505 lines
17 KiB
Python
505 lines
17 KiB
Python
from __future__ import unicode_literals
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import base64
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import binascii
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from collections import OrderedDict
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import hashlib
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import importlib
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from django.dispatch import receiver
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from django.conf import settings
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from django.test.signals import setting_changed
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from django.utils.encoding import force_bytes, force_str, force_text
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from django.core.exceptions import ImproperlyConfigured
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from django.utils.crypto import (
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pbkdf2, constant_time_compare, get_random_string)
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from django.utils.module_loading import import_by_path
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from django.utils.translation import ugettext_noop as _
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UNUSABLE_PASSWORD_PREFIX = '!' # This will never be a valid encoded hash
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UNUSABLE_PASSWORD_SUFFIX_LENGTH = 40 # number of random chars to add after UNUSABLE_PASSWORD_PREFIX
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HASHERS = None # lazily loaded from PASSWORD_HASHERS
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PREFERRED_HASHER = None # defaults to first item in PASSWORD_HASHERS
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@receiver(setting_changed)
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def reset_hashers(**kwargs):
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if kwargs['setting'] == 'PASSWORD_HASHERS':
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global HASHERS, PREFERRED_HASHER
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HASHERS = None
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PREFERRED_HASHER = None
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def is_password_usable(encoded):
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if encoded is None or encoded.startswith(UNUSABLE_PASSWORD_PREFIX):
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return False
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try:
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identify_hasher(encoded)
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except ValueError:
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return False
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return True
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def check_password(password, encoded, setter=None, preferred='default'):
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"""
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Returns a boolean of whether the raw password matches the three
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part encoded digest.
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If setter is specified, it'll be called when you need to
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regenerate the password.
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"""
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if password is None or not is_password_usable(encoded):
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return False
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preferred = get_hasher(preferred)
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hasher = identify_hasher(encoded)
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must_update = hasher.algorithm != preferred.algorithm
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is_correct = hasher.verify(password, encoded)
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if setter and is_correct and must_update:
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setter(password)
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return is_correct
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def make_password(password, salt=None, hasher='default'):
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"""
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Turn a plain-text password into a hash for database storage
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Same as encode() but generates a new random salt.
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If password is None then a concatenation of
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UNUSABLE_PASSWORD_PREFIX and a random string will be returned
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which disallows logins. Additional random string reduces chances
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of gaining access to staff or superuser accounts.
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See ticket #20079 for more info.
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"""
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if password is None:
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return UNUSABLE_PASSWORD_PREFIX + get_random_string(UNUSABLE_PASSWORD_SUFFIX_LENGTH)
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hasher = get_hasher(hasher)
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if not salt:
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salt = hasher.salt()
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return hasher.encode(password, salt)
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def load_hashers(password_hashers=None):
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global HASHERS
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global PREFERRED_HASHER
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hashers = []
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if not password_hashers:
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password_hashers = settings.PASSWORD_HASHERS
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for backend in password_hashers:
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hasher = import_by_path(backend)()
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if not getattr(hasher, 'algorithm'):
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raise ImproperlyConfigured("hasher doesn't specify an "
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"algorithm name: %s" % backend)
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hashers.append(hasher)
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HASHERS = dict((hasher.algorithm, hasher) for hasher in hashers)
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PREFERRED_HASHER = hashers[0]
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def get_hasher(algorithm='default'):
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"""
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Returns an instance of a loaded password hasher.
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If algorithm is 'default', the default hasher will be returned.
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This function will also lazy import hashers specified in your
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settings file if needed.
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"""
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if hasattr(algorithm, 'algorithm'):
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return algorithm
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elif algorithm == 'default':
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if PREFERRED_HASHER is None:
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load_hashers()
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return PREFERRED_HASHER
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else:
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if HASHERS is None:
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load_hashers()
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if algorithm not in HASHERS:
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raise ValueError("Unknown password hashing algorithm '%s'. "
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"Did you specify it in the PASSWORD_HASHERS "
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"setting?" % algorithm)
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return HASHERS[algorithm]
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def identify_hasher(encoded):
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"""
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Returns an instance of a loaded password hasher.
