/* american fuzzy lop++ - bitmap related routines ---------------------------------------------- Originally written by Michal Zalewski Now maintained by Marc Heuse , Heiko Eißfeldt and Andrea Fioraldi Copyright 2016, 2017 Google Inc. All rights reserved. Copyright 2019-2020 AFLplusplus Project. 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 This is the real deal: the program takes an instrumented binary and attempts a variety of basic fuzzing tricks, paying close attention to how they affect the execution path. */ #include "afl-fuzz.h" #include /* Write bitmap to file. The bitmap is useful mostly for the secret -B option, to focus a separate fuzzing session on a particular interesting input without rediscovering all the others. */ void write_bitmap(afl_state_t *afl) { u8 fname[PATH_MAX]; s32 fd; if (!afl->bitmap_changed) { return; } afl->bitmap_changed = 0; snprintf(fname, PATH_MAX, "%s/fuzz_bitmap", afl->out_dir); fd = open(fname, O_WRONLY | O_CREAT | O_TRUNC, 0600); if (fd < 0) { PFATAL("Unable to open '%s'", fname); } ck_write(fd, afl->virgin_bits, afl->fsrv.map_size, fname); close(fd); } /* Check if the current execution path brings anything new to the table. Update virgin bits to reflect the finds. Returns 1 if the only change is the hit-count for a particular tuple; 2 if there are new tuples seen. Updates the map, so subsequent calls will always return 0. This function is called after every exec() on a fairly large buffer, so it needs to be fast. We do this in 32-bit and 64-bit flavors. */ u8 has_new_bits(afl_state_t *afl, u8 *virgin_map) { #ifdef WORD_SIZE_64 u64 *current = (u64 *)afl->fsrv.trace_bits; u64 *virgin = (u64 *)virgin_map; u32 i = (afl->fsrv.map_size >> 3); #else u32 *current = (u32 *)afl->fsrv.trace_bits; u32 *virgin = (u32 *)virgin_map; u32 i = (afl->fsrv.map_size >> 2); #endif /* ^WORD_SIZE_64 */ // the map size must be a minimum of 8 bytes. // for variable/dynamic map sizes this is ensured in the forkserver u8 ret = 0; while (i--) { /* Optimize for (*current & *virgin) == 0 - i.e., no bits in current bitmap that have not been already cleared from the virgin map - since this will almost always be the case. */ // the (*current) is unnecessary but speeds up the overall comparison if (unlikely(*current) && unlikely(*current & *virgin)) { if (likely(ret < 2)) { u8 *cur = (u8 *)current; u8 *vir = (u8 *)virgin; /* Looks like we have not found any new bytes yet; see if any non-zero bytes in current[] are pristine in virgin[]. */ #ifdef WORD_SIZE_64 if (*virgin == 0xffffffffffffffff || (cur[0] && vir[0] == 0xff) || (cur[1] && vir[1] == 0xff) || (cur[2] && vir[2] == 0xff) || (cur[3] && vir[3] == 0xff) || (cur[4] && vir[4] == 0xff) || (cur[5] && vir[5] == 0xff) || (cur[6] && vir[6] == 0xff) || (cur[7] && vir[7] == 0xff)) { ret = 2; } else { ret = 1; } #else if (*virgin == 0xffffffff || (cur[0] && vir[0] == 0xff) || (cur[1] && vir[1] == 0xff) || (cur[2] && vir[2] == 0xff) || (cur[3] && vir[3] == 0xff)) ret = 2; else ret = 1; #endif /* ^WORD_SIZE_64 */ } *virgin &= ~*current; } ++current; ++virgin; } if (unlikely(ret) && likely(virgin_map == afl->virgin_bits)) { afl->bitmap_changed = 1; } return ret; } /* Count the number of bits set in the provided bitmap. Used for the status screen several times every second, does not have to be fast. */ u32 count_bits(afl_state_t *afl, u8 *mem) { u32 *ptr = (u32 *)mem; u32 i = (afl->fsrv.map_size >> 2); u32 ret = 0; while (i--) { u32 v = *(ptr++); /* This gets called on the inverse, virgin bitmap; optimize for sparse data. */ if (v == 0xffffffff) { ret += 32; continue; } v -= ((v >> 1) & 0x55555555); v = (v & 0x33333333) + ((v >> 2) & 0x33333333); ret += (((v + (v >> 4)) & 0xF0F0F0F) * 0x01010101) >> 24; } return ret; } /* Count the number of bytes set in the bitmap. Called fairly sporadically, mostly to update the status screen or calibrate and examine confirmed new paths. */ u32 count_bytes(afl_state_t *afl, u8 *mem) { u32 *ptr = (u32 *)mem; u32 i = (afl->fsrv.map_size >> 2); u32 ret = 0; while (i--) { u32 v = *(ptr++); if (!v) { continue; } if (v & 0x000000ff) { ++ret; } if (v & 0x0000ff00) { ++ret; } if (v & 0x00ff0000) { ++ret; } if (v & 0xff000000) { ++ret; } } return ret; } /* Count the number of non-255 bytes set in the bitmap. Used strictly for the status screen, several calls per second or so. */ u32 count_non_255_bytes(afl_state_t *afl, u8 *mem) { u32 *ptr = (u32 *)mem; u32 i = (afl->fsrv.map_size >> 2); u32 ret = 0; while (i--) { u32 v = *(ptr++); /* This is called on the virgin bitmap, so optimize for the most likely case. */ if (v == 0xffffffff) { continue; } if ((v & 0x000000ff) != 0x000000ff) { ++ret; } if ((v & 0x0000ff00) != 0x0000ff00) { ++ret; } if ((v & 0x00ff0000) != 0x00ff0000) { ++ret; } if ((v & 0xff000000) != 0xff000000) { ++ret; } } return ret; } /* Destructively simplify trace by eliminating hit count information and replacing it with 0x80 or 0x01 depending on whether the tuple is hit or not. Called on every new crash or timeout, should be reasonably fast. */ const u8 simplify_lookup[256] = { [0] = 1, [1 ... 255] = 128 }; #ifdef WORD_SIZE_64 void simplify_trace(afl_state_t *afl, u64 *mem) { u32 i = (afl->fsrv.map_size >> 3); while (i--) { /* Optimize for sparse bitmaps. */ if (unlikely(*mem)) { u8 *mem8 = (u8 *)mem; mem8[0] = simplify_lookup[mem8[0]]; mem8[1] = simplify_lookup[mem8[1]]; mem8[2] = simplify_lookup[mem8[2]]; mem8[3] = simplify_lookup[mem8[3]]; mem8[4] = simplify_lookup[mem8[4]]; mem8[5] = simplify_lookup[mem8[5]]; mem8[6] = simplify_lookup[mem8[6]]; mem8[7] = simplify_lookup[mem8[7]]; } else { *mem = 0x0101010101010101ULL; } ++mem; } } #else void simplify_trace(afl_state_t *afl, u32 *mem) { u32 i = (afl->fsrv.map_size >> 2); while (i--) { /* Optimize for sparse bitmaps. */ if (unlikely(*mem)) { u8 *mem8 = (u8 *)mem; mem8[0] = simplify_lookup[mem8[0]]; mem8[1] = simplify_lookup[mem8[1]]; mem8[2] = simplify_lookup[mem8[2]]; mem8[3] = simplify_lookup[mem8[3]]; } else *mem = 0x01010101; ++mem; } } #endif /* ^WORD_SIZE_64 */ /* Destructively classify execution counts in a trace. This is used as a preprocessing step for any newly acquired traces. Called on every exec, must be fast. */ static const u8 count_class_lookup8[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 u16 count_class_lookup16[65536]; void init_count_class16(void) { u32 b1, b2; for (b1 = 0; b1 < 256; b1++) { for (b2 = 0; b2 < 256; b2++) { count_class_lookup16[(b1 << 8) + b2] = (count_class_lookup8[b1] << 8) | count_class_lookup8[b2]; } } } #ifdef WORD_SIZE_64 void classify_counts(afl_forkserver_t *fsrv) { u64 *mem = (u64 *)fsrv->trace_bits; u32 i = (fsrv->map_size >> 3); while (i--) { /* Optimize for sparse bitmaps. */ if (unlikely(*mem)) { u16 *mem16 = (u16 *)mem; mem16[0] = count_class_lookup16[mem16[0]]; mem16[1] = count_class_lookup16[mem16[1]]; mem16[2] = count_class_lookup16[mem16[2]]; mem16[3] = count_class_lookup16[mem16[3]]; } ++mem; } } #else void classify_counts(afl_forkserver_t *fsrv) { u32 *mem = (u32 *)fsrv->trace_bits; u32 i = (fsrv->map_size >> 2); while (i--) { /* Optimize for sparse bitmaps. */ if (unlikely(*mem)) { u16 *mem16 = (u16 *)mem; mem16[0] = count_class_lookup16[mem16[0]]; mem16[1] = count_class_lookup16[mem16[1]]; } ++mem; } } #endif /* ^WORD_SIZE_64 */ /* Compact trace bytes into a smaller bitmap. We