# Django 4.2.11 documentation

# Source code for django.contrib.auth.hashers

    import base64
    import binascii
    import functools
    import hashlib
    import importlib
    import math
    import warnings

    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 (
        RANDOM_STRING_CHARS,
        constant_time_compare,
        get_random_string,
        md5,
        pbkdf2,
    )
    from django.utils.deprecation import RemovedInDjango50Warning, RemovedInDjango51Warning
    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.
        """
        fake_runtime = password is None or not is_password_usable(encoded)

        preferred = get_hasher(preferred)
        try:
            hasher = identify_hasher(encoded)
        except ValueError:
            # encoded is gibberish or uses a hasher that's no longer installed.
            fake_runtime = True

        if fake_runtime:
            # Run the default password hasher once to reduce the timing difference
            # between an existing user with an unusable password and a nonexistent
            # user or missing hasher (similar to #20760).
            make_password(get_random_string(UNUSABLE_PASSWORD_SUFFIX_LENGTH))
            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
            )
        if not isinstance(password, (bytes, str)):
            raise TypeError(
                "Password must be a string or bytes, got %s." % type(password).__qualname__
            )
        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(*, setting, **kwargs):
        if 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

    def must_update_salt(salt, expected_entropy):
        # Each character in the salt provides log_2(len(alphabet)) bits of entropy.
        return len(salt) * math.log2(len(RANDOM_STRING_CHARS)) < expected_entropy

    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
        salt_entropy = 128

        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 with an entropy
            of at least `salt_entropy` bits.
            """
            # Each character in the salt provides
            # log_2(len(alphabet)) bits of entropy.
            char_count = math.ceil(self.salt_entropy / math.log2(len(RANDOM_STRING_CHARS)))
            return get_random_string(char_count, allowed_chars=RANDOM_STRING_CHARS)

        def verify(self, password, encoded):
            """Check if the given password is correct."""
            raise NotImplementedError(
                "subclasses of BasePasswordHasher must provide a verify() method"
            )

        def _check_encode_args(self, password, salt):
            if password is None:
                raise TypeError("password must be provided.")
            if not salt or "$" in salt:
                raise ValueError("salt must be provided and cannot contain $.")

        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 decode(self, encoded):
            """
            Return a decoded database value.

            The result is a dictionary and should contain `algorithm`, `hash`, and
            `salt`. Extra keys can be algorithm specific like `iterations` or
            `work_factor`.
            """
            raise NotImplementedError(
                "subclasses of BasePasswordHasher must provide a decode() 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 = 600000
        digest = hashlib.sha256

        def encode(self, password, salt, iterations=None):
            self._check_encode_args(password, 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 decode(self, encoded):
            algorithm, iterations, salt, hash = encoded.split("$", 3)
            assert algorithm == self.algorithm
            return {
                "algorithm": algorithm,
                "hash": hash,
                "iterations": int(iterations),
                "salt": salt,
            }

        def verify(self, password, encoded):
            decoded = self.decode(encoded)
            encoded_2 = self.encode(password, decoded["salt"], decoded["iterations"])
            return constant_time_compare(encoded, encoded_2)

        def safe_summary(self, encoded):
            decoded = self.decode(encoded)
            return {
                _("algorithm"): decoded["algorithm"],
                _("iterations"): decoded["iterations"],
                _("salt"): mask_hash(decoded["salt"]),
                _("hash"): mask_hash(decoded["hash"]),
            }

        def must_update(self, encoded):
            decoded = self.decode(encoded)
            update_salt = must_update_salt(decoded["salt"], self.salt_entropy)
            return (decoded["iterations"] != self.iterations) or update_salt

        def harden_runtime(self, password, encoded):
            decoded = self.decode(encoded)
            extra_iterations = self.iterations - decoded["iterations"]
            if extra_iterations > 0:
                self.encode(password, decoded["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 = 102400
        parallelism = 8

