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lwip/netif/ppp/randm.c@0:d616ece2d859, 2010-09-18 (annotated)

Committer:: mbed714
Date:: Sat Sep 18 23:05:49 2010 +0000
Revision:: 0:d616ece2d859

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User	Revision	Line number	New contents of line
mbed714	0:d616ece2d859	1	/*****************************************************************************
mbed714	0:d616ece2d859	2	* randm.c - Random number generator program file.
mbed714	0:d616ece2d859	3	*
mbed714	0:d616ece2d859	4	* Copyright (c) 2003 by Marc Boucher, Services Informatiques (MBSI) inc.
mbed714	0:d616ece2d859	5	* Copyright (c) 1998 by Global Election Systems Inc.
mbed714	0:d616ece2d859	6	*
mbed714	0:d616ece2d859	7	* The authors hereby grant permission to use, copy, modify, distribute,
mbed714	0:d616ece2d859	8	* and license this software and its documentation for any purpose, provided
mbed714	0:d616ece2d859	9	* that existing copyright notices are retained in all copies and that this
mbed714	0:d616ece2d859	10	* notice and the following disclaimer are included verbatim in any
mbed714	0:d616ece2d859	11	* distributions. No written agreement, license, or royalty fee is required
mbed714	0:d616ece2d859	12	* for any of the authorized uses.
mbed714	0:d616ece2d859	13	*
mbed714	0:d616ece2d859	14	* THIS SOFTWARE IS PROVIDED BY THE CONTRIBUTORS AS IS AND ANY EXPRESS OR
mbed714	0:d616ece2d859	15	* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
mbed714	0:d616ece2d859	16	* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
mbed714	0:d616ece2d859	17	* IN NO EVENT SHALL THE CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
mbed714	0:d616ece2d859	18	* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
mbed714	0:d616ece2d859	19	* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
mbed714	0:d616ece2d859	20	* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
mbed714	0:d616ece2d859	21	* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
mbed714	0:d616ece2d859	22	* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
mbed714	0:d616ece2d859	23	* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
mbed714	0:d616ece2d859	24	*
mbed714	0:d616ece2d859	25	******************************************************************************
mbed714	0:d616ece2d859	26	* REVISION HISTORY
mbed714	0:d616ece2d859	27	*
mbed714	0:d616ece2d859	28	* 03-01-01 Marc Boucher <marc@mbsi.ca>
mbed714	0:d616ece2d859	29	* Ported to lwIP.
mbed714	0:d616ece2d859	30	* 98-06-03 Guy Lancaster <lancasterg@acm.org>, Global Election Systems Inc.
mbed714	0:d616ece2d859	31	* Extracted from avos.
mbed714	0:d616ece2d859	32	*****************************************************************************/
mbed714	0:d616ece2d859	33
mbed714	0:d616ece2d859	34	#include "lwip/opt.h"
mbed714	0:d616ece2d859	35
mbed714	0:d616ece2d859	36	#if PPP_SUPPORT /* don't build if not configured for use in lwipopts.h */
mbed714	0:d616ece2d859	37
mbed714	0:d616ece2d859	38	#include "md5.h"
mbed714	0:d616ece2d859	39	#include "randm.h"
mbed714	0:d616ece2d859	40
mbed714	0:d616ece2d859	41	#include "ppp.h"
mbed714	0:d616ece2d859	42	#include "pppdebug.h"
mbed714	0:d616ece2d859	43
mbed714	0:d616ece2d859	44	#include <string.h>
mbed714	0:d616ece2d859	45
mbed714	0:d616ece2d859	46	#if MD5_SUPPORT /* this module depends on MD5 */
mbed714	0:d616ece2d859	47	#define RANDPOOLSZ 16 /* Bytes stored in the pool of randomness. */
mbed714	0:d616ece2d859	48
mbed714	0:d616ece2d859	49	/*****************************/
mbed714	0:d616ece2d859	50	/* LOCAL DATA STRUCTURES */
mbed714	0:d616ece2d859	51	/*****************************/
mbed714	0:d616ece2d859	52	static char randPool[RANDPOOLSZ]; /* Pool of randomness. */
mbed714	0:d616ece2d859	53	static long randCount = 0; /* Pseudo-random incrementer */
mbed714	0:d616ece2d859	54
mbed714	0:d616ece2d859	55
mbed714	0:d616ece2d859	56	/***********************************/
mbed714	0:d616ece2d859	57	/* PUBLIC FUNCTION DEFINITIONS */
mbed714	0:d616ece2d859	58	/***********************************/
mbed714	0:d616ece2d859	59	/*
mbed714	0:d616ece2d859	60	* Initialize the random number generator.
