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