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  }