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# All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License"); you may
# not use this file except in compliance with the License. You may obtain
# a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
# License for the specific language governing permissions and limitations
# under the License.
"""
Secret utilities.
.. versionadded:: 3.5
"""
import hmac
import six
try:
constant_time_compare = hmac.compare_digest
except AttributeError:
def constant_time_compare(first, second):
"""Returns True if both string inputs are equal, otherwise False.
This function should take a constant amount of time regardless of
how many characters in the strings match. This function uses an
approach designed to prevent timing analysis by avoiding
content-based short circuiting behaviour, making it appropriate
for cryptography.
"""
if isinstance(first, six.string_types):
first = first.encode('utf-8')
if isinstance(second, six.string_types):
second = second.encode('utf-8')
if len(first) != len(second):
return False
result = 0
for x, y in zip(first, second):
result |= ord(x) ^ ord(y)
return result == 0
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