[py3] Fixed #17040 -- ported django.utils.crypto.constant_time_compare.

from django.conf import settings

from django.utils.encoding import smart_bytes

from django.utils import six

from django.utils.six.moves import xrange

def constant_time_compare(val1, val2):

    """

    Returns True if the two strings are equal, False otherwise.

    Returns True if the two bytestrings are equal, False otherwise.

    The time taken is independent of the number of characters that match.

    """

    if not (isinstance(val1, bytes) and isinstance(val2, bytes)):

        raise TypeError("constant_time_compare only supports bytes")

    if len(val1) != len(val2):

        return False

    result = 0

    if six.PY3:

        for x, y in zip(val1, val2):

            result |= x ^ y

    else:

        for x, y in zip(val1, val2):

            result |= ord(x) ^ ord(y)

    return result == 0

import hashlib

from django.utils import unittest

from django.utils.crypto import pbkdf2

from django.utils.crypto import constant_time_compare, pbkdf2

class TestUtilsCryptoMisc(unittest.TestCase):

    def test_constant_time_compare(self):

        # It's hard to test for constant time, just test the result.

        self.assertTrue(constant_time_compare(b'spam', b'spam'))

        self.assertFalse(constant_time_compare(b'spam', b'eggs'))

        with self.assertRaises(TypeError):

            constant_time_compare('spam', 'spam')

class TestUtilsCryptoPBKDF2(unittest.TestCase):

from .archive import TestBzip2Tar, TestGzipTar, TestTar, TestZip

from .baseconv import TestBaseConv

from .checksums import TestUtilsChecksums

from .crypto import TestUtilsCryptoPBKDF2

from .crypto import TestUtilsCryptoMisc, TestUtilsCryptoPBKDF2

from .datastructures import (DictWrapperTests, ImmutableListTests,

    MergeDictTests, MultiValueDictTests, SortedDictTests)

from .dateformat import DateFormatTests