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afl-tmin.c
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afl-tmin.c
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/*
american fuzzy lop - test case minimizer
----------------------------------------
Written and maintained by Michal Zalewski <[email protected]>
Copyright 2015, 2016, 2017 Google Inc. All rights reserved.
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at:
http://www.apache.org/licenses/LICENSE-2.0
A simple test case minimizer that takes an input file and tries to remove
as much data as possible while keeping the binary in a crashing state
*or* producing consistent instrumentation output (the mode is auto-selected
based on the initially observed behavior).
*/
#define AFL_MAIN
#include "config.h"
#include "types.h"
#include "debug.h"
#include "alloc-inl.h"
#include "hash.h"
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <errno.h>
#include <signal.h>
#include <dirent.h>
#include <fcntl.h>
#include <sys/wait.h>
#include <sys/time.h>
#include <sys/shm.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/resource.h>
static s32 forksrv_pid, /* PID of the fork server */
child_pid; /* PID of the tested program */
static s32 fsrv_ctl_fd, /* Fork server control pipe (write) */
fsrv_st_fd; /* Fork server status pipe (read) */
static u8 *trace_bits, /* SHM with instrumentation bitmap */
*mask_bitmap; /* Mask for trace bits (-B) */
static u8 *in_file, /* Minimizer input test case */
*out_file, /* Minimizer output file */
*prog_in, /* Targeted program input file */
*target_path, /* Path to target binary */
*doc_path; /* Path to docs */
static s32 prog_in_fd; /* Persistent fd for prog_in */
static u8* in_data; /* Input data for trimming */
static u8 qemu_mode = 0; /* Running in QEMU mode? */
static u32 in_len, /* Input data length */
orig_cksum, /* Original checksum */
total_execs, /* Total number of execs */
missed_hangs, /* Misses due to hangs */
missed_crashes, /* Misses due to crashes */
missed_paths, /* Misses due to exec path diffs */
exec_tmout = EXEC_TIMEOUT; /* Exec timeout (ms) */
static u64 mem_limit = MEM_LIMIT; /* Memory limit (MB) */
static s32 shm_id, /* ID of the SHM region */
dev_null_fd = -1; /* FD to /dev/null */
static u8 crash_mode, /* Crash-centric mode? */
exit_crash, /* Treat non-zero exit as crash? */
edges_only, /* Ignore hit counts? */
exact_mode, /* Require path match for crashes? */
use_stdin = 1; /* Use stdin for program input? */
static volatile u8
stop_soon, /* Ctrl-C pressed? */
child_timed_out; /* Child timed out? */
/* Classify tuple counts. This is a slow & naive version, but good enough here. */
static const u8 count_class_lookup[256] = {
[0] = 0,
[1] = 1,
[2] = 2,
[3] = 4,
[4 ... 7] = 8,
[8 ... 15] = 16,
[16 ... 31] = 32,
[32 ... 127] = 64,
[128 ... 255] = 128
};
static void classify_counts(u8* mem) {
u32 i = MAP_SIZE;
if (edges_only) {
while (i--) {
if (*mem) *mem = 1;
mem++;
}
} else {
while (i--) {
*mem = count_class_lookup[*mem];
mem++;
}
}
}
/* Apply mask to classified bitmap (if set). */
static void apply_mask(u32* mem, u32* mask) {
u32 i = (MAP_SIZE >> 2);
if (!mask) return;
while (i--) {
*mem &= ~*mask;
mem++;
mask++;
}
}
/* See if any bytes are set in the bitmap. */
static inline u8 anything_set(void) {
u32* ptr = (u32*)trace_bits;
u32 i = (MAP_SIZE >> 2);
while (i--) if (*(ptr++)) return 1;
return 0;
}
/* Get rid of shared memory and temp files (atexit handler). */
static void remove_shm(void) {
if (prog_in) unlink(prog_in); /* Ignore errors */
shmctl(shm_id, IPC_RMID, NULL);
}
/* Configure shared memory. */
static void setup_shm(void) {
u8* shm_str;
shm_id = shmget(IPC_PRIVATE, MAP_SIZE, IPC_CREAT | IPC_EXCL | 0600);
