1 /*****************************************************************************
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2 * randm.c - Random number generator program file.
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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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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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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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25 ******************************************************************************
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28 * 03-01-01 Marc Boucher <marc@mbsi.ca>
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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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39 #include "pppdebug.h"
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42 #if MD5_SUPPORT>0 /* this module depends on MD5 */
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43 #define RANDPOOLSZ 16 /* Bytes stored in the pool of randomness. */
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45 /*****************************/
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46 /*** LOCAL DATA STRUCTURES ***/
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47 /*****************************/
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48 static char randPool[RANDPOOLSZ]; /* Pool of randomness. */
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49 static long randCount = 0; /* Pseudo-random incrementer */
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52 /***********************************/
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53 /*** PUBLIC FUNCTION DEFINITIONS ***/
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54 /***********************************/
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56 * Initialize the random number generator.
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58 * Since this is to be called on power up, we don't have much
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59 * system randomess to work with. Here all we use is the
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60 * real-time clock. We'll accumulate more randomness as soon
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61 * as things start happening.
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65 avChurnRand(NULL, 0);
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69 * Churn the randomness pool on a random event. Call this early and often
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70 * on random and semi-random system events to build randomness in time for
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71 * usage. For randomly timed events, pass a null pointer and a zero length
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72 * and this will use the system timer and other sources to add randomness.
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73 * If new random data is available, pass a pointer to that and it will be
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76 * Ref: Applied Cryptography 2nd Ed. by Bruce Schneier p. 427
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78 void avChurnRand(char *randData, u32_t randLen)
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82 /* ppp_trace(LOG_INFO, "churnRand: %u@%P\n", randLen, randData); */
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84 MD5Update(&md5, (u_char *)randPool, sizeof(randPool));
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86 MD5Update(&md5, (u_char *)randData, randLen);
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89 /* INCLUDE fields for any system sources of randomness */
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93 /* Load sysData fields here. */
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95 MD5Update(&md5, (u_char *)&sysData, sizeof(sysData));
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97 MD5Final((u_char *)randPool, &md5);
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98 /* ppp_trace(LOG_INFO, "churnRand: -> 0\n"); */
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102 * Use the random pool to generate random data. This degrades to pseudo
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103 * random when used faster than randomness is supplied using churnRand().
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104 * Note: It's important that there be sufficient randomness in randPool
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105 * before this is called for otherwise the range of the result may be
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106 * narrow enough to make a search feasible.
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108 * Ref: Applied Cryptography 2nd Ed. by Bruce Schneier p. 427
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110 * XXX Why does he not just call churnRand() for each block? Probably
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111 * so that you don't ever publish the seed which could possibly help
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112 * predict future values.
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113 * XXX Why don't we preserve md5 between blocks and just update it with
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114 * randCount each time? Probably there is a weakness but I wish that
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115 * it was documented.
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117 void avGenRand(char *buf, u32_t bufLen)
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123 while (bufLen > 0) {
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124 n = LWIP_MIN(bufLen, RANDPOOLSZ);
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126 MD5Update(&md5, (u_char *)randPool, sizeof(randPool));
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127 MD5Update(&md5, (u_char *)&randCount, sizeof(randCount));
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128 MD5Final(tmp, &md5);
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130 memcpy(buf, tmp, n);
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137 * Return a new random number.
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143 avGenRand((char *)&newRand, sizeof(newRand));
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148 #else /* MD5_SUPPORT */
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151 /*****************************/
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152 /*** LOCAL DATA STRUCTURES ***/
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153 /*****************************/
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154 static int avRandomized = 0; /* Set when truely randomized. */
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155 static u32_t avRandomSeed = 0; /* Seed used for random number generation. */
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158 /***********************************/
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159 /*** PUBLIC FUNCTION DEFINITIONS ***/
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160 /***********************************/
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162 * Initialize the random number generator.
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164 * Here we attempt to compute a random number seed but even if
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165 * it isn't random, we'll randomize it later.
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167 * The current method uses the fields from the real time clock,
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168 * the idle process counter, the millisecond counter, and the
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169 * hardware timer tick counter. When this is invoked
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170 * in startup(), then the idle counter and timer values may
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171 * repeat after each boot and the real time clock may not be
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172 * operational. Thus we call it again on the first random
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175 void avRandomInit()
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178 /* Get a pointer into the last 4 bytes of clockBuf. */
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179 u32_t *lptr1 = (u32_t *)((char *)&clockBuf[3]);
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182 * Initialize our seed using the real-time clock, the idle
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183 * counter, the millisecond timer, and the hardware timer
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184 * tick counter. The real-time clock and the hardware
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185 * tick counter are the best sources of randomness but
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186 * since the tick counter is only 16 bit (and truncated
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187 * at that), the idle counter and millisecond timer
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188 * (which may be small values) are added to help
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189 * randomize the lower 16 bits of the seed.
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192 avRandomSeed += *(u32_t *)clockBuf + *lptr1 + OSIdleCtr
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193 + ppp_mtime() + ((u32_t)TM1 << 16) + TM1;
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195 avRandomSeed += sys_jiffies(); /* XXX */
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198 /* Initialize the Borland random number generator. */
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199 srand((unsigned)avRandomSeed);
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203 * Randomize our random seed value. Here we use the fact that
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204 * this function is called at *truely random* times by the polling
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205 * and network functions. Here we only get 16 bits of new random
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206 * value but we use the previous value to randomize the other 16
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209 void avRandomize(void)
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211 static u32_t last_jiffies;
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213 if (!avRandomized) {
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216 /* The initialization function also updates the seed. */
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218 /* avRandomSeed += (avRandomSeed << 16) + TM1; */
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219 avRandomSeed += (sys_jiffies() - last_jiffies); /* XXX */
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221 last_jiffies = sys_jiffies();
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225 * Return a new random number.
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226 * Here we use the Borland rand() function to supply a pseudo random
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227 * number which we make truely random by combining it with our own
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228 * seed which is randomized by truely random events.
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229 * Thus the numbers will be truely random unless there have been no
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230 * operator or network events in which case it will be pseudo random
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231 * seeded by the real time clock.
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235 return ((((u32_t)rand() << 16) + rand()) + avRandomSeed);
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240 #endif /* MD5_SUPPORT */
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241 #endif /* PPP_SUPPORT */
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