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hlongmore on 08/17/11

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Last Edited at 08/17/11 05:03pm

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Password Strength Checker

/ Published in: Python

This is based on the JavaScript snippet at the snipplr URL listed. It in turn referenced a page that is no longer available. So I have decided to make my pythonification of the JavaScript available for others instead of hoarding it.

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"""
Class for checking the strength of a password.
Copyright (C) 2011 Henry Longmore.  This version
of this file may be copied for personal, educational,
or commercial purposes.  Use at your own risk.
"""

import os
from os import path
import math

# Nota Bene: the configuration module is non-standard. You will
# need to format and read your dictionary file yourself.
from djangoapps import configuration

password_dict = path.join(os.sep, 'path', 'to', 'your', 'password.dictionary')

# Based on Password Strength Meter posted at Snipplr
# http://snipplr.com/view/8755/password-strength-meter/

class PasswordStrengthChecker(object):
    def __init__(self, strength='medium', pwd_dict=''):
        self.punctuation = list("!@#$%^&* ()_+-='\";:[{]}\|.>,</?`~")
        self.similarity_map = {
            '3': 'e', 'x': 'k', '5': 's', '$': 's', '6': 'g', '7': 't',
            '8': 'b', '|': 'l', '9': 'g', '+': 't', '@': 'a', '0': 'o',
            '1': 'l', '2': 'z', '!': 'i', '1': 'i'}
        password_dictionary = configuration.Configuration(configpath=pwd_dict)
        self.word_list = dict()
        for i in xrange(3, 17):
            self.word_list[i] = password_dictionary.get_option('%s' % i, [])

self.strengths = ['medium', 'strong', 'best']
        self.thresholds = {'medium': 0.8, 'strong': 0.6, 'best': 0.6}
        self.min_length = {'medium': 8, 'strong': 8, 'best': 14}
        self.min_charsets = {'medium': 2, 'strong': 3, 'best': 3}
        self.similarity = {'medium': False, 'strong': True, 'best': True}

if strength not in self.strengths:
            strength = self.strengths[0]
        self.strength = strength

def is_charset_type(self, c, c_class):
        if c_class == 'capital':
            return c.isalpha() and c == c.upper()
        if c_class == 'lower':
            return c.isalpha() and c == c.lower()
        if c_class == 'digit':
            return c.isdigit()
        if c_class == 'punctuation':
            return c in self.punctuation
        return False

def canonicalize_word(self, word, letters_only=False):
        canonicalized = ''
        for c in list(word.lower()):
            if letters_only and not self.is_charset_type(c, 'lower'):
                canonicalized += c
            else:
                canonicalized += self.similarity_map.get(c, c)
        return canonicalized

def charset_span(self, word):
        checks = {'capital': 0, 'lower': 0, 'digit': 0, 'punctuation': 0}
        for c in list(word):
            for key in checks:
                if not checks[key] and self.is_charset_type(c, key):
                    checks[key] = 1
                    break
        return sum(checks.values())

def in_dictionary(self, word):
        similarity_check = self.similarity[self.strength]
        canonicalized = self.canonicalize_word(word, letters_only=similarity_check)
        word_length = len(canonicalized)
        if canonicalized in self.word_list[word_length]:
            return True
        if similarity_check:
            minimum_meaningful_match = int(math.floor((self.thresholds[self.strength]) * word_length))
            for length in xrange(minimum_meaningful_match, word_length):
                for start in xrange(0, word_length - minimum_meaningful_match):
                    subword = canonicalized[start:start + length]
                    if subword in self.word_list[len(subword)]:
                        return True
        return False

def strong_enough(self, password):
        if not password:
            return False
        if len(password) < self.min_length[self.strength]:
            return False
        if self.charset_span(password) < self.min_charsets[self.strength]:
            return False
        if self.in_dictionary(password):
            return False
        return True

global password_checker
password_checker = PasswordStrengthChecker(strength='medium', pwd_dict=password_dict)

URL: http://snipplr.com/view/8755/password-strength-meter/

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