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+import hashlib
+
+from django.conf import settings
+from django.utils import importlib
+from django.utils.datastructures import SortedDict
+from django.utils.encoding import smart_str
+from django.core.exceptions import ImproperlyConfigured
+from django.utils.crypto import (
+ pbkdf2, constant_time_compare, get_random_string)
+
+
+UNUSABLE_PASSWORD = '!' # This will never be a valid encoded hash
+HASHERS = None # lazily loaded from PASSWORD_HASHERS
+PREFERRED_HASHER = None # defaults to first item in PASSWORD_HASHERS
+
+
+def is_password_usable(encoded):
+ return (encoded is not None and encoded != UNUSABLE_PASSWORD)
+
+
+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 not password or not is_password_usable(encoded):
+ return False
+
+ preferred = get_hasher(preferred)
+ raw_password = password
+ password = smart_str(password)
+ encoded = smart_str(encoded)
+
+ if len(encoded) == 32 and '$' not in encoded:
+ hasher = get_hasher('md5')
+ else:
+ algorithm = encoded.split('$', 1)[0]
+ hasher = get_hasher(algorithm)
+
+ must_update = hasher.algorithm != preferred.algorithm
+ is_correct = hasher.verify(password, encoded)
+ if setter and is_correct and must_update:
+ setter(raw_password)
+ return is_correct
+
+
+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 or blank then UNUSABLE_PASSWORD will be
+ returned which disallows logins.
+ """
+ if not password:
@bmispelon
bmispelon Jun 12, 2013 Django member

Was this backwards-incompatible change introduced on purpose?

See the discussion on ticket #20593 (https://code.djangoproject.com/ticket/20593)

@PaulMcMillan
PaulMcMillan Jun 13, 2013 collaborator

Nope, that wasn't intentional - I've replied to your ticket as well, but I agree that should be "if password is None"...

+ return UNUSABLE_PASSWORD
+
+ hasher = get_hasher(hasher)
+ password = smart_str(password)
+
+ if not salt:
+ salt = hasher.salt()
+ salt = smart_str(salt)
+
+ return hasher.encode(password, salt)
+
+
+def load_hashers():
+ global HASHERS
+ global PREFERRED_HASHER
+ hashers = []
+ for backend in settings.PASSWORD_HASHERS:
+ try:
+ mod_path, cls_name = backend.rsplit('.', 1)
+ mod = importlib.import_module(mod_path)
+ hasher_cls = getattr(mod, cls_name)
+ except (AttributeError, ImportError, ValueError):
+ raise ImproperlyConfigured("hasher not found: %s" % backend)
+ hasher = hasher_cls()
+ 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 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:
+ name = mod_path = self.library
+ try:
+ module = importlib.import_module(mod_path)
+ except ImportError:
+ raise ValueError("Couldn't load %s password algorithm "
+ "library" % name)
+ return module
+ raise ValueError("Hasher '%s' doesn't specify a library attribute" %
+ self.__class__)
+
+ 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()
+
+ 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()
+
+ 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()
+
+
+class PBKDF2PasswordHasher(BasePasswordHasher):
+ """
+ Secure password hashing using the PBKDF2 algorithm (recommended)
+
+ Configured to use PBKDF2 + HMAC + SHA256 with 10000 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 = 10000
+ digest = hashlib.sha256
+
+ def encode(self, password, salt, iterations=None):
+ assert password
+ assert salt and '$' not in salt
+ if not iterations:
+ iterations = self.iterations
+ hash = pbkdf2(password, salt, iterations, digest=self.digest)
+ hash = hash.encode('base64').strip()
+ return "%s$%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 SortedDict([
+ ('algorithm', algorithm),
+ ('iterations', iterations),
+ ('salt', mask_hash(salt)),
+ ('hash', mask_hash(hash)),
+ ])
+
+
+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 BCryptPasswordHasher(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 py-bcrypt library. Please be warned that
+ this library depends on native C code and might cause portability
+ issues.
+ """
+ algorithm = "bcrypt"
+ library = ("py-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()
+ data = bcrypt.hashpw(password, salt)
+ return "%s$%s" % (self.algorithm, data)
+
+ def verify(self, password, encoded):
+ algorithm, data = encoded.split('$', 1)
+ assert algorithm == self.algorithm
+ bcrypt = self._load_library()
+ return constant_time_compare(data, bcrypt.hashpw(password, data))
+
+ def safe_summary(self, encoded):
+ algorithm, empty, algostr, work_factor, data = encoded.split('$', 4)
+ assert algorithm == self.algorithm
+ salt, checksum = data[:22], data[22:]
+ return SortedDict([
+ ('algorithm', algorithm),
+ ('work factor', work_factor),
+ ('salt', mask_hash(salt)),
+ ('checksum', mask_hash(checksum)),
+ ])
+
+
+class SHA1PasswordHasher(BasePasswordHasher):
+ """
+ The SHA1 password hashing algorithm (not recommended)
+ """
+ algorithm = "sha1"
+
+ def encode(self, password, salt):
+ assert password
+ assert salt and '$' not in salt
+ hash = hashlib.sha1(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 SortedDict([
+ ('algorithm', algorithm),
+ ('salt', mask_hash(salt, show=2)),
+ ('hash', mask_hash(hash)),
+ ])
+
+
+class MD5PasswordHasher(BasePasswordHasher):
+ """
+ I am an incredibly insecure algorithm you should *never* use;
+ stores unsalted MD5 hashes without the algorithm prefix.
+
+ This class is implemented because Django used to store passwords
+ this way. Some older Django installs still have these values
+ lingering around so we need to handle and upgrade them properly.
+ """
+ algorithm = "md5"
+
+ def salt(self):
+ return ''
+
+ def encode(self, password, salt):
+ return hashlib.md5(password).hexdigest()
+
+ def verify(self, password, encoded):
+ encoded_2 = self.encode(password, '')
+ return constant_time_compare(encoded, encoded_2)
+
+ def safe_summary(self, encoded):
+ return SortedDict([
+ ('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(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('$', 2)
+ assert algorithm == self.algorithm
+ return constant_time_compare(data, crypt.crypt(password, data))
+
+ def safe_summary(self, encoded):
+ algorithm, salt, data = encoded.split('$', 2)
+ assert algorithm == self.algorithm
+ return SortedDict([
+ ('algorithm', algorithm),
+ ('salt', salt),
+ ('hash', mask_hash(data, show=3)),
+ ])
+
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