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lwip/netif/ppp/randm.c@0:281d6ff68967, 2010-11-19 (annotated)

Committer:: hexley
Date:: Fri Nov 19 01:54:45 2010 +0000
Revision:: 0:281d6ff68967

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User	Revision	Line number	New contents of line
hexley	0:281d6ff68967	1	/*****************************************************************************
hexley	0:281d6ff68967	2	* randm.c - Random number generator program file.
hexley	0:281d6ff68967	3	*
hexley	0:281d6ff68967	4	* Copyright (c) 2003 by Marc Boucher, Services Informatiques (MBSI) inc.
hexley	0:281d6ff68967	5	* Copyright (c) 1998 by Global Election Systems Inc.
hexley	0:281d6ff68967	6	*
hexley	0:281d6ff68967	7	* The authors hereby grant permission to use, copy, modify, distribute,
hexley	0:281d6ff68967	8	* and license this software and its documentation for any purpose, provided
hexley	0:281d6ff68967	9	* that existing copyright notices are retained in all copies and that this
hexley	0:281d6ff68967	10	* notice and the following disclaimer are included verbatim in any
hexley	0:281d6ff68967	11	* distributions. No written agreement, license, or royalty fee is required
hexley	0:281d6ff68967	12	* for any of the authorized uses.
hexley	0:281d6ff68967	13	*
hexley	0:281d6ff68967	14	* THIS SOFTWARE IS PROVIDED BY THE CONTRIBUTORS AS IS AND ANY EXPRESS OR
hexley	0:281d6ff68967	15	* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
hexley	0:281d6ff68967	16	* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
hexley	0:281d6ff68967	17	* IN NO EVENT SHALL THE CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
hexley	0:281d6ff68967	18	* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
hexley	0:281d6ff68967	19	* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
hexley	0:281d6ff68967	20	* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
hexley	0:281d6ff68967	21	* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
hexley	0:281d6ff68967	22	* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
hexley	0:281d6ff68967	23	* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
hexley	0:281d6ff68967	24	*
hexley	0:281d6ff68967	25	******************************************************************************
hexley	0:281d6ff68967	26	* REVISION HISTORY
hexley	0:281d6ff68967	27	*
hexley	0:281d6ff68967	28	* 03-01-01 Marc Boucher <marc@mbsi.ca>
hexley	0:281d6ff68967	29	* Ported to lwIP.
hexley	0:281d6ff68967	30	* 98-06-03 Guy Lancaster <lancasterg@acm.org>, Global Election Systems Inc.
hexley	0:281d6ff68967	31	* Extracted from avos.
hexley	0:281d6ff68967	32	*****************************************************************************/
hexley	0:281d6ff68967	33
hexley	0:281d6ff68967	34	#include "lwip/opt.h"
hexley	0:281d6ff68967	35
hexley	0:281d6ff68967	36	#if PPP_SUPPORT /* don't build if not configured for use in lwipopts.h */
hexley	0:281d6ff68967	37
hexley	0:281d6ff68967	38	#include "md5.h"
hexley	0:281d6ff68967	39	#include "randm.h"
hexley	0:281d6ff68967	40
hexley	0:281d6ff68967	41	#include "ppp.h"
hexley	0:281d6ff68967	42	#include "pppdebug.h"
hexley	0:281d6ff68967	43
hexley	0:281d6ff68967	44	#include <string.h>
hexley	0:281d6ff68967	45
hexley	0:281d6ff68967	46	#if MD5_SUPPORT /* this module depends on MD5 */
hexley	0:281d6ff68967	47	#define RANDPOOLSZ 16 /* Bytes stored in the pool of randomness. */
hexley	0:281d6ff68967	48
hexley	0:281d6ff68967	49	/*****************************/
hexley	0:281d6ff68967	50	/* LOCAL DATA STRUCTURES */
hexley	0:281d6ff68967	51	/*****************************/
hexley	0:281d6ff68967	52	static char randPool[RANDPOOLSZ]; /* Pool of randomness. */
hexley	0:281d6ff68967	53	static long randCount = 0; /* Pseudo-random incrementer */
hexley	0:281d6ff68967	54
hexley	0:281d6ff68967	55
hexley	0:281d6ff68967	56	/***********************************/
hexley	0:281d6ff68967	57	/* PUBLIC FUNCTION DEFINITIONS */
hexley	0:281d6ff68967	58	/***********************************/
hexley	0:281d6ff68967	59	/*
hexley	0:281d6ff68967	60	* Initialize the random number generator.