mbed714	0:d616ece2d859	61	*
mbed714	0:d616ece2d859	62	* Since this is to be called on power up, we don't have much
mbed714	0:d616ece2d859	63	* system randomess to work with. Here all we use is the
mbed714	0:d616ece2d859	64	* real-time clock. We'll accumulate more randomness as soon
mbed714	0:d616ece2d859	65	* as things start happening.
mbed714	0:d616ece2d859	66	*/
mbed714	0:d616ece2d859	67	void
mbed714	0:d616ece2d859	68	avRandomInit()
mbed714	0:d616ece2d859	69	{
mbed714	0:d616ece2d859	70	avChurnRand(NULL, 0);
mbed714	0:d616ece2d859	71	}
mbed714	0:d616ece2d859	72
mbed714	0:d616ece2d859	73	/*
mbed714	0:d616ece2d859	74	* Churn the randomness pool on a random event. Call this early and often
mbed714	0:d616ece2d859	75	* on random and semi-random system events to build randomness in time for
mbed714	0:d616ece2d859	76	* usage. For randomly timed events, pass a null pointer and a zero length
mbed714	0:d616ece2d859	77	* and this will use the system timer and other sources to add randomness.
mbed714	0:d616ece2d859	78	* If new random data is available, pass a pointer to that and it will be
mbed714	0:d616ece2d859	79	* included.
mbed714	0:d616ece2d859	80	*
mbed714	0:d616ece2d859	81	* Ref: Applied Cryptography 2nd Ed. by Bruce Schneier p. 427
mbed714	0:d616ece2d859	82	*/
mbed714	0:d616ece2d859	83	void
mbed714	0:d616ece2d859	84	avChurnRand(char *randData, u32_t randLen)
mbed714	0:d616ece2d859	85	{
mbed714	0:d616ece2d859	86	MD5_CTX md5;
mbed714	0:d616ece2d859	87
mbed714	0:d616ece2d859	88	/* LWIP_DEBUGF(LOG_INFO, ("churnRand: %u@%P\n", randLen, randData)); */
mbed714	0:d616ece2d859	89	MD5Init(&md5);
mbed714	0:d616ece2d859	90	MD5Update(&md5, (u_char *)randPool, sizeof(randPool));
mbed714	0:d616ece2d859	91	if (randData) {
mbed714	0:d616ece2d859	92	MD5Update(&md5, (u_char *)randData, randLen);
mbed714	0:d616ece2d859	93	} else {
mbed714	0:d616ece2d859	94	struct {
mbed714	0:d616ece2d859	95	/* INCLUDE fields for any system sources of randomness */
mbed714	0:d616ece2d859	96	char foobar;
mbed714	0:d616ece2d859	97	} sysData;
mbed714	0:d616ece2d859	98
mbed714	0:d616ece2d859	99	/* Load sysData fields here. */
mbed714	0:d616ece2d859	100	MD5Update(&md5, (u_char *)&sysData, sizeof(sysData));
mbed714	0:d616ece2d859	101	}
mbed714	0:d616ece2d859	102	MD5Final((u_char *)randPool, &md5);
mbed714	0:d616ece2d859	103	/* LWIP_DEBUGF(LOG_INFO, ("churnRand: -> 0\n")); */
mbed714	0:d616ece2d859	104	}
mbed714	0:d616ece2d859	105
mbed714	0:d616ece2d859	106	/*
mbed714	0:d616ece2d859	107	* Use the random pool to generate random data. This degrades to pseudo
mbed714	0:d616ece2d859	108	* random when used faster than randomness is supplied using churnRand().
mbed714	0:d616ece2d859	109	* Note: It's important that there be sufficient randomness in randPool
mbed714	0:d616ece2d859	110	* before this is called for otherwise the range of the result may be
mbed714	0:d616ece2d859	111	* narrow enough to make a search feasible.
mbed714	0:d616ece2d859	112	*
mbed714	0:d616ece2d859	113	* Ref: Applied Cryptography 2nd Ed. by Bruce Schneier p. 427
mbed714	0:d616ece2d859	114	*
mbed714	0:d616ece2d859	115	* XXX Why does he not just call churnRand() for each block? Probably
mbed714	0:d616ece2d859	116	* so that you don't ever publish the seed which could possibly help
mbed714	0:d616ece2d859	117	* predict future values.
mbed714	0:d616ece2d859	118	* XXX Why don't we preserve md5 between blocks and just update it with
mbed714	0:d616ece2d859	119	* randCount each time? Probably there is a weakness but I wish that
mbed714	0:d616ece2d859	120	* it was documented.
