Editing: base64.py
#! /usr/bin/python2.7 """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 re import struct import string import 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 encoded.translate(string.maketrans(b'+/', altchars[:2])) 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 is incorrectly padded. Characters that are neither in the normal base-64 alphabet nor the alternative alphabet are discarded prior to the padding check. """ if altchars is not None: s = s.translate(string.maketrans(altchars[:2], '+/')) 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. Argument s is the string to decode. The decoded string is returned. A TypeError is raised if the string is incorrectly padded. Characters that are not in the standard alphabet are discarded prior to the padding check. """ return b64decode(s) _urlsafe_encode_translation = string.maketrans(b'+/', b'-_') _urlsafe_decode_translation = string.maketrans(b'-_', b'+/') def urlsafe_b64encode(s): """Encode a string using the URL- and filesystem-safe Base64 alphabet. Argument s is the string to encode. The encoded string is returned. The alphabet uses '-' instead of '+' and '_' instead of '/'. """ return b64encode(s).translate(_urlsafe_encode_translation) def urlsafe_b64decode(s): """Decode a string using the URL- and filesystem-safe Base64 alphabet. Argument s is the string to decode. The decoded string is returned. A TypeError is raised if the string is incorrectly padded. Characters that are not in the URL-safe base-64 alphabet, and are not a plus '+' or slash '/', are discarded prior to the padding check. The alphabet uses '-' instead of '+' and '_' instead of '/'. """ return b64decode(s.translate(_urlsafe_decode_translation)) # 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 = s.translate(string.maketrans(b'01', b'O' + 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 is 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 CRLF MAXBINSIZE = (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 into multiple lines of base-64 data.""" 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] != '-': with open(args[0], 'rb') as f: func(f, 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()
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