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import base64
import binascii
import functools
import hashlib
import importlib
import warnings
from collections import OrderedDict
from django.conf import settings
from django.core.exceptions import ImproperlyConfigured
from django.core.signals import setting_changed
from django.dispatch import receiver
from django.utils.crypto import (
constant_time_compare, get_random_string, pbkdf2,
)
from django.utils.module_loading import import_string
from django.utils.translation import gettext_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
def is_password_usable(encoded):
"""
Return True if this password wasn't generated by
User.set_unusable_password(), i.e. make_password(None).
"""
return encoded is None or not encoded.startswith(UNUSABLE_PASSWORD_PREFIX)
def check_password(password, encoded, setter=None, preferred='default'):
"""
Return 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)
try:
hasher = identify_hasher(encoded)
except ValueError:
# encoded is gibberish or uses a hasher that's no longer installed.
return False
hasher_changed = hasher.algorithm != preferred.algorithm
must_update = hasher_changed or preferred.must_update(encoded)
is_correct = hasher.verify(password, encoded)
# If the hasher didn't change (we don't protect against enumeration if it
# does) and the password should get updated, try to close the timing gap
# between the work factor of the current encoded password and the default
# work factor.
if not is_correct and not hasher_changed and must_update:
hasher.harden_runtime(password, encoded)
if setter and is_correct and must_update:
setter(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 generate a new random salt. If password is None then
return a concatenation of UNUSABLE_PASSWORD_PREFIX and a random string,
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)
salt = salt or hasher.salt()
return hasher.encode(password, salt)
@functools.lru_cache()
def get_hashers():
hashers = []
for hasher_path in settings.PASSWORD_HASHERS:
hasher_cls = import_string(hasher_path)
hasher = hasher_cls()
if not getattr(hasher, 'algorithm'):
raise ImproperlyConfigured("hasher doesn't specify an "
"algorithm name: %s" % hasher_path)
hashers.append(hasher)
return hashers
@functools.lru_cache()
def get_hashers_by_algorithm():
return {hasher.algorithm: hasher for hasher in get_hashers()}
@receiver(setting_changed)
def reset_hashers(**kwargs):
if kwargs['setting'] == 'PASSWORD_HASHERS':
get_hashers.cache_clear()
get_hashers_by_algorithm.cache_clear()
def get_hasher(algorithm='default'):
"""
Return an instance of a loaded password hasher.
If algorithm is 'default', return the default hasher. Lazily import hashers
specified in the project's settings file if needed.
"""
if hasattr(algorithm, 'algorithm'):
return algorithm
elif algorithm == 'default':
return get_hashers()[0]
else:
hashers = get_hashers_by_algorithm()
try:
return hashers[algorithm]
except KeyError:
raise ValueError("Unknown password hashing algorithm '%s'. "
"Did you specify it in the PASSWORD_HASHERS "
"setting?" % algorithm)
def identify_hasher(encoded):
"""
Return an instance of a loaded password hasher.
Identify hasher algorithm by examining encoded hash, and call
get_hasher() to return hasher. Raise 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('$', 1)[0]
return get_hasher(algorithm)
def mask_hash(hash, show=6, char="*"):
"""
Return the given hash, with only the first ``show`` number shown. The
rest are masked with ``char`` for security reasons.
"""
masked = hash[:show]
masked += char * len(hash[show:])
return masked
class BasePasswordHasher:
"""
Abstract base class for password hashers
When creating your own hasher, you need to override algorithm,
verify(), encode() and safe_summary().
PasswordHasher objects are immutable.
"""
algorithm = None
library = None
def _load_library(self):
if self.library is not None:
if isinstance(self.library, (tuple, list)):
name, mod_path = self.library
else:
mod_path = self.library
try:
module = importlib.import_module(mod_path)
except ImportError as e:
raise ValueError("Couldn't load %r algorithm library: %s" %
(self.__class__.__name__, e))
return module
raise ValueError("Hasher %r doesn't specify a library attribute" %
self.__class__.__name__)
def salt(self):
"""Generate a cryptographically secure nonce salt in ASCII."""
return get_random_string()
def verify(self, password, encoded):
"""Check if the given password is correct."""
raise NotImplementedError('subclasses of BasePasswordHasher must provide a verify() method')
def encode(self, password, salt):
"""
Create an encoded database value.