if (shm_id < 0) PFATAL("shmget() failed");
atexit(remove_shm);
shm_str = alloc_printf("%d", shm_id);
setenv(SHM_ENV_VAR, shm_str, 1);
ck_free(shm_str);
trace_bits = shmat(shm_id, NULL, 0);
if (!trace_bits) PFATAL("shmat() failed");
}
/* Read initial file. */
static void read_initial_file(void) {
struct stat st;
s32 fd = open(in_file, O_RDONLY);
if (fd < 0) PFATAL("Unable to open '%s'", in_file);
if (fstat(fd, &st) || !st.st_size)
FATAL("Zero-sized input file.");
if (st.st_size >= TMIN_MAX_FILE)
FATAL("Input file is too large (%u MB max)", TMIN_MAX_FILE / 1024 / 1024);
in_len = st.st_size;
in_data = ck_alloc_nozero(in_len);
ck_read(fd, in_data, in_len, in_file);
close(fd);
OKF("Read %u byte%s from '%s'.", in_len, in_len == 1 ? "" : "s", in_file);
}
/* Write output file. */
static s32 write_to_file(u8* path, u8* mem, u32 len) {
s32 ret;
unlink(path); /* Ignore errors */
ret = open(path, O_RDWR | O_CREAT | O_EXCL, 0600);
if (ret < 0) PFATAL("Unable to create '%s'", path);
ck_write(ret, mem, len, path);
lseek(ret, 0, SEEK_SET);
return ret;
}
/* Write modified data to file for testing. If use_stdin is clear, the old file
is unlinked and a new one is created. Otherwise, prog_in_fd is rewound and
truncated. */
static void write_to_testcase(void* mem, u32 len) {
s32 fd = prog_in_fd;
if (!use_stdin) {
unlink(prog_in); /* Ignore errors. */
fd = open(prog_in, O_WRONLY | O_CREAT | O_EXCL, 0600);
if (fd < 0) PFATAL("Unable to create '%s'", prog_in);
}
else lseek(fd, 0, SEEK_SET);
ck_write(fd, mem, len, prog_in);
if (use_stdin) {
if (ftruncate(fd, len)) PFATAL("ftruncate() failed");
lseek(fd, 0, SEEK_SET);
}
else close(fd);
}
/* Handle timeout signal. */
static void handle_timeout(int sig) {
if (child_pid > 0) {
child_timed_out = 1;
kill(child_pid, SIGKILL);
}
else if (child_pid == -1 && forksrv_pid > 0) {
child_timed_out = 1;
kill(forksrv_pid, SIGKILL);
}
}
/* start the app and it's forkserver */
static void init_forkserver(char** argv) {
static struct itimerval it;
int st_pipe[2], ctl_pipe[2];
int status = 0;
s32 rlen;
ACTF("Spinning up the fork server...");
if (pipe(st_pipe) || pipe(ctl_pipe)) PFATAL("pipe() failed");
forksrv_pid = fork();
if (forksrv_pid < 0) PFATAL("fork() failed");
if (!forksrv_pid) {
struct rlimit r;
if (dup2(use_stdin ? prog_in_fd : dev_null_fd, 0) < 0 ||
dup2(dev_null_fd, 1) < 0 ||
dup2(dev_null_fd, 2) < 0) {
*(u32*)trace_bits = EXEC_FAIL_SIG;
PFATAL("dup2() failed");
}
close(dev_null_fd);
close(prog_in_fd);
setsid();
if (mem_limit) {
r.rlim_max = r.rlim_cur = ((rlim_t)mem_limit) << 20;
#ifdef RLIMIT_AS
setrlimit(RLIMIT_AS, &r); /* Ignore errors */
#else
setrlimit(RLIMIT_DATA, &r); /* Ignore errors */
#endif /* ^RLIMIT_AS */
}
r.rlim_max = r.rlim_cur = 0;
setrlimit(RLIMIT_CORE, &r); /* Ignore errors */
/* Set up control and status pipes, close the unneeded original fds. */
if (dup2(ctl_pipe[0], FORKSRV_FD) < 0) PFATAL("dup2() failed");
if (dup2(st_pipe[1], FORKSRV_FD + 1) < 0) PFATAL("dup2() failed");
close(ctl_pipe[0]);
close(ctl_pipe[1]);
close(st_pipe[0]);
close(st_pipe[1]);
execv(target_path, argv);
*(u32*)trace_bits = EXEC_FAIL_SIG;
exit(0);
}
/* Close the unneeded endpoints. */
close(ctl_pipe[0]);
close(st_pipe[1]);
fsrv_ctl_fd = ctl_pipe[1];
fsrv_st_fd = st_pipe[0];
/* Configure timeout, wait for child, cancel timeout. */
if (exec_tmout) {
child_timed_out = 0;
it.it_value.tv_sec = (exec_tmout * FORK_WAIT_MULT / 1000);
it.it_value.tv_usec = ((exec_tmout * FORK_WAIT_MULT) % 1000) * 1000;
}
setitimer(ITIMER_REAL, &it, NULL);
rlen = read(fsrv_st_fd, &status, 4);
it.it_value.tv_sec = 0;
it.it_value.tv_usec = 0;
setitimer(ITIMER_REAL, &it, NULL);
/* If we have a four-byte "hello" message from the server, we're all set.
