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lwip/netif/ppp/randm.c@0:632c9925f013, 2010-06-11 (annotated)

Committer:: donatien
Date:: Fri Jun 11 16:05:15 2010 +0000
Revision:: 0:632c9925f013

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User	Revision	Line number	New contents of line
donatien	0:632c9925f013	1	/*****************************************************************************
donatien	0:632c9925f013	2	* randm.c - Random number generator program file.
donatien	0:632c9925f013	3	*
donatien	0:632c9925f013	4	* Copyright (c) 2003 by Marc Boucher, Services Informatiques (MBSI) inc.
donatien	0:632c9925f013	5	* Copyright (c) 1998 by Global Election Systems Inc.
donatien	0:632c9925f013	6	*
donatien	0:632c9925f013	7	* The authors hereby grant permission to use, copy, modify, distribute,
donatien	0:632c9925f013	8	* and license this software and its documentation for any purpose, provided
donatien	0:632c9925f013	9	* that existing copyright notices are retained in all copies and that this
donatien	0:632c9925f013	10	* notice and the following disclaimer are included verbatim in any
donatien	0:632c9925f013	11	* distributions. No written agreement, license, or royalty fee is required
donatien	0:632c9925f013	12	* for any of the authorized uses.
donatien	0:632c9925f013	13	*
donatien	0:632c9925f013	14	* THIS SOFTWARE IS PROVIDED BY THE CONTRIBUTORS AS IS AND ANY EXPRESS OR
donatien	0:632c9925f013	15	* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
donatien	0:632c9925f013	16	* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
donatien	0:632c9925f013	17	* IN NO EVENT SHALL THE CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
donatien	0:632c9925f013	18	* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
donatien	0:632c9925f013	19	* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
donatien	0:632c9925f013	20	* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
donatien	0:632c9925f013	21	* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
donatien	0:632c9925f013	22	* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
donatien	0:632c9925f013	23	* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
donatien	0:632c9925f013	24	*
donatien	0:632c9925f013	25	******************************************************************************
donatien	0:632c9925f013	26	* REVISION HISTORY
donatien	0:632c9925f013	27	*
donatien	0:632c9925f013	28	* 03-01-01 Marc Boucher <marc@mbsi.ca>
donatien	0:632c9925f013	29	* Ported to lwIP.
donatien	0:632c9925f013	30	* 98-06-03 Guy Lancaster <lancasterg@acm.org>, Global Election Systems Inc.
donatien	0:632c9925f013	31	* Extracted from avos.
donatien	0:632c9925f013	32	*****************************************************************************/
donatien	0:632c9925f013	33
donatien	0:632c9925f013	34	#include "lwip/opt.h"
donatien	0:632c9925f013	35
donatien	0:632c9925f013	36	#if PPP_SUPPORT /* don't build if not configured for use in lwipopts.h */
donatien	0:632c9925f013	37
donatien	0:632c9925f013	38	#include "md5.h"
donatien	0:632c9925f013	39	#include "randm.h"
donatien	0:632c9925f013	40
donatien	0:632c9925f013	41	#include "ppp.h"
donatien	0:632c9925f013	42	#include "pppdebug.h"
donatien	0:632c9925f013	43
donatien	0:632c9925f013	44	#include <string.h>
donatien	0:632c9925f013	45
donatien	0:632c9925f013	46	#if MD5_SUPPORT /* this module depends on MD5 */
donatien	0:632c9925f013	47	#define RANDPOOLSZ 16 /* Bytes stored in the pool of randomness. */
donatien	0:632c9925f013	48
donatien	0:632c9925f013	49	/*****************************/
donatien	0:632c9925f013	50	/* LOCAL DATA STRUCTURES */
donatien	0:632c9925f013	51	/*****************************/
donatien	0:632c9925f013	52	static char randPool[RANDPOOLSZ]; /* Pool of randomness. */
donatien	0:632c9925f013	53	static long randCount = 0; /* Pseudo-random incrementer */
donatien	0:632c9925f013	54
donatien	0:632c9925f013	55
donatien	0:632c9925f013	56	/***********************************/
donatien	0:632c9925f013	57	/* PUBLIC FUNCTION DEFINITIONS */
donatien	0:632c9925f013	58	/***********************************/
donatien	0:632c9925f013	59	/*
donatien	0:632c9925f013	60	* Initialize the random number generator.
