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920dae64 AT |
1 | #! /usr/bin/env python |
2 | ||
3 | """RFC 3548: Base16, Base32, Base64 Data Encodings""" | |
4 | ||
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 | |
7 | ||
8 | import re | |
9 | import struct | |
10 | import binascii | |
11 | ||
12 | ||
13 | __all__ = [ | |
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 | |
22 | # starting at: | |
23 | # | |
24 | # http://zgp.org/pipermail/p2p-hackers/2001-September/000316.html | |
25 | 'urlsafe_b64encode', 'urlsafe_b64decode', | |
26 | ] | |
27 | ||
28 | _translation = [chr(_x) for _x in range(256)] | |
29 | EMPTYSTRING = '' | |
30 | ||
31 | ||
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)) | |
37 | ||
38 | ||
39 | \f | |
40 | # Base64 encoding/decoding uses binascii | |
41 | ||
42 | def b64encode(s, altchars=None): | |
43 | """Encode a string using Base64. | |
44 | ||
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. | |
49 | ||
50 | The encoded string is returned. | |
51 | """ | |
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]}) | |
56 | return encoded | |
57 | ||
58 | ||
59 | def b64decode(s, altchars=None): | |
60 | """Decode a Base64 encoded string. | |
61 | ||
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. | |
65 | ||
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 | |
68 | string. | |
69 | """ | |
70 | if altchars is not None: | |
71 | s = _translate(s, {altchars[0]: '+', altchars[1]: '/'}) | |
72 | try: | |
73 | return binascii.a2b_base64(s) | |
74 | except binascii.Error, msg: | |
75 | # Transform this exception for consistency | |
76 | raise TypeError(msg) | |
77 | ||
78 | ||
79 | def standard_b64encode(s): | |
80 | """Encode a string using the standard Base64 alphabet. | |
81 | ||
82 | s is the string to encode. The encoded string is returned. | |
83 | """ | |
84 | return b64encode(s) | |
85 | ||
86 | def standard_b64decode(s): | |
87 | """Decode a string encoded with the standard Base64 alphabet. | |
88 | ||
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. | |
92 | """ | |
93 | return b64decode(s) | |
94 | ||
95 | def urlsafe_b64encode(s): | |
96 | """Encode a string using a url-safe Base64 alphabet. | |
97 | ||
98 | s is the string to encode. The encoded string is returned. The alphabet | |
99 | uses '-' instead of '+' and '_' instead of '/'. | |
100 | """ | |
101 | return b64encode(s, '-_') | |
102 | ||
103 | def urlsafe_b64decode(s): | |
104 | """Decode a string encoded with the standard Base64 alphabet. | |
105 | ||
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. | |
109 | ||
110 | The alphabet uses '-' instead of '+' and '_' instead of '/'. | |
111 | """ | |
112 | return b64decode(s, '-_') | |
113 | ||
114 | ||
115 | \f | |
116 | # Base32 encoding/decoding must be done in Python | |
117 | _b32alphabet = { | |
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', | |
127 | } | |
128 | ||
129 | _b32tab = [v for v in _b32alphabet.values()] | |
130 | _b32rev = dict([(v, long(k)) for k, v in _b32alphabet.items()]) | |
131 | ||
132 | ||
133 | def b32encode(s): | |
134 | """Encode a string using Base32. | |
135 | ||
136 | s is the string to encode. The encoded string is returned. | |
137 | """ | |
138 | parts = [] | |
139 | quanta, leftover = divmod(len(s), 5) | |
140 | # Pad the last quantum with zero bits if necessary | |
141 | if leftover: | |
142 | s += ('\0' * (5 - leftover)) | |
143 | quanta += 1 | |
144 | for i in range(quanta): | |
145 | # c1 and c2 are 16 bits wide, c3 is 8 bits wide. The intent of this | |
146 | # code is to process the 40 bits in units of 5 bits. So we take the 1 | |
147 | # leftover bit of c1 and tack it onto c2. Then we take the 2 leftover | |