        def encode(self, password, salt):
            argon2 = self._load_library()
            params = self.params()
            data = argon2.low_level.hash_secret(
                password.encode(),
                salt.encode(),
                time_cost=params.time_cost,
                memory_cost=params.memory_cost,
                parallelism=params.parallelism,
                hash_len=params.hash_len,
                type=params.type,
            )
            return self.algorithm + data.decode("ascii")

        def decode(self, encoded):
            argon2 = self._load_library()
            algorithm, rest = encoded.split("$", 1)
            assert algorithm == self.algorithm
            params = argon2.extract_parameters("$" + rest)
            variety, *_, b64salt, hash = rest.split("$")
            # Add padding.
            b64salt += "=" * (-len(b64salt) % 4)
            salt = base64.b64decode(b64salt).decode("latin1")
            return {
                "algorithm": algorithm,
                "hash": hash,
                "memory_cost": params.memory_cost,
                "parallelism": params.parallelism,
                "salt": salt,
                "time_cost": params.time_cost,
                "variety": variety,
                "version": params.version,
                "params": params,
            }

        def verify(self, password, encoded):
            argon2 = self._load_library()
            algorithm, rest = encoded.split("$", 1)
            assert algorithm == self.algorithm
            try:
                return argon2.PasswordHasher().verify("$" + rest, password)
            except argon2.exceptions.VerificationError:
                return False

        def safe_summary(self, encoded):
            decoded = self.decode(encoded)
            return {
                _("algorithm"): decoded["algorithm"],
                _("variety"): decoded["variety"],
                _("version"): decoded["version"],
                _("memory cost"): decoded["memory_cost"],
                _("time cost"): decoded["time_cost"],
                _("parallelism"): decoded["parallelism"],
                _("salt"): mask_hash(decoded["salt"]),
                _("hash"): mask_hash(decoded["hash"]),
            }

        def must_update(self, encoded):
            decoded = self.decode(encoded)
            current_params = decoded["params"]
            new_params = self.params()
            # Set salt_len to the salt_len of the current parameters because salt
            # is explicitly passed to argon2.
            new_params.salt_len = current_params.salt_len
            update_salt = must_update_salt(decoded["salt"], self.salt_entropy)
            return (current_params != new_params) or update_salt

        def harden_runtime(self, password, encoded):
            # The runtime for Argon2 is too complicated to implement a sensible
            # hardening algorithm.
            pass

        def params(self):
            argon2 = self._load_library()
            # salt_len is a noop, because we provide our own salt.
            return argon2.Parameters(
                type=argon2.low_level.Type.ID,
                version=argon2.low_level.ARGON2_VERSION,
                salt_len=argon2.DEFAULT_RANDOM_SALT_LENGTH,
                hash_len=argon2.DEFAULT_HASH_LENGTH,
                time_cost=self.time_cost,
                memory_cost=self.memory_cost,
                parallelism=self.parallelism,
            )

    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 decode(self, encoded):
            algorithm, empty, algostr, work_factor, data = encoded.split("$", 4)
            assert algorithm == self.algorithm
            return {
                "algorithm": algorithm,
                "algostr": algostr,
                "checksum": data[22:],
                "salt": data[:22],
                "work_factor": int(work_factor),
            }

        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):
            decoded = self.decode(encoded)
            return {
                _("algorithm"): decoded["algorithm"],
                _("work factor"): decoded["work_factor"],
                _("salt"): mask_hash(decoded["salt"]),
                _("checksum"): mask_hash(decoded["checksum"]),
            }

        def must_update(self, encoded):
            decoded = self.decode(encoded)
            return decoded["work_factor"] != 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 ScryptPasswordHasher(BasePasswordHasher):
        """
        Secure password hashing using the Scrypt algorithm.
        """

        algorithm = "scrypt"
        block_size = 8
        maxmem = 0
        parallelism = 1
        work_factor = 2**14

