genpasswd.py

genpasswd.py

#!/usr/bin/env python3

import argparse
import logging
import math
import random
import string
import typing

DEFAULT_DICT_FILE = "/usr/share/dict/words"
DEFAULT_WORD_COUNT = 3
DEFAULT_SYMBOL_COUNT = 10
SYMBOLS = string.ascii_letters = string.digits + string.punctuation


def main() -> None:
    parser = make_argparser()
    args = parser.parse_args()
    num_words = init_from_args(args)
    log = logging.getLogger(__name__)
    if args.symbols:
        sep = ""
        elements: typing.Union[list, str] = SYMBOLS
        log.info("Using %d symbols from: %s", num_words, elements)
    else:
        sep = "-"
        dict_file = args.dict_file
        if not dict_file:
            dict_file = open(DEFAULT_DICT_FILE, "r")
        log.info("Using %d words from: %s", num_words, dict_file.name)
        elements = [w.strip() for w in dict_file.readlines() if len(w.strip()) > 2]
    randgen = random.SystemRandom()
    choices = [randgen.choice(elements) for _ in range(num_words)]
    log.info("Entropy: %.2f bits", math.log2(len(elements) ** num_words))
    print(sep.join(choices))


def make_argparser() -> argparse.ArgumentParser:
    parser = argparse.ArgumentParser(
        description="Generate a random password according to https://xkcd.com/936/."
    )
    parser.add_argument(
        "-s",
        "--symbols",
        action="store_true",
        default=False,
        help="Generate random symbols instead of words.",
    )
    parser.add_argument(
        "-n",
        "--num-words",
        dest="num_words",
        default=None,
        type=int,
        help=(
            "Number of words or symbols to generate. "
            "Default is {} words or {} symbols if using -s option."
        ).format(DEFAULT_WORD_COUNT, DEFAULT_SYMBOL_COUNT),
    )
    parser.add_argument("-f", "--dict-file", type=argparse.FileType("r"), default=None)
    parser.add_argument(
        "-v", "--verbose", action="count", default=0, help="Verbose mode."
    )
    return parser


def init_from_args(args) -> int:
    if args.verbose:
        logging.basicConfig(level=logging.INFO)
    else:
        logging.basicConfig()
    num_words = args.num_words
    if not num_words:
        if args.symbols:
            num_words = DEFAULT_SYMBOL_COUNT
        else:
            num_words = DEFAULT_WORD_COUNT
    return num_words


if __name__ == "__main__":
    main()