148 | # bits of c2 and tack them onto c3. The shifts and masks are intended | |
149 | # to give us values of exactly 5 bits in width. | |
150 | c1, c2, c3 = struct.unpack('!HHB', s[i*5:(i+1)*5]) | |
151 | c2 += (c1 & 1) << 16 # 17 bits wide | |
152 | c3 += (c2 & 3) << 8 # 10 bits wide | |
153 | parts.extend([_b32tab[c1 >> 11], # bits 1 - 5 | |
154 | _b32tab[(c1 >> 6) & 0x1f], # bits 6 - 10 | |
155 | _b32tab[(c1 >> 1) & 0x1f], # bits 11 - 15 | |
156 | _b32tab[c2 >> 12], # bits 16 - 20 (1 - 5) | |
157 | _b32tab[(c2 >> 7) & 0x1f], # bits 21 - 25 (6 - 10) | |
158 | _b32tab[(c2 >> 2) & 0x1f], # bits 26 - 30 (11 - 15) | |
159 | _b32tab[c3 >> 5], # bits 31 - 35 (1 - 5) | |
160 | _b32tab[c3 & 0x1f], # bits 36 - 40 (1 - 5) | |
161 | ]) | |
162 | encoded = EMPTYSTRING.join(parts) | |
163 | # Adjust for any leftover partial quanta | |
164 | if leftover == 1: | |
165 | return encoded[:-6] + '======' | |
166 | elif leftover == 2: | |
167 | return encoded[:-4] + '====' | |
168 | elif leftover == 3: | |
169 | return encoded[:-3] + '===' | |
170 | elif leftover == 4: | |
171 | return encoded[:-1] + '=' | |
172 | return encoded | |
173 | ||
174 | ||
175 | def b32decode(s, casefold=False, map01=None): | |
176 | """Decode a Base32 encoded string. | |
177 | ||
178 | s is the string to decode. Optional casefold is a flag specifying whether | |
179 | a lowercase alphabet is acceptable as input. For security purposes, the | |
180 | default is False. | |
181 | ||
182 | RFC 3548 allows for optional mapping of the digit 0 (zero) to the letter O | |
183 | (oh), and for optional mapping of the digit 1 (one) to either the letter I | |
184 | (eye) or letter L (el). The optional argument map01 when not None, | |
185 | specifies which letter the digit 1 should be mapped to (when map01 is not | |
186 | None, the digit 0 is always mapped to the letter O). For security | |
187 | purposes the default is None, so that 0 and 1 are not allowed in the | |
188 | input. | |
189 | ||
190 | The decoded string is returned. A TypeError is raised if s were | |
191 | incorrectly padded or if there are non-alphabet characters present in the | |
192 | string. | |
193 | """ | |
194 | quanta, leftover = divmod(len(s), 8) | |
195 | if leftover: | |
196 | raise TypeError('Incorrect padding') | |
197 | # Handle section 2.4 zero and one mapping. The flag map01 will be either | |
198 | # False, or the character to map the digit 1 (one) to. It should be | |
199 | # either L (el) or I (eye). | |
200 | if map01: | |
201 | s = _translate(s, {'0': 'O', '1': map01}) | |
202 | if casefold: | |
203 | s = s.upper() | |
204 | # Strip off pad characters from the right. We need to count the pad | |
205 | # characters because this will tell us how many null bytes to remove from | |
206 | # the end of the decoded string. | |
207 | padchars = 0 | |
208 | mo = re.search('(?P<pad>[=]*)$', s) | |
209 | if mo: | |
210 | padchars = len(mo.group('pad')) | |
211 | if padchars > 0: | |
212 | s = s[:-padchars] | |
213 | # Now decode the full quanta | |
214 | parts = [] | |
215 | acc = 0 | |
216 | shift = 35 | |
217 | for c in s: | |
218 | val = _b32rev.get(c) | |
219 | if val is None: | |
220 | raise TypeError('Non-base32 digit found') | |
221 | acc += _b32rev[c] << shift | |
222 | shift -= 5 | |
223 | if shift < 0: | |
224 | parts.append(binascii.unhexlify('%010x' % acc)) | |
225 | acc = 0 | |
226 | shift = 35 | |
227 | # Process the last, partial quanta | |
228 | last = binascii.unhexlify('%010x' % acc) | |
229 | if padchars == 0: | |
230 | last = '' # No characters | |
231 | elif padchars == 1: | |
232 | last = last[:-1] | |
233 | elif padchars == 3: | |
234 | last = last[:-2] | |
235 | elif padchars == 4: | |
236 | last = last[:-3] | |
237 | elif padchars == 6: | |
