| #! /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 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. Non-base64-alphabet characters 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. |
| |
| 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) |
| |
| _urlsafe_encode_translation = string.maketrans(b'+/', b'-_') |
| _urlsafe_decode_translation = string.maketrans(b'-_', b'+/') |
| |
| 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).translate(_urlsafe_encode_translation) |
| |
| 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.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 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 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() |