mbed714	0:d616ece2d859	121	*/
mbed714	0:d616ece2d859	122	void
mbed714	0:d616ece2d859	123	avGenRand(char *buf, u32_t bufLen)
mbed714	0:d616ece2d859	124	{
mbed714	0:d616ece2d859	125	MD5_CTX md5;
mbed714	0:d616ece2d859	126	u_char tmp[16];
mbed714	0:d616ece2d859	127	u32_t n;
mbed714	0:d616ece2d859	128
mbed714	0:d616ece2d859	129	while (bufLen > 0) {
mbed714	0:d616ece2d859	130	n = LWIP_MIN(bufLen, RANDPOOLSZ);
mbed714	0:d616ece2d859	131	MD5Init(&md5);
mbed714	0:d616ece2d859	132	MD5Update(&md5, (u_char *)randPool, sizeof(randPool));
mbed714	0:d616ece2d859	133	MD5Update(&md5, (u_char *)&randCount, sizeof(randCount));
mbed714	0:d616ece2d859	134	MD5Final(tmp, &md5);
mbed714	0:d616ece2d859	135	randCount++;
mbed714	0:d616ece2d859	136	MEMCPY(buf, tmp, n);
mbed714	0:d616ece2d859	137	buf += n;
mbed714	0:d616ece2d859	138	bufLen -= n;
mbed714	0:d616ece2d859	139	}
mbed714	0:d616ece2d859	140	}
mbed714	0:d616ece2d859	141
mbed714	0:d616ece2d859	142	/*
mbed714	0:d616ece2d859	143	* Return a new random number.
mbed714	0:d616ece2d859	144	*/
mbed714	0:d616ece2d859	145	u32_t
mbed714	0:d616ece2d859	146	avRandom()
mbed714	0:d616ece2d859	147	{
mbed714	0:d616ece2d859	148	u32_t newRand;
mbed714	0:d616ece2d859	149
mbed714	0:d616ece2d859	150	avGenRand((char *)&newRand, sizeof(newRand));
mbed714	0:d616ece2d859	151
mbed714	0:d616ece2d859	152	return newRand;
mbed714	0:d616ece2d859	153	}
mbed714	0:d616ece2d859	154
mbed714	0:d616ece2d859	155	#else /* MD5_SUPPORT */
mbed714	0:d616ece2d859	156
mbed714	0:d616ece2d859	157	/*****************************/
mbed714	0:d616ece2d859	158	/* LOCAL DATA STRUCTURES */
mbed714	0:d616ece2d859	159	/*****************************/
mbed714	0:d616ece2d859	160	static int avRandomized = 0; /* Set when truely randomized. */
mbed714	0:d616ece2d859	161	static u32_t avRandomSeed = 0; /* Seed used for random number generation. */
mbed714	0:d616ece2d859	162
mbed714	0:d616ece2d859	163
mbed714	0:d616ece2d859	164	/***********************************/
mbed714	0:d616ece2d859	165	/* PUBLIC FUNCTION DEFINITIONS */
mbed714	0:d616ece2d859	166	/***********************************/
mbed714	0:d616ece2d859	167	/*
mbed714	0:d616ece2d859	168	* Initialize the random number generator.
mbed714	0:d616ece2d859	169	*
mbed714	0:d616ece2d859	170	* Here we attempt to compute a random number seed but even if
mbed714	0:d616ece2d859	171	* it isn't random, we'll randomize it later.
mbed714	0:d616ece2d859	172	*
mbed714	0:d616ece2d859	173	* The current method uses the fields from the real time clock,
mbed714	0:d616ece2d859	174	* the idle process counter, the millisecond counter, and the
mbed714	0:d616ece2d859	175	* hardware timer tick counter. When this is invoked
mbed714	0:d616ece2d859	176	* in startup(), then the idle counter and timer values may
mbed714	0:d616ece2d859	177	* repeat after each boot and the real time clock may not be
mbed714	0:d616ece2d859	178	* operational. Thus we call it again on the first random
mbed714	0:d616ece2d859	179	* event.