Otherwise, try to figure out what went wrong. */
if (rlen == 4) {
ACTF("All right - fork server is up.");
return;
}
if (waitpid(forksrv_pid, &status, 0) <= 0)
PFATAL("waitpid() failed");
u8 child_crashed;
if (WIFSIGNALED(status))
child_crashed = 1;
if (child_timed_out)
SAYF(cLRD "\n+++ Program timed off +++\n" cRST);
else if (stop_soon)
SAYF(cLRD "\n+++ Program aborted by user +++\n" cRST);
else if (child_crashed)
SAYF(cLRD "\n+++ Program killed by signal %u +++\n" cRST, WTERMSIG(status));
}
/* Execute target application. Returns 0 if the changes are a dud, or
1 if they should be kept. */
static u8 run_target(char** argv, u8* mem, u32 len, u8 first_run) {
static struct itimerval it;
static u32 prev_timed_out = 0;
int status = 0;
u32 cksum;
memset(trace_bits, 0, MAP_SIZE);
MEM_BARRIER();
write_to_testcase(mem, len);
s32 res;
/* we have the fork server up and running, so simply
tell it to have at it, and then read back PID. */
if ((res = write(fsrv_ctl_fd, &prev_timed_out, 4)) != 4) {
if (stop_soon) return 0;
RPFATAL(res, "Unable to request new process from fork server (OOM?)");
}
if ((res = read(fsrv_st_fd, &child_pid, 4)) != 4) {
if (stop_soon) return 0;
RPFATAL(res, "Unable to request new process from fork server (OOM?)");
}
if (child_pid <= 0) FATAL("Fork server is misbehaving (OOM?)");
/* Configure timeout, wait for child, cancel timeout. */
if (exec_tmout) {
child_timed_out = 0;
it.it_value.tv_sec = (exec_tmout / 1000);
it.it_value.tv_usec = (exec_tmout % 1000) * 1000;
}
setitimer(ITIMER_REAL, &it, NULL);
if ((res = read(fsrv_st_fd, &status, 4)) != 4) {
if (stop_soon) return 0;
RPFATAL(res, "Unable to communicate with fork server (OOM?)");
}
child_pid = 0;
it.it_value.tv_sec = 0;
it.it_value.tv_usec = 0;
setitimer(ITIMER_REAL, &it, NULL);
MEM_BARRIER();
/* Clean up bitmap, analyze exit condition, etc. */
if (*(u32*)trace_bits == EXEC_FAIL_SIG)
FATAL("Unable to execute '%s'", argv[0]);
classify_counts(trace_bits);
apply_mask((u32*)trace_bits, (u32*)mask_bitmap);
total_execs++;
if (stop_soon) {
ACTF(cRST cLRD "\n+++ Minimization aborted by user +++\n" cRST);
close(write_to_file(out_file, in_data, in_len));
exit(1);
}
/* Always discard inputs that time out. */
if (child_timed_out) {
missed_hangs++;
return 0;
}
/* Handle crashing inputs depending on current mode. */
int crashed = 0;
if (WIFSIGNALED(status) ||
(WIFEXITED(status) && WEXITSTATUS(status) == MSAN_ERROR) ||
(WIFEXITED(status) && WEXITSTATUS(status) && exit_crash)) {
crashed = 1;
}
/* treat all non-zero return values from qemu system test as a crash */
if (qemu_mode > 1 && WEXITSTATUS(status) != 0) {
crashed = 1;
}
if (crashed) {
if (first_run) crash_mode = 1;
if (crash_mode) {
if (!exact_mode) return 1;
} else {
missed_crashes++;
return 0;
}
} else
/* Handle non-crashing inputs appropriately. */
if (crash_mode) {
missed_paths++;
return 0;
}
