FreeRTOS/Common/ethernet/lwIP/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 "ppp.h"
  35 #if PPP_SUPPORT > 0
  36 #include "md5.h"
  37 #include "randm.h"
  38
  39 #include "pppdebug.h"
  40
  41
  42 #if MD5_SUPPORT>0   /* this module depends on MD5 */
  43 #define RANDPOOLSZ 16   /* Bytes stored in the pool of randomness. */
  44
  45 /*****************************/
  46 /*** LOCAL DATA STRUCTURES ***/
  47 /*****************************/
  48 static char randPool[RANDPOOLSZ];   /* Pool of randomness. */
  49 static long randCount = 0;      /* Pseudo-random incrementer */
  50
  51
  52 /***********************************/
  53 /*** PUBLIC FUNCTION DEFINITIONS ***/
  54 /***********************************/
  55 /*
  56  * Initialize the random number generator.
  57  *
  58  * Since this is to be called on power up, we don't have much
  59  *  system randomess to work with.  Here all we use is the
  60  *  real-time clock.  We'll accumulate more randomness as soon
  61  *  as things start happening.
  62  */
  63 void avRandomInit()
  64 {
  65     avChurnRand(NULL, 0);
  66 }
  67
  68 /*
  69  * Churn the randomness pool on a random event.  Call this early and often
  70  *  on random and semi-random system events to build randomness in time for
  71  *  usage.  For randomly timed events, pass a null pointer and a zero length
  72  *  and this will use the system timer and other sources to add randomness.
  73  *  If new random data is available, pass a pointer to that and it will be
  74  *  included.
  75  *
  76  * Ref: Applied Cryptography 2nd Ed. by Bruce Schneier p. 427
  77  */
  78 void avChurnRand(char *randData, u32_t randLen)
  79 {
  80     MD5_CTX md5;
  81
  82 /*  ppp_trace(LOG_INFO, "churnRand: %u@%P\n", randLen, randData); */
  83     MD5Init(&md5);
  84     MD5Update(&md5, (u_char *)randPool, sizeof(randPool));
  85     if (randData)
  86         MD5Update(&md5, (u_char *)randData, randLen);
  87     else {
  88         struct {
  89             /* INCLUDE fields for any system sources of randomness */
  90             char foobar;
  91         } sysData;
  92
  93         /* Load sysData fields here. */
  94         ;
  95         MD5Update(&md5, (u_char *)&sysData, sizeof(sysData));
  96     }
  97     MD5Final((u_char *)randPool, &md5);
  98 /*  ppp_trace(LOG_INFO, "churnRand: -> 0\n"); */
  99 }
 100
 101 /*
 102  * Use the random pool to generate random data.  This degrades to pseudo
 103  *  random when used faster than randomness is supplied using churnRand().
 104  * Note: It's important that there be sufficient randomness in randPool
 105  *  before this is called for otherwise the range of the result may be
 106  *  narrow enough to make a search feasible.
 107  *
 108  * Ref: Applied Cryptography 2nd Ed. by Bruce Schneier p. 427
 109  *
 110  * XXX Why does he not just call churnRand() for each block?  Probably
 111  *  so that you don't ever publish the seed which could possibly help
 112  *  predict future values.
 113  * XXX Why don't we preserve md5 between blocks and just update it with
 114  *  randCount each time?  Probably there is a weakness but I wish that
 115  *  it was documented.
 116  */
 117 void avGenRand(char *buf, u32_t bufLen)
 118 {
 119     MD5_CTX md5;
 120     u_char tmp[16];
 121     u32_t n;
 122
 123     while (bufLen > 0) {
 124         n = LWIP_MIN(bufLen, RANDPOOLSZ);
 125         MD5Init(&md5);
 126         MD5Update(&md5, (u_char *)randPool, sizeof(randPool));
 127         MD5Update(&md5, (u_char *)&randCount, sizeof(randCount));
 128         MD5Final(tmp, &md5);
 129         randCount++;
 130         memcpy(buf, tmp, n);
 131         buf += n;
 132         bufLen -= n;
 133     }
 134 }
 135
 136 /*
 137  * Return a new random number.
