[164] | 1 | /*****************************************************************************
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| 2 | * randm.c - Random number generator program file.
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| 3 | *
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| 4 | * Copyright (c) 2003 by Marc Boucher, Services Informatiques (MBSI) inc.
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| 5 | * Copyright (c) 1998 by Global Election Systems Inc.
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| 6 | *
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| 7 | * The authors hereby grant permission to use, copy, modify, distribute,
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| 8 | * and license this software and its documentation for any purpose, provided
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| 9 | * that existing copyright notices are retained in all copies and that this
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| 10 | * notice and the following disclaimer are included verbatim in any
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| 11 | * distributions. No written agreement, license, or royalty fee is required
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| 12 | * for any of the authorized uses.
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| 13 | *
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| 14 | * THIS SOFTWARE IS PROVIDED BY THE CONTRIBUTORS *AS IS* AND ANY EXPRESS OR
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| 15 | * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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| 16 | * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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| 17 | * IN NO EVENT SHALL THE CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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| 18 | * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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| 19 | * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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| 20 | * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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| 21 | * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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| 22 | * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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| 23 | * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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| 24 | *
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| 25 | ******************************************************************************
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| 26 | * REVISION HISTORY
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| 27 | *
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| 28 | * 03-01-01 Marc Boucher <marc@mbsi.ca>
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| 29 | * Ported to lwIP.
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| 30 | * 98-06-03 Guy Lancaster <lancasterg@acm.org>, Global Election Systems Inc.
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| 31 | * Extracted from avos.
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| 32 | *****************************************************************************/
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| 33 |
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| 34 | #include "lwip/opt.h"
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| 35 |
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| 36 | #if PPP_SUPPORT /* don't build if not configured for use in lwipopts.h */
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| 37 |
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| 38 | #include "md5.h"
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| 39 | #include "randm.h"
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| 40 |
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| 41 | #include "ppp_impl.h"
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| 42 | #include "pppdebug.h"
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| 43 |
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| 44 | #include <string.h>
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| 45 |
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| 46 | #if MD5_SUPPORT /* this module depends on MD5 */
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| 47 | #define RANDPOOLSZ 16 /* Bytes stored in the pool of randomness. */
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| 48 |
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| 49 | /*****************************/
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| 50 | /*** LOCAL DATA STRUCTURES ***/
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| 51 | /*****************************/
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| 52 | static char randPool[RANDPOOLSZ]; /* Pool of randomness. */
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| 53 | static long randCount = 0; /* Pseudo-random incrementer */
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| 54 |
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| 55 |
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| 56 | /***********************************/
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| 57 | /*** PUBLIC FUNCTION DEFINITIONS ***/
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| 58 | /***********************************/
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| 59 | /*
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| 60 | * Initialize the random number generator.
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| 61 | *
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| 62 | * Since this is to be called on power up, we don't have much
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| 63 | * system randomess to work with. Here all we use is the
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| 64 | * real-time clock. We'll accumulate more randomness as soon
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| 65 | * as things start happening.
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| 66 | */
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| 67 | void
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| 68 | avRandomInit()
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| 69 | {
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| 70 | avChurnRand(NULL, 0);
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| 71 | }
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| 72 |
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| 73 | /*
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| 74 | * Churn the randomness pool on a random event. Call this early and often
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| 75 | * on random and semi-random system events to build randomness in time for
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| 76 | * usage. For randomly timed events, pass a null pointer and a zero length
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| 77 | * and this will use the system timer and other sources to add randomness.
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| 78 | * If new random data is available, pass a pointer to that and it will be
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| 79 | * included.
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| 80 | *
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| 81 | * Ref: Applied Cryptography 2nd Ed. by Bruce Schneier p. 427
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| 82 | */
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| 83 | void
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| 84 | avChurnRand(char *randData, u32_t randLen)
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| 85 | {
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| 86 | MD5_CTX md5;
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| 87 |
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| 88 | /* LWIP_DEBUGF(LOG_INFO, ("churnRand: %u@%P\n", randLen, randData)); */
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| 89 | MD5Init(&md5);
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| 90 | MD5Update(&md5, (u_char *)randPool, sizeof(randPool));
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| 91 | if (randData) {
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| 92 | MD5Update(&md5, (u_char *)randData, randLen);
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| 93 | } else {
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| 94 | struct {
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| 95 | /* INCLUDE fields for any system sources of randomness */
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| 96 | char foobar;
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| 97 | } sysData;
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| 98 |
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| 99 | /* Load sysData fields here. */
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| 100 | MD5Update(&md5, (u_char *)&sysData, sizeof(sysData));
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| 101 | }
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| 102 | MD5Final((u_char *)randPool, &md5);
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| 103 | /* LWIP_DEBUGF(LOG_INFO, ("churnRand: -> 0\n")); */
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| 104 | }
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| 105 |
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| 106 | /*
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| 107 | * Use the random pool to generate random data. This degrades to pseudo
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| 108 | * random when used faster than randomness is supplied using churnRand().
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| 109 | * Note: It's important that there be sufficient randomness in randPool
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| 110 | * before this is called for otherwise the range of the result may be
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| 111 | * narrow enough to make a search feasible.
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| 112 | *
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| 113 | * Ref: Applied Cryptography 2nd Ed. by Bruce Schneier p. 427
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| 114 | *
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| 115 | * XXX Why does he not just call churnRand() for each block? Probably
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| 116 | * so that you don't ever publish the seed which could possibly help
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| 117 | * predict future values.
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| 118 | * XXX Why don't we preserve md5 between blocks and just update it with
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| 119 | * randCount each time? Probably there is a weakness but I wish that
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| 120 | * it was documented.
