osfmk/corecrypto/cc/src/cc_cmp_safe.c

   1 /*
   2  *  cc_cmp_safe.c
   3  *  corecrypto
   4  *
   5  *  Created on 04/22/2014
   6  *
   7  *  Copyright (c) 2014,2015 Apple Inc. All rights reserved.
   8  *
   9  *
  10  * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
  11  *
  12  * This file contains Original Code and/or Modifications of Original Code
  13  * as defined in and that are subject to the Apple Public Source License
  14  * Version 2.0 (the 'License'). You may not use this file except in
  15  * compliance with the License. The rights granted to you under the License
  16  * may not be used to create, or enable the creation or redistribution of,
  17  * unlawful or unlicensed copies of an Apple operating system, or to
  18  * circumvent, violate, or enable the circumvention or violation of, any
  19  * terms of an Apple operating system software license agreement.
  20  *
  21  * Please obtain a copy of the License at
  22  * http://www.opensource.apple.com/apsl/ and read it before using this file.
  23  *
  24  * The Original Code and all software distributed under the License are
  25  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  26  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  27  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  28  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  29  * Please see the License for the specific language governing rights and
  30  * limitations under the License.
  31  *
  32  * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
  33  */
  34
  35 #include <corecrypto/cc_priv.h>
  36
  37 int
  38 cc_cmp_safe(size_t num, const void * ptr1, const void * ptr2)
  39 {
  40         size_t i;
  41         const uint8_t *s = (const uint8_t *)ptr1;
  42         const uint8_t *t = (const uint8_t *)ptr2;
  43         uint8_t flag = ((num <= 0)?1:0); // If 0 return an error
  44         for (i = 0; i < num; i++) {
  45                 flag |= (s[i] ^ t[i]);
  46         }
  47         CC_HEAVISIDE_STEP(flag, flag); // flag=(flag==0)?0:1;
  48         return flag; // 0 iff all bytes were equal, 1 if there is any difference
  49 }