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# This file is dual licensed under the terms of the Apache License, Version
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# 2.0, and the BSD License. See the LICENSE file in the root of this repository
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# for complete details.
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import abc
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class KeyDerivationFunction(metaclass=abc.ABCMeta):
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@abc.abstractmethod
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def derive(self, key_material: bytes) -> bytes:
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"""
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Deterministically generates and returns a new key based on the existing
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key material.
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"""
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@abc.abstractmethod
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def verify(self, key_material: bytes, expected_key: bytes) -> None:
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"""
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Checks whether the key generated by the key material matches the
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expected derived key. Raises an exception if they do not match.
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"""
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@@ -0,0 +1,155 @@
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# This file is dual licensed under the terms of the Apache License, Version
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# 2.0, and the BSD License. See the LICENSE file in the root of this repository
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# for complete details.
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import struct
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import typing
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from cryptography import utils
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from cryptography.exceptions import (
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AlreadyFinalized,
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InvalidKey,
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UnsupportedAlgorithm,
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_Reasons,
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)
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from cryptography.hazmat.backends import _get_backend
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from cryptography.hazmat.backends.interfaces import (
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Backend,
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HMACBackend,
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HashBackend,
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)
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from cryptography.hazmat.primitives import constant_time, hashes, hmac
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from cryptography.hazmat.primitives.kdf import KeyDerivationFunction
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def _int_to_u32be(n: int) -> bytes:
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return struct.pack(">I", n)
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def _common_args_checks(
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algorithm: hashes.HashAlgorithm,
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length: int,
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otherinfo: typing.Optional[bytes],
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) -> None:
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max_length = algorithm.digest_size * (2 ** 32 - 1)
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if length > max_length:
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raise ValueError(
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"Cannot derive keys larger than {} bits.".format(max_length)
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)
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if otherinfo is not None:
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utils._check_bytes("otherinfo", otherinfo)
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def _concatkdf_derive(
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key_material: bytes,
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length: int,
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auxfn: typing.Callable[[], hashes.HashContext],
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otherinfo: bytes,
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) -> bytes:
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utils._check_byteslike("key_material", key_material)
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output = [b""]
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outlen = 0
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counter = 1
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while length > outlen:
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h = auxfn()
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h.update(_int_to_u32be(counter))
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h.update(key_material)
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h.update(otherinfo)
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output.append(h.finalize())
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outlen += len(output[-1])
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counter += 1
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return b"".join(output)[:length]
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class ConcatKDFHash(KeyDerivationFunction):
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def __init__(
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self,
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algorithm: hashes.HashAlgorithm,
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length: int,
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otherinfo: typing.Optional[bytes],
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backend: typing.Optional[Backend] = None,
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):
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backend = _get_backend(backend)
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_common_args_checks(algorithm, length, otherinfo)
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self._algorithm = algorithm
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self._length = length
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self._otherinfo: bytes = otherinfo if otherinfo is not None else b""
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if not isinstance(backend, HashBackend):
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raise UnsupportedAlgorithm(
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"Backend object does not implement HashBackend.",
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_Reasons.BACKEND_MISSING_INTERFACE,
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)
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self._backend = backend
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self._used = False
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def _hash(self) -> hashes.Hash:
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return hashes.Hash(self._algorithm, self._backend)
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def derive(self, key_material: bytes) -> bytes:
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if self._used:
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raise AlreadyFinalized
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self._used = True
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return _concatkdf_derive(
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key_material, self._length, self._hash, self._otherinfo
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)
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def verify(self, key_material: bytes, expected_key: bytes) -> None:
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if not constant_time.bytes_eq(self.derive(key_material), expected_key):
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raise InvalidKey
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class ConcatKDFHMAC(KeyDerivationFunction):
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def __init__(
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self,
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algorithm: hashes.HashAlgorithm,
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length: int,
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salt: typing.Optional[bytes],
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otherinfo: typing.Optional[bytes],
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backend: typing.Optional[Backend] = None,
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):
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backend = _get_backend(backend)
