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///////////////////////////////////////////////////////////////////////////////
//
/// \file fuzz.c
/// \brief Fuzz test program for liblzma
//
// Author: Lasse Collin
//
// This file has been put into the public domain.
// You can do whatever you want with this file.
//
///////////////////////////////////////////////////////////////////////////////
#include <inttypes.h>
#include <stdlib.h>
#include <stdio.h>
#include "lzma.h"
// Output buffer for decompressed data. This is write only; nothing cares
// about the actual data written here.
static uint8_t outbuf[4096];
extern int
LLVMFuzzerTestOneInput(const uint8_t *inbuf, size_t inbuf_size)
{
// Some header values can make liblzma allocate a lot of RAM
// (up to about 4 GiB with liblzma 5.2.x). We set a limit here to
// prevent extreme allocations when fuzzing.
const uint64_t memlimit = 300 << 20; // 300 MiB
// Initialize a .xz decoder using the above memory usage limit.
// Enable support for concatenated .xz files which is used when
// decompressing regular .xz files (instead of data embedded inside
// some other file format). Integrity checks on the uncompressed
// data are ignored to make fuzzing more effective (incorrect check
// values won't prevent the decoder from processing more input).
//
// The flag LZMA_IGNORE_CHECK doesn't disable verification of header
// CRC32 values. Those checks are disabled when liblzma is built
// with the #define FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION.
lzma_stream strm = LZMA_STREAM_INIT;
lzma_ret ret = lzma_stream_decoder(&strm, memlimit,
LZMA_CONCATENATED | LZMA_IGNORE_CHECK);
if (ret != LZMA_OK) {
// This should never happen unless the system has
// no free memory or address space to allow the small
// allocations that the initialization requires.
fprintf(stderr, "lzma_stream_decoder() failed (%d)\n", ret);
abort();
}
// Give the whole input buffer at once to liblzma.
// Output buffer isn't initialized as liblzma only writes to it.
strm.next_in = inbuf;
strm.avail_in = inbuf_size;
strm.next_out = outbuf;
strm.avail_out = sizeof(outbuf);
while ((ret = lzma_code(&strm, LZMA_FINISH)) == LZMA_OK) {
if (strm.avail_out == 0) {
// outbuf became full. We don't care about the
// uncompressed data there, so we simply reuse
// the outbuf and overwrite the old data.
strm.next_out = outbuf;
strm.avail_out = sizeof(outbuf);
}
}
// LZMA_PROG_ERROR should never happen as long as the code calling
// the liblzma functions is correct. Thus LZMA_PROG_ERROR is a sign
// of a bug in either this function or in liblzma.
if (ret == LZMA_PROG_ERROR) {
fprintf(stderr, "lzma_code() returned LZMA_PROG_ERROR\n");
abort();
}
// Free the allocated memory.
lzma_end(&strm);
return 0;
}
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