        def encode(self, password, salt, n=None, r=None, p=None):
            self._check_encode_args(password, salt)
            n = n or self.work_factor
            r = r or self.block_size
            p = p or self.parallelism
            hash_ = hashlib.scrypt(
                password.encode(),
                salt=salt.encode(),
                n=n,
                r=r,
                p=p,
                maxmem=self.maxmem,
                dklen=64,
            )
            hash_ = base64.b64encode(hash_).decode("ascii").strip()
            return "%s$%d$%s$%d$%d$%s" % (self.algorithm, n, salt, r, p, hash_)

        def decode(self, encoded):
            algorithm, work_factor, salt, block_size, parallelism, hash_ = encoded.split(
                "$", 6
            )
            assert algorithm == self.algorithm
            return {
                "algorithm": algorithm,
                "work_factor": int(work_factor),
                "salt": salt,
                "block_size": int(block_size),
                "parallelism": int(parallelism),
                "hash": hash_,
            }

        def verify(self, password, encoded):
            decoded = self.decode(encoded)
            encoded_2 = self.encode(
                password,
                decoded["salt"],
                decoded["work_factor"],
                decoded["block_size"],
                decoded["parallelism"],
            )
            return constant_time_compare(encoded, encoded_2)

        def safe_summary(self, encoded):
            decoded = self.decode(encoded)
            return {
                _("algorithm"): decoded["algorithm"],
                _("work factor"): decoded["work_factor"],
                _("block size"): decoded["block_size"],
                _("parallelism"): decoded["parallelism"],
                _("salt"): mask_hash(decoded["salt"]),
                _("hash"): mask_hash(decoded["hash"]),
            }

        def must_update(self, encoded):
            decoded = self.decode(encoded)
            return (
                decoded["work_factor"] != self.work_factor
                or decoded["block_size"] != self.block_size
                or decoded["parallelism"] != self.parallelism
            )

        def harden_runtime(self, password, encoded):
            # The runtime for Scrypt is too complicated to implement a sensible
            # hardening algorithm.
            pass

    # RemovedInDjango51Warning.
    class SHA1PasswordHasher(BasePasswordHasher):
        """
        The SHA1 password hashing algorithm (not recommended)
        """

        algorithm = "sha1"

        def __init__(self, *args, **kwargs):
            warnings.warn(
                "django.contrib.auth.hashers.SHA1PasswordHasher is deprecated.",
                RemovedInDjango51Warning,
                stacklevel=2,
            )
            super().__init__(*args, **kwargs)

        def encode(self, password, salt):
            self._check_encode_args(password, salt)
            hash = hashlib.sha1((salt + password).encode()).hexdigest()
            return "%s$%s$%s" % (self.algorithm, salt, hash)

        def decode(self, encoded):
            algorithm, salt, hash = encoded.split("$", 2)
            assert algorithm == self.algorithm
            return {
                "algorithm": algorithm,
                "hash": hash,
                "salt": salt,
            }

        def verify(self, password, encoded):
            decoded = self.decode(encoded)
            encoded_2 = self.encode(password, decoded["salt"])
            return constant_time_compare(encoded, encoded_2)

        def safe_summary(self, encoded):
            decoded = self.decode(encoded)
            return {
                _("algorithm"): decoded["algorithm"],
                _("salt"): mask_hash(decoded["salt"], show=2),
                _("hash"): mask_hash(decoded["hash"]),
            }

        def must_update(self, encoded):
            decoded = self.decode(encoded)
            return must_update_salt(decoded["salt"], self.salt_entropy)

        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):
            self._check_encode_args(password, salt)
            hash = md5((salt + password).encode()).hexdigest()
            return "%s$%s$%s" % (self.algorithm, salt, hash)

        def decode(self, encoded):
            algorithm, salt, hash = encoded.split("$", 2)
            assert algorithm == self.algorithm
            return {
                "algorithm": algorithm,
                "hash": hash,
                "salt": salt,
            }

        def verify(self, password, encoded):
            decoded = self.decode(encoded)
            encoded_2 = self.encode(password, decoded["salt"])
            return constant_time_compare(encoded, encoded_2)

        def safe_summary(self, encoded):
            decoded = self.decode(encoded)
            return {
                _("algorithm"): decoded["algorithm"],
                _("salt"): mask_hash(decoded["salt"], show=2),
                _("hash"): mask_hash(decoded["hash"]),
            }

