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 #ifdef HAVE_STDINT_H 30 #include <stdint.h> 31 #endif 32 #include <stdlib.h> 33 #include <string.h> 34 #include <unistd.h> 35 #include <sys/types.h> 36 #include <sys/param.h> 37 #include <sys/time.h> 38 #ifndef UB_ON_WINDOWS 39 #include <sys/mman.h> 40 #endif 41 42 #define KEYSTREAM_ONLY 43 #include "chacha_private.h" 44 45 #define arc4_min(a, b) ((a) < (b) ? (a) : (b)) 46 #ifdef __GNUC__ 47 #define inline __inline 48 #else /* !__GNUC__ */ 49 #define inline 50 #endif /* !__GNUC__ */ 51 52 #define KEYSZ 32 53 #define IVSZ 8 54 #define BLOCKSZ 64 55 #define RSBUFSZ (16*BLOCKSZ) 56 57 /* Marked MAP_INHERIT_ZERO, so zero'd out in fork children. */ 58 static struct { 59 size_t rs_have; /* valid bytes at end of rs_buf */ 60 size_t rs_count; /* bytes till reseed */ 61 } *rs; 62 63 /* Preserved in fork children. */ 64 static struct { 65 chacha_ctx rs_chacha; /* chacha context for random keystream */ 66 u_char rs_buf[RSBUFSZ]; /* keystream blocks */ 67 } *rsx; 68 69 static inline void _rs_rekey(u_char *dat, size_t datlen); 70 71 static inline void 72 _rs_init(u_char *buf, size_t n) 73 { 74 if (n < KEYSZ + IVSZ) 75 return; 76 77 if (rs == NULL) { 78 #ifndef UB_ON_WINDOWS 79 if ((rs = mmap(NULL, sizeof(*rs), PROT_READ|PROT_WRITE, 80 MAP_ANON|MAP_PRIVATE, -1, 0)) == MAP_FAILED) 81 abort(); 82 #ifdef MAP_INHERIT_ZERO 83 if (minherit(rs, sizeof(*rs), MAP_INHERIT_ZERO) == -1) 84 abort(); 85 #endif 86 #else /* WINDOWS */ 87 rs = malloc(sizeof(*rs)); 88 if(!rs) 89 abort(); 90 #endif 91 } 92 if (rsx == NULL) { 93 #ifndef UB_ON_WINDOWS 94 if ((rsx = mmap(NULL, sizeof(*rsx), PROT_READ|PROT_WRITE, 95 MAP_ANON|MAP_PRIVATE, -1, 0)) == MAP_FAILED) 96 abort(); 97 #else /* WINDOWS */ 98 rsx = malloc(sizeof(*rsx)); 99 if(!rsx) 100 abort(); 101 #endif 102 } 103 104 chacha_keysetup(&rsx->rs_chacha, buf, KEYSZ * 8, 0); 105 chacha_ivsetup(&rsx->rs_chacha, buf + KEYSZ); 106 } 107 108 static void 109 _rs_stir(void) 110 { 111 u_char rnd[KEYSZ + IVSZ]; 112 113 if (getentropy(rnd, sizeof rnd) == -1) { 114 #ifdef SIGKILL 115 raise(SIGKILL); 116 #else 117 exit(9); /* windows */ 118 #endif 119 } 120 121 if (!rs) 122 _rs_init(rnd, sizeof(rnd)); 123 else 124 _rs_rekey(rnd, sizeof(rnd)); 125 explicit_bzero(rnd, sizeof(rnd)); /* discard source seed */ 126 127 /* invalidate rs_buf */ 128 rs->rs_have = 0; 129 memset(rsx->rs_buf, 0, sizeof(rsx->rs_buf)); 130 131 rs->rs_count = 1600000; 132 } 133 134 static inline void 135 _rs_stir_if_needed(size_t len) 136 { 137 #ifndef MAP_INHERIT_ZERO 138 static pid_t _rs_pid = 0; 139 pid_t pid = getpid(); 140 141 /* If a system lacks MAP_INHERIT_ZERO, resort to getpid() */ 142 if (_rs_pid == 0 || _rs_pid != pid) { 143 _rs_pid = pid; 144 if (rs) 145 rs->rs_count = 0; 146 } 147 #endif 148 if (!rs || rs->rs_count <= len) 149 _rs_stir(); 150 if (rs->rs_count <= len) 151 rs->rs_count = 0; 152 else 153 rs->rs_count -= len; 154 } 155 156 static inline void 157 _rs_rekey(u_char *dat, size_t datlen) 158 { 159 #ifndef KEYSTREAM_ONLY 160 memset(rsx->rs_buf, 0, sizeof(rsx->rs_buf)); 161 #endif 162 /* fill rs_buf with the keystream */ 163 chacha_encrypt_bytes(&rsx->rs_chacha, rsx->rs_buf, 164 rsx->rs_buf, sizeof(rsx->rs_buf)); 165 /* mix in optional user provided data */ 166 if (dat) { 167 size_t i, m; 168 169 m = arc4_min(datlen, KEYSZ + IVSZ); 170 for (i = 0; i < m; i++) 171 rsx->rs_buf[i] ^= dat[i]; 172 } 173 /* immediately reinit for backtracking resistance */ 174 _rs_init(rsx->rs_buf, KEYSZ + IVSZ); 175 memset(rsx->rs_buf, 0, KEYSZ + IVSZ); 176 rs->rs_have = sizeof(rsx->rs_buf) - KEYSZ - IVSZ; 177 } 178 179 static inline void 180 _rs_random_buf(void *_buf, size_t n) 181 { 182 u_char *buf = (u_char *)_buf; 183 u_char *keystream; 184 size_t m; 185 186 _rs_stir_if_needed(n); 187 while (n > 0) { 188 if (rs->rs_have > 0) { 189 m = arc4_min(n, rs->rs_have); 190 keystream = rsx->rs_buf + sizeof(rsx->rs_buf) 191 - rs->rs_have; 192 memcpy(buf, keystream, m); 193 memset(keystream, 0, m); 194 buf += m; 195 n -= m; 196 rs->rs_have -= m; 197 } 198 if (rs->rs_have == 0) 199 _rs_rekey(NULL, 0); 200 } 201 } 202 203 static inline void 204 _rs_random_u32(uint32_t *val) 205 { 206 u_char *keystream; 207 _rs_stir_if_needed(sizeof(*val)); 208 if (rs->rs_have < sizeof(*val)) 209 _rs_rekey(NULL, 0); 210 keystream = rsx->rs_buf + sizeof(rsx->rs_buf) - rs->rs_have; 211 memcpy(val, keystream, sizeof(*val)); 212 memset(keystream, 0, sizeof(*val)); 213 rs->rs_have -= sizeof(*val); 214 } 215 216 uint32_t 217 arc4random(void) 218 { 219 uint32_t val; 220 221 _ARC4_LOCK(); 222 _rs_random_u32(&val); 223 _ARC4_UNLOCK(); 224 return val; 225 } 226 227 void 228 arc4random_buf(void *buf, size_t n) 229 { 230 _ARC4_LOCK(); 231 _rs_random_buf(buf, n); 232 _ARC4_UNLOCK(); 233 } 234