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lwip/netif/ppp/randm.c@0:ac1725ba162c, 2010-11-09 (annotated)

Committer:: segundo
Date:: Tue Nov 09 20:54:15 2010 +0000
Revision:: 0:ac1725ba162c

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User	Revision	Line number	New contents of line
segundo	0:ac1725ba162c	1	/*****************************************************************************
segundo	0:ac1725ba162c	2	* randm.c - Random number generator program file.
segundo	0:ac1725ba162c	3	*
segundo	0:ac1725ba162c	4	* Copyright (c) 2003 by Marc Boucher, Services Informatiques (MBSI) inc.
segundo	0:ac1725ba162c	5	* Copyright (c) 1998 by Global Election Systems Inc.
segundo	0:ac1725ba162c	6	*
segundo	0:ac1725ba162c	7	* The authors hereby grant permission to use, copy, modify, distribute,
segundo	0:ac1725ba162c	8	* and license this software and its documentation for any purpose, provided
segundo	0:ac1725ba162c	9	* that existing copyright notices are retained in all copies and that this
segundo	0:ac1725ba162c	10	* notice and the following disclaimer are included verbatim in any
segundo	0:ac1725ba162c	11	* distributions. No written agreement, license, or royalty fee is required
segundo	0:ac1725ba162c	12	* for any of the authorized uses.
segundo	0:ac1725ba162c	13	*
segundo	0:ac1725ba162c	14	* THIS SOFTWARE IS PROVIDED BY THE CONTRIBUTORS AS IS AND ANY EXPRESS OR
segundo	0:ac1725ba162c	15	* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
segundo	0:ac1725ba162c	16	* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
segundo	0:ac1725ba162c	17	* IN NO EVENT SHALL THE CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
segundo	0:ac1725ba162c	18	* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
segundo	0:ac1725ba162c	19	* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
segundo	0:ac1725ba162c	20	* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
segundo	0:ac1725ba162c	21	* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
segundo	0:ac1725ba162c	22	* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
segundo	0:ac1725ba162c	23	* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
segundo	0:ac1725ba162c	24	*
segundo	0:ac1725ba162c	25	******************************************************************************
segundo	0:ac1725ba162c	26	* REVISION HISTORY
segundo	0:ac1725ba162c	27	*
segundo	0:ac1725ba162c	28	* 03-01-01 Marc Boucher <marc@mbsi.ca>
segundo	0:ac1725ba162c	29	* Ported to lwIP.
segundo	0:ac1725ba162c	30	* 98-06-03 Guy Lancaster <lancasterg@acm.org>, Global Election Systems Inc.
segundo	0:ac1725ba162c	31	* Extracted from avos.
segundo	0:ac1725ba162c	32	*****************************************************************************/
segundo	0:ac1725ba162c	33
segundo	0:ac1725ba162c	34	#include "lwip/opt.h"
segundo	0:ac1725ba162c	35
segundo	0:ac1725ba162c	36	#if PPP_SUPPORT /* don't build if not configured for use in lwipopts.h */
segundo	0:ac1725ba162c	37
segundo	0:ac1725ba162c	38	#include "md5.h"
segundo	0:ac1725ba162c	39	#include "randm.h"
segundo	0:ac1725ba162c	40
segundo	0:ac1725ba162c	41	#include "ppp.h"
segundo	0:ac1725ba162c	42	#include "pppdebug.h"
segundo	0:ac1725ba162c	43
segundo	0:ac1725ba162c	44	#include <string.h>
segundo	0:ac1725ba162c	45
segundo	0:ac1725ba162c	46	#if MD5_SUPPORT /* this module depends on MD5 */
segundo	0:ac1725ba162c	47	#define RANDPOOLSZ 16 /* Bytes stored in the pool of randomness. */
segundo	0:ac1725ba162c	48
segundo	0:ac1725ba162c	49	/*****************************/
segundo	0:ac1725ba162c	50	/* LOCAL DATA STRUCTURES */
segundo	0:ac1725ba162c	51	/*****************************/
segundo	0:ac1725ba162c	52	static char randPool[RANDPOOLSZ]; /* Pool of randomness. */
segundo	0:ac1725ba162c	53	static long randCount = 0; /* Pseudo-random incrementer */
segundo	0:ac1725ba162c	54
segundo	0:ac1725ba162c	55
segundo	0:ac1725ba162c	56	/***********************************/
segundo	0:ac1725ba162c	57	/* PUBLIC FUNCTION DEFINITIONS */
segundo	0:ac1725ba162c	58	/***********************************/
segundo	0:ac1725ba162c	59	/*
segundo	0:ac1725ba162c	60	* Initialize the random number generator.
