diff options
Diffstat (limited to 'Lib')
| -rwxr-xr-x | Lib/base64.py | 297 |
1 files changed, 288 insertions, 9 deletions
diff --git a/Lib/base64.py b/Lib/base64.py index 3158fdc..1ef797c 100755 --- a/Lib/base64.py +++ b/Lib/base64.py @@ -1,36 +1,309 @@ #! /usr/bin/env python -"""Conversions to/from base64 transport encoding as per RFC-1521.""" +"""RFC 3548: Base16, Base32, Base64 Data Encodings""" -# Modified 04-Oct-95 by Jack to use binascii module +# 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 binascii -__all__ = ["encode","decode","encodestring","decodestring"] + +__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 + 'freenet_b64encode', 'freenet_b64decode', + '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 = [v for v in _b32alphabet.values()] +_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(hex(acc)[2:-1])) + acc = 0 + shift = 35 + # Process the last, partial quanta + last = binascii.unhexlify(hex(acc)[2:-1]) + if padchars == 1: + last = last[:-1] + elif padchars == 3: + last = last[:-2] + elif padchars == 4: + last = last[:-3] + elif padchars == 6: + last = last[:-4] + elif padchars <> 0: + 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 CRLF MAXBINSIZE = (MAXLINESIZE//4)*3 def encode(input, output): """Encode a file.""" - while 1: + while True: s = input.read(MAXBINSIZE) - if not s: break + if not s: + break while len(s) < MAXBINSIZE: ns = input.read(MAXBINSIZE-len(s)) - if not ns: break - s = s + ns + if not ns: + break + s += ns line = binascii.b2a_base64(s) output.write(line) + def decode(input, output): """Decode a file.""" - while 1: + while True: line = input.readline() - if not line: break + if not line: + break s = binascii.a2b_base64(line) output.write(s) + def encodestring(s): """Encode a string.""" pieces = [] @@ -39,10 +312,14 @@ def encodestring(s): 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 @@ -67,11 +344,13 @@ def test(): else: func(sys.stdin, sys.stdout) + def test1(): s0 = "Aladdin:open sesame" s1 = encodestring(s0) s2 = decodestring(s1) print s0, `s1`, s2 + if __name__ == '__main__': test() |