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annotate libtomcrypt/src/misc/mem_neq.c @ 1861:2b3a8026a6ce

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Add re-exec for server This allows ASLR to re-randomize the address space for every connection, preventing some vulnerabilities from being exploitable by repeated probing. Overhead (memory and time) is yet to be confirmed. At present this is only enabled on Linux. Other BSD platforms with fexecve() would probably also work though have not been tested.
author Matt Johnston <matt@ucc.asn.au>
date Sun, 30 Jan 2022 10:14:56 +0800
parents 6dba84798cd5
children
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6dba84798cd5 Update to libtomcrypt 1.18.1, merged with Dropbear changes
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1 /* LibTomCrypt, modular cryptographic library -- Tom St Denis
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2 *
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3 * LibTomCrypt is a library that provides various cryptographic
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4 * algorithms in a highly modular and flexible manner.
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5 *
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6 * The library is free for all purposes without any express
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7 * guarantee it works.
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8 */
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9 #include "tomcrypt.h"
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10
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11 /**
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12 @file mem_neq.c
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13 Compare two blocks of memory for inequality in constant time.
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14 Steffen Jaeckel
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15 */
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16
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17 /**
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18 Compare two blocks of memory for inequality in constant time.
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19
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20 The usage is similar to that of standard memcmp, but you can only test
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21 if the memory is equal or not - you can not determine by how much the
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22 first different byte differs.
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23
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24 This function shall be used to compare results of cryptographic
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25 operations where inequality means most likely usage of a wrong key.
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26 The execution time has therefore to be constant as otherwise
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27 timing attacks could be possible.
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28
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29 @param a The first memory region
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30 @param b The second memory region
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31 @param len The length of the area to compare (octets)
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32
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33 @return 0 when a and b are equal for len bytes, 1 they are not equal.
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34 */
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35 int mem_neq(const void *a, const void *b, size_t len)
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36 {
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37 unsigned char ret = 0;
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38 const unsigned char* pa;
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39 const unsigned char* pb;
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40
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41 LTC_ARGCHK(a != NULL);
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42 LTC_ARGCHK(b != NULL);
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43
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44 pa = a;
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45 pb = b;
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46
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47 while (len-- > 0) {
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48 ret |= *pa ^ *pb;
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49 ++pa;
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50 ++pb;
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51 }
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52
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53 ret |= ret >> 4;
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54 ret |= ret >> 2;
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55 ret |= ret >> 1;
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56 ret &= 1;
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57
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58 return ret;
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59 }
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60
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61 /* ref: $Format:%D$ */
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62 /* git commit: $Format:%H$ */
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63 /* commit time: $Format:%ai$ */