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/* 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 |= get_unaligned((unsigned long *)a) ^
 75		       get_unaligned((unsigned long *)b);
 76		OPTIMIZER_HIDE_VAR(neq);
 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;
 84		OPTIMIZER_HIDE_VAR(neq);
 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 */
 93static inline unsigned long __crypto_memneq_16(const void *a, const void *b)
 94{
 95	unsigned long neq = 0;
 96
 97#ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
 98	if (sizeof(unsigned long) == 8) {
 99		neq |= get_unaligned((unsigned long *)a) ^
100		       get_unaligned((unsigned long *)b);
101		OPTIMIZER_HIDE_VAR(neq);
102		neq |= get_unaligned((unsigned long *)(a + 8)) ^
103		       get_unaligned((unsigned long *)(b + 8));
104		OPTIMIZER_HIDE_VAR(neq);
105	} else if (sizeof(unsigned int) == 4) {
106		neq |= get_unaligned((unsigned int *)a) ^
107		       get_unaligned((unsigned int *)b);
108		OPTIMIZER_HIDE_VAR(neq);
109		neq |= get_unaligned((unsigned int *)(a + 4)) ^
110		       get_unaligned((unsigned int *)(b + 4));
111		OPTIMIZER_HIDE_VAR(neq);
112		neq |= get_unaligned((unsigned int *)(a + 8)) ^
113		       get_unaligned((unsigned int *)(b + 8));
114		OPTIMIZER_HIDE_VAR(neq);
115		neq |= get_unaligned((unsigned int *)(a + 12)) ^
116		       get_unaligned((unsigned int *)(b + 12));
117		OPTIMIZER_HIDE_VAR(neq);
118	} else
119#endif /* CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS */
120	{
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;
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 */
163noinline 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}
173EXPORT_SYMBOL(__crypto_memneq);