effectively just drop the count information here. This is called only sporadically, for some new paths. */ void minimize_bits(afl_state_t *afl, u8 *dst, u8 *src) { u32 i = 0; while (i < afl->fsrv.map_size) { if (*(src++)) { dst[i >> 3] |= 1 << (i & 7); } ++i; } } #ifndef SIMPLE_FILES /* Construct a file name for a new test case, capturing the operation that led to its discovery. Returns a ptr to afl->describe_op_buf_256. */ u8 *describe_op(afl_state_t *afl, u8 hnb) { u8 *ret = afl->describe_op_buf_256; if (unlikely(afl->syncing_party)) { sprintf(ret, "sync:%s,src:%06u", afl->syncing_party, afl->syncing_case); } else { sprintf(ret, "src:%06u", afl->current_entry); if (afl->splicing_with >= 0) { sprintf(ret + strlen(ret), "+%06d", afl->splicing_with); } sprintf(ret + strlen(ret), ",time:%llu", get_cur_time() - afl->start_time); sprintf(ret + strlen(ret), ",op:%s", afl->stage_short); if (afl->stage_cur_byte >= 0) { sprintf(ret + strlen(ret), ",pos:%d", afl->stage_cur_byte); if (afl->stage_val_type != STAGE_VAL_NONE) { sprintf(ret + strlen(ret), ",val:%s%+d", (afl->stage_val_type == STAGE_VAL_BE) ? "be:" : "", afl->stage_cur_val); } } else { sprintf(ret + strlen(ret), ",rep:%d", afl->stage_cur_val); } } if (hnb == 2) { strcat(ret, ",+cov"); } return ret; } #endif /* !SIMPLE_FILES */ /* Write a message accompanying the crash directory :-) */ static void write_crash_readme(afl_state_t *afl) { u8 fn[PATH_MAX]; s32 fd; FILE *f; u8 val_buf[STRINGIFY_VAL_SIZE_MAX]; sprintf(fn, "%s/crashes/README.txt", afl->out_dir); fd = open(fn, O_WRONLY | O_CREAT | O_EXCL, 0600); /* Do not die on errors here - that would be impolite. */ if (unlikely(fd < 0)) { return; } f = fdopen(fd, "w"); if (unlikely(!f)) { close(fd); return; } fprintf( f, "Command line used to find this crash:\n\n" "%s\n\n" "If you can't reproduce a bug outside of afl-fuzz, be sure to set the " "same\n" "memory limit. The limit used for this fuzzing session was %s.\n\n" "Need a tool to minimize test cases before investigating the crashes or " "sending\n" "them to a vendor? Check out the afl-tmin that comes with the fuzzer!\n\n" "Found any cool bugs in open-source tools using afl-fuzz? If yes, please " "drop\n" "an mail at once the issues are fixed\n\n" " https://github.com/AFLplusplus/AFLplusplus\n\n", afl->orig_cmdline, stringify_mem_size(val_buf, sizeof(val_buf), afl->fsrv.mem_limit << 20)); /* ignore errors */ fclose(f); } /* Check if the result of an execve() during routine fuzzing is interesting, save or queue the input test case for further analysis if so. Returns 1 if entry is saved, 0 otherwise. */ u8 save_if_interesting(afl_state_t *afl, void *mem, u32 len, u8 fault) { if (unlikely(len == 0)) { return 0; } u8 *queue_fn = ""; u8 hnb = '\0'; s32 fd; u8 keeping = 0, res; u8 fn[PATH_MAX]; /* Update path frequency. */ u32 cksum = hash32(afl->fsrv.trace_bits, afl->fsrv.map_size, HASH_CONST); struct queue_entry *q = afl->queue; while (q) { if (q->exec_cksum == cksum) { q->n_fuzz = q->n_fuzz + 1; break; } q = q->next; } if (unlikely(fault == afl->crash_mode)) { /* Keep only if there are new bits in the map, add to queue for future fuzzing, etc. */ if (!