238 | last = last[:-4] | |
239 | else: | |
240 | raise TypeError('Incorrect padding') | |
241 | parts.append(last) | |
242 | return EMPTYSTRING.join(parts) | |
243 | ||
244 | ||
245 | \f | |
246 | # RFC 3548, Base 16 Alphabet specifies uppercase, but hexlify() returns | |
247 | # lowercase. The RFC also recommends against accepting input case | |
248 | # insensitively. | |
249 | def b16encode(s): | |
250 | """Encode a string using Base16. | |
251 | ||
252 | s is the string to encode. The encoded string is returned. | |
253 | """ | |
254 | return binascii.hexlify(s).upper() | |
255 | ||
256 | ||
257 | def b16decode(s, casefold=False): | |
258 | """Decode a Base16 encoded string. | |
259 | ||
260 | s is the string to decode. Optional casefold is a flag specifying whether | |
261 | a lowercase alphabet is acceptable as input. For security purposes, the | |
262 | default is False. | |
263 | ||
264 | The decoded string is returned. A TypeError is raised if s were | |
265 | incorrectly padded or if there are non-alphabet characters present in the | |
266 | string. | |
267 | """ | |
268 | if casefold: | |
269 | s = s.upper() | |
270 | if re.search('[^0-9A-F]', s): | |
271 | raise TypeError('Non-base16 digit found') | |
272 | return binascii.unhexlify(s) | |
273 | ||
274 | ||
275 | \f | |
276 | # Legacy interface. This code could be cleaned up since I don't believe | |
277 | # binascii has any line length limitations. It just doesn't seem worth it | |
278 | # though. | |
279 | ||
280 | MAXLINESIZE = 76 # Excluding the CRLF | |
281 | MAXBINSIZE = (MAXLINESIZE//4)*3 | |
282 | ||
283 | def encode(input, output): | |
284 | """Encode a file.""" | |
285 | while True: | |
286 | s = input.read(MAXBINSIZE) | |
287 | if not s: | |
288 | break | |
289 | while len(s) < MAXBINSIZE: | |
290 | ns = input.read(MAXBINSIZE-len(s)) | |
291 | if not ns: | |
292 | break | |
293 | s += ns | |
294 | line = binascii.b2a_base64(s) | |
295 | output.write(line) | |
296 | ||
297 | ||
298 | def decode(input, output): | |
299 | """Decode a file.""" | |
300 | while True: | |
301 | line = input.readline() | |
302 | if not line: | |
303 | break | |
304 | s = binascii.a2b_base64(line) | |
305 | output.write(s) | |
306 | ||
307 | ||
308 | def encodestring(s): | |
309 | """Encode a string.""" | |
310 | pieces = [] | |
311 | for i in range(0, len(s), MAXBINSIZE): | |
312 | chunk = s[i : i + MAXBINSIZE] | |
313 | pieces.append(binascii.b2a_base64(chunk)) | |
314 | return "".join(pieces) | |
315 | ||
316 | ||
317 | def decodestring(s): | |
318 | """Decode a string.""" | |
319 | return binascii.a2b_base64(s) | |
320 | ||
321 | ||
322 | \f | |
323 | # Useable as a script... | |
324 | def test(): | |
325 | """Small test program""" | |
326 | import sys, getopt | |
327 | try: | |
328 | opts, args = getopt.getopt(sys.argv[1:], 'deut') | |
329 | except getopt.error, msg: | |
330 | sys.stdout = sys.stderr | |
331 | print msg | |
332 | print """usage: %s [-d|-e|-u|-t] [file|-] | |
333 | -d, -u: decode | |
334 | -e: encode (default) | |
335 | -t: encode and decode string 'Aladdin:open sesame'"""%sys.argv[0] | |
336 | sys.exit(2) | |
337 | func = encode | |
338 | for o, a in opts: | |
339 | if o == '-e': func = encode | |
340 | if o == '-d': func = decode | |
341 | if o == '-u': func = decode | |
342 | if o == '-t': test1(); return | |
343 | if args and args[0] != '-': | |
344 | func(open(args[0], 'rb'), sys.stdout) | |
345 | else: | |
346 | func(sys.stdin, sys.stdout) | |
347 | ||
348 | ||
349 | def test1(): | |
350 | s0 = "Aladdin:open sesame" | |
351 | s1 = encodestring(s0) | |
352 | s2 = decodestring(s1) | |
353 | print s0, repr(s1), s2 | |
354 | ||
355 | ||
356 | if __name__ == '__main__': | |
357 | test() |