hexley	0:281d6ff68967	61	*
hexley	0:281d6ff68967	62	* Since this is to be called on power up, we don't have much
hexley	0:281d6ff68967	63	* system randomess to work with. Here all we use is the
hexley	0:281d6ff68967	64	* real-time clock. We'll accumulate more randomness as soon
hexley	0:281d6ff68967	65	* as things start happening.
hexley	0:281d6ff68967	66	*/
hexley	0:281d6ff68967	67	void
hexley	0:281d6ff68967	68	avRandomInit()
hexley	0:281d6ff68967	69	{
hexley	0:281d6ff68967	70	avChurnRand(NULL, 0);
hexley	0:281d6ff68967	71	}
hexley	0:281d6ff68967	72
hexley	0:281d6ff68967	73	/*
hexley	0:281d6ff68967	74	* Churn the randomness pool on a random event. Call this early and often
hexley	0:281d6ff68967	75	* on random and semi-random system events to build randomness in time for
hexley	0:281d6ff68967	76	* usage. For randomly timed events, pass a null pointer and a zero length
hexley	0:281d6ff68967	77	* and this will use the system timer and other sources to add randomness.
hexley	0:281d6ff68967	78	* If new random data is available, pass a pointer to that and it will be
hexley	0:281d6ff68967	79	* included.
hexley	0:281d6ff68967	80	*
hexley	0:281d6ff68967	81	* Ref: Applied Cryptography 2nd Ed. by Bruce Schneier p. 427
hexley	0:281d6ff68967	82	*/
hexley	0:281d6ff68967	83	void
hexley	0:281d6ff68967	84	avChurnRand(char *randData, u32_t randLen)
hexley	0:281d6ff68967	85	{
hexley	0:281d6ff68967	86	MD5_CTX md5;
hexley	0:281d6ff68967	87
hexley	0:281d6ff68967	88	/* LWIP_DEBUGF(LOG_INFO, ("churnRand: %u@%P\n", randLen, randData)); */
hexley	0:281d6ff68967	89	MD5Init(&md5);
hexley	0:281d6ff68967	90	MD5Update(&md5, (u_char *)randPool, sizeof(randPool));
hexley	0:281d6ff68967	91	if (randData) {
hexley	0:281d6ff68967	92	MD5Update(&md5, (u_char *)randData, randLen);
hexley	0:281d6ff68967	93	} else {
hexley	0:281d6ff68967	94	struct {
hexley	0:281d6ff68967	95	/* INCLUDE fields for any system sources of randomness */
hexley	0:281d6ff68967	96	char foobar;
hexley	0:281d6ff68967	97	} sysData;
hexley	0:281d6ff68967	98
hexley	0:281d6ff68967	99	/* Load sysData fields here. */
hexley	0:281d6ff68967	100	MD5Update(&md5, (u_char *)&sysData, sizeof(sysData));
hexley	0:281d6ff68967	101	}
hexley	0:281d6ff68967	102	MD5Final((u_char *)randPool, &md5);
hexley	0:281d6ff68967	103	/* LWIP_DEBUGF(LOG_INFO, ("churnRand: -> 0\n")); */
hexley	0:281d6ff68967	104	}
hexley	0:281d6ff68967	105
hexley	0:281d6ff68967	106	/*
hexley	0:281d6ff68967	107	* Use the random pool to generate random data. This degrades to pseudo
hexley	0:281d6ff68967	108	* random when used faster than randomness is supplied using churnRand().
hexley	0:281d6ff68967	109	* Note: It's important that there be sufficient randomness in randPool
hexley	0:281d6ff68967	110	* before this is called for otherwise the range of the result may be
hexley	0:281d6ff68967	111	* narrow enough to make a search feasible.
hexley	0:281d6ff68967	112	*
hexley	0:281d6ff68967	113	* Ref: Applied Cryptography 2nd Ed. by Bruce Schneier p. 427
hexley	0:281d6ff68967	114	*
hexley	0:281d6ff68967	115	* XXX Why does he not just call churnRand() for each block? Probably
hexley	0:281d6ff68967	116	* so that you don't ever publish the seed which could possibly help
hexley	0:281d6ff68967	117	* predict future values.
hexley	0:281d6ff68967	118	* XXX Why don't we preserve md5 between blocks and just update it with
hexley	0:281d6ff68967	119	* randCount each time? Probably there is a weakness but I wish that
hexley	0:281d6ff68967	120	* it was documented.
