Adam Green / Mbed 2 deprecated WeatherStation

Web server based weather station using Sparkfun Weather Meters.

Dependencies:   FatFileSystem mbed WeatherMeters SDFileSystem

NetStack/lwip/netif/ppp/randm.c@1:c7958aa34fa1, 2012-02-25 (annotated)

Committer:
AdamGreen
Date:
Sat Feb 25 03:28:05 2012 +0000
Revision:
1:c7958aa34fa1
Parent:
0:616601bde9fb 
Use published libraries where possible.

Who changed what in which revision?

UserRevisionLine numberNew contents of line
AdamGreen 0:616601bde9fb 1 /*****************************************************************************
AdamGreen 0:616601bde9fb 2 * randm.c - Random number generator program file.
AdamGreen 0:616601bde9fb 3 *
AdamGreen 0:616601bde9fb 4 * Copyright (c) 2003 by Marc Boucher, Services Informatiques (MBSI) inc.
AdamGreen 0:616601bde9fb 5 * Copyright (c) 1998 by Global Election Systems Inc.
AdamGreen 0:616601bde9fb 6 *
AdamGreen 0:616601bde9fb 7 * The authors hereby grant permission to use, copy, modify, distribute,
AdamGreen 0:616601bde9fb 8 * and license this software and its documentation for any purpose, provided
AdamGreen 0:616601bde9fb 9 * that existing copyright notices are retained in all copies and that this
AdamGreen 0:616601bde9fb 10 * notice and the following disclaimer are included verbatim in any
AdamGreen 0:616601bde9fb 11 * distributions. No written agreement, license, or royalty fee is required
AdamGreen 0:616601bde9fb 12 * for any of the authorized uses.
AdamGreen 0:616601bde9fb 13 *
AdamGreen 0:616601bde9fb 14 * THIS SOFTWARE IS PROVIDED BY THE CONTRIBUTORS *AS IS* AND ANY EXPRESS OR
AdamGreen 0:616601bde9fb 15 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
AdamGreen 0:616601bde9fb 16 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
AdamGreen 0:616601bde9fb 17 * IN NO EVENT SHALL THE CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
AdamGreen 0:616601bde9fb 18 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
AdamGreen 0:616601bde9fb 19 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
AdamGreen 0:616601bde9fb 20 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
AdamGreen 0:616601bde9fb 21 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
AdamGreen 0:616601bde9fb 22 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
AdamGreen 0:616601bde9fb 23 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
AdamGreen 0:616601bde9fb 24 *
AdamGreen 0:616601bde9fb 25 ******************************************************************************
AdamGreen 0:616601bde9fb 26 * REVISION HISTORY
AdamGreen 0:616601bde9fb 27 *
AdamGreen 0:616601bde9fb 28 * 03-01-01 Marc Boucher <marc@mbsi.ca>
AdamGreen 0:616601bde9fb 29 * Ported to lwIP.
AdamGreen 0:616601bde9fb 30 * 98-06-03 Guy Lancaster <lancasterg@acm.org>, Global Election Systems Inc.
AdamGreen 0:616601bde9fb 31 * Extracted from avos.
