xref: /freebsd/sys/netinet6/ip6_id.c (revision eedc7fd9e87e86d636304611a29e53cecb3a57a1)
1caf43b02SWarner Losh /*-
28373d51dSHajimu UMEMOTO  * Copyright (C) 2003 WIDE Project.
38373d51dSHajimu UMEMOTO  * All rights reserved.
48373d51dSHajimu UMEMOTO  *
58373d51dSHajimu UMEMOTO  * Redistribution and use in source and binary forms, with or without
68373d51dSHajimu UMEMOTO  * modification, are permitted provided that the following conditions
78373d51dSHajimu UMEMOTO  * are met:
88373d51dSHajimu UMEMOTO  * 1. Redistributions of source code must retain the above copyright
98373d51dSHajimu UMEMOTO  *    notice, this list of conditions and the following disclaimer.
108373d51dSHajimu UMEMOTO  * 2. Redistributions in binary form must reproduce the above copyright
118373d51dSHajimu UMEMOTO  *    notice, this list of conditions and the following disclaimer in the
128373d51dSHajimu UMEMOTO  *    documentation and/or other materials provided with the distribution.
138373d51dSHajimu UMEMOTO  * 3. Neither the name of the project nor the names of its contributors
148373d51dSHajimu UMEMOTO  *    may be used to endorse or promote products derived from this software
158373d51dSHajimu UMEMOTO  *    without specific prior written permission.
168373d51dSHajimu UMEMOTO  *
178373d51dSHajimu UMEMOTO  * THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND
188373d51dSHajimu UMEMOTO  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
198373d51dSHajimu UMEMOTO  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
208373d51dSHajimu UMEMOTO  * ARE DISCLAIMED.  IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE
218373d51dSHajimu UMEMOTO  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
228373d51dSHajimu UMEMOTO  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
238373d51dSHajimu UMEMOTO  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
248373d51dSHajimu UMEMOTO  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
258373d51dSHajimu UMEMOTO  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
268373d51dSHajimu UMEMOTO  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
278373d51dSHajimu UMEMOTO  * SUCH DAMAGE.
28b48287a3SDavid E. O'Brien  *
29b48287a3SDavid E. O'Brien  *	$KAME: ip6_id.c,v 1.13 2003/09/16 09:11:19 itojun Exp $
308373d51dSHajimu UMEMOTO  */
318373d51dSHajimu UMEMOTO 
32caf43b02SWarner Losh /*-
338373d51dSHajimu UMEMOTO  * Copyright 1998 Niels Provos <provos@citi.umich.edu>
348373d51dSHajimu UMEMOTO  * All rights reserved.
358373d51dSHajimu UMEMOTO  *
368373d51dSHajimu UMEMOTO  * Theo de Raadt <deraadt@openbsd.org> came up with the idea of using
378373d51dSHajimu UMEMOTO  * such a mathematical system to generate more random (yet non-repeating)
388373d51dSHajimu UMEMOTO  * ids to solve the resolver/named problem.  But Niels designed the
398373d51dSHajimu UMEMOTO  * actual system based on the constraints.
408373d51dSHajimu UMEMOTO  *
418373d51dSHajimu UMEMOTO  * Redistribution and use in source and binary forms, with or without
428373d51dSHajimu UMEMOTO  * modification, are permitted provided that the following conditions
438373d51dSHajimu UMEMOTO  * are met:
448373d51dSHajimu UMEMOTO  * 1. Redistributions of source code must retain the above copyright
458373d51dSHajimu UMEMOTO  *    notice, this list of conditions and the following disclaimer.
468373d51dSHajimu UMEMOTO  * 2. Redistributions in binary form must reproduce the above copyright
478373d51dSHajimu UMEMOTO  *    notice, this list of conditions and the following disclaimer in the
488373d51dSHajimu UMEMOTO  *    documentation and/or other materials provided with the distribution.
498373d51dSHajimu UMEMOTO  * 3. All advertising materials mentioning features or use of this software
508373d51dSHajimu UMEMOTO  *    must display the following acknowledgement:
518373d51dSHajimu UMEMOTO  *      This product includes software developed by Niels Provos.
528373d51dSHajimu UMEMOTO  * 4. The name of the author may not be used to endorse or promote products
538373d51dSHajimu UMEMOTO  *    derived from this software without specific prior written permission.
