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bpo-16995: add support for base32 extended hex (base32hex) (GH-20441)

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Filipe Laíns 2020-08-10 15:48:20 +01:00 committed by GitHub
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5 changed files with 156 additions and 33 deletions
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23
Doc/library/base64.rst
View file

@ -124,7 +124,7 @@ The modern interface provides:
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
:rfc:`4648` 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
@ -136,6 +136,27 @@ The modern interface provides:
input.
.. function:: b32hexencode(s)
Similar to :func:`b32encode` but uses the Extended Hex Alphabet, as defined in
:rfc:`4648`.
.. versionadded:: 3.10
.. function:: b32hexdecode(s, casefold=False)
Similar to :func:`b32decode` but uses the Extended Hex Alphabet, as defined in
:rfc:`4648`.
This version does not allow the digit 0 (zero) to the letter O (oh) and digit
1 (one) to either the letter I (eye) or letter L (el) mappings, all these
characters are included in the Extended Hex Alphabet and are not
interchangable.
.. versionadded:: 3.10
.. function:: b16encode(s)
Encode the :term:`bytes-like object` *s* using Base16 and return the

6
Doc/whatsnew/3.10.rst
View file

@ -103,6 +103,12 @@ New Modules
Improved Modules
================
base64
------
Add :func:`base64.b32hexencode` and :func:`base64.b32hexdecode` to support the
Base32 Encoding with Extended Hex Alphabet.
curses
------

88
Lib/base64.py
View file

@ -16,7 +16,7 @@
'encode', 'decode', 'encodebytes', 'decodebytes',
# Generalized interface for other encodings
'b64encode', 'b64decode', 'b32encode', 'b32decode',
'b16encode', 'b16decode',
'b32hexencode', 'b32hexdecode', 'b16encode', 'b16decode',
# Base85 and Ascii85 encodings
'b85encode', 'b85decode', 'a85encode', 'a85decode',
# Standard Base64 encoding
@ -135,19 +135,40 @@ def urlsafe_b64decode(s):
# Base32 encoding/decoding must be done in Python
_b32alphabet = b'ABCDEFGHIJKLMNOPQRSTUVWXYZ234567'
_b32tab2 = None
_b32rev = None
_B32_ENCODE_DOCSTRING = '''
Encode the bytes-like objects using {encoding} and return a bytes object.
'''
_B32_DECODE_DOCSTRING = '''
Decode the {encoding} encoded bytes-like object or ASCII string s.
def b32encode(s):
"""Encode the bytes-like object s using Base32 and return a bytes object.
"""
Optional casefold is a flag specifying whether a lowercase alphabet is
acceptable as input. For security purposes, the default is False.
{extra_args}
The result is returned as a bytes object. A binascii.Error is raised if
the input is incorrectly padded or if there are non-alphabet
characters present in the input.
'''
_B32_DECODE_MAP01_DOCSTRING = '''
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.
'''
_b32alphabet = b'ABCDEFGHIJKLMNOPQRSTUVWXYZ234567'
_b32hexalphabet = b'0123456789ABCDEFGHIJKLMNOPQRSTUV'
_b32tab2 = {}
_b32rev = {}
def _b32encode(alphabet, s):
global _b32tab2
# Delay the initialization of the table to not waste memory
# if the function is never called
if _b32tab2 is None:
b32tab = [bytes((i,)) for i in _b32alphabet]
_b32tab2 = [a + b for a in b32tab for b in b32tab]
if alphabet not in _b32tab2:
b32tab = [bytes((i,)) for i in alphabet]
_b32tab2[alphabet] = [a + b for a in b32tab for b in b32tab]
b32tab = None
if not isinstance(s, bytes_types):
@ -158,7 +179,7 @@ def b32encode(s):
s = s + b'\0' * (5 - leftover) # Don't use += !
encoded = bytearray()
from_bytes = int.from_bytes
b32tab2 = _b32tab2
b32tab2 = _b32tab2[alphabet]
for i in range(0, len(s), 5):
c = from_bytes(s[i: i + 5], 'big')
encoded += (b32tab2[c >> 30] + # bits 1 - 10
@ -177,29 +198,12 @@ def b32encode(s):
encoded[-1:] = b'='
return bytes(encoded)
def b32decode(s, casefold=False, map01=None):
"""Decode the Base32 encoded bytes-like object or ASCII string s.
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 result is returned as a bytes object. A binascii.Error is raised if
the input is incorrectly padded or if there are non-alphabet
characters present in the input.
"""
def _b32decode(alphabet, s, casefold=False, map01=None):
global _b32rev
# Delay the initialization of the table to not waste memory
# if the function is never called
if _b32rev is None:
_b32rev = {v: k for k, v in enumerate(_b32alphabet)}
if alphabet not in _b32rev:
_b32rev[alphabet] = {v: k for k, v in enumerate(alphabet)}
s = _bytes_from_decode_data(s)
if len(s) % 8:
raise binascii.Error('Incorrect padding')
@ -220,7 +224,7 @@ def b32decode(s, casefold=False, map01=None):
padchars = l - len(s)
# Now decode the full quanta
decoded = bytearray()
b32rev = _b32rev
b32rev = _b32rev[alphabet]
for i in range(0, len(s), 8):
quanta = s[i: i + 8]
acc = 0
@ -241,6 +245,26 @@ def b32decode(s, casefold=False, map01=None):
return bytes(decoded)
def b32encode(s):
return _b32encode(_b32alphabet, s)
b32encode.__doc__ = _B32_ENCODE_DOCSTRING.format(encoding='base32')
def b32decode(s, casefold=False, map01=None):
return _b32decode(_b32alphabet, s, casefold, map01)
b32decode.__doc__ = _B32_DECODE_DOCSTRING.format(encoding='base32',
extra_args=_B32_DECODE_MAP01_DOCSTRING)
def b32hexencode(s):
return _b32encode(_b32hexalphabet, s)
b32hexencode.__doc__ = _B32_ENCODE_DOCSTRING.format(encoding='base32hex')
def b32hexdecode(s, casefold=False):
# base32hex does not have the 01 mapping
return _b32decode(_b32hexalphabet, s, casefold)
b32hexdecode.__doc__ = _B32_DECODE_DOCSTRING.format(encoding='base32hex',
extra_args='')
# RFC 3548, Base 16 Alphabet specifies uppercase, but hexlify() returns
# lowercase. The RFC also recommends against accepting input case
# insensitively.

