Support for parsing encrypted WebM streams by src.

media/filters/ffmpeg_demuxer.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "media/filters/ffmpeg_demuxer.h"
 
 #include <algorithm>
 #include <string>
 
+#include "base/base64.h"
 #include "base/bind.h"
 #include "base/callback.h"
 #include "base/callback_helpers.h"
 #include "base/command_line.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/message_loop.h"
 #include "base/stl_util.h"
 #include "base/string_util.h"
 #include "base/task_runner_util.h"
 #include "base/time.h"
 #include "media/base/audio_decoder_config.h"
 #include "media/base/bind_to_loop.h"
 #include "media/base/decoder_buffer.h"
+#include "media/base/decrypt_config.h"
 #include "media/base/limits.h"
 #include "media/base/media_switches.h"
 #include "media/base/video_decoder_config.h"
 #include "media/ffmpeg/ffmpeg_common.h"
 #include "media/filters/ffmpeg_glue.h"
 #include "media/filters/ffmpeg_h264_to_annex_b_bitstream_converter.h"
+#include "media/webm/webm_crypto_helpers.h"
 
 namespace media {
 
 //
 // FFmpegDemuxerStream
 //
 FFmpegDemuxerStream::FFmpegDemuxerStream(
     FFmpegDemuxer* demuxer,
     AVStream* stream)
     : demuxer_(demuxer),
       message_loop_(base::MessageLoopProxy::current()),
       stream_(stream),
       type_(UNKNOWN),
       stopped_(false),
       end_of_stream_(false),
       last_packet_timestamp_(kNoTimestamp()),
       bitstream_converter_enabled_(false) {
   DCHECK(demuxer_);
 
+  bool is_encrypted = false;
+
   // Determine our media format.
   switch (stream->codec->codec_type) {
     case AVMEDIA_TYPE_AUDIO:
       type_ = AUDIO;
-      AVCodecContextToAudioDecoderConfig(stream->codec, &audio_config_);
+      AVStreamToAudioDecoderConfig(stream, &audio_config_);
+      is_encrypted = audio_config_.is_encrypted();
       break;
     case AVMEDIA_TYPE_VIDEO:
       type_ = VIDEO;
       AVStreamToVideoDecoderConfig(stream, &video_config_);
+      is_encrypted = video_config_.is_encrypted();
       break;
     default:
       NOTREACHED();
       break;
   }
 
   // Calculate the duration.
   duration_ = ConvertStreamTimestamp(stream->time_base, stream->duration);
 
   if (stream_->codec->codec_id == CODEC_ID_H264) {
     bitstream_converter_.reset(
         new FFmpegH264ToAnnexBBitstreamConverter(stream_->codec));
   }
+
+  if (is_encrypted) {
+    AVDictionaryEntry* key = av_dict_get(stream->metadata, "enc_key_id", NULL,
+                                         0);
+    DCHECK(key);
+    DCHECK(key->value);
+    if (!key || !key->value)
+      return;
+    base::StringPiece base64_key_id(key->value);
+    std::string enc_key_id;
+    base::Base64Decode(base64_key_id, &enc_key_id);
+    DCHECK(!enc_key_id.empty());
+    if (enc_key_id.empty())
+      return;
+
+    encryption_key_id_.assign(enc_key_id);
+    demuxer_->FireNeedKey(kWebMEncryptInitDataType, enc_key_id);
+  }
 }
 
 void FFmpegDemuxerStream::EnqueuePacket(ScopedAVPacket packet) {
   DCHECK(message_loop_->BelongsToCurrentThread());
 
   if (stopped_ || end_of_stream_) {
     NOTREACHED() << "Attempted to enqueue packet on a stopped stream";
     return;
   }
 
   // Convert the packet if there is a bitstream filter.
   if (packet->data && bitstream_converter_enabled_ &&
       !bitstream_converter_->ConvertPacket(packet.get())) {
     LOG(ERROR) << "Format conversion failed.";
   }
 
   // If a packet is returned by FFmpeg's av_parser_parse2() the packet will
   // reference inner memory of FFmpeg.  As such we should transfer the packet
   // into memory we control.
   scoped_refptr<DecoderBuffer> buffer;
   buffer = DecoderBuffer::CopyFrom(packet->data, packet->size);
+
+  if ((type() == DemuxerStream::AUDIO && audio_config_.is_encrypted()) ||
+      (type() == DemuxerStream::VIDEO && video_config_.is_encrypted())) {
+    buffer->SetDecryptConfig(WebMCreateDecryptConfig(
+         packet->data, packet->size,
+         reinterpret_cast<const uint8*>(encryption_key_id_.data()),
+         encryption_key_id_.size()));
+    CHECK(buffer->GetDecryptConfig()) << "Create DecryptConfig failed.";

[ddorwin, 2013/03/12 04:40:06]

How can this happen? Should it really be a check (with string) in opt builds?

