1 /*
2 * Constant-time equality testing of memory regions.
3 *
4 * Authors:
5 *
6 * James Yonan <james@openvpn.net>
7 * Daniel Borkmann <dborkman@redhat.com>
8 *
9 * This file is provided under a dual BSD/GPLv2 license. When using or
10 * redistributing this file, you may do so under either license.
11 *
12 * GPL LICENSE SUMMARY
13 *
14 * Copyright(c) 2013 OpenVPN Technologies, Inc. All rights reserved.
15 *
16 * This program is free software; you can redistribute it and/or modify
17 * it under the terms of version 2 of the GNU General Public License as
18 * published by the Free Software Foundation.
19 *
20 * This program is distributed in the hope that it will be useful, but
21 * WITHOUT ANY WARRANTY; without even the implied warranty of
22 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
23 * General Public License for more details.
24 *
25 * You should have received a copy of the GNU General Public License
26 * along with this program; if not, write to the Free Software
27 * Foundation, Inc., 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA.
28 * The full GNU General Public License is included in this distribution
29 * in the file called LICENSE.GPL.
30 *
31 * BSD LICENSE
32 *
33 * Copyright(c) 2013 OpenVPN Technologies, Inc. All rights reserved.
34 *
35 * Redistribution and use in source and binary forms, with or without
36 * modification, are permitted provided that the following conditions
37 * are met:
38 *
39 * * Redistributions of source code must retain the above copyright
40 * notice, this list of conditions and the following disclaimer.
41 * * Redistributions in binary form must reproduce the above copyright
42 * notice, this list of conditions and the following disclaimer in
43 * the documentation and/or other materials provided with the
44 * distribution.
45 * * Neither the name of OpenVPN Technologies nor the names of its
46 * contributors may be used to endorse or promote products derived
47 * from this software without specific prior written permission.
48 *
49 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
50 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
51 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
52 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
53 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
54 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
55 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
56 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
57 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
58 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
59 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
60 */
61
62 #include <crypto/algapi.h>
63
64 #ifndef __HAVE_ARCH_CRYPTO_MEMNEQ
65
66 /* Generic path for arbitrary size */
67 static inline unsigned long
__crypto_memneq_generic(const void * a,const void * b,size_t size)68 __crypto_memneq_generic(const void *a, const void *b, size_t size)
69 {
70 unsigned long neq = 0;
71
72 #if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)
73 while (size >= sizeof(unsigned long)) {
74 neq |= *(unsigned long *)a ^ *(unsigned long *)b;
75 a += sizeof(unsigned long);
76 b += sizeof(unsigned long);
77 size -= sizeof(unsigned long);
78 }
79 #endif /* CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS */
80 while (size > 0) {
81 neq |= *(unsigned char *)a ^ *(unsigned char *)b;
82 a += 1;
83 b += 1;
84 size -= 1;
85 }
86 return neq;
87 }
88
89 /* Loop-free fast-path for frequently used 16-byte size */
__crypto_memneq_16(const void * a,const void * b)90 static inline unsigned long __crypto_memneq_16(const void *a, const void *b)
91 {
92 #ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
93 if (sizeof(unsigned long) == 8)
94 return ((*(unsigned long *)(a) ^ *(unsigned long *)(b))
95 | (*(unsigned long *)(a+8) ^ *(unsigned long *)(b+8)));
96 else if (sizeof(unsigned int) == 4)
97 return ((*(unsigned int *)(a) ^ *(unsigned int *)(b))
98 | (*(unsigned int *)(a+4) ^ *(unsigned int *)(b+4))
99 | (*(unsigned int *)(a+8) ^ *(unsigned int *)(b+8))
100 | (*(unsigned int *)(a+12) ^ *(unsigned int *)(b+12)));
101 else
102 #endif /* CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS */
103 return ((*(unsigned char *)(a) ^ *(unsigned char *)(b))
104 | (*(unsigned char *)(a+1) ^ *(unsigned char *)(b+1))
105 | (*(unsigned char *)(a+2) ^ *(unsigned char *)(b+2))
106 | (*(unsigned char *)(a+3) ^ *(unsigned char *)(b+3))
107 | (*(unsigned char *)(a+4) ^ *(unsigned char *)(b+4))
108 | (*(unsigned char *)(a+5) ^ *(unsigned char *)(b+5))
109 | (*(unsigned char *)(a+6) ^ *(unsigned char *)(b+6))
110 | (*(unsigned char *)(a+7) ^ *(unsigned char *)(b+7))
111 | (*(unsigned char *)(a+8) ^ *(unsigned char *)(b+8))
112 | (*(unsigned char *)(a+9) ^ *(unsigned char *)(b+9))
113 | (*(unsigned char *)(a+10) ^ *(unsigned char *)(b+10))
114 | (*(unsigned char *)(a+11) ^ *(unsigned char *)(b+11))
115 | (*(unsigned char *)(a+12) ^ *(unsigned char *)(b+12))
116 | (*(unsigned char *)(a+13) ^ *(unsigned char *)(b+13))
117 | (*(unsigned char *)(a+14) ^ *(unsigned char *)(b+14))
118 | (*(unsigned char *)(a+15) ^ *(unsigned char *)(b+15)));
119 }
120
121 /* Compare two areas of memory without leaking timing information,
122 * and with special optimizations for common sizes. Users should
123 * not call this function directly, but should instead use
124 * crypto_memneq defined in crypto/algapi.h.
125 */
__crypto_memneq(const void * a,const void * b,size_t size)126 noinline unsigned long __crypto_memneq(const void *a, const void *b,
127 size_t size)
128 {
129 switch (size) {
130 case 16:
131 return __crypto_memneq_16(a, b);
132 default:
133 return __crypto_memneq_generic(a, b, size);
134 }
135 }
136 EXPORT_SYMBOL(__crypto_memneq);
137
138 #endif /* __HAVE_ARCH_CRYPTO_MEMNEQ */
139