segundo	0:ac1725ba162c	61	*
segundo	0:ac1725ba162c	62	* Since this is to be called on power up, we don't have much
segundo	0:ac1725ba162c	63	* system randomess to work with. Here all we use is the
segundo	0:ac1725ba162c	64	* real-time clock. We'll accumulate more randomness as soon
segundo	0:ac1725ba162c	65	* as things start happening.
segundo	0:ac1725ba162c	66	*/
segundo	0:ac1725ba162c	67	void
segundo	0:ac1725ba162c	68	avRandomInit()
segundo	0:ac1725ba162c	69	{
segundo	0:ac1725ba162c	70	avChurnRand(NULL, 0);
segundo	0:ac1725ba162c	71	}
segundo	0:ac1725ba162c	72
segundo	0:ac1725ba162c	73	/*
segundo	0:ac1725ba162c	74	* Churn the randomness pool on a random event. Call this early and often
segundo	0:ac1725ba162c	75	* on random and semi-random system events to build randomness in time for
segundo	0:ac1725ba162c	76	* usage. For randomly timed events, pass a null pointer and a zero length
segundo	0:ac1725ba162c	77	* and this will use the system timer and other sources to add randomness.
segundo	0:ac1725ba162c	78	* If new random data is available, pass a pointer to that and it will be
segundo	0:ac1725ba162c	79	* included.
segundo	0:ac1725ba162c	80	*
segundo	0:ac1725ba162c	81	* Ref: Applied Cryptography 2nd Ed. by Bruce Schneier p. 427
segundo	0:ac1725ba162c	82	*/
segundo	0:ac1725ba162c	83	void
segundo	0:ac1725ba162c	84	avChurnRand(char *randData, u32_t randLen)
segundo	0:ac1725ba162c	85	{
segundo	0:ac1725ba162c	86	MD5_CTX md5;
segundo	0:ac1725ba162c	87
segundo	0:ac1725ba162c	88	/* LWIP_DEBUGF(LOG_INFO, ("churnRand: %u@%P\n", randLen, randData)); */
segundo	0:ac1725ba162c	89	MD5Init(&md5);
segundo	0:ac1725ba162c	90	MD5Update(&md5, (u_char *)randPool, sizeof(randPool));
segundo	0:ac1725ba162c	91	if (randData) {
segundo	0:ac1725ba162c	92	MD5Update(&md5, (u_char *)randData, randLen);
segundo	0:ac1725ba162c	93	} else {
segundo	0:ac1725ba162c	94	struct {
segundo	0:ac1725ba162c	95	/* INCLUDE fields for any system sources of randomness */
segundo	0:ac1725ba162c	96	char foobar;
segundo	0:ac1725ba162c	97	} sysData;
segundo	0:ac1725ba162c	98
segundo	0:ac1725ba162c	99	/* Load sysData fields here. */
segundo	0:ac1725ba162c	100	MD5Update(&md5, (u_char *)&sysData, sizeof(sysData));
segundo	0:ac1725ba162c	101	}
segundo	0:ac1725ba162c	102	MD5Final((u_char *)randPool, &md5);
segundo	0:ac1725ba162c	103	/* LWIP_DEBUGF(LOG_INFO, ("churnRand: -> 0\n")); */
segundo	0:ac1725ba162c	104	}
segundo	0:ac1725ba162c	105
segundo	0:ac1725ba162c	106	/*
segundo	0:ac1725ba162c	107	* Use the random pool to generate random data. This degrades to pseudo
segundo	0:ac1725ba162c	108	* random when used faster than randomness is supplied using churnRand().
segundo	0:ac1725ba162c	109	* Note: It's important that there be sufficient randomness in randPool
segundo	0:ac1725ba162c	110	* before this is called for otherwise the range of the result may be
segundo	0:ac1725ba162c	111	* narrow enough to make a search feasible.
segundo	0:ac1725ba162c	112	*
segundo	0:ac1725ba162c	113	* Ref: Applied Cryptography 2nd Ed. by Bruce Schneier p. 427
segundo	0:ac1725ba162c	114	*
segundo	0:ac1725ba162c	115	* XXX Why does he not just call churnRand() for each block? Probably
segundo	0:ac1725ba162c	116	* so that you don't ever publish the seed which could possibly help
segundo	0:ac1725ba162c	117	* predict future values.
segundo	0:ac1725ba162c	118	* XXX Why don't we preserve md5 between blocks and just update it with
segundo	0:ac1725ba162c	119	* randCount each time? Probably there is a weakness but I wish that
segundo	0:ac1725ba162c	120	* it was documented.
