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 <stdbool.h> 45 #include <stdlib.h> 46 #include <syslog.h> 47 #include "un-namespace.h" 48 49 #include "random.h" 50 51 /* 52 * Implement rand(3), the standard C PRNG API, using the non-standard but 53 * higher quality random(3) implementation and the same size 128-byte state 54 * LFSR as the random(3) default. 55 * 56 * It turns out there are portable applications that want a PRNG but are too 57 * lazy to use better-but-nonstandard interfaces like random(3), when 58 * available, and too lazy to import higher-quality and faster PRNGs into their 59 * codebase (such as any of SFC, JSF, 128-bit LCGs, PCG, or Splitmix64). 60 * 61 * Since we're stuck with rand(3) due to the C standard, we can at least have 62 * it produce a relatively good PRNG sequence using our existing random(3) 63 * LFSR. The random(3) design is not particularly fast nor compact, but it has 64 * the advantage of being the one already in the tree. 65 */ 66 static struct __random_state *rand3_state; 67 68 static void 69 initialize_rand3(void) 70 { 71 int error; 72 73 rand3_state = allocatestate(TYPE_3); 74 error = initstate_r(rand3_state, 1, rand3_state->rst_randtbl, BREAK_3); 75 assert(error == 0); 76 } 77 78 int 79 rand(void) 80 { 81 if (rand3_state == NULL) 82 initialize_rand3(); 83 return ((int)random_r(rand3_state)); 84 } 85 86 void 87 srand(unsigned seed) 88 { 89 if (rand3_state == NULL) 90 initialize_rand3(); 91 srandom_r(rand3_state, seed); 92 } 93 94 /* 95 * FreeBSD 12 and prior compatibility implementation of rand(3). 96 */ 97 static int 98 do_rand(unsigned long *ctx) 99 { 100 /* 101 * Compute x = (7^5 * x) mod (2^31 - 1) 102 * without overflowing 31 bits: 103 * (2^31 - 1) = 127773 * (7^5) + 2836 104 * From "Random number generators: good ones are hard to find", 105 * Park and Miller, Communications of the ACM, vol. 31, no. 10, 106 * October 1988, p. 1195. 107 */ 108 long hi, lo, x; 109 110 /* Transform to [1, 0x7ffffffe] range. */ 111 x = (*ctx % 0x7ffffffe) + 1; 112 hi = x / 127773; 113 lo = x % 127773; 114 x = 16807 * lo - 2836 * hi; 115 if (x < 0) 116 x += 0x7fffffff; 117 /* Transform to [0, 0x7ffffffd] range. */ 118 x--; 119 *ctx = x; 120 return (x); 121 } 122 123 /* 124 * Can't fix this garbage; too little state. 125 */ 126 int 127 rand_r(unsigned *ctx) 128 { 129 u_long val; 130 int r; 131 132 val = *ctx; 133 r = do_rand(&val); 134 *ctx = (unsigned)val; 135 return (r); 136 } 137 138 static u_long next = 1; 139 140 int __rand_fbsd12(void); 141 int 142 __rand_fbsd12(void) 143 { 144 return (do_rand(&next)); 145 } 146 __sym_compat(rand, __rand_fbsd12, FBSD_1.0); 147 148 void __srand_fbsd12(unsigned seed); 149 void 150 __srand_fbsd12(unsigned seed) 151 { 152 next = seed; 153 } 154 __sym_compat(srand, __srand_fbsd12, FBSD_1.0); 155 156 void __sranddev_fbsd12(void); 157 void 158 __sranddev_fbsd12(void) 159 { 160 static bool warned = false; 161 162 if (!warned) { 163 syslog(LOG_DEBUG, "Deprecated function sranddev() called"); 164 warned = true; 165 } 166 } 167 __sym_compat(sranddev, __sranddev_fbsd12, FBSD_1.0); 168