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Identifies hasher algorithm by examining encoded hash, and calls
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get_hasher() to return hasher. Raises ValueError if
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algorithm cannot be identified, or if hasher is not loaded.
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"""
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# Ancient versions of Django created plain MD5 passwords and accepted
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# MD5 passwords with an empty salt.
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if ((len(encoded) == 32 and '$' not in encoded) or
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(len(encoded) == 37 and encoded.startswith('md5$$'))):
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algorithm = 'unsalted_md5'
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# Ancient versions of Django accepted SHA1 passwords with an empty salt.
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elif len(encoded) == 46 and encoded.startswith('sha1$$'):
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algorithm = 'unsalted_sha1'
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else:
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algorithm = encoded.split('$', 1)[0]
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return get_hasher(algorithm)
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def mask_hash(hash, show=6, char="*"):
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"""
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Returns the given hash, with only the first ``show`` number shown. The
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rest are masked with ``char`` for security reasons.
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"""
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masked = hash[:show]
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masked += char * len(hash[show:])
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return masked
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class BasePasswordHasher(object):
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"""
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Abstract base class for password hashers
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When creating your own hasher, you need to override algorithm,
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verify(), encode() and safe_summary().
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PasswordHasher objects are immutable.
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"""
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algorithm = None
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library = None
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def _load_library(self):
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if self.library is not None:
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if isinstance(self.library, (tuple, list)):
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name, mod_path = self.library
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else:
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mod_path = self.library
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try:
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module = importlib.import_module(mod_path)
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except ImportError as e:
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raise ValueError("Couldn't load %r algorithm library: %s" %
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(self.__class__.__name__, e))
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return module
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raise ValueError("Hasher %r doesn't specify a library attribute" %
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self.__class__.__name__)
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def salt(self):
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"""
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Generates a cryptographically secure nonce salt in ascii
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"""
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return get_random_string()
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def verify(self, password, encoded):
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"""
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Checks if the given password is correct
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"""
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raise NotImplementedError()
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def encode(self, password, salt):
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"""
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Creates an encoded database value
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The result is normally formatted as "algorithm$salt$hash" and
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must be fewer than 128 characters.
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"""
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raise NotImplementedError()
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def safe_summary(self, encoded):
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"""
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Returns a summary of safe values
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The result is a dictionary and will be used where the password field
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must be displayed to construct a safe representation of the password.
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"""
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raise NotImplementedError()
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class PBKDF2PasswordHasher(BasePasswordHasher):
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"""
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Secure password hashing using the PBKDF2 algorithm (recommended)
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Configured to use PBKDF2 + HMAC + SHA256 with 10000 iterations.
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The result is a 64 byte binary string. Iterations may be changed
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safely but you must rename the algorithm if you change SHA256.
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"""
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algorithm = "pbkdf2_sha256"
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iterations = 10000
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digest = hashlib.sha256
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def encode(self, password, salt, iterations=None):
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assert password is not None
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assert salt and '$' not in salt
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if not iterations:
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iterations = self.iterations
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hash = pbkdf2(password, salt, iterations, digest=self.digest)
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hash = base64.b64encode(hash).decode('ascii').strip()
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return "%s$%d$%s$%s" % (self.algorithm, iterations, salt, hash)
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def verify(self, password, encoded):
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algorithm, iterations, salt, hash = encoded.split('$', 3)
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assert algorithm == self.algorithm
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encoded_2 = self.encode(password, salt, int(iterations))
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return constant_time_compare(encoded, encoded_2)
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def safe_summary(self, encoded):
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algorithm, iterations, salt, hash = encoded.split('$', 3)
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assert algorithm == self.algorithm
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return OrderedDict([
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(_('algorithm'), algorithm),
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(_('iterations'), iterations),
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(_('salt'), mask_hash(salt)),
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(_('hash'), mask_hash(hash)),
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])
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class PBKDF2SHA1PasswordHasher(PBKDF2PasswordHasher):
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"""
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Alternate PBKDF2 hasher which uses SHA1, the default PRF
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recommended by PKCS #5. This is compatible with other
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implementations of PBKDF2, such as openssl's
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PKCS5_PBKDF2_HMAC_SHA1().
