Prevent depacketizer OOB reads on zero-length VP8 payload.

webrtc/modules/rtp_rtcp/source/rtp_format_vp8.cc

 /*
  *  Copyright (c) 2011 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.
  */
 
@@ skipping 650 matching lines @@
 //       0 1 2 3 4 5 6 7
 //      +-+-+-+-+-+-+-+-+
 //      |Size0|H| VER |P|
 //      +-+-+-+-+-+-+-+-+
 //      |      ...      |
 //      +               +
 bool RtpDepacketizerVp8::Parse(ParsedPayload* parsed_payload,
                                const uint8_t* payload_data,
                                size_t payload_data_length) {
   assert(parsed_payload != NULL);
+  if (payload_data_length == 0) {
+    LOG(LS_ERROR) << "Empty payload.";
+    return false;
+  }
 
   // Parse mandatory first byte of payload descriptor.
   bool extension = (*payload_data & 0x80) ? true : false;               // X bit
   bool beginning_of_partition = (*payload_data & 0x10) ? true : false;  // S bit
   int partition_id = (*payload_data & 0x0F);  // PartID field
 
   parsed_payload->type.Video.width = 0;
   parsed_payload->type.Video.height = 0;
   parsed_payload->type.Video.isFirstPacket =
       beginning_of_partition && (partition_id == 0);
@@ skipping 49 matching lines @@
   if (ParseVP8FrameSize(parsed_payload, payload_data, payload_data_length) !=
       0) {
     return false;
   }
 
   parsed_payload->payload = payload_data;
   parsed_payload->payload_length = payload_data_length;
   return true;
 }
 }  // namespace webrtc