cksum = hash32(trace_bits, MAP_SIZE, HASH_CONST);
if (first_run) orig_cksum = cksum;
if (orig_cksum == cksum) return 1;
missed_paths++;
return 0;
}
/* Find first power of two greater or equal to val. */
static u32 next_p2(u32 val) {
u32 ret = 1;
while (val > ret) ret <<= 1;
return ret;
}
/* Actually minimize! */
static void minimize(char** argv) {
static u32 alpha_map[256];
u8* tmp_buf = ck_alloc_nozero(in_len);
u32 orig_len = in_len, stage_o_len;
u32 del_len, set_len, del_pos, set_pos, i, alpha_size, cur_pass = 0;
u32 syms_removed, alpha_del0 = 0, alpha_del1, alpha_del2, alpha_d_total = 0;
u8 changed_any, prev_del;
/***********************
* BLOCK NORMALIZATION *
***********************/
set_len = next_p2(in_len / TMIN_SET_STEPS);
set_pos = 0;
if (set_len < TMIN_SET_MIN_SIZE) set_len = TMIN_SET_MIN_SIZE;
ACTF(cBRI "Stage #0: " cRST "One-time block normalization...");
while (set_pos < in_len) {
u8 res;
u32 use_len = MIN(set_len, in_len - set_pos);
for (i = 0; i < use_len; i++)
if (in_data[set_pos + i] != '0') break;
if (i != use_len) {
memcpy(tmp_buf, in_data, in_len);
memset(tmp_buf + set_pos, '0', use_len);
res = run_target(argv, tmp_buf, in_len, 0);
if (res) {
memset(in_data + set_pos, '0', use_len);
changed_any = 1;
alpha_del0 += use_len;
}
}
set_pos += set_len;
}
alpha_d_total += alpha_del0;
OKF("Block normalization complete, %u byte%s replaced.", alpha_del0,
alpha_del0 == 1 ? "" : "s");
next_pass:
ACTF(cYEL "--- " cBRI "Pass #%u " cYEL "---", ++cur_pass);
changed_any = 0;
/******************
* BLOCK DELETION *
******************/
del_len = next_p2(in_len / TRIM_START_STEPS);
stage_o_len = in_len;
ACTF(cBRI "Stage #1: " cRST "Removing blocks of data...");
next_del_blksize:
if (!del_len) del_len = 1;
del_pos = 0;
prev_del = 1;
SAYF(cGRA " Block length = %u, remaining size = %u\n" cRST,
del_len, in_len);
while (del_pos < in_len) {
u8 res;
s32 tail_len;
tail_len = in_len - del_pos - del_len;
if (tail_len < 0) tail_len = 0;
/* If we have processed at least one full block (initially, prev_del == 1),
and we did so without deleting the previous one, and we aren't at the
very end of the buffer (tail_len > 0), and the current block is the same
as the previous one... skip this step as a no-op. */
if (!prev_del && tail_len && !memcmp(in_data + del_pos - del_len,
in_data + del_pos, del_len)) {
del_pos += del_len;
continue;
}
prev_del = 0;
/* Head */
memcpy(tmp_buf, in_data, del_pos);
/* Tail */
memcpy(tmp_buf + del_pos, in_data + del_pos + del_len, tail_len);
res = run_target(argv, tmp_buf, del_pos + tail_len, 0);
if (res) {
memcpy(in_data, tmp_buf, del_pos + tail_len);
prev_del = 1;
in_len = del_pos + tail_len;
changed_any = 1;
} else del_pos += del_len;
}
if (del_len > 1 && in_len >= 1) {
del_len /= 2;
goto next_del_blksize;
}
OKF("Block removal complete, %u bytes deleted.", stage_o_len - in_len);
if (!in_len && changed_any)