mbed714	0:d616ece2d859	180	*/
mbed714	0:d616ece2d859	181	void
mbed714	0:d616ece2d859	182	avRandomInit()
mbed714	0:d616ece2d859	183	{
mbed714	0:d616ece2d859	184	#if 0
mbed714	0:d616ece2d859	185	/* Get a pointer into the last 4 bytes of clockBuf. */
mbed714	0:d616ece2d859	186	u32_t lptr1 = (u32_t )((char *)&clockBuf[3]);
mbed714	0:d616ece2d859	187
mbed714	0:d616ece2d859	188	/*
mbed714	0:d616ece2d859	189	* Initialize our seed using the real-time clock, the idle
mbed714	0:d616ece2d859	190	* counter, the millisecond timer, and the hardware timer
mbed714	0:d616ece2d859	191	* tick counter. The real-time clock and the hardware
mbed714	0:d616ece2d859	192	* tick counter are the best sources of randomness but
mbed714	0:d616ece2d859	193	* since the tick counter is only 16 bit (and truncated
mbed714	0:d616ece2d859	194	* at that), the idle counter and millisecond timer
mbed714	0:d616ece2d859	195	* (which may be small values) are added to help
mbed714	0:d616ece2d859	196	* randomize the lower 16 bits of the seed.
mbed714	0:d616ece2d859	197	*/
mbed714	0:d616ece2d859	198	readClk();
mbed714	0:d616ece2d859	199	avRandomSeed += (u32_t )clockBuf + *lptr1 + OSIdleCtr
mbed714	0:d616ece2d859	200	+ ppp_mtime() + ((u32_t)TM1 << 16) + TM1;
mbed714	0:d616ece2d859	201	#else
mbed714	0:d616ece2d859	202	avRandomSeed += sys_jiffies(); /* XXX */
mbed714	0:d616ece2d859	203	#endif
mbed714	0:d616ece2d859	204
mbed714	0:d616ece2d859	205	/* Initialize the Borland random number generator. */
mbed714	0:d616ece2d859	206	srand((unsigned)avRandomSeed);
mbed714	0:d616ece2d859	207	}
mbed714	0:d616ece2d859	208
mbed714	0:d616ece2d859	209	/*
mbed714	0:d616ece2d859	210	* Randomize our random seed value. Here we use the fact that
mbed714	0:d616ece2d859	211	* this function is called at truely random times by the polling
mbed714	0:d616ece2d859	212	* and network functions. Here we only get 16 bits of new random
mbed714	0:d616ece2d859	213	* value but we use the previous value to randomize the other 16
mbed714	0:d616ece2d859	214	* bits.
mbed714	0:d616ece2d859	215	*/
mbed714	0:d616ece2d859	216	void
mbed714	0:d616ece2d859	217	avRandomize(void)
mbed714	0:d616ece2d859	218	{
mbed714	0:d616ece2d859	219	static u32_t last_jiffies;
mbed714	0:d616ece2d859	220
mbed714	0:d616ece2d859	221	if (!avRandomized) {
mbed714	0:d616ece2d859	222	avRandomized = !0;
mbed714	0:d616ece2d859	223	avRandomInit();
mbed714	0:d616ece2d859	224	/* The initialization function also updates the seed. */
mbed714	0:d616ece2d859	225	} else {
mbed714	0:d616ece2d859	226	/* avRandomSeed += (avRandomSeed << 16) + TM1; */
mbed714	0:d616ece2d859	227	avRandomSeed += (sys_jiffies() - last_jiffies); /* XXX */
mbed714	0:d616ece2d859	228	}
mbed714	0:d616ece2d859	229	last_jiffies = sys_jiffies();
mbed714	0:d616ece2d859	230	}
mbed714	0:d616ece2d859	231
mbed714	0:d616ece2d859	232	/*
mbed714	0:d616ece2d859	233	* Return a new random number.
mbed714	0:d616ece2d859	234	* Here we use the Borland rand() function to supply a pseudo random
mbed714	0:d616ece2d859	235	* number which we make truely random by combining it with our own
mbed714	0:d616ece2d859	236	* seed which is randomized by truely random events.
mbed714	0:d616ece2d859	237	* Thus the numbers will be truely random unless there have been no
mbed714	0:d616ece2d859	238	* operator or network events in which case it will be pseudo random
mbed714	0:d616ece2d859	239	* seeded by the real time clock.
mbed714	0:d616ece2d859	240	*/
mbed714	0:d616ece2d859	241	u32_t
mbed714	0:d616ece2d859	242	avRandom()
mbed714	0:d616ece2d859	243	{
mbed714	0:d616ece2d859	244	return ((((u32_t)rand() << 16) + rand()) + avRandomSeed);
mbed714	0:d616ece2d859	245	}
mbed714	0:d616ece2d859	246
mbed714	0:d616ece2d859	247	#endif /* MD5_SUPPORT */
mbed714	0:d616ece2d859	248
mbed714	0:d616ece2d859	249	#endif /* PPP_SUPPORT */

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Type:	Library
Created:	18 Sep 2010
Imports:	1
Forks:	0
Commits:	1
Dependents:	0
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lwip/netif/ppp/randm.c@0:d616ece2d859, 2010-09-18 (annotated)

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