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Embedded C project:18/12/2014
Dependencies: DS1307 TextLCD mbed
NetServices/lwip/netif/ppp/randm.c
- Committer:
- ninoderkinderen
- Date:
- 2014-12-18
- Revision:
- 0:8d87bc453349
File content as of revision 0:8d87bc453349:
/***************************************************************************** * 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" #include <string.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; /* LWIP_DEBUGF(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); /* LWIP_DEBUGF(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 */