2 * Constant-time equality testing of memory regions.
6 * James Yonan <james@openvpn.net>
7 * Daniel Borkmann <dborkman@redhat.com>
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62 #include <crypto/algapi.h>
64 #ifndef __HAVE_ARCH_CRYPTO_MEMNEQ
66 /* Generic path for arbitrary size */
67 static inline unsigned long
68 __crypto_memneq_generic(const void *a, const void *b, size_t size)
70 unsigned long neq = 0;
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);
80 #endif /* CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS */
82 neq |= *(unsigned char *)a ^ *(unsigned char *)b;
83 OPTIMIZER_HIDE_VAR(neq);
91 /* Loop-free fast-path for frequently used 16-byte size */
92 static inline unsigned long __crypto_memneq_16(const void *a, const void *b)
94 unsigned long neq = 0;
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);
112 #endif /* CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS */
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);
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.
156 noinline unsigned long __crypto_memneq(const void *a, const void *b,
161 return __crypto_memneq_16(a, b);
163 return __crypto_memneq_generic(a, b, size);
166 EXPORT_SYMBOL(__crypto_memneq);
168 #endif /* __HAVE_ARCH_CRYPTO_MEMNEQ */