Source code for django.contrib.auth.hashers

from __future__ import unicode_literals

import base64
import binascii
from collections import OrderedDict
import hashlib
import importlib

from django.dispatch import receiver
from django.conf import settings
from django.test.signals import setting_changed
from django.utils.encoding import force_bytes, force_str, force_text
from django.core.exceptions import ImproperlyConfigured
from django.utils.crypto import (
    pbkdf2, constant_time_compare, get_random_string)
from django.utils.module_loading import import_string
from django.utils.translation import ugettext_noop as _


UNUSABLE_PASSWORD_PREFIX = '!'  # This will never be a valid encoded hash
UNUSABLE_PASSWORD_SUFFIX_LENGTH = 40  # number of random chars to add after UNUSABLE_PASSWORD_PREFIX
HASHERS = None  # lazily loaded from PASSWORD_HASHERS
PREFERRED_HASHER = None  # defaults to first item in PASSWORD_HASHERS


@receiver(setting_changed)
def reset_hashers(**kwargs):
    if kwargs['setting'] == 'PASSWORD_HASHERS':
        global HASHERS, PREFERRED_HASHER
        HASHERS = None
        PREFERRED_HASHER = None


[docs]def is_password_usable(encoded): if encoded is None or encoded.startswith(UNUSABLE_PASSWORD_PREFIX): return False try: identify_hasher(encoded) except ValueError: return False return True
[docs]def check_password(password, encoded, setter=None, preferred='default'): """ Returns a boolean of whether the raw password matches the three part encoded digest. If setter is specified, it'll be called when you need to regenerate the password. """ if password is None or not is_password_usable(encoded): return False preferred = get_hasher(preferred) hasher = identify_hasher(encoded) must_update = hasher.algorithm != preferred.algorithm if not must_update: must_update = preferred.must_update(encoded) is_correct = hasher.verify(password, encoded) if setter and is_correct and must_update: setter(password) return is_correct
[docs]def make_password(password, salt=None, hasher='default'): """ Turn a plain-text password into a hash for database storage Same as encode() but generates a new random salt. If password is None then a concatenation of UNUSABLE_PASSWORD_PREFIX and a random string will be returned which disallows logins. Additional random string reduces chances of gaining access to staff or superuser accounts. See ticket #20079 for more info. """ if password is None: return UNUSABLE_PASSWORD_PREFIX + get_random_string(UNUSABLE_PASSWORD_SUFFIX_LENGTH) hasher = get_hasher(hasher) if not salt: salt = hasher.salt() return hasher.encode(password, salt)
def load_hashers(password_hashers=None): global HASHERS global PREFERRED_HASHER hashers = [] if not password_hashers: password_hashers = settings.PASSWORD_HASHERS for backend in password_hashers: hasher = import_string(backend)() if not getattr(hasher, 'algorithm'): raise ImproperlyConfigured("hasher doesn't specify an " "algorithm name: %s" % backend) hashers.append(hasher) HASHERS = dict((hasher.algorithm, hasher) for hasher in hashers) PREFERRED_HASHER = hashers[0] def get_hasher(algorithm='default'): """ Returns an instance of a loaded password hasher. If algorithm is 'default', the default hasher will be returned. This function will also lazy import hashers specified in your settings file if needed. """ if hasattr(algorithm, 'algorithm'): return algorithm elif algorithm == 'default': if PREFERRED_HASHER is None: load_hashers() return PREFERRED_HASHER else: if HASHERS is None: load_hashers() if algorithm not in HASHERS: raise ValueError("Unknown password hashing algorithm '%s'. " "Did you specify it in the PASSWORD_HASHERS " "setting?" % algorithm) return HASHERS[algorithm] def identify_hasher(encoded): """ Returns an instance of a loaded password hasher. Identifies hasher algorithm by examining encoded hash, and calls get_hasher() to return hasher. Raises ValueError if algorithm cannot be identified, or if hasher is not loaded. """ # Ancient versions of Django created plain MD5 passwords and accepted # MD5 passwords with an empty salt. if ((len(encoded) == 32 and '$' not in encoded) or (len(encoded) == 37 and encoded.startswith('md5$$'))): algorithm = 'unsalted_md5' # Ancient versions of Django accepted SHA1 passwords with an empty salt. elif len(encoded) == 46 and encoded.startswith('sha1$$'): algorithm = 'unsalted_sha1' else: algorithm = encoded.split('$', 1)[0] return get_hasher(algorithm) def mask_hash(hash, show=6, char="*"): """ Returns the given hash, with only the first ``show`` number shown. The rest are masked with ``char`` for security reasons. """ masked = hash[:show] masked += char * len(hash[show:]) return masked class BasePasswordHasher(object): """ Abstract base class for password hashers When creating your own hasher, you need to override algorithm, verify(), encode() and safe_summary(). PasswordHasher objects are immutable. """ algorithm = None library = None def _load_library(self): if self.library is not None: if isinstance(self.library, (tuple, list)): name, mod_path = self.library else: mod_path = self.library try: module = importlib.import_module(mod_path) except ImportError as e: raise ValueError("Couldn't load %r algorithm library: %s" % (self.