Add fuzzer for (A)PNG decoder

third_party/WebKit/Source/platform/PngFuzzer.cpp

+// Copyright 2016 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.
+
+// TODO (scroggo): Move this to
+// third_party/WebKit/Source/platform/image-decoders ?
+
+// Compile with:
+// gn gen out/Fuzz '--args=use_libfuzzer=true is_asan=true
+// is_debug=false is_ubsan_security=true' --check
+// ninja -C out/Fuzz blink_png_decoder_fuzzer
+//
+// Run with:
+// ./out/Fuzz/blink_png_decoder_fuzzer
+// third_party/WebKit/LayoutTests/images/resources/pngfuzz
+//
+// Alternatively, it can be run with:
+// ./out/Fuzz/blink_png_decoder_fuzzer ~/another_dir_to_store_corpus
+// third_party/WebKit/LayoutTests/images/resources/pngfuzz
+//
+// so the fuzzer will read both directories passed, but all new generated
+// testcases will go into ~/another_dir_to_store_corpus
+//
+// For more details, see
+// https://chromium.googlesource.com/chromium/src/+/master/testing/libfuzzer/README.md
+
+#include "platform/image-decoders/png/PNGImageDecoder.cpp"
+#include "platform/testing/BlinkFuzzerTestSupport.h"
+
+namespace blink {
+
+std::unique_ptr<ImageDecoder> createDecoder(
+    ImageDecoder::AlphaOption alphaOption) {
+  return WTF::wrapUnique(new PNGImageDecoder(
+      alphaOption, ColorBehavior::transformToTargetForTesting(),
+      ImageDecoder::noDecodedImageByteLimit));
+}
+
+int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size) {
+  auto buffer = SharedBuffer::create(data, size);
+  // TODO (scroggo): Also test ImageDecoder::AlphaNotPremultiplied?
+  auto decoder = createDecoder(ImageDecoder::AlphaPremultiplied);
+  const bool allDataReceived = true;
+  decoder->setData(buffer.get(), allDataReceived);
+  decoder->frameCount();
+  if (decoder->failed())
+    return 0;
+  for (size_t frame = 0; frame < decoder->frameCount(); frame++) {
+    decoder->frameBufferAtIndex(frame);
+    if (decoder->failed())
+      return 0;
+  }
+  return 0;
+}
+
+}  // namespace blink
+
+extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size) {
+  return blink::LLVMFuzzerTestOneInput(data, size);
+}
+
+extern "C" int LLVMFuzzerInitialize(int* argc, char*** argv) {
+  blink::InitializeBlinkFuzzTest(argc, argv);
+  return 0;
+}