Add a fuzzer for FlexfecReceiver.

Specifically set max_len to 2000, to simulate multi-packet insertions.

BUG=webrtc:5654
NOTRY=true

Review-Url: https://codereview.webrtc.org/2391263002
Cr-Commit-Position: refs/heads/master@{#14656}

webrtc/test/fuzzers/BUILD.gn

@@ -95,6 +95,16 @@ webrtc_fuzzer_test("producer_fec_fuzzer") {
   ]
 }
 
+webrtc_fuzzer_test("flexfec_receiver_fuzzer") {
+  sources = [
+    "flexfec_receiver_fuzzer.cc",
+  ]
+  deps = [
+    "../../modules/rtp_rtcp/",
+  ]
+  libfuzzer_options = [ "max_len=2000" ]
+}
+
 webrtc_fuzzer_test("rtcp_receiver_fuzzer") {
   sources = [
     "rtcp_receiver_fuzzer.cc",

webrtc/test/fuzzers/flexfec_receiver_fuzzer.cc

@@ -0,0 +1,69 @@
+/*
+ *  Copyright (c) 2016 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 <algorithm>
+
+#include "webrtc/base/basictypes.h"
+#include "webrtc/modules/rtp_rtcp/include/rtp_rtcp_defines.h"
+#include "webrtc/modules/rtp_rtcp/include/flexfec_receiver.h"
+#include "webrtc/modules/rtp_rtcp/source/byte_io.h"
+
+namespace webrtc {
+
+namespace {
+class DummyCallback : public RecoveredPacketReceiver {
+  bool OnRecoveredPacket(const uint8_t* packet, size_t length) { return true; }
+};
+}  // namespace
+
+void FuzzOneInput(const uint8_t* data, size_t size) {
+  constexpr size_t kMinDataNeeded = 12;
+  if (size < kMinDataNeeded) {
+    return;
+  }
+
+  uint32_t flexfec_ssrc;
+  memcpy(&flexfec_ssrc, data + 0, 4);
+  uint16_t flexfec_seq_num;
+  memcpy(&flexfec_seq_num, data + 4, 2);
+  uint32_t media_ssrc;
+  memcpy(&media_ssrc, data + 6, 4);
+  uint16_t media_seq_num;
+  memcpy(&media_seq_num, data + 10, 2);
+
+  DummyCallback callback;
+  std::unique_ptr<FlexfecReceiver> receiver =
+      FlexfecReceiver::Create(flexfec_ssrc, media_ssrc, &callback);
+
+  std::unique_ptr<uint8_t[]> packet;
+  size_t packet_length;
+  size_t i = kMinDataNeeded;
+  while (i < size) {
+    packet_length = kRtpHeaderSize + data[i++];
+    packet = std::unique_ptr<uint8_t[]>(new uint8_t[packet_length]);
+    if (i + packet_length >= size) {
+      break;
+    }
+    memcpy(packet.get(), data + i, packet_length);
+    i += packet_length;
+    if (i < size && data[i++] % 2 == 0) {
+      // Simulate FlexFEC packet.
+      ByteWriter<uint16_t>::WriteBigEndian(packet.get() + 2, flexfec_seq_num++);
+      ByteWriter<uint32_t>::WriteBigEndian(packet.get() + 8, flexfec_ssrc);
+    } else {
+      // Simulate media packet.
+      ByteWriter<uint16_t>::WriteBigEndian(packet.get() + 2, media_seq_num++);
+      ByteWriter<uint32_t>::WriteBigEndian(packet.get() + 8, media_ssrc);
+    }
+    receiver->AddAndProcessReceivedPacket(packet.get(), packet_length);
+  }
+}
+
+}  // namespace webrtc