WARNF(cLRD "Down to zero bytes - check the command line and mem limit!" cRST);
if (cur_pass > 1 && !changed_any) goto finalize_all;
/*************************
* ALPHABET MINIMIZATION *
*************************/
alpha_size = 0;
alpha_del1 = 0;
syms_removed = 0;
memset(alpha_map, 0, 256 * sizeof(u32));
for (i = 0; i < in_len; i++) {
if (!alpha_map[in_data[i]]) alpha_size++;
alpha_map[in_data[i]]++;
}
ACTF(cBRI "Stage #2: " cRST "Minimizing symbols (%u code point%s)...",
alpha_size, alpha_size == 1 ? "" : "s");
for (i = 0; i < 256; i++) {
u32 r;
u8 res;
if (i == '0' || !alpha_map[i]) continue;
memcpy(tmp_buf, in_data, in_len);
for (r = 0; r < in_len; r++)
if (tmp_buf[r] == i) tmp_buf[r] = '0';
res = run_target(argv, tmp_buf, in_len, 0);
if (res) {
memcpy(in_data, tmp_buf, in_len);
syms_removed++;
alpha_del1 += alpha_map[i];
changed_any = 1;
}
}
alpha_d_total += alpha_del1;
OKF("Symbol minimization finished, %u symbol%s (%u byte%s) replaced.",
syms_removed, syms_removed == 1 ? "" : "s",
alpha_del1, alpha_del1 == 1 ? "" : "s");
/**************************
* CHARACTER MINIMIZATION *
**************************/
alpha_del2 = 0;
ACTF(cBRI "Stage #3: " cRST "Character minimization...");
memcpy(tmp_buf, in_data, in_len);
for (i = 0; i < in_len; i++) {
u8 res, orig = tmp_buf[i];
if (orig == '0') continue;
tmp_buf[i] = '0';
res = run_target(argv, tmp_buf, in_len, 0);
if (res) {
in_data[i] = '0';
alpha_del2++;
changed_any = 1;
} else tmp_buf[i] = orig;
}
alpha_d_total += alpha_del2;
OKF("Character minimization done, %u byte%s replaced.",
alpha_del2, alpha_del2 == 1 ? "" : "s");
if (changed_any) goto next_pass;
finalize_all:
SAYF("\n"
cGRA " File size reduced by : " cRST "%0.02f%% (to %u byte%s)\n"
cGRA " Characters simplified : " cRST "%0.02f%%\n"
cGRA " Number of execs done : " cRST "%u\n"
cGRA " Fruitless execs : " cRST "path=%u crash=%u hang=%s%u\n\n",
100 - ((double)in_len) * 100 / orig_len, in_len, in_len == 1 ? "" : "s",
((double)(alpha_d_total)) * 100 / (in_len ? in_len : 1),
total_execs, missed_paths, missed_crashes, missed_hangs ? cLRD : "",
missed_hangs);
if (total_execs > 50 && missed_hangs * 10 > total_execs)
WARNF(cLRD "Frequent timeouts - results may be skewed." cRST);
}
/* Handle Ctrl-C and the like. */
static void handle_stop_sig(int sig) {
stop_soon = 1;
if (child_pid > 0) kill(child_pid, SIGKILL);
}
/* Do basic preparations - persistent fds, filenames, etc. */
static void set_up_environment(void) {
u8* x;
dev_null_fd = open("/dev/null", O_RDWR);
if (dev_null_fd < 0) PFATAL("Unable to open /dev/null");
if (!prog_in) {
u8* use_dir = ".";
if (access(use_dir, R_OK | W_OK | X_OK)) {
use_dir = getenv("TMPDIR");
if (!use_dir) use_dir = "/tmp";
}
prog_in = alloc_printf("%s/.afl-tmin-temp-%u", use_dir, getpid());
}
unlink(prog_in);
prog_in_fd = open(prog_in, O_RDWR | O_CREAT | O_EXCL, 0600);
if (prog_in_fd < 0) PFATAL("Unable to create '%s'", prog_in);
