1012

/*afl-tmin：
独立工具，能够自动收缩测试用例，同时仍然确保它们在目标二进制文件中执行相同的功能（或者触发相同的崩溃）。
另一个类似的工具afl-cmin采用了类似的技巧来消除任何大型测试语料库中的冗余文件。*/

#define U32 unsigned int
#define U16 unsigned short
#define U8  unsigned char (byte)

#define S32 int
#define S16 short int
#define S8  char



#include <stdio.h>
#include <stdlib.h>

/* Main entry point */

int main(int argc, char** argv) //argv指向char*，即argv存的是指向字符串的指针的地址。
{

  s32 opt;
  u8  mem_limit_given = 0, timeout_given = 0, qemu_mode = 0; //u8：最大255
  char** use_argv;

  doc_path = access(DOC_PATH, F_OK) ? "docs" : DOC_PATH;     //R_OK文件是否可读 W_OK文件是否可写入 F_OK 文件是否存在

  SAYF(cCYA "afl-tmin " cBRI VERSION cRST " by <[email protected]>\n");   

  while ((opt = getopt(argc,argv,"+i:o:f:m:t:B:xeQ")) > 0)   //每调用一次getopt返回一个选项，optarg是指向对应选项的参数指针。。
    switch (opt)                                             //从用户terminal输入中找到-i -t ...等配置
    {

      case 'i':

        if (in_file) FATAL("Multiple -i options not supported");
        in_file = optarg;
        break;

      case 'o':

        if (out_file) FATAL("Multiple -o options not supported");
        out_file = optarg;
        break;

      case 'f':

        if (prog_in) FATAL("Multiple -f options not supported");
        use_stdin = 0;
        prog_in   = optarg;
        break;

      case 'e':

        if (edges_only) FATAL("Multiple -e options not supported");
        edges_only = 1;
        break;

      case 'x':

        if (exit_crash) FATAL("Multiple -x options not supported");
        exit_crash = 1;
        break;

      case 'm': {

          u8 suffix = 'M';

          if (mem_limit_given) FATAL("Multiple -m options not supported");
          mem_limit_given = 1;

          if (!strcmp(optarg, "none")) {

            mem_limit = 0;
            break;

          }

          if (sscanf(optarg, "%llu%c", &mem_limit, &suffix) < 1 ||
              optarg[0] == '-') FATAL("Bad syntax used for -m");

          switch (suffix) {                            //定义

            case 'T': mem_limit *= 1024 * 1024; break;
            case 'G': mem_limit *= 1024; break;
            case 'k': mem_limit /= 1024; break;
            case 'M': break;

            default:  FATAL("Unsupported suffix or bad syntax for -m");

          }

          if (mem_limit < 5) FATAL("Dangerously low value of -m");

          if (sizeof(rlim_t) == 4 && mem_limit > 2000)
            FATAL("Value of -m out of range on 32-bit systems");

        }

        break;

      case 't':

        if (timeout_given) FATAL("Multiple -t options not supported");
        timeout_given = 1;

        exec_tmout = atoi(optarg);                          //用户输入空闲等待时间

        if (exec_tmout < 10 || optarg[0] == '-')
          FATAL("Dangerously low value of -t");

        break;

      case 'Q':

        if (qemu_mode) FATAL("Multiple -Q options not supported");
        if (!mem_limit_given) mem_limit = MEM_LIMIT_QEMU;

        qemu_mode = 1;
        break;

      case 'B': /* load bitmap */

        /* This is a secret undocumented option! It is speculated to be useful
           if you have a baseline "boring" input file and another "interesting"
           file you want to minimize.

           You can dump a binary bitmap for the boring file using
           afl-showmap -b, and then load it into afl-tmin via -B. The minimizer
           will then minimize to preserve only the edges that are unique to
           the interesting input file, but ignoring everything from the
           original map.

           The option may be extended and made more official if it proves
           to be useful. */

        if (mask_bitmap) FATAL("Multiple -B options not supported");
        mask_bitmap = ck_alloc(MAP_SIZE);
        read_bitmap(optarg);
        break;

      default:

        usage(argv[0]);                         //显示使用提示

    }

  if (optind == argc || !in_file || !out_file) usage(argv[0]);

  setup_shm();                         //设置共享内存块
  setup_signal_handlers();              //设置信号句柄

  set_up_environment();

  find_binary(argv[optind]);                //606
  detect_file_args(argv + optind);           // 字符串中删除@@

  if (qemu_mode)
    use_argv = get_qemu_argv(argv[0], argv + optind, argc - optind);
  else
    use_argv = argv + optind;

  exact_mode = !!getenv("AFL_TMIN_EXACT");

  SAYF("\n");

  read_initial_file();                        //读初始文件

  ACTF("Performing dry run (mem limit = %llu MB, timeout = %u ms%s)...",
       mem_limit, exec_tmout, edges_only ? ", edges only" : "");

  run_target(use_argv, in_data, in_len, 1);                //删-0 留-1

  if (child_timed_out)
    FATAL("Target binary times out (adjusting -t may help).");

  if (!crash_mode) {

     OKF("Program terminates normally, minimizing in "
         cCYA "instrumented" cRST " mode.");

     if (!anything_set()) FATAL("No instrumentation detected.");

