FreeRTOS/Common/ethernet/lwIP_130/src/netif/ppp/randm.c

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