/****************************************************************************** randm.c - Random number generator program file.** Copyright (c) 2003 by Marc Boucher, Services Informatiques (MBSI) inc.* Copyright (c) 1998 by Global Election Systems Inc.** The authors hereby grant permission to use, copy, modify, distribute,* and license this software and its documentation for any purpose, provided* that existing copyright notices are retained in all copies and that this* notice and the following disclaimer are included verbatim in any * distributions. No written agreement, license, or royalty fee is required* for any of the authorized uses.** THIS SOFTWARE IS PROVIDED BY THE CONTRIBUTORS *AS IS* AND ANY EXPRESS OR* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. * IN NO EVENT SHALL THE CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.******************************************************************************** REVISION HISTORY** 03-01-01 Marc Boucher <marc@mbsi.ca>*   Ported to lwIP.* 98-06-03 Guy Lancaster <lancasterg@acm.org>, Global Election Systems Inc.*   Extracted from avos.*****************************************************************************/#include "ppp.h"#if PPP_SUPPORT > 0#include "md5.h"#include "randm.h"#include "pppdebug.h"#if MD5_SUPPORT>0   /* this module depends on MD5 */#define RANDPOOLSZ 16   /* Bytes stored in the pool of randomness. *//*****************************//*** LOCAL DATA STRUCTURES ***//*****************************/static char randPool[RANDPOOLSZ];   /* Pool of randomness. */static long randCount = 0;      /* Pseudo-random incrementer *//***********************************//*** PUBLIC FUNCTION DEFINITIONS ***//***********************************//* * Initialize the random number generator. * * Since this is to be called on power up, we don't have much *  system randomess to work with.  Here all we use is the *  real-time clock.  We'll accumulate more randomness as soon *  as things start happening. */void avRandomInit(){    avChurnRand(NULL, 0);}/* * Churn the randomness pool on a random event.  Call this early and often *  on random and semi-random system events to build randomness in time for *  usage.  For randomly timed events, pass a null pointer and a zero length *  and this will use the system timer and other sources to add randomness. *  If new random data is available, pass a pointer to that and it will be *  included. * * Ref: Applied Cryptography 2nd Ed. by Bruce Schneier p. 427 */void avChurnRand(char *randData, u32_t randLen){    MD5_CTX md5;/*  ppp_trace(LOG_INFO, "churnRand: %u@%P\n", randLen, randData); */    MD5Init(&md5);    MD5Update(&md5, (u_char *)randPool, sizeof(randPool));    if (randData)        MD5Update(&md5, (u_char *)randData, randLen);    else {        struct {            /* INCLUDE fields for any system sources of randomness */            char foobar;        } sysData;        /* Load sysData fields here. */        ;        MD5Update(&md5, (u_char *)&sysData, sizeof(sysData));    }    MD5Final((u_char *)randPool, &md5);/*  ppp_trace(LOG_INFO, "churnRand: -> 0\n"); */}/* * Use the random pool to generate random data.  This degrades to pseudo *  random when used faster than randomness is supplied using churnRand(). * Note: It's important that there be sufficient randomness in randPool *  before this is called for otherwise the range of the result may be *  narrow enough to make a search feasible. * * Ref: Applied Cryptography 2nd Ed. by Bruce Schneier p. 427 * * XXX Why does he not just call churnRand() for each block?  Probably *  so that you don't ever publish the seed which could possibly help *  predict future values. * XXX Why don't we preserve md5 between blocks and just update it with *  randCount each time?  Probably there is a weakness but I wish that *  it was documented. */void avGenRand(char *buf, u32_t bufLen){    MD5_CTX md5;    u_char tmp[16];    u32_t n;    while (bufLen > 0) {        n = LWIP_MIN(bufLen, RANDPOOLSZ);        MD5Init(&md5);        MD5Update(&md5, (u_char *)randPool, sizeof(randPool));        MD5Update(&md5, (u_char *)&randCount, sizeof(randCount));        MD5Final(tmp, &md5);        randCount++;        memcpy(buf, tmp, n);        buf += n;        bufLen -= n;    }}/* * Return a new random number. */u32_t avRandom(){    u32_t newRand;    avGenRand((char *)&newRand, sizeof(newRand));    return newRand;}#else /* MD5_SUPPORT *//*****************************//*** LOCAL DATA STRUCTURES ***//*****************************/static int  avRandomized = 0;       /* Set when truely randomized. */static u32_t avRandomSeed = 0;      /* Seed used for random number generation. *//***********************************//*** PUBLIC FUNCTION DEFINITIONS ***//***********************************//* * Initialize the random number generator. * * Here we attempt to compute a random number seed but even if * it isn't random, we'll randomize it later. * * The current method uses the fields from the real time clock, * the idle process counter, the millisecond counter, and the * hardware timer tick counter.  When this is invoked * in startup(), then the idle counter and timer values may * repeat after each boot and the real time clock may not be * operational.  Thus we call it again on the first random * event. */void avRandomInit(){#if 0    /* Get a pointer into the last 4 bytes of clockBuf. */    u32_t *lptr1 = (u32_t *)((char *)&clockBuf[3]);    /*     * Initialize our seed using the real-time clock, the idle     * counter, the millisecond timer, and the hardware timer     * tick counter.  The real-time clock and the hardware     * tick counter are the best sources of randomness but     * since the tick counter is only 16 bit (and truncated     * at that), the idle counter and millisecond timer     * (which may be small values) are added to help     * randomize the lower 16 bits of the seed.     */    readClk();    avRandomSeed += *(u32_t *)clockBuf + *lptr1 + OSIdleCtr             + ppp_mtime() + ((u32_t)TM1 << 16) + TM1;#else    avRandomSeed += sys_jiffies(); /* XXX */#endif            /* Initialize the Borland random number generator. */    srand((unsigned)avRandomSeed);}/* * Randomize our random seed value.  Here we use the fact that * this function is called at *truely random* times by the polling * and network functions.  Here we only get 16 bits of new random * value but we use the previous value to randomize the other 16 * bits. */void avRandomize(void){    static u32_t last_jiffies;    if (!avRandomized) {        avRandomized = !0;        avRandomInit();        /* The initialization function also updates the seed. */    } else {/*        avRandomSeed += (avRandomSeed << 16) + TM1; */    	avRandomSeed += (sys_jiffies() - last_jiffies); /* XXX */    }    last_jiffies = sys_jiffies();}/* * Return a new random number. * Here we use the Borland rand() function to supply a pseudo random * number which we make truely random by combining it with our own * seed which is randomized by truely random events.  * Thus the numbers will be truely random unless there have been no * operator or network events in which case it will be pseudo random * seeded by the real time clock. */u32_t avRandom(){    return ((((u32_t)rand() << 16) + rand()) + avRandomSeed);}#endif /* MD5_SUPPORT */#endif /* PPP_SUPPORT */