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/*
* Constant-time equality testing of memory regions.
*
* Authors:
*
* James Yonan <james@openvpn.net>
* Daniel Borkmann <dborkman@redhat.com>
*
* This file is provided under a dual BSD/GPLv2 license. When using or
* redistributing this file, you may do so under either license.
*
* GPL LICENSE SUMMARY
*
* Copyright(c) 2013 OpenVPN Technologies, Inc. All rights reserved.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of version 2 of the GNU General Public License as
* published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA.
* The full GNU General Public License is included in this distribution
* in the file called LICENSE.GPL.
*
* BSD LICENSE
*
* Copyright(c) 2013 OpenVPN Technologies, Inc. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
* * Neither the name of OpenVPN Technologies nor the names of its
* contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include <crypto/algapi.h>
/* Make the optimizer believe the variable can be manipulated arbitrarily. */
#define COMPILER_OPTIMIZER_HIDE_VAR(var) asm("" : "=r" (var) : "0" (var))
#ifndef __HAVE_ARCH_CRYPTO_MEMNEQ
/* Generic path for arbitrary size */
static inline unsigned long
__crypto_memneq_generic(const void *a, const void *b, size_t size)
{
unsigned long neq = 0;
#if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)
while (size >= sizeof(unsigned long)) {
neq |= *(unsigned long *)a ^ *(unsigned long *)b;
COMPILER_OPTIMIZER_HIDE_VAR(neq);
a += sizeof(unsigned long);
b += sizeof(unsigned long);
size -= sizeof(unsigned long);
}
#endif /* CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS */
while (size > 0) {
neq |= *(unsigned char *)a ^ *(unsigned char *)b;
COMPILER_OPTIMIZER_HIDE_VAR(neq);
a += 1;
b += 1;
size -= 1;
}
return neq;
}
/* Loop-free fast-path for frequently used 16-byte size */
static inline unsigned long __crypto_memneq_16(const void *a, const void *b)
{
unsigned long neq = 0;
#ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
if (sizeof(unsigned long) == 8) {
neq |= *(unsigned long *)(a) ^ *(unsigned long *)(b);
COMPILER_OPTIMIZER_HIDE_VAR(neq);
neq |= *(unsigned long *)(a+8) ^ *(unsigned long *)(b+8);
COMPILER_OPTIMIZER_HIDE_VAR(neq);
} else if (sizeof(unsigned int) == 4) {
neq |= *(unsigned int *)(a) ^ *(unsigned int *)(b);
COMPILER_OPTIMIZER_HIDE_VAR(neq);
neq |= *(unsigned int *)(a+4) ^ *(unsigned int *)(b+4);
COMPILER_OPTIMIZER_HIDE_VAR(neq);
neq |= *(unsigned int *)(a+8) ^ *(unsigned int *)(b+8);
COMPILER_OPTIMIZER_HIDE_VAR(neq);
neq |= *(unsigned int *)(a+12) ^ *(unsigned int *)(b+12);
COMPILER_OPTIMIZER_HIDE_VAR(neq);
} else
#endif /* CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS */
{
neq |= *(unsigned char *)(a) ^ *(unsigned char *)(b);
COMPILER_OPTIMIZER_HIDE_VAR(neq);
neq |= *(unsigned char *)(a+1) ^ *(unsigned char *)(b+1);
COMPILER_OPTIMIZER_HIDE_VAR(neq);
neq |= *(unsigned char *)(a+2) ^ *(unsigned char *)(b+2);
COMPILER_OPTIMIZER_HIDE_VAR(neq);
neq |= *(unsigned char *)(a+3) ^ *(unsigned char *)(b+3);
COMPILER_OPTIMIZER_HIDE_VAR(neq);
neq |= *(unsigned char *)(a+4) ^ *(unsigned char *)(b+4);
COMPILER_OPTIMIZER_HIDE_VAR(neq);
neq |= *(unsigned char *)(a+5) ^ *(unsigned char *)(b+5);
COMPILER_OPTIMIZER_HIDE_VAR(neq);
neq |= *(unsigned char *)(a+6) ^ *(unsigned char *)(b+6);
COMPILER_OPTIMIZER_HIDE_VAR(neq);
neq |= *(unsigned char *)(a+7) ^ *(unsigned char *)(b+7);
COMPILER_OPTIMIZER_HIDE_VAR(neq);
neq |= *(unsigned char *)(a+8) ^ *(unsigned char *)(b+8);
COMPILER_OPTIMIZER_HIDE_VAR(neq);
neq |= *(unsigned char *)(a+9) ^ *(unsigned char *)(b+9);
COMPILER_OPTIMIZER_HIDE_VAR(neq);
neq |= *(unsigned char *)(a+10) ^ *(unsigned char *)(b+10);
COMPILER_OPTIMIZER_HIDE_VAR(neq);
neq |= *(unsigned char *)(a+11) ^ *(unsigned char *)(b+11);
COMPILER_OPTIMIZER_HIDE_VAR(neq);
neq |= *(unsigned char *)(a+12) ^ *(unsigned char *)(b+12);
COMPILER_OPTIMIZER_HIDE_VAR(neq);
neq |= *(unsigned char *)(a+13) ^ *(unsigned char *)(b+13);
COMPILER_OPTIMIZER_HIDE_VAR(neq);
neq |= *(unsigned char *)(a+14) ^ *(unsigned char *)(b+14);
COMPILER_OPTIMIZER_HIDE_VAR(neq);
neq |= *(unsigned char *)(a+15) ^ *(unsigned char *)(b+15);
COMPILER_OPTIMIZER_HIDE_VAR(neq);
}
return neq;
}
/* Compare two areas of memory without leaking timing information,
* and with special optimizations for common sizes. Users should
* not call this function directly, but should instead use
* crypto_memneq defined in crypto/algapi.h.
*/
noinline unsigned long __crypto_memneq(const void *a, const void *b,
size_t size)
{
switch (size) {
case 16:
return __crypto_memneq_16(a, b);
default:
return __crypto_memneq_generic(a, b, size);
}
}
#endif /* __HAVE_ARCH_CRYPTO_MEMNEQ */
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