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6bf37e5a JY |
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 | ||
1c16dfbe | 62 | #include <asm/unaligned.h> |
7033b937 EB |
63 | #include <crypto/algapi.h> |
64 | #include <linux/module.h> | |
6bf37e5a | 65 | |
6bf37e5a JY |
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)) { | |
1c16dfbe AB |
74 | neq |= get_unaligned((unsigned long *)a) ^ |
75 | get_unaligned((unsigned long *)b); | |
fe8c8a12 | 76 | OPTIMIZER_HIDE_VAR(neq); |
6bf37e5a JY |
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; | |
fe8c8a12 | 84 | OPTIMIZER_HIDE_VAR(neq); |
6bf37e5a JY |
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 | { | |
fe8c8a12 CEB |
95 | unsigned long neq = 0; |
96 | ||
6bf37e5a | 97 | #ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS |
fe8c8a12 | 98 | if (sizeof(unsigned long) == 8) { |
1c16dfbe AB |
99 | neq |= get_unaligned((unsigned long *)a) ^ |
100 | get_unaligned((unsigned long *)b); | |
fe8c8a12 | 101 | OPTIMIZER_HIDE_VAR(neq); |
1c16dfbe AB |
102 | neq |= get_unaligned((unsigned long *)(a + 8)) ^ |
103 | get_unaligned((unsigned long *)(b + 8)); | |
fe8c8a12 CEB |
104 | OPTIMIZER_HIDE_VAR(neq); |
105 | } else if (sizeof(unsigned int) == 4) { | |
1c16dfbe AB |
106 | neq |= get_unaligned((unsigned int *)a) ^ |
107 | get_unaligned((unsigned int *)b); | |
fe8c8a12 | 108 | OPTIMIZER_HIDE_VAR(neq); |
1c16dfbe AB |
109 | neq |= get_unaligned((unsigned int *)(a + 4)) ^ |
110 | get_unaligned((unsigned int *)(b + 4)); | |
fe8c8a12 | 111 | OPTIMIZER_HIDE_VAR(neq); |
1c16dfbe AB |
112 | neq |= get_unaligned((unsigned int *)(a + 8)) ^ |
113 | get_unaligned((unsigned int *)(b + 8)); | |
fe8c8a12 | 114 | OPTIMIZER_HIDE_VAR(neq); |
1c16dfbe AB |
115 | neq |= get_unaligned((unsigned int *)(a + 12)) ^ |
116 | get_unaligned((unsigned int *)(b + 12)); | |
fe8c8a12 | 117 | OPTIMIZER_HIDE_VAR(neq); |
e37b94eb | 118 | } else |
6bf37e5a | 119 | #endif /* CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS */ |
e37b94eb | 120 | { |
fe8c8a12 CEB |
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; | |
6bf37e5a JY |
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); |