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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)