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| # ============================================================================= |
| # 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() |