1 files changed, 123 insertions, 0 deletions
diff --git a/third_party/libwebrtc/video/buffered_frame_decryptor.cc b/third_party/libwebrtc/video/buffered_frame_decryptor.cc
new file mode 100644
index 0000000000..24cbaf8265
--- /dev/null
+++ b/third_party/libwebrtc/video/buffered_frame_decryptor.cc
@@ -0,0 +1,123 @@
+/*
+ *  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/rtp_descriptor_authentication.h"
+#include "modules/video_coding/frame_object.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