picoctf/248/level4.py

import hashlib

### THIS FUNCTION WILL NOT HELP YOU FIND THE FLAG --LT ########################
def str_xor(secret, key):
    #extend key to secret length
    new_key = key
    i = 0
    while len(new_key) < len(secret):
        new_key = new_key + key[i]
        i = (i + 1) % len(key)        
    return "".join([chr(ord(secret_c) ^ ord(new_key_c)) for (secret_c,new_key_c) in zip(secret,new_key)])
###############################################################################

flag_enc = open('level4.flag.txt.enc', 'rb').read()
correct_pw_hash = open('level4.hash.bin', 'rb').read()


def hash_pw(pw_str):
    pw_bytes = bytearray()
    pw_bytes.extend(pw_str.encode())
    m = hashlib.md5()
    m.update(pw_bytes)
    return m.digest()


def level_4_pw_check():
    user_pw = input("Please enter correct password for flag: ")
    user_pw_hash = hash_pw(user_pw)
    
    if( user_pw_hash == correct_pw_hash ):
        print("Welcome back... your flag, user:")
        decryption = str_xor(flag_enc.decode(), user_pw)
        print(decryption)
        return
    print("That password is incorrect")


if __name__ == '__main__':
    level_4_pw_check()



# The strings below are 100 possibilities for the correct password. 
#   (Only 1 is correct)
pos_pw_list = ["6288", "6152", "4c7a", "b722", "9a6e", "6717", "4389", "1a28", "37ac", "de4f", "eb28", "351b", "3d58", "948b", "231b", "973a", "a087", "384a", "6d3c", "9065", "725c", "fd60", "4d4f", "6a60", "7213", "93e6", "8c54", "537d", "a1da", "c718", "9de8", "ebe3", "f1c5", "a0bf", "ccab", "4938", "8f97", "3327", "8029", "41f2", "a04f", "c7f9", "b453", "90a5", "25dc", "26b0", "cb42", "de89", "2451", "1dd3", "7f2c", "8919", "f3a9", "b88f", "eaa8", "776a", "6236", "98f5", "492b", "507d", "18e8", "cfb5", "76fd", "6017", "30de", "bbae", "354e", "4013", "3153", "e9cc", "cba9", "25ea", "c06c", "a166", "faf1", "2264", "2179", "cf30", "4b47", "3446", "b213", "88a3", "6253", "db88", "c38c", "a48c", "3e4f", "7208", "9dcb", "fc77", "e2cf", "8552", "f6f8", "7079", "42ef", "391e", "8a6d", "2154", "d964", "49ec"]