forked from STI/Astroport.ONE
125 lines
3.6 KiB
Python
125 lines
3.6 KiB
Python
# 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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from __future__ import annotations
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import typing
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from cryptography import utils
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from cryptography.exceptions import AlreadyFinalized, InvalidKey
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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 n.to_bytes(length=4, byteorder="big")
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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: bytes | None,
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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(f"Cannot derive keys larger than {max_length} bits.")
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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: bytes | None,
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backend: typing.Any = None,
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):
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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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self._used = False
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def _hash(self) -> hashes.Hash:
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return hashes.Hash(self._algorithm)
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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: bytes | None,
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otherinfo: bytes | None,
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backend: typing.Any = None,
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):
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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(f"{algorithm.name} is unsupported for ConcatKDF")
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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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self._used = False
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def _hmac(self) -> hmac.HMAC:
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return hmac.HMAC(self._salt, self._algorithm)
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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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