1 /*
2  *  Copyright 2018 The WebRTC project authors. All Rights Reserved.
3  *
4  *  Use of this source code is governed by a BSD-style license
5  *  that can be found in the LICENSE file in the root of the source
6  *  tree. An additional intellectual property rights grant can be found
7  *  in the file PATENTS.  All contributing project authors may
8  *  be found in the AUTHORS file in the root of the source tree.
9  */
10 
11 #ifndef API_CRYPTO_FRAME_DECRYPTOR_INTERFACE_H_
12 #define API_CRYPTO_FRAME_DECRYPTOR_INTERFACE_H_
13 
14 #include <vector>
15 
16 #include "api/array_view.h"
17 #include "api/media_types.h"
18 #include "rtc_base/ref_count.h"
19 
20 namespace webrtc {
21 
22 // FrameDecryptorInterface allows users to provide a custom decryption
23 // implementation for all incoming audio and video frames. The user must also
24 // provide a FrameEncryptorInterface to be able to encrypt the frames being
25 // sent out of the device. Note this is an additional layer of encyrption in
26 // addition to the standard SRTP mechanism and is not intended to be used
27 // without it. You may assume that this interface will have the same lifetime
28 // as the RTPReceiver it is attached to. It must only be attached to one
29 // RTPReceiver. Additional data may be null.
30 // Note: This interface is not ready for production use.
31 class FrameDecryptorInterface : public rtc::RefCountInterface {
32  public:
33   // The Status enum represents all possible states that can be
34   // returned when attempting to decrypt a frame. kRecoverable indicates that
35   // there was an error with the given frame and so it should not be passed to
36   // the decoder, however it hints that the receive stream is still decryptable
37   // which is important for determining when to send key frame requests
38   // kUnknown should never be returned by the implementor.
39   enum class Status { kOk, kRecoverable, kFailedToDecrypt, kUnknown };
40 
41   struct Result {
ResultResult42     Result(Status status, size_t bytes_written)
43         : status(status), bytes_written(bytes_written) {}
44 
IsOkResult45     bool IsOk() const { return status == Status::kOk; }
46 
47     const Status status;
48     const size_t bytes_written;
49   };
50 
~FrameDecryptorInterface()51   ~FrameDecryptorInterface() override {}
52 
53   // Attempts to decrypt the encrypted frame. You may assume the frame size will
54   // be allocated to the size returned from GetMaxPlaintextSize. You may assume
55   // that the frames are in order if SRTP is enabled. The stream is not provided
56   // here and it is up to the implementor to transport this information to the
57   // receiver if they care about it. You must set bytes_written to how many
58   // bytes you wrote to in the frame buffer. kOk must be returned if successful,
59   // kRecoverable should be returned if the failure was due to something other
60   // than a decryption failure. kFailedToDecrypt should be returned in all other
61   // cases.
62   virtual Result Decrypt(cricket::MediaType media_type,
63                          const std::vector<uint32_t>& csrcs,
64                          rtc::ArrayView<const uint8_t> additional_data,
65                          rtc::ArrayView<const uint8_t> encrypted_frame,
66                          rtc::ArrayView<uint8_t> frame) = 0;
67 
68   // Returns the total required length in bytes for the output of the
69   // decryption. This can be larger than the actual number of bytes you need but
70   // must never be smaller as it informs the size of the frame buffer.
71   virtual size_t GetMaxPlaintextByteSize(cricket::MediaType media_type,
72                                          size_t encrypted_frame_size) = 0;
73 };
74 
75 }  // namespace webrtc
76 
77 #endif  // API_CRYPTO_FRAME_DECRYPTOR_INTERFACE_H_
78