#! /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 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 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() |