e158c10ccb
1. There are some problems about the test method. problem 1: Unit tests may not cover our function, it depends on the python version that performed the test. problem 2: when using function 'constant_time_compare(first, second)', 'first' and 'second' params are usually HMAC digest values, it is not appropriate to use utf-8 encoded values as mock data. 2. The previous commit `f1d332a` lead into a bug, but due to the problem 1 and the problem 2, we did not find out the error. Change-Id: I1c29bfe69f8eda60f3c5caaf3e5447dd5b69b108 Closes-Bug: #1772851
46 lines
1.4 KiB
Python
46 lines
1.4 KiB
Python
# All Rights Reserved.
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#
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# Licensed under the Apache License, Version 2.0 (the "License"); you may
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# not use this file except in compliance with the License. You may obtain
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# a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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# License for the specific language governing permissions and limitations
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# under the License.
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"""
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Secret utilities.
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.. versionadded:: 3.5
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"""
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import hmac
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def _constant_time_compare(first, second):
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"""Return True if both string or binary inputs are equal, otherwise False.
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This function should take a constant amount of time regardless of
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how many characters in the strings match. This function uses an
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approach designed to prevent timing analysis by avoiding
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content-based short circuiting behaviour, making it appropriate
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for cryptography.
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"""
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first = str(first)
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second = str(second)
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if len(first) != len(second):
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return False
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result = 0
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for x, y in zip(first, second):
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result |= ord(x) ^ ord(y)
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return result == 0
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try:
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constant_time_compare = hmac.compare_digest
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except AttributeError:
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constant_time_compare = _constant_time_compare
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