1*ae771770SStanislav Sedov /*
2*ae771770SStanislav Sedov * Copyright (c) 2009 Kungliga Tekniska Högskolan
3*ae771770SStanislav Sedov * (Royal Institute of Technology, Stockholm, Sweden).
4*ae771770SStanislav Sedov * All rights reserved.
5*ae771770SStanislav Sedov *
6*ae771770SStanislav Sedov * Redistribution and use in source and binary forms, with or without
7*ae771770SStanislav Sedov * modification, are permitted provided that the following conditions
8*ae771770SStanislav Sedov * are met:
9*ae771770SStanislav Sedov *
10*ae771770SStanislav Sedov * 1. Redistributions of source code must retain the above copyright
11*ae771770SStanislav Sedov * notice, this list of conditions and the following disclaimer.
12*ae771770SStanislav Sedov *
13*ae771770SStanislav Sedov * 2. Redistributions in binary form must reproduce the above copyright
14*ae771770SStanislav Sedov * notice, this list of conditions and the following disclaimer in the
15*ae771770SStanislav Sedov * documentation and/or other materials provided with the distribution.
16*ae771770SStanislav Sedov *
17*ae771770SStanislav Sedov * 3. Neither the name of the Institute nor the names of its contributors
18*ae771770SStanislav Sedov * may be used to endorse or promote products derived from this software
19*ae771770SStanislav Sedov * without specific prior written permission.
20*ae771770SStanislav Sedov *
21*ae771770SStanislav Sedov * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
22*ae771770SStanislav Sedov * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
23*ae771770SStanislav Sedov * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
24*ae771770SStanislav Sedov * ARE DISCLAIMED. IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
25*ae771770SStanislav Sedov * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
26*ae771770SStanislav Sedov * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
27*ae771770SStanislav Sedov * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
28*ae771770SStanislav Sedov * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
29*ae771770SStanislav Sedov * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
30*ae771770SStanislav Sedov * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31*ae771770SStanislav Sedov * SUCH DAMAGE.
32*ae771770SStanislav Sedov */
33*ae771770SStanislav Sedov
34*ae771770SStanislav Sedov #include <config.h>
35*ae771770SStanislav Sedov #include "roken.h"
36*ae771770SStanislav Sedov
37*ae771770SStanislav Sedov /**
38*ae771770SStanislav Sedov * Constant time compare to memory regions. The reason for making it
39*ae771770SStanislav Sedov * constant time is to make sure that timeing information leak from
40*ae771770SStanislav Sedov * where in the function the diffrence is.
41*ae771770SStanislav Sedov *
42*ae771770SStanislav Sedov * ct_memcmp() can't be used to order memory regions like memcmp(),
43*ae771770SStanislav Sedov * for example, use ct_memcmp() with qsort().
44*ae771770SStanislav Sedov *
45*ae771770SStanislav Sedov * @param p1 memory region 1 to compare
46*ae771770SStanislav Sedov * @param p2 memory region 2 to compare
47*ae771770SStanislav Sedov * @param len length of memory
48*ae771770SStanislav Sedov *
49*ae771770SStanislav Sedov * @return 0 when the memory regions are equal, non zero if not
50*ae771770SStanislav Sedov *
51*ae771770SStanislav Sedov * @ingroup roken
52*ae771770SStanislav Sedov */
53*ae771770SStanislav Sedov
54*ae771770SStanislav Sedov int
ct_memcmp(const void * p1,const void * p2,size_t len)55*ae771770SStanislav Sedov ct_memcmp(const void *p1, const void *p2, size_t len)
56*ae771770SStanislav Sedov {
57*ae771770SStanislav Sedov const unsigned char *s1 = p1, *s2 = p2;
58*ae771770SStanislav Sedov size_t i;
59*ae771770SStanislav Sedov int r = 0;
60*ae771770SStanislav Sedov
61*ae771770SStanislav Sedov for (i = 0; i < len; i++)
62*ae771770SStanislav Sedov r |= (s1[i] ^ s2[i]);
63*ae771770SStanislav Sedov return !!r;
64*ae771770SStanislav Sedov }
65