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387 lines
12 KiB
Python
Executable file
387 lines
12 KiB
Python
Executable file
#! /usr/bin/env python
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"""RFC 3548: Base16, Base32, Base64 Data Encodings"""
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# Modified 04-Oct-1995 by Jack Jansen to use binascii module
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# Modified 30-Dec-2003 by Barry Warsaw to add full RFC 3548 support
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# Modified 22-May-2007 by Guido van Rossum to use bytes everywhere
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import re
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import struct
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import binascii
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__all__ = [
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# Legacy interface exports traditional RFC 1521 Base64 encodings
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'encode', 'decode', 'encodestring', 'decodestring',
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# Generalized interface for other encodings
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'b64encode', 'b64decode', 'b32encode', 'b32decode',
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'b16encode', 'b16decode',
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# Standard Base64 encoding
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'standard_b64encode', 'standard_b64decode',
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# Some common Base64 alternatives. As referenced by RFC 3458, see thread
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# starting at:
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#
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# http://zgp.org/pipermail/p2p-hackers/2001-September/000316.html
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'urlsafe_b64encode', 'urlsafe_b64decode',
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]
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def _translate(s, altchars):
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if not isinstance(s, bytes):
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raise TypeError("expected bytes, not %s" % s.__class__.__name__)
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translation = bytes(range(256))
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for k, v in altchars.items():
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translation[ord(k)] = v[0]
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return s.translate(translation)
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# Base64 encoding/decoding uses binascii
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def b64encode(s, altchars=None):
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"""Encode a byte string using Base64.
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s is the byte string to encode. Optional altchars must be a byte
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string of length 2 which specifies an alternative alphabet for the
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'+' and '/' characters. This allows an application to
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e.g. generate url or filesystem safe Base64 strings.
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The encoded byte string is returned.
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"""
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if not isinstance(s, bytes):
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s = bytes(s, "ascii")
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# Strip off the trailing newline
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encoded = binascii.b2a_base64(s)[:-1]
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if altchars is not None:
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if not isinstance(altchars, bytes):
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altchars = bytes(altchars, "ascii")
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assert len(altchars) == 2, repr(altchars)
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return _translate(encoded, {'+': altchars[0:1], '/': altchars[1:2]})
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return encoded
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def b64decode(s, altchars=None):
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"""Decode a Base64 encoded byte string.
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s is the byte string to decode. Optional altchars must be a
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string of length 2 which specifies the alternative alphabet used
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instead of the '+' and '/' characters.
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The decoded byte string is returned. binascii.Error is raised if
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s were incorrectly padded or if there are non-alphabet characters
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present in the string.
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"""
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if not isinstance(s, bytes):
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s = bytes(s)
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if altchars is not None:
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if not isinstance(altchars, bytes):
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altchars = bytes(altchars, "ascii")
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assert len(altchars) == 2, repr(altchars)
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s = _translate(s, {chr(altchars[0]): b'+', chr(altchars[1]): b'/'})
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return binascii.a2b_base64(s)
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def standard_b64encode(s):
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"""Encode a byte string using the standard Base64 alphabet.
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s is the byte string to encode. The encoded byte string is returned.
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"""
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return b64encode(s)
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def standard_b64decode(s):
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"""Decode a byte string encoded with the standard Base64 alphabet.
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s is the byte string to decode. The decoded byte string is
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returned. binascii.Error is raised if the input is incorrectly
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padded or if there are non-alphabet characters present in the
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input.
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"""
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return b64decode(s)
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def urlsafe_b64encode(s):
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"""Encode a byte string using a url-safe Base64 alphabet.
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s is the byte string to encode. The encoded byte string is
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returned. The alphabet uses '-' instead of '+' and '_' instead of
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'/'.
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"""
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return b64encode(s, b'-_')
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def urlsafe_b64decode(s):
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"""Decode a byte string encoded with the standard Base64 alphabet.
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s is the byte string to decode. The decoded byte string is
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returned. binascii.Error is raised if the input is incorrectly
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padded or if there are non-alphabet characters present in the
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input.
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The alphabet uses '-' instead of '+' and '_' instead of '/'.