        def must_update(self, encoded):
            decoded = self.decode(encoded)
            return must_update_salt(decoded["salt"], self.salt_entropy)

        def harden_runtime(self, password, encoded):
            pass

    # RemovedInDjango51Warning.
    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 __init__(self, *args, **kwargs):
            warnings.warn(
                "django.contrib.auth.hashers.UnsaltedSHA1PasswordHasher is deprecated.",
                RemovedInDjango51Warning,
                stacklevel=2,
            )
            super().__init__(*args, **kwargs)

        def salt(self):
            return ""

        def encode(self, password, salt):
            if salt != "":
                raise ValueError("salt must be empty.")
            hash = hashlib.sha1(password.encode()).hexdigest()
            return "sha1$$%s" % hash

        def decode(self, encoded):
            assert encoded.startswith("sha1$$")
            return {
                "algorithm": self.algorithm,
                "hash": encoded[6:],
                "salt": None,
            }

        def verify(self, password, encoded):
            encoded_2 = self.encode(password, "")
            return constant_time_compare(encoded, encoded_2)

        def safe_summary(self, encoded):
            decoded = self.decode(encoded)
            return {
                _("algorithm"): decoded["algorithm"],
                _("hash"): mask_hash(decoded["hash"]),
            }

        def harden_runtime(self, password, encoded):
            pass

    # RemovedInDjango51Warning.
    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 __init__(self, *args, **kwargs):
            warnings.warn(
                "django.contrib.auth.hashers.UnsaltedMD5PasswordHasher is deprecated.",
                RemovedInDjango51Warning,
                stacklevel=2,
            )
            super().__init__(*args, **kwargs)

        def salt(self):
            return ""

        def encode(self, password, salt):
            if salt != "":
                raise ValueError("salt must be empty.")
            return md5(password.encode()).hexdigest()

        def decode(self, encoded):
            return {
                "algorithm": self.algorithm,
                "hash": encoded,
                "salt": None,
            }

        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):
            decoded = self.decode(encoded)
            return {
                _("algorithm"): decoded["algorithm"],
                _("hash"): mask_hash(decoded["hash"], show=3),
            }

        def harden_runtime(self, password, encoded):
            pass

    # RemovedInDjango50Warning.
    class CryptPasswordHasher(BasePasswordHasher):
        """
        Password hashing using UNIX crypt (not recommended)

        The crypt module is not supported on all platforms.
        """

        algorithm = "crypt"
        library = "crypt"

        def __init__(self, *args, **kwargs):
            warnings.warn(
                "django.contrib.auth.hashers.CryptPasswordHasher is deprecated.",
                RemovedInDjango50Warning,
                stacklevel=2,
            )
            super().__init__(*args, **kwargs)

        def salt(self):
            return get_random_string(2)

        def encode(self, password, salt):
            crypt = self._load_library()
            if len(salt) != 2:
                raise ValueError("salt must be of length 2.")
            hash = crypt.crypt(password, salt)
            if hash is None:  # A platform like OpenBSD with a dummy crypt module.
                raise TypeError("hash must be provided.")
            # we don't need to store the salt, but Django used to do this
            return "%s$%s$%s" % (self.algorithm, "", hash)

        def decode(self, encoded):
            algorithm, salt, hash = encoded.split("$", 2)
            assert algorithm == self.algorithm
            return {
                "algorithm": algorithm,
                "hash": hash,
                "salt": salt,
            }

        def verify(self, password, encoded):
            crypt = self._load_library()
            decoded = self.decode(encoded)
            data = crypt.crypt(password, decoded["hash"])
            return constant_time_compare(decoded["hash"], data)

        def safe_summary(self, encoded):
            decoded = self.decode(encoded)
            return {
                _("algorithm"): decoded["algorithm"],
                _("salt"): decoded["salt"],
                _("hash"): mask_hash(decoded["hash"], show=3),
            }

        def harden_runtime(self, password, encoded):
            pass