1/* 2 * Copyright (c) 2009-2013 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 58/*- 59 * Copyright 1998 Niels Provos <provos@citi.umich.edu> 60 * All rights reserved. 61 * 62 * Theo de Raadt <deraadt@openbsd.org> came up with the idea of using 63 * such a mathematical system to generate more random (yet non-repeating) 64 * ids to solve the resolver/named problem. But Niels designed the 65 * actual system based on the constraints. 66 * 67 * Redistribution and use in source and binary forms, with or without 68 * modification, are permitted provided that the following conditions 69 * are met: 70 * 1. Redistributions of source code must retain the above copyright 71 * notice, this list of conditions and the following disclaimer. 72 * 2. Redistributions in binary form must reproduce the above copyright 73 * notice, this list of conditions and the following disclaimer in the 74 * documentation and/or other materials provided with the distribution. 75 * 3. All advertising materials mentioning features or use of this software 76 * must display the following acknowledgement: 77 * This product includes software developed by Niels Provos. 78 * 4. The name of the author may not be used to endorse or promote products 79 * derived from this software without specific prior written permission. 80 * 81 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 82 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 83 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 84 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 85 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 86 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 87 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 88 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 89 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 90 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 91 */ 92 93#include <sys/cdefs.h> 94 95/* 96 * seed = random (bits - 1) bit 97 * n = prime, g0 = generator to n, 98 * j = random so that gcd(j,n-1) == 1 99 * g = g0^j mod n will be a generator again. 100 * 101 * X[0] = random seed. 102 * X[n] = a*X[n-1]+b mod m is a Linear Congruential Generator 103 * with a = 7^(even random) mod m, 104 * b = random with gcd(b,m) == 1 105 * m = constant and a maximal period of m-1. 106 * 107 * The transaction id is determined by: 108 * id[n] = seed xor (g^X[n] mod n) 109 * 110 * Effectivly the id is restricted to the lower (bits - 1) bits, thus 111 * yielding two different cycles by toggling the msb on and off. 112 * This avoids reuse issues caused by reseeding. 113 */ 114 115#include <sys/types.h> 116#include <sys/socket.h> 117#include <sys/param.h> 118#include <sys/time.h> 119#include <sys/kernel.h> 120#include <sys/random.h> 121#include <sys/protosw.h> 122#include <libkern/libkern.h> 123#include <dev/random/randomdev.h> 124 125#include <net/if.h> 126#include <net/route.h> 127#include <netinet/in.h> 128#include <netinet/ip6.h> 129#include <netinet6/ip6_var.h> 130 131struct randomtab { 132 const int ru_bits; /* resulting bits */ 133 const long ru_out; /* Time after wich will be reseeded */ 134 const u_int32_t ru_max; /* Uniq cycle, avoid blackjack prediction */ 135 const u_int32_t ru_gen; /* Starting generator */ 136 const u_int32_t ru_n; /* ru_n: prime, ru_n - 1: product of pfacts[] */ 137 const u_int32_t ru_agen; /* determine ru_a as ru_agen^(2*rand) */ 138 const u_int32_t ru_m; /* ru_m = 2^x*3^y */ 139 const u_int32_t pfacts[4]; /* factors of ru_n */ 140 141 u_int32_t ru_counter; 142 u_int32_t ru_msb; 143 144 u_int32_t ru_x; 145 u_int32_t ru_seed, ru_seed2; 146 u_int32_t ru_a, ru_b; 147 u_int32_t ru_g; 148 long ru_reseed; 149}; 150 151static struct randomtab randomtab_32 = { 152 