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