(hnb = has_new_bits(afl, afl->virgin_bits))) { if (unlikely(afl->crash_mode)) { ++afl->total_crashes; } return 0; } #ifndef SIMPLE_FILES queue_fn = alloc_printf("%s/queue/id:%06u,%s", afl->out_dir, afl->queued_paths, describe_op(afl, hnb)); #else queue_fn = alloc_printf("%s/queue/id_%06u", afl->out_dir, afl->queued_paths); #endif /* ^!SIMPLE_FILES */ add_to_queue(afl, queue_fn, len, 0); if (hnb == 2) { afl->queue_top->has_new_cov = 1; ++afl->queued_with_cov; } afl->queue_top->exec_cksum = cksum; /* Try to calibrate inline; this also calls update_bitmap_score() when successful. */ res = calibrate_case(afl, afl->queue_top, mem, afl->queue_cycle - 1, 0); if (unlikely(res == FSRV_RUN_ERROR)) { FATAL("Unable to execute target application"); } fd = open(queue_fn, O_WRONLY | O_CREAT | O_EXCL, 0600); if (unlikely(fd < 0)) { PFATAL("Unable to create '%s'", queue_fn); } ck_write(fd, mem, len, queue_fn); close(fd); keeping = 1; } switch (fault) { case FSRV_RUN_TMOUT: /* Timeouts are not very interesting, but we're still obliged to keep a handful of samples. We use the presence of new bits in the hang-specific bitmap as a signal of uniqueness. In "dumb" mode, we just keep everything. */ ++afl->total_tmouts; if (afl->unique_hangs >= KEEP_UNIQUE_HANG) { return keeping; } if (likely(!afl->dumb_mode)) { #ifdef WORD_SIZE_64 simplify_trace(afl, (u64 *)afl->fsrv.trace_bits); #else simplify_trace(afl, (u32 *)afl->fsrv.trace_bits); #endif /* ^WORD_SIZE_64 */ if (!has_new_bits(afl, afl->virgin_tmout)) { return keeping; } } ++afl->unique_tmouts; /* Before saving, we make sure that it's a genuine hang by re-running the target with a more generous timeout (unless the default timeout is already generous). */ if (afl->fsrv.exec_tmout < afl->hang_tmout) { u8 new_fault; write_to_testcase(afl, mem, len); new_fault = fuzz_run_target(afl, &afl->fsrv, afl->hang_tmout); /* A corner case that one user reported bumping into: increasing the timeout actually uncovers a crash. Make sure we don't discard it if so. */ if (!afl->stop_soon && new_fault == FSRV_RUN_CRASH) { goto keep_as_crash; } if (afl->stop_soon || new_fault != FSRV_RUN_TMOUT) { return keeping; } } #ifndef SIMPLE_FILES snprintf(fn, PATH_MAX, "%s/hangs/id:%06llu,%s", afl->out_dir, afl->unique_hangs, describe_op(afl, 0)); #else snprintf(fn, PATH_MAX, "%s/hangs/id_%06llu", afl->out_dir, afl->unique_hangs); #endif /* ^!SIMPLE_FILES */ ++afl->unique_hangs; afl->last_hang_time = get_cur_time(); break; case FSRV_RUN_CRASH: keep_as_crash: /* This is handled in a manner roughly similar to timeouts, except for slightly different limits and no need to re-run test cases. */ ++afl->total_crashes; if (afl->unique_crashes >= KEEP_UNIQUE_CRASH) { return keeping; } if (likely(!afl->dumb_mode)) { #ifdef WORD_SIZE_64 simplify_trace(afl, (u64 *)afl->fsrv.trace_bits); #else simplify_trace(afl, (u32 *)afl->fsrv.trace_bits); #endif /* ^WORD_SIZE_64 */ if (!has_new_bits(afl, afl->virgin_crash)) { return keeping; } } if (unlikely(!afl->unique_crashes)) { write_crash_readme(afl); } #ifndef SIMPLE_FILES snprintf(fn, PATH_MAX, "%s/crashes/id:%06llu,sig:%02u,%s", afl->out_dir, afl->unique_crashes, afl->fsrv.last_kill_signal, describe_op(afl, 0)); #else snprintf(fn, PATH_MAX, "%s/crashes/id_%06llu_%02u", afl->out_dir, afl->unique_crashes, afl->last_kill_signal); #endif /* ^!SIMPLE_FILES */ ++afl->unique_crashes; if (unlikely(afl->infoexec)) { // if the user wants to be informed on new crashes - do that #if !TARGET_OS_IPHONE // we dont care if system errors, but we dont want a // compiler warning either // See // https://stackoverflow.com/questions/11888594/ignoring-return-values-in-c (void)(system(afl->infoexec) + 1); #else WARNF("command execution unsupported"); #endif } afl->last_crash_time = get_cur_time(); afl->last_crash_execs = afl->fsrv.total_execs; break; case FSRV_RUN_ERROR: FATAL("Unable to execute target application"); default: return keeping; } /* If we're here, we apparently want to save the crash or hang test case, too. */ fd = open(fn, O_WRONLY | O_CREAT | O_EXCL, 0600); if (unlikely(fd < 0)) { PFATAL("Unable to create '%s'", fn); } ck_write(fd, mem, len, fn); close(fd); return keeping; }