__class__.__name__, e)) return module raise ValueError("Hasher %r doesn't specify a library attribute" % self.__class__.__name__) def salt(self): """ Generates a cryptographically secure nonce salt in ASCII """ return get_random_string() def verify(self, password, encoded): """ Checks if the given password is correct """ raise NotImplementedError('subclasses of BasePasswordHasher must provide a verify() method') def encode(self, password, salt): """ Creates an encoded database value The result is normally formatted as "algorithm$salt$hash" and must be fewer than 128 characters. """ raise NotImplementedError('subclasses of BasePasswordHasher must provide an encode() method') def safe_summary(self, encoded): """ Returns a summary of safe values The result is a dictionary and will be used where the password field must be displayed to construct a safe representation of the password. """ raise NotImplementedError('subclasses of BasePasswordHasher must provide a safe_summary() method') def must_update(self, encoded): return False class PBKDF2PasswordHasher(BasePasswordHasher): """ Secure password hashing using the PBKDF2 algorithm (recommended) Configured to use PBKDF2 + HMAC + SHA256 with 15000 iterations. The result is a 64 byte binary string. Iterations may be changed safely but you must rename the algorithm if you change SHA256. """ algorithm = "pbkdf2_sha256" iterations = 15000 digest = hashlib.sha256 def encode(self, password, salt, iterations=None): assert password is not None assert salt and '$' not in salt if not iterations: iterations = self.iterations hash = pbkdf2(password, salt, iterations, digest=self.digest) hash = base64.b64encode(hash).decode('ascii').strip() return "%s$%d$%s$%s" % (self.algorithm, iterations, salt, hash) def verify(self, password, encoded): algorithm, iterations, salt, hash = encoded.split('$', 3) assert algorithm == self.algorithm encoded_2 = self.encode(password, salt, int(iterations)) return constant_time_compare(encoded, encoded_2) def safe_summary(self, encoded): algorithm, iterations, salt, hash = encoded.split('$', 3) assert algorithm == self.algorithm return OrderedDict([ (_('algorithm'), algorithm), (_('iterations'), iterations), (_('salt'), mask_hash(salt)), (_('hash'), mask_hash(hash)), ]) def must_update(self, encoded): algorithm, iterations, salt, hash = encoded.split('$', 3) return int(iterations) != self.iterations class PBKDF2SHA1PasswordHasher(PBKDF2PasswordHasher): """ Alternate PBKDF2 hasher which uses SHA1, the default PRF recommended by PKCS #5. This is compatible with other implementations of PBKDF2, such as openssl's PKCS5_PBKDF2_HMAC_SHA1(). """ algorithm = "pbkdf2_sha1" digest = hashlib.sha1 class BCryptSHA256PasswordHasher(BasePasswordHasher): """ Secure password hashing using the bcrypt algorithm (recommended) This is considered by many to be the most secure algorithm but you must first install the bcrypt library. Please be warned that this library depends on native C code and might cause portability issues. """ algorithm = "bcrypt_sha256" digest = hashlib.sha256 library = ("bcrypt", "bcrypt") rounds = 12 def salt(self): bcrypt = self._load_library() return bcrypt.gensalt(self.rounds) def encode(self, password, salt): bcrypt = self._load_library() # Need to reevaluate the force_bytes call once bcrypt is supported on # Python 3 # Hash the password prior to using bcrypt to prevent password truncation # See: https://code.djangoproject.com/ticket/20138 if self.digest is not None: # We use binascii.hexlify here because Python3 decided that a hex encoded # bytestring is somehow a unicode. password = binascii.hexlify(self.digest(force_bytes(password)).digest()) else: password = force_bytes(password) data = bcrypt.hashpw(password, salt) return "%s$%s" % (self.algorithm, force_text(data)) def verify(self, password, encoded): algorithm, data = encoded.split('$', 1) assert algorithm == self.algorithm bcrypt = self._load_library() # Hash the password prior to using bcrypt to prevent password truncation # See: https://code.djangoproject.com/ticket/20138 if self.digest is not None: # We use binascii.hexlify here because Python3 decided that a hex encoded # bytestring is somehow a unicode. password = binascii.hexlify(self.digest(force_bytes(password)).digest()) else: password = force_bytes(password) # Ensure that our data is a bytestring data = force_bytes(data) # force_bytes() necessary for py-bcrypt compatibility hashpw = force_bytes(bcrypt.hashpw(password, data)) return constant_time_compare(data, hashpw) def safe_summary(self, encoded): algorithm, empty, algostr, work_factor, data = encoded.split('$', 4) assert algorithm == self.algorithm salt, checksum = data[:22], data[22:] return OrderedDict([ (_('algorithm'), algorithm), (_('work