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_common_args_checks(algorithm, length, otherinfo)
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self._algorithm = algorithm
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self._length = length
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self._otherinfo: bytes = otherinfo if otherinfo is not None else b""
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if algorithm.block_size is None:
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raise TypeError(
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"{} is unsupported for ConcatKDF".format(algorithm.name)
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)
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if salt is None:
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salt = b"\x00" * algorithm.block_size
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else:
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utils._check_bytes("salt", salt)
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self._salt = salt
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if not isinstance(backend, HMACBackend):
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raise UnsupportedAlgorithm(
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"Backend object does not implement HMACBackend.",
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_Reasons.BACKEND_MISSING_INTERFACE,
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)
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self._backend = backend
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self._used = False
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def _hmac(self) -> hmac.HMAC:
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return hmac.HMAC(self._salt, self._algorithm, self._backend)
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def derive(self, key_material: bytes) -> bytes:
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if self._used:
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raise AlreadyFinalized
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self._used = True
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return _concatkdf_derive(
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key_material, self._length, self._hmac, self._otherinfo
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)
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def verify(self, key_material: bytes, expected_key: bytes) -> None:
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if not constant_time.bytes_eq(self.derive(key_material), expected_key):
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raise InvalidKey
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@@ -0,0 +1,125 @@
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# This file is dual licensed under the terms of the Apache License, Version
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# 2.0, and the BSD License. See the LICENSE file in the root of this repository
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# for complete details.
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import typing
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from cryptography import utils
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from cryptography.exceptions import (
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AlreadyFinalized,
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InvalidKey,
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UnsupportedAlgorithm,
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_Reasons,
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)
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from cryptography.hazmat.backends import _get_backend
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from cryptography.hazmat.backends.interfaces import Backend, HMACBackend
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from cryptography.hazmat.primitives import constant_time, hashes, hmac
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from cryptography.hazmat.primitives.kdf import KeyDerivationFunction
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class HKDF(KeyDerivationFunction):
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def __init__(
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self,
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algorithm: hashes.HashAlgorithm,
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length: int,
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salt: typing.Optional[bytes],
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info: typing.Optional[bytes],
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backend: typing.Optional[Backend] = None,
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):
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backend = _get_backend(backend)
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if not isinstance(backend, HMACBackend):
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raise UnsupportedAlgorithm(
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"Backend object does not implement HMACBackend.",
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_Reasons.BACKEND_MISSING_INTERFACE,
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)
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self._algorithm = algorithm
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if salt is None:
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salt = b"\x00" * self._algorithm.digest_size
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else:
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utils._check_bytes("salt", salt)
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self._salt = salt
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self._backend = backend
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self._hkdf_expand = HKDFExpand(self._algorithm, length, info, backend)
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def _extract(self, key_material: bytes) -> bytes:
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h = hmac.HMAC(self._salt, self._algorithm, backend=self._backend)
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h.update(key_material)
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return h.finalize()
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def derive(self, key_material: bytes) -> bytes:
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utils._check_byteslike("key_material", key_material)
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return self._hkdf_expand.derive(self._extract(key_material))
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def verify(self, key_material: bytes, expected_key: bytes) -> None:
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if not constant_time.bytes_eq(self.derive(key_material), expected_key):
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raise InvalidKey
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class HKDFExpand(KeyDerivationFunction):
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def __init__(
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self,
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algorithm: hashes.HashAlgorithm,
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length: int,
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info: typing.Optional[bytes],
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backend: typing.Optional[Backend] = None,
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):
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backend = _get_backend(backend)
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if not isinstance(backend, HMACBackend):
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raise UnsupportedAlgorithm(
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"Backend object does not implement HMACBackend.",
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_Reasons.BACKEND_MISSING_INTERFACE,
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)
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self._algorithm = algorithm
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self._backend = backend
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max_length = 255 * algorithm.digest_size
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if length > max_length:
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raise ValueError(
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"Cannot derive keys larger than {} octets.".format(max_length)
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)
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self._length = length
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if info is None:
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info = b""
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else:
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utils._check_bytes("info", info)
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self._info = info
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self._used = False
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def _expand(self, key_material: bytes) -> bytes:
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output = [b""]
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counter = 1