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"""
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algorithm = "pbkdf2_sha1"
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digest = hashlib.sha1
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class BCryptSHA256PasswordHasher(BasePasswordHasher):
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"""
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Secure password hashing using the bcrypt algorithm (recommended)
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This is considered by many to be the most secure algorithm but you
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must first install the bcrypt library. Please be warned that
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this library depends on native C code and might cause portability
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issues.
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"""
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algorithm = "bcrypt_sha256"
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digest = hashlib.sha256
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library = ("bcrypt", "bcrypt")
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rounds = 12
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def salt(self):
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bcrypt = self._load_library()
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return bcrypt.gensalt(self.rounds)
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def encode(self, password, salt):
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bcrypt = self._load_library()
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# Need to reevaluate the force_bytes call once bcrypt is supported on
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# Python 3
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# Hash the password prior to using bcrypt to prevent password truncation
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# See: https://code.djangoproject.com/ticket/20138
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if self.digest is not None:
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# We use binascii.hexlify here because Python3 decided that a hex encoded
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# bytestring is somehow a unicode.
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password = binascii.hexlify(self.digest(force_bytes(password)).digest())
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else:
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password = force_bytes(password)
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data = bcrypt.hashpw(password, salt)
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return "%s$%s" % (self.algorithm, force_text(data))
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def verify(self, password, encoded):
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algorithm, data = encoded.split('$', 1)
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assert algorithm == self.algorithm
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bcrypt = self._load_library()
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# Hash the password prior to using bcrypt to prevent password truncation
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# See: https://code.djangoproject.com/ticket/20138
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if self.digest is not None:
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# We use binascii.hexlify here because Python3 decided that a hex encoded
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# bytestring is somehow a unicode.
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password = binascii.hexlify(self.digest(force_bytes(password)).digest())
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else:
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password = force_bytes(password)
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# Ensure that our data is a bytestring
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data = force_bytes(data)
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return constant_time_compare(data, bcrypt.hashpw(password, data))
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def safe_summary(self, encoded):
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algorithm, empty, algostr, work_factor, data = encoded.split('$', 4)
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assert algorithm == self.algorithm
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salt, checksum = data[:22], data[22:]
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return OrderedDict([
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(_('algorithm'), algorithm),
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(_('work factor'), work_factor),
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(_('salt'), mask_hash(salt)),
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(_('checksum'), mask_hash(checksum)),
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])
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class BCryptPasswordHasher(BCryptSHA256PasswordHasher):
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"""
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Secure password hashing using the bcrypt algorithm
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This is considered by many to be the most secure algorithm but you
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must first install the bcrypt library. Please be warned that
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this library depends on native C code and might cause portability
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issues.
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This hasher does not first hash the password which means it is subject to
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the 72 character bcrypt password truncation, most use cases should prefer
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the BCryptSha512PasswordHasher.
