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 ct_memcmp(const void *p1, const void *p2, size_t len) 56 { 57 const unsigned char *s1 = p1, *s2 = p2; 58 size_t i; 59 int r = 0; 60 61 for (i = 0; i < len; i++) 62 r |= (s1[i] ^ s2[i]); 63 return !!r; 64 } 65