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while self._algorithm.digest_size * (len(output) - 1) < self._length:
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h = hmac.HMAC(key_material, self._algorithm, backend=self._backend)
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h.update(output[-1])
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h.update(self._info)
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h.update(bytes([counter]))
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output.append(h.finalize())
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counter += 1
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return b"".join(output)[: self._length]
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def derive(self, key_material: bytes) -> bytes:
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utils._check_byteslike("key_material", key_material)
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if self._used:
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raise AlreadyFinalized
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self._used = True
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return self._expand(key_material)
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def verify(self, key_material: bytes, expected_key: bytes) -> None:
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if not constant_time.bytes_eq(self.derive(key_material), expected_key):
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raise InvalidKey
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@@ -0,0 +1,272 @@
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# This file is dual licensed under the terms of the Apache License, Version
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# 2.0, and the BSD License. See the LICENSE file in the root of this repository
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# for complete details.
|
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import typing
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from cryptography import utils
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from cryptography.exceptions import (
|
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AlreadyFinalized,
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InvalidKey,
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UnsupportedAlgorithm,
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_Reasons,
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)
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from cryptography.hazmat.backends import _get_backend
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from cryptography.hazmat.backends.interfaces import (
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Backend,
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CMACBackend,
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HMACBackend,
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)
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from cryptography.hazmat.primitives import (
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ciphers,
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cmac,
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constant_time,
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hashes,
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hmac,
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)
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from cryptography.hazmat.primitives.kdf import KeyDerivationFunction
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class Mode(utils.Enum):
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CounterMode = "ctr"
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class CounterLocation(utils.Enum):
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BeforeFixed = "before_fixed"
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AfterFixed = "after_fixed"
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class _KBKDFDeriver:
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def __init__(
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self,
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prf: typing.Callable,
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mode: Mode,
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length: int,
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rlen: int,
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llen: typing.Optional[int],
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location: CounterLocation,
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label: typing.Optional[bytes],
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context: typing.Optional[bytes],
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fixed: typing.Optional[bytes],
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):
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assert callable(prf)
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if not isinstance(mode, Mode):
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raise TypeError("mode must be of type Mode")
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if not isinstance(location, CounterLocation):
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raise TypeError("location must be of type CounterLocation")
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if (label or context) and fixed:
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raise ValueError(
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"When supplying fixed data, " "label and context are ignored."
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)
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if rlen is None or not self._valid_byte_length(rlen):
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raise ValueError("rlen must be between 1 and 4")
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if llen is None and fixed is None:
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raise ValueError("Please specify an llen")
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if llen is not None and not isinstance(llen, int):
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raise TypeError("llen must be an integer")
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if label is None:
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label = b""
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if context is None:
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context = b""
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utils._check_bytes("label", label)
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utils._check_bytes("context", context)
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self._prf = prf
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self._mode = mode
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self._length = length
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self._rlen = rlen
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self._llen = llen
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self._location = location
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self._label = label
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self._context = context
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self._used = False
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self._fixed_data = fixed
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@staticmethod
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def _valid_byte_length(value: int) -> bool:
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if not isinstance(value, int):
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raise TypeError("value must be of type int")
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value_bin = utils.int_to_bytes(1, value)
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if not 1 <= len(value_bin) <= 4:
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return False
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return True
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def derive(self, key_material: bytes, prf_output_size: int) -> bytes:
|
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if self._used:
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raise AlreadyFinalized
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|
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utils._check_byteslike("key_material", key_material)
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self._used = True
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# inverse floor division (equivalent to ceiling)
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rounds = -(-self._length // prf_output_size)
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output = [b""]
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# For counter mode, the number of iterations shall not be
|
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# larger than 2^r-1, where r <= 32 is the binary length of the counter
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# This ensures that the counter values used as an input to the
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# PRF will not repeat during a particular call to the KDF function.
