crypto/external/bsd/heimdal/dist/lib/roken/ct.c

   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 Högskolan
   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
  56 int
  57 ct_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 }