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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 absolute_import, division, print_function
import abc
import six
from cryptography import utils
from cryptography.exceptions import AlreadyFinalized
from cryptography.hazmat.bindings._padding import lib
@six.add_metaclass(abc.ABCMeta)
class PaddingContext(object):
@abc.abstractmethod
def update(self, data):
"""
Pads the provided bytes and returns any available data as bytes.
"""
@abc.abstractmethod
def finalize(self):
"""
Finalize the padding, returns bytes.
"""
def _byte_padding_check(block_size):
if not (0 <= block_size <= 2040):
raise ValueError("block_size must be in range(0, 2041).")
if block_size % 8 != 0:
raise ValueError("block_size must be a multiple of 8.")
def _byte_padding_update(buffer_, data, block_size):
if buffer_ is None:
raise AlreadyFinalized("Context was already finalized.")
utils._check_bytes("data", data)
buffer_ += data
finished_blocks = len(buffer_) // (block_size // 8)
result = buffer_[:finished_blocks * (block_size // 8)]
buffer_ = buffer_[finished_blocks * (block_size // 8):]
return buffer_, result
def _byte_padding_pad(buffer_, block_size, paddingfn):
if buffer_ is None:
raise AlreadyFinalized("Context was already finalized.")
pad_size = block_size // 8 - len(buffer_)
return buffer_ + paddingfn(pad_size)
def _byte_unpadding_update(buffer_, data, block_size):
if buffer_ is None:
raise AlreadyFinalized("Context was already finalized.")
utils._check_bytes("data", data)
buffer_ += data
finished_blocks = max(len(buffer_) // (block_size // 8) - 1, 0)
result = buffer_[:finished_blocks * (block_size // 8)]
buffer_ = buffer_[finished_blocks * (block_size // 8):]
return buffer_, result
def _byte_unpadding_check(buffer_, block_size, checkfn):
if buffer_ is None:
raise AlreadyFinalized("Context was already finalized.")
if len(buffer_) != block_size // 8:
raise ValueError("Invalid padding bytes.")
valid = checkfn(buffer_, block_size // 8)
if not valid:
raise ValueError("Invalid padding bytes.")
pad_size = six.indexbytes(buffer_, -1)
return buffer_[:-pad_size]
class PKCS7(object):
def __init__(self, block_size):
_byte_padding_check(block_size)
self.block_size = block_size
def padder(self):
return _PKCS7PaddingContext(self.block_size)
def unpadder(self):
return _PKCS7UnpaddingContext(self.block_size)
@utils.register_interface(PaddingContext)
class _PKCS7PaddingContext(object):
def __init__(self, block_size):
self.block_size = block_size
# TODO: more copies than necessary, we should use zero-buffer (#193)
self._buffer = b""
def update(self, data):
self._buffer, result = _byte_padding_update(
self._buffer, data, self.block_size)
return result
def _padding(self, size):
return six.int2byte(size) * size
def finalize(self):
result = _byte_padding_pad(
self._buffer, self.block_size, self._padding)
self._buffer = None
return result
@utils.register_interface(PaddingContext)
class _PKCS7UnpaddingContext(object):
def __init__(self, block_size):
self.block_size = block_size
# TODO: more copies than necessary, we should use zero-buffer (#193)
self._buffer = b""
def update(self, data):
self._buffer, result = _byte_unpadding_update(
self._buffer, data, self.block_size)
return result
def finalize(self):
result = _byte_unpadding_check(
self._buffer, self.block_size,
lib.Cryptography_check_pkcs7_padding)
self._buffer = None
return result
class ANSIX923(object):
def __init__(self, block_size):
_byte_padding_check(block_size)
self.block_size = block_size
def padder(self):
return _ANSIX923PaddingContext(self.block_size)
def unpadder(self):
return _ANSIX923UnpaddingContext(self.block_size)
@utils.register_interface(PaddingContext)
class _ANSIX923PaddingContext(object):
def __init__(self, block_size):
self.block_size = block_size
# TODO: more copies than necessary, we should use zero-buffer (#193)
self._buffer = b""
def update(self, data):
self._buffer, result = _byte_padding_update(
self._buffer, data, self.block_size)
return result
def _padding(self, size):
return six.int2byte(0) * (size - 1) + six.int2byte(size)
def finalize(self):
result = _byte_padding_pad(
self._buffer, self.block_size, self._padding)
self._buffer = None
return result
@utils.register_interface(PaddingContext)
class _ANSIX923UnpaddingContext(object):
def __init__(self, block_size):
self.block_size = block_size
# TODO: more copies than necessary, we should use zero-buffer (#193)
self._buffer = b""
def update(self, data):
self._buffer, result = _byte_unpadding_update(
self._buffer, data, self.block_size)
return result
def finalize(self):
result = _byte_unpadding_check(
self._buffer, self.block_size,
lib.Cryptography_check_ansix923_padding)
self._buffer = None
return result
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