Source code for cryptography.hazmat.primitives.padding

# 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


[docs]@six.add_metaclass(abc.ABCMeta) class PaddingContext(object):
[docs] @abc.abstractmethod def update(self, data): """ Pads the provided bytes and returns any available data as bytes. """
[docs] @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_byteslike("data", data) buffer_ += bytes(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_byteslike("data", data) buffer_ += bytes(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]
[docs]class PKCS7(object): def __init__(self, block_size): _byte_padding_check(block_size) self.block_size = block_size
[docs] def padder(self): return _PKCS7PaddingContext(self.block_size)
[docs] 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
[docs]class ANSIX923(object): def __init__(self, block_size): _byte_padding_check(block_size) self.block_size = block_size
[docs] def padder(self): return _ANSIX923PaddingContext(self.block_size)
[docs] 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