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