[ossfuzz] Improve the fuzzers
* Run more decompression variants * Round trip the compression fuzzer and do partial decompression as well * Add a compression fuzzer that compresses into a smaller output buffer and test the destSize variant These fuzzers caught 2 bugs that were fixed in the previous commit. * Input buffer over-read in partial decompress * Partial decompress fails if output size is 0
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@ -57,3 +57,4 @@ $(LZ4DIR)/liblz4.a:
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.PHONY: clean
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clean: compress_fuzzer_clean decompress_fuzzer_clean
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$(MAKE) -C $(LZ4DIR) clean
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@ -1,25 +1,51 @@
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/**
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* This fuzz target attempts to compress the fuzzed data with the simple
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* compression function with an output buffer that may be too small to
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* ensure that the compressor never crashes.
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*/
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#include <stddef.h>
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#include <stdint.h>
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#include <stdlib.h>
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#include "lz4.h"
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#include <string.h>
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#define CHECK(COND) if (!(COND)) { abort(); }
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#include "fuzz_helpers.h"
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#include "lz4.h"
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int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size)
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{
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size_t const compressed_dest_size = LZ4_compressBound(size);
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char *const dest_buffer = (char *)malloc(compressed_dest_size);
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uint32_t seed = FUZZ_seed(&data, &size);
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size_t const dstCapacity = FUZZ_rand32(&seed, 0, LZ4_compressBound(size));
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char* const dst = (char*)malloc(dstCapacity);
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char* const rt = (char*)malloc(size);
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CHECK(dest_buffer != NULL);
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FUZZ_ASSERT(dst);
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FUZZ_ASSERT(rt);
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// Allocation succeeded, try compressing the incoming data.
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int result = LZ4_compress_default((const char*)data,
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dest_buffer,
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size,
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compressed_dest_size);
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CHECK(result != 0);
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/* If compression succeeds it must round trip correctly. */
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{
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int const dstSize = LZ4_compress_default((const char*)data, dst,
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size, dstCapacity);
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if (dstSize > 0) {
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int const rtSize = LZ4_decompress_safe(dst, rt, dstSize, size);
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FUZZ_ASSERT_MSG(rtSize == size, "Incorrect regenerated size");
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FUZZ_ASSERT_MSG(!memcmp(data, rt, size), "Corruption!");
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}
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}
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free(dest_buffer);
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if (dstCapacity > 0) {
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/* Compression succeeds and must round trip correctly. */
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int compressedSize = size;
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int const dstSize = LZ4_compress_destSize((const char*)data, dst,
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&compressedSize, dstCapacity);
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FUZZ_ASSERT(dstSize > 0);
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int const rtSize = LZ4_decompress_safe(dst, rt, dstSize, size);
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FUZZ_ASSERT_MSG(rtSize == compressedSize, "Incorrect regenerated size");
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FUZZ_ASSERT_MSG(!memcmp(data, rt, compressedSize), "Corruption!");
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}
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return 0;
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free(dst);
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free(rt);
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return 0;
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}
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@ -1,28 +1,58 @@
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/**
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* This fuzz target attempts to decompress the fuzzed data with the simple
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* decompression function to ensure the decompressor never crashes.
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*/
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#include <stddef.h>
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#include <stdint.h>
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#include <stdlib.h>
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#include "lz4.h"
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#include <string.h>
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#define CHECK(COND) if (!(COND)) { abort(); }
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#include "fuzz_helpers.h"
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#include "lz4.h"
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int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size)
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{
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// TODO: Size input buffer pseudo-randomly based on seed extracted from input
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size_t const buffer_size = 10 * 1024 * 1024;
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char *const dest_buffer = (char *)malloc(buffer_size);
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CHECK(dest_buffer != NULL);
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uint32_t seed = FUZZ_seed(&data, &size);
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size_t const dstCapacity = FUZZ_rand32(&seed, 0, 4 * size);
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size_t const smallDictSize = size + 1;
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size_t const largeDictSize = 64 * 1024 - 1;
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size_t const dictSize = MAX(smallDictSize, largeDictSize);
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char* const dst = (char*)malloc(dstCapacity);
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char* const dict = (char*)malloc(dictSize + size);
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char* const largeDict = dict;
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char* const dataAfterDict = dict + dictSize;
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char* const smallDict = dataAfterDict - smallDictSize;
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// Allocation succeeded, try decompressing the incoming data.
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int result = LZ4_decompress_safe((const char*)data,
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dest_buffer,
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size,
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buffer_size);
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FUZZ_ASSERT(dst);
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FUZZ_ASSERT(dict);
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// Ignore the result of decompression.