AdamGreen 0:616601bde9fb 32 *****************************************************************************/
AdamGreen 0:616601bde9fb 33
AdamGreen 0:616601bde9fb 34 #include "lwip/opt.h"
AdamGreen 0:616601bde9fb 35
AdamGreen 0:616601bde9fb 36 #if PPP_SUPPORT /* don't build if not configured for use in lwipopts.h */
AdamGreen 0:616601bde9fb 37
AdamGreen 0:616601bde9fb 38 #include "md5.h"
AdamGreen 0:616601bde9fb 39 #include "randm.h"
AdamGreen 0:616601bde9fb 40
AdamGreen 0:616601bde9fb 41 #include "ppp.h"
AdamGreen 0:616601bde9fb 42 #include "pppdebug.h"
AdamGreen 0:616601bde9fb 43
AdamGreen 0:616601bde9fb 44 #include <string.h>
AdamGreen 0:616601bde9fb 45
AdamGreen 0:616601bde9fb 46 #if MD5_SUPPORT /* this module depends on MD5 */
AdamGreen 0:616601bde9fb 47 #define RANDPOOLSZ 16 /* Bytes stored in the pool of randomness. */
AdamGreen 0:616601bde9fb 48
AdamGreen 0:616601bde9fb 49 /*****************************/
AdamGreen 0:616601bde9fb 50 /*** LOCAL DATA STRUCTURES ***/
AdamGreen 0:616601bde9fb 51 /*****************************/
AdamGreen 0:616601bde9fb 52 static char randPool[RANDPOOLSZ]; /* Pool of randomness. */
AdamGreen 0:616601bde9fb 53 static long randCount = 0; /* Pseudo-random incrementer */
AdamGreen 0:616601bde9fb 54
AdamGreen 0:616601bde9fb 55
AdamGreen 0:616601bde9fb 56 /***********************************/
AdamGreen 0:616601bde9fb 57 /*** PUBLIC FUNCTION DEFINITIONS ***/
AdamGreen 0:616601bde9fb 58 /***********************************/
AdamGreen 0:616601bde9fb 59 /*
AdamGreen 0:616601bde9fb 60 * Initialize the random number generator.
AdamGreen 0:616601bde9fb 61 *
AdamGreen 0:616601bde9fb 62 * Since this is to be called on power up, we don't have much
AdamGreen 0:616601bde9fb 63 * system randomess to work with. Here all we use is the
AdamGreen 0:616601bde9fb 64 * real-time clock. We'll accumulate more randomness as soon
AdamGreen 0:616601bde9fb 65 * as things start happening.
AdamGreen 0:616601bde9fb 66 */
AdamGreen 0:616601bde9fb 67 void
AdamGreen 0:616601bde9fb 68 avRandomInit()
AdamGreen 0:616601bde9fb 69 {
AdamGreen 0:616601bde9fb 70 avChurnRand(NULL, 0);
AdamGreen 0:616601bde9fb 71 }
AdamGreen 0:616601bde9fb 72
AdamGreen 0:616601bde9fb 73 /*
AdamGreen 0:616601bde9fb 74 * Churn the randomness pool on a random event. Call this early and often
AdamGreen 0:616601bde9fb 75 * on random and semi-random system events to build randomness in time for
AdamGreen 0:616601bde9fb 76 * usage. For randomly timed events, pass a null pointer and a zero length
AdamGreen 0:616601bde9fb 77 * and this will use the system timer and other sources to add randomness.
AdamGreen 0:616601bde9fb 78 * If new random data is available, pass a pointer to that and it will be
AdamGreen 0:616601bde9fb 79 * included.
AdamGreen 0:616601bde9fb 80 *
AdamGreen 0:616601bde9fb 81 * Ref: Applied Cryptography 2nd Ed. by Bruce Schneier p. 427
AdamGreen 0:616601bde9fb 82 */
AdamGreen 0:616601bde9fb 83 void
AdamGreen 0:616601bde9fb 84 avChurnRand(char *randData, u32_t randLen)
AdamGreen 0:616601bde9fb 85 {
AdamGreen 0:616601bde9fb 86 MD5_CTX md5;
AdamGreen 0:616601bde9fb 87
AdamGreen 0:616601bde9fb 88 /* LWIP_DEBUGF(LOG_INFO, ("churnRand: %u@%P\n", randLen, randData)); */
AdamGreen 0:616601bde9fb 89 MD5Init(&md5);
AdamGreen 0:616601bde9fb 90 MD5Update(&md5, (u_char *)randPool, sizeof(randPool));
AdamGreen 0:616601bde9fb 91 if (randData) {
AdamGreen 0:616601bde9fb 92 MD5Update(&md5, (u_char *)randData, randLen);
AdamGreen 0:616601bde9fb 93 } else {
AdamGreen 0:616601bde9fb 94 struct {
AdamGreen 0:616601bde9fb 95 /* INCLUDE fields for any system sources of randomness */
AdamGreen 0:616601bde9fb 96 char foobar;
AdamGreen 0:616601bde9fb 97 } sysData;
AdamGreen 0:616601bde9fb 98
AdamGreen 0:616601bde9fb 99 /* Load sysData fields here. */
AdamGreen 0:616601bde9fb 100 MD5Update(&md5, (u_char *)&sysData, sizeof(sysData));
AdamGreen 0:616601bde9fb 101 }
AdamGreen 0:616601bde9fb 102 MD5Final((u_char *)randPool, &md5);
AdamGreen 0:616601bde9fb 103 /* LWIP_DEBUGF(LOG_INFO, ("churnRand: -> 0\n")); */
AdamGreen 0:616601bde9fb 104 }
AdamGreen 0:616601bde9fb 105
AdamGreen 0:616601bde9fb 106 /*
AdamGreen 0:616601bde9fb 107 * Use the random pool to generate random data. This degrades to pseudo
AdamGreen 0:616601bde9fb 108 * random when used faster than randomness is supplied using churnRand().