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"""
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return b64decode(s, b'-_')
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# Base32 encoding/decoding must be done in Python
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_b32alphabet = {
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0: b'A', 9: b'J', 18: b'S', 27: b'3',
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1: b'B', 10: b'K', 19: b'T', 28: b'4',
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2: b'C', 11: b'L', 20: b'U', 29: b'5',
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3: b'D', 12: b'M', 21: b'V', 30: b'6',
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4: b'E', 13: b'N', 22: b'W', 31: b'7',
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5: b'F', 14: b'O', 23: b'X',
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6: b'G', 15: b'P', 24: b'Y',
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7: b'H', 16: b'Q', 25: b'Z',
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8: b'I', 17: b'R', 26: b'2',
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}
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_b32tab = [v[0] for k, v in sorted(_b32alphabet.items())]
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_b32rev = dict([(v[0], k) for k, v in _b32alphabet.items()])
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def b32encode(s):
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"""Encode a byte string using Base32.
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s is the byte string to encode. The encoded byte string is returned.
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"""
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if not isinstance(s, bytes):
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s = bytes(s)
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quanta, leftover = divmod(len(s), 5)
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# Pad the last quantum with zero bits if necessary
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if leftover:
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s = s + bytes(5 - leftover) # Don't use += !
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quanta += 1
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encoded = bytes()
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for i in range(quanta):
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# c1 and c2 are 16 bits wide, c3 is 8 bits wide. The intent of this
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# code is to process the 40 bits in units of 5 bits. So we take the 1
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# leftover bit of c1 and tack it onto c2. Then we take the 2 leftover
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# bits of c2 and tack them onto c3. The shifts and masks are intended
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# to give us values of exactly 5 bits in width.
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c1, c2, c3 = struct.unpack('!HHB', s[i*5:(i+1)*5])
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c2 += (c1 & 1) << 16 # 17 bits wide
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c3 += (c2 & 3) << 8 # 10 bits wide
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encoded += bytes([_b32tab[c1 >> 11], # bits 1 - 5
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_b32tab[(c1 >> 6) & 0x1f], # bits 6 - 10
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_b32tab[(c1 >> 1) & 0x1f], # bits 11 - 15
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_b32tab[c2 >> 12], # bits 16 - 20 (1 - 5)
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_b32tab[(c2 >> 7) & 0x1f], # bits 21 - 25 (6 - 10)
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_b32tab[(c2 >> 2) & 0x1f], # bits 26 - 30 (11 - 15)
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_b32tab[c3 >> 5], # bits 31 - 35 (1 - 5)
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_b32tab[c3 & 0x1f], # bits 36 - 40 (1 - 5)
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])
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# Adjust for any leftover partial quanta
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if leftover == 1:
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return encoded[:-6] + b'======'
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elif leftover == 2:
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return encoded[:-4] + b'===='
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elif leftover == 3:
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return encoded[:-3] + b'==='
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elif leftover == 4:
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return encoded[:-1] + b'='
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return encoded
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def b32decode(s, casefold=False, map01=None):
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"""Decode a Base32 encoded byte string.
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s is the byte string to decode. Optional casefold is a flag
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specifying whether a lowercase alphabet is acceptable as input.
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For security purposes, the default is False.
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RFC 3548 allows for optional mapping of the digit 0 (zero) to the
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letter O (oh), and for optional mapping of the digit 1 (one) to
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either the letter I (eye) or letter L (el). The optional argument
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map01 when not None, specifies which letter the digit 1 should be
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mapped to (when map01 is not None, the digit 0 is always mapped to
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the letter O). For security purposes the default is None, so that
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0 and 1 are not allowed in the input.
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The decoded byte string is returned. binascii.Error is raised if
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the input is incorrectly padded or if there are non-alphabet
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characters present in the input.
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"""
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if not isinstance(s, bytes):
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s = bytes(s)
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quanta, leftover = divmod(len(s), 8)
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if leftover:
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raise binascii.Error('Incorrect padding')
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# Handle section 2.4 zero and one mapping. The flag map01 will be either
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# False, or the character to map the digit 1 (one) to. It should be
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# either L (el) or I (eye).
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if map01:
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if not isinstance(map01, bytes):
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map01 = bytes(map01)
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assert len(map01) == 1, repr(map01)
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s = _translate(s, {'0': b'O', '1': map01})
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if casefold:
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s = bytes(str(s, "ascii").upper(), "ascii")
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# Strip off pad characters from the right. We need to count the pad
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# characters because this will tell us how many null bytes to remove from
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# the end of the decoded string.