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| 121 | */
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| 122 | void
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| 123 | avGenRand(char *buf, u32_t bufLen)
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| 124 | {
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| 125 | MD5_CTX md5;
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| 126 | u_char tmp[16];
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| 127 | u32_t n;
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| 128 |
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| 129 | while (bufLen > 0) {
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| 130 | n = LWIP_MIN(bufLen, RANDPOOLSZ);
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| 131 | MD5Init(&md5);
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| 132 | MD5Update(&md5, (u_char *)randPool, sizeof(randPool));
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| 133 | MD5Update(&md5, (u_char *)&randCount, sizeof(randCount));
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| 134 | MD5Final(tmp, &md5);
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| 135 | randCount++;
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| 136 | MEMCPY(buf, tmp, n);
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| 137 | buf += n;
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| 138 | bufLen -= n;
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| 139 | }
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| 140 | }
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| 141 |
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| 142 | /*
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| 143 | * Return a new random number.
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| 144 | */
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| 145 | u32_t
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| 146 | avRandom()
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| 147 | {
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| 148 | u32_t newRand;
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| 149 |
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| 150 | avGenRand((char *)&newRand, sizeof(newRand));
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| 151 |
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| 152 | return newRand;
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| 153 | }
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| 154 |
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| 155 | #else /* MD5_SUPPORT */
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| 156 |
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| 157 | /*****************************/
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| 158 | /*** LOCAL DATA STRUCTURES ***/
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| 159 | /*****************************/
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| 160 | static int avRandomized = 0; /* Set when truely randomized. */
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| 161 | static u32_t avRandomSeed = 0; /* Seed used for random number generation. */
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| 162 |
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| 163 |
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| 164 | /***********************************/
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| 165 | /*** PUBLIC FUNCTION DEFINITIONS ***/
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| 166 | /***********************************/
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| 167 | /*
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| 168 | * Initialize the random number generator.
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| 169 | *
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| 170 | * Here we attempt to compute a random number seed but even if
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| 171 | * it isn't random, we'll randomize it later.
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| 172 | *
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| 173 | * The current method uses the fields from the real time clock,
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| 174 | * the idle process counter, the millisecond counter, and the
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| 175 | * hardware timer tick counter. When this is invoked
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| 176 | * in startup(), then the idle counter and timer values may
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| 177 | * repeat after each boot and the real time clock may not be
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| 178 | * operational. Thus we call it again on the first random
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| 179 | * event.
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| 180 | */
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| 181 | void
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| 182 | avRandomInit()
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| 183 | {
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| 184 | #if 0
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| 185 | /* Get a pointer into the last 4 bytes of clockBuf. */
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| 186 | u32_t *lptr1 = (u32_t *)((char *)&clockBuf[3]);
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| 187 |
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| 188 | /*
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| 189 | * Initialize our seed using the real-time clock, the idle
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| 190 | * counter, the millisecond timer, and the hardware timer
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| 191 | * tick counter. The real-time clock and the hardware
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| 192 | * tick counter are the best sources of randomness but
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| 193 | * since the tick counter is only 16 bit (and truncated
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| 194 | * at that), the idle counter and millisecond timer
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| 195 | * (which may be small values) are added to help
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| 196 | * randomize the lower 16 bits of the seed.
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| 197 | */
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| 198 | readClk();
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| 199 | avRandomSeed += *(u32_t *)clockBuf + *lptr1 + OSIdleCtr
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| 200 | + ppp_mtime() + ((u32_t)TM1 << 16) + TM1;
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| 201 | #else
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| 202 | avRandomSeed += sys_jiffies(); /* XXX */
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| 203 | #endif
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| 204 |
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| 205 | /* Initialize the Borland random number generator. */
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| 206 | srand((unsigned)avRandomSeed);
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| 207 | }
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| 208 |
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| 209 | /*
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| 210 | * Randomize our random seed value. Here we use the fact that
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| 211 | * this function is called at *truely random* times by the polling
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| 212 | * and network functions. Here we only get 16 bits of new random
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| 213 | * value but we use the previous value to randomize the other 16
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| 214 | * bits.
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| 215 | */
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| 216 | void
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| 217 | avRandomize(void)
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| 218 | {
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| 219 | static u32_t last_jiffies;
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| 220 |
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| 221 | if (!avRandomized) {
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| 222 | avRandomized = !0;
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| 223 | avRandomInit();
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| 224 | /* The initialization function also updates the seed. */
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| 225 | } else {
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| 226 | /* avRandomSeed += (avRandomSeed << 16) + TM1; */
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| 227 | avRandomSeed += (sys_jiffies() - last_jiffies); /* XXX */
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| 228 | }
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| 229 | last_jiffies = sys_jiffies();
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| 230 | }
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| 231 |
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| 232 | /*
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| 233 | * Return a new random number.
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| 234 | * Here we use the Borland rand() function to supply a pseudo random
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| 235 | * number which we make truely random by combining it with our own
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| 236 | * seed which is randomized by truely random events.
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| 237 | * Thus the numbers will be truely random unless there have been no
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| 238 | * operator or network events in which case it will be pseudo random
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| 239 | * seeded by the real time clock.
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| 240 | */
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| 241 | u32_t
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| 242 | avRandom()
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| 243 | {
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| 244 | return ((((u32_t)rand() << 16) + rand()) + avRandomSeed);
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| 245 | }
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| 246 |
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| 247 | #endif /* MD5_SUPPORT */
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| 248 |
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| 249 | #endif /* PPP_SUPPORT */
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