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r_bin = utils.int_to_bytes(1, self._rlen)
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if rounds > pow(2, len(r_bin) * 8) - 1:
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raise ValueError("There are too many iterations.")
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|
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for i in range(1, rounds + 1):
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h = self._prf(key_material)
|
||||
|
||||
counter = utils.int_to_bytes(i, self._rlen)
|
||||
if self._location == CounterLocation.BeforeFixed:
|
||||
h.update(counter)
|
||||
|
||||
h.update(self._generate_fixed_input())
|
||||
|
||||
if self._location == CounterLocation.AfterFixed:
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h.update(counter)
|
||||
|
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output.append(h.finalize())
|
||||
|
||||
return b"".join(output)[: self._length]
|
||||
|
||||
def _generate_fixed_input(self) -> bytes:
|
||||
if self._fixed_data and isinstance(self._fixed_data, bytes):
|
||||
return self._fixed_data
|
||||
|
||||
l_val = utils.int_to_bytes(self._length * 8, self._llen)
|
||||
|
||||
return b"".join([self._label, b"\x00", self._context, l_val])
|
||||
|
||||
|
||||
class KBKDFHMAC(KeyDerivationFunction):
|
||||
def __init__(
|
||||
self,
|
||||
algorithm: hashes.HashAlgorithm,
|
||||
mode: Mode,
|
||||
length: int,
|
||||
rlen: int,
|
||||
llen: typing.Optional[int],
|
||||
location: CounterLocation,
|
||||
label: typing.Optional[bytes],
|
||||
context: typing.Optional[bytes],
|
||||
fixed: typing.Optional[bytes],
|
||||
backend: typing.Optional[Backend] = None,
|
||||
):
|
||||
backend = _get_backend(backend)
|
||||
if not isinstance(backend, HMACBackend):
|
||||
raise UnsupportedAlgorithm(
|
||||
"Backend object does not implement HMACBackend.",
|
||||
_Reasons.BACKEND_MISSING_INTERFACE,
|
||||
)
|
||||
|
||||
if not isinstance(algorithm, hashes.HashAlgorithm):
|
||||
raise UnsupportedAlgorithm(
|
||||
"Algorithm supplied is not a supported hash algorithm.",
|
||||
_Reasons.UNSUPPORTED_HASH,
|
||||
)
|
||||
|
||||
if not backend.hmac_supported(algorithm):
|
||||
raise UnsupportedAlgorithm(
|
||||
"Algorithm supplied is not a supported hmac algorithm.",
|
||||
_Reasons.UNSUPPORTED_HASH,
|
||||
)
|
||||
|
||||
self._algorithm = algorithm
|
||||
self._backend = backend
|
||||
|
||||
self._deriver = _KBKDFDeriver(
|
||||
self._prf,
|
||||
mode,
|
||||
length,
|
||||
rlen,
|
||||
llen,
|
||||
location,
|
||||
label,
|
||||
context,
|
||||
fixed,
|
||||
)
|
||||
|
||||
def _prf(self, key_material: bytes):
|
||||
return hmac.HMAC(key_material, self._algorithm, backend=self._backend)
|
||||
|
||||
def derive(self, key_material) -> bytes:
|
||||
return self._deriver.derive(key_material, self._algorithm.digest_size)
|
||||
|
||||
def verify(self, key_material: bytes, expected_key: bytes) -> None:
|
||||
if not constant_time.bytes_eq(self.derive(key_material), expected_key):
|
||||
raise InvalidKey
|
||||
|
||||
|
||||
class KBKDFCMAC(KeyDerivationFunction):
|
||||
def __init__(
|
||||
self,
|
||||
algorithm,
|
||||
mode: Mode,
|
||||
length: int,
|
||||
rlen: int,
|
||||
llen: typing.Optional[int],
|
||||
location: CounterLocation,
|
||||
label: typing.Optional[bytes],
|
||||
context: typing.Optional[bytes],
|
||||
fixed: typing.Optional[bytes],
|
||||
backend: typing.Optional[Backend] = None,
|
||||
):
|
||||