factor'), work_factor), (_('salt'), mask_hash(salt)), (_('checksum'), mask_hash(checksum)), ]) class BCryptPasswordHasher(BCryptSHA256PasswordHasher): """ Secure password hashing using the bcrypt algorithm This is considered by many to be the most secure algorithm but you must first install the bcrypt library. Please be warned that this library depends on native C code and might cause portability issues. This hasher does not first hash the password which means it is subject to the 72 character bcrypt password truncation, most use cases should prefer the BCryptSha512PasswordHasher. See: https://code.djangoproject.com/ticket/20138 """ algorithm = "bcrypt" digest = None class SHA1PasswordHasher(BasePasswordHasher): """ The SHA1 password hashing algorithm (not recommended) """ algorithm = "sha1" def encode(self, password, salt): assert password is not None assert salt and '$' not in salt hash = hashlib.sha1(force_bytes(salt + password)).hexdigest() return "%s$%s$%s" % (self.algorithm, salt, hash) def verify(self, password, encoded): algorithm, salt, hash = encoded.split('$', 2) assert algorithm == self.algorithm encoded_2 = self.encode(password, salt) return constant_time_compare(encoded, encoded_2) def safe_summary(self, encoded): algorithm, salt, hash = encoded.split('$', 2) assert algorithm == self.algorithm return OrderedDict([ (_('algorithm'), algorithm), (_('salt'), mask_hash(salt, show=2)), (_('hash'), mask_hash(hash)), ]) class MD5PasswordHasher(BasePasswordHasher): """ The Salted MD5 password hashing algorithm (not recommended) """ algorithm = "md5" def encode(self, password, salt): assert password is not None assert salt and '$' not in salt hash = hashlib.md5(force_bytes(salt + password)).hexdigest() return "%s$%s$%s" % (self.algorithm, salt, hash) def verify(self, password, encoded): algorithm, salt, hash = encoded.split('$', 2) assert algorithm == self.algorithm encoded_2 = self.encode(password, salt) return constant_time_compare(encoded, encoded_2) def safe_summary(self, encoded): algorithm, salt, hash = encoded.split('$', 2) assert algorithm == self.algorithm return OrderedDict([ (_('algorithm'), algorithm), (_('salt'), mask_hash(salt, show=2)), (_('hash'), mask_hash(hash)), ]) class UnsaltedSHA1PasswordHasher(BasePasswordHasher): """ Very insecure algorithm that you should *never* use; stores SHA1 hashes with an empty salt. This class is implemented because Django used to accept such password hashes. Some older Django installs still have these values lingering around so we need to handle and upgrade them properly. """ algorithm = "unsalted_sha1" def salt(self): return '' def encode(self, password, salt): assert salt == '' hash = hashlib.sha1(force_bytes(password)).hexdigest() return 'sha1$$%s' % hash def verify(self, password, encoded): encoded_2 = self.encode(password, '') return constant_time_compare(encoded, encoded_2) def safe_summary(self, encoded): assert encoded.startswith('sha1$$') hash = encoded[6:] return OrderedDict([ (_('algorithm'), self.algorithm), (_('hash'), mask_hash(hash)), ]) class UnsaltedMD5PasswordHasher(BasePasswordHasher): """ Incredibly insecure algorithm that you should *never* use; stores unsalted MD5 hashes without the algorithm prefix, also accepts MD5 hashes with an empty salt. This class is implemented because Django used to store passwords this way and to accept such password hashes. Some older Django installs still have these values lingering around so we need to handle and upgrade them properly. """ algorithm = "unsalted_md5" def salt(self): return '' def encode(self, password, salt): assert salt == '' return hashlib.md5(force_bytes(password)).hexdigest() def verify(self, password, encoded): if len(encoded) == 37 and encoded.startswith('md5$$'): encoded = encoded[5:] encoded_2 = self.encode(password, '') return constant_time_compare(encoded, encoded_2) def safe_summary(self, encoded): return OrderedDict([ (_('algorithm'), self.algorithm), (_('hash'), mask_hash(encoded, show=3)), ]) class CryptPasswordHasher(BasePasswordHasher): """ Password hashing using UNIX crypt (not recommended) The crypt module is not supported on all platforms. """ algorithm = "crypt" library = "crypt" def salt(self): return get_random_string(2) def encode(self, password, salt): crypt = self._load_library() assert len(salt) == 2 data = crypt.crypt(force_str(password), salt) # we don't need to store the salt, but Django used to do this return "%s$%s$%s" % (self.algorithm, '', data) def verify(self, password, encoded): crypt = self._load_library() algorithm, salt, data = encoded.split('$', 2) assert algorithm == self.algorithm return constant_time_compare(data, crypt.crypt(force_str(password), data)) def safe_summary(self, encoded): algorithm, salt, data = encoded.split('$', 2) assert algorithm == self.algorithm return OrderedDict([ (_('algorithm'), algorithm), (_('salt'), salt), (_('hash'), mask_hash(data, show=3)), ])
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