donatien	0:632c9925f013	61	*
donatien	0:632c9925f013	62	* Since this is to be called on power up, we don't have much
donatien	0:632c9925f013	63	* system randomess to work with. Here all we use is the
donatien	0:632c9925f013	64	* real-time clock. We'll accumulate more randomness as soon
donatien	0:632c9925f013	65	* as things start happening.
donatien	0:632c9925f013	66	*/
donatien	0:632c9925f013	67	void
donatien	0:632c9925f013	68	avRandomInit()
donatien	0:632c9925f013	69	{
donatien	0:632c9925f013	70	avChurnRand(NULL, 0);
donatien	0:632c9925f013	71	}
donatien	0:632c9925f013	72
donatien	0:632c9925f013	73	/*
donatien	0:632c9925f013	74	* Churn the randomness pool on a random event. Call this early and often
donatien	0:632c9925f013	75	* on random and semi-random system events to build randomness in time for
donatien	0:632c9925f013	76	* usage. For randomly timed events, pass a null pointer and a zero length
donatien	0:632c9925f013	77	* and this will use the system timer and other sources to add randomness.
donatien	0:632c9925f013	78	* If new random data is available, pass a pointer to that and it will be
donatien	0:632c9925f013	79	* included.
donatien	0:632c9925f013	80	*
donatien	0:632c9925f013	81	* Ref: Applied Cryptography 2nd Ed. by Bruce Schneier p. 427
donatien	0:632c9925f013	82	*/
donatien	0:632c9925f013	83	void
donatien	0:632c9925f013	84	avChurnRand(char *randData, u32_t randLen)
donatien	0:632c9925f013	85	{
donatien	0:632c9925f013	86	MD5_CTX md5;
donatien	0:632c9925f013	87
donatien	0:632c9925f013	88	/* LWIP_DEBUGF(LOG_INFO, ("churnRand: %u@%P\n", randLen, randData)); */
donatien	0:632c9925f013	89	MD5Init(&md5);
donatien	0:632c9925f013	90	MD5Update(&md5, (u_char *)randPool, sizeof(randPool));
donatien	0:632c9925f013	91	if (randData) {
donatien	0:632c9925f013	92	MD5Update(&md5, (u_char *)randData, randLen);
donatien	0:632c9925f013	93	} else {
donatien	0:632c9925f013	94	struct {
donatien	0:632c9925f013	95	/* INCLUDE fields for any system sources of randomness */
donatien	0:632c9925f013	96	char foobar;
donatien	0:632c9925f013	97	} sysData;
donatien	0:632c9925f013	98
donatien	0:632c9925f013	99	/* Load sysData fields here. */
donatien	0:632c9925f013	100	MD5Update(&md5, (u_char *)&sysData, sizeof(sysData));
donatien	0:632c9925f013	101	}
donatien	0:632c9925f013	102	MD5Final((u_char *)randPool, &md5);
donatien	0:632c9925f013	103	/* LWIP_DEBUGF(LOG_INFO, ("churnRand: -> 0\n")); */
donatien	0:632c9925f013	104	}
donatien	0:632c9925f013	105
donatien	0:632c9925f013	106	/*
donatien	0:632c9925f013	107	* Use the random pool to generate random data. This degrades to pseudo
donatien	0:632c9925f013	108	* random when used faster than randomness is supplied using churnRand().
donatien	0:632c9925f013	109	* Note: It's important that there be sufficient randomness in randPool
donatien	0:632c9925f013	110	* before this is called for otherwise the range of the result may be
donatien	0:632c9925f013	111	* narrow enough to make a search feasible.
donatien	0:632c9925f013	112	*
donatien	0:632c9925f013	113	* Ref: Applied Cryptography 2nd Ed. by Bruce Schneier p. 427
donatien	0:632c9925f013	114	*
donatien	0:632c9925f013	115	* XXX Why does he not just call churnRand() for each block? Probably
donatien	0:632c9925f013	116	* so that you don't ever publish the seed which could possibly help
donatien	0:632c9925f013	117	* predict future values.
donatien	0:632c9925f013	118	* XXX Why don't we preserve md5 between blocks and just update it with
donatien	0:632c9925f013	119	* randCount each time? Probably there is a weakness but I wish that
donatien	0:632c9925f013	120	* it was documented.
