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Diffstat (limited to '.venv/lib/python3.12/site-packages/cryptography/hazmat/primitives/ciphers/modes.py')
| -rw-r--r-- | .venv/lib/python3.12/site-packages/cryptography/hazmat/primitives/ciphers/modes.py | 268 |
1 files changed, 268 insertions, 0 deletions
diff --git a/.venv/lib/python3.12/site-packages/cryptography/hazmat/primitives/ciphers/modes.py b/.venv/lib/python3.12/site-packages/cryptography/hazmat/primitives/ciphers/modes.py new file mode 100644 index 00000000..1dd2cc1e --- /dev/null +++ b/.venv/lib/python3.12/site-packages/cryptography/hazmat/primitives/ciphers/modes.py @@ -0,0 +1,268 @@ +# 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 +from cryptography.exceptions import UnsupportedAlgorithm, _Reasons +from cryptography.hazmat.primitives._cipheralgorithm import ( + BlockCipherAlgorithm, + CipherAlgorithm, +) +from cryptography.hazmat.primitives.ciphers import algorithms + + +class Mode(metaclass=abc.ABCMeta): + @property + @abc.abstractmethod + def name(self) -> str: + """ + A string naming this mode (e.g. "ECB", "CBC"). + """ + + @abc.abstractmethod + def validate_for_algorithm(self, algorithm: CipherAlgorithm) -> None: + """ + Checks that all the necessary invariants of this (mode, algorithm) + combination are met. + """ + + +class ModeWithInitializationVector(Mode, metaclass=abc.ABCMeta): + @property + @abc.abstractmethod + def initialization_vector(self) -> bytes: + """ + The value of the initialization vector for this mode as bytes. + """ + + +class ModeWithTweak(Mode, metaclass=abc.ABCMeta): + @property + @abc.abstractmethod + def tweak(self) -> bytes: + """ + The value of the tweak for this mode as bytes. + """ + + +class ModeWithNonce(Mode, metaclass=abc.ABCMeta): + @property + @abc.abstractmethod + def nonce(self) -> bytes: + """ + The value of the nonce for this mode as bytes. + """ + + +class ModeWithAuthenticationTag(Mode, metaclass=abc.ABCMeta): + @property + @abc.abstractmethod + def tag(self) -> bytes | None: + """ + The value of the tag supplied to the constructor of this mode. + """ + + +def _check_aes_key_length(self: Mode, algorithm: CipherAlgorithm) -> None: + if algorithm.key_size > 256 and algorithm.name == "AES": + raise ValueError( + "Only 128, 192, and 256 bit keys are allowed for this AES mode" + ) + + +def _check_iv_length( + self: ModeWithInitializationVector, algorithm: BlockCipherAlgorithm +) -> None: + iv_len = len(self.initialization_vector) + if iv_len * 8 != algorithm.block_size: + raise ValueError(f"Invalid IV size ({iv_len}) for {self.name}.") + + +def _check_nonce_length( + nonce: bytes, name: str, algorithm: CipherAlgorithm +) -> None: + if not isinstance(algorithm, BlockCipherAlgorithm): + raise UnsupportedAlgorithm( + f"{name} requires a block cipher algorithm", + _Reasons.UNSUPPORTED_CIPHER, + ) + if len(nonce) * 8 != algorithm.block_size: + raise ValueError(f"Invalid nonce size ({len(nonce)}) for {name}.") + + +def _check_iv_and_key_length( + self: ModeWithInitializationVector, algorithm: CipherAlgorithm +) -> None: + if not isinstance(algorithm, BlockCipherAlgorithm): + raise UnsupportedAlgorithm( + f"{self} requires a block cipher algorithm", + _Reasons.UNSUPPORTED_CIPHER, + ) + _check_aes_key_length(self, algorithm) + _check_iv_length(self, algorithm) + + +class CBC(ModeWithInitializationVector): + name = "CBC" + + def __init__(self, initialization_vector: bytes): + utils._check_byteslike("initialization_vector", initialization_vector) + self._initialization_vector = initialization_vector + + @property + def initialization_vector(self) -> bytes: + return self._initialization_vector + + validate_for_algorithm = _check_iv_and_key_length + + +class XTS(ModeWithTweak): + name = "XTS" + + def __init__(self, tweak: bytes): + utils._check_byteslike("tweak", tweak) + + if len(tweak) != 16: + raise ValueError("tweak