arc4random.c revision 1.5.2.2
1 1.5.2.2 jmc /* $NetBSD: arc4random.c,v 1.5.2.2 2004/03/26 22:52:50 jmc Exp $ */ 2 1.5.2.2 jmc /* $OpenBSD: arc4random.c,v 1.6 2001/06/05 05:05:38 pvalchev Exp $ */ 3 1.5.2.2 jmc 4 1.5.2.2 jmc /* 5 1.5.2.2 jmc * Arc4 random number generator for OpenBSD. 6 1.5.2.2 jmc * Copyright 1996 David Mazieres <dm (at) lcs.mit.edu>. 7 1.5.2.2 jmc * 8 1.5.2.2 jmc * Modification and redistribution in source and binary forms is 9 1.5.2.2 jmc * permitted provided that due credit is given to the author and the 10 1.5.2.2 jmc * OpenBSD project by leaving this copyright notice intact. 11 1.5.2.2 jmc */ 12 1.5.2.2 jmc 13 1.5.2.2 jmc /* 14 1.5.2.2 jmc * This code is derived from section 17.1 of Applied Cryptography, 15 1.5.2.2 jmc * second edition, which describes a stream cipher allegedly 16 1.5.2.2 jmc * compatible with RSA Labs "RC4" cipher (the actual description of 17 1.5.2.2 jmc * which is a trade secret). The same algorithm is used as a stream 18 1.5.2.2 jmc * cipher called "arcfour" in Tatu Ylonen's ssh package. 19 1.5.2.2 jmc * 20 1.5.2.2 jmc * Here the stream cipher has been modified always to include the time 21 1.5.2.2 jmc * when initializing the state. That makes it impossible to 22 1.5.2.2 jmc * regenerate the same random sequence twice, so this can't be used 23 1.5.2.2 jmc * for encryption, but will generate good random numbers. 24 1.5.2.2 jmc * 25 1.5.2.2 jmc * RC4 is a registered trademark of RSA Laboratories. 26 1.5.2.2 jmc */ 27 1.5.2.2 jmc 28 1.5.2.2 jmc #include <fcntl.h> 29 1.5.2.2 jmc #include <stdlib.h> 30 1.5.2.2 jmc #include <unistd.h> 31 1.5.2.2 jmc #include <sys/types.h> 32 1.5.2.2 jmc #include <sys/param.h> 33 1.5.2.2 jmc #include <sys/time.h> 34 1.5.2.2 jmc #include <sys/sysctl.h> 35 1.5.2.2 jmc 36 1.5.2.2 jmc #ifdef __GNUC__ 37 1.5.2.2 jmc #define inline __inline 38 1.5.2.2 jmc #else /* !__GNUC__ */ 39 1.5.2.2 jmc #define inline 40 1.5.2.2 jmc #endif /* !__GNUC__ */ 41 1.5.2.2 jmc 42 1.5.2.2 jmc struct arc4_stream { 43 1.5.2.2 jmc u_int8_t i; 44 1.5.2.2 jmc u_int8_t j; 45 1.5.2.2 jmc u_int8_t s[256]; 46 1.5.2.2 jmc }; 47 1.5.2.2 jmc 48 1.5.2.2 jmc int rs_initialized; 49 1.5.2.2 jmc static struct arc4_stream rs; 50 1.5.2.2 jmc 51 1.5.2.2 jmc static inline void arc4_init(struct arc4_stream *); 52 1.5.2.2 jmc static inline void arc4_addrandom(struct arc4_stream *, u_char *, int); 53 1.5.2.2 jmc static void arc4_stir(struct arc4_stream *); 54 1.5.2.2 jmc static inline u_int8_t arc4_getbyte(struct arc4_stream *); 55 1.5.2.2 jmc static inline u_int32_t