/* $NetBSD: randomid.c,v 1.16 2022/05/15 20:37:50 andvar Exp $ */ /* $KAME: ip6_id.c,v 1.8 2003/09/06 13:41:06 itojun Exp $ */ /* $OpenBSD: ip_id.c,v 1.6 2002/03/15 18:19:52 millert Exp $ */ /* * Copyright (C) 2003 WIDE Project. * All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * 3. Neither the name of the project nor the names of its contributors * may be used to endorse or promote products derived from this software * without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. */ /* * Copyright 1998 Niels Provos <provos@citi.umich.edu> * All rights reserved. * * Theo de Raadt <deraadt@openbsd.org> came up with the idea of using * such a mathematical system to generate more random (yet non-repeating) * ids to solve the resolver/named problem. But Niels designed the * actual system based on the constraints. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */ /* * seed = random (bits - 1) bit * n = prime, g0 = generator to n, * j = random so that gcd(j,n-1) == 1 * g = g0^j mod n will be a generator again. * * X[0] = random seed. * X[n] = a*X[n-1]+b mod m is a Linear Congruential Generator * with a = 7^(even random) mod m, * b = random with gcd(b,m) == 1 * m = constant and a maximal period of m-1. * * The transaction id is determined by: * id[n] = seed xor (g^X[n] mod n) * * Effectively the id is restricted to the lower (bits - 1) bits, thus * yielding two different cycles by toggling the msb on and off. * This avoids reuse issues caused by reseeding. */ #include <sys/cdefs.h> #if defined(LIBC_SCCS) && !defined(lint) __RCSID("$NetBSD: randomid.c,v 1.16 2022/05/15 20:37:50 andvar Exp $"); #endif #include "namespace.h" #include <sys/types.h> #include <sys/time.h> #include <stdlib.h> #include <string.h> #include <errno.h> #include <randomid.h> #ifdef __weak_alias __weak_alias(randomid,_randomid) __weak_alias(randomid_new,_randomid_new) __weak_alias(randomid_delete,_randomid_delete) #endif struct randomconf { const int rc_bits; /* resulting bits */ const u_int32_t rc_max; /* Uniq cycle, avoid blackjack prediction */ const u_int32_t rc_gen; /* Starting generator */ const u_int32_t rc_n; /* ru_n: prime, ru_n - 1: product of pfacts[] */ const u_int32_t rc_agen; /* determine ru_a as ru_agen^(2*rand) */ const u_int32_t rc_m; /* ru_m = 2^x*3^y */ const u_int32_t rc_pfacts[4]; /* factors of ru_n */ const int rc_skip; /* skip values */ }; struct randomid_ctx { struct randomconf *ru_conf; #define ru_bits ru_conf->rc_bits #define ru_max ru_conf->rc_max #define ru_gen ru_conf->rc_gen #define ru_n ru_conf->rc_n #define ru_agen ru_conf->rc_agen #define ru_m ru_conf->rc_m #define ru_pfacts ru_conf->rc_pfacts #define ru_skip ru_conf->rc_skip long ru_out; /* Time after which will be reseeded */ u_int32_t ru_counter; u_int32_t ru_msb; u_int32_t ru_x; u_int32_t ru_seed, ru_seed2; u_int32_t ru_a, ru_b; u_int32_t ru_g; time_t ru_reseed; }; static struct randomconf randomconf[] = { { 32, /* resulting bits */ 1000000000, /* Uniq cycle, avoid blackjack prediction */ 2, /* Starting generator */ 2147483629, /* RU_N-1 = 2^2*3^2*59652323 */ 7, /* determine ru_a as RU_AGEN^(2*rand) */ 1836660096, /* RU_M = 2^7*3^15 - don't change */ { 2, 3, 59652323, 0 }, /* factors of ru_n */ 3, /* skip values */ }, { 20, /* resulting bits */ 200000, /* Uniq cycle, avoid blackjack prediction */ 2, /* Starting generator */ 524269, /* RU_N-1 = 2^2*3^2*14563 */ 7, /* determine ru_a as RU_AGEN^(2*rand) */ 279936, /* RU_M = 2^7*3^7 - don't change */ { 2, 3, 14563, 0 }, /* factors of ru_n */ 3, /* skip values */ }, { 16, /* resulting bits */ 30000, /* Uniq cycle, avoid blackjack prediction */ 2, /* Starting generator */ 32749, /* RU_N-1 = 2^2*3*2729 */ 7, /* determine ru_a as RU_AGEN^(2*rand) */ 31104, /* RU_M = 2^7*3^5 - don't change */ { 2, 3, 2729, 0 }, /* factors of ru_n */ 0, /* skip values */ }, { .rc_bits = -1, /* termination */ }, }; static u_int32_t pmod(u_int32_t, u_int32_t, u_int32_t); static void initid(struct randomid_ctx *); struct randomid_ctx *randomid_new(int, long); void randomid_delete(struct randomid_ctx *); u_int32_t randomid(struct randomid_ctx *); /* * Do a fast modular exponation, returned value will be in the range * of 0 - (mod-1) */ static u_int32_t pmod(u_int32_t gen, u_int32_t expo, u_int32_t mod) { u_int64_t s, t, u; s = 1; t = gen; u = expo; while (u) { if (u & 1) s = (s * t) % mod; u >>= 1; t = (t * t) % mod; } return ((u_int32_t)s & UINT32_MAX); } /* * Initializes the seed and chooses a suitable generator. Also toggles * the msb flag. The msb flag is used to generate two distinct * cycles of random numbers and thus avoiding reuse of ids. * * This function is called from id_randomid() when needed, an * application does not have to worry about it. */ static void initid(struct randomid_ctx *p) { u_int32_t j, i; int noprime = 1; struct timeval tv; p->ru_x = arc4random() % p->ru_m; /* (bits - 1) bits of random seed */ p->ru_seed = arc4random() & (~0U >> (32 - p->ru_bits + 1)); p->ru_seed2 = arc4random() & (~0U >> (32 - p->ru_bits + 1)); /* Determine the LCG we use */ p->ru_b = (arc4random() & (~0U >> (32 - p->ru_bits))) | 1; p->ru_a = pmod(p->ru_agen, (arc4random() & (~0U >> (32 - p->ru_bits))) & (~1U), p->ru_m); while (p->ru_b % 3 == 0) p->ru_b += 2; j = arc4random() % p->ru_n; /* * Do a fast gcd(j, RU_N - 1), so we can find a j with * gcd(j, RU_N - 1) == 1, giving a new generator for * RU_GEN^j mod RU_N */ while (noprime) { for (i = 0; p->ru_pfacts[i] > 0; i++) if (j % p->ru_pfacts[i] == 0) break; if (p->ru_pfacts[i] == 0) noprime = 0; else j = (j + 1) % p->ru_n; } p->ru_g = pmod(p->ru_gen, j, p->ru_n); p->ru_counter = 0; gettimeofday(&tv, NULL); p->ru_reseed = tv.tv_sec + p->ru_out; p->ru_msb = p->ru_msb ? 0 : (1U << (p->ru_bits - 1)); } struct randomid_ctx * randomid_new(int bits, long timeo) { struct randomconf *conf; struct randomid_ctx *ctx; if (timeo < RANDOMID_TIMEO_MIN) { errno = EINVAL; return (NULL); } for (conf = randomconf; conf->rc_bits > 0; conf++) { if (bits == conf->rc_bits) break; } /* unsupported bits */ if (bits != conf->rc_bits) { errno = ENOTSUP; return (NULL); } ctx = malloc(sizeof(*ctx)); if (!ctx) return (NULL); memset(ctx, 0, sizeof(*ctx)); ctx->ru_conf = conf; ctx->ru_out = timeo; return (ctx); } void randomid_delete(struct randomid_ctx *ctx) { memset(ctx, 0, sizeof(*ctx)); free(ctx); } u_int32_t randomid(struct randomid_ctx *p) { int i, n; struct timeval tv; gettimeofday(&tv, NULL); if (p->ru_counter >= p->ru_max || tv.tv_sec > p->ru_reseed) initid(p); /* Skip a random number of ids */ if (p->ru_skip) { n = arc4random() & p->ru_skip; if (p->ru_counter + n >= p->ru_max) initid(p); } else n = 0; for (i = 0; i <= n; i++) { /* Linear Congruential Generator */ p->ru_x = (u_int32_t)(((u_int64_t)p->ru_a * p->ru_x + p->ru_b) % p->ru_m); } p->ru_counter += i; return (p->ru_seed ^ pmod(p->ru_g, p->ru_seed2 + p->ru_x, p->ru_n)) | p->ru_msb; }
