1/* 2 * Copyright (c) 2009 Apple Inc. All rights reserved. 3 * 4 * @APPLE_OSREFERENCE_LICENSE_HEADER_START@ 5 * 6 * This file contains Original Code and/or Modifications of Original Code 7 * as defined in and that are subject to the Apple Public Source License 8 * Version 2.0 (the 'License'). You may not use this file except in 9 * compliance with the License. The rights granted to you under the License 10 * may not be used to create, or enable the creation or redistribution of, 11 * unlawful or unlicensed copies of an Apple operating system, or to 12 * circumvent, violate, or enable the circumvention or violation of, any 13 * terms of an Apple operating system software license agreement. 14 * 15 * Please obtain a copy of the License at 16 * http://www.opensource.apple.com/apsl/ and read it before using this file. 17 * 18 * The Original Code and all software distributed under the License are 19 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER 20 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES, 21 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY, 22 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT. 23 * Please see the License for the specific language governing rights and 24 * limitations under the License. 25 * 26 * @APPLE_OSREFERENCE_LICENSE_HEADER_END@ 27 */ 28 29/*- 30 * Copyright (C) 2003 WIDE Project. 31 * All rights reserved. 32 * 33 * Redistribution and use in source and binary forms, with or without 34 * modification, are permitted provided that the following conditions 35 * are met: 36 * 1. Redistributions of source code must retain the above copyright 37 * notice, this list of conditions and the following disclaimer. 38 * 2. Redistributions in binary form must reproduce the above copyright 39 * notice, this list of conditions and the following disclaimer in the 40 * documentation and/or other materials provided with the distribution. 41 * 3. Neither the name of the project nor the names of its contributors 42 * may be used to endorse or promote products derived from this software 43 * without specific prior written permission. 44 * 45 * THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND 46 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 47 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 48 * ARE DISCLAIMED. IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE 49 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 50 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 51 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 52 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 53 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 54 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 55 * SUCH DAMAGE. 56 * 57 * $KAME: ip6_id.c,v 1.13 2003/09/16 09:11:19 itojun Exp $ 58 */ 59 60/*- 61 * Copyright 1998 Niels Provos <provos@citi.umich.edu> 62 * All rights reserved. 63 * 64 * Theo de Raadt <deraadt@openbsd.org> came up with the idea of using 65 * such a mathematical system to generate more random (yet non-repeating) 66 * ids to solve the resolver/named problem. But Niels designed the 67 * actual system based on the constraints. 68 * 69 * Redistribution and use in source and binary forms, with or without 70 * modification, are permitted provided that the following conditions 71 * are met: 72 * 1. Redistributions of source code must retain the above copyright 73 * notice, this list of conditions and the following disclaimer. 74 * 2. Redistributions in binary form must reproduce the above copyright 75 * notice, this list of conditions and the following disclaimer in the 76 * documentation and/or other materials provided with the distribution. 77 * 3. All advertising materials mentioning features or use of this software 78 * must display the following acknowledgement: 79 * This product includes software developed by Niels Provos. 80 * 4. The name of the author may not be used to endorse or promote products 81 * derived from this software without specific prior written permission. 82 * 83 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 84 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 85 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 86 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 87 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 88 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 89 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 90 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 91 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 92 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 93 * 94 * $OpenBSD: ip_id.c,v 1.6 2002/03/15 18:19:52 millert Exp $ 95 */ 96 97#include <sys/cdefs.h> 98 99/* 100 * seed = random (bits - 1) bit 101 * n = prime, g0 = generator to n, 102 * j = random so that gcd(j,n-1) == 1 103 * g = g0^j mod n will be a generator again. 104 * 105 * X[0] = random seed. 106 * X[n] = a*X[n-1]+b mod m is a Linear Congruential Generator 107 * with a = 7^(even random) mod m, 108 * b = random with gcd(b,m) == 1 109 * m = constant and a maximal period of m-1. 