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/*
* Copyright (c) 2018 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 "video/buffered_frame_decryptor.h"
#include <utility>
#include <vector>
#include "modules/rtp_rtcp/source/frame_object.h"
#include "modules/rtp_rtcp/source/rtp_descriptor_authentication.h"
#include "rtc_base/logging.h"
#include "system_wrappers/include/field_trial.h"
namespace webrtc {
BufferedFrameDecryptor::BufferedFrameDecryptor(
OnDecryptedFrameCallback* decrypted_frame_callback,
OnDecryptionStatusChangeCallback* decryption_status_change_callback,
const FieldTrialsView& field_trials)
: generic_descriptor_auth_experiment_(
!field_trials.IsDisabled("WebRTC-GenericDescriptorAuth")),
decrypted_frame_callback_(decrypted_frame_callback),
decryption_status_change_callback_(decryption_status_change_callback) {}
BufferedFrameDecryptor::~BufferedFrameDecryptor() {}
void BufferedFrameDecryptor::SetFrameDecryptor(
rtc::scoped_refptr<FrameDecryptorInterface> frame_decryptor) {
frame_decryptor_ = std::move(frame_decryptor);
}
void BufferedFrameDecryptor::ManageEncryptedFrame(
std::unique_ptr<RtpFrameObject> encrypted_frame) {
switch (DecryptFrame(encrypted_frame.get())) {
case FrameDecision::kStash:
if (stashed_frames_.size() >= kMaxStashedFrames) {
RTC_LOG(LS_WARNING) << "Encrypted frame stash full poping oldest item.";
stashed_frames_.pop_front();
}
stashed_frames_.push_back(std::move(encrypted_frame));
break;
case FrameDecision::kDecrypted:
RetryStashedFrames();
decrypted_frame_callback_->OnDecryptedFrame(std::move(encrypted_frame));
break;
case FrameDecision::kDrop:
break;
}
}
BufferedFrameDecryptor::FrameDecision BufferedFrameDecryptor::DecryptFrame(
RtpFrameObject* frame) {
// Optionally attempt to decrypt the raw video frame if it was provided.
if (frame_decryptor_ == nullptr) {
RTC_LOG(LS_INFO) << "Frame decryption required but not attached to this "
"stream. Stashing frame.";
return FrameDecision::kStash;
}
// Retrieve the maximum possible size of the decrypted payload.
const size_t max_plaintext_byte_size =
frame_decryptor_->GetMaxPlaintextByteSize(cricket::MEDIA_TYPE_VIDEO,
frame->size());
RTC_CHECK_LE(max_plaintext_byte_size, frame->size());
// Place the decrypted frame inline into the existing frame.
rtc::ArrayView<uint8_t> inline_decrypted_bitstream(frame->mutable_data(),
max_plaintext_byte_size);
// Enable authenticating the header if the field trial isn't disabled.
std::vector<uint8_t> additional_data;
if (generic_descriptor_auth_experiment_) {
additional_data = RtpDescriptorAuthentication(frame->GetRtpVideoHeader());
}
// Attempt to decrypt the video frame.
const FrameDecryptorInterface::Result decrypt_result =
frame_decryptor_->Decrypt(cricket::MEDIA_TYPE_VIDEO, /*csrcs=*/{},
additional_data, *frame,
inline_decrypted_bitstream);
// Optionally call the callback if there was a change in status
if (decrypt_result.status != last_status_) {
last_status_ = decrypt_result.status;
decryption_status_change_callback_->OnDecryptionStatusChange(
decrypt_result.status);
}
if (!decrypt_result.IsOk()) {
// Only stash frames if we have never decrypted a frame before.
return first_frame_decrypted_ ? FrameDecision::kDrop
: FrameDecision::kStash;
}
RTC_CHECK_LE(decrypt_result.bytes_written, max_plaintext_byte_size);
// Update the frame to contain just the written bytes.
frame->set_size(decrypt_result.bytes_written);
// Indicate that all future fail to decrypt frames should be dropped.
if (!first_frame_decrypted_) {
first_frame_decrypted_ = true;
}
return FrameDecision::kDecrypted;
}
void BufferedFrameDecryptor::RetryStashedFrames() {
if (!stashed_frames_.empty()) {
RTC_LOG(LS_INFO) << "Retrying stashed encrypted frames. Count: "
<< stashed_frames_.size();
}
for (auto& frame : stashed_frames_) {
if (DecryptFrame(frame.get()) == FrameDecision::kDecrypted) {
decrypted_frame_callback_->OnDecryptedFrame(std::move(frame));
}
}
stashed_frames_.clear();
}
} // namespace webrtc