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170 lines
6.5 KiB
170 lines
6.5 KiB
/* |
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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 <[email protected]> |
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* Daniel Borkmann <[email protected]> |
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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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/* Make the optimizer believe the variable can be manipulated arbitrarily. */ |
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#define COMPILER_OPTIMIZER_HIDE_VAR(var) asm("" : "=r" (var) : "0" (var)) |
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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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COMPILER_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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COMPILER_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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COMPILER_OPTIMIZER_HIDE_VAR(neq); |
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neq |= *(unsigned long *)(a+8) ^ *(unsigned long *)(b+8); |
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COMPILER_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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COMPILER_OPTIMIZER_HIDE_VAR(neq); |
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neq |= *(unsigned int *)(a+4) ^ *(unsigned int *)(b+4); |
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COMPILER_OPTIMIZER_HIDE_VAR(neq); |
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neq |= *(unsigned int *)(a+8) ^ *(unsigned int *)(b+8); |
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COMPILER_OPTIMIZER_HIDE_VAR(neq); |
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neq |= *(unsigned int *)(a+12) ^ *(unsigned int *)(b+12); |
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COMPILER_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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COMPILER_OPTIMIZER_HIDE_VAR(neq); |
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neq |= *(unsigned char *)(a+1) ^ *(unsigned char *)(b+1); |
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COMPILER_OPTIMIZER_HIDE_VAR(neq); |
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neq |= *(unsigned char *)(a+2) ^ *(unsigned char *)(b+2); |
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COMPILER_OPTIMIZER_HIDE_VAR(neq); |
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neq |= *(unsigned char *)(a+3) ^ *(unsigned char *)(b+3); |
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COMPILER_OPTIMIZER_HIDE_VAR(neq); |
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neq |= *(unsigned char *)(a+4) ^ *(unsigned char *)(b+4); |
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COMPILER_OPTIMIZER_HIDE_VAR(neq); |
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neq |= *(unsigned char *)(a+5) ^ *(unsigned char *)(b+5); |
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COMPILER_OPTIMIZER_HIDE_VAR(neq); |
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neq |= *(unsigned char *)(a+6) ^ *(unsigned char *)(b+6); |
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COMPILER_OPTIMIZER_HIDE_VAR(neq); |
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neq |= *(unsigned char *)(a+7) ^ *(unsigned char *)(b+7); |
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COMPILER_OPTIMIZER_HIDE_VAR(neq); |
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neq |= *(unsigned char *)(a+8) ^ *(unsigned char *)(b+8); |
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COMPILER_OPTIMIZER_HIDE_VAR(neq); |
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neq |= *(unsigned char *)(a+9) ^ *(unsigned char *)(b+9); |
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COMPILER_OPTIMIZER_HIDE_VAR(neq); |
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neq |= *(unsigned char *)(a+10) ^ *(unsigned char *)(b+10); |
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COMPILER_OPTIMIZER_HIDE_VAR(neq); |
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neq |= *(unsigned char *)(a+11) ^ *(unsigned char *)(b+11); |
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COMPILER_OPTIMIZER_HIDE_VAR(neq); |
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neq |= *(unsigned char *)(a+12) ^ *(unsigned char *)(b+12); |
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COMPILER_OPTIMIZER_HIDE_VAR(neq); |
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neq |= *(unsigned char *)(a+13) ^ *(unsigned char *)(b+13); |
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COMPILER_OPTIMIZER_HIDE_VAR(neq); |
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neq |= *(unsigned char *)(a+14) ^ *(unsigned char *)(b+14); |
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COMPILER_OPTIMIZER_HIDE_VAR(neq); |
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neq |= *(unsigned char *)(a+15) ^ *(unsigned char *)(b+15); |
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COMPILER_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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#endif /* __HAVE_ARCH_CRYPTO_MEMNEQ */
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