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(void)result;
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/* Prepare the dictionary. The data doesn't matter for decompression. */
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memset(dict, 0, dictSize);
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memcpy(dataAfterDict, data, size);
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free(dest_buffer);
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/* Decompress using each possible dictionary configuration. */
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/* No dictionary. */
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LZ4_decompress_safe_usingDict((char const*)data, dst, size,
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dstCapacity, NULL, 0);
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/* Small external dictonary. */
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LZ4_decompress_safe_usingDict((char const*)data, dst, size,
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dstCapacity, smallDict, smallDictSize);
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/* Large external dictionary. */
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LZ4_decompress_safe_usingDict((char const*)data, dst, size,
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dstCapacity, largeDict, largeDictSize);
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/* Small prefix. */
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LZ4_decompress_safe_usingDict((char const*)dataAfterDict, dst, size,
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dstCapacity, smallDict, smallDictSize);
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/* Large prefix. */
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LZ4_decompress_safe_usingDict((char const*)data, dst, size,
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dstCapacity, largeDict, largeDictSize);
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/* Partial decompression. */
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LZ4_decompress_safe_partial((char const*)data, dst, size,
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dstCapacity, dstCapacity);
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free(dst);
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free(dict);
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return 0;
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return 0;
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}
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48
ossfuzz/fuzz.h
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48
ossfuzz/fuzz.h
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@ -0,0 +1,48 @@
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/**
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* Fuzz target interface.
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* Fuzz targets have some common parameters passed as macros during compilation.
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* Check the documentation for each individual fuzzer for more parameters.
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*
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* @param FUZZ_RNG_SEED_SIZE:
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* The number of bytes of the source to look at when constructing a seed
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* for the deterministic RNG. These bytes are discarded before passing
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* the data to lz4 functions. Every fuzzer initializes the RNG exactly
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* once before doing anything else, even if it is unused.
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* Default: 4.
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* @param LZ4_DEBUG:
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* This is a parameter for the lz4 library. Defining `LZ4_DEBUG=1`
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* enables assert() statements in the lz4 library. Higher levels enable
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* logging, so aren't recommended. Defining `LZ4_DEBUG=1` is
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* recommended.
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* @param LZ4_FORCE_MEMORY_ACCESS:
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* This flag controls how the zstd library accesses unaligned memory.
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* It can be undefined, or 0 through 2. If it is undefined, it selects
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* the method to use based on the compiler. If testing with UBSAN set
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* MEM_FORCE_MEMORY_ACCESS=0 to use the standard compliant method.
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* @param FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION
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* This is the canonical flag to enable deterministic builds for fuzzing.
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* Changes to zstd for fuzzing are gated behind this define.
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* It is recommended to define this when building zstd for fuzzing.
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*/
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#ifndef FUZZ_H
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#define FUZZ_H
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#ifndef FUZZ_RNG_SEED_SIZE
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# define FUZZ_RNG_SEED_SIZE 4
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#endif
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#include <stddef.h>
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#include <stdint.h>
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#ifdef __cplusplus
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extern "C" {
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#endif
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int LLVMFuzzerTestOneInput(const uint8_t *src, size_t size);
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#ifdef __cplusplus
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}
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#endif
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#endif
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89
ossfuzz/fuzz_helpers.h
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89
ossfuzz/fuzz_helpers.h
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/*
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* Copyright (c) 2016-present, Facebook, Inc.
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* All rights reserved.
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*
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* This source code is licensed under both the BSD-style license (found in the
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* LICENSE file in the root directory of this source tree) and the GPLv2 (found
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* in the COPYING file in the root directory of this source tree).
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*/
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/**
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* Helper functions for fuzzing.
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*/
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#ifndef FUZZ_HELPERS_H
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#define FUZZ_HELPERS_H
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#include "fuzz.h"
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#include "xxhash.h"
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#include <stdint.h>
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#include <stdio.h>
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#include <stdlib.h>
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#ifdef __cplusplus
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extern "C" {
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#endif
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#define MIN(a, b) ((a) < (b) ? (a) : (b))
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#define MAX(a, b) ((a) > (b) ? (a) : (b))
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#define FUZZ_QUOTE_IMPL(str) #str
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#define FUZZ_QUOTE(str) FUZZ_QUOTE_IMPL(str)
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/**
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* Asserts for fuzzing that are always enabled.
