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 "namespace.h" 38 #include <sys/param.h> 39 #include <sys/sysctl.h> 40 #include <assert.h> 41 #include <pthread.h> 42 #include <stdbool.h> 43 #include <stdlib.h> 44 #include <syslog.h> 45 #include "un-namespace.h" 46 47 #include "libc_private.h" 48 #include "random.h" 49 50 /* 51 * Implement rand(3), the standard C PRNG API, using the non-standard but 52 * higher quality random(3) implementation and the same size 128-byte state 53 * LFSR as the random(3) default. 54 * 55 * It turns out there are portable applications that want a PRNG but are too 56 * lazy to use better-but-nonstandard interfaces like random(3), when 57 * available, and too lazy to import higher-quality and faster PRNGs into their 58 * codebase (such as any of SFC, JSF, 128-bit LCGs, PCG, or Splitmix64). 59 * 60 * Since we're stuck with rand(3) due to the C standard, we can at least have 61 * it produce a relatively good PRNG sequence using our existing random(3) 62 * LFSR. The random(3) design is not particularly fast nor compact, but it has 63 * the advantage of being the one already in the tree. 64 */ 65 static struct __random_state *rand3_state; 66 static pthread_once_t rand3_state_once = PTHREAD_ONCE_INIT; 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 _once(&rand3_state_once, initialize_rand3); 82 return ((int)random_r(rand3_state)); 83 } 84 85 void 86 srand(unsigned seed) 87 { 88 _once(&rand3_state_once, initialize_rand3); 89 srandom_r(rand3_state, seed); 90 } 91 92 /* 93 * FreeBSD 12 and prior compatibility implementation of rand(3). 94 */ 95 static int 96 do_rand(unsigned long *ctx) 97 { 98 /* 99 * Compute x = (7^5 * x) mod (2^31 - 1) 100 * without overflowing 31 bits: 101 * (2^31 - 1) = 127773 * (7^5) + 2836 102 * From "Random number generators: good ones are hard to find", 103 * Park and Miller, Communications of the ACM, vol. 31, no. 10, 104 * October 1988, p. 1195. 105 */ 106 long hi, lo, x; 107 108 /* Transform to [1, 0x7ffffffe] range. */ 109 x = (*ctx % 0x7ffffffe) + 1; 110 hi = x / 127773; 111 lo = x % 127773; 112 x = 16807 * lo - 2836 * hi; 113 if (x < 0) 114 x += 0x7fffffff; 115 /* Transform to [0, 0x7ffffffd] range. */ 116 x--; 117 *ctx = x; 118 return (x); 119 } 120 121 /* 122 * Can't fix this garbage; too little state. 123 */ 124 int 125 rand_r(unsigned *ctx) 126 { 127 u_long val; 128 int r; 129 130 val = *ctx; 131 r = do_rand(&val); 132 *ctx = (unsigned)val; 133 return (r); 134 } 135 136 static u_long next = 1; 137 138 int __rand_fbsd12(void); 139 int 140 __rand_fbsd12(void) 141 { 142 return (do_rand(&next)); 143 } 144 __sym_compat(rand, __rand_fbsd12, FBSD_1.0); 145 146 void __srand_fbsd12(unsigned seed); 147 void 148 __srand_fbsd12(unsigned seed) 149 { 150 next = seed; 151 } 152 __sym_compat(srand, __srand_fbsd12, FBSD_1.0); 153 154 void __sranddev_fbsd12(void); 155 void 156 __sranddev_fbsd12(void) 157 { 158 static bool warned = false; 159 160 if (!warned) { 161 syslog(LOG_DEBUG, "Deprecated function sranddev() called"); 162 warned = true; 163 } 164 } 165 __sym_compat(sranddev, __sranddev_fbsd12, FBSD_1.0); 166