hexley	0:281d6ff68967	121	*/
hexley	0:281d6ff68967	122	void
hexley	0:281d6ff68967	123	avGenRand(char *buf, u32_t bufLen)
hexley	0:281d6ff68967	124	{
hexley	0:281d6ff68967	125	MD5_CTX md5;
hexley	0:281d6ff68967	126	u_char tmp[16];
hexley	0:281d6ff68967	127	u32_t n;
hexley	0:281d6ff68967	128
hexley	0:281d6ff68967	129	while (bufLen > 0) {
hexley	0:281d6ff68967	130	n = LWIP_MIN(bufLen, RANDPOOLSZ);
hexley	0:281d6ff68967	131	MD5Init(&md5);
hexley	0:281d6ff68967	132	MD5Update(&md5, (u_char *)randPool, sizeof(randPool));
hexley	0:281d6ff68967	133	MD5Update(&md5, (u_char *)&randCount, sizeof(randCount));
hexley	0:281d6ff68967	134	MD5Final(tmp, &md5);
hexley	0:281d6ff68967	135	randCount++;
hexley	0:281d6ff68967	136	MEMCPY(buf, tmp, n);
hexley	0:281d6ff68967	137	buf += n;
hexley	0:281d6ff68967	138	bufLen -= n;
hexley	0:281d6ff68967	139	}
hexley	0:281d6ff68967	140	}
hexley	0:281d6ff68967	141
hexley	0:281d6ff68967	142	/*
hexley	0:281d6ff68967	143	* Return a new random number.
hexley	0:281d6ff68967	144	*/
hexley	0:281d6ff68967	145	u32_t
hexley	0:281d6ff68967	146	avRandom()
hexley	0:281d6ff68967	147	{
hexley	0:281d6ff68967	148	u32_t newRand;
hexley	0:281d6ff68967	149
hexley	0:281d6ff68967	150	avGenRand((char *)&newRand, sizeof(newRand));
hexley	0:281d6ff68967	151
hexley	0:281d6ff68967	152	return newRand;
hexley	0:281d6ff68967	153	}
hexley	0:281d6ff68967	154
hexley	0:281d6ff68967	155	#else /* MD5_SUPPORT */
hexley	0:281d6ff68967	156
hexley	0:281d6ff68967	157	/*****************************/
hexley	0:281d6ff68967	158	/* LOCAL DATA STRUCTURES */
hexley	0:281d6ff68967	159	/*****************************/
hexley	0:281d6ff68967	160	static int avRandomized = 0; /* Set when truely randomized. */
hexley	0:281d6ff68967	161	static u32_t avRandomSeed = 0; /* Seed used for random number generation. */
hexley	0:281d6ff68967	162
hexley	0:281d6ff68967	163
hexley	0:281d6ff68967	164	/***********************************/
hexley	0:281d6ff68967	165	/* PUBLIC FUNCTION DEFINITIONS */
hexley	0:281d6ff68967	166	/***********************************/
hexley	0:281d6ff68967	167	/*
hexley	0:281d6ff68967	168	* Initialize the random number generator.
hexley	0:281d6ff68967	169	*
hexley	0:281d6ff68967	170	* Here we attempt to compute a random number seed but even if
hexley	0:281d6ff68967	171	* it isn't random, we'll randomize it later.
hexley	0:281d6ff68967	172	*
hexley	0:281d6ff68967	173	* The current method uses the fields from the real time clock,
hexley	0:281d6ff68967	174	* the idle process counter, the millisecond counter, and the
hexley	0:281d6ff68967	175	* hardware timer tick counter. When this is invoked
hexley	0:281d6ff68967	176	* in startup(), then the idle counter and timer values may
hexley	0:281d6ff68967	177	* repeat after each boot and the real time clock may not be
hexley	0:281d6ff68967	178	* operational. Thus we call it again on the first random
hexley	0:281d6ff68967	179	* event.
hexley	0:281d6ff68967	180	*/
hexley	0:281d6ff68967	181	void
hexley	0:281d6ff68967	182	avRandomInit()
hexley	0:281d6ff68967	183	{
hexley	0:281d6ff68967	184	#if 0
hexley	0:281d6ff68967	185	/* Get a pointer into the last 4 bytes of clockBuf. */
hexley	0:281d6ff68967	186	u32_t lptr1 = (u32_t )((char *)&clockBuf[3]);
hexley	0:281d6ff68967	187
hexley	0:281d6ff68967	188	/*
hexley	0:281d6ff68967	189	* Initialize our seed using the real-time clock, the idle
hexley	0:281d6ff68967	190	* counter, the millisecond timer, and the hardware timer
hexley	0:281d6ff68967	191	* tick counter. The real-time clock and the hardware
hexley	0:281d6ff68967	192	* tick counter are the best sources of randomness but
hexley	0:281d6ff68967	193	* since the tick counter is only 16 bit (and truncated
hexley	0:281d6ff68967	194	* at that), the idle counter and millisecond timer
hexley	0:281d6ff68967	195	* (which may be small values) are added to help
hexley	0:281d6ff68967	196	* randomize the lower 16 bits of the seed.