segundo	0:ac1725ba162c	121	*/
segundo	0:ac1725ba162c	122	void
segundo	0:ac1725ba162c	123	avGenRand(char *buf, u32_t bufLen)
segundo	0:ac1725ba162c	124	{
segundo	0:ac1725ba162c	125	MD5_CTX md5;
segundo	0:ac1725ba162c	126	u_char tmp[16];
segundo	0:ac1725ba162c	127	u32_t n;
segundo	0:ac1725ba162c	128
segundo	0:ac1725ba162c	129	while (bufLen > 0) {
segundo	0:ac1725ba162c	130	n = LWIP_MIN(bufLen, RANDPOOLSZ);
segundo	0:ac1725ba162c	131	MD5Init(&md5);
segundo	0:ac1725ba162c	132	MD5Update(&md5, (u_char *)randPool, sizeof(randPool));
segundo	0:ac1725ba162c	133	MD5Update(&md5, (u_char *)&randCount, sizeof(randCount));
segundo	0:ac1725ba162c	134	MD5Final(tmp, &md5);
segundo	0:ac1725ba162c	135	randCount++;
segundo	0:ac1725ba162c	136	MEMCPY(buf, tmp, n);
segundo	0:ac1725ba162c	137	buf += n;
segundo	0:ac1725ba162c	138	bufLen -= n;
segundo	0:ac1725ba162c	139	}
segundo	0:ac1725ba162c	140	}
segundo	0:ac1725ba162c	141
segundo	0:ac1725ba162c	142	/*
segundo	0:ac1725ba162c	143	* Return a new random number.
segundo	0:ac1725ba162c	144	*/
segundo	0:ac1725ba162c	145	u32_t
segundo	0:ac1725ba162c	146	avRandom()
segundo	0:ac1725ba162c	147	{
segundo	0:ac1725ba162c	148	u32_t newRand;
segundo	0:ac1725ba162c	149
segundo	0:ac1725ba162c	150	avGenRand((char *)&newRand, sizeof(newRand));
segundo	0:ac1725ba162c	151
segundo	0:ac1725ba162c	152	return newRand;
segundo	0:ac1725ba162c	153	}
segundo	0:ac1725ba162c	154
segundo	0:ac1725ba162c	155	#else /* MD5_SUPPORT */
segundo	0:ac1725ba162c	156
segundo	0:ac1725ba162c	157	/*****************************/
segundo	0:ac1725ba162c	158	/* LOCAL DATA STRUCTURES */
segundo	0:ac1725ba162c	159	/*****************************/
segundo	0:ac1725ba162c	160	static int avRandomized = 0; /* Set when truely randomized. */
segundo	0:ac1725ba162c	161	static u32_t avRandomSeed = 0; /* Seed used for random number generation. */
segundo	0:ac1725ba162c	162
segundo	0:ac1725ba162c	163
segundo	0:ac1725ba162c	164	/***********************************/
segundo	0:ac1725ba162c	165	/* PUBLIC FUNCTION DEFINITIONS */
segundo	0:ac1725ba162c	166	/***********************************/
segundo	0:ac1725ba162c	167	/*
segundo	0:ac1725ba162c	168	* Initialize the random number generator.
segundo	0:ac1725ba162c	169	*
segundo	0:ac1725ba162c	170	* Here we attempt to compute a random number seed but even if
segundo	0:ac1725ba162c	171	* it isn't random, we'll randomize it later.
segundo	0:ac1725ba162c	172	*
segundo	0:ac1725ba162c	173	* The current method uses the fields from the real time clock,
segundo	0:ac1725ba162c	174	* the idle process counter, the millisecond counter, and the
segundo	0:ac1725ba162c	175	* hardware timer tick counter. When this is invoked
segundo	0:ac1725ba162c	176	* in startup(), then the idle counter and timer values may
segundo	0:ac1725ba162c	177	* repeat after each boot and the real time clock may not be
segundo	0:ac1725ba162c	178	* operational. Thus we call it again on the first random
segundo	0:ac1725ba162c	179	* event.
segundo	0:ac1725ba162c	180	*/
segundo	0:ac1725ba162c	181	void
segundo	0:ac1725ba162c	182	avRandomInit()
segundo	0:ac1725ba162c	183	{
segundo	0:ac1725ba162c	184	#if 0
segundo	0:ac1725ba162c	185	/* Get a pointer into the last 4 bytes of clockBuf. */
segundo	0:ac1725ba162c	186	u32_t lptr1 = (u32_t )((char *)&clockBuf[3]);
segundo	0:ac1725ba162c	187
segundo	0:ac1725ba162c	188	/*
segundo	0:ac1725ba162c	189	* Initialize our seed using the real-time clock, the idle
segundo	0:ac1725ba162c	190	* counter, the millisecond timer, and the hardware timer
segundo	0:ac1725ba162c	191	* tick counter. The real-time clock and the hardware
segundo	0:ac1725ba162c	192	* tick counter are the best sources of randomness but
segundo	0:ac1725ba162c	193	* since the tick counter is only 16 bit (and truncated
segundo	0:ac1725ba162c	194	* at that), the idle counter and millisecond timer
segundo	0:ac1725ba162c	195	* (which may be small values) are added to help
segundo	0:ac1725ba162c	196	* randomize the lower 16 bits of the seed.
