// 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"
#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;
}
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;
}
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;
}
// 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
return 0;
}
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