must be 128-bits (16 bytes)") + + self._tweak = tweak + + @property + def tweak(self) -> bytes: + return self._tweak + + def validate_for_algorithm(self, algorithm: CipherAlgorithm) -> None: + if isinstance(algorithm, (algorithms.AES128, algorithms.AES256)): + raise TypeError( + "The AES128 and AES256 classes do not support XTS, please use " + "the standard AES class instead." + ) + + if algorithm.key_size not in (256, 512): + raise ValueError( + "The XTS specification requires a 256-bit key for AES-128-XTS" + " and 512-bit key for AES-256-XTS" + ) + + +class ECB(Mode): + name = "ECB" + + validate_for_algorithm = _check_aes_key_length + + +class OFB(ModeWithInitializationVector): + name = "OFB" + + def __init__(self, initialization_vector: bytes): + utils._check_byteslike("initialization_vector", initialization_vector) + self._initialization_vector = initialization_vector + + @property + def initialization_vector(self) -> bytes: + return self._initialization_vector + + validate_for_algorithm = _check_iv_and_key_length + + +class CFB(ModeWithInitializationVector): + name = "CFB" + + def __init__(self, initialization_vector: bytes): + utils._check_byteslike("initialization_vector", initialization_vector) + self._initialization_vector = initialization_vector + + @property + def initialization_vector(self) -> bytes: + return self._initialization_vector + + validate_for_algorithm = _check_iv_and_key_length + + +class CFB8(ModeWithInitializationVector): + name = "CFB8" + + def __init__(self, initialization_vector: bytes): + utils._check_byteslike("initialization_vector", initialization_vector) + self._initialization_vector = initialization_vector + + @property + def initialization_vector(self) -> bytes: + return self._initialization_vector + + validate_for_algorithm = _check_iv_and_key_length + + +class CTR(ModeWithNonce): + name = "CTR" + + def __init__(self, nonce: bytes): + utils._check_byteslike("nonce", nonce) + self._nonce = nonce + + @property + def nonce(self) -> bytes: + return self._nonce + + def validate_for_algorithm(self, algorithm: CipherAlgorithm) -> None: + _check_aes_key_length(self, algorithm) + _check_nonce_length(self.nonce, self.name, algorithm) + + +class GCM(ModeWithInitializationVector, ModeWithAuthenticationTag): + name = "GCM" + _MAX_ENCRYPTED_BYTES = (2**39 - 256) // 8 + _MAX_AAD_BYTES = (2**64) // 8 + + def __init__( + self, + initialization_vector: bytes, + tag: bytes | None = None, + min_tag_length: int = 16, + ): + # OpenSSL 3.0.0 constrains GCM IVs to [64, 1024] bits inclusive + # This is a sane limit anyway so we'll enforce it here. + utils._check_byteslike("initialization_vector", initialization_vector) + if len(initialization_vector) < 8 or len(initialization_vector) > 128: + raise ValueError( + "initialization_vector must be between 8 and 128 bytes (64 " + "and 1024 bits)." + ) + self._initialization_vector = initialization_vector + if tag is not None: + utils._check_bytes("tag", tag) + if min_tag_length < 4: + raise ValueError("min_tag_length must be >= 4") + if len(tag) < min_tag_length: + raise ValueError( + f"Authentication tag must be {min_tag_length} bytes or " + "longer." + ) + self._tag = tag + self._min_tag_length = min_tag_length + + @property + def tag(self) -> bytes | None: + return self._tag + + @property + def initialization_vector(self) -> bytes: + return self._initialization_vector + + def validate_for_algorithm(self, algorithm: CipherAlgorithm) -> None: + _check_aes_key_length(self, algorithm) + if not isinstance(algorithm, BlockCipherAlgorithm): + raise UnsupportedAlgorithm( + "GCM requires a block cipher algorithm", + _Reasons.UNSUPPORTED_CIPHER, + ) + block_size_bytes = algorithm.block_size // 8 + if self._tag is not None and len(self._tag) > block_size_bytes: + raise ValueError( + f"Authentication tag cannot be more than {block_size_bytes} " + "bytes." + ) |