548373d51dSHajimu UMEMOTO  *
558373d51dSHajimu UMEMOTO  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
568373d51dSHajimu UMEMOTO  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
578373d51dSHajimu UMEMOTO  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
588373d51dSHajimu UMEMOTO  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
598373d51dSHajimu UMEMOTO  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
608373d51dSHajimu UMEMOTO  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
618373d51dSHajimu UMEMOTO  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
628373d51dSHajimu UMEMOTO  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
638373d51dSHajimu UMEMOTO  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
648373d51dSHajimu UMEMOTO  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
65b48287a3SDavid E. O'Brien  *
66b48287a3SDavid E. O'Brien  * $OpenBSD: ip_id.c,v 1.6 2002/03/15 18:19:52 millert Exp $
678373d51dSHajimu UMEMOTO  */
688373d51dSHajimu UMEMOTO 
69b48287a3SDavid E. O'Brien #include <sys/cdefs.h>
70b48287a3SDavid E. O'Brien __FBSDID("$FreeBSD$");
71b48287a3SDavid E. O'Brien 
728373d51dSHajimu UMEMOTO /*
738373d51dSHajimu UMEMOTO  * seed = random (bits - 1) bit
748373d51dSHajimu UMEMOTO  * n = prime, g0 = generator to n,
758373d51dSHajimu UMEMOTO  * j = random so that gcd(j,n-1) == 1
768373d51dSHajimu UMEMOTO  * g = g0^j mod n will be a generator again.
778373d51dSHajimu UMEMOTO  *
788373d51dSHajimu UMEMOTO  * X[0] = random seed.
798373d51dSHajimu UMEMOTO  * X[n] = a*X[n-1]+b mod m is a Linear Congruential Generator
808373d51dSHajimu UMEMOTO  * with a = 7^(even random) mod m,
818373d51dSHajimu UMEMOTO  *      b = random with gcd(b,m) == 1
828373d51dSHajimu UMEMOTO  *      m = constant and a maximal period of m-1.
838373d51dSHajimu UMEMOTO  *
848373d51dSHajimu UMEMOTO  * The transaction id is determined by:
858373d51dSHajimu UMEMOTO  * id[n] = seed xor (g^X[n] mod n)
868373d51dSHajimu UMEMOTO  *
878373d51dSHajimu UMEMOTO  * Effectivly the id is restricted to the lower (bits - 1) bits, thus
888373d51dSHajimu UMEMOTO  * yielding two different cycles by toggling the msb on and off.
898373d51dSHajimu UMEMOTO  * This avoids reuse issues caused by reseeding.
908373d51dSHajimu UMEMOTO  */
918373d51dSHajimu UMEMOTO 
928373d51dSHajimu UMEMOTO #include <sys/types.h>
938373d51dSHajimu UMEMOTO #include <sys/param.h>
948373d51dSHajimu UMEMOTO #include <sys/kernel.h>
958373d51dSHajimu UMEMOTO #include <sys/socket.h>
968373d51dSHajimu UMEMOTO #include <sys/libkern.h>
978373d51dSHajimu UMEMOTO 
988373d51dSHajimu UMEMOTO #include <net/if.h>
998373d51dSHajimu UMEMOTO #include <net/route.h>
100*eedc7fd9SGleb Smirnoff #include <net/vnet.h>
1018373d51dSHajimu UMEMOTO #include <netinet/in.h>
1028373d51dSHajimu UMEMOTO #include <netinet/ip6.h>
