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62 lines
2.3 KiB
62 lines
2.3 KiB
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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// A fuzz target that consumes a Zlib-compressed input.
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// This test verifies that we can find this bug with a custom mutator.
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#include <cstddef>
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#include <cstdint>
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#include <cstdio>
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#include <cstdlib>
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#include <zlib.h>
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// The fuzz target.
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// Uncompress the data, crash on input starting with "FU".
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// Good luck finding this w/o a custom mutator. :)
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extern "C" int LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size) {
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uint8_t Uncompressed[100];
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size_t UncompressedLen = sizeof(Uncompressed);
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if (Z_OK != uncompress(Uncompressed, &UncompressedLen, Data, Size))
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return 0;
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if (UncompressedLen < 2) return 0;
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if (Uncompressed[0] == 'F' && Uncompressed[1] == 'U')
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abort(); // Boom
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return 0;
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}
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#ifdef CUSTOM_MUTATOR
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// Forward-declare the libFuzzer's mutator callback.
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extern "C" size_t
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LLVMFuzzerMutate(uint8_t *Data, size_t Size, size_t MaxSize);
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// The custom mutator:
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// * deserialize the data (in this case, uncompress).
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// * If the data doesn't deserialize, create a properly serialized dummy.
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// * Mutate the deserialized data (in this case, just call LLVMFuzzerMutate).
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// * Serialize the mutated data (in this case, compress).
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extern "C" size_t LLVMFuzzerCustomMutator(uint8_t *Data, size_t Size,
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size_t MaxSize, unsigned int Seed) {
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uint8_t Uncompressed[100];
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size_t UncompressedLen = sizeof(Uncompressed);
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size_t CompressedLen = MaxSize;
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if (Z_OK != uncompress(Uncompressed, &UncompressedLen, Data, Size)) {
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// The data didn't uncompress.
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// So, it's either a broken input and we want to ignore it,
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// or we've started fuzzing from an empty corpus and we need to supply
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// out first properly compressed input.
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uint8_t Dummy[] = {'H', 'i'};
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if (Z_OK != compress(Data, &CompressedLen, Dummy, sizeof(Dummy)))
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return 0;
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// fprintf(stderr, "Dummy: max %zd res %zd\n", MaxSize, CompressedLen);
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return CompressedLen;
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}
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UncompressedLen =
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LLVMFuzzerMutate(Uncompressed, UncompressedLen, sizeof(Uncompressed));
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if (Z_OK != compress(Data, &CompressedLen, Uncompressed, UncompressedLen))
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return 0;
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return CompressedLen;
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}
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#endif // CUSTOM_MUTATOR
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