#! /usr/bin/env python """RFC 3548: Base16, Base32, Base64 Data Encodings""" # Modified 04-Oct-1995 by Jack Jansen to use binascii module# Modified 30-Dec-2003 by Barry Warsaw to add full RFC 3548 support import reimport structimport binascii  __all__ = [    # Legacy interface exports traditional RFC 1521 Base64 encodings    'encode', 'decode', 'encodestring', 'decodestring',    # Generalized interface for other encodings    'b64encode', 'b64decode', 'b32encode', 'b32decode',    'b16encode', 'b16decode',    # Standard Base64 encoding    'standard_b64encode', 'standard_b64decode',    # Some common Base64 alternatives.  As referenced by RFC 3458, see thread    # starting at:    #    # http://zgp.org/pipermail/p2p-hackers/2001-September/000316.html    'urlsafe_b64encode', 'urlsafe_b64decode',    ] _translation = [chr(_x) for _x in range(256)]EMPTYSTRING = ''  def _translate(s, altchars):    translation = _translation[:]    for k, v in altchars.items():        translation[ord(k)] = v    return s.translate(''.join(translation))  # Base64 encoding/decoding uses binascii def b64encode(s, altchars=None):    """Encode a string using Base64.     s is the string to encode.  Optional altchars must be a string of at least    length 2 (additional characters are ignored) which specifies an    alternative alphabet for the '+' and '/' characters.  This allows an    application to e.g. generate url or filesystem safe Base64 strings.     The encoded string is returned.    """    # Strip off the trailing newline    encoded = binascii.b2a_base64(s)[:-1]    if altchars is not None:        return _translate(encoded, {'+': altchars[0], '/': altchars[1]})    return encoded  def b64decode(s, altchars=None):    """Decode a Base64 encoded string.     s is the string to decode.  Optional altchars must be a string of at least    length 2 (additional characters are ignored) which specifies the    alternative alphabet used instead of the '+' and '/' characters.     The decoded string is returned.  A TypeError is raised if s were    incorrectly padded or if there are non-alphabet characters present in the    string.    """    if altchars is not None:        s = _translate(s, {altchars[0]: '+', altchars[1]: '/'})    try:        return binascii.a2b_base64(s)    except binascii.Error, msg:        # Transform this exception for consistency        raise TypeError(msg)  def standard_b64encode(s):    """Encode a string using the standard Base64 alphabet.     s is the string to encode.  The encoded string is returned.    """    return b64encode(s) def standard_b64decode(s):    """Decode a string encoded with the standard Base64 alphabet.     s is the string to decode.  The decoded string is returned.  A TypeError    is raised if the string is incorrectly padded or if there are non-alphabet    characters present in the string.    """    return b64decode(s) def urlsafe_b64encode(s):    """Encode a string using a url-safe Base64 alphabet.     s is the string to encode.  The encoded string is returned.  The alphabet    uses '-' instead of '+' and '_' instead of '/'.    """    return b64encode(s, '-_') def urlsafe_b64decode(s):    """Decode a string encoded with the standard Base64 alphabet.     s is the string to decode.  The decoded string is returned.  A TypeError    is raised if the string is incorrectly padded or if there are non-alphabet    characters present in the string.     The alphabet uses '-' instead of '+' and '_' instead of '/'.    """    return b64decode(s, '-_')  # Base32 encoding/decoding must be done in Python_b32alphabet = {    0: 'A',  9: 'J', 18: 'S', 27: '3',    1: 'B', 10: 'K', 19: 'T', 28: '4',    2: 'C', 11: 'L', 20: 'U', 29: '5',    3: 'D', 12: 'M', 21: 'V', 30: '6',    4: 'E', 13: 'N', 22: 'W', 31: '7',    5: 'F', 14: 'O', 23: 'X',    6: 'G', 15: 'P', 24: 'Y',    7: 'H', 16: 'Q', 25: 'Z',    8: 'I', 17: 'R', 26: '2',    } _b32tab = _b32alphabet.items()_b32tab.sort()_b32tab = [v for k, v in _b32tab]_b32rev = dict([(v, long(k)) for k, v in _b32alphabet.items()])  def b32encode(s):    """Encode a string using Base32.     s is the string to encode.  The encoded string is returned.    """    parts = []    quanta, leftover = divmod(len(s), 5)    # Pad the last quantum with zero bits if necessary    if leftover:        s += ('\0' * (5 - leftover))        quanta += 1    for i in range(quanta):        # c1 and c2 are 16 bits wide, c3 is 8 bits wide.  The intent of this        # code is to process the 40 bits in units of 5 bits.  So we take the 1        # leftover bit of c1 and tack it onto c2.  Then we take the 2 leftover        # bits of c2 and tack them onto c3.  The shifts and masks are intended        # to give us values of exactly 5 bits in width.        c1, c2, c3 = struct.unpack('!HHB', s[i*5:(i+1)*5])        c2 += (c1 & 1) << 16 # 17 bits wide        c3 += (c2 & 3) << 8  # 10 bits wide        parts.extend([_b32tab[c1 >> 11],         # bits 1 - 5                      _b32tab[(c1 >> 6) & 0x1f], # bits 6 - 10                      _b32tab[(c1 >> 1) & 0x1f], # bits 11 - 15                      _b32tab[c2 >> 12],         # bits 16 - 20 (1 - 5)                      _b32tab[(c2 >> 7) & 0x1f], # bits 21 - 25 (6 - 10)                      _b32tab[(c2 >> 2) & 0x1f], # bits 26 - 30 (11 - 15)                      _b32tab[c3 >> 5],          # bits 31 - 35 (1 - 5)                      _b32tab[c3 & 0x1f],        # bits 36 - 40 (1 - 5)                      ])    encoded = EMPTYSTRING.join(parts)    # Adjust for any leftover partial quanta    if leftover == 1:        return encoded[:-6] + '======'    elif leftover == 2:        return encoded[:-4] + '===='    elif leftover == 3:        return encoded[:-3] + '==='    elif leftover == 4:        return encoded[:-1] + '='    return encoded  def b32decode(s, casefold=False, map01=None):    """Decode a Base32 encoded string.     