cpython / Lib / base64.py

  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
#! /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
# Modified 22-May-2007 by Guido van Rossum to use bytes everywhere

import re
import struct
import binascii


__all__ = [
    # Legacy interface exports traditional RFC 1521 Base64 encodings
    'encode', 'decode', 'encodebytes', 'decodebytes',
    # 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',
    ]


bytes_types = (bytes, bytearray)  # Types acceptable as binary data


def _translate(s, altchars):
    if not isinstance(s, bytes_types):
        raise TypeError("expected bytes, not %s" % s.__class__.__name__)
    translation = bytearray(range(256))
    for k, v in altchars.items():
        translation[ord(k)] = v[0]
    return s.translate(translation)



# Base64 encoding/decoding uses binascii

def b64encode(s, altchars=None):
    """Encode a byte string using Base64.

    s is the byte string to encode.  Optional altchars must be a byte
    string of length 2 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 byte string is returned.
    """
    if not isinstance(s, bytes_types):
        raise TypeError("expected bytes, not %s" % s.__class__.__name__)
    # Strip off the trailing newline
    encoded = binascii.b2a_base64(s)[:-1]
    if altchars is not None:
        if not isinstance(altchars, bytes_types):
            raise TypeError("expected bytes, not %s"
                            % altchars.__class__.__name__)
        assert len(altchars) == 2, repr(altchars)
        return _translate(encoded, {'+': altchars[0:1], '/': altchars[1:2]})
    return encoded


def b64decode(s, altchars=None):
    """Decode a Base64 encoded byte string.

    s is the byte string to decode.  Optional altchars must be a
    string of length 2 which specifies the alternative alphabet used
    instead of the '+' and '/' characters.

    The decoded byte string is returned.  binascii.Error is raised if
    s were incorrectly padded or if there are non-alphabet characters
    present in the string.
    """
    if not isinstance(s, bytes_types):
        raise TypeError("expected bytes, not %s" % s.__class__.__name__)
    if altchars is not None:
        if not isinstance(altchars, bytes_types):
            raise TypeError("expected bytes, not %s"
                            % altchars.__class__.__name__)
        assert len(altchars) == 2, repr(altchars)
        s = _translate(s, {chr(altchars[0]): b'+', chr(altchars[1]): b'/'})
    return binascii.a2b_base64(s)


def standard_b64encode(s):
    """Encode a byte string using the standard Base64 alphabet.

    s is the byte string to encode.  The encoded byte string is returned.
    """
    return b64encode(s)

def standard_b64decode(s):
    """Decode a byte string encoded with the standard Base64 alphabet.

    s is the byte string to decode.  The decoded byte string is
    returned.  binascii.Error is raised if the input is incorrectly
    padded or if there are non-alphabet characters present in the
    input.
    """
    return b64decode(s)

def urlsafe_b64encode(s):
    """Encode a byte string using a url-safe Base64 alphabet.

    s is the byte string to encode.  The encoded byte string is
    returned.  The alphabet uses '-' instead of '+' and '_' instead of
    '/'.
    """
    return b64encode(s, b'-_')

def urlsafe_b64decode(s):
    """Decode a byte string encoded with the standard Base64 alphabet.

    s is the byte string to decode.  The decoded byte string is
    returned.  binascii.Error is raised if the input is incorrectly
    padded or if there are non-alphabet characters present in the
    input.

    The alphabet uses '-' instead of '+' and '_' instead of '/'.
    """
    return b64decode(s, b'-_')



# Base32 encoding/decoding must be done in Python
_b32alphabet = {
    0: b'A',  9: b'J', 18: b'S', 27: b'3',
    1: b'B', 10: b'K', 19: b'T', 28: b'4',
    2: b'C', 11: b'L', 20: b'U', 29: b'5',
    3: b'D', 12: b'M', 21: b'V', 30: b'6',
    4: b'E', 13: b'N', 22: b'W', 31: b'7',
    5: b'F', 14: b'O', 23: b'X',
    6: b'G', 15: b'P', 24: b'Y',
    7: b'H', 16: b'Q', 25: b'Z',
    8: b'I', 17: b'R', 26: b'2',
    }

_b32tab = [v[0] for k, v in sorted(_b32alphabet.items())]
_b32rev = dict([(v[0], k) for k, v in _b32alphabet.items()])


def b32encode(s):
    """Encode a byte string using Base32.

    s is the byte string to encode.  The encoded byte string is returned.
    """
    if not isinstance(s, bytes_types):
        raise TypeError("expected bytes, not %s" % s.__class__.__name__)
    quanta, leftover = divmod(len(s), 5)
    # Pad the last quantum with zero bits if necessary
    if leftover:
        s = s + bytes(5 - leftover)  # Don't use += !
        quanta += 1
    encoded = bytes()
    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
        encoded += bytes([_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)
                          ])
    # Adjust for any leftover partial quanta
    if leftover == 1:
        return encoded[:-6] + b'======'
    elif leftover == 2:
        return encoded[:-4] + b'===='
    elif leftover == 3:
        return encoded[:-3] + b'==='
    elif leftover == 4:
        return encoded[:-1] + b'='
    return encoded


def b32decode(s, casefold=False, map01=None):
    """Decode a Base32 encoded byte string.