hexley	0:281d6ff68967	197	*/
hexley	0:281d6ff68967	198	readClk();
hexley	0:281d6ff68967	199	avRandomSeed += (u32_t )clockBuf + *lptr1 + OSIdleCtr
hexley	0:281d6ff68967	200	+ ppp_mtime() + ((u32_t)TM1 << 16) + TM1;
hexley	0:281d6ff68967	201	#else
hexley	0:281d6ff68967	202	avRandomSeed += sys_jiffies(); /* XXX */
hexley	0:281d6ff68967	203	#endif
hexley	0:281d6ff68967	204
hexley	0:281d6ff68967	205	/* Initialize the Borland random number generator. */
hexley	0:281d6ff68967	206	srand((unsigned)avRandomSeed);
hexley	0:281d6ff68967	207	}
hexley	0:281d6ff68967	208
hexley	0:281d6ff68967	209	/*
hexley	0:281d6ff68967	210	* Randomize our random seed value. Here we use the fact that
hexley	0:281d6ff68967	211	* this function is called at truely random times by the polling
hexley	0:281d6ff68967	212	* and network functions. Here we only get 16 bits of new random
hexley	0:281d6ff68967	213	* value but we use the previous value to randomize the other 16
hexley	0:281d6ff68967	214	* bits.
hexley	0:281d6ff68967	215	*/
hexley	0:281d6ff68967	216	void
hexley	0:281d6ff68967	217	avRandomize(void)
hexley	0:281d6ff68967	218	{
hexley	0:281d6ff68967	219	static u32_t last_jiffies;
hexley	0:281d6ff68967	220
hexley	0:281d6ff68967	221	if (!avRandomized) {
hexley	0:281d6ff68967	222	avRandomized = !0;
hexley	0:281d6ff68967	223	avRandomInit();
hexley	0:281d6ff68967	224	/* The initialization function also updates the seed. */
hexley	0:281d6ff68967	225	} else {
hexley	0:281d6ff68967	226	/* avRandomSeed += (avRandomSeed << 16) + TM1; */
hexley	0:281d6ff68967	227	avRandomSeed += (sys_jiffies() - last_jiffies); /* XXX */
hexley	0:281d6ff68967	228	}
hexley	0:281d6ff68967	229	last_jiffies = sys_jiffies();
hexley	0:281d6ff68967	230	}
hexley	0:281d6ff68967	231
hexley	0:281d6ff68967	232	/*
hexley	0:281d6ff68967	233	* Return a new random number.
hexley	0:281d6ff68967	234	* Here we use the Borland rand() function to supply a pseudo random
hexley	0:281d6ff68967	235	* number which we make truely random by combining it with our own
hexley	0:281d6ff68967	236	* seed which is randomized by truely random events.
hexley	0:281d6ff68967	237	* Thus the numbers will be truely random unless there have been no
hexley	0:281d6ff68967	238	* operator or network events in which case it will be pseudo random
hexley	0:281d6ff68967	239	* seeded by the real time clock.
hexley	0:281d6ff68967	240	*/
hexley	0:281d6ff68967	241	u32_t
hexley	0:281d6ff68967	242	avRandom()
hexley	0:281d6ff68967	243	{
hexley	0:281d6ff68967	244	return ((((u32_t)rand() << 16) + rand()) + avRandomSeed);
hexley	0:281d6ff68967	245	}
hexley	0:281d6ff68967	246
hexley	0:281d6ff68967	247	#endif /* MD5_SUPPORT */
hexley	0:281d6ff68967	248
hexley	0:281d6ff68967	249	#endif /* PPP_SUPPORT */

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Type:	Library
Created:	19 Nov 2010
Imports:	44
Forks:	0
Commits:	1
Dependents:	0
Dependencies:	0
Followers:	1

lwip/netif/ppp/randm.c@0:281d6ff68967, 2010-11-19 (annotated)

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