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/* A tiny utility for fuzzing bzip3 round-trip compression/decompression.
*
* Prerequisites:
*
* - AFL https://github.com/AFLplusplus/AFLplusplus
* - clang (part of LLVM)
*
* On Arch this is `pacman -S afl++ clang`
*
* # Instructions:
*
* 1. Prepare fuzzer directories
*
* mkdir -p afl_in && mkdir -p afl_out
*
* 2. Insert a test file to afl_in/
*
* cp ./standard_test_files/63_byte_file.bin afl_in/
*
* 3. Build binary (for fuzzing)
*
* afl-clang-fast fuzz-round-trip.c -I../include -o fuzz -g3 "-DVERSION=\"0.0.0\"" -O3 -march=native
*
* 4. Run the fuzzer
*
* AFL_SKIP_CPUFREQ=1 afl-fuzz -i afl_in -o afl_out -- ./fuzz @@
*
* 5. Need to go faster? Multithread.
*
* alacritty -e bash -c "afl-fuzz -i afl_in -o afl_out -M fuzzer01 -- ./fuzz @@; exec bash" &
* alacritty -e bash -c "afl-fuzz -i afl_in -o afl_out -S fuzzer02 -- ./fuzz @@; exec bash" &
* alacritty -e bash -c "afl-fuzz -i afl_in -o afl_out -S fuzzer03 -- ./fuzz @@; exec bash" &
* alacritty -e bash -c "afl-fuzz -i afl_in -o afl_out -S fuzzer04 -- ./fuzz @@; exec bash" &
*
* etc. Replace `alacritty` with your terminal.
*
* 6. For ASAN testing:
*
* export AFL_USE_ASAN=1
* afl-clang-fast fuzz-round-trip.c -I../include -o fuzz -g3 "-DVERSION=\"0.0.0\"" -O3 -march=native
*/
#include "../include/libbz3.h"
#include "../src/libbz3.c"
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <string.h>
#define KiB(x) ((x)*1024)
#define DEFAULT_BLOCK_SIZE KiB(65)
// Required for AFL++ persistent mode
#ifdef __AFL_HAVE_MANUAL_CONTROL
#include <unistd.h>
__AFL_FUZZ_INIT();
#endif
// Function to emulate a crash for diagnostic purposes
static void __attribute__((noreturn)) crash_with_message(const char* msg) {
fprintf(stderr, "Emulating crash: %s\n", msg);
// Use abort() to generate a crash that ASAN and other tools can catch
abort();
}
// Returns 0 on success, crashes on failure
static int try_round_trip(const uint8_t *input_buf, size_t input_len) {
if (input_len == 0) return 0;
// Use the larger of DEFAULT_BLOCK_SIZE or input_len
size_t block_size = input_len > DEFAULT_BLOCK_SIZE ? input_len : DEFAULT_BLOCK_SIZE;
struct bz3_state *state = bz3_new(block_size);
if (!state) {
return -1; // allocation failures not tested.
}
// Allocate buffer for both compression and decompression
// Using block_size to ensure we have enough space for both operations
size_t comp_buf_len = bz3_bound(input_len);
uint8_t *comp_buf = malloc(comp_buf_len);
if (!comp_buf) {
bz3_free(state);
return -1; // allocation failures not tested.
}
// Step 0: Move input to compress buffer
memmove(comp_buf, input_buf, input_len);
// Step 1: Compress the input
int32_t comp_size = bz3_encode_block(state, comp_buf, input_len);
if (comp_size < 0) {
bz3_free(state);
free(comp_buf);
crash_with_message("Compression failed");
}
// Step 2: Decompress
int bzerr = bz3_decode_block(state, comp_buf, comp_buf_len, comp_size, input_len);
if (bzerr < 0 || bzerr != input_len) {
bz3_free(state);
free(comp_buf);
crash_with_message("Decompression failed");
}
// Step 3: Compare
if (memcmp(input_buf, comp_buf, input_len) != 0) {
bz3_free(state);
free(comp_buf);
crash_with_message("Round-trip data mismatch");
}
bz3_free(state);
free(comp_buf);
return 0;
}
static int test_file(const char *filename) {
FILE *fp = fopen(filename, "rb");
if (!fp) {
perror("Failed to open input file");
return 1;
}
fseek(fp, 0, SEEK_END);
size_t size = ftell(fp);
fseek(fp, 0, SEEK_SET);
uint8_t *buffer = malloc(size);
if (!buffer) {
fclose(fp);
crash_with_message("Failed to allocate input buffer");
}
if (fread(buffer, 1, size, fp) != size) {
fclose(fp);
free(buffer);
crash_with_message("Failed to read input file");
}
fclose(fp);
int result = try_round_trip(buffer, size);
free(buffer);
return result;
}
int main(int argc, char **argv) {
#ifdef __AFL_HAVE_MANUAL_CONTROL
__AFL_INIT();
while (__AFL_LOOP(1000)) {
try_round_trip(__AFL_FUZZ_TESTCASE_BUF, __AFL_FUZZ_TESTCASE_LEN);
}
#else
if (argc != 2) {
fprintf(stderr, "Usage: %s <input_file>\n", argv[0]);
return 1;
}
return test_file(argv[1]);
#endif
return 0;
}
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