source/cryptography/hazmat/primitives/_cipheralgorithm.py

# 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.

from __future__ import annotations

import abc

from cryptography import utils

# This exists to break an import cycle. It is normally accessible from the
# ciphers module.


class CipherAlgorithm(metaclass=abc.ABCMeta):
    @property
    @abc.abstractmethod
    def name(self) -> str:
        """
        A string naming this mode (e.g. "AES", "Camellia").
        """

    @property
    @abc.abstractmethod
    def key_sizes(self) -> frozenset[int]:
        """
        Valid key sizes for this algorithm in bits
        """

    @property
    @abc.abstractmethod
    def key_size(self) -> int:
        """
        The size of the key being used as an integer in bits (e.g. 128, 256).
        """


class BlockCipherAlgorithm(CipherAlgorithm):
    key: utils.Buffer

    @property
    @abc.abstractmethod
    def block_size(self) -> int:
        """
        The size of a block as an integer in bits (e.g. 64, 128).
        """


def _verify_key_size(
    algorithm: CipherAlgorithm, key: utils.Buffer
) -> utils.Buffer:
    # Verify that the key is instance of bytes
    utils._check_byteslike("key", key)

    # Verify that the key size matches the expected key size
    if len(key) * 8 not in algorithm.key_sizes:
        raise ValueError(
            f"Invalid key size ({len(key) * 8}) for {algorithm.name}."
        )
    return key