3 """RFC 3548: Base16, Base32, Base64 Data Encodings"""
5 # Modified 04-Oct-1995 by Jack Jansen to use binascii module
6 # Modified 30-Dec-2003 by Barry Warsaw to add full RFC 3548 support
14 # Legacy interface exports traditional RFC 1521 Base64 encodings
15 'encode', 'decode', 'encodestring', 'decodestring',
16 # Generalized interface for other encodings
17 'b64encode', 'b64decode', 'b32encode', 'b32decode',
18 'b16encode', 'b16decode',
19 # Standard Base64 encoding
20 'standard_b64encode', 'standard_b64decode',
21 # Some common Base64 alternatives. As referenced by RFC 3458, see thread
24 # http://zgp.org/pipermail/p2p-hackers/2001-September/000316.html
25 'urlsafe_b64encode', 'urlsafe_b64decode',
28 _translation
= [chr(_x
) for _x
in range(256)]
32 def _translate(s
, altchars
):
33 translation
= _translation
[:]
34 for k
, v
in altchars
.items():
35 translation
[ord(k
)] = v
36 return s
.translate(''.join(translation
))
40 # Base64 encoding/decoding uses binascii
42 def b64encode(s
, altchars
=None):
43 """Encode a string using Base64.
45 s is the string to encode. Optional altchars must be a string of at least
46 length 2 (additional characters are ignored) which specifies an
47 alternative alphabet for the '+' and '/' characters. This allows an
48 application to e.g. generate url or filesystem safe Base64 strings.
50 The encoded string is returned.
52 # Strip off the trailing newline
53 encoded
= binascii
.b2a_base64(s
)[:-1]
54 if altchars
is not None:
55 return _translate(encoded
, {'+': altchars
[0], '/': altchars
[1]})
59 def b64decode(s
, altchars
=None):
60 """Decode a Base64 encoded string.
62 s is the string to decode. Optional altchars must be a string of at least
63 length 2 (additional characters are ignored) which specifies the
64 alternative alphabet used instead of the '+' and '/' characters.
66 The decoded string is returned. A TypeError is raised if s were
67 incorrectly padded or if there are non-alphabet characters present in the
70 if altchars
is not None:
71 s
= _translate(s
, {altchars
[0]: '+', altchars
[1]: '/'})
73 return binascii
.a2b_base64(s
)
74 except binascii
.Error
, msg
:
75 # Transform this exception for consistency
79 def standard_b64encode(s
):
80 """Encode a string using the standard Base64 alphabet.
82 s is the string to encode. The encoded string is returned.
86 def standard_b64decode(s
):
87 """Decode a string encoded with the standard Base64 alphabet.
89 s is the string to decode. The decoded string is returned. A TypeError
90 is raised if the string is incorrectly padded or if there are non-alphabet
91 characters present in the string.
95 def urlsafe_b64encode(s
):
96 """Encode a string using a url-safe Base64 alphabet.
98 s is the string to encode. The encoded string is returned. The alphabet
99 uses '-' instead of '+' and '_' instead of '/'.
101 return b64encode(s
, '-_')
103 def urlsafe_b64decode(s
):
104 """Decode a string encoded with the standard Base64 alphabet.
106 s is the string to decode. The decoded string is returned. A TypeError
107 is raised if the string is incorrectly padded or if there are non-alphabet
108 characters present in the string.
110 The alphabet uses '-' instead of '+' and '_' instead of '/'.
112 return b64decode(s
, '-_')
116 # Base32 encoding/decoding must be done in Python
118 0: 'A', 9: 'J', 18: 'S', 27: '3',
119 1: 'B', 10: 'K', 19: 'T', 28: '4',
120 2: 'C', 11: 'L', 20: 'U', 29: '5',
121 3: 'D', 12: 'M', 21: 'V', 30: '6',
122 4: 'E', 13: 'N', 22: 'W', 31: '7',
123 5: 'F', 14: 'O', 23: 'X',
124 6: 'G', 15: 'P', 24: 'Y',
125 7: 'H', 16: 'Q', 25: 'Z',
126 8: 'I', 17: 'R', 26: '2',
129 _b32tab
= _b32alphabet
.items()
131 _b32tab
= [v
for k
, v
in _b32tab
]
132 _b32rev
= dict([(v
, long(k
)) for k
, v
in _b32alphabet
.items()])
136 """Encode a string using Base32.
138 s is the string to encode. The encoded string is returned.
141 quanta
, leftover
= divmod(len(s
), 5)
142 # Pad the last quantum with zero bits if necessary
144 s
+= ('\0' * (5 - leftover
))
146 for i
in range(quanta
):
147 # c1 and c2 are 16 bits wide, c3 is 8 bits wide. The intent of this
148 # code is to process the 40 bits in units of 5 bits. So we take the 1
149 # leftover bit of c1 and tack it onto c2. Then we take the 2 leftover
150 # bits of c2 and tack them onto c3. The shifts and masks are intended
151 # to give us values of exactly 5 bits in width.