    s is the byte 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 byte string is returned.  binascii.Error is raised if
    the input is incorrectly padded or if there are non-alphabet
    characters present in the input.
    """
    if not isinstance(s, bytes_types):
        raise TypeError("expected bytes, not %s" % s.__class__.__name__)
    quanta, leftover = divmod(len(s), 8)
    if leftover:
        raise binascii.Error('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 is not None:
        if not isinstance(map01, bytes_types):
            raise TypeError("expected bytes, not %s" % map01.__class__.__name__)
        assert len(map01) == 1, repr(map01)
        s = _translate(s, {b'0': b'O', b'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(b'(?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(bytes('%010x' % acc, "ascii"))
    if padchars == 0:
        last = b''                      # 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 binascii.Error('Incorrect padding')
    parts.append(last)
    return b''.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 byte string using Base16.

    s is the byte string to encode.  The encoded byte string is returned.
    """
    if not isinstance(s, bytes_types):
        raise TypeError("expected bytes, not %s" % s.__class__.__name__)
    return binascii.hexlify(s).upper()


def b16decode(s, casefold=False):
    """Decode a Base16 encoded byte string.

    s is the byte 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 byte string is returned.  binascii.Error is raised if
    s were incorrectly padded or if there are non-alphabet characters
    present in the string.
    """
    if not isinstance(s, bytes_types):
        raise TypeError("expected bytes, not %s" % s.__class__.__name__)
    if casefold:
        s = s.upper()
    if re.search(b'[^0-9A-F]', s):
        raise binascii.Error('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.  The files should be opened in binary mode.

MAXLINESIZE = 76 # Excluding the CRLF
MAXBINSIZE = (MAXLINESIZE//4)*3

def encode(input, output):
    """Encode a file; input and output are binary files."""
    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; input and output are binary files."""
    while True:
        line = input.readline()
        if not line:
            break
        s = binascii.a2b_base64(line)
        output.write(s)


def encodebytes(s):
    """Encode a bytestring into a bytestring containing multiple lines
    of base-64 data."""
    if not isinstance(s, bytes_types):
        raise TypeError("expected bytes, not %s" % s.__class__.__name__)
    pieces = []
    for i in range(0, len(s), MAXBINSIZE):
        chunk = s[i : i + MAXBINSIZE]
        pieces.append(binascii.b2a_base64(chunk))
    return b"".join(pieces)

def encodestring(s):
    """Legacy alias of encodebytes()."""
    import warnings
    warnings.warn("encodestring() is a deprecated alias, use encodebytes()",
                  DeprecationWarning, 2)
    return encodebytes(s)


def decodebytes(s):
    """Decode a bytestring of base-64 data into a bytestring."""
    if not isinstance(s, bytes_types):
        raise TypeError("expected bytes, not %s" % s.__class__.__name__)
    return binascii.a2b_base64(s)

def decodestring(s):
    """Legacy alias of decodebytes()."""
    import warnings
    warnings.warn("decodestring() is a deprecated alias, use decodebytes()",
                  DeprecationWarning, 2)
    return decodebytes(s)


# Usable as a script...
def main():
    """Small main program"""
    import sys, getopt
    try:
        opts, args = getopt.getopt(sys.argv[1:], 'deut')
    except getopt.error as 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': test(); return
    if args and args[0] != '-':
        with open(args[0], 'rb') as f:
            func(f, sys.stdout.buffer)
    else:
        func(sys.stdin.buffer, sys.stdout.buffer)


def test():
    s0 = b"Aladdin:open sesame"
    print(repr(s0))
    s1 = encodebytes(s0)
    print(repr(s1))
    s2 = decodebytes(s1)
    print(repr(s2))
    assert s0 == s2


if __name__ == '__main__':
    main()
Tip: Filter by directory path e.g. /media app.js to search for public/media/app.js.
Tip: Use camelCasing e.g. ProjME to search for ProjectModifiedEvent.java.
Tip: Filter by extension type e.g. /repo .js to search for all .js files in the /repo directory.
Tip: Separate your search with spaces e.g. /ssh pom.xml to search for src/ssh/pom.xml.
Tip: Use ↑ and ↓ arrow keys to navigate and return to view the file.
Tip: You can also navigate files with Ctrl+j (next) and Ctrl+k (previous) and view the file with Ctrl+o.
Tip: You can also navigate files with Alt+j (next) and Alt+k (previous) and view the file with Alt+o.