32, /* resulting bits */ 153 180, /* Time after wich will be reseeded */ 154 1000000000, /* Uniq cycle, avoid blackjack prediction */ 155 2, /* Starting generator */ 156 2147483629, /* RU_N-1 = 2^2*3^2*59652323 */ 157 7, /* determine ru_a as RU_AGEN^(2*rand) */ 158 1836660096, /* RU_M = 2^7*3^15 - don't change */ 159 { 2, 3, 59652323, 0 }, /* factors of ru_n */ 160 0, 0, 0, 0, 0, 0, 0, 0, 0 161}; 162 163static struct randomtab randomtab_20 = { 164 20, /* resulting bits */ 165 180, /* Time after wich will be reseeded */ 166 200000, /* Uniq cycle, avoid blackjack prediction */ 167 2, /* Starting generator */ 168 524269, /* RU_N-1 = 2^2*3^2*14563 */ 169 7, /* determine ru_a as RU_AGEN^(2*rand) */ 170 279936, /* RU_M = 2^7*3^7 - don't change */ 171 { 2, 3, 14563, 0 }, /* factors of ru_n */ 172 0, 0, 0, 0, 0, 0, 0, 0, 0 173}; 174 175static u_int32_t pmod(u_int32_t, u_int32_t, u_int32_t); 176static void initid(struct randomtab *); 177static u_int32_t randomid(struct randomtab *); 178 179/* 180 * Do a fast modular exponation, returned value will be in the range 181 * of 0 - (mod-1) 182 */ 183static u_int32_t 184pmod(u_int32_t gen, u_int32_t expo, u_int32_t mod) 185{ 186 u_int64_t s, t, u; 187 188 s = 1; 189 t = gen; 190 u = expo; 191 192 while (u) { 193 if (u & 1) 194 s = (s * t) % mod; 195 u >>= 1; 196 t = (t * t) % mod; 197 } 198 return (s); 199} 200 201/* 202 * Initalizes the seed and chooses a suitable generator. Also toggles 203 * the msb flag. The msb flag is used to generate two distinct 204 * cycles of random numbers and thus avoiding reuse of ids. 205 * 206 * This function is called from id_randomid() when needed, an 207 * application does not have to worry about it. 208 */ 209static void 210initid(struct randomtab *p) 211{ 212 time_t curtime = (time_t)net_uptime(); 213 u_int32_t j, i; 214 int noprime = 1; 215 216 p->ru_x = RandomULong() % p->ru_m; 217 218 /* (bits - 1) bits of random seed */ 219 p->ru_seed = RandomULong() & (~0U >> (32 - p->ru_bits + 1)); 220 p->ru_seed2 = RandomULong() & (~0U >> (32 - p->ru_bits + 1)); 221 222 /* Determine the LCG we use */ 223 p->ru_b = (RandomULong() & (~0U >> (32 - p->ru_bits))) | 1; 224 p->ru_a = pmod(p->ru_agen, 225 (RandomULong() & (~0U >> (32 - p->ru_bits))) & (~1U), p->ru_m); 226 while (p->ru_b % 3 == 0) 227 p->ru_b += 2; 228 229 j = RandomULong() % p->ru_n; 230 231 /* 232 * Do a fast gcd(j, RU_N - 1), so we can find a j with 233 * gcd(j, RU_N - 1) == 1, giving a new generator for 234 * RU_GEN^j mod RU_N 235 */ 236 while (noprime) { 237 for (i = 0; p->pfacts[i] > 0; i++) 238 if (j % p->pfacts[i] == 0) 239 break; 240 241 if (p->pfacts[i] == 0) 242 noprime = 0; 243 else 244 j = (j + 1) % p->ru_n; 245 } 246 247 p->ru_g = pmod(p->ru_gen, j, p->ru_n); 248 p->ru_counter = 0; 249 250 p->ru_reseed = curtime + p->ru_out; 251 p->ru_msb = p->ru_msb ? 0 : (1U << (p->ru_bits - 1)); 252} 253 254static u_int32_t 255randomid(struct randomtab *p) 256{ 257 time_t curtime = (time_t)net_uptime(); 258 int i, n; 259 u_int32_t tmp; 260 261 if (p->ru_counter >= p->ru_max || curtime > p->ru_reseed) 262 initid(p); 263 264 tmp = RandomULong(); 265 266 /* Skip a random number of ids */ 267 n = tmp & 0x3; tmp = tmp >> 2; 268 if (p->ru_counter + n >= p->ru_max) 269 initid(p); 270 271 for (i = 0; i <= n; i++) { 272 /* Linear Congruential Generator */ 273 p->ru_x = ((u_int64_t)p->ru_a * p->ru_x + p->ru_b) % p->ru_m; 274 } 275 276 p->ru_counter += i; 277 278 return ((p->ru_seed ^ pmod(p->ru_g, p->ru_seed2 ^ p->ru_x, p->ru_n)) | 279 p->ru_msb); 280} 281 282u_int32_t 283ip6_randomid(void) 284{ 285 286 return (randomid(&randomtab_32)); 287} 288 289u_int32_t 290ip6_randomflowlabel(void) 291{ 292 293 return (randomid(&randomtab_20) & 0xfffff); 294} 295