AdamGreen 0:616601bde9fb 109 * Note: It's important that there be sufficient randomness in randPool
AdamGreen 0:616601bde9fb 110 * before this is called for otherwise the range of the result may be
AdamGreen 0:616601bde9fb 111 * narrow enough to make a search feasible.
AdamGreen 0:616601bde9fb 112 *
AdamGreen 0:616601bde9fb 113 * Ref: Applied Cryptography 2nd Ed. by Bruce Schneier p. 427
AdamGreen 0:616601bde9fb 114 *
AdamGreen 0:616601bde9fb 115 * XXX Why does he not just call churnRand() for each block? Probably
AdamGreen 0:616601bde9fb 116 * so that you don't ever publish the seed which could possibly help
AdamGreen 0:616601bde9fb 117 * predict future values.
AdamGreen 0:616601bde9fb 118 * XXX Why don't we preserve md5 between blocks and just update it with
AdamGreen 0:616601bde9fb 119 * randCount each time? Probably there is a weakness but I wish that
AdamGreen 0:616601bde9fb 120 * it was documented.
AdamGreen 0:616601bde9fb 121 */
AdamGreen 0:616601bde9fb 122 void
AdamGreen 0:616601bde9fb 123 avGenRand(char *buf, u32_t bufLen)
AdamGreen 0:616601bde9fb 124 {
AdamGreen 0:616601bde9fb 125 MD5_CTX md5;
AdamGreen 0:616601bde9fb 126 u_char tmp[16];
AdamGreen 0:616601bde9fb 127 u32_t n;
AdamGreen 0:616601bde9fb 128
AdamGreen 0:616601bde9fb 129 while (bufLen > 0) {
AdamGreen 0:616601bde9fb 130 n = LWIP_MIN(bufLen, RANDPOOLSZ);
AdamGreen 0:616601bde9fb 131 MD5Init(&md5);
AdamGreen 0:616601bde9fb 132 MD5Update(&md5, (u_char *)randPool, sizeof(randPool));
AdamGreen 0:616601bde9fb 133 MD5Update(&md5, (u_char *)&randCount, sizeof(randCount));
AdamGreen 0:616601bde9fb 134 MD5Final(tmp, &md5);
AdamGreen 0:616601bde9fb 135 randCount++;
AdamGreen 0:616601bde9fb 136 MEMCPY(buf, tmp, n);
AdamGreen 0:616601bde9fb 137 buf += n;
AdamGreen 0:616601bde9fb 138 bufLen -= n;
AdamGreen 0:616601bde9fb 139 }
AdamGreen 0:616601bde9fb 140 }
AdamGreen 0:616601bde9fb 141
AdamGreen 0:616601bde9fb 142 /*
AdamGreen 0:616601bde9fb 143 * Return a new random number.
