We are greeted with a binary file download and an initial investigation with file reveals a 32-bit ELF binary (stripped, of course): ➜ file happy_tree happy_tree: ELF 32-bit LSB pie executable, Intel 80386, version 1 (SYSV), dynamically linked, interpreter /lib/ld-linux.so.2, for GNU/Linux 3.2.0, BuildID[sha1]=fd7f1b2d769e389444cc6eea0f801be7ebc6a7e4, stripped Upon opening the binary with my favourite disassembler, some unusual things reveal themselves: IDA is unable to find the main entrypoint (not that unusual, but more on that later) Address calculations seemed to be done in some sort of relative manner.

In this challenge, we’re looking at a modern type of pyjail escape. Upon first connecting, we’re informed about the source code of the challenge being available, so we can have a look at that first. #!/usr/bin/env python3 import pathlib import re import signal import sys import audit_sandbox if sys.version_info[:3] < (3, 8, 2): raise RuntimeError('Python version too old') WELCOME = f'''\ Welcome to PyAuCalc, an awesome calculator based on Python {'.