#! /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
[docs]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
[docs]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)
[docs]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)
[docs]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'+/')
[docs]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)
[docs]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()])
[docs]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
[docs]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.
[docs]def b16encode(s):
"""Encode a string using Base16.
s is the string to encode. The encoded string is returned.
"""
return binascii.hexlify(s).upper()
[docs]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
[docs]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)
[docs]def decode(input, output):
"""Decode a file."""
while True:
line = input.readline()
if not line:
break
s = binascii.a2b_base64(line)
output.write(s)
[docs]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)
[docs]def decodestring(s):
"""Decode a string."""
return binascii.a2b_base64(s)
# Useable as a script...
[docs]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)
[docs]def test1():
s0 = "Aladdin:open sesame"
s1 = encodestring(s0)
s2 = decodestring(s1)
print s0, repr(s1), s2
if __name__ == '__main__':
test()