pwcracker.py

import crypt

def crypt_test(password, salt, checksum='my43charchecksum'):
    '''Test only the logic without crypt library'''

    correct = 'iCeCream9999'
    if password == correct:
        return 'prefix {} suffix'.format(checksum)
    return 'prefix something else suffix'

def main():

    # beginning of the plaintext password
    pw_part = 'iCeCream'

    # random checksum of the real unknow password
    checksum = 'my43charchecksum'

    # random salt
    salt_string = '$mysaltstring' # remember to put $ sign first!

    # sha256 method
    method = '$5'

    # final salt string for the function
    salt = method + salt_string

    # iteration to know the real password e.g. 'iCeCream6070'
    for number in range(10000):
        password = pw_part + str(number).zfill(4)

        # crypt library works only with Unix-like systems
        # example usage:  crypt.crypt('plaintext', '$5$mysalt')
        # example output of crypt.crypt: '$5$mysalt$PGffDtysDjNOnNi/r6.0ECtKy5dsVtaqwZ1VYFuGoUC'
        if checksum in crypt.crypt(password, salt):
            print('password is:', password)
            break

if __name__ == '__main__':
    main()