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# 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
import typing
from cryptography.hazmat.bindings._rust import openssl as rust_openssl
from cryptography.hazmat.primitives._cipheralgorithm import CipherAlgorithm
from cryptography.hazmat.primitives.ciphers import modes
class CipherContext(metaclass=abc.ABCMeta):
@abc.abstractmethod
def update(self, data: bytes) -> bytes:
"""
Processes the provided bytes through the cipher and returns the results
as bytes.
"""
@abc.abstractmethod
def update_into(self, data: bytes, buf: bytes) -> int:
"""
Processes the provided bytes and writes the resulting data into the
provided buffer. Returns the number of bytes written.
"""
@abc.abstractmethod
def finalize(self) -> bytes:
"""
Returns the results of processing the final block as bytes.
"""
@abc.abstractmethod
def reset_nonce(self, nonce: bytes) -> None:
"""
Resets the nonce for the cipher context to the provided value.
Raises an exception if it does not support reset or if the
provided nonce does not have a valid length.
"""
class AEADCipherContext(CipherContext, metaclass=abc.ABCMeta):
@abc.abstractmethod
def authenticate_additional_data(self, data: bytes) -> None:
"""
Authenticates the provided bytes.
"""
class AEADDecryptionContext(AEADCipherContext, metaclass=abc.ABCMeta):
@abc.abstractmethod
def finalize_with_tag(self, tag: bytes) -> bytes:
"""
Returns the results of processing the final block as bytes and allows
delayed passing of the authentication tag.
"""
class AEADEncryptionContext(AEADCipherContext, metaclass=abc.ABCMeta):
@property
@abc.abstractmethod
def tag(self) -> bytes:
"""
Returns tag bytes. This is only available after encryption is
finalized.
"""
Mode = typing.TypeVar(
"Mode", bound=typing.Optional[modes.Mode], covariant=True
)
class Cipher(typing.Generic[Mode]):
def __init__(
self,
algorithm: CipherAlgorithm,
mode: Mode,
backend: typing.Any = None,
) -> None:
if not isinstance(algorithm, CipherAlgorithm):
raise TypeError("Expected interface of CipherAlgorithm.")
if mode is not None:
# mypy needs this assert to narrow the type from our generic
# type. Maybe it won't some time in the future.
assert isinstance(mode, modes.Mode)
mode.validate_for_algorithm(algorithm)
self.algorithm = algorithm
self.mode = mode
@typing.overload
def encryptor(
self: Cipher[modes.ModeWithAuthenticationTag],
) -> AEADEncryptionContext: ...
@typing.overload
def encryptor(
self: _CIPHER_TYPE,
) -> CipherContext: ...
def encryptor(self):
if isinstance(self.mode, modes.ModeWithAuthenticationTag):
if self.mode.tag is not None:
raise ValueError(
"Authentication tag must be None when encrypting."
)
return rust_openssl.ciphers.create_encryption_ctx(
self.algorithm, self.mode
)
@typing.overload
def decryptor(
self: Cipher[modes.ModeWithAuthenticationTag],
) -> AEADDecryptionContext: ...
@typing.overload
def decryptor(
self: _CIPHER_TYPE,
) -> CipherContext: ...
def decryptor(self):
return rust_openssl.ciphers.create_decryption_ctx(
self.algorithm, self.mode
)
_CIPHER_TYPE = Cipher[
typing.Union[
modes.ModeWithNonce,
modes.ModeWithTweak,
None,
modes.ECB,
modes.ModeWithInitializationVector,
]
]
CipherContext.register(rust_openssl.ciphers.CipherContext)
AEADEncryptionContext.register(rust_openssl.ciphers.AEADEncryptionContext)
AEADDecryptionContext.register(rust_openssl.ciphers.AEADDecryptionContext)