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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