donatien	0:632c9925f013	121	*/
donatien	0:632c9925f013	122	void
donatien	0:632c9925f013	123	avGenRand(char *buf, u32_t bufLen)
donatien	0:632c9925f013	124	{
donatien	0:632c9925f013	125	MD5_CTX md5;
donatien	0:632c9925f013	126	u_char tmp[16];
donatien	0:632c9925f013	127	u32_t n;
donatien	0:632c9925f013	128
donatien	0:632c9925f013	129	while (bufLen > 0) {
donatien	0:632c9925f013	130	n = LWIP_MIN(bufLen, RANDPOOLSZ);
donatien	0:632c9925f013	131	MD5Init(&md5);
donatien	0:632c9925f013	132	MD5Update(&md5, (u_char *)randPool, sizeof(randPool));
donatien	0:632c9925f013	133	MD5Update(&md5, (u_char *)&randCount, sizeof(randCount));
donatien	0:632c9925f013	134	MD5Final(tmp, &md5);
donatien	0:632c9925f013	135	randCount++;
donatien	0:632c9925f013	136	MEMCPY(buf, tmp, n);
donatien	0:632c9925f013	137	buf += n;
donatien	0:632c9925f013	138	bufLen -= n;
donatien	0:632c9925f013	139	}
donatien	0:632c9925f013	140	}
donatien	0:632c9925f013	141
donatien	0:632c9925f013	142	/*
donatien	0:632c9925f013	143	* Return a new random number.
donatien	0:632c9925f013	144	*/
donatien	0:632c9925f013	145	u32_t
donatien	0:632c9925f013	146	avRandom()
donatien	0:632c9925f013	147	{
donatien	0:632c9925f013	148	u32_t newRand;
donatien	0:632c9925f013	149
donatien	0:632c9925f013	150	avGenRand((char *)&newRand, sizeof(newRand));
donatien	0:632c9925f013	151
donatien	0:632c9925f013	152	return newRand;
donatien	0:632c9925f013	153	}
donatien	0:632c9925f013	154
donatien	0:632c9925f013	155	#else /* MD5_SUPPORT */
donatien	0:632c9925f013	156
donatien	0:632c9925f013	157	/*****************************/
donatien	0:632c9925f013	158	/* LOCAL DATA STRUCTURES */
donatien	0:632c9925f013	159	/*****************************/
donatien	0:632c9925f013	160	static int avRandomized = 0; /* Set when truely randomized. */
donatien	0:632c9925f013	161	static u32_t avRandomSeed = 0; /* Seed used for random number generation. */
donatien	0:632c9925f013	162
donatien	0:632c9925f013	163
donatien	0:632c9925f013	164	/***********************************/
donatien	0:632c9925f013	165	/* PUBLIC FUNCTION DEFINITIONS */
donatien	0:632c9925f013	166	/***********************************/
donatien	0:632c9925f013	167	/*
donatien	0:632c9925f013	168	* Initialize the random number generator.
donatien	0:632c9925f013	169	*
donatien	0:632c9925f013	170	* Here we attempt to compute a random number seed but even if
donatien	0:632c9925f013	171	* it isn't random, we'll randomize it later.
donatien	0:632c9925f013	172	*
donatien	0:632c9925f013	173	* The current method uses the fields from the real time clock,
donatien	0:632c9925f013	174	* the idle process counter, the millisecond counter, and the
donatien	0:632c9925f013	175	* hardware timer tick counter. When this is invoked
donatien	0:632c9925f013	176	* in startup(), then the idle counter and timer values may
donatien	0:632c9925f013	177	* repeat after each boot and the real time clock may not be
donatien	0:632c9925f013	178	* operational. Thus we call it again on the first random
donatien	0:632c9925f013	179	* event.
donatien	0:632c9925f013	180	*/
donatien	0:632c9925f013	181	void
donatien	0:632c9925f013	182	avRandomInit()
donatien	0:632c9925f013	183	{
donatien	0:632c9925f013	184	#if 0
donatien	0:632c9925f013	185	/* Get a pointer into the last 4 bytes of clockBuf. */
donatien	0:632c9925f013	186	u32_t lptr1 = (u32_t )((char *)&clockBuf[3]);
donatien	0:632c9925f013	187
donatien	0:632c9925f013	188	/*
donatien	0:632c9925f013	189	* Initialize our seed using the real-time clock, the idle
donatien	0:632c9925f013	190	* counter, the millisecond timer, and the hardware timer
donatien	0:632c9925f013	191	* tick counter. The real-time clock and the hardware
donatien	0:632c9925f013	192	* tick counter are the best sources of randomness but
donatien	0:632c9925f013	193	* since the tick counter is only 16 bit (and truncated
donatien	0:632c9925f013	194	* at that), the idle counter and millisecond timer
donatien	0:632c9925f013	195	* (which may be small values) are added to help
donatien	0:632c9925f013	196	* randomize the lower 16 bits of the seed.