backend = _get_backend(backend)
|
||||
if not isinstance(backend, CMACBackend):
|
||||
raise UnsupportedAlgorithm(
|
||||
"Backend object does not implement CMACBackend.",
|
||||
_Reasons.BACKEND_MISSING_INTERFACE,
|
||||
)
|
||||
|
||||
if not issubclass(
|
||||
algorithm, ciphers.BlockCipherAlgorithm
|
||||
) or not issubclass(algorithm, ciphers.CipherAlgorithm):
|
||||
raise UnsupportedAlgorithm(
|
||||
"Algorithm supplied is not a supported cipher algorithm.",
|
||||
_Reasons.UNSUPPORTED_CIPHER,
|
||||
)
|
||||
|
||||
self._algorithm = algorithm
|
||||
self._backend = backend
|
||||
self._cipher: typing.Optional[ciphers.BlockCipherAlgorithm] = None
|
||||
|
||||
self._deriver = _KBKDFDeriver(
|
||||
self._prf,
|
||||
mode,
|
||||
length,
|
||||
rlen,
|
||||
llen,
|
||||
location,
|
||||
label,
|
||||
context,
|
||||
fixed,
|
||||
)
|
||||
|
||||
def _prf(self, _: bytes):
|
||||
assert self._cipher is not None
|
||||
|
||||
return cmac.CMAC(self._cipher, backend=self._backend)
|
||||
|
||||
def derive(self, key_material: bytes) -> bytes:
|
||||
self._cipher = self._algorithm(key_material)
|
||||
|
||||
assert self._cipher is not None
|
||||
|
||||
if not self._backend.cmac_algorithm_supported(self._cipher):
|
||||
raise UnsupportedAlgorithm(
|
||||
"Algorithm supplied is not a supported cipher algorithm.",
|
||||
_Reasons.UNSUPPORTED_CIPHER,
|
||||
)
|
||||
|
||||
return self._deriver.derive(key_material, self._cipher.block_size // 8)
|
||||
|
||||
def verify(self, key_material: bytes, expected_key: bytes) -> None:
|
||||
if not constant_time.bytes_eq(self.derive(key_material), expected_key):
|
||||
raise InvalidKey
|
||||
@@ -0,0 +1,69 @@
|
||||
# This file is dual licensed under the terms of the Apache License, Version
|
||||
# 2.0, and the BSD License. See the LICENSE file in the root of this repository
|
||||
# for complete details.
|
||||
|
||||
|
||||
import typing
|
||||
|
||||
from cryptography import utils
|
||||
from cryptography.exceptions import (
|
||||
AlreadyFinalized,
|
||||
InvalidKey,
|
||||
UnsupportedAlgorithm,
|
||||
_Reasons,
|
||||
)
|
||||
from cryptography.hazmat.backends import _get_backend
|
||||
from cryptography.hazmat.backends.interfaces import Backend, PBKDF2HMACBackend
|
||||
from cryptography.hazmat.primitives import constant_time, hashes
|
||||
from cryptography.hazmat.primitives.kdf import KeyDerivationFunction
|
||||
|
||||
|
||||
class PBKDF2HMAC(KeyDerivationFunction):
|
||||
def __init__(
|
||||
self,
|
||||
algorithm: hashes.HashAlgorithm,
|
||||
length: int,
|
||||
salt: bytes,
|
||||
iterations: int,
|
||||
backend: typing.Optional[Backend] = None,
|
||||
):
|
||||
backend = _get_backend(backend)
|
||||
if not isinstance(backend, PBKDF2HMACBackend):
|
||||
raise UnsupportedAlgorithm(
|
||||
"Backend object does not implement PBKDF2HMACBackend.",
|
||||
_Reasons.BACKEND_MISSING_INTERFACE,
|
||||
)
|
||||
|
||||
if not backend.pbkdf2_hmac_supported(algorithm):
|
||||
raise UnsupportedAlgorithm(
|
||||
"{} is not supported for PBKDF2 by this backend.".format(
|
||||
algorithm.name
|
||||
),
|
||||
_Reasons.UNSUPPORTED_HASH,
|
||||
)
|
||||
self._used = False
|
||||
self._algorithm = algorithm
|
||||
self._length = length
|
||||
utils._check_bytes("salt", salt)
|
||||
self._salt = salt
|
||||
self._iterations = iterations
|
||||
self._backend = backend
|
||||
|
||||
def derive(self, key_material: bytes) -> bytes:
|
||||
if self._used:
|
||||
raise AlreadyFinalized("PBKDF2 instances can only be used once.")