The result is normally formatted as "algorithm$salt$hash" and
must be fewer than 128 characters.
"""
raise NotImplementedError('subclasses of BasePasswordHasher must provide an encode() method')
def safe_summary(self, encoded):
"""
Return a summary of safe values.
The result is a dictionary and will be used where the password field
must be displayed to construct a safe representation of the password.
"""
raise NotImplementedError('subclasses of BasePasswordHasher must provide a safe_summary() method')
def must_update(self, encoded):
return False
def harden_runtime(self, password, encoded):
"""
Bridge the runtime gap between the work factor supplied in `encoded`
and the work factor suggested by this hasher.
Taking PBKDF2 as an example, if `encoded` contains 20000 iterations and
`self.iterations` is 30000, this method should run password through
another 10000 iterations of PBKDF2. Similar approaches should exist
for any hasher that has a work factor. If not, this method should be
defined as a no-op to silence the warning.
"""
warnings.warn('subclasses of BasePasswordHasher should provide a harden_runtime() method')
class PBKDF2PasswordHasher(BasePasswordHasher):
"""
Secure password hashing using the PBKDF2 algorithm (recommended)
Configured to use PBKDF2 + HMAC + SHA256.
The result is a 64 byte binary string. Iterations may be changed
safely but you must rename the algorithm if you change SHA256.
"""
algorithm = "pbkdf2_sha256"
iterations = 150000
digest = hashlib.sha256
def encode(self, password, salt, iterations=None):
assert password is not None
assert salt and '$' not in salt
iterations = iterations or 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
def harden_runtime(self, password, encoded):
algorithm, iterations, salt, hash = encoded.split('$', 3)
extra_iterations = self.iterations - int(iterations)
if extra_iterations > 0:
self.encode(password, salt, extra_iterations)
class PBKDF2SHA1PasswordHasher(PBKDF2PasswordHasher):
"""
Alternate PBKDF2 hasher which uses SHA1, the default PRF
recommended by PKCS #5. This is compatible with other
implementations of PBKDF2, such as openssl's
PKCS5_PBKDF2_HMAC_SHA1().
"""
algorithm = "pbkdf2_sha1"
digest = hashlib.sha1
class Argon2PasswordHasher(BasePasswordHasher):
"""
Secure password hashing using the argon2 algorithm.
This is the winner of the Password Hashing Competition 2013-2015
(https://password-hashing.net). It requires the argon2-cffi library which
depends on native C code and might cause portability issues.
"""
algorithm = 'argon2'
library = 'argon2'
time_cost = 2
memory_cost = 512
parallelism = 2
def encode(self, password, salt):
argon2 = self._load_library()
data = argon2.low_level.hash_secret(
password.encode(),
salt.encode(),
time_cost=self.time_cost,
memory_cost=self.memory_cost,
parallelism=self.parallelism,
hash_len=argon2.DEFAULT_HASH_LENGTH,
type=argon2.low_level.Type.I,
)
return self.algorithm + data.decode('ascii')
def verify(self, password, encoded):
argon2 = self._load_library()
algorithm, rest = encoded.split('$', 1)
assert algorithm == self.algorithm
try:
return argon2.low_level.verify_secret(
('$' + rest).encode('ascii'),
password.encode(),
type=argon2.low_level.Type.I,
)
except argon2.exceptions.VerificationError:
return False
def safe_summary(self, encoded):
(algorithm, variety, version, time_cost, memory_cost, parallelism,
salt, data) = self._decode(encoded)
assert algorithm == self.algorithm
return OrderedDict([
(_('algorithm'), algorithm),
(_('variety'), variety),
(_('version'), version),
(_('memory cost'), memory_cost),
(_('time cost'), time_cost),
(_('parallelism'), parallelism),
(_('salt'), mask_hash(salt)),
(_('hash'), mask_hash(data)),
])
def must_update(self, encoded):
(algorithm, variety, version, time_cost, memory_cost, parallelism,
salt, data) = self._decode(encoded)
assert algorithm == self.algorithm
argon2 = self._load_library()
return (
argon2.low_level.ARGON2_VERSION != version or
self.time_cost != time_cost or
self.memory_cost != memory_cost or
self.parallelism != parallelism
)
def harden_runtime(self, password, encoded):
# The runtime for Argon2 is too complicated to implement a sensible
# hardening algorithm.
pass
def _decode(self, encoded):
"""
Split an encoded hash and return: (
algorithm, variety, version, time_cost, memory_cost,
parallelism, salt, data,
).
