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dist/ba_data/python-site-packages/cryptography/hazmat/primitives/ciphers/base.py

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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.exceptions import (
+    AlreadyFinalized,
+    AlreadyUpdated,
+    NotYetFinalized,
+)
+from cryptography.hazmat.primitives._cipheralgorithm import CipherAlgorithm
+from cryptography.hazmat.primitives.ciphers import modes
+
+if typing.TYPE_CHECKING:
+    from cryptography.hazmat.backends.openssl.ciphers import (
+        _CipherContext as _BackendCipherContext,
+    )
+
+
+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.
+        """
+
+
+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."
+                )
+        from cryptography.hazmat.backends.openssl.backend import backend
+
+        ctx = backend.create_symmetric_encryption_ctx(
+            self.algorithm, self.mode
+        )
+        return self._wrap_ctx(ctx, encrypt=True)
+
+    @typing.overload
+    def decryptor(
+        self: Cipher[modes.ModeWithAuthenticationTag],
+    ) -> AEADDecryptionContext:
+        ...
+
+    @typing.overload
+    def decryptor(
+        self: _CIPHER_TYPE,
+    ) -> CipherContext:
+        ...
+
+    def decryptor(self):
+        from cryptography.hazmat.backends.openssl.backend import backend
+
+        ctx = backend.create_symmetric_decryption_ctx(
+            self.algorithm, self.mode
+        )
+        return self._wrap_ctx(ctx, encrypt=False)
+
+    def _wrap_ctx(
+        self, ctx: _BackendCipherContext, encrypt: bool
+    ) -> typing.Union[
+        AEADEncryptionContext, AEADDecryptionContext, CipherContext
+    ]:
+        if isinstance(self.mode, modes.ModeWithAuthenticationTag):
+            if encrypt:
+                return _AEADEncryptionContext(ctx)
+            else:
+                return _AEADDecryptionContext(ctx)
+        else:
+            return _CipherContext(ctx)
+
+
+_CIPHER_TYPE = Cipher[
+    typing.Union[
+        modes.ModeWithNonce,
+        modes.ModeWithTweak,
+        None,
+        modes.ECB,
+        modes.ModeWithInitializationVector,
+    ]
+]
+
+
+class _CipherContext(CipherContext):
+    _ctx: typing.Optional[_BackendCipherContext]
+
+    def __init__(self, ctx: _BackendCipherContext) -> None:
+        self._ctx = ctx
+
+    def update(self, data: bytes) -> bytes:
+        if self._ctx is None:
+            raise AlreadyFinalized("Context was already finalized.")
+        return self._ctx.update(data)
+
+    def update_into(self, data: bytes, buf: bytes) -> int:
+        if self._ctx is None:
+            raise AlreadyFinalized("Context was already finalized.")
+        return self._ctx.update_into(data, buf)
+
+    def finalize(self) -> bytes:
+        if self._ctx is None:
+            raise AlreadyFinalized("Context was already finalized.")
+        data = self._ctx.finalize()
+        self._ctx = None
+        return data
+
+
+class _AEADCipherContext(AEADCipherContext):
+    _ctx: typing.Optional[_BackendCipherContext]
+    _tag: typing.Optional[bytes]
+
+    def __init__(self, ctx: _BackendCipherContext) -> None:
+        self._ctx = ctx
+        self._bytes_processed = 0
+        self._aad_bytes_processed = 0
+        self._tag = None
+        self._updated = False
+
+    def _check_limit(self, data_size: int) -> None:
+        if self._ctx is None:
+            raise AlreadyFinalized("Context was already finalized.")
+        self._updated = True
+        self._bytes_processed += data_size
+        if self._bytes_processed > self._ctx._mode._MAX_ENCRYPTED_BYTES:
+            raise ValueError(
+                "{} has a maximum encrypted byte limit of {}".format(
+                    self._ctx._mode.name, self._ctx._mode._MAX_ENCRYPTED_BYTES
+                )
+            )
+
+    def update(self, data: bytes) -> bytes:
+        self._check_limit(len(data))
+        # mypy needs this assert even though _check_limit already checked
+        assert self._ctx is not None
+        return self._ctx.update(data)
+
+    def update_into(self, data: bytes, buf: bytes) -> int:
+        self._check_limit(len(data))
+        # mypy needs this assert even though _check_limit already checked
+        assert self._ctx is not None
+        return self._ctx.update_into(data, buf)
+
+    def finalize(self) -> bytes:
+        if self._ctx is None:
+            raise AlreadyFinalized("Context was already finalized.")
+        data = self._ctx.finalize()
+        self._tag = self._ctx.tag
+        self._ctx = None
+        return data
+
+    def authenticate_additional_data(self, data: bytes) -> None:
+        if self._ctx is None:
+            raise AlreadyFinalized("Context was already finalized.")
+        if self._updated:
+            raise AlreadyUpdated("Update has been called on this context.")
+
+        self._aad_bytes_processed += len(data)
+        if self._aad_bytes_processed > self._ctx._mode._MAX_AAD_BYTES:
+            raise ValueError(
+                "{} has a maximum AAD byte limit of {}".format(
+                    self._ctx._mode.name, self._ctx._mode._MAX_AAD_BYTES
+                )
+            )
+
+        self._ctx.authenticate_additional_data(data)
+
+
+class _AEADDecryptionContext(_AEADCipherContext, AEADDecryptionContext):
+    def finalize_with_tag(self, tag: bytes) -> bytes:
+        if self._ctx is None:
+            raise AlreadyFinalized("Context was already finalized.")
+        data = self._ctx.finalize_with_tag(tag)
+        self._tag = self._ctx.tag
+        self._ctx = None
+        return data
+
+
+class _AEADEncryptionContext(_AEADCipherContext, AEADEncryptionContext):
+    @property
+    def tag(self) -> bytes:
+        if self._ctx is not None:
+            raise NotYetFinalized(
+                "You must finalize encryption before " "getting the tag."
+            )
+        assert self._tag is not None
+        return self._tag