arc4_getword(struct arc4_stream *); 56 1.5.2.2 jmc 57 1.5.2.2 jmc static inline void 58 1.5.2.2 jmc arc4_init(as) 59 1.5.2.2 jmc struct arc4_stream *as; 60 1.5.2.2 jmc { 61 1.5.2.2 jmc int n; 62 1.5.2.2 jmc 63 1.5.2.2 jmc for (n = 0; n < 256; n++) 64 1.5.2.2 jmc as->s[n] = n; 65 1.5.2.2 jmc as->i = 0; 66 1.5.2.2 jmc as->j = 0; 67 1.5.2.2 jmc } 68 1.5.2.2 jmc 69 1.5.2.2 jmc static inline void 70 1.5.2.2 jmc arc4_addrandom(as, dat, datlen) 71 1.5.2.2 jmc struct arc4_stream *as; 72 1.5.2.2 jmc u_char *dat; 73 1.5.2.2 jmc int datlen; 74 1.5.2.2 jmc { 75 1.5.2.2 jmc int n; 76 1.5.2.2 jmc u_int8_t si; 77 1.5.2.2 jmc 78 1.5.2.2 jmc as->i--; 79 1.5.2.2 jmc for (n = 0; n < 256; n++) { 80 1.5.2.2 jmc as->i = (as->i + 1); 81 1.5.2.2 jmc si = as->s[as->i]; 82 1.5.2.2 jmc as->j = (as->j + si + dat[n % datlen]); 83 1.5.2.2 jmc as->s[as->i] = as->s[as->j]; 84 1.5.2.2 jmc as->s[as->j] = si; 85 1.5.2.2 jmc } 86 1.5.2.2 jmc as->j = as->i; 87 1.5.2.2 jmc } 88 1.5.2.2 jmc 89 1.5.2.2 jmc static void 90 1.5.2.2 jmc arc4_stir(as) 91 1.5.2.2 jmc struct arc4_stream *as; 92 1.5.2.2 jmc { 93 1.5.2.2 jmc int fd; 94 1.5.2.2 jmc struct { 95 1.5.2.2 jmc struct timeval tv; 96 1.5.2.2 jmc u_int rnd[(128 - sizeof(struct timeval)) / sizeof(u_int)]; 97 1.5.2.2 jmc } rdat; 98 1.5.2.2 jmc int n; 99 1.5.2.2 jmc 100 1.5.2.2 jmc gettimeofday(&rdat.tv, NULL); 101 1.5.2.2 jmc fd = open("/dev/urandom", O_RDONLY); 102 1.5.2.2 jmc if (fd != -1) { 103 1.5.2.2 jmc read(fd, rdat.rnd, sizeof(rdat.rnd)); 104 1.5.2.2 jmc close(fd); 105 1.5.2.2 jmc } 106 1.5.2.2 jmc #ifdef KERN_URND 107 1.5.2.2 jmc else { 108 1.5.2.2 jmc int mib[2]; 109 1.5.2.2 jmc u_int i; 110 1.5.2.2 jmc size_t len; 111 1.5.2.2 jmc 112 1.5.2.2 jmc /* Device could not be opened, we might be chrooted, take 113 1.5.2.2 jmc * randomness from sysctl. */ 114 1.5.2.2 jmc 115 1.5.2.2 jmc mib[0] = CTL_KERN; 116 1.5.2.2 jmc mib[1] = KERN_URND; 117 1.5.2.2 jmc 118 1.5.2.2 jmc for (i = 0; i < sizeof(rdat.rnd) / sizeof(u_int); i++) { 119 1.5.2.2 jmc len = sizeof(u_int); 120 1.5.2.2 jmc if (sysctl(mib, 2, &rdat.rnd[i], &len, NULL, 0) == -1) 121 1.5.2.2 jmc break; 122 1.5.2.2 jmc } 123 1.5.2.2 jmc } 124 1.5.2.2 jmc #endif 125 1.5.2.2 jmc /* fd < 0 or failed sysctl ? Ah, what the heck. We'll just take 126 1.5.2.2 jmc * whatever was on the stack... */ 127 1.5.2.2 jmc 128 1.5.2.2 jmc arc4_addrandom(as, (void *) &rdat, sizeof(rdat)); 129 1.5.2.2 jmc 130 1.5.2.2 jmc /* 131 1.5.2.2 jmc * Throw away the first N words of output, as suggested in the 132 1.5.2.2 jmc * paper "Weaknesses in the Key Scheduling Algorithm