225 lines
6.1 KiB
Python
225 lines
6.1 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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import abc
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import typing
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from cryptography import utils
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from cryptography.exceptions import AlreadyFinalized
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from cryptography.hazmat.bindings._rust import (
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check_ansix923_padding,
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check_pkcs7_padding,
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)
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class PaddingContext(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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Pads the provided bytes and returns any available data as bytes.
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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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Finalize the padding, returns bytes.
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"""
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def _byte_padding_check(block_size: int) -> None:
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if not (0 <= block_size <= 2040):
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raise ValueError("block_size must be in range(0, 2041).")
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if block_size % 8 != 0:
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raise ValueError("block_size must be a multiple of 8.")
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def _byte_padding_update(
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buffer_: typing.Optional[bytes], data: bytes, block_size: int
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) -> typing.Tuple[bytes, bytes]:
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if buffer_ is None:
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raise AlreadyFinalized("Context was already finalized.")
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utils._check_byteslike("data", data)
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buffer_ += bytes(data)
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finished_blocks = len(buffer_) // (block_size // 8)
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result = buffer_[: finished_blocks * (block_size // 8)]
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buffer_ = buffer_[finished_blocks * (block_size // 8) :]
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return buffer_, result
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def _byte_padding_pad(
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buffer_: typing.Optional[bytes],
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block_size: int,
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paddingfn: typing.Callable[[int], bytes],
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) -> bytes:
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if buffer_ is None:
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raise AlreadyFinalized("Context was already finalized.")
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pad_size = block_size // 8 - len(buffer_)
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return buffer_ + paddingfn(pad_size)
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def _byte_unpadding_update(
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buffer_: typing.Optional[bytes], data: bytes, block_size: int
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) -> typing.Tuple[bytes, bytes]:
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if buffer_ is None:
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raise AlreadyFinalized("Context was already finalized.")
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utils._check_byteslike("data", data)
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buffer_ += bytes(data)
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finished_blocks = max(len(buffer_) // (block_size // 8) - 1, 0)
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result = buffer_[: finished_blocks * (block_size // 8)]
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buffer_ = buffer_[finished_blocks * (block_size // 8) :]
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return buffer_, result
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def _byte_unpadding_check(
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buffer_: typing.Optional[bytes],
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block_size: int,
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checkfn: typing.Callable[[bytes], int],
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) -> bytes:
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if buffer_ is None:
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raise AlreadyFinalized("Context was already finalized.")
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if len(buffer_) != block_size // 8:
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raise ValueError("Invalid padding bytes.")
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valid = checkfn(buffer_)
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if not valid:
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raise ValueError("Invalid padding bytes.")
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pad_size = buffer_[-1]
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return buffer_[:-pad_size]
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class PKCS7:
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def __init__(self, block_size: int):
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_byte_padding_check(block_size)
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self.block_size = block_size
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def padder(self) -> PaddingContext:
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return _PKCS7PaddingContext(self.block_size)
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def unpadder(self) -> PaddingContext:
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return _PKCS7UnpaddingContext(self.block_size)
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class _PKCS7PaddingContext(PaddingContext):
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_buffer: typing.Optional[bytes]
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def __init__(self, block_size: int):
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self.block_size = block_size
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# TODO: more copies than necessary, we should use zero-buffer (#193)
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self._buffer = b""
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def update(self, data: bytes) -> bytes:
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self._buffer, result = _byte_padding_update(
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self._buffer, data, self.block_size
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)
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return result
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def _padding(self, size: int) -> bytes:
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return bytes([size]) * size
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def finalize(self) -> bytes:
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result = _byte_padding_pad(
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self._buffer, self.block_size, self._padding
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)
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self._buffer = None
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return result
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class _PKCS7UnpaddingContext(PaddingContext):
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_buffer: typing.Optional[bytes]
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def __init__(self, block_size: int):
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self.block_size = block_size
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# TODO: more copies than necessary, we should use zero-buffer (#193)
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self._buffer = b""
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def update(self, data: bytes) -> bytes:
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self._buffer, result = _byte_unpadding_update(
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self._buffer, data, self.block_size
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)
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return result
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def finalize(self) -> bytes:
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result = _byte_unpadding_check(
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self._buffer, self.block_size, check_pkcs7_padding
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)
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self._buffer = None
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return result
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class ANSIX923:
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def __init__(self, block_size: int):
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_byte_padding_check(block_size)
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self.block_size = block_size
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def padder(self) -> PaddingContext:
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return _ANSIX923PaddingContext(self.block_size)
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def unpadder(self) -> PaddingContext:
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return _ANSIX923UnpaddingContext(self.block_size)
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class _ANSIX923PaddingContext(PaddingContext):
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_buffer: typing.Optional[bytes]
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def __init__(self, block_size: int):
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self.block_size = block_size
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# TODO: more copies than necessary, we should use zero-buffer (#193)
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self._buffer = b""
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def update(self, data: bytes) -> bytes:
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self._buffer, result = _byte_padding_update(
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self._buffer, data, self.block_size
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)
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return result
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def _padding(self, size: int) -> bytes:
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return bytes([0]) * (size - 1) + bytes([size])
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def finalize(self) -> bytes:
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result = _byte_padding_pad(
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self._buffer, self.block_size, self._padding
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)
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self._buffer = None
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return result
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class _ANSIX923UnpaddingContext(PaddingContext):
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_buffer: typing.Optional[bytes]
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def __init__(self, block_size: int):
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self.block_size = block_size
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# TODO: more copies than necessary, we should use zero-buffer (#193)
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self._buffer = b""
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def update(self, data: bytes) -> bytes:
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self._buffer, result = _byte_unpadding_update(
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self._buffer, data, self.block_size
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)
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return result
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def finalize(self) -> bytes:
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result = _byte_unpadding_check(
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self._buffer,
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self.block_size,
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check_ansix923_padding,
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)
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self._buffer = None
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return result
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