47 lines
1.1 KiB
Python
47 lines
1.1 KiB
Python
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import decimal
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import hmac
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import numbers
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import sys
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PY2 = sys.version_info[0] == 2
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if PY2:
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from itertools import izip
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text_type = unicode # noqa: 821
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else:
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izip = zip
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text_type = str
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number_types = (numbers.Real, decimal.Decimal)
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def _constant_time_compare(val1, val2):
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"""Return ``True`` if the two strings are equal, ``False``
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otherwise.
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The time taken is independent of the number of characters that
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match. Do not use this function for anything else than comparision
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with known length targets.
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This is should be implemented in C in order to get it completely
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right.
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This is an alias of :func:`hmac.compare_digest` on Python>=2.7,3.3.
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"""
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len_eq = len(val1) == len(val2)
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if len_eq:
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result = 0
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left = val1
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else:
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result = 1
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left = val2
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for x, y in izip(bytearray(left), bytearray(val2)):
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result |= x ^ y
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return result == 0
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# Starting with 2.7/3.3 the standard library has a c-implementation for
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# constant time string compares.
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constant_time_compare = getattr(hmac, "compare_digest", _constant_time_compare)
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