forked from STI/Astroport.ONE
273 lines
8.2 KiB
Python
273 lines
8.2 KiB
Python
# This file is dual licensed under the terms of the Apache License, Version
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# 2.0, and the BSD License. See the LICENSE file in the root of this repository
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# for complete details.
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from __future__ import annotations
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import abc
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import typing
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from cryptography.exceptions import (
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AlreadyFinalized,
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AlreadyUpdated,
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NotYetFinalized,
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)
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from cryptography.hazmat.primitives._cipheralgorithm import CipherAlgorithm
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from cryptography.hazmat.primitives.ciphers import modes
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if typing.TYPE_CHECKING:
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from cryptography.hazmat.backends.openssl.ciphers import (
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_CipherContext as _BackendCipherContext,
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)
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class CipherContext(metaclass=abc.ABCMeta):
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@abc.abstractmethod
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def update(self, data: bytes) -> bytes:
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"""
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Processes the provided bytes through the cipher and returns the results
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as bytes.
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"""
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@abc.abstractmethod
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def update_into(self, data: bytes, buf: bytes) -> int:
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"""
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Processes the provided bytes and writes the resulting data into the
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provided buffer. Returns the number of bytes written.
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"""
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@abc.abstractmethod
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def finalize(self) -> bytes:
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"""
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Returns the results of processing the final block as bytes.
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"""
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class AEADCipherContext(CipherContext, metaclass=abc.ABCMeta):
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@abc.abstractmethod
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def authenticate_additional_data(self, data: bytes) -> None:
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"""
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Authenticates the provided bytes.
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"""
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class AEADDecryptionContext(AEADCipherContext, metaclass=abc.ABCMeta):
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@abc.abstractmethod
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def finalize_with_tag(self, tag: bytes) -> bytes:
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"""
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Returns the results of processing the final block as bytes and allows
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delayed passing of the authentication tag.
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"""
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class AEADEncryptionContext(AEADCipherContext, metaclass=abc.ABCMeta):
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@property
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@abc.abstractmethod
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def tag(self) -> bytes:
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"""
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Returns tag bytes. This is only available after encryption is
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finalized.
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"""
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Mode = typing.TypeVar(
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"Mode", bound=typing.Optional[modes.Mode], covariant=True
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)
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class Cipher(typing.Generic[Mode]):
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def __init__(
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self,
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algorithm: CipherAlgorithm,
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mode: Mode,
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backend: typing.Any = None,
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) -> None:
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if not isinstance(algorithm, CipherAlgorithm):
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raise TypeError("Expected interface of CipherAlgorithm.")
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if mode is not None:
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# mypy needs this assert to narrow the type from our generic
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# type. Maybe it won't some time in the future.
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assert isinstance(mode, modes.Mode)
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mode.validate_for_algorithm(algorithm)
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self.algorithm = algorithm
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self.mode = mode
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@typing.overload
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def encryptor(
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self: Cipher[modes.ModeWithAuthenticationTag],
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) -> AEADEncryptionContext:
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...
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@typing.overload
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def encryptor(
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self: _CIPHER_TYPE,
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) -> CipherContext:
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...
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def encryptor(self):
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if isinstance(self.mode, modes.ModeWithAuthenticationTag):
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if self.mode.tag is not None:
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raise ValueError(
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"Authentication tag must be None when encrypting."
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)
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from cryptography.hazmat.backends.openssl.backend import backend
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ctx = backend.create_symmetric_encryption_ctx(
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self.algorithm, self.mode
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)
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return self._wrap_ctx(ctx, encrypt=True)
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@typing.overload
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def decryptor(
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self: Cipher[modes.ModeWithAuthenticationTag],
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) -> AEADDecryptionContext:
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...
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@typing.overload
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def decryptor(
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self: _CIPHER_TYPE,
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) -> CipherContext:
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...