s is the string to decode.  Optional casefold is a flag specifying whether    a lowercase alphabet is acceptable as input.  For security purposes, the    default is False.     RFC 3548 allows for optional mapping of the digit 0 (zero) to the letter O    (oh), and for optional mapping of the digit 1 (one) to either the letter I    (eye) or letter L (el).  The optional argument map01 when not None,    specifies which letter the digit 1 should be mapped to (when map01 is not    None, the digit 0 is always mapped to the letter O).  For security    purposes the default is None, so that 0 and 1 are not allowed in the    input.     The decoded string is returned.  A TypeError is raised if s were    incorrectly padded or if there are non-alphabet characters present in the    string.    """    quanta, leftover = divmod(len(s), 8)    if leftover:        raise TypeError('Incorrect padding')    # Handle section 2.4 zero and one mapping.  The flag map01 will be either    # False, or the character to map the digit 1 (one) to.  It should be    # either L (el) or I (eye).    if map01:        s = _translate(s, {'0': 'O', '1': map01})    if casefold:        s = s.upper()    # Strip off pad characters from the right.  We need to count the pad    # characters because this will tell us how many null bytes to remove from    # the end of the decoded string.    padchars = 0    mo = re.search('(?P<pad>[=]*)$', s)    if mo:        padchars = len(mo.group('pad'))        if padchars > 0:            s = s[:-padchars]    # Now decode the full quanta    parts = []    acc = 0    shift = 35    for c in s:        val = _b32rev.get(c)        if val is None:            raise TypeError('Non-base32 digit found')        acc += _b32rev[c] << shift        shift -= 5        if shift < 0:            parts.append(binascii.unhexlify('%010x' % acc))            acc = 0            shift = 35    # Process the last, partial quanta    last = binascii.unhexlify('%010x' % acc)    if padchars == 0:        last = ''                       # No characters    elif padchars == 1:        last = last[:-1]    elif padchars == 3:        last = last[:-2]    elif padchars == 4:        last = last[:-3]    elif padchars == 6:        last = last[:-4]    else:        raise TypeError('Incorrect padding')    parts.append(last)    return EMPTYSTRING.join(parts)  # RFC 3548, Base 16 Alphabet specifies uppercase, but hexlify() returns# lowercase.  The RFC also recommends against accepting input case# insensitively.def b16encode(s):    """Encode a string using Base16.     s is the string to encode.  The encoded string is returned.    """    return binascii.hexlify(s).upper()  def b16decode(s, casefold=False):    """Decode a Base16 encoded string.     s is the string to decode.  Optional casefold is a flag specifying whether    a lowercase alphabet is acceptable as input.  For security purposes, the    default is False.     The decoded string is returned.  A TypeError is raised if s were    incorrectly padded or if there are non-alphabet characters present in the    string.    """    if casefold:        s = s.upper()    if re.search('[^0-9A-F]', s):        raise TypeError('Non-base16 digit found')    return binascii.unhexlify(s)  # Legacy interface.  This code could be cleaned up since I don't believe# binascii has any line length limitations.  It just doesn't seem worth it# though. MAXLINESIZE = 76 # Excluding the CRLFMAXBINSIZE = (MAXLINESIZE//4)*3 def encode(input, output):    """Encode a file."""    while True:        s = input.read(MAXBINSIZE)        if not s:            break        while len(s) < MAXBINSIZE:            ns = input.read(MAXBINSIZE-len(s))            if not ns:                break            s += ns        line = binascii.b2a_base64(s)        output.write(line)  def decode(input, output):    """Decode a file."""    while True:        line = input.readline()        if not line:            break        s = binascii.a2b_base64(line)        output.write(s)  def encodestring(s):    """Encode a string."""    pieces = []    for i in range(0, len(s), MAXBINSIZE):        chunk = s[i : i + MAXBINSIZE]        pieces.append(binascii.b2a_base64(chunk))    return "".join(pieces)  def decodestring(s):    """Decode a string."""    return binascii.a2b_base64(s)  # Useable as a script...def test():    """Small test program"""    import sys, getopt    try:        opts, args = getopt.getopt(sys.argv[1:], 'deut')    except getopt.error, msg:        sys.stdout = sys.stderr        print msg        print """usage: %s [-d|-e|-u|-t] [file|-]        -d, -u: decode        -e: encode (default)        -t: encode and decode string 'Aladdin:open sesame'"""%sys.argv[0]        sys.exit(2)    func = encode    for o, a in opts:        if o == '-e': func = encode        if o == '-d': func = decode        if o == '-u': func = decode        if o == '-t': test1(); return    if args and args[0] != '-':        func(open(args[0], 'rb'), sys.stdout)    else:        func(sys.stdin, sys.stdout)  def test1():    s0 = "Aladdin:open sesame"    s1 = encodestring(s0)    s2 = decodestring(s1)    print s0, repr(s1), s2  if __name__ == '__main__':    test()