1 /* $OpenBSD: arc4random.c,v 1.41 2014/07/12 13:24:54 deraadt Exp $ */ 2 3 /* 4 * Copyright (c) 1996, David Mazieres <dm@uun.org> 5 * Copyright (c) 2008, Damien Miller <djm@openbsd.org> 6 * Copyright (c) 2013, Markus Friedl <markus@openbsd.org> 7 * 8 * Permission to use, copy, modify, and distribute this software for any 9 * purpose with or without fee is hereby granted, provided that the above 10 * copyright notice and this permission notice appear in all copies. 11 * 12 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES 13 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF 14 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR 15 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES 16 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN 17 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF 18 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. 19 */ 20 #include "config.h" 21 22 /* 23 * ChaCha based random number generator for OpenBSD. 24 */ 25 26 #include <fcntl.h> 27 #include <limits.h> 28 #include <signal.h> 29 #include <stdint.h> 30 #include <stdlib.h> 31 #include <string.h> 32 #include <unistd.h> 33 #include <sys/types.h> 34 #include <sys/param.h> 35 #include <sys/time.h> 36 #ifndef UB_ON_WINDOWS 37 #include <sys/mman.h> 38 #endif 39 40 #define KEYSTREAM_ONLY 41 #include "chacha_private.h" 42 43 #define arc4_min(a, b) ((a) < (b) ? (a) : (b)) 44 #ifdef __GNUC__ 45 #define inline __inline 46 #else /* !__GNUC__ */ 47 #define inline 48 #endif /* !__GNUC__ */ 49 50 #define KEYSZ 32 51 #define IVSZ 8 52 #define BLOCKSZ 64 53 #define RSBUFSZ (16*BLOCKSZ) 54 55 /* Marked MAP_INHERIT_ZERO, so zero'd out in fork children. */ 56 static struct { 57 size_t rs_have; /* valid bytes at end of rs_buf */ 58 size_t rs_count; /* bytes till reseed */ 59 } *rs; 60 61 /* Preserved in fork children. */ 62 static struct { 63 chacha_ctx rs_chacha; /* chacha context for random keystream */ 64 u_char rs_buf[RSBUFSZ]; /* keystream blocks */ 65 } *rsx; 66 67 static inline void _rs_rekey(u_char *dat, size_t datlen); 68 69 static inline void 70 _rs_init(u_char *buf, size_t n) 71 { 72 if (n < KEYSZ + IVSZ) 73 return; 74 75 if (rs == NULL) { 76 #ifndef UB_ON_WINDOWS 77 if ((rs = mmap(NULL, sizeof(*rs), PROT_READ|PROT_WRITE, 78 MAP_ANON|MAP_PRIVATE, -1, 0)) == MAP_FAILED) 79 abort(); 80 #ifdef MAP_INHERIT_ZERO 81 if (minherit(rs, sizeof(*rs), MAP_INHERIT_ZERO) == -1) 82 abort(); 83 #endif 84 #else /* WINDOWS */ 85 rs = malloc(sizeof(*rs)); 86 if(!rs) 87 abort(); 88 #endif 89 } 90 if (rsx == NULL) { 91 #ifndef UB_ON_WINDOWS 92 if ((rsx = mmap(NULL, sizeof(*rsx), PROT_READ|PROT_WRITE, 93 MAP_ANON|MAP_PRIVATE, -1, 0)) == MAP_FAILED) 94 abort(); 95 #else /* WINDOWS */ 96 rsx = malloc(sizeof(*rsx)); 97 if(!rsx) 98 abort(); 99 #endif 100 } 101 102 chacha_keysetup(&rsx->rs_chacha, buf, KEYSZ * 8, 0); 103 chacha_ivsetup(&rsx->rs_chacha, buf + KEYSZ); 104 } 105 106 static void 107 _rs_stir(void) 108 { 109 u_char rnd[KEYSZ + IVSZ]; 110 111 if (getentropy(rnd, sizeof rnd) == -1) { 112 #ifdef SIGKILL 113 raise(SIGKILL); 114 #else 115 exit(9); /* windows */ 116 #endif 117 } 118 119 if (!rs) 120 _rs_init(rnd, sizeof(rnd)); 121 else 122 _rs_rekey(rnd, sizeof(rnd)); 123 explicit_bzero(rnd, sizeof(rnd)); /* discard source seed */ 124 125 /* invalidate rs_buf */ 126 rs->rs_have = 0; 127 memset(rsx->rs_buf, 0, sizeof(rsx->rs_buf)); 128 129 rs->rs_count = 1600000; 130 } 131 132 static inline void 133 _rs_stir_if_needed(size_t len) 134 { 135 #ifndef MAP_INHERIT_ZERO 136 static pid_t _rs_pid = 0; 137 pid_t pid = getpid(); 138 139 /* If a system lacks MAP_INHERIT_ZERO, resort to getpid() */ 140 if (_rs_pid == 0 || _rs_pid != pid) { 141 _rs_pid = pid; 142 if (rs) 143 rs->rs_count = 0; 144 } 145 #endif 146 if (!rs || rs->rs_count <= len) 147 _rs_stir(); 148 if (rs->rs_count <= len) 149 rs->rs_count = 0; 150 else 151 rs->rs_count -= len; 152 } 153 154 static inline void 155 _rs_rekey(u_char *dat, size_t datlen) 156 { 157 #ifndef KEYSTREAM_ONLY 158 memset(rsx->rs_buf, 0, sizeof(rsx->rs_buf)); 159 #endif 160 /* fill rs_buf with the keystream */ 161 chacha_encrypt_bytes(&rsx->rs_chacha, rsx->rs_buf, 162 rsx->rs_buf, sizeof(rsx->rs_buf)); 163 /* mix in optional user provided data */ 164 if (dat) { 165 size_t i, m; 166 167 m = arc4_min(datlen, KEYSZ + IVSZ); 168 for (i = 0; i < m; i++) 169 rsx->rs_buf[i] ^= dat[i]; 170 } 171 /* immediately reinit for backtracking resistance */ 172 _rs_init(rsx->rs_buf, KEYSZ + IVSZ); 173 memset(rsx->rs_buf, 0, KEYSZ + IVSZ); 174 rs->rs_have = sizeof(rsx->rs_buf) - KEYSZ - IVSZ; 175 } 176 177 static inline void 178 _rs_random_buf(void *_buf, size_t n) 179 { 180 u_char *buf = (u_char *)_buf; 181 u_char *keystream; 182 size_t m; 183 184 _rs_stir_if_needed(n); 185 while (n > 0) { 186 if (rs->rs_have > 0) { 187 m = arc4_min(n, rs->rs_have); 188 keystream = rsx->rs_buf + sizeof(rsx->rs_buf) 189 - rs->rs_have; 190 memcpy(buf, keystream, m); 191 memset(keystream, 0, m); 192 buf += m; 193 n -= m; 194 rs->rs_have -= m; 195 } 196 if (rs->rs_have == 0) 197 _rs_rekey(NULL, 0); 198 } 199 } 200 201 static inline void 202 _rs_random_u32(uint32_t *val) 203 { 204 u_char *keystream; 205 _rs_stir_if_needed(sizeof(*val)); 206 if (rs->rs_have < sizeof(*val)) 207 _rs_rekey(NULL, 0); 208 keystream = rsx->rs_buf + sizeof(rsx->rs_buf) - rs->rs_have; 209 memcpy(val, keystream, sizeof(*val)); 210 memset(keystream, 0, sizeof(*val)); 211 rs->rs_have -= sizeof(*val); 212 } 213 214 uint32_t 215 arc4random(void) 216 { 217 uint32_t val; 218 219 _ARC4_LOCK(); 220 _rs_random_u32(&val); 221 _ARC4_UNLOCK(); 222 return val; 223 } 224 225 void 226 arc4random_buf(void *buf, size_t n) 227 { 228 _ARC4_LOCK(); 229 _rs_random_buf(buf, n); 230 _ARC4_UNLOCK(); 231 } 232