xref: /openbmc/linux/lib/crypto/memneq.c (revision 7033b937)
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 #ifndef __HAVE_ARCH_CRYPTO_MEMNEQ
67 
68 /* Generic path for arbitrary size */
69 static inline unsigned long
70 __crypto_memneq_generic(const void *a, const void *b, size_t size)
71 {
72 	unsigned long neq = 0;
73 
74 #if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)
75 	while (size >= sizeof(unsigned long)) {
76 		neq |= get_unaligned((unsigned long *)a) ^
77 		       get_unaligned((unsigned long *)b);
78 		OPTIMIZER_HIDE_VAR(neq);
79 		a += sizeof(unsigned long);
80 		b += sizeof(unsigned long);
81 		size -= sizeof(unsigned long);
82 	}
83 #endif /* CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS */
84 	while (size > 0) {
85 		neq |= *(unsigned char *)a ^ *(unsigned char *)b;
86 		OPTIMIZER_HIDE_VAR(neq);
87 		a += 1;
88 		b += 1;
89 		size -= 1;
90 	}
91 	return neq;
92 }
93 
94 /* Loop-free fast-path for frequently used 16-byte size */
95 static inline unsigned long __crypto_memneq_16(const void *a, const void *b)
96 {
97 	unsigned long neq = 0;
98 
99 #ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
100 	if (sizeof(unsigned long) == 8) {
101 		neq |= get_unaligned((unsigned long *)a) ^
102 		       get_unaligned((unsigned long *)b);
103 		OPTIMIZER_HIDE_VAR(neq);
104 		neq |= get_unaligned((unsigned long *)(a + 8)) ^
105 		       get_unaligned((unsigned long *)(b + 8));
106 		OPTIMIZER_HIDE_VAR(neq);
107 	} else if (sizeof(unsigned int) == 4) {
108 		neq |= get_unaligned((unsigned int *)a) ^
109 		       get_unaligned((unsigned int *)b);
110 		OPTIMIZER_HIDE_VAR(neq);
111 		neq |= get_unaligned((unsigned int *)(a + 4)) ^
112 		       get_unaligned((unsigned int *)(b + 4));
113 		OPTIMIZER_HIDE_VAR(neq);
114 		neq |= get_unaligned((unsigned int *)(a + 8)) ^
115 		       get_unaligned((unsigned int *)(b + 8));
116 		OPTIMIZER_HIDE_VAR(neq);
117 		neq |= get_unaligned((unsigned int *)(a + 12)) ^
118 		       get_unaligned((unsigned int *)(b + 12));
119 		OPTIMIZER_HIDE_VAR(neq);
120 	} else
121 #endif /* CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS */
122 	{
123 		neq |= *(unsigned char *)(a)    ^ *(unsigned char *)(b);
124 		OPTIMIZER_HIDE_VAR(neq);
125 		neq |= *(unsigned char *)(a+1)  ^ *(unsigned char *)(b+1);
126 		OPTIMIZER_HIDE_VAR(neq);
127 		neq |= *(unsigned char *)(a+2)  ^ *(unsigned char *)(b+2);
128 		OPTIMIZER_HIDE_VAR(neq);
129 		neq |= *(unsigned char *)(a+3)  ^ *(unsigned char *)(b+3);
130 		OPTIMIZER_HIDE_VAR(neq);
131 		neq |= *(unsigned char *)(a+4)  ^ *(unsigned char *)(b+4);
132 		OPTIMIZER_HIDE_VAR(neq);
133 		neq |= *(unsigned char *)(a+5)  ^ *(unsigned char *)(b+5);
134 		OPTIMIZER_HIDE_VAR(neq);
135 		neq |= *(unsigned char *)(a+6)  ^ *(unsigned char *)(b+6);
136 		OPTIMIZER_HIDE_VAR(neq);
137 		neq |= *(unsigned char *)(a+7)  ^ *(unsigned char *)(b+7);
138 		OPTIMIZER_HIDE_VAR(neq);
139 		neq |= *(unsigned char *)(a+8)  ^ *(unsigned char *)(b+8);
140 		OPTIMIZER_HIDE_VAR(neq);
141 		neq |= *(unsigned char *)(a+9)  ^ *(unsigned char *)(b+9);
142 		OPTIMIZER_HIDE_VAR(neq);
143 		neq |= *(unsigned char *)(a+10) ^ *(unsigned char *)(b+10);
144 		OPTIMIZER_HIDE_VAR(neq);
145 		neq |= *(unsigned char *)(a+11) ^ *(unsigned char *)(b+11);
146 		OPTIMIZER_HIDE_VAR(neq);
147 		neq |= *(unsigned char *)(a+12) ^ *(unsigned char *)(b+12);
148 		OPTIMIZER_HIDE_VAR(neq);
149 		neq |= *(unsigned char *)(a+13) ^ *(unsigned char *)(b+13);
150 		OPTIMIZER_HIDE_VAR(neq);
151 		neq |= *(unsigned char *)(a+14) ^ *(unsigned char *)(b+14);
152 		OPTIMIZER_HIDE_VAR(neq);
153 		neq |= *(unsigned char *)(a+15) ^ *(unsigned char *)(b+15);
154 		OPTIMIZER_HIDE_VAR(neq);
155 	}
156 
157 	return neq;
158 }
159 
160 /* Compare two areas of memory without leaking timing information,
161  * and with special optimizations for common sizes.  Users should
162  * not call this function directly, but should instead use
163  * crypto_memneq defined in crypto/algapi.h.
164  */
165 noinline unsigned long __crypto_memneq(const void *a, const void *b,
166 				       size_t size)
167 {
168 	switch (size) {
169 	case 16:
170 		return __crypto_memneq_16(a, b);
171 	default:
172 		return __crypto_memneq_generic(a, b, size);
173 	}
174 }
175 EXPORT_SYMBOL(__crypto_memneq);
176 
177 #endif /* __HAVE_ARCH_CRYPTO_MEMNEQ */
178 
179 MODULE_LICENSE("GPL");
180