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1 : : /*
2 : : * Copyright (c) 2009 Kungliga Tekniska Högskolan
3 : : * (Royal Institute of Technology, Stockholm, Sweden).
4 : : * All rights reserved.
5 : : *
6 : : * Redistribution and use in source and binary forms, with or without
7 : : * modification, are permitted provided that the following conditions
8 : : * are met:
9 : : *
10 : : * 1. Redistributions of source code must retain the above copyright
11 : : * notice, this list of conditions and the following disclaimer.
12 : : *
13 : : * 2. Redistributions in binary form must reproduce the above copyright
14 : : * notice, this list of conditions and the following disclaimer in the
15 : : * documentation and/or other materials provided with the distribution.
16 : : *
17 : : * 3. Neither the name of the Institute nor the names of its contributors
18 : : * may be used to endorse or promote products derived from this software
19 : : * without specific prior written permission.
20 : : *
21 : : * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
22 : : * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
23 : : * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
24 : : * ARE DISCLAIMED. IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
25 : : * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
26 : : * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
27 : : * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
28 : : * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
29 : : * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
30 : : * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31 : : * SUCH DAMAGE.
32 : : */
33 : :
34 : : #include <config.h>
35 : : #include "roken.h"
36 : :
37 : : /**
38 : : * Constant time compare to memory regions. The reason for making it
39 : : * constant time is to make sure that timeing information leak from
40 : : * where in the function the diffrence is.
41 : : *
42 : : * ct_memcmp() can't be used to order memory regions like memcmp(),
43 : : * for example, use ct_memcmp() with qsort().
44 : : *
45 : : * @param p1 memory region 1 to compare
46 : : * @param p2 memory region 2 to compare
47 : : * @param len length of memory
48 : : *
49 : : * @return 0 when the memory regions are equal, non zero if not
50 : : *
51 : : * @ingroup roken
52 : : */
53 : :
54 : : int
55 : 0 : ct_memcmp(const void *p1, const void *p2, size_t len)
56 : : {
57 : 0 : const unsigned char *s1 = p1, *s2 = p2;
58 : : size_t i;
59 : 0 : int r = 0;
60 : :
61 [ # # ]: 0 : for (i = 0; i < len; i++)
62 : 0 : r |= (s1[i] ^ s2[i]);
63 : 0 : return !!r;
64 : : }
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