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#include <linux/export.h>
64#include <linux/module.h>
65#include <linux/unaligned.h>
66
67/* Generic path for arbitrary size */
68static inline unsigned long
69__crypto_memneq_generic(const void *a, const void *b, size_t size)
70{
71 unsigned long neq = 0;
72
73#if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)
74 while (size >= sizeof(unsigned long)) {
75 neq |= get_unaligned((unsigned long *)a) ^
76 get_unaligned((unsigned long *)b);
77 OPTIMIZER_HIDE_VAR(neq);
78 a += sizeof(unsigned long);
79 b += sizeof(unsigned long);
80 size -= sizeof(unsigned long);
81 }
82#endif /* CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS */
83 while (size > 0) {
84 neq |= *(unsigned char *)a ^ *(unsigned char *)b;
85 OPTIMIZER_HIDE_VAR(neq);
86 a += 1;
87 b += 1;
88 size -= 1;
89 }
90 return neq;
91}
92
93/* Loop-free fast-path for frequently used 16-byte size */
94static inline unsigned long __crypto_memneq_16(const void *a, const void *b)
95{
96 unsigned long neq = 0;
97
98#ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
99 if (sizeof(unsigned long) == 8) {
100 neq |= get_unaligned((unsigned long *)a) ^
101 get_unaligned((unsigned long *)b);
102 OPTIMIZER_HIDE_VAR(neq);
103 neq |= get_unaligned((unsigned long *)(a + 8)) ^
104 get_unaligned((unsigned long *)(b + 8));
105 OPTIMIZER_HIDE_VAR(neq);
106 } else if (sizeof(unsigned int) == 4) {
107 neq |= get_unaligned((unsigned int *)a) ^
108 get_unaligned((unsigned int *)b);
109 OPTIMIZER_HIDE_VAR(neq);
110 neq |= get_unaligned((unsigned int *)(a + 4)) ^
111 get_unaligned((unsigned int *)(b + 4));
112 OPTIMIZER_HIDE_VAR(neq);
113 neq |= get_unaligned((unsigned int *)(a + 8)) ^
114 get_unaligned((unsigned int *)(b + 8));
115 OPTIMIZER_HIDE_VAR(neq);
116 neq |= get_unaligned((unsigned int *)(a + 12)) ^
117 get_unaligned((unsigned int *)(b + 12));
118 OPTIMIZER_HIDE_VAR(neq);
119 } else
120#endif /* CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS */
121 {
122 neq |= *(unsigned char *)(a) ^ *(unsigned char *)(b);
123 OPTIMIZER_HIDE_VAR(neq);
124 neq |= *(unsigned char *)(a+1) ^ *(unsigned char *)(b+1);
125 OPTIMIZER_HIDE_VAR(neq);
126 neq |= *(unsigned char *)(a+2) ^ *(unsigned char *)(b+2);
127 OPTIMIZER_HIDE_VAR(neq);
128 neq |= *(unsigned char *)(a+3) ^ *(unsigned char *)(b+3);
129 OPTIMIZER_HIDE_VAR(neq);
130 neq |= *(unsigned char *)(a+4) ^ *(unsigned char *)(b+4);
131 OPTIMIZER_HIDE_VAR(neq);
132 neq |= *(unsigned char *)(a+5) ^ *(unsigned char *)(b+5);
133 OPTIMIZER_HIDE_VAR(neq);
134 neq |= *(unsigned char *)(a+6) ^ *(unsigned char *)(b+6);
135 OPTIMIZER_HIDE_VAR(neq);
136 neq |= *(unsigned char *)(a+7) ^ *(unsigned char *)(b+7);
137 OPTIMIZER_HIDE_VAR(neq);
138 neq |= *(unsigned char *)(a+8) ^ *(unsigned char *)(b+8);
139 OPTIMIZER_HIDE_VAR(neq);
140 neq |= *(unsigned char *)(a+9) ^ *(unsigned char *)(b+9);
141 OPTIMIZER_HIDE_VAR(neq);
142 neq |= *(unsigned char *)(a+10) ^ *(unsigned char *)(b+10);
143 OPTIMIZER_HIDE_VAR(neq);
144 neq |= *(unsigned char *)(a+11) ^ *(unsigned char *)(b+11);
145 OPTIMIZER_HIDE_VAR(neq);
146 neq |= *(unsigned char *)(a+12) ^ *(unsigned char *)(b+12);
147 OPTIMIZER_HIDE_VAR(neq);
148 neq |= *(unsigned char *)(a+13) ^ *(unsigned char *)(b+13);
149 OPTIMIZER_HIDE_VAR(neq);
150 neq |= *(unsigned char *)(a+14) ^ *(unsigned char *)(b+14);
151 OPTIMIZER_HIDE_VAR(neq);
152 neq |= *(unsigned char *)(a+15) ^ *(unsigned char *)(b+15);
153 OPTIMIZER_HIDE_VAR(neq);
154 }
155
156 return neq;
157}
158
159/* Compare two areas of memory without leaking timing information,
160 * and with special optimizations for common sizes. Users should
161 * not call this function directly, but should instead use
162 * crypto_memneq defined in crypto/algapi.h.
163 */
164noinline unsigned long __crypto_memneq(const void *a, const void *b,
165 size_t size)
166{
167 switch (size) {
168 case 16:
169 return __crypto_memneq_16(a, b);
170 default:
171 return __crypto_memneq_generic(a, b, size);
172 }
173}
174EXPORT_SYMBOL(__crypto_memneq);
175