attack.py

# dead simple dictionary attack for fixed-length passwords.
# this is far from optimal.

from collections import defaultdict
import argparse
import sys
import random

program = sys.argv[0]
args = sys.argv[1:]

parser = argparse.ArgumentParser(
    description="attack: produce fixed-length strings from dictionaries")

parser.add_argument(
    'length', type=int,
    help="the length of the strings to output")
parser.add_argument(
    'path', metavar='text-file', nargs='+',
    help="a dictionary file containing one string per line")
parser.add_argument(
    '-n', metavar='limit', type=float, default='inf',
    help="output this many strings and exit")
parser.add_argument(
    '-s', metavar='seed', type=int, default=None,
    help="use as a seed for the random number generator")

a = parser.parse_args(args)
seed = a.s
limit = a.n
paths = a.path
fixed_length = a.length
del a

lines = []
for path in paths:
    with open(path, "r") as f:
        for line in f:
            lines.append(line.strip('\r\n'))

nlines = defaultdict(lambda: [])
ncount = defaultdict(lambda: 0)
for line in lines:
    length = len(line)
    if length == 0 or length > fixed_length:
        continue
    nlines[length].append(line)
    ncount[length] += 1

del lines

if seed is not None:
    random.seed(seed)

lengths = list(ncount.keys())
length_weights = list(ncount.values())

i = 0
while i < limit:
    s = ''
    new_weights = length_weights.copy()

    while len(s) < fixed_length:
        if len(s) > 0:
            for j, length in enumerate(lengths):
                if len(s) + length > fixed_length:
                    new_weights[j] = 0

        if sum(new_weights) == 0:
            s = ''
            new_weights = length_weights.copy()
            continue

        chosen_length = random.choices(lengths, new_weights)[0]
        s += random.choice(nlines[chosen_length])

    try:
        print(s)
    except OSError:
        # pipe closed.
        break
    i += 1