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               0 : {
      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                 : }