPacketTransport() const override {
    return rtp_transport_->GetRtpPacketTransport();
  }

  rtc::PacketTransportInternal* rtcp_packet_transport() const override {
    return rtp_transport_->rtcp_packet_transport();
  }
  void SetRtcpPacketTransport(rtc::PacketTransportInternal* rtcp) override {
    rtp_transport_->SetRtcpPacketTransport(rtcp);
  }

  PacketTransportInterface* GetRtcpPacketTransport() const override {
    return rtp_transport_->GetRtcpPacketTransport();
  }

  bool SendRtpPacket(rtc::CopyOnWriteBuffer* packet,
                     const rtc::PacketOptions& options,
                     int flags) override;

  bool SendRtcpPacket(rtc::CopyOnWriteBuffer* packet,
                      const rtc::PacketOptions& options,
                      int flags) override;

  bool IsWritable(bool rtcp) const override {
    return rtp_transport_->IsWritable(rtcp);
  }

  // The transport becomes active if the send_session_ and recv_session_ are
  // created.
  bool IsActive() const;

  bool HandlesPayloadType(int payload_type) const override {
    return rtp_transport_->HandlesPayloadType(payload_type);
  }

  void AddHandledPayloadType(int payload_type) override {
    rtp_transport_->AddHandledPayloadType(payload_type);
  }

  RTCError SetParameters(const RtpTransportParameters& parameters) override {
    return rtp_transport_->SetParameters(parameters);
  }

  RtpTransportParameters GetParameters() const override {
    return rtp_transport_->GetParameters();
  }

  // TODO(zstein): Remove this when we remove RtpTransportAdapter.
  RtpTransportAdapter* GetInternal() override { return nullptr; }

  // Create new send/recv sessions and set the negotiated crypto keys for RTP
  // packet encryption. The keys can either come from SDES negotiation or DTLS
  // handshake.
  bool SetRtpParams(int send_cs,
                    const uint8_t* send_key,
                    int send_key_len,
                    int recv_cs,
                    const uint8_t* recv_key,
                    int recv_key_len);

  // Create new send/recv sessions and set the negotiated crypto keys for RTCP
  // packet encryption. The keys can either come from SDES negotiation or DTLS
  // handshake.
  bool SetRtcpParams(int send_cs,
                     const uint8_t* send_key,
                     int send_key_len,
                     int recv_cs,
                     const uint8_t* recv_key,
                     int recv_key_len);

  void ResetParams();

  // Set the header extension ids that should be encrypted for the given source.
  // This method doesn't immediately update the SRTP session with the new IDs,
  // and you need to call SetRtpParams for that to happen.
  void SetEncryptedHeaderExtensionIds(cricket::ContentSource source,
                                      const std::vector<int>& extension_ids);

  // If external auth is enabled, SRTP will write a dummy auth tag that then
  // later must get replaced before the packet is sent out. Only supported for
  // non-GCM cipher suites and can be checked through "IsExternalAuthActive"
  // if it is actually used. This method is only valid before the RTP params
  // have been set.
  void EnableExternalAuth();
  bool IsExternalAuthEnabled() const;

  // A SrtpTransport supports external creation of the auth tag if a non-GCM
  // cipher is used. This method is only valid after the RTP params have
  // been set.
  bool IsExternalAuthActive() const;

  // Returns srtp overhead for rtp packets.
  bool GetSrtpOverhead(int* srtp_overhead) const;

  // Returns rtp auth params from srtp context.
  bool GetRtpAuthParams(uint8_t** key, int* key_len, int* tag_len);

  // Helper method to get RTP Absoulute SendTime extension header id if
  // present in remote supported extensions list.
  void CacheRtpAbsSendTimeHeaderExtension(int rtp_abs_sendtime_extn_id) {
    rtp_abs_sendtime_extn_id_ = rtp_abs_sendtime_extn_id;
  }

 private:
  void CreateSrtpSessions();

  void ConnectToRtpTransport();

  bool SendPacket(bool rtcp,
                  rtc::CopyOnWriteBuffer* packet,
                  const rtc::PacketOptions& options,
                  int flags);

  void OnPacketReceived(bool rtcp,
                        rtc::CopyOnWriteBuffer* packet,
                        const rtc::PacketTime& packet_time);

  void OnReadyToSend(bool ready) { SignalReadyToSend(ready); }

  bool ProtectRtp(void* data, int in_len, int max_len, int* out_len);

  // Overloaded version, outputs packet index.
  bool ProtectRtp(void* data,
                  int in_len,
                  int max_len,
                  int* out_len,
                  int64_t* index);
  bool ProtectRtcp(void* data, int in_len, int max_len, int* out_len);

  // Decrypts/verifies an invidiual RTP/RTCP packet.
  // If an HMAC is used, this will decrease the packet size.
  bool UnprotectRtp(void* data, int in_len, int* out_len);

  bool UnprotectRtcp(void* data, int in_len, int* out_len);

  const std::string content_name_;
  std::unique_ptr<RtpTransportInternal> rtp_transport_;

  std::unique_ptr<cricket::SrtpSession> send_session_;
  std::unique_ptr<cricket::SrtpSession> recv_session_;
  std::unique_ptr<cricket::SrtpSession> send_rtcp_session_;
  std::unique_ptr<cricket::SrtpSession> recv_rtcp_session_;

  std::vector<int> send_encrypted_header_extension_ids_;
  std::vector<int> recv_encrypted_header_extension_ids_;
  bool external_auth_enabled_ = false;

  int rtp_abs_sendtime_extn_id_ = -1;
};

}  // namespace webrtc

#endif  // WEBRTC_PC_SRTPTRANSPORT_H_