45 lines
1.5 KiB
Python
45 lines
1.5 KiB
Python
# vim: tabstop=4 shiftwidth=4 softtabstop=4
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# Copyright 2011 OpenStack LLC.
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# 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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Authentication related utilities and helper functions.
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"""
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def auth_str_equal(provided, known):
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"""Constant-time string comparison.
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:params provided: the first string
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:params known: the second string
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:return: True if the strings are equal.
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This function takes two strings and compares them. It is intended to be
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used when doing a comparison for authentication purposes to help guard
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against timing attacks. When using the function for this purpose, always
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provide the user-provided password as the first argument. The time this
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function will take is always a factor of the length of this string.
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"""
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result = 0
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p_len = len(provided)
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k_len = len(known)
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for i in xrange(p_len):
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a = ord(provided[i]) if i < p_len else 0
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b = ord(known[i]) if i < k_len else 0
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result |= a ^ b
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return (p_len == k_len) & (result == 0)
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