/* Set sane defaults... */
x = getenv("ASAN_OPTIONS");
if (x) {
if (!strstr(x, "abort_on_error=1"))
FATAL("Custom ASAN_OPTIONS set without abort_on_error=1 - please fix!");
if (!strstr(x, "symbolize=0"))
FATAL("Custom ASAN_OPTIONS set without symbolize=0 - please fix!");
}
x = getenv("MSAN_OPTIONS");
if (x) {
if (!strstr(x, "exit_code=" STRINGIFY(MSAN_ERROR)))
FATAL("Custom MSAN_OPTIONS set without exit_code="
STRINGIFY(MSAN_ERROR) " - please fix!");
if (!strstr(x, "symbolize=0"))
FATAL("Custom MSAN_OPTIONS set without symbolize=0 - please fix!");
}
setenv("ASAN_OPTIONS", "abort_on_error=1:"
"detect_leaks=0:"
"symbolize=0:"
"allocator_may_return_null=1", 0);
setenv("MSAN_OPTIONS", "exit_code=" STRINGIFY(MSAN_ERROR) ":"
"symbolize=0:"
"abort_on_error=1:"
"allocator_may_return_null=1:"
"msan_track_origins=0", 0);
if (getenv("AFL_PRELOAD")) {
setenv("LD_PRELOAD", getenv("AFL_PRELOAD"), 1);
setenv("DYLD_INSERT_LIBRARIES", getenv("AFL_PRELOAD"), 1);
}
}
/* Setup signal handlers, duh. */
static void setup_signal_handlers(void) {
struct sigaction sa;
sa.sa_handler = NULL;
sa.sa_flags = SA_RESTART;
sa.sa_sigaction = NULL;
sigemptyset(&sa.sa_mask);
/* Various ways of saying "stop". */
sa.sa_handler = handle_stop_sig;
sigaction(SIGHUP, &sa, NULL);
sigaction(SIGINT, &sa, NULL);
sigaction(SIGTERM, &sa, NULL);
/* Exec timeout notifications. */
sa.sa_handler = handle_timeout;
sigaction(SIGALRM, &sa, NULL);
}
/* Detect @@ in args. */
static void detect_file_args(char** argv) {
u32 i = 0;
u8* cwd = getcwd(NULL, 0);
if (!cwd) PFATAL("getcwd() failed");
while (argv[i]) {
u8* aa_loc = strstr(argv[i], "@@");
if (aa_loc) {
u8 *aa_subst, *n_arg;
/* Be sure that we're always using fully-qualified paths. */
if (prog_in[0] == '/') aa_subst = prog_in;
else aa_subst = alloc_printf("%s/%s", cwd, prog_in);
/* Construct a replacement argv value. */
*aa_loc = 0;
n_arg = alloc_printf("%s%s%s", argv[i], aa_subst, aa_loc + 2);
argv[i] = n_arg;
*aa_loc = '@';
if (prog_in[0] != '/') ck_free(aa_subst);
}
i++;
}
free(cwd); /* not tracked */
}
/* Display usage hints. */
static void usage(u8* argv0) {
SAYF("\n%s [ options ] -- /path/to/target_app [ ... ]\n\n"
"Required parameters:\n\n"
" -i file - input test case to be shrunk by the tool\n"
" -o file - final output location for the minimized data\n\n"
"Execution control settings:\n\n"
" -f file - input file read by the tested program (stdin)\n"
" -t msec - timeout for each run (%u ms)\n"
" -m megs - memory limit for child process (%u MB)\n"
" -Q - use binary-only instrumentation (QEMU mode)\n\n"
"Minimization settings:\n\n"
" -e - solve for edge coverage only, ignore hit counts\n"
" -x - treat non-zero exit codes as crashes\n\n"
"For additional tips, please consult %s/README.\n\n",
argv0, EXEC_TIMEOUT, MEM_LIMIT, doc_path);
exit(1);
}
/* Find binary. */
static void find_binary(u8* fname) {
u8* env_path = 0;