|
||||
self._used = True
|
||||
|
||||
utils._check_byteslike("key_material", key_material)
|
||||
return self._backend.derive_pbkdf2_hmac(
|
||||
self._algorithm,
|
||||
self._length,
|
||||
self._salt,
|
||||
self._iterations,
|
||||
key_material,
|
||||
)
|
||||
|
||||
def verify(self, key_material: bytes, expected_key: bytes) -> None:
|
||||
derived_key = self.derive(key_material)
|
||||
if not constant_time.bytes_eq(derived_key, expected_key):
|
||||
raise InvalidKey("Keys do not match.")
|
||||
@@ -0,0 +1,75 @@
|
||||
# This file is dual licensed under the terms of the Apache License, Version
|
||||
# 2.0, and the BSD License. See the LICENSE file in the root of this repository
|
||||
# for complete details.
|
||||
|
||||
|
||||
import sys
|
||||
import typing
|
||||
|
||||
from cryptography import utils
|
||||
from cryptography.exceptions import (
|
||||
AlreadyFinalized,
|
||||
InvalidKey,
|
||||
UnsupportedAlgorithm,
|
||||
_Reasons,
|
||||
)
|
||||
from cryptography.hazmat.backends import _get_backend
|
||||
from cryptography.hazmat.backends.interfaces import Backend, ScryptBackend
|
||||
from cryptography.hazmat.primitives import constant_time
|
||||
from cryptography.hazmat.primitives.kdf import KeyDerivationFunction
|
||||
|
||||
|
||||
# This is used by the scrypt tests to skip tests that require more memory
|
||||
# than the MEM_LIMIT
|
||||
_MEM_LIMIT = sys.maxsize // 2
|
||||
|
||||
|
||||
class Scrypt(KeyDerivationFunction):
|
||||
def __init__(
|
||||
self,
|
||||
salt: bytes,
|
||||
length: int,
|
||||
n: int,
|
||||
r: int,
|
||||
p: int,
|
||||
backend: typing.Optional[Backend] = None,
|
||||
):
|
||||
backend = _get_backend(backend)
|
||||
if not isinstance(backend, ScryptBackend):
|
||||
raise UnsupportedAlgorithm(
|
||||
"Backend object does not implement ScryptBackend.",
|
||||
_Reasons.BACKEND_MISSING_INTERFACE,
|
||||
)
|
||||
|
||||
self._length = length
|
||||
utils._check_bytes("salt", salt)
|
||||
if n < 2 or (n & (n - 1)) != 0:
|
||||
raise ValueError("n must be greater than 1 and be a power of 2.")
|
||||
|
||||
if r < 1:
|
||||
raise ValueError("r must be greater than or equal to 1.")
|
||||
|
||||
if p < 1:
|
||||
raise ValueError("p must be greater than or equal to 1.")
|
||||
|
||||
self._used = False
|
||||
self._salt = salt
|
||||
self._n = n
|
||||
self._r = r
|
||||
self._p = p
|
||||
self._backend = backend
|
||||
|
||||
def derive(self, key_material: bytes) -> bytes:
|
||||
if self._used:
|
||||
raise AlreadyFinalized("Scrypt instances can only be used once.")