donatien	0:632c9925f013	197	*/
donatien	0:632c9925f013	198	readClk();
donatien	0:632c9925f013	199	avRandomSeed += (u32_t )clockBuf + *lptr1 + OSIdleCtr
donatien	0:632c9925f013	200	+ ppp_mtime() + ((u32_t)TM1 << 16) + TM1;
donatien	0:632c9925f013	201	#else
donatien	0:632c9925f013	202	avRandomSeed += sys_jiffies(); /* XXX */
donatien	0:632c9925f013	203	#endif
donatien	0:632c9925f013	204
donatien	0:632c9925f013	205	/* Initialize the Borland random number generator. */
donatien	0:632c9925f013	206	srand((unsigned)avRandomSeed);
donatien	0:632c9925f013	207	}
donatien	0:632c9925f013	208
donatien	0:632c9925f013	209	/*
donatien	0:632c9925f013	210	* Randomize our random seed value. Here we use the fact that
donatien	0:632c9925f013	211	* this function is called at truely random times by the polling
donatien	0:632c9925f013	212	* and network functions. Here we only get 16 bits of new random
donatien	0:632c9925f013	213	* value but we use the previous value to randomize the other 16
donatien	0:632c9925f013	214	* bits.
donatien	0:632c9925f013	215	*/
donatien	0:632c9925f013	216	void
donatien	0:632c9925f013	217	avRandomize(void)
donatien	0:632c9925f013	218	{
donatien	0:632c9925f013	219	static u32_t last_jiffies;
donatien	0:632c9925f013	220
donatien	0:632c9925f013	221	if (!avRandomized) {
donatien	0:632c9925f013	222	avRandomized = !0;
donatien	0:632c9925f013	223	avRandomInit();
donatien	0:632c9925f013	224	/* The initialization function also updates the seed. */
donatien	0:632c9925f013	225	} else {
donatien	0:632c9925f013	226	/* avRandomSeed += (avRandomSeed << 16) + TM1; */
donatien	0:632c9925f013	227	avRandomSeed += (sys_jiffies() - last_jiffies); /* XXX */
donatien	0:632c9925f013	228	}
donatien	0:632c9925f013	229	last_jiffies = sys_jiffies();
donatien	0:632c9925f013	230	}
donatien	0:632c9925f013	231
donatien	0:632c9925f013	232	/*
donatien	0:632c9925f013	233	* Return a new random number.
donatien	0:632c9925f013	234	* Here we use the Borland rand() function to supply a pseudo random
donatien	0:632c9925f013	235	* number which we make truely random by combining it with our own
donatien	0:632c9925f013	236	* seed which is randomized by truely random events.
donatien	0:632c9925f013	237	* Thus the numbers will be truely random unless there have been no
donatien	0:632c9925f013	238	* operator or network events in which case it will be pseudo random
donatien	0:632c9925f013	239	* seeded by the real time clock.
donatien	0:632c9925f013	240	*/
donatien	0:632c9925f013	241	u32_t
donatien	0:632c9925f013	242	avRandom()
donatien	0:632c9925f013	243	{
donatien	0:632c9925f013	244	return ((((u32_t)rand() << 16) + rand()) + avRandomSeed);
donatien	0:632c9925f013	245	}
donatien	0:632c9925f013	246
donatien	0:632c9925f013	247	#endif /* MD5_SUPPORT */
donatien	0:632c9925f013	248
donatien	0:632c9925f013	249	#endif /* PPP_SUPPORT */

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Type:	Program
Created:	11 Jun 2010
Imports:	2654
Forks:	0
Commits:	12
Dependents:	3
Dependencies:	0
Followers:	13

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lwip/netif/ppp/randm.c@0:632c9925f013, 2010-06-11 (annotated)

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