"""
bits = encoded.split('$')
if len(bits) == 5:
# Argon2 < 1.3
algorithm, variety, raw_params, salt, data = bits
version = 0x10
else:
assert len(bits) == 6
algorithm, variety, raw_version, raw_params, salt, data = bits
assert raw_version.startswith('v=')
version = int(raw_version[len('v='):])
params = dict(bit.split('=', 1) for bit in raw_params.split(','))
assert len(params) == 3 and all(x in params for x in ('t', 'm', 'p'))
time_cost = int(params['t'])
memory_cost = int(params['m'])
parallelism = int(params['p'])
return (
algorithm, variety, version, time_cost, memory_cost, parallelism,
salt, data,
)
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()
password = password.encode()
# Hash the password prior to using bcrypt to prevent password
# truncation as described in #20138.
if self.digest is not None:
# Use binascii.hexlify() because a hex encoded bytestring is str.
password = binascii.hexlify(self.digest(password).digest())
data = bcrypt.hashpw(password, salt)
return "%s$%s" % (self.algorithm, data.decode('ascii'))
def verify(self, password, encoded):
algorithm, data = encoded.split('$', 1)
assert algorithm == self.algorithm
encoded_2 = self.encode(password, data.encode('ascii'))
return constant_time_compare(encoded, encoded_2)
def safe_summary(self, encoded):
algorithm, empty, algostr, work_factor, data = encoded.split('$', 4)
assert algorithm == self.algorithm
salt, checksum = data[:22], data[22:]
return OrderedDict([
(_('algorithm'), algorithm),
(_('work factor'), work_factor),
(_('salt'), mask_hash(salt)),
(_('checksum'), mask_hash(checksum)),
])
def must_update(self, encoded):
algorithm, empty, algostr, rounds, data = encoded.split('$', 4)
return int(rounds) != self.rounds
def harden_runtime(self, password, encoded):
_, data = encoded.split('$', 1)
salt = data[:29] # Length of the salt in bcrypt.
rounds = data.split('$')[2]
# work factor is logarithmic, adding one doubles the load.
diff = 2**(self.rounds - int(rounds)) - 1
while diff > 0:
self.encode(password, salt.encode('ascii'))
diff -= 1
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
bcrypt's 72 bytes password truncation. Most use cases should prefer the
BCryptSHA256PasswordHasher.
"""
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 '$' not in salt
hash = hashlib.sha1((salt + password).encode()).hexdigest()
return "%s$%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('$', 2)
assert algorithm == self.algorithm
return OrderedDict([
(_('algorithm'), algorithm),
(_('salt'), mask_hash(salt, show=2)),
(_('hash'), mask_hash(hash)),
])
def harden_runtime(self, password, encoded):
pass
class MD5PasswordHasher(BasePasswordHasher):
"""
The Salted MD5 password hashing algorithm (not recommended)
"""
algorithm = "md5"
def encode(self, password, salt):
assert password is not None
assert salt and '$' not in salt
hash = hashlib.md5((salt + password).encode()).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)),
])
def harden_runtime(self, password, encoded):
pass
class UnsaltedSHA1PasswordHasher(BasePasswordHasher):
"""
Very insecure algorithm that you should *never* use; store 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(password.encode()).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)),
])
def harden_runtime(self, password, encoded):
pass
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(password.encode()).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)),
])
def harden_runtime(self, password, encoded):
pass
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)
assert data is not None # A platform like OpenBSD with a dummy crypt module.
# 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 OrderedDict([
(_('algorithm'), algorithm),
(_('salt'), salt),
(_('hash'), mask_hash(data, show=3)),
])
def harden_runtime(self, password, encoded):
pass