1038373d51dSHajimu UMEMOTO #include <netinet6/ip6_var.h>
1048373d51dSHajimu UMEMOTO 
1058373d51dSHajimu UMEMOTO #ifndef INT32_MAX
1068373d51dSHajimu UMEMOTO #define INT32_MAX	0x7fffffffU
1078373d51dSHajimu UMEMOTO #endif
1088373d51dSHajimu UMEMOTO 
1098373d51dSHajimu UMEMOTO struct randomtab {
1108373d51dSHajimu UMEMOTO 	const int	ru_bits; /* resulting bits */
1118373d51dSHajimu UMEMOTO 	const long	ru_out;	/* Time after wich will be reseeded */
1128373d51dSHajimu UMEMOTO 	const u_int32_t ru_max;	/* Uniq cycle, avoid blackjack prediction */
1138373d51dSHajimu UMEMOTO 	const u_int32_t ru_gen;	/* Starting generator */
1148373d51dSHajimu UMEMOTO 	const u_int32_t ru_n;	/* ru_n: prime, ru_n - 1: product of pfacts[] */
1158373d51dSHajimu UMEMOTO 	const u_int32_t ru_agen; /* determine ru_a as ru_agen^(2*rand) */
1168373d51dSHajimu UMEMOTO 	const u_int32_t ru_m;	/* ru_m = 2^x*3^y */
1178373d51dSHajimu UMEMOTO 	const u_int32_t pfacts[4];	/* factors of ru_n */
1188373d51dSHajimu UMEMOTO 
1198373d51dSHajimu UMEMOTO 	u_int32_t ru_counter;
1208373d51dSHajimu UMEMOTO 	u_int32_t ru_msb;
1218373d51dSHajimu UMEMOTO 
1228373d51dSHajimu UMEMOTO 	u_int32_t ru_x;
1238373d51dSHajimu UMEMOTO 	u_int32_t ru_seed, ru_seed2;
1248373d51dSHajimu UMEMOTO 	u_int32_t ru_a, ru_b;
1258373d51dSHajimu UMEMOTO 	u_int32_t ru_g;
1268373d51dSHajimu UMEMOTO 	long ru_reseed;
1278373d51dSHajimu UMEMOTO };
1288373d51dSHajimu UMEMOTO 
1298373d51dSHajimu UMEMOTO static struct randomtab randomtab_32 = {
1308373d51dSHajimu UMEMOTO 	32,			/* resulting bits */
1318373d51dSHajimu UMEMOTO 	180,			/* Time after wich will be reseeded */
1328373d51dSHajimu UMEMOTO 	1000000000,		/* Uniq cycle, avoid blackjack prediction */
1338373d51dSHajimu UMEMOTO 	2,			/* Starting generator */
1348373d51dSHajimu UMEMOTO 	2147483629,		/* RU_N-1 = 2^2*3^2*59652323 */
1358373d51dSHajimu UMEMOTO 	7,			/* determine ru_a as RU_AGEN^(2*rand) */
1368373d51dSHajimu UMEMOTO 	1836660096,		/* RU_M = 2^7*3^15 - don't change */
1378373d51dSHajimu UMEMOTO 	{ 2, 3, 59652323, 0 },	/* factors of ru_n */
1388373d51dSHajimu UMEMOTO };
1398373d51dSHajimu UMEMOTO 
1405d405368SHajimu UMEMOTO static struct randomtab randomtab_20 = {
1415d405368SHajimu UMEMOTO 	20,			/* resulting bits */
1425d405368SHajimu UMEMOTO 	180,			/* Time after wich will be reseeded */
1435d405368SHajimu UMEMOTO 	200000,			/* Uniq cycle, avoid blackjack prediction */
1445d405368SHajimu UMEMOTO 	2,			/* Starting generator */
1455d405368SHajimu UMEMOTO 	524269,			/* RU_N-1 = 2^2*3^2*14563 */
1465d405368SHajimu UMEMOTO 	7,			/* determine ru_a as RU_AGEN^(2*rand) */
1475d405368SHajimu UMEMOTO 	279936,			/* RU_M = 2^7*3^7 - don't change */
1485d405368SHajimu UMEMOTO 	{ 2, 3, 14563, 0 },	/* factors of ru_n */
1495d405368SHajimu UMEMOTO };
1505d405368SHajimu UMEMOTO 
