crypto.py 文件源码

def constant_time_compare(val1, val2):
        """
        Returns True if the two strings are equal, False otherwise.

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

        For the sake of simplicity, this function executes in constant time only
        when the two strings have the same length. It short-circuits when they
        have different lengths. Since Django only uses it to compare hashes of
        known expected length, this is acceptable.
        """
        if len(val1) != len(val2):
            return False
        result = 0
        if six.PY3 and isinstance(val1, bytes) and isinstance(val2, bytes):
            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