segundo	0:ac1725ba162c	197	*/
segundo	0:ac1725ba162c	198	readClk();
segundo	0:ac1725ba162c	199	avRandomSeed += (u32_t )clockBuf + *lptr1 + OSIdleCtr
segundo	0:ac1725ba162c	200	+ ppp_mtime() + ((u32_t)TM1 << 16) + TM1;
segundo	0:ac1725ba162c	201	#else
segundo	0:ac1725ba162c	202	avRandomSeed += sys_jiffies(); /* XXX */
segundo	0:ac1725ba162c	203	#endif
segundo	0:ac1725ba162c	204
segundo	0:ac1725ba162c	205	/* Initialize the Borland random number generator. */
segundo	0:ac1725ba162c	206	srand((unsigned)avRandomSeed);
segundo	0:ac1725ba162c	207	}
segundo	0:ac1725ba162c	208
segundo	0:ac1725ba162c	209	/*
segundo	0:ac1725ba162c	210	* Randomize our random seed value. Here we use the fact that
segundo	0:ac1725ba162c	211	* this function is called at truely random times by the polling
segundo	0:ac1725ba162c	212	* and network functions. Here we only get 16 bits of new random
segundo	0:ac1725ba162c	213	* value but we use the previous value to randomize the other 16
segundo	0:ac1725ba162c	214	* bits.
segundo	0:ac1725ba162c	215	*/
segundo	0:ac1725ba162c	216	void
segundo	0:ac1725ba162c	217	avRandomize(void)
segundo	0:ac1725ba162c	218	{
segundo	0:ac1725ba162c	219	static u32_t last_jiffies;
segundo	0:ac1725ba162c	220
segundo	0:ac1725ba162c	221	if (!avRandomized) {
segundo	0:ac1725ba162c	222	avRandomized = !0;
segundo	0:ac1725ba162c	223	avRandomInit();
segundo	0:ac1725ba162c	224	/* The initialization function also updates the seed. */
segundo	0:ac1725ba162c	225	} else {
segundo	0:ac1725ba162c	226	/* avRandomSeed += (avRandomSeed << 16) + TM1; */
segundo	0:ac1725ba162c	227	avRandomSeed += (sys_jiffies() - last_jiffies); /* XXX */
segundo	0:ac1725ba162c	228	}
segundo	0:ac1725ba162c	229	last_jiffies = sys_jiffies();
segundo	0:ac1725ba162c	230	}
segundo	0:ac1725ba162c	231
segundo	0:ac1725ba162c	232	/*
segundo	0:ac1725ba162c	233	* Return a new random number.
segundo	0:ac1725ba162c	234	* Here we use the Borland rand() function to supply a pseudo random
segundo	0:ac1725ba162c	235	* number which we make truely random by combining it with our own
segundo	0:ac1725ba162c	236	* seed which is randomized by truely random events.
segundo	0:ac1725ba162c	237	* Thus the numbers will be truely random unless there have been no
segundo	0:ac1725ba162c	238	* operator or network events in which case it will be pseudo random
segundo	0:ac1725ba162c	239	* seeded by the real time clock.
segundo	0:ac1725ba162c	240	*/
segundo	0:ac1725ba162c	241	u32_t
segundo	0:ac1725ba162c	242	avRandom()
segundo	0:ac1725ba162c	243	{
segundo	0:ac1725ba162c	244	return ((((u32_t)rand() << 16) + rand()) + avRandomSeed);
segundo	0:ac1725ba162c	245	}
segundo	0:ac1725ba162c	246
segundo	0:ac1725ba162c	247	#endif /* MD5_SUPPORT */
segundo	0:ac1725ba162c	248
segundo	0:ac1725ba162c	249	#endif /* PPP_SUPPORT */

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Type:	Library
Created:	09 Nov 2010
Imports:	3034
Forks:	1
Commits:	8
Dependents:	42
Dependencies:	0
Followers:	27

lwip/netif/ppp/randm.c@0:ac1725ba162c, 2010-11-09 (annotated)

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