bsd/netinet6/ip6_id.c

   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
 137 struct 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
 157 static 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
 169 static 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
 181 static u_int32_t pmod(u_int32_t, u_int32_t, u_int32_t);
 182 static void initid(struct randomtab *);
 183 static 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  */
 189 static u_int32_t
 190 pmod(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  */
 215 static void
 216 initid(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
 262 static u_int32_t
 263 randomid(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
 292 u_int32_t
 293 ip6_randomid(void)
 294 {
 295
 296         return randomid(&randomtab_32);
 297 }
 298
 299 u_int32_t
 300 ip6_randomflowlabel(void)
 301 {
 302
 303         return randomid(&randomtab_20) & 0xfffff;
 304 }