|
||||
self._used = True
|
||||
|
||||
utils._check_byteslike("key_material", key_material)
|
||||
return self._backend.derive_scrypt(
|
||||
key_material, self._salt, self._length, self._n, self._r, self._p
|
||||
)
|
||||
|
||||
def verify(self, key_material: bytes, expected_key: bytes) -> None:
|
||||
derived_key = self.derive(key_material)
|
||||
if not constant_time.bytes_eq(derived_key, expected_key):
|
||||
raise InvalidKey("Keys do not match.")
|
||||
@@ -0,0 +1,79 @@
|
||||
# This file is dual licensed under the terms of the Apache License, Version
|
||||
# 2.0, and the BSD License. See the LICENSE file in the root of this repository
|
||||
# for complete details.
|
||||
|
||||
|
||||
import struct
|
||||
import typing
|
||||
|
||||
from cryptography import utils
|
||||
from cryptography.exceptions import (
|
||||
AlreadyFinalized,
|
||||
InvalidKey,
|
||||
UnsupportedAlgorithm,
|
||||
_Reasons,
|
||||
)
|
||||
from cryptography.hazmat.backends import _get_backend
|
||||
from cryptography.hazmat.backends.interfaces import Backend, HashBackend
|
||||
from cryptography.hazmat.primitives import constant_time, hashes
|
||||
from cryptography.hazmat.primitives.kdf import KeyDerivationFunction
|
||||
|
||||
|
||||
def _int_to_u32be(n):
|
||||
return struct.pack(">I", n)
|
||||
|
||||
|
||||
class X963KDF(KeyDerivationFunction):
|
||||
def __init__(
|
||||
self,
|
||||
algorithm: hashes.HashAlgorithm,
|
||||
length: int,
|
||||
sharedinfo: typing.Optional[bytes],
|
||||
backend: typing.Optional[Backend] = None,
|
||||
):
|
||||
backend = _get_backend(backend)
|
||||
|
||||
max_len = algorithm.digest_size * (2 ** 32 - 1)
|
||||
if length > max_len:
|
||||
raise ValueError(
|
||||
"Cannot derive keys larger than {} bits.".format(max_len)
|
||||
)
|
||||
if sharedinfo is not None:
|
||||
utils._check_bytes("sharedinfo", sharedinfo)
|
||||
|
||||
self._algorithm = algorithm
|
||||
self._length = length
|
||||
self._sharedinfo = sharedinfo
|
||||
|
||||
if not isinstance(backend, HashBackend):
|
||||
raise UnsupportedAlgorithm(
|
||||
"Backend object does not implement HashBackend.",
|
||||
_Reasons.BACKEND_MISSING_INTERFACE,
|
||||
)
|
||||
self._backend = backend
|
||||
self._used = False
|
||||
|
||||
def derive(self, key_material: bytes) -> bytes:
|
||||
if self._used:
|
||||
raise AlreadyFinalized
|
||||
self._used = True
|
||||
utils._check_byteslike("key_material", key_material)
|
||||
output = [b""]
|
||||
outlen = 0
|
||||
counter = 1
|
||||
|
||||
while self._length > outlen:
|
||||
h = hashes.Hash(self._algorithm, self._backend)
|
||||
h.update(key_material)
|
||||
h.update(_int_to_u32be(counter))
|
||||
if self._sharedinfo is not None:
|
||||
h.update(self._sharedinfo)
|
||||
output.append(h.finalize())
|
||||
outlen += len(output[-1])
|
||||
counter += 1
|
||||
|
||||
return b"".join(output)[: self._length]
|
||||
|
||||
def verify(self, key_material: bytes, expected_key: bytes) -> None:
|
||||
if not constant_time.bytes_eq(self.derive(key_material), expected_key):
|
||||
raise InvalidKey
|
||||
Reference in new issue
Block a user