 138  */
 139 u32_t avRandom()
 140 {
 141     u32_t newRand;
 142
 143     avGenRand((char *)&newRand, sizeof(newRand));
 144
 145     return newRand;
 146 }
 147
 148 #else /* MD5_SUPPORT */
 149
 150
 151 /*****************************/
 152 /*** LOCAL DATA STRUCTURES ***/
 153 /*****************************/
 154 static int  avRandomized = 0;       /* Set when truely randomized. */
 155 static u32_t avRandomSeed = 0;      /* Seed used for random number generation. */
 156
 157
 158 /***********************************/
 159 /*** PUBLIC FUNCTION DEFINITIONS ***/
 160 /***********************************/
 161 /*
 162  * Initialize the random number generator.
 163  *
 164  * Here we attempt to compute a random number seed but even if
 165  * it isn't random, we'll randomize it later.
 166  *
 167  * The current method uses the fields from the real time clock,
 168  * the idle process counter, the millisecond counter, and the
 169  * hardware timer tick counter.  When this is invoked
 170  * in startup(), then the idle counter and timer values may
 171  * repeat after each boot and the real time clock may not be
 172  * operational.  Thus we call it again on the first random
 173  * event.
 174  */
 175 void avRandomInit()
 176 {
 177 #if 0
 178     /* Get a pointer into the last 4 bytes of clockBuf. */
 179     u32_t *lptr1 = (u32_t *)((char *)&clockBuf[3]);
 180
 181     /*
 182      * Initialize our seed using the real-time clock, the idle
 183      * counter, the millisecond timer, and the hardware timer
 184      * tick counter.  The real-time clock and the hardware
 185      * tick counter are the best sources of randomness but
 186      * since the tick counter is only 16 bit (and truncated
 187      * at that), the idle counter and millisecond timer
 188      * (which may be small values) are added to help
 189      * randomize the lower 16 bits of the seed.
 190      */
 191     readClk();
 192     avRandomSeed += *(u32_t *)clockBuf + *lptr1 + OSIdleCtr
 193              + ppp_mtime() + ((u32_t)TM1 << 16) + TM1;
 194 #else
 195     avRandomSeed += sys_jiffies(); /* XXX */
 196 #endif
 197
 198     /* Initialize the Borland random number generator. */
 199     srand((unsigned)avRandomSeed);
 200 }
 201
 202 /*
 203  * Randomize our random seed value.  Here we use the fact that
 204  * this function is called at *truely random* times by the polling
 205  * and network functions.  Here we only get 16 bits of new random
 206  * value but we use the previous value to randomize the other 16
 207  * bits.
 208  */
 209 void avRandomize(void)
 210 {
 211     static u32_t last_jiffies;
 212
 213     if (!avRandomized) {
 214         avRandomized = !0;
 215         avRandomInit();
 216         /* The initialization function also updates the seed. */
 217     } else {
 218 /*        avRandomSeed += (avRandomSeed << 16) + TM1; */
 219         avRandomSeed += (sys_jiffies() - last_jiffies); /* XXX */
 220     }
 221     last_jiffies = sys_jiffies();
 222 }
 223
 224 /*
 225  * Return a new random number.
 226  * Here we use the Borland rand() function to supply a pseudo random
 227  * number which we make truely random by combining it with our own
 228  * seed which is randomized by truely random events.
 229  * Thus the numbers will be truely random unless there have been no
 230  * operator or network events in which case it will be pseudo random
 231  * seeded by the real time clock.
 232  */
 233 u32_t avRandom()
 234 {
 235     return ((((u32_t)rand() << 16) + rand()) + avRandomSeed);
 236 }
 237
 238
 239
 240 #endif /* MD5_SUPPORT */
 241 #endif /* PPP_SUPPORT */
 242