1 /*- 2 * SPDX-License-Identifier: BSD-3-Clause 3 * 4 * Copyright (c) 1990, 1993 5 * The Regents of the University of California. All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer. 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 3. Neither the name of the University nor the names of its contributors 16 * may be used to endorse or promote products derived from this software 17 * without specific prior written permission. 18 * 19 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 20 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 22 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 23 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 24 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 25 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 26 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 29 * SUCH DAMAGE. 30 * 31 * Posix rand_r function added May 1999 by Wes Peters <wes@softweyr.com>. 32 */ 33 34 #if defined(LIBC_SCCS) && !defined(lint) 35 static char sccsid[] = "@(#)rand.c 8.1 (Berkeley) 6/14/93"; 36 #endif /* LIBC_SCCS and not lint */ 37 #include <sys/cdefs.h> 38 __FBSDID("$FreeBSD$"); 39 40 #include "namespace.h" 41 #include <sys/param.h> 42 #include <sys/sysctl.h> 43 #include <assert.h> 44 #include <pthread.h> 45 #include <stdbool.h> 46 #include <stdlib.h> 47 #include <syslog.h> 48 #include "un-namespace.h" 49 50 #include "libc_private.h" 51 #include "random.h" 52 53 /* 54 * Implement rand(3), the standard C PRNG API, using the non-standard but 55 * higher quality random(3) implementation and the same size 128-byte state 56 * LFSR as the random(3) default. 57 * 58 * It turns out there are portable applications that want a PRNG but are too 59 * lazy to use better-but-nonstandard interfaces like random(3), when 60 * available, and too lazy to import higher-quality and faster PRNGs into their 61 * codebase (such as any of SFC, JSF, 128-bit LCGs, PCG, or Splitmix64). 62 * 63 * Since we're stuck with rand(3) due to the C standard, we can at least have 64 * it produce a relatively good PRNG sequence using our existing random(3) 65 * LFSR. The random(3) design is not particularly fast nor compact, but it has 66 * the advantage of being the one already in the tree. 67 */ 68 static struct __random_state *rand3_state; 69 static pthread_once_t rand3_state_once = PTHREAD_ONCE_INIT; 70 71 static void 72 initialize_rand3(void) 73 { 74 int error; 75 76 rand3_state = allocatestate(TYPE_3); 77 error = initstate_r(rand3_state, 1, rand3_state->rst_randtbl, BREAK_3); 78 assert(error == 0); 79 } 80 81 int 82 rand(void) 83 { 84 _once(&rand3_state_once, initialize_rand3); 85 return ((int)random_r(rand3_state)); 86 } 87 88 void 89 srand(unsigned seed) 90 { 91 _once(&rand3_state_once, initialize_rand3); 92 srandom_r(rand3_state, seed); 93 } 94 95 /* 96 * FreeBSD 12 and prior compatibility implementation of rand(3). 97 */ 98 static int 99 do_rand(unsigned long *ctx) 100 { 101 /* 102 * Compute x = (7^5 * x) mod (2^31 - 1) 103 * without overflowing 31 bits: 104 * (2^31 - 1) = 127773 * (7^5) + 2836 105 * From "Random number generators: good ones are hard to find", 106 * Park and Miller, Communications of the ACM, vol. 31, no. 10, 107 * October 1988, p. 1195. 108 */ 109 long hi, lo, x; 110 111 /* Transform to [1, 0x7ffffffe] range. */ 112 x = (*ctx % 0x7ffffffe) + 1; 113 hi = x / 127773; 114 lo = x % 127773; 115 x = 16807 * lo - 2836 * hi; 116 if (x < 0) 117 x += 0x7fffffff; 118 /* Transform to [0, 0x7ffffffd] range. */ 119 x--; 120 *ctx = x; 121 return (x); 122 } 123 124 /* 125 * Can't fix this garbage; too little state. 126 */ 127 int 128 rand_r(unsigned *ctx) 129 { 130 u_long val; 131 int r; 132 133 val = *ctx; 134 r = do_rand(&val); 135 *ctx = (unsigned)val; 136 return (r); 137 } 138 139 static u_long next = 1; 140 141 int __rand_fbsd12(void); 142 int 143 __rand_fbsd12(void) 144 { 145 return (do_rand(&next)); 146 } 147 __sym_compat(rand, __rand_fbsd12, FBSD_1.0); 148 149 void __srand_fbsd12(unsigned seed); 150 void 151 __srand_fbsd12(unsigned seed) 152 { 153 next = seed; 154 } 155 __sym_compat(srand, __srand_fbsd12, FBSD_1.0); 156 157 void __sranddev_fbsd12(void); 158 void 159 __sranddev_fbsd12(void) 160 { 161 static bool warned = false; 162 163 if (!warned) { 164 syslog(LOG_DEBUG, "Deprecated function sranddev() called"); 165 warned = true; 166 } 167 } 168 __sym_compat(sranddev, __sranddev_fbsd12, FBSD_1.0); 169