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def decryptor(self):
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from cryptography.hazmat.backends.openssl.backend import backend
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ctx = backend.create_symmetric_decryption_ctx(
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self.algorithm, self.mode
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)
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return self._wrap_ctx(ctx, encrypt=False)
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def _wrap_ctx(
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self, ctx: _BackendCipherContext, encrypt: bool
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) -> AEADEncryptionContext | AEADDecryptionContext | CipherContext:
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if isinstance(self.mode, modes.ModeWithAuthenticationTag):
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if encrypt:
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return _AEADEncryptionContext(ctx)
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else:
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return _AEADDecryptionContext(ctx)
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else:
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return _CipherContext(ctx)
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_CIPHER_TYPE = Cipher[
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typing.Union[
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modes.ModeWithNonce,
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modes.ModeWithTweak,
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None,
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modes.ECB,
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modes.ModeWithInitializationVector,
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]
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]
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class _CipherContext(CipherContext):
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_ctx: _BackendCipherContext | None
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def __init__(self, ctx: _BackendCipherContext) -> None:
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self._ctx = ctx
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def update(self, data: bytes) -> bytes:
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if self._ctx is None:
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raise AlreadyFinalized("Context was already finalized.")
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return self._ctx.update(data)
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def update_into(self, data: bytes, buf: bytes) -> int:
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if self._ctx is None:
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raise AlreadyFinalized("Context was already finalized.")
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return self._ctx.update_into(data, buf)
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def finalize(self) -> bytes:
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if self._ctx is None:
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raise AlreadyFinalized("Context was already finalized.")
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data = self._ctx.finalize()
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self._ctx = None
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return data
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class _AEADCipherContext(AEADCipherContext):
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_ctx: _BackendCipherContext | None
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_tag: bytes | None
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def __init__(self, ctx: _BackendCipherContext) -> None:
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self._ctx = ctx
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self._bytes_processed = 0
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self._aad_bytes_processed = 0
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self._tag = None
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self._updated = False
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def _check_limit(self, data_size: int) -> None:
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if self._ctx is None:
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raise AlreadyFinalized("Context was already finalized.")
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self._updated = True
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self._bytes_processed += data_size
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if self._bytes_processed > self._ctx._mode._MAX_ENCRYPTED_BYTES:
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raise ValueError(
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"{} has a maximum encrypted byte limit of {}".format(
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self._ctx._mode.name, self._ctx._mode._MAX_ENCRYPTED_BYTES
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)
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)
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def update(self, data: bytes) -> bytes:
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self._check_limit(len(data))
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# mypy needs this assert even though _check_limit already checked
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assert self._ctx is not None
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return self._ctx.update(data)
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def update_into(self, data: bytes, buf: bytes) -> int:
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self._check_limit(len(data))
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# mypy needs this assert even though _check_limit already checked
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assert self._ctx is not None
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return self._ctx.update_into(data, buf)
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def finalize(self) -> bytes:
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if self._ctx is None:
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raise AlreadyFinalized("Context was already finalized.")
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data = self._ctx.finalize()
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self._tag = self._ctx.tag
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self._ctx = None
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return data
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def authenticate_additional_data(self, data: bytes) -> None:
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if self._ctx is None:
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raise AlreadyFinalized("Context was already finalized.")
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if self._updated:
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raise AlreadyUpdated("Update has been called on this context.")
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self._aad_bytes_processed += len(data)
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if self._aad_bytes_processed > self._ctx._mode._MAX_AAD_BYTES:
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raise ValueError(
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"{} has a maximum AAD byte limit of {}".format(
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self._ctx._mode.name, self._ctx._mode._MAX_AAD_BYTES
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)
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)
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self._ctx.authenticate_additional_data(data)
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class _AEADDecryptionContext(_AEADCipherContext, AEADDecryptionContext):
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def finalize_with_tag(self, tag: bytes) -> bytes:
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if self._ctx is None:
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raise AlreadyFinalized("Context was already finalized.")
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if self._ctx._tag is not None:
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raise ValueError(
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"tag provided both in mode and in call with finalize_with_tag:"
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" tag should only be provided once"
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)
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data = self._ctx.finalize_with_tag(tag)
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self._tag = self._ctx.tag
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self._ctx = None
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return data
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class _AEADEncryptionContext(_AEADCipherContext, AEADEncryptionContext):
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@property
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def tag(self) -> bytes:
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if self._ctx is not None:
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raise NotYetFinalized(
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"You must finalize encryption before " "getting the tag."
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)
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assert self._tag is not None
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return self._tag
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