harness.cc

// 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

// Last changed in libpng 1.6.35 [July 15, 2018]

// 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 <string.h>

#include <vector>

#define PNG_INTERNAL
#include "png.h"

#define PNG_CLEANUP                                                        \
  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;
}

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; }

  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; }

  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;
  }

  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
#ifdef HAS_DUMMY_CRASH
  #ifdef __aarch64__
    asm volatile(".word 0xf7f0a000\n");
  #else
    asm("ud2");
  #endif
#endif
    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
  return 0;
}