125 lines
3.5 KiB
Python
125 lines
3.5 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 absolute_import, division, print_function
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import abc
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import six
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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._padding import lib
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@six.add_metaclass(abc.ABCMeta)
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class PaddingContext(object):
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@abc.abstractmethod
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def update(self, data):
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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):
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"""
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Finalize the padding, returns bytes.
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"""
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class PKCS7(object):
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def __init__(self, block_size):
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if not (0 <= block_size < 256):
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raise ValueError("block_size must be in range(0, 256).")
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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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self.block_size = block_size
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def padder(self):
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return _PKCS7PaddingContext(self.block_size)
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def unpadder(self):
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return _PKCS7UnpaddingContext(self.block_size)
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@utils.register_interface(PaddingContext)
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class _PKCS7PaddingContext(object):
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def __init__(self, block_size):
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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):
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if self._buffer is None:
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raise AlreadyFinalized("Context was already finalized.")
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if not isinstance(data, bytes):
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raise TypeError("data must be bytes.")
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self._buffer += data
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finished_blocks = len(self._buffer) // (self.block_size // 8)
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result = self._buffer[:finished_blocks * (self.block_size // 8)]
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self._buffer = self._buffer[finished_blocks * (self.block_size // 8):]
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return result
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def finalize(self):
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if self._buffer is None:
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raise AlreadyFinalized("Context was already finalized.")
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pad_size = self.block_size // 8 - len(self._buffer)
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result = self._buffer + six.int2byte(pad_size) * pad_size
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self._buffer = None
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return result
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@utils.register_interface(PaddingContext)
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class _PKCS7UnpaddingContext(object):
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def __init__(self, block_size):
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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):
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if self._buffer is None:
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raise AlreadyFinalized("Context was already finalized.")
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if not isinstance(data, bytes):
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raise TypeError("data must be bytes.")
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self._buffer += data
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finished_blocks = max(
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len(self._buffer) // (self.block_size // 8) - 1,
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0
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)
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result = self._buffer[:finished_blocks * (self.block_size // 8)]
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self._buffer = self._buffer[finished_blocks * (self.block_size // 8):]
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return result
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def finalize(self):
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if self._buffer is None:
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raise AlreadyFinalized("Context was already finalized.")
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if len(self._buffer) != self.block_size // 8:
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raise ValueError("Invalid padding bytes.")
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valid = lib.Cryptography_check_pkcs7_padding(
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self._buffer, self.block_size // 8
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)
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if not valid:
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raise ValueError("Invalid padding bytes.")
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pad_size = six.indexbytes(self._buffer, -1)
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res = self._buffer[:-pad_size]
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self._buffer = None
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return res
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