]>
git.ipfire.org Git - people/ms/linux.git/blob - lib/memneq.c
2 * Constant-time equality testing of memory regions.
6 * James Yonan <james@openvpn.net>
7 * Daniel Borkmann <dborkman@redhat.com>
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.
14 * Copyright(c) 2013 OpenVPN Technologies, Inc. All rights reserved.
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.
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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.
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.
33 * Copyright(c) 2013 OpenVPN Technologies, Inc. All rights reserved.
35 * Redistribution and use in source and binary forms, with or without
36 * modification, are permitted provided that the following conditions
39 * * Redistributions of source code must retain the above copyright
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53 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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62 #include <crypto/algapi.h>
63 #include <asm/unaligned.h>
65 #ifndef __HAVE_ARCH_CRYPTO_MEMNEQ
67 /* Generic path for arbitrary size */
68 static inline unsigned long
69 __crypto_memneq_generic(const void *a
, const void *b
, size_t size
)
71 unsigned long neq
= 0;
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);
82 #endif /* CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS */
84 neq
|= *(unsigned char *)a
^ *(unsigned char *)b
;
85 OPTIMIZER_HIDE_VAR(neq
);
93 /* Loop-free fast-path for frequently used 16-byte size */
94 static inline unsigned long __crypto_memneq_16(const void *a
, const void *b
)
96 unsigned long neq
= 0;
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
);
120 #endif /* CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS */
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
);
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.
164 noinline
unsigned long __crypto_memneq(const void *a
, const void *b
,
169 return __crypto_memneq_16(a
, b
);
171 return __crypto_memneq_generic(a
, b
, size
);
174 EXPORT_SYMBOL(__crypto_memneq
);
176 #endif /* __HAVE_ARCH_CRYPTO_MEMNEQ */