1518373d51dSHajimu UMEMOTO static u_int32_t pmod(u_int32_t, u_int32_t, u_int32_t);
1528373d51dSHajimu UMEMOTO static void initid(struct randomtab *);
1538373d51dSHajimu UMEMOTO static u_int32_t randomid(struct randomtab *);
1548373d51dSHajimu UMEMOTO 
1558373d51dSHajimu UMEMOTO /*
1568373d51dSHajimu UMEMOTO  * Do a fast modular exponation, returned value will be in the range
1578373d51dSHajimu UMEMOTO  * of 0 - (mod-1)
1588373d51dSHajimu UMEMOTO  */
1598373d51dSHajimu UMEMOTO static u_int32_t
1608373d51dSHajimu UMEMOTO pmod(u_int32_t gen, u_int32_t expo, u_int32_t mod)
1618373d51dSHajimu UMEMOTO {
1628373d51dSHajimu UMEMOTO 	u_int64_t s, t, u;
1638373d51dSHajimu UMEMOTO 
1648373d51dSHajimu UMEMOTO 	s = 1;
1658373d51dSHajimu UMEMOTO 	t = gen;
1668373d51dSHajimu UMEMOTO 	u = expo;
1678373d51dSHajimu UMEMOTO 
1688373d51dSHajimu UMEMOTO 	while (u) {
1698373d51dSHajimu UMEMOTO 		if (u & 1)
1708373d51dSHajimu UMEMOTO 			s = (s * t) % mod;
1718373d51dSHajimu UMEMOTO 		u >>= 1;
1728373d51dSHajimu UMEMOTO 		t = (t * t) % mod;
1738373d51dSHajimu UMEMOTO 	}
1748373d51dSHajimu UMEMOTO 	return (s);
1758373d51dSHajimu UMEMOTO }
1768373d51dSHajimu UMEMOTO 
1778373d51dSHajimu UMEMOTO /*
1788373d51dSHajimu UMEMOTO  * Initalizes the seed and chooses a suitable generator. Also toggles
1798373d51dSHajimu UMEMOTO  * the msb flag. The msb flag is used to generate two distinct
1808373d51dSHajimu UMEMOTO  * cycles of random numbers and thus avoiding reuse of ids.
1818373d51dSHajimu UMEMOTO  *
1828373d51dSHajimu UMEMOTO  * This function is called from id_randomid() when needed, an
1838373d51dSHajimu UMEMOTO  * application does not have to worry about it.
1848373d51dSHajimu UMEMOTO  */
1858373d51dSHajimu UMEMOTO static void
1868373d51dSHajimu UMEMOTO initid(struct randomtab *p)
1878373d51dSHajimu UMEMOTO {
1888373d51dSHajimu UMEMOTO 	u_int32_t j, i;
1898373d51dSHajimu UMEMOTO 	int noprime = 1;
1908373d51dSHajimu UMEMOTO 
1918373d51dSHajimu UMEMOTO 	p->ru_x = arc4random() % p->ru_m;
1928373d51dSHajimu UMEMOTO 
1938373d51dSHajimu UMEMOTO 	/* (bits - 1) bits of random seed */
1948373d51dSHajimu UMEMOTO 	p->ru_seed = arc4random() & (~0U >> (32 - p->ru_bits + 1));
1958373d51dSHajimu UMEMOTO 	p->ru_seed2 = arc4random() & (~0U >> (32 - p->ru_bits + 1));
1968373d51dSHajimu UMEMOTO 
1978373d51dSHajimu UMEMOTO 	/* Determine the LCG we use */
1988373d51dSHajimu UMEMOTO 	p->ru_b = (arc4random() & (~0U >> (32 - p->ru_bits))) | 1;
1998373d51dSHajimu UMEMOTO 	p->ru_a = pmod(p->ru_agen,
2008373d51dSHajimu UMEMOTO 	    (arc4random() & (~0U >> (32 - p->ru_bits))) & (~1U), p->ru_m);
2018373d51dSHajimu UMEMOTO 	while (p->ru_b % 3 == 0)
2028373d51dSHajimu UMEMOTO 		p->ru_b += 2;
2038373d51dSHajimu UMEMOTO 
2048373d51dSHajimu UMEMOTO 	j = arc4random() % p->ru_n;
2058373d51dSHajimu UMEMOTO 
2068373d51dSHajimu UMEMOTO 	/*