  } else {

     OKF("Program exits with a signal, minimizing in " cMGN "%scrash" cRST
         " mode.", exact_mode ? "EXACT " : "");

  }

  minimize(use_argv);    ///////////===============================================important

  ACTF("Writing output to '%s'...", out_file);

  unlink(prog_in);
  prog_in = NULL;

  close(write_to_file(out_file, in_data, in_len));

  OKF("We're done here. Have a nice day!\n");

  exit(0);

}

/* Actually minimize! */

static void minimize(char** argv)
{     //argv表示的是命令行参数，char** argv可以看成char* argv[]，即一个字符串数组，每个元素对应一个字符串，值为字符串的首地址。因此**argv就是字符串的首字母

  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);           //449；值为1或者2
  set_pos    = 0;

  if (set_len < TMIN_SET_MIN_SIZE) 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);  // use_len: search MIN

    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);           //in_data的前in_len位赋给tmp_buf
      memset(tmp_buf + set_pos, '0', use_len);       //tmp_buf + set_pos的长度是use_len,值为0

      res = run_target(argv, tmp_buf, in_len, 0);          //run_target:通知forkserver可以开始fork并且fuzz了

      if (res) {

        memset(in_data + set_pos, '0', use_len);
        changed_any = 1;                             //flag
        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");   //打印输出

next_pass:

  ACTF(cYEL "--- " cBRI "Pass #%u " cYEL "---", ++cur_pass);   //打印
  changed_any = 0;                                      //flag恢复

  /******************
   * BLOCK DELETION *      //删块
   ******************/

  del_len = next_p2(in_len / TRIM_START_STEPS);                //del_len=1或者2
  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) {       //执行delete

    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;    //428

  /*************************
   * 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);          //往小了赋值

    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);

}   //minimize结束惹


/* Find first power of two greater or equal to val. */
static u32 next_p2(u32 val) {

  u32 ret = 1;
  while (val > ret) ret <<= 1;         //ret=ret << 1 :左移一位，相当于ret乘2：返回1或者2
  return ret;

}



/* 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;
  int status = 0;

  s32 prog_in_fd;
  u32 cksum;

  memset(trace_bits, 0, MAP_SIZE);
  MEM_BARRIER();

  prog_in_fd = write_to_file(prog_in, mem, len);

  child_pid = fork();          //forl()创建新进程

  if (child_pid < 0) PFATAL("fork() failed");

  if (!child_pid) {

    struct rlimit r;
    //https://blog.csdn.net/silent123go/article/details/71108501
    if (dup2(use_stdin ? prog_in_fd : dev_null_fd, 0) < 0 ||     //复制一个现存的文件描述符
        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 */    //https://www.cnblogs.com/niocai/archive/2012/04/01/2428128.html

#endif /* ^RLIMIT_AS */

    }

    r.rlim_max = r.rlim_cur = 0;
    setrlimit(RLIMIT_CORE, &r); /* Ignore errors */

    execv(target_path, argv);

    *(u32*)trace_bits = EXEC_FAIL_SIG;
    exit(0);

  }

  close(prog_in_fd);
  /* Configure timeout, wait for child, cancel timeout. */

  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 (waitpid(child_pid, &status, 0) <= 0) FATAL("waitpid() failed");

  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) {

    SAYF(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. */

  if (WIFSIGNALED(status) ||
      (WIFEXITED(status) && WEXITSTATUS(status) == MSAN_ERROR) ||
      (WIFEXITED(status) && WEXITSTATUS(status) && exit_crash)) {

    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;

}        //run_target结束



/* Find binary. */

static void find_binary(u8* fname) {

  u8* env_path = 0;
  struct stat st;

  if (strchr(fname, '/') || !(env_path = getenv("PATH"))) {

    target_path = ck_strdup(fname);

    if (stat(target_path, &st) || !S_ISREG(st.st_mode) ||
        !(st.st_mode & 0111) || st.st_size < 4)
      FATAL("Program '%s' not found or not executable", fname);

  } else {

    while (env_path) {

      u8 *cur_elem, *delim = strchr(env_path, ':');       //查找env_path首次出现：的位置

      if (delim) {

        cur_elem = ck_alloc(delim - env_path + 1);
        memcpy(cur_elem, env_path, delim - env_path);
        delim++;

      } else cur_elem = ck_strdup(env_path);

      env_path = delim;

      if (cur_elem[0])
        target_path = alloc_printf("%s/%s", cur_elem, fname);
      else
        target_path = ck_strdup(fname);

      ck_free(cur_elem);

      if (!stat(target_path, &st) && S_ISREG(st.st_mode) &&
          (st.st_mode & 0111) && st.st_size >= 4) break;

      ck_free(target_path);
      target_path = 0;

    }

    if (!target_path) FATAL("Program '%s' not found or not executable", fname);

  }

}