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*/
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#define FUZZ_ASSERT_MSG(cond, msg) \
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((cond) ? (void)0 \
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: (fprintf(stderr, "%s: %u: Assertion: `%s' failed. %s\n", __FILE__, \
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__LINE__, FUZZ_QUOTE(cond), (msg)), \
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abort()))
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#define FUZZ_ASSERT(cond) FUZZ_ASSERT_MSG((cond), "");
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#if defined(__GNUC__)
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#define FUZZ_STATIC static __inline __attribute__((unused))
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#elif defined(__cplusplus) || \
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(defined(__STDC_VERSION__) && (__STDC_VERSION__ >= 199901L) /* C99 */)
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#define FUZZ_STATIC static inline
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#elif defined(_MSC_VER)
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#define FUZZ_STATIC static __inline
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#else
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#define FUZZ_STATIC static
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#endif
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/**
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* Deterministically constructs a seed based on the fuzz input.
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* Consumes up to the first FUZZ_RNG_SEED_SIZE bytes of the input.
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*/
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FUZZ_STATIC uint32_t FUZZ_seed(uint8_t const **src, size_t* size) {
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uint8_t const *data = *src;
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size_t const toHash = MIN(FUZZ_RNG_SEED_SIZE, *size);
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*size -= toHash;
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*src += toHash;
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return XXH32(data, toHash, 0);
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}
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#define FUZZ_rotl32(x, r) (((x) << (r)) | ((x) >> (32 - (r))))
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FUZZ_STATIC uint32_t FUZZ_rand(uint32_t *state) {
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static const uint32_t prime1 = 2654435761U;
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static const uint32_t prime2 = 2246822519U;
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uint32_t rand32 = *state;
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rand32 *= prime1;
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rand32 += prime2;
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rand32 = FUZZ_rotl32(rand32, 13);
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*state = rand32;
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return rand32 >> 5;
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}
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/* Returns a random numer in the range [min, max]. */
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FUZZ_STATIC uint32_t FUZZ_rand32(uint32_t *state, uint32_t min, uint32_t max) {
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uint32_t random = FUZZ_rand(state);
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return min + (random % (max - min + 1));
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}
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#ifdef __cplusplus
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}
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#endif
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#endif
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50
ossfuzz/round_trip_fuzzer.c
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50
ossfuzz/round_trip_fuzzer.c
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/**
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* This fuzz target performs a lz4 round-trip test (compress & decompress),
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* compares the result with the original, and calls abort() on corruption.
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*/
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#include <stddef.h>
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#include <stdint.h>
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#include <stdlib.h>
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#include <string.h>
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#include "fuzz_helpers.h"
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#include "lz4.h"
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int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size)
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{
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uint32_t seed = FUZZ_seed(&data, &size);
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size_t const dstCapacity = LZ4_compressBound(size);
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char* const dst = (char*)malloc(dstCapacity);
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char* const rt = (char*)malloc(size);
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FUZZ_ASSERT(dst);
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FUZZ_ASSERT(rt);
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/* Compression must succeed and round trip correctly. */
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int const dstSize = LZ4_compress_default((const char*)data, dst,
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size, dstCapacity);
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FUZZ_ASSERT(dstSize > 0);
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int const rtSize = LZ4_decompress_safe(dst, rt, dstSize, size);
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FUZZ_ASSERT_MSG(rtSize == size, "Incorrect size");
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FUZZ_ASSERT_MSG(!memcmp(data, rt, size), "Corruption!");
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/* Partial decompression must succeed. */
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{
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size_t const partialCapacity = FUZZ_rand32(&seed, 0, size);
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char* const partial = (char*)malloc(partialCapacity);
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FUZZ_ASSERT(partial);
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int const partialSize = LZ4_decompress_safe_partial(
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dst, partial, dstSize, partialCapacity, partialCapacity);
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FUZZ_ASSERT(partialSize >= 0);
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FUZZ_ASSERT_MSG(partialSize == partialCapacity, "Incorrect size");
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FUZZ_ASSERT_MSG(!memcmp(data, partial, partialSize), "Corruption!");
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free(partial);
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}
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free(dst);
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free(rt);
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return 0;
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}
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#include <stdio.h>
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#include <stdlib.h>
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#include "testinput.h"
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#include "fuzz.h"
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/**
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* Main procedure for standalone fuzzing engine.
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#ifndef TESTINPUT_H_INCLUDED
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#define TESTINPUT_H_INCLUDED
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#include <inttypes.h>
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#if defined (__cplusplus)
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extern "C" {
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#endif
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int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size);
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#if defined(__cplusplus)
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}
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#endif
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#endif
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