# SPDX-License-Identifier: MIT
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from __future__ import annotations
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import os
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from typing import ClassVar, Literal
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from ._utils import (
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Parameters,
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_check_types,
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extract_parameters,
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validate_params_for_platform,
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)
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from .exceptions import InvalidHashError
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from .low_level import Type, hash_secret, verify_secret
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from .profiles import get_default_parameters
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default_params = get_default_parameters()
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DEFAULT_RANDOM_SALT_LENGTH = default_params.salt_len
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DEFAULT_HASH_LENGTH = default_params.hash_len
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DEFAULT_TIME_COST = default_params.time_cost
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DEFAULT_MEMORY_COST = default_params.memory_cost
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DEFAULT_PARALLELISM = default_params.parallelism
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def _ensure_bytes(s: bytes | str, encoding: str) -> bytes:
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"""
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Ensure *s* is a bytes string. Encode using *encoding* if it isn't.
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"""
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if isinstance(s, bytes):
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return s
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return s.encode(encoding)
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class PasswordHasher:
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r"""
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High level class to hash passwords with sensible defaults.
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Uses Argon2\ **id** by default and uses a random salt_ for hashing. But it
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can verify any type of Argon2 as long as the hash is correctly encoded.
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The reason for this being a class is both for convenience to carry
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parameters and to verify the parameters only *once*. Any unnecessary
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slowdown when hashing is a tangible advantage for a brute-force attacker.
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Args:
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time_cost:
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Defines the amount of computation realized and therefore the
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execution time, given in number of iterations.
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memory_cost: Defines the memory usage, given in kibibytes_.
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parallelism:
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Defines the number of parallel threads (*changes* the resulting
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hash value).
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hash_len: Length of the hash in bytes.
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salt_len: Length of random salt to be generated for each password.
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encoding:
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The Argon2 C library expects bytes. So if :meth:`hash` or
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:meth:`verify` are passed a ``str``, it will be encoded using this
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encoding.
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type:
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Argon2 type to use. Only change for interoperability with legacy
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systems.
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.. versionadded:: 16.0.0
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.. versionchanged:: 18.2.0
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Switch from Argon2i to Argon2id based on the recommendation by the
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current RFC draft. See also :doc:`parameters`.
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.. versionchanged:: 18.2.0
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Changed default *memory_cost* to 100 MiB and default *parallelism* to 8.
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.. versionchanged:: 18.2.0 ``verify`` now will determine the type of hash.
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.. versionchanged:: 18.3.0 The Argon2 type is configurable now.
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.. versionadded:: 21.2.0 :meth:`from_parameters`
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.. versionchanged:: 21.2.0
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Changed defaults to :data:`argon2.profiles.RFC_9106_LOW_MEMORY`.
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.. _salt: https://en.wikipedia.org/wiki/Salt_(cryptography)
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.. _kibibytes: https://en.wikipedia.org/wiki/Binary_prefix#kibi
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"""
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__slots__ = ["_parameters", "encoding"]
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_parameters: Parameters
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encoding: str
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def __init__(
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self,
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time_cost: int = DEFAULT_TIME_COST,
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memory_cost: int = DEFAULT_MEMORY_COST,
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parallelism: int = DEFAULT_PARALLELISM,
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hash_len: int = DEFAULT_HASH_LENGTH,
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salt_len: int = DEFAULT_RANDOM_SALT_LENGTH,
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encoding: str = "utf-8",
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type: Type = Type.ID,
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):
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e = _check_types(
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time_cost=(time_cost, int),
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memory_cost=(memory_cost, int),
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parallelism=(parallelism, int),
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hash_len=(hash_len, int),
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salt_len=(salt_len, int),
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encoding=(encoding, str),
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type=(type, Type),
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)
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if e:
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raise TypeError(e)
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params = Parameters(
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type=type,
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version=19,
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salt_len=salt_len,
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hash_len=hash_len,
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time_cost=time_cost,
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memory_cost=memory_cost,
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parallelism=parallelism,
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)
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validate_params_for_platform(params)
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# Cache a Parameters object for check_needs_rehash.
