Root/crypto/memneq.c

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

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