osfmk/kern/memset_s.c

   1 /*
   2  * Copyright (c) 2016 Apple Inc. All rights reserved.
   3  *
   4  * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
   5  *
   6  * This file contains Original Code and/or Modifications of Original Code
   7  * as defined in and that are subject to the Apple Public Source License
   8  * Version 2.0 (the 'License'). You may not use this file except in
   9  * compliance with the License. The rights granted to you under the License
  10  * may not be used to create, or enable the creation or redistribution of,
  11  * unlawful or unlicensed copies of an Apple operating system, or to
  12  * circumvent, violate, or enable the circumvention or violation of, any
  13  * terms of an Apple operating system software license agreement.
  14  *
  15  * Please obtain a copy of the License at
  16  * http://www.opensource.apple.com/apsl/ and read it before using this file.
  17  *
  18  * The Original Code and all software distributed under the License are
  19  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  20  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  21  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  22  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  23  * Please see the License for the specific language governing rights and
  24  * limitations under the License.
  25  *
  26  * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
  27  */
  28
  29 #include <string.h>
  30 #include <sys/errno.h>
  31 #include <stdint.h>
  32
  33 extern void   *secure_memset(void *, int, size_t);
  34
  35 /*
  36  * The memset_s function copies the value c into the first n bytes
  37  * pointed by s. No more than smax bytes will be copied.
  38  *
  39  * In contrast to the memset function, calls to memset_s will never
  40  * be ''optimised away'' by a compiler, ensuring the memory copy
  41  * even if s is not accessed anymore after this call.
  42  */
  43 int
  44 memset_s(void *s, size_t smax, int c, size_t n)
  45 {
  46         int err = 0;
  47
  48         if (s == NULL) {
  49                 return EINVAL;
  50         }
  51         if (smax > RSIZE_MAX) {
  52                 return E2BIG;
  53         }
  54         if (n > smax) {
  55                 n = smax;
  56                 err = EOVERFLOW;
  57         }
  58
  59         /*
  60          * secure_memset is defined in assembly, we therefore
  61          * expect that the compiler will not inline the call.
  62          */
  63         secure_memset(s, c, n);
  64
  65         return err;
  66 }
  67
  68 int
  69 timingsafe_bcmp(const void *b1, const void *b2, size_t n)
  70 {
  71         const unsigned char *p1 = b1, *p2 = b2;
  72         unsigned char ret = 0;
  73
  74         for (; n > 0; n--) {
  75                 ret |= *p1++ ^ *p2++;
  76         }
  77
  78         /* map zero to zero and nonzero to one */
  79         return (ret + 0xff) >> 8;
  80 }