110 * 111 * The transaction id is determined by: 112 * id[n] = seed xor (g^X[n] mod n) 113 * 114 * Effectivly the id is restricted to the lower (bits - 1) bits, thus 115 * yielding two different cycles by toggling the msb on and off. 116 * This avoids reuse issues caused by reseeding. 117 */ 118 119#include <sys/types.h> 120#include <sys/socket.h> 121#include <sys/param.h> 122#include <sys/time.h> 123#include <sys/kernel.h> 124#include <sys/random.h> 125#include <libkern/libkern.h> 126 127#include <net/if.h> 128#include <net/route.h> 129#include <netinet/in.h> 130#include <netinet/ip6.h> 131#include <netinet6/ip6_var.h> 132 133#ifndef INT32_MAX 134#define INT32_MAX 0x7fffffffU 135#endif 136 137struct randomtab { 138 const int ru_bits; /* resulting bits */ 139 const long ru_out; /* Time after wich will be reseeded */ 140 const u_int32_t ru_max; /* Uniq cycle, avoid blackjack prediction */ 141 const u_int32_t ru_gen; /* Starting generator */ 142 const u_int32_t ru_n; /* ru_n: prime, ru_n - 1: product of pfacts[] */ 143 const u_int32_t ru_agen; /* determine ru_a as ru_agen^(2*rand) */ 144 const u_int32_t ru_m; /* ru_m = 2^x*3^y */ 145 const u_int32_t pfacts[4]; /* factors of ru_n */ 146 147 u_int32_t ru_counter; 148 u_int32_t ru_msb; 149 150 u_int32_t ru_x; 151 u_int32_t ru_seed, ru_seed2; 152 u_int32_t ru_a, ru_b; 153 u_int32_t ru_g; 154 long ru_reseed; 155}; 156 157static struct randomtab randomtab_32 = { 158 32, /* resulting bits */ 159 180, /* Time after wich will be reseeded */ 160 1000000000, /* Uniq cycle, avoid blackjack prediction */ 161 2, /* Starting generator */ 162 2147483629, /* RU_N-1 = 2^2*3^2*59652323 */ 163 7, /* determine ru_a as RU_AGEN^(2*rand) */ 164 1836660096, /* RU_M = 2^7*3^15 - don't change */ 165 { 2, 3, 59652323, 0 }, /* factors of ru_n */ 166 0, 0, 0, 0, 0, 0, 0, 0, 0 167}; 168 169static struct randomtab randomtab_20 = { 170 20, /* resulting bits */ 171 180, /* Time after wich will be reseeded */ 172 200000, /* Uniq cycle, avoid blackjack prediction */ 173 2, /* Starting generator */ 174 524269, /* RU_N-1 = 2^2*3^2*14563 */ 175 7, /* determine ru_a as RU_AGEN^(2*rand) */ 176 279936, /* RU_M = 2^7*3^7 - don't change */ 177 { 2, 3, 14563, 0 }, /* factors of ru_n */ 178 0, 0, 0, 0, 0, 0, 0, 0, 0 179}; 180 181static u_int32_t pmod(u_int32_t, u_int32_t, u_int32_t); 182static void initid(struct randomtab *); 183static u_int32_t randomid(struct randomtab *); 184 185/* 186 * Do a fast modular exponation, returned value will be in the range 187 * of 0 - (mod-1) 188 */ 189static u_int32_t 190pmod(u_int32_t gen, u_int32_t expo, u_int32_t mod) 191{ 192 u_int64_t s, t, u; 193 194 s = 1; 195 t = gen; 196 u = expo; 197 198 while (u) { 199 if (u & 1) 200 s = (s * t) % mod; 201 u >>= 1; 202 t = (t * t) % mod; 203 } 204 return (s); 205} 206 207/* 208 * Initalizes the seed and chooses a suitable generator. Also toggles 209 * the msb flag. The msb flag is used to generate two distinct 210 * cycles of random numbers and thus avoiding reuse of ids. 211 * 212 * This function is called from id_randomid() when needed, an 213 * application does not have to worry about it. 214 */ 215static void 216initid(struct randomtab *p) 217{ 218 u_int32_t j, i; 219 int noprime = 1; 220 struct timeval timenow; 221 222 getmicrotime(&timenow); 223 224 p->ru_x = random() % p->ru_m; 225 226 /* (bits - 1) bits of random seed */ 227 p->ru_seed = random() & (~0U >> (32 - p->ru_bits + 1)); 228 p->ru_seed2 = random() & (~0U >> (32 - p->ru_bits + 1)); 229 230 /* Determine the LCG we use */ 231 p->ru_b = (random() & (~0U >> (32 - p->ru_bits))) | 1; 232 p->ru_a = pmod(p->ru_agen, 233 (random() & (~0U >> (32 - p->ru_bits))) & (~1U), p->ru_m); 234 while (p->ru_b % 3 == 0) 235 p->ru_b += 2; 236 237 j = random() % p->ru_n; 238 239 /* 240 * Do a fast gcd(j, RU_N - 1), so we can find a j with 241 * gcd(j, RU_N - 1) == 1, giving a new generator for 242 * RU_GEN^j mod RU_N 243 */ 244 while (noprime) { 245 for (i = 0; p->pfacts[i] > 0; i++) 246 if (j % p->pfacts[i] == 0) 247 break; 248 249 if (p->pfacts[i] == 0) 250 noprime = 0; 251 else 252 j = (j + 1) % p->ru_n; 253 } 254 255 p->ru_g = pmod(p->ru_gen, j, p->ru_n); 256 p->ru_counter = 0; 257 258 p->ru_reseed = timenow.tv_sec + p->ru_out; 259 p->ru_msb = p->ru_msb ? 0 : (1U << (p->ru_bits - 1)); 260} 261 262static u_int32_t 263randomid(struct randomtab *p) 264{ 265 int i, n; 266 u_int32_t tmp; 267 struct timeval timenow; 268 269 getmicrotime(&timenow); 270 271 if (p->ru_counter >= p->ru_max || timenow.tv_sec > p->ru_reseed) 272 initid(p); 273 274 tmp = random(); 275 276 /* Skip a random number of ids */ 277 n = tmp & 0x3; tmp = tmp >> 2; 278 if (p->ru_counter + n >= p->ru_max) 279 initid(p); 280 281 for (i = 0; i <= n; i++) { 282 /* Linear Congruential Generator */ 283 p->ru_x = (u_int32_t)((u_int64_t)p->ru_a * p->ru_x + p->ru_b) % p->ru_m; 284 } 285 286 p->ru_counter += i; 287 288 return (p->ru_seed ^ pmod(p->ru_g, p->ru_seed2 ^ p->ru_x, p->ru_n)) | 289 p->ru_msb; 290} 291 292u_int32_t 293ip6_randomid(void) 294{ 295 296 return randomid(&randomtab_32); 297} 298 299u_int32_t 300ip6_randomflowlabel(void) 301{ 302 303 return randomid(&randomtab_20) & 0xfffff; 304} 305