srtp_session.h - mozsearch

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/*

 *  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 PC_SRTP_SESSION_H_

#define PC_SRTP_SESSION_H_

#include <stddef.h>

#include <stdint.h>

#include <vector>

#include "api/field_trials_view.h"

#include "api/scoped_refptr.h"

#include "api/sequence_checker.h"

#include "rtc_base/synchronization/mutex.h"

// Forward declaration to avoid pulling in libsrtp headers here

struct srtp_event_data_t;

struct srtp_ctx_t_;

namespace cricket {

// Prohibits webrtc from initializing libsrtp. This can be used if libsrtp is

// initialized by another library or explicitly. Note that this must be called

// before creating an SRTP session with WebRTC.

void ProhibitLibsrtpInitialization();

// Class that wraps a libSRTP session.

class SrtpSession {

 public:

  SrtpSession();

  explicit SrtpSession(const webrtc::FieldTrialsView& field_trials);

  ~SrtpSession();

  SrtpSession(const SrtpSession&) = delete;

  SrtpSession& operator=(const SrtpSession&) = delete;

  // Configures the session for sending data using the specified

  // crypto suite and key. Receiving must be done by a separate session.

  bool SetSend(int crypto_suite,

               const uint8_t* key,

               size_t len,

               const std::vector<int>& extension_ids);

  bool UpdateSend(int crypto_suite,

                  const uint8_t* key,

                  size_t len,

                  const std::vector<int>& extension_ids);

  // Configures the session for receiving data using the specified

  // crypto suite and key. Sending must be done by a separate session.

  bool SetRecv(int crypto_suite,

               const uint8_t* key,

               size_t len,

               const std::vector<int>& extension_ids);

  bool UpdateRecv(int crypto_suite,

                  const uint8_t* key,

                  size_t len,

                  const std::vector<int>& extension_ids);

  // Encrypts/signs an individual RTP/RTCP packet, in-place.

  // If an HMAC is used, this will increase the packet size.

  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);

  // Helper method to get authentication params.

  bool GetRtpAuthParams(uint8_t** key, int* key_len, int* tag_len);

  int GetSrtpOverhead() const;

  // 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 SRTP session 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;

  // Removes a SSRC from the underlying libSRTP session.

  // Note: this should only be done for SSRCs that are received.

  // Removing SSRCs that were sent and then reusing them leads to

  // cryptographic weaknesses described in

  // https://www.rfc-editor.org/rfc/rfc3711#section-8

  // https://www.rfc-editor.org/rfc/rfc7714#section-8.4

  bool RemoveSsrcFromSession(uint32_t ssrc);

 private:

  bool DoSetKey(int type,

                int crypto_suite,

                const uint8_t* key,

                size_t len,

                const std::vector<int>& extension_ids);

  bool SetKey(int type,

              int crypto_suite,

              const uint8_t* key,

              size_t len,

              const std::vector<int>& extension_ids);

  bool UpdateKey(int type,

                 int crypto_suite,

                 const uint8_t* key,

                 size_t len,

                 const std::vector<int>& extension_ids);

  // Returns send stream current packet index from srtp db.

  bool GetSendStreamPacketIndex(void* data, int in_len, int64_t* index);

  // Writes unencrypted packets in text2pcap format to the log file

  // for debugging.

  void DumpPacket(const void* buf, int len, bool outbound);

  void HandleEvent(const srtp_event_data_t* ev);

  static void HandleEventThunk(srtp_event_data_t* ev);

  webrtc::SequenceChecker thread_checker_;

  srtp_ctx_t_* session_ = nullptr;

  // Overhead of the SRTP auth tag for RTP and RTCP in bytes.

  // Depends on the cipher suite used and is usually the same with the exception

  // of the kCsAesCm128HmacSha1_32 cipher suite. The additional four bytes

  // required for RTCP protection are not included.

  int rtp_auth_tag_len_ = 0;

  int rtcp_auth_tag_len_ = 0;

  bool inited_ = false;

  int last_send_seq_num_ = -1;

  bool external_auth_active_ = false;

  bool external_auth_enabled_ = false;

  int decryption_failure_count_ = 0;

  bool dump_plain_rtp_ = false;

};

}  // namespace cricket

#endif  // PC_SRTP_SESSION_H_