390 lines
12 KiB
Python
Executable File
390 lines
12 KiB
Python
Executable File
#! /usr/bin/env python3
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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', 'encodebytes', 'decodebytes',
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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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bytes_types = (bytes, bytearray) # Types acceptable as binary data
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def _bytes_from_decode_data(s):
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if isinstance(s, str):
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try:
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return s.encode('ascii')
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except UnicodeEncodeError:
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raise ValueError('string argument should contain only ASCII characters')
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if isinstance(s, bytes_types):
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return s
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try:
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return memoryview(s).tobytes()
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except TypeError:
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raise TypeError("argument should be a bytes-like object or ASCII "
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"string, not %r" % s.__class__.__name__) from None
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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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# 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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assert len(altchars) == 2, repr(altchars)
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return encoded.translate(bytes.maketrans(b'+/', altchars))
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return encoded
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def b64decode(s, altchars=None, validate=False):
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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 string is returned. A binascii.Error is raised if s is
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incorrectly padded.
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If validate is False (the default), non-base64-alphabet characters are
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discarded prior to the padding check. If validate is True,
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non-base64-alphabet characters in the input result in a binascii.Error.
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"""
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s = _bytes_from_decode_data(s)
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if altchars is not None:
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altchars = _bytes_from_decode_data(altchars)
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assert len(altchars) == 2, repr(altchars)
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s = s.translate(bytes.maketrans(altchars, b'+/'))
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if validate and not re.match(b'^[A-Za-z0-9+/]*={0,2}$', s):
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raise binascii.Error('Non-base64 digit found')
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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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_urlsafe_encode_translation = bytes.maketrans(b'+/', b'-_')
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_urlsafe_decode_translation = bytes.maketrans(b'-_', b'+/')
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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).translate(_urlsafe_encode_translation)
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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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s = _bytes_from_decode_data(s)
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s = s.translate(_urlsafe_decode_translation)
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return b64decode(s)
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# Base32 encoding/decoding must be done in Python
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_b32alphabet = b'ABCDEFGHIJKLMNOPQRSTUVWXYZ234567'
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_b32tab = [bytes([i]) for i in _b32alphabet]
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_b32tab2 = [a + b for a in _b32tab for b in _b32tab]
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_b32rev = {v: k for k, v in enumerate(_b32alphabet)}
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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_types):
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s = memoryview(s).tobytes()
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leftover = 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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encoded = bytearray()
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from_bytes = int.from_bytes
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b32tab2 = _b32tab2
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for i in range(0, len(s), 5):
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c = from_bytes(s[i: i + 5], 'big')
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encoded += (b32tab2[c >> 30] + # bits 1 - 10
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b32tab2[(c >> 20) & 0x3ff] + # bits 11 - 20
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b32tab2[(c >> 10) & 0x3ff] + # bits 21 - 30
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b32tab2[c & 0x3ff] # bits 31 - 40
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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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encoded[-6:] = b'======'
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elif leftover == 2:
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encoded[-4:] = b'===='
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elif leftover == 3:
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encoded[-3:] = b'==='
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elif leftover == 4:
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encoded[-1:] = b'='
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return bytes(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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s = _bytes_from_decode_data(s)
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if len(s) % 8:
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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 is not None:
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map01 = _bytes_from_decode_data(map01)
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assert len(map01) == 1, repr(map01)
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s = s.translate(bytes.maketrans(b'01', b'O' + map01))
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if casefold:
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s = s.upper()
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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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l = len(s)
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s = s.rstrip(b'=')
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padchars = l - len(s)
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# Now decode the full quanta
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decoded = bytearray()
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b32rev = _b32rev
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for i in range(0, len(s), 8):
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quanta = s[i: i + 8]
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acc = 0
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try:
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for c in quanta:
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acc = (acc << 5) + b32rev[c]
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except KeyError:
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raise binascii.Error('Non-base32 digit found') from None
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decoded += acc.to_bytes(5, 'big')
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# Process the last, partial quanta
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if padchars:
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acc <<= 5 * padchars
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last = acc.to_bytes(5, 'big')
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if padchars == 1:
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decoded[-5:] = last[:-1]
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elif padchars == 3:
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decoded[-5:] = last[:-2]
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elif padchars == 4:
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decoded[-5:] = last[:-3]
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elif padchars == 6:
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decoded[-5:] = last[:-4]
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else:
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raise binascii.Error('Incorrect padding')
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return bytes(decoded)
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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 binascii.hexlify(s).upper()
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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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s = _bytes_from_decode_data(s)
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if casefold:
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s = s.upper()
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if re.search(b'[^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 _input_type_check(s):
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try:
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m = memoryview(s)
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except TypeError as err:
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msg = "expected bytes-like object, not %s" % s.__class__.__name__
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raise TypeError(msg) from err
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if m.format not in ('c', 'b', 'B'):
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msg = ("expected single byte elements, not %r from %s" %
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(m.format, s.__class__.__name__))
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raise TypeError(msg)
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if m.ndim != 1:
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msg = ("expected 1-D data, not %d-D data from %s" %
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(m.ndim, s.__class__.__name__))
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raise TypeError(msg)
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def encodebytes(s):
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"""Encode a bytestring into a bytestring containing multiple lines
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of base-64 data."""
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_input_type_check(s)
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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 encodestring(s):
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"""Legacy alias of encodebytes()."""
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import warnings
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warnings.warn("encodestring() is a deprecated alias, use encodebytes()",
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DeprecationWarning, 2)
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return encodebytes(s)
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def decodebytes(s):
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"""Decode a bytestring of base-64 data into a bytestring."""
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_input_type_check(s)
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return binascii.a2b_base64(s)
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def decodestring(s):
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"""Legacy alias of decodebytes()."""
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import warnings
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warnings.warn("decodestring() is a deprecated alias, use decodebytes()",
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DeprecationWarning, 2)
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return decodebytes(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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with open(args[0], 'rb') as f:
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func(f, sys.stdout.buffer)
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else:
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func(sys.stdin.buffer, sys.stdout.buffer)
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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 = encodebytes(s0)
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print(repr(s1))
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s2 = decodebytes(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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