of RC4" 133 1.5.2.2 jmc * by Fluher, Mantin, and Shamir. (N = 256 in our case.) 134 1.5.2.2 jmc */ 135 1.5.2.2 jmc for (n = 0; n < 256 * 4; n++) 136 1.5.2.2 jmc arc4_getbyte(as); 137 1.5.2.2 jmc } 138 1.5.2.2 jmc 139 1.5.2.2 jmc static inline u_int8_t 140 1.5.2.2 jmc arc4_getbyte(as) 141 1.5.2.2 jmc struct arc4_stream *as; 142 1.5.2.2 jmc { 143 1.5.2.2 jmc u_int8_t si, sj; 144 1.5.2.2 jmc 145 1.5.2.2 jmc as->i = (as->i + 1); 146 1.5.2.2 jmc si = as->s[as->i]; 147 1.5.2.2 jmc as->j = (as->j + si); 148 1.5.2.2 jmc sj = as->s[as->j]; 149 1.5.2.2 jmc as->s[as->i] = sj; 150 1.5.2.2 jmc as->s[as->j] = si; 151 1.5.2.2 jmc return (as->s[(si + sj) & 0xff]); 152 1.5.2.2 jmc } 153 1.5.2.2 jmc 154 1.5.2.2 jmc static inline u_int32_t 155 1.5.2.2 jmc arc4_getword(as) 156 1.5.2.2 jmc struct arc4_stream *as; 157 1.5.2.2 jmc { 158 1.5.2.2 jmc u_int32_t val; 159 1.5.2.2 jmc val = arc4_getbyte(as) << 24; 160 1.5.2.2 jmc val |= arc4_getbyte(as) << 16; 161 1.5.2.2 jmc val |= arc4_getbyte(as) << 8; 162 1.5.2.2 jmc val |= arc4_getbyte(as); 163 1.5.2.2 jmc return val; 164 1.5.2.2 jmc } 165 1.5.2.2 jmc 166 1.5.2.2 jmc void 167 1.5.2.2 jmc arc4random_stir() 168 1.5.2.2 jmc { 169 1.5.2.2 jmc if (!rs_initialized) { 170 1.5.2.2 jmc arc4_init(&rs); 171 1.5.2.2 jmc rs_initialized = 1; 172 1.5.2.2 jmc } 173 1.5.2.2 jmc arc4_stir(&rs); 174 1.5.2.2 jmc } 175 1.5.2.2 jmc 176 1.5.2.2 jmc void 177 1.5.2.2 jmc arc4random_addrandom(dat, datlen) 178 1.5.2.2 jmc u_char *dat; 179 1.5.2.2 jmc int datlen; 180 1.5.2.2 jmc { 181 1.5.2.2 jmc if (!rs_initialized) 182 1.5.2.2 jmc arc4random_stir(); 183 1.5.2.2 jmc arc4_addrandom(&rs, dat, datlen); 184 1.5.2.2 jmc } 185 1.5.2.2 jmc 186 1.5.2.2 jmc u_int32_t 187 1.5.2.2 jmc arc4random() 188 1.5.2.2 jmc { 189 1.5.2.2 jmc if (!rs_initialized) 190 1.5.2.2 jmc arc4random_stir(); 191 1.5.2.2 jmc return arc4_getword(&rs); 192 1.5.2.2 jmc } 193 1.5.2.2 jmc 194 1.5.2.2 jmc #if 0 195 1.5.2.2 jmc /*-------- Test code for i386 --------*/ 196 1.5.2.2 jmc #include <stdio.h> 197 1.5.2.2 jmc #include <machine/pctr.h> 198 1.5.2.2 jmc int 199 1.5.2.2 jmc main(int argc, char **argv) 200 1.5.2.2 jmc { 201 1.5.2.2 jmc const int iter = 1000000; 202 1.5.2.2 jmc int i; 203 1.5.2.2 jmc pctrval v; 204 1.5.2.2 jmc 205 1.5.2.2 jmc v = rdtsc(); 206 1.5.2.2 jmc for (i = 0; i < iter; i++) 207 1.5.2.2 jmc arc4random(); 208 1.5.2.2 jmc v = rdtsc() - v; 209 1.5.2.2 jmc v /= iter; 210 1.5.2.2 jmc 211 1.5.2.2 jmc printf("%qd cycles\n", v); 212 1.5.2.2 jmc } 213 1.5.2.2 jmc #endif 214
Indexes created Mon Sep 29 21:09:56 GMT 2025