2078373d51dSHajimu UMEMOTO 	 * Do a fast gcd(j, RU_N - 1), so we can find a j with
2088373d51dSHajimu UMEMOTO 	 * gcd(j, RU_N - 1) == 1, giving a new generator for
2098373d51dSHajimu UMEMOTO 	 * RU_GEN^j mod RU_N
2108373d51dSHajimu UMEMOTO 	 */
2118373d51dSHajimu UMEMOTO 	while (noprime) {
2128373d51dSHajimu UMEMOTO 		for (i = 0; p->pfacts[i] > 0; i++)
2138373d51dSHajimu UMEMOTO 			if (j % p->pfacts[i] == 0)
2148373d51dSHajimu UMEMOTO 				break;
2158373d51dSHajimu UMEMOTO 
2168373d51dSHajimu UMEMOTO 		if (p->pfacts[i] == 0)
2178373d51dSHajimu UMEMOTO 			noprime = 0;
2188373d51dSHajimu UMEMOTO 		else
2198373d51dSHajimu UMEMOTO 			j = (j + 1) % p->ru_n;
2208373d51dSHajimu UMEMOTO 	}
2218373d51dSHajimu UMEMOTO 
2228373d51dSHajimu UMEMOTO 	p->ru_g = pmod(p->ru_gen, j, p->ru_n);
2238373d51dSHajimu UMEMOTO 	p->ru_counter = 0;
2248373d51dSHajimu UMEMOTO 
2257d26db17SHiroki Sato 	p->ru_reseed = time_uptime + p->ru_out;
2268373d51dSHajimu UMEMOTO 	p->ru_msb = p->ru_msb ? 0 : (1U << (p->ru_bits - 1));
2278373d51dSHajimu UMEMOTO }
2288373d51dSHajimu UMEMOTO 
2298373d51dSHajimu UMEMOTO static u_int32_t
2308373d51dSHajimu UMEMOTO randomid(struct randomtab *p)
2318373d51dSHajimu UMEMOTO {
2328373d51dSHajimu UMEMOTO 	int i, n;
2338373d51dSHajimu UMEMOTO 	u_int32_t tmp;
2348373d51dSHajimu UMEMOTO 
2357d26db17SHiroki Sato 	if (p->ru_counter >= p->ru_max || time_uptime > p->ru_reseed)
2368373d51dSHajimu UMEMOTO 		initid(p);
2378373d51dSHajimu UMEMOTO 
2388373d51dSHajimu UMEMOTO 	tmp = arc4random();
2398373d51dSHajimu UMEMOTO 
2408373d51dSHajimu UMEMOTO 	/* Skip a random number of ids */
2418373d51dSHajimu UMEMOTO 	n = tmp & 0x3; tmp = tmp >> 2;
2428373d51dSHajimu UMEMOTO 	if (p->ru_counter + n >= p->ru_max)
2438373d51dSHajimu UMEMOTO 		initid(p);
2448373d51dSHajimu UMEMOTO 
2458373d51dSHajimu UMEMOTO 	for (i = 0; i <= n; i++) {
2468373d51dSHajimu UMEMOTO 		/* Linear Congruential Generator */
2478373d51dSHajimu UMEMOTO 		p->ru_x = (u_int32_t)((u_int64_t)p->ru_a * p->ru_x + p->ru_b) % p->ru_m;
2488373d51dSHajimu UMEMOTO 	}
2498373d51dSHajimu UMEMOTO 
2508373d51dSHajimu UMEMOTO 	p->ru_counter += i;
2518373d51dSHajimu UMEMOTO 
2528373d51dSHajimu UMEMOTO 	return (p->ru_seed ^ pmod(p->ru_g, p->ru_seed2 ^ p->ru_x, p->ru_n)) |
2538373d51dSHajimu UMEMOTO 	    p->ru_msb;
2548373d51dSHajimu UMEMOTO }
2558373d51dSHajimu UMEMOTO 
2568373d51dSHajimu UMEMOTO u_int32_t
2578373d51dSHajimu UMEMOTO ip6_randomid(void)
2588373d51dSHajimu UMEMOTO {
2598373d51dSHajimu UMEMOTO 
2608373d51dSHajimu UMEMOTO 	return randomid(&randomtab_32);
2618373d51dSHajimu UMEMOTO }
262672467ebSHajimu UMEMOTO 
263b79274baSHajimu UMEMOTO u_int32_t
264b79274baSHajimu UMEMOTO ip6_randomflowlabel(void)
265b79274baSHajimu UMEMOTO {
266b79274baSHajimu UMEMOTO 
267b79274baSHajimu UMEMOTO 	return randomid(&randomtab_20) & 0xfffff;
268b79274baSHajimu UMEMOTO }
269