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File Content: `Padding.py`

#
# Util/Padding.py :  Functions to manage padding
#
# ===================================================================
#
# Copyright (c) 2014, Legrandin <helderijs@gmail.com>
# All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions
# are met:
#
# 1. Redistributions of source code must retain the above copyright
#    notice, this list of conditions and the following disclaimer.
# 2. Redistributions in binary form must reproduce the above copyright
#    notice, this list of conditions and the following disclaimer in
#    the documentation and/or other materials provided with the
#    distribution.
#
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
# FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
# COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
# INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
# BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
# LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
# CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
# ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
# POSSIBILITY OF SUCH DAMAGE.
# ===================================================================

__all__ = [ 'pad', 'unpad' ]

from Crypto.Util.py3compat import *


def pad(data_to_pad, block_size, style='pkcs7'):
    """Apply standard padding.

    Args:
      data_to_pad (byte string):
        The data that needs to be padded.
      block_size (integer):
        The block boundary to use for padding. The output length is guaranteed
        to be a multiple of :data:`block_size`.
      style (string):
        Padding algorithm. It can be *'pkcs7'* (default), *'iso7816'* or *'x923'*.

    Return:
      byte string : the original data with the appropriate padding added at the end.
    """

    padding_len = block_size-len(data_to_pad)%block_size
    if style == 'pkcs7':
        padding = bchr(padding_len)*padding_len
    elif style == 'x923':
        padding = bchr(0)*(padding_len-1) + bchr(padding_len)
    elif style == 'iso7816':
        padding = bchr(128) + bchr(0)*(padding_len-1)
    else:
        raise ValueError("Unknown padding style")
    return data_to_pad + padding


def unpad(padded_data, block_size, style='pkcs7'):
    """Remove standard padding.

    Args:
      padded_data (byte string):
        A piece of data with padding that needs to be stripped.
      block_size (integer):
        The block boundary to use for padding. The input length
        must be a multiple of :data:`block_size`.
      style (string):
        Padding algorithm. It can be *'pkcs7'* (default), *'iso7816'* or *'x923'*.
    Return:
        byte string : data without padding.
    Raises:
      ValueError: if the padding is incorrect.
    """

    pdata_len = len(padded_data)
    if pdata_len == 0:
        raise ValueError("Zero-length input cannot be unpadded")
    if pdata_len % block_size:
        raise ValueError("Input data is not padded")
    if style in ('pkcs7', 'x923'):
        padding_len = bord(padded_data[-1])
        if padding_len<1 or padding_len>min(block_size, pdata_len):
            raise ValueError("Padding is incorrect.")
        if style == 'pkcs7':
            if padded_data[-padding_len:]!=bchr(padding_len)*padding_len:
                raise ValueError("PKCS#7 padding is incorrect.")
        else:
            if padded_data[-padding_len:-1]!=bchr(0)*(padding_len-1):
                raise ValueError("ANSI X.923 padding is incorrect.")
    elif style == 'iso7816':
        padding_len = pdata_len - padded_data.rfind(bchr(128))
        if padding_len<1 or padding_len>min(block_size, pdata_len):
            raise ValueError("Padding is incorrect.")
        if padding_len>1 and padded_data[1-padding_len:]!=bchr(0)*(padding_len-1):
            raise ValueError("ISO 7816-4 padding is incorrect.")
    else:
        raise ValueError("Unknown padding style")
    return padded_data[:-padding_len]

Name	Size	Permission
__pycache__	---	0755
Counter.py	3110 bytes	0644
Counter.pyi	290 bytes	0644
Padding.py	4313 bytes	0644
Padding.pyi	238 bytes	0644
RFC1751.py	21192 bytes	0644
RFC1751.pyi	159 bytes	0644
__init__.py	1927 bytes	0644
_cpu_features.py	1989 bytes	0644
_cpu_features.pyi	59 bytes	0644
_cpuid_c.abi3.so	19304 bytes	0755
_file_system.py	2171 bytes	0644
_file_system.pyi	100 bytes	0644
_raw_api.py	10226 bytes	0644
_raw_api.pyi	906 bytes	0644
_strxor.abi3.so	20376 bytes	0755
asn1.py	36169 bytes	0644
asn1.pyi	3805 bytes	0644
number.py	96371 bytes	0644
number.pyi	975 bytes	0644
py3compat.py	5526 bytes	0644
py3compat.pyi	837 bytes	0644
strxor.py	5441 bytes	0644
strxor.pyi	243 bytes	0644

File Content: Padding.py

File Content: `Padding.py`