AdamGreen 0:616601bde9fb 144 */
AdamGreen 0:616601bde9fb 145 u32_t
AdamGreen 0:616601bde9fb 146 avRandom()
AdamGreen 0:616601bde9fb 147 {
AdamGreen 0:616601bde9fb 148 u32_t newRand;
AdamGreen 0:616601bde9fb 149
AdamGreen 0:616601bde9fb 150 avGenRand((char *)&newRand, sizeof(newRand));
AdamGreen 0:616601bde9fb 151
AdamGreen 0:616601bde9fb 152 return newRand;
AdamGreen 0:616601bde9fb 153 }
AdamGreen 0:616601bde9fb 154
AdamGreen 0:616601bde9fb 155 #else /* MD5_SUPPORT */
AdamGreen 0:616601bde9fb 156
AdamGreen 0:616601bde9fb 157 /*****************************/
AdamGreen 0:616601bde9fb 158 /*** LOCAL DATA STRUCTURES ***/
AdamGreen 0:616601bde9fb 159 /*****************************/
AdamGreen 0:616601bde9fb 160 static int avRandomized = 0; /* Set when truely randomized. */
AdamGreen 0:616601bde9fb 161 static u32_t avRandomSeed = 0; /* Seed used for random number generation. */
AdamGreen 0:616601bde9fb 162
AdamGreen 0:616601bde9fb 163
AdamGreen 0:616601bde9fb 164 /***********************************/
AdamGreen 0:616601bde9fb 165 /*** PUBLIC FUNCTION DEFINITIONS ***/
AdamGreen 0:616601bde9fb 166 /***********************************/
AdamGreen 0:616601bde9fb 167 /*
AdamGreen 0:616601bde9fb 168 * Initialize the random number generator.
AdamGreen 0:616601bde9fb 169 *
AdamGreen 0:616601bde9fb 170 * Here we attempt to compute a random number seed but even if
AdamGreen 0:616601bde9fb 171 * it isn't random, we'll randomize it later.
AdamGreen 0:616601bde9fb 172 *
AdamGreen 0:616601bde9fb 173 * The current method uses the fields from the real time clock,
AdamGreen 0:616601bde9fb 174 * the idle process counter, the millisecond counter, and the
AdamGreen 0:616601bde9fb 175 * hardware timer tick counter. When this is invoked
AdamGreen 0:616601bde9fb 176 * in startup(), then the idle counter and timer values may
AdamGreen 0:616601bde9fb 177 * repeat after each boot and the real time clock may not be
AdamGreen 0:616601bde9fb 178 * operational. Thus we call it again on the first random
AdamGreen 0:616601bde9fb 179 * event.
AdamGreen 0:616601bde9fb 180 */
AdamGreen 0:616601bde9fb 181 void
AdamGreen 0:616601bde9fb 182 avRandomInit()
AdamGreen 0:616601bde9fb 183 {
AdamGreen 0:616601bde9fb 184 #if 0
AdamGreen 0:616601bde9fb 185 /* Get a pointer into the last 4 bytes of clockBuf. */
AdamGreen 0:616601bde9fb 186 u32_t *lptr1 = (u32_t *)((char *)&clockBuf[3]);
AdamGreen 0:616601bde9fb 187
AdamGreen 0:616601bde9fb 188 /*
AdamGreen 0:616601bde9fb 189 * Initialize our seed using the real-time clock, the idle
AdamGreen 0:616601bde9fb 190 * counter, the millisecond timer, and the hardware timer
AdamGreen 0:616601bde9fb 191 * tick counter. The real-time clock and the hardware
AdamGreen 0:616601bde9fb 192 * tick counter are the best sources of randomness but
AdamGreen 0:616601bde9fb 193 * since the tick counter is only 16 bit (and truncated
AdamGreen 0:616601bde9fb 194 * at that), the idle counter and millisecond timer
AdamGreen 0:616601bde9fb 195 * (which may be small values) are added to help
AdamGreen 0:616601bde9fb 196 * randomize the lower 16 bits of the seed.
