ct.c revision 1.1.1.1 
1/*	$NetBSD: ct.c,v 1.1.1.1 2011/04/13 18:15:40 elric Exp $	*/
2
3/*
4 * Copyright (c) 2009 Kungliga Tekniska H��gskolan
5 * (Royal Institute of Technology, Stockholm, Sweden).
6 * All rights reserved.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 *
12 * 1. Redistributions of source code must retain the above copyright
13 *    notice, this list of conditions and the following disclaimer.
14 *
15 * 2. Redistributions in binary form must reproduce the above copyright
16 *    notice, this list of conditions and the following disclaimer in the
17 *    documentation and/or other materials provided with the distribution.
18 *
19 * 3. Neither the name of the Institute nor the names of its contributors
20 *    may be used to endorse or promote products derived from this software
21 *    without specific prior written permission.
22 *
23 * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
24 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
25 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
26 * ARE DISCLAIMED.  IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
27 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
28 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
29 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
30 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
31 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
32 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
33 * SUCH DAMAGE.
34 */
35
36#include <config.h>
37#include <krb5/roken.h>
38
39/**
40 * Constant time compare to memory regions. The reason for making it
41 * constant time is to make sure that timeing information leak from
42 * where in the function the diffrence is.
43 *
44 * ct_memcmp() can't be used to order memory regions like memcmp(),
45 * for example, use ct_memcmp() with qsort().
46 *
47 * @param p1 memory region 1 to compare
48 * @param p2 memory region 2 to compare
49 * @param len length of memory
50 *
51 * @return 0 when the memory regions are equal, non zero if not
52 *
53 * @ingroup roken
54 */
55
56int
57ct_memcmp(const void *p1, const void *p2, size_t len)
58{
59    const unsigned char *s1 = p1, *s2 = p2;
60    size_t i;
61    int r = 0;
62
63    for (i = 0; i < len; i++)
64	r |= (s1[i] ^ s2[i]);
65    return !!r;
66}
67