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/*****************************************************************************
* 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 "lwip/opt.h"
#if PPP_SUPPORT /* don't build if not configured for use in lwipopts.h */
#include "md5.h"
#include "randm.h"
#include "ppp.h"
#include "pppdebug.h"
#if MD5_SUPPORT /* 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 */
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