AdamGreen 0:616601bde9fb 197 */
AdamGreen 0:616601bde9fb 198 readClk();
AdamGreen 0:616601bde9fb 199 avRandomSeed += *(u32_t *)clockBuf + *lptr1 + OSIdleCtr
AdamGreen 0:616601bde9fb 200 + ppp_mtime() + ((u32_t)TM1 << 16) + TM1;
AdamGreen 0:616601bde9fb 201 #else
AdamGreen 0:616601bde9fb 202 avRandomSeed += sys_jiffies(); /* XXX */
AdamGreen 0:616601bde9fb 203 #endif
AdamGreen 0:616601bde9fb 204
AdamGreen 0:616601bde9fb 205 /* Initialize the Borland random number generator. */
AdamGreen 0:616601bde9fb 206 srand((unsigned)avRandomSeed);
AdamGreen 0:616601bde9fb 207 }
AdamGreen 0:616601bde9fb 208
AdamGreen 0:616601bde9fb 209 /*
AdamGreen 0:616601bde9fb 210 * Randomize our random seed value. Here we use the fact that
AdamGreen 0:616601bde9fb 211 * this function is called at *truely random* times by the polling
AdamGreen 0:616601bde9fb 212 * and network functions. Here we only get 16 bits of new random
AdamGreen 0:616601bde9fb 213 * value but we use the previous value to randomize the other 16
AdamGreen 0:616601bde9fb 214 * bits.
AdamGreen 0:616601bde9fb 215 */
AdamGreen 0:616601bde9fb 216 void
AdamGreen 0:616601bde9fb 217 avRandomize(void)
AdamGreen 0:616601bde9fb 218 {
AdamGreen 0:616601bde9fb 219 static u32_t last_jiffies;
AdamGreen 0:616601bde9fb 220
AdamGreen 0:616601bde9fb 221 if (!avRandomized) {
AdamGreen 0:616601bde9fb 222 avRandomized = !0;
AdamGreen 0:616601bde9fb 223 avRandomInit();
AdamGreen 0:616601bde9fb 224 /* The initialization function also updates the seed. */
AdamGreen 0:616601bde9fb 225 } else {
AdamGreen 0:616601bde9fb 226 /* avRandomSeed += (avRandomSeed << 16) + TM1; */
AdamGreen 0:616601bde9fb 227 avRandomSeed += (sys_jiffies() - last_jiffies); /* XXX */
AdamGreen 0:616601bde9fb 228 }
AdamGreen 0:616601bde9fb 229 last_jiffies = sys_jiffies();
AdamGreen 0:616601bde9fb 230 }
AdamGreen 0:616601bde9fb 231
AdamGreen 0:616601bde9fb 232 /*
AdamGreen 0:616601bde9fb 233 * Return a new random number.
AdamGreen 0:616601bde9fb 234 * Here we use the Borland rand() function to supply a pseudo random
AdamGreen 0:616601bde9fb 235 * number which we make truely random by combining it with our own
AdamGreen 0:616601bde9fb 236 * seed which is randomized by truely random events.
AdamGreen 0:616601bde9fb 237 * Thus the numbers will be truely random unless there have been no
AdamGreen 0:616601bde9fb 238 * operator or network events in which case it will be pseudo random
AdamGreen 0:616601bde9fb 239 * seeded by the real time clock.
AdamGreen 0:616601bde9fb 240 */
AdamGreen 0:616601bde9fb 241 u32_t
AdamGreen 0:616601bde9fb 242 avRandom()
AdamGreen 0:616601bde9fb 243 {
AdamGreen 0:616601bde9fb 244 return ((((u32_t)rand() << 16) + rand()) + avRandomSeed);
AdamGreen 0:616601bde9fb 245 }
AdamGreen 0:616601bde9fb 246
AdamGreen 0:616601bde9fb 247 #endif /* MD5_SUPPORT */
AdamGreen 0:616601bde9fb 248
AdamGreen 0:616601bde9fb 249 #endif /* PPP_SUPPORT */