[fgalligan1, 2013/03/12 17:20:13]

This could happen is the encrypted Block is malformed. E.g. A zero length frame
(missing the signal byte). Or an encrypted frame that has length less than 9
bytes (A corrupted IV). I added 2 tests to check this code in chunk demuxer.
Should I just let this type of error propagate and let the decode fail?

[ddorwin, 2013/03/12 19:31:01]

I think so. If "user input" (media) can cause it, we should not crash.

[fgalligan1, 2013/03/13 17:58:09]

Changed to DCHECK. Good?

+  }
+
   buffer->SetTimestamp(ConvertStreamTimestamp(
       stream_->time_base, packet->pts));
   buffer->SetDuration(ConvertStreamTimestamp(
       stream_->time_base, packet->duration));
   if (buffer->GetTimestamp() != kNoTimestamp() &&
       last_packet_timestamp_ != kNoTimestamp() &&
       last_packet_timestamp_ < buffer->GetTimestamp()) {
     buffered_ranges_.Add(last_packet_timestamp_, buffer->GetTimestamp());
     demuxer_->NotifyBufferingChanged();
   }
@@ skipping 123 matching lines @@
     return kNoTimestamp();
 
   return ConvertFromTimeBase(time_base, timestamp);
 }
 
 //
 // FFmpegDemuxer
 //
 FFmpegDemuxer::FFmpegDemuxer(
     const scoped_refptr<base::MessageLoopProxy>& message_loop,
-    const scoped_refptr<DataSource>& data_source)
+    const scoped_refptr<DataSource>& data_source,
+    const FFmpegNeedKeyCB& need_key_cb)
     : host_(NULL),
       message_loop_(message_loop),
       blocking_thread_("FFmpegDemuxer"),
       pending_read_(false),
       pending_seek_(false),
       data_source_(data_source),
       bitrate_(0),
       start_time_(kNoTimestamp()),
       audio_disabled_(false),
       duration_known_(false),
       url_protocol_(data_source, BindToLoop(message_loop_, base::Bind(
-          &FFmpegDemuxer::OnDataSourceError, base::Unretained(this)))) {
+          &FFmpegDemuxer::OnDataSourceError, base::Unretained(this)))),
+      need_key_cb_(need_key_cb) {
   DCHECK(message_loop_);
   DCHECK(data_source_);
 }
 
 FFmpegDemuxer::~FFmpegDemuxer() {}
 
 void FFmpegDemuxer::Stop(const base::Closure& callback) {
   DCHECK(message_loop_->BelongsToCurrentThread());
   url_protocol_.Abort();
   data_source_->Stop(BindToCurrentLoop(base::Bind(
@@ skipping 397 matching lines @@
   StreamVector::iterator iter;
   for (iter = streams_.begin(); iter != streams_.end(); ++iter) {
     if (!*iter ||
         (audio_disabled_ && (*iter)->type() == DemuxerStream::AUDIO)) {
       continue;
     }
     (*iter)->SetEndOfStream();
   }
 }
 
+void FFmpegDemuxer::FireNeedKey(const std::string& init_data_type,
+                                const std::string& encryption_key_id) {
+  int key_id_size = encryption_key_id.size();
+  scoped_array<uint8> key_id_local(new uint8[key_id_size]);
+  memcpy(key_id_local.get(), encryption_key_id.data(), key_id_size);
+  need_key_cb_.Run(init_data_type, key_id_local.Pass(), key_id_size);
+}
+
 void FFmpegDemuxer::NotifyCapacityAvailable() {
   DCHECK(message_loop_->BelongsToCurrentThread());
   ReadFrameIfNeeded();
 }
 
 void FFmpegDemuxer::NotifyBufferingChanged() {
   DCHECK(message_loop_->BelongsToCurrentThread());
   Ranges<base::TimeDelta> buffered;
   scoped_refptr<FFmpegDemuxerStream> audio =
       audio_disabled_ ? NULL : GetFFmpegStream(DemuxerStream::AUDIO);
   scoped_refptr<FFmpegDemuxerStream> video =
       GetFFmpegStream(DemuxerStream::VIDEO);
   if (audio && video) {
     buffered = audio->GetBufferedRanges().IntersectionWith(
         video->GetBufferedRanges());
   } else if (audio) {
     buffered = audio->GetBufferedRanges();
   } else if (video) {
     buffered = video->GetBufferedRanges();
   }
   for (size_t i = 0; i < buffered.size(); ++i)
     host_->AddBufferedTimeRange(buffered.start(i), buffered.end(i));
 }
 
 void FFmpegDemuxer::OnDataSourceError() {
   host_->OnDemuxerError(PIPELINE_ERROR_READ);
 }
 
 }  // namespace media