Branch data     Line data    Source code

       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 <crypto/algapi.h>
      63                 :            : 
      64                 :            : #ifndef __HAVE_ARCH_CRYPTO_MEMNEQ
      65                 :            : 
      66                 :            : /* Generic path for arbitrary size */
      67                 :            : static inline unsigned long
      68                 :          3 : __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                 :          3 :         while (size >= sizeof(unsigned long)) {
      74                 :          3 :                 neq |= *(unsigned long *)a ^ *(unsigned long *)b;
      75                 :          3 :                 OPTIMIZER_HIDE_VAR(neq);
      76                 :          3 :                 a += sizeof(unsigned long);
      77                 :          3 :                 b += sizeof(unsigned long);
      78                 :          3 :                 size -= sizeof(unsigned long);
      79                 :            :         }
      80                 :            : #endif /* CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS */
      81                 :          3 :         while (size > 0) {
      82                 :          3 :                 neq |= *(unsigned char *)a ^ *(unsigned char *)b;
      83                 :          3 :                 OPTIMIZER_HIDE_VAR(neq);
      84                 :          3 :                 a += 1;
      85                 :          3 :                 b += 1;
      86                 :          3 :                 size -= 1;
      87                 :            :         }
      88                 :          3 :         return neq;
      89                 :            : }
      90                 :            : 
      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)
      93                 :            : {
      94                 :            :         unsigned long neq = 0;
      95                 :            : 
      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                 :          0 :                 neq |= *(unsigned int *)(a)    ^ *(unsigned int *)(b);
     104                 :          0 :                 OPTIMIZER_HIDE_VAR(neq);
     105                 :          0 :                 neq |= *(unsigned int *)(a+4)  ^ *(unsigned int *)(b+4);
     106                 :          0 :                 OPTIMIZER_HIDE_VAR(neq);
     107                 :          0 :                 neq |= *(unsigned int *)(a+8)  ^ *(unsigned int *)(b+8);
     108                 :          0 :                 OPTIMIZER_HIDE_VAR(neq);
     109                 :          0 :                 neq |= *(unsigned int *)(a+12) ^ *(unsigned int *)(b+12);
     110                 :          0 :                 OPTIMIZER_HIDE_VAR(neq);
     111                 :            :         } else
     112                 :            : #endif /* CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS */
     113                 :            :         {
     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);
     146                 :            :         }
     147                 :            : 
     148                 :            :         return neq;
     149                 :            : }
     150                 :            : 
     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.
     155                 :            :  */
     156                 :          3 : noinline unsigned long __crypto_memneq(const void *a, const void *b,
     157                 :            :                                        size_t size)
     158                 :            : {
     159                 :          3 :         switch (size) {
     160                 :            :         case 16:
     161                 :          0 :                 return __crypto_memneq_16(a, b);
     162                 :            :         default:
     163                 :          3 :                 return __crypto_memneq_generic(a, b, size);
     164                 :            :         }
     165                 :            : }
     166                 :            : EXPORT_SYMBOL(__crypto_memneq);
     167                 :            : 
     168                 :            : #endif /* __HAVE_ARCH_CRYPTO_MEMNEQ */