70
Lib/test/test_base64.py
View file

@ -351,6 +351,76 @@ def test_b32decode_error(self):
with self.assertRaises(binascii.Error):
base64.b32decode(data.decode('ascii'))
def test_b32hexencode(self):
test_cases = [
# to_encode, expected
(b'', b''),
(b'\x00', b'00======'),
(b'a', b'C4======'),
(b'ab', b'C5H0===='),
(b'abc', b'C5H66==='),
(b'abcd', b'C5H66P0='),
(b'abcde', b'C5H66P35'),
]
for to_encode, expected in test_cases:
with self.subTest(to_decode=to_encode):
self.assertEqual(base64.b32hexencode(to_encode), expected)
def test_b32hexencode_other_types(self):
self.check_other_types(base64.b32hexencode, b'abcd', b'C5H66P0=')
self.check_encode_type_errors(base64.b32hexencode)
def test_b32hexdecode(self):
test_cases = [
# to_decode, expected, casefold
(b'', b'', False),
(b'00======', b'\x00', False),
(b'C4======', b'a', False),
(b'C5H0====', b'ab', False),
(b'C5H66===', b'abc', False),
(b'C5H66P0=', b'abcd', False),
(b'C5H66P35', b'abcde', False),
(b'', b'', True),
(b'00======', b'\x00', True),
(b'C4======', b'a', True),
(b'C5H0====', b'ab', True),
(b'C5H66===', b'abc', True),
(b'C5H66P0=', b'abcd', True),
(b'C5H66P35', b'abcde', True),
(b'c4======', b'a', True),
(b'c5h0====', b'ab', True),
(b'c5h66===', b'abc', True),
(b'c5h66p0=', b'abcd', True),
(b'c5h66p35', b'abcde', True),
]
for to_decode, expected, casefold in test_cases:
with self.subTest(to_decode=to_decode, casefold=casefold):
self.assertEqual(base64.b32hexdecode(to_decode, casefold),
expected)
self.assertEqual(base64.b32hexdecode(to_decode.decode('ascii'),
casefold), expected)
def test_b32hexdecode_other_types(self):
self.check_other_types(base64.b32hexdecode, b'C5H66===', b'abc')
self.check_decode_type_errors(base64.b32hexdecode)
def test_b32hexdecode_error(self):
tests = [b'abc', b'ABCDEF==', b'==ABCDEF', b'c4======']
prefixes = [b'M', b'ME', b'MFRA', b'MFRGG', b'MFRGGZA', b'MFRGGZDF']
for i in range(0, 17):
if i:
tests.append(b'='*i)
for prefix in prefixes:
if len(prefix) + i != 8:
tests.append(prefix + b'='*i)
for data in tests:
with self.subTest(to_decode=data):
with self.assertRaises(binascii.Error):
base64.b32hexdecode(data)
with self.assertRaises(binascii.Error):
base64.b32hexdecode(data.decode('ascii'))
def test_b16encode(self):
eq = self.assertEqual
eq(base64.b16encode(b'\x01\x02\xab\xcd\xef'), b'0102ABCDEF')

2
Misc/NEWS.d/next/Library/2020-05-27-00-09-52.bpo-16995.4niOT7.rst Normal file
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@ -0,0 +1,2 @@
Add :func:`base64.b32hexencode` and :func:`base64.b32hexdecode` to support the
Base32 Encoding with Extended Hex Alphabet.