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padchars = 0
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mo = re.search('(?P<pad>[=]*)$', s)
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if mo:
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padchars = len(mo.group('pad'))
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if padchars > 0:
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s = s[:-padchars]
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# Now decode the full quanta
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parts = []
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acc = 0
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shift = 35
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for c in s:
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val = _b32rev.get(c)
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if val is None:
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raise TypeError('Non-base32 digit found')
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acc += _b32rev[c] << shift
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shift -= 5
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if shift < 0:
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parts.append(binascii.unhexlify('%010x' % acc))
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acc = 0
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shift = 35
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# Process the last, partial quanta
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last = binascii.unhexlify(bytes('%010x' % acc, "ascii"))
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if padchars == 0:
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last = b'' # No characters
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elif padchars == 1:
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last = last[:-1]
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elif padchars == 3:
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last = last[:-2]
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elif padchars == 4:
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last = last[:-3]
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elif padchars == 6:
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last = last[:-4]
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else:
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raise binascii.Error('Incorrect padding')
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parts.append(last)
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return b''.join(parts)
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# RFC 3548, Base 16 Alphabet specifies uppercase, but hexlify() returns
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# lowercase. The RFC also recommends against accepting input case
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# insensitively.
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def b16encode(s):
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"""Encode a byte string using Base16.
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s is the byte string to encode. The encoded byte string is returned.
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"""
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return bytes(str(binascii.hexlify(s), "ascii").upper(), "ascii")
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def b16decode(s, casefold=False):
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"""Decode a Base16 encoded byte string.
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s is the byte string to decode. Optional casefold is a flag
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specifying whether a lowercase alphabet is acceptable as input.
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For security purposes, the default is False.
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The decoded byte string is returned. binascii.Error is raised if
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s were incorrectly padded or if there are non-alphabet characters
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present in the string.
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"""
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if not isinstance(s, bytes):
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s = bytes(s)
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if casefold:
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s = bytes(str(s, "ascii").upper(), "ascii")
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if re.search('[^0-9A-F]', s):
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raise binascii.Error('Non-base16 digit found')
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return binascii.unhexlify(s)
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# Legacy interface. This code could be cleaned up since I don't believe
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# binascii has any line length limitations. It just doesn't seem worth it
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# though. The files should be opened in binary mode.
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MAXLINESIZE = 76 # Excluding the CRLF
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MAXBINSIZE = (MAXLINESIZE//4)*3
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def encode(input, output):
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"""Encode a file; input and output are binary files."""
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while True:
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s = input.read(MAXBINSIZE)
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if not s:
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break
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while len(s) < MAXBINSIZE:
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ns = input.read(MAXBINSIZE-len(s))
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if not ns:
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break
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s += ns
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line = binascii.b2a_base64(s)
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output.write(line)
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def decode(input, output):
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"""Decode a file; input and output are binary files."""
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while True:
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line = input.readline()
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if not line:
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break
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s = binascii.a2b_base64(line)
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output.write(s)
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def encodestring(s):
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"""Encode a string into multiple lines of base-64 data.
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Argument and return value are bytes.
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"""
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if not isinstance(s, bytes):
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raise TypeError("expected bytes, not %s" % s.__class__.__name__)
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pieces = []
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for i in range(0, len(s), MAXBINSIZE):
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chunk = s[i : i + MAXBINSIZE]
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pieces.append(binascii.b2a_base64(chunk))
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return b"".join(pieces)
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def decodestring(s):
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"""Decode a string.
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Argument and return value are bytes.
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"""
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if not isinstance(s, bytes):
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raise TypeError("expected bytes, not %s" % s.__class__.__name__)
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return binascii.a2b_base64(s)
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# Usable as a script...
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def main():
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"""Small main program"""
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import sys, getopt
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try:
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opts, args = getopt.getopt(sys.argv[1:], 'deut')
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except getopt.error as msg:
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sys.stdout = sys.stderr
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print(msg)
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print("""usage: %s [-d|-e|-u|-t] [file|-]
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-d, -u: decode
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-e: encode (default)
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-t: encode and decode string 'Aladdin:open sesame'"""%sys.argv[0])
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sys.exit(2)
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func = encode
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for o, a in opts:
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if o == '-e': func = encode
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if o == '-d': func = decode
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if o == '-u': func = decode
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if o == '-t': test(); return
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if args and args[0] != '-':
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func(open(args[0], 'rb'), sys.stdout)
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else:
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func(sys.stdin, sys.stdout)
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def test():
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s0 = b"Aladdin:open sesame"
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print(repr(s0))
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s1 = encodestring(s0)
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print(repr(s1))
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s2 = decodestring(s1)
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print(repr(s2))
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assert s0 == s2
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if __name__ == '__main__':
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main()
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