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self._parameters = params
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self.encoding = encoding
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@classmethod
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def from_parameters(cls, params: Parameters) -> PasswordHasher:
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"""
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Construct a `PasswordHasher` from *params*.
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Returns:
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A `PasswordHasher` instance with the parameters from *params*.
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.. versionadded:: 21.2.0
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"""
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return cls(
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time_cost=params.time_cost,
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memory_cost=params.memory_cost,
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parallelism=params.parallelism,
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hash_len=params.hash_len,
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salt_len=params.salt_len,
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type=params.type,
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)
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@property
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def time_cost(self) -> int:
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return self._parameters.time_cost
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@property
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def memory_cost(self) -> int:
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return self._parameters.memory_cost
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@property
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def parallelism(self) -> int:
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return self._parameters.parallelism
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@property
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def hash_len(self) -> int:
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return self._parameters.hash_len
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@property
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def salt_len(self) -> int:
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return self._parameters.salt_len
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@property
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def type(self) -> Type:
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return self._parameters.type
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def hash(self, password: str | bytes, *, salt: bytes | None = None) -> str:
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"""
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Hash *password* and return an encoded hash.
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Args:
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password: Password to hash.
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salt:
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If None, a random salt is securely created.
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.. danger::
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You should **not** pass a salt unless you really know what
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you are doing.
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Raises:
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argon2.exceptions.HashingError: If hashing fails.
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Returns:
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Hashed *password*.
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.. versionadded:: 23.1.0 *salt* parameter
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"""
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return hash_secret(
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secret=_ensure_bytes(password, self.encoding),
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salt=salt or os.urandom(self.salt_len),
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time_cost=self.time_cost,
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memory_cost=self.memory_cost,
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parallelism=self.parallelism,
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hash_len=self.hash_len,
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type=self.type,
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).decode("ascii")
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_header_to_type: ClassVar[dict[bytes, Type]] = {
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b"$argon2i$": Type.I,
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b"$argon2d$": Type.D,
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b"$argon2id": Type.ID,
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}
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def verify(
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self, hash: str | bytes, password: str | bytes
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) -> Literal[True]:
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"""
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Verify that *password* matches *hash*.
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.. warning::
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It is assumed that the caller is in full control of the hash. No
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other parsing than the determination of the hash type is done by
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*argon2-cffi*.
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Args:
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hash: An encoded hash as returned from :meth:`PasswordHasher.hash`.
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password: The password to verify.
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Raises:
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argon2.exceptions.VerifyMismatchError:
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If verification fails because *hash* is not valid for
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*password*.
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argon2.exceptions.VerificationError:
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If verification fails for other reasons.
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argon2.exceptions.InvalidHashError:
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If *hash* is so clearly invalid, that it couldn't be passed to
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Argon2.
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Returns:
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``True`` on success, otherwise an exception is raised.
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.. versionchanged:: 16.1.0
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Raise :exc:`~argon2.exceptions.VerifyMismatchError` on mismatches
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instead of its more generic superclass.
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.. versionadded:: 18.2.0 Hash type agility.
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"""
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hash = _ensure_bytes(hash, "ascii")
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try:
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hash_type = self._header_to_type[hash[:9]]
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except LookupError:
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raise InvalidHashError from None
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return verify_secret(
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hash, _ensure_bytes(password, self.encoding), hash_type
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)
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def check_needs_rehash(self, hash: str | bytes) -> bool:
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"""
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Check whether *hash* was created using the instance's parameters.
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Whenever your Argon2 parameters -- or *argon2-cffi*'s defaults! --
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change, you should rehash your passwords at the next opportunity. The
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common approach is to do that whenever a user logs in, since that
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should be the only time when you have access to the cleartext
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password.
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Therefore it's best practice to check -- and if necessary rehash --
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passwords after each successful authentication.
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Args:
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hash: An encoded Argon2 password hash.
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Returns:
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Whether *hash* was created using the instance's parameters.
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.. versionadded:: 18.2.0
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.. versionchanged:: 24.1.0 Accepts bytes for *hash*.
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"""
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if isinstance(hash, bytes):
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hash = hash.decode("ascii")
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return self._parameters != extract_parameters(hash)
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