152 c1
, c2
, c3
= struct
.unpack('!HHB', s
[i
*5:(i
+1)*5])
153 c2
+= (c1
& 1) << 16 # 17 bits wide
154 c3
+= (c2
& 3) << 8 # 10 bits wide
155 parts
.extend([_b32tab
[c1
>> 11], # bits 1 - 5
156 _b32tab
[(c1
>> 6) & 0x1f], # bits 6 - 10
157 _b32tab
[(c1
>> 1) & 0x1f], # bits 11 - 15
158 _b32tab
[c2
>> 12], # bits 16 - 20 (1 - 5)
159 _b32tab
[(c2
>> 7) & 0x1f], # bits 21 - 25 (6 - 10)
160 _b32tab
[(c2
>> 2) & 0x1f], # bits 26 - 30 (11 - 15)
161 _b32tab
[c3
>> 5], # bits 31 - 35 (1 - 5)
162 _b32tab
[c3
& 0x1f], # bits 36 - 40 (1 - 5)
164 encoded
= EMPTYSTRING
.join(parts
)
165 # Adjust for any leftover partial quanta
167 return encoded
[:-6] + '======'
169 return encoded
[:-4] + '===='
171 return encoded
[:-3] + '==='
173 return encoded
[:-1] + '='
177 def b32decode(s
, casefold
=False, map01
=None):
178 """Decode a Base32 encoded string.
180 s is the string to decode. Optional casefold is a flag specifying whether
181 a lowercase alphabet is acceptable as input. For security purposes, the
184 RFC 3548 allows for optional mapping of the digit 0 (zero) to the letter O
185 (oh), and for optional mapping of the digit 1 (one) to either the letter I
186 (eye) or letter L (el). The optional argument map01 when not None,
187 specifies which letter the digit 1 should be mapped to (when map01 is not
188 None, the digit 0 is always mapped to the letter O). For security
189 purposes the default is None, so that 0 and 1 are not allowed in the
192 The decoded string is returned. A TypeError is raised if s were
193 incorrectly padded or if there are non-alphabet characters present in the
196 quanta
, leftover
= divmod(len(s
), 8)
198 raise TypeError('Incorrect padding')
199 # Handle section 2.4 zero and one mapping. The flag map01 will be either
200 # False, or the character to map the digit 1 (one) to. It should be
201 # either L (el) or I (eye).
203 s
= _translate(s
, {'0': 'O', '1': map01
})
206 # Strip off pad characters from the right. We need to count the pad
207 # characters because this will tell us how many null bytes to remove from
208 # the end of the decoded string.
210 mo
= re
.search('(?P<pad>[=]*)$', s
)
212 padchars
= len(mo
.group('pad'))
215 # Now decode the full quanta
222 raise TypeError('Non-base32 digit found')
223 acc
+= _b32rev
[c
] << shift
226 parts
.append(binascii
.unhexlify('%010x' % acc
))
229 # Process the last, partial quanta
230 last
= binascii
.unhexlify('%010x' % acc
)
232 last
= '' # No characters
242 raise TypeError('Incorrect padding')
244 return EMPTYSTRING
.join(parts
)
248 # RFC 3548, Base 16 Alphabet specifies uppercase, but hexlify() returns
249 # lowercase. The RFC also recommends against accepting input case
252 """Encode a string using Base16.
254 s is the string to encode. The encoded string is returned.
256 return binascii
.hexlify(s
).upper()
259 def b16decode(s
, casefold
=False):
260 """Decode a Base16 encoded string.
262 s is the string to decode. Optional casefold is a flag specifying whether
263 a lowercase alphabet is acceptable as input. For security purposes, the
266 The decoded string is returned. A TypeError is raised if s were
267 incorrectly padded or if there are non-alphabet characters present in the
272 if re
.search('[^0-9A-F]', s
):
273 raise TypeError('Non-base16 digit found')
274 return binascii
.unhexlify(s
)
278 # Legacy interface. This code could be cleaned up since I don't believe
279 # binascii has any line length limitations. It just doesn't seem worth it
282 MAXLINESIZE
= 76 # Excluding the CRLF
283 MAXBINSIZE
= (MAXLINESIZE
//4)*3
285 def encode(input, output
):
288 s
= input.read(MAXBINSIZE
)
291 while len(s
) < MAXBINSIZE
:
292 ns
= input.read(MAXBINSIZE
-len(s
))
296 line
= binascii
.b2a_base64(s
)
300 def decode(input, output
):
303 line
= input.readline()
306 s
= binascii
.a2b_base64(line
)
311 """Encode a string into multiple lines of base-64 data."""
313 for i
in range(0, len(s
), MAXBINSIZE
):
314 chunk
= s
[i
: i
+ MAXBINSIZE
]
315 pieces
.append(binascii
.b2a_base64(chunk
))
316 return "".join(pieces
)
320 """Decode a string."""
321 return binascii
.a2b_base64(s
)
325 # Useable as a script...
327 """Small test program"""
330 opts
, args
= getopt
.getopt(sys
.argv
[1:], 'deut')
331 except getopt
.error
, msg
:
332 sys
.stdout
= sys
.stderr
334 print """usage: %s [-d|-e|-u|-t] [file|-]
337 -t: encode and decode string 'Aladdin:open sesame'"""%sys
.argv
[0]
341 if o
== '-e': func
= encode
342 if o
== '-d': func
= decode
343 if o
== '-u': func
= decode
344 if o
== '-t': test1(); return
345 if args
and args
[0] != '-':
346 func(open(args
[0], 'rb'), sys
.stdout
)
348 func(sys
.stdin
, sys
.stdout
)
352 s0
= "Aladdin:open sesame"
353 s1
= encodestring(s0
)
354 s2
= decodestring(s1
)
355 print s0
, repr(s1
), s2
358 if __name__
== '__main__':