// libpng_read_fuzzer.cc

// Copyright 2017-2018 Glenn Randers-Pehrson

// Copyright 2015 The Chromium Authors. All rights reserved.

// Use of this source code is governed by a BSD-style license that may

// be found in the LICENSE file https://cs.chromium.org/chromium/src/LICENSE

// The modifications in 2017 by Glenn Randers-Pehrson include

// 1. addition of a PNG_CLEANUP macro,

// 2. setting the option to ignore ADLER32 checksums,

// 3. adding "#include <string.h>" which is needed on some platforms

//    to provide memcpy().

// 4. adding read_end_info() and creating an end_info structure.

// 5. adding calls to png_set_*() transforms commonly used by browsers.

#include <stddef.h>

#include <stdint.h>

#include <stdlib.h>

#include <string.h>

#include <vector>

#define PNG_INTERNAL

#include "png.h"

#include "nalloc.h"

#define PNG_CLEANUP \

  nalloc_end(); \

  if(png_handler.png_ptr) \

  { \

    if (png_handler.row_ptr) \

      png_free(png_handler.png_ptr, png_handler.row_ptr); \

    if (png_handler.end_info_ptr) \

      png_destroy_read_struct(&png_handler.png_ptr, &png_handler.info_ptr,\

        &png_handler.end_info_ptr); \

    else if (png_handler.info_ptr) \

      png_destroy_read_struct(&png_handler.png_ptr, &png_handler.info_ptr,\

        nullptr); \

    else \

      png_destroy_read_struct(&png_handler.png_ptr, nullptr, nullptr); \

    png_handler.png_ptr = nullptr; \

    png_handler.row_ptr = nullptr; \

    png_handler.info_ptr = nullptr; \

    png_handler.end_info_ptr = nullptr; \

  }

struct BufState {

  const uint8_t* data;

  size_t bytes_left;

};

struct PngObjectHandler {

  png_infop info_ptr = nullptr;

  png_structp png_ptr = nullptr;

  png_infop end_info_ptr = nullptr;

  png_voidp row_ptr = nullptr;

  BufState* buf_state = nullptr;

  ~PngObjectHandler() {

    if (row_ptr)

      png_free(png_ptr, row_ptr);

    if (end_info_ptr)

      png_destroy_read_struct(&png_ptr, &info_ptr, &end_info_ptr);

    else if (info_ptr)

      png_destroy_read_struct(&png_ptr, &info_ptr, nullptr);

    else

      png_destroy_read_struct(&png_ptr, nullptr, nullptr);

    delete buf_state;

  }

};

void user_read_data(png_structp png_ptr, png_bytep data, size_t length) {

  BufState* buf_state = static_cast<BufState*>(png_get_io_ptr(png_ptr));

  if (length > buf_state->bytes_left) {

    png_error(png_ptr, "read error");

  }

  memcpy(data, buf_state->data, length);

  buf_state->bytes_left -= length;

  buf_state->data += length;

}

void* limited_malloc(png_structp, png_alloc_size_t size) {

  // libpng may allocate large amounts of memory that the fuzzer reports as

  // an error. In order to silence these errors, make libpng fail when trying

  // to allocate a large amount. This allocator used to be in the Chromium

  // version of this fuzzer.

  // This number is chosen to match the default png_user_chunk_malloc_max.

  if (size > 8000000)

    return nullptr;

  return malloc(size);

}

void default_free(png_structp, png_voidp ptr) {

  return free(ptr);

}

static const int kPngHeaderSize = 8;

// Entry point for LibFuzzer.