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See: https://code.djangoproject.com/ticket/20138
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"""
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algorithm = "bcrypt"
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digest = None
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class SHA1PasswordHasher(BasePasswordHasher):
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"""
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The SHA1 password hashing algorithm (not recommended)
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"""
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algorithm = "sha1"
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def encode(self, password, salt):
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assert password is not None
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assert salt and '$' not in salt
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hash = hashlib.sha1(force_bytes(salt + password)).hexdigest()
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return "%s$%s$%s" % (self.algorithm, salt, hash)
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def verify(self, password, encoded):
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algorithm, salt, hash = encoded.split('$', 2)
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assert algorithm == self.algorithm
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encoded_2 = self.encode(password, salt)
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return constant_time_compare(encoded, encoded_2)
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def safe_summary(self, encoded):
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algorithm, salt, hash = encoded.split('$', 2)
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assert algorithm == self.algorithm
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return OrderedDict([
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(_('algorithm'), algorithm),
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(_('salt'), mask_hash(salt, show=2)),
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(_('hash'), mask_hash(hash)),
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])
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class MD5PasswordHasher(BasePasswordHasher):
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"""
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The Salted MD5 password hashing algorithm (not recommended)
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"""
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algorithm = "md5"
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def encode(self, password, salt):
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assert password is not None
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assert salt and '$' not in salt
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hash = hashlib.md5(force_bytes(salt + password)).hexdigest()
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return "%s$%s$%s" % (self.algorithm, salt, hash)
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def verify(self, password, encoded):
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algorithm, salt, hash = encoded.split('$', 2)
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assert algorithm == self.algorithm
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encoded_2 = self.encode(password, salt)
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return constant_time_compare(encoded, encoded_2)
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def safe_summary(self, encoded):
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algorithm, salt, hash = encoded.split('$', 2)
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assert algorithm == self.algorithm
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return OrderedDict([
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(_('algorithm'), algorithm),
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(_('salt'), mask_hash(salt, show=2)),
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(_('hash'), mask_hash(hash)),
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])
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class UnsaltedSHA1PasswordHasher(BasePasswordHasher):
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"""
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Very insecure algorithm that you should *never* use; stores SHA1 hashes
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with an empty salt.
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This class is implemented because Django used to accept such password
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hashes. Some older Django installs still have these values lingering
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around so we need to handle and upgrade them properly.
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"""
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algorithm = "unsalted_sha1"
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def salt(self):
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return ''
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def encode(self, password, salt):
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assert salt == ''
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hash = hashlib.sha1(force_bytes(password)).hexdigest()
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return 'sha1$$%s' % hash
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def verify(self, password, encoded):
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encoded_2 = self.encode(password, '')
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return constant_time_compare(encoded, encoded_2)
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def safe_summary(self, encoded):
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assert encoded.startswith('sha1$$')
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hash = encoded[6:]
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return OrderedDict([
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(_('algorithm'), self.algorithm),
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(_('hash'), mask_hash(hash)),
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])
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class UnsaltedMD5PasswordHasher(BasePasswordHasher):
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"""
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Incredibly insecure algorithm that you should *never* use; stores unsalted
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MD5 hashes without the algorithm prefix, also accepts MD5 hashes with an
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empty salt.
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This class is implemented because Django used to store passwords this way
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and to accept such password hashes. Some older Django installs still have
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these values lingering around so we need to handle and upgrade them
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properly.
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"""
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algorithm = "unsalted_md5"
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def salt(self):
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return ''
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def encode(self, password, salt):
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assert salt == ''
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return hashlib.md5(force_bytes(password)).hexdigest()
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def verify(self, password, encoded):
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if len(encoded) == 37 and encoded.startswith('md5$$'):
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encoded = encoded[5:]
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encoded_2 = self.encode(password, '')
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return constant_time_compare(encoded, encoded_2)
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def safe_summary(self, encoded):
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return OrderedDict([
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(_('algorithm'), self.algorithm),
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(_('hash'), mask_hash(encoded, show=3)),
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])
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class CryptPasswordHasher(BasePasswordHasher):
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"""
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Password hashing using UNIX crypt (not recommended)
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The crypt module is not supported on all platforms.
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"""
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algorithm = "crypt"
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library = "crypt"
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def salt(self):
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return get_random_string(2)
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def encode(self, password, salt):
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crypt = self._load_library()
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assert len(salt) == 2
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data = crypt.crypt(force_str(password), salt)
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# we don't need to store the salt, but Django used to do this
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return "%s$%s$%s" % (self.algorithm, '', data)
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def verify(self, password, encoded):
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crypt = self._load_library()
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algorithm, salt, data = encoded.split('$', 2)
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assert algorithm == self.algorithm
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return constant_time_compare(data, crypt.crypt(force_str(password), data))
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def safe_summary(self, encoded):
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algorithm, salt, data = encoded.split('$', 2)
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assert algorithm == self.algorithm
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return OrderedDict([
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(_('algorithm'), algorithm),
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(_('salt'), salt),
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(_('hash'), mask_hash(data, show=3)),
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])
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