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 #include "namespace.h" 35 #include <sys/param.h> 36 #include <sys/sysctl.h> 37 #include <assert.h> 38 #include <pthread.h> 39 #include <stdbool.h> 40 #include <stdlib.h> 41 #include <syslog.h> 42 #include "un-namespace.h" 43 44 #include "libc_private.h" 45 #include "random.h" 46 47 /* 48 * Implement rand(3), the standard C PRNG API, using the non-standard but 49 * higher quality random(3) implementation and the same size 128-byte state 50 * LFSR as the random(3) default. 51 * 52 * It turns out there are portable applications that want a PRNG but are too 53 * lazy to use better-but-nonstandard interfaces like random(3), when 54 * available, and too lazy to import higher-quality and faster PRNGs into their 55 * codebase (such as any of SFC, JSF, 128-bit LCGs, PCG, or Splitmix64). 56 * 57 * Since we're stuck with rand(3) due to the C standard, we can at least have 58 * it produce a relatively good PRNG sequence using our existing random(3) 59 * LFSR. The random(3) design is not particularly fast nor compact, but it has 60 * the advantage of being the one already in the tree. 61 */ 62 static struct __random_state *rand3_state; 63 static pthread_once_t rand3_state_once = PTHREAD_ONCE_INIT; 64 65 static void 66 initialize_rand3(void) 67 { 68 int error; 69 70 rand3_state = allocatestate(TYPE_3); 71 error = initstate_r(rand3_state, 1, rand3_state->rst_randtbl, BREAK_3); 72 assert(error == 0); 73 } 74 75 int 76 rand(void) 77 { 78 _once(&rand3_state_once, initialize_rand3); 79 return ((int)random_r(rand3_state)); 80 } 81 82 void 83 srand(unsigned seed) 84 { 85 _once(&rand3_state_once, initialize_rand3); 86 srandom_r(rand3_state, seed); 87 } 88 89 /* 90 * FreeBSD 12 and prior compatibility implementation of rand(3). 91 */ 92 static int 93 do_rand(unsigned long *ctx) 94 { 95 /* 96 * Compute x = (7^5 * x) mod (2^31 - 1) 97 * without overflowing 31 bits: 98 * (2^31 - 1) = 127773 * (7^5) + 2836 99 * From "Random number generators: good ones are hard to find", 100 * Park and Miller, Communications of the ACM, vol. 31, no. 10, 101 * October 1988, p. 1195. 102 */ 103 long hi, lo, x; 104 105 /* Transform to [1, 0x7ffffffe] range. */ 106 x = (*ctx % 0x7ffffffe) + 1; 107 hi = x / 127773; 108 lo = x % 127773; 109 x = 16807 * lo - 2836 * hi; 110 if (x < 0) 111 x += 0x7fffffff; 112 /* Transform to [0, 0x7ffffffd] range. */ 113 x--; 114 *ctx = x; 115 return (x); 116 } 117 118 /* 119 * Can't fix this garbage; too little state. 120 */ 121 int 122 rand_r(unsigned *ctx) 123 { 124 u_long val; 125 int r; 126 127 val = *ctx; 128 r = do_rand(&val); 129 *ctx = (unsigned)val; 130 return (r); 131 } 132 133 static u_long next = 1; 134 135 int __rand_fbsd12(void); 136 int 137 __rand_fbsd12(void) 138 { 139 return (do_rand(&next)); 140 } 141 __sym_compat(rand, __rand_fbsd12, FBSD_1.0); 142 143 void __srand_fbsd12(unsigned seed); 144 void 145 __srand_fbsd12(unsigned seed) 146 { 147 next = seed; 148 } 149 __sym_compat(srand, __srand_fbsd12, FBSD_1.0); 150 151 void __sranddev_fbsd12(void); 152 void 153 __sranddev_fbsd12(void) 154 { 155 static bool warned = false; 156 157 if (!warned) { 158 syslog(LOG_DEBUG, "Deprecated function sranddev() called"); 159 warned = true; 160 } 161 } 162 __sym_compat(sranddev, __sranddev_fbsd12, FBSD_1.0); 163