// Roughly follows the libpng book example:

// http://www.libpng.org/pub/png/book/chapter13.html

extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size) {

  if (size < kPngHeaderSize) {

    return 0;

  }

  nalloc_init(nullptr);

  std::vector<unsigned char> v(data, data + size);

  if (png_sig_cmp(v.data(), 0, kPngHeaderSize)) {

    // not a PNG.

    return 0;

  }

  PngObjectHandler png_handler;

  png_handler.png_ptr = nullptr;

  png_handler.row_ptr = nullptr;

  png_handler.info_ptr = nullptr;

  png_handler.end_info_ptr = nullptr;

  png_handler.png_ptr = png_create_read_struct

    (PNG_LIBPNG_VER_STRING, nullptr, nullptr, nullptr);

  if (!png_handler.png_ptr) {

    return 0;

  }

  nalloc_start(data, size);

  png_handler.info_ptr = png_create_info_struct(png_handler.png_ptr);

  if (!png_handler.info_ptr) {

    PNG_CLEANUP

    return 0;

  }

  png_handler.end_info_ptr = png_create_info_struct(png_handler.png_ptr);

  if (!png_handler.end_info_ptr) {

    PNG_CLEANUP

    return 0;

  }

  // Use a custom allocator that fails for large allocations to avoid OOM.

  png_set_mem_fn(png_handler.png_ptr, nullptr, limited_malloc, default_free);

  png_set_crc_action(png_handler.png_ptr, PNG_CRC_QUIET_USE, PNG_CRC_QUIET_USE);

#ifdef PNG_IGNORE_ADLER32

  png_set_option(png_handler.png_ptr, PNG_IGNORE_ADLER32, PNG_OPTION_ON);

#endif

  // Setting up reading from buffer.

  png_handler.buf_state = new BufState();

  png_handler.buf_state->data = data + kPngHeaderSize;

  png_handler.buf_state->bytes_left = size - kPngHeaderSize;

  png_set_read_fn(png_handler.png_ptr, png_handler.buf_state, user_read_data);

  png_set_sig_bytes(png_handler.png_ptr, kPngHeaderSize);

  if (setjmp(png_jmpbuf(png_handler.png_ptr))) {

    PNG_CLEANUP

    return 0;

  }

  // Reading.

  png_read_info(png_handler.png_ptr, png_handler.info_ptr);

  // reset error handler to put png_deleter into scope.

  if (setjmp(png_jmpbuf(png_handler.png_ptr))) {

    PNG_CLEANUP

    return 0;

  }

  png_uint_32 width, height;

  int bit_depth, color_type, interlace_type, compression_type;

  int filter_type;

  if (!png_get_IHDR(png_handler.png_ptr, png_handler.info_ptr, &width,

                    &height, &bit_depth, &color_type, &interlace_type,

                    &compression_type, &filter_type)) {

    PNG_CLEANUP

    return 0;

  }

  // This is going to be too slow.

  if (width && height > 100000000 / width) {

    PNG_CLEANUP

    return 0;

  }

  // Set several transforms that browsers typically use:

  png_set_gray_to_rgb(png_handler.png_ptr);

  png_set_expand(png_handler.png_ptr);

  png_set_packing(png_handler.png_ptr);

  png_set_scale_16(png_handler.png_ptr);

  png_set_tRNS_to_alpha(png_handler.png_ptr);

  int passes = png_set_interlace_handling(png_handler.png_ptr);

  png_read_update_info(png_handler.png_ptr, png_handler.info_ptr);

  png_handler.row_ptr = png_malloc(

      png_handler.png_ptr, png_get_rowbytes(png_handler.png_ptr,

                                            png_handler.info_ptr));

  for (int pass = 0; pass < passes; ++pass) {

    for (png_uint_32 y = 0; y < height; ++y) {

      png_read_row(png_handler.png_ptr,

                   static_cast<png_bytep>(png_handler.row_ptr), nullptr);

    }

  }

  png_read_end(png_handler.png_ptr, png_handler.end_info_ptr);

  PNG_CLEANUP

#ifdef PNG_SIMPLIFIED_READ_SUPPORTED

  // Simplified READ API

  png_image image;

  memset(&image, 0, (sizeof image));

  image.version = PNG_IMAGE_VERSION;

  if (!png_image_begin_read_from_memory(&image, data, size)) {

    return 0;

  }

  image.format = PNG_FORMAT_RGBA;

  std::vector<png_byte> buffer(PNG_IMAGE_SIZE(image));

  png_image_finish_read(&image, NULL, buffer.data(), 0, NULL);

#endif

  return 0;

}