# =============================================================================
# Copyright (c) 2008 Christophe Oosterlynck <christophe.oosterlynck_AT_gmail.com>
# & NXP ( Philippe Teuwen <philippe.teuwen_AT_nxp.com> )
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
# THE SOFTWARE.
# =============================================================================
"""Module for padding functions
padding info here: http://en.wikipedia.org/wiki/Padding_(cryptography)
"""
import random
PAD = 0
UNPAD = 1
def bitPadding (padData, direction, length=None):
"""Pad a string using bitPadding
padData = raw string to pad/unpad
direction = PAD or UNPAD
length = amount of bytes the padded string should be a multiple of
(length variable is not used when unpadding)
returns: (un)padded raw string
A new block full of padding will be added when padding data that is
already a multiple of the length.
Example:
=========
>>> import padding
>>> padding.bitPadding('test', padding.PAD, 8)
'test\\x80\\x00\\x00\\x00'
>>> padding.bitPadding(_,padding.UNPAD)
'test'"""
if direction == PAD:
if length == None:
raise ValueError,"Supply a valid length"
return __bitPadding(padData, length)
elif direction == UNPAD:
return __bitPadding_unpad(padData)
else:
raise ValueError,"Supply a valid direction"
def __bitPadding (toPad,length):
padded = toPad + '\x80' + '\x00'*(length - len(toPad)%length -1)
return padded
def __bitPadding_unpad (padded):
if padded.rstrip('\x00')[-1] == '\x80':
return padded.rstrip('\x00')[:-1]
else:
return padded
def zerosPadding (padData, direction, length=None):
"""Pad a string using zerosPadding
padData = raw string to pad/unpad
direction = PAD or UNPAD
beware: padding and unpadding a string ending in 0's
will remove those 0's too
length = amount of bytes the padded string should be a multiple of
(length variable is not used when unpadding)
returns: (un)padded raw string
No padding will be added when padding data that is already a
multiple of the given length.
Example:
=========
>>> import padding
>>> padding.zerosPadding('12345678',padding.PAD,16)
'12345678\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00'
>>> padding.zerosPadding(_,padding.UNPAD)
'12345678'"""
if direction == PAD:
if length == None:
raise ValueError,"Supply a valid length"
return __zerosPadding(padData, length)
elif direction == UNPAD:
return __zerosPadding_unpad(padData)
else:
raise ValueError,"Supply a valid direction"
def __zerosPadding (toPad, length):
padLength = (length - len(toPad))%length
return toPad + '\x00'*padLength
def __zerosPadding_unpad (padded ):
return padded.rstrip('\x00')
def PKCS7(padData, direction, length=None):
"""Pad a string using PKCS7
padData = raw string to pad/unpad
direction = PAD or UNPAD
length = amount of bytes the padded string should be a multiple of
(length variable is not used when unpadding)
returns: (un)padded raw string
A new block full of padding will be added when padding data that is
already a multiple of the given length.
Example:
=========
>>> import padding
>>> padding.PKCS7('12345678',padding.PAD,16)
'12345678\\x08\\x08\\x08\\x08\\x08\\x08\\x08\\x08'
>>> padding.PKCS7(_,padding.UNPAD)
'12345678'"""
if direction == PAD:
if length == None:
raise ValueError,"Supply a valid length"
return __PKCS7(padData, length)
elif direction == UNPAD:
return __PKCS7_unpad(padData)
else:
raise ValueError,"Supply a valid direction"
def __PKCS7 (toPad, length):
amount = length - len(toPad)%length
pattern = chr(amount)
pad = pattern*amount
return toPad + pad
def __PKCS7_unpad (padded):
pattern = padded[-1]
length = ord(pattern)
#check if the bytes to be removed are all the same pattern
if padded.endswith(pattern*length):
return padded[:-length]
else:
return padded
print 'error: padding pattern not recognized'
def ANSI_X923 (padData, direction, length=None):
"""Pad a string using ANSI_X923
padData = raw string to pad/unpad
direction = PAD or UNPAD
length = amount of bytes the padded string should be a multiple of
(length variable is not used when unpadding)
returns: (un)padded raw string
A new block full of padding will be added when padding data that is
already a multiple of the given length.
Example:
=========
>>> import padding
>>> padding.ANSI_X923('12345678',padding.PAD,16)
'12345678\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x08'
>>> padding.ANSI_X923(_,padding.UNPAD)
'12345678'"""
if direction == PAD:
if length == None:
raise ValueError,"Supply a valid length"
return __ANSI_X923(padData, length)
elif direction == UNPAD:
return __ANSI_X923_unpad(padData)
else:
raise ValueError,"Supply a valid direction"
def __ANSI_X923 (toPad, length):
bytesToPad = length - len(toPad)%length
trail = chr(bytesToPad)
pattern = '\x00'*(bytesToPad -1) + trail
return toPad + pattern
def __ANSI_X923_unpad (padded):
length =ord(padded[-1])
#check if the bytes to be removed are all zero
if padded.count('\x00',-length,-1) == length - 1:
return padded[:-length]
else:
print 'error: padding pattern not recognized %s' % padded.count('\x00',-length,-1)
return padded
def ISO_10126 (padData, direction, length=None):
"""Pad a string using ISO_10126
padData = raw string to pad/unpad
direction = PAD or UNPAD
length = amount of bytes the padded string should be a multiple of
(length variable is not used when unpadding)
returns: (un)padded raw string
A new block full of padding will be added when padding data that is
already a multiple of the given length.
Example:
=========
>>> import padding
>>> padded = padding.ISO_10126('12345678',padding.PAD,16)
>>> padding.ISO_10126(padded,padding.UNPAD)
'12345678'"""
if direction == PAD:
if length == None:
raise ValueError,"Supply a valid length"
return __ISO_10126(padData, length)
elif direction == UNPAD:
return __ISO_10126_unpad(padData)
else:
raise ValueError,"Supply a valid direction"
def __ISO_10126 (toPad, length):
bytesToPad = length - len(toPad)%length
randomPattern = ''.join(chr(random.randint(0,255)) for x in range(0,bytesToPad-1))
return toPad + randomPattern + chr(bytesToPad)
def __ISO_10126_unpad (padded):
return padded[0:len(padded)-ord(padded[-1])]
def _test():
import doctest
doctest.testmod()
if __name__ == "__main__":
_test()