/***************************************************************************** | |
* 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 */ | |