1 /* $OpenBSD: arc4random.c,v 1.54 2015/09/13 08:31:47 guenther 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 * Copyright (c) 2014, Theo de Raadt <deraadt@openbsd.org> 8 * 9 * Permission to use, copy, modify, and distribute this software for any 10 * purpose with or without fee is hereby granted, provided that the above 11 * copyright notice and this permission notice appear in all copies. 12 * 13 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES 14 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF 15 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR 16 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES 17 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN 18 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF 19 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. 20 */ 21 22 /* 23 * ChaCha based random number generator for OpenBSD. 24 */ 25 26 #include <sys/cdefs.h> 27 __FBSDID("$FreeBSD$"); 28 29 #include "namespace.h" 30 #include <fcntl.h> 31 #include <limits.h> 32 #include <pthread.h> 33 #include <signal.h> 34 #include <stdint.h> 35 #include <stdlib.h> 36 #include <string.h> 37 #include <unistd.h> 38 #include <sys/types.h> 39 #include <sys/time.h> 40 41 #include "libc_private.h" 42 #include "un-namespace.h" 43 44 #define CHACHA_EMBED 45 #define KEYSTREAM_ONLY 46 #include "chacha.c" 47 48 #define minimum(a, b) ((a) < (b) ? (a) : (b)) 49 50 #if defined(__GNUC__) || defined(_MSC_VER) 51 #define inline __inline 52 #else /* __GNUC__ || _MSC_VER */ 53 #define inline 54 #endif /* !__GNUC__ && !_MSC_VER */ 55 56 #define KEYSZ 32 57 #define IVSZ 8 58 #define BLOCKSZ 64 59 #define RSBUFSZ (16*BLOCKSZ) 60 61 /* Marked INHERIT_ZERO, so zero'd out in fork children. */ 62 static struct _rs { 63 size_t rs_have; /* valid bytes at end of rs_buf */ 64 size_t rs_count; /* bytes till reseed */ 65 } *rs; 66 67 /* Maybe be preserved in fork children, if _rs_allocate() decides. */ 68 static struct _rsx { 69 chacha_ctx rs_chacha; /* chacha context for random keystream */ 70 u_char rs_buf[RSBUFSZ]; /* keystream blocks */ 71 } *rsx; 72 73 static inline int _rs_allocate(struct _rs **, struct _rsx **); 74 static inline void _rs_forkdetect(void); 75 #include "arc4random.h" 76 77 static inline void _rs_rekey(u_char *dat, size_t datlen); 78 79 static inline void 80 _rs_init(u_char *buf, size_t n) 81 { 82 if (n < KEYSZ + IVSZ) 83 return; 84 85 if (rs == NULL) { 86 if (_rs_allocate(&rs, &rsx) == -1) 87 abort(); 88 } 89 90 chacha_keysetup(&rsx->rs_chacha, buf, KEYSZ * 8); 91 chacha_ivsetup(&rsx->rs_chacha, buf + KEYSZ, NULL); 92 } 93 94 static void 95 _rs_stir(void) 96 { 97 u_char rnd[KEYSZ + IVSZ]; 98 99 if (getentropy(rnd, sizeof rnd) == -1) 100 _getentropy_fail(); 101 102 if (!rs) 103 _rs_init(rnd, sizeof(rnd)); 104 else 105 _rs_rekey(rnd, sizeof(rnd)); 106 explicit_bzero(rnd, sizeof(rnd)); /* discard source seed */ 107 108 /* invalidate rs_buf */ 109 rs->rs_have = 0; 110 memset(rsx->rs_buf, 0, sizeof(rsx->rs_buf)); 111 112 rs->rs_count = 1600000; 113 } 114 115 static inline void 116 _rs_stir_if_needed(size_t len) 117 { 118 _rs_forkdetect(); 119 if (!rs || rs->rs_count <= len) 120 _rs_stir(); 121 if (rs->rs_count <= len) 122 rs->rs_count = 0; 123 else 124 rs->rs_count -= len; 125 } 126 127 static inline void 128 _rs_rekey(u_char *dat, size_t datlen) 129 { 130 #ifndef KEYSTREAM_ONLY 131 memset(rsx->rs_buf, 0, sizeof(rsx->rs_buf)); 132 #endif 133 /* fill rs_buf with the keystream */ 134 chacha_encrypt_bytes(&rsx->rs_chacha, rsx->rs_buf, 135 rsx->rs_buf, sizeof(rsx->rs_buf)); 136 /* mix in optional user provided data */ 137 if (dat) { 138 size_t i, m; 139 140 m = minimum(datlen, KEYSZ + IVSZ); 141 for (i = 0; i < m; i++) 142 rsx->rs_buf[i] ^= dat[i]; 143 } 144 /* immediately reinit for backtracking resistance */ 145 _rs_init(rsx->rs_buf, KEYSZ + IVSZ); 146 memset(rsx->rs_buf, 0, KEYSZ + IVSZ); 147 rs->rs_have = sizeof(rsx->rs_buf) - KEYSZ - IVSZ; 148 } 149 150 static inline void 151 _rs_random_buf(void *_buf, size_t n) 152 { 153 u_char *buf = (u_char *)_buf; 154 u_char *keystream; 155 size_t m; 156 157 _rs_stir_if_needed(n); 158 while (n > 0) { 159 if (rs->rs_have > 0) { 160 m = minimum(n, rs->rs_have); 161 keystream = rsx->rs_buf + sizeof(rsx->rs_buf) 162 - rs->rs_have; 163 memcpy(buf, keystream, m); 164 memset(keystream, 0, m); 165 buf += m; 166 n -= m; 167 rs->rs_have -= m; 168 } 169 if (rs->rs_have == 0) 170 _rs_rekey(NULL, 0); 171 } 172 } 173 174 static inline void 175 _rs_random_u32(uint32_t *val) 176 { 177 u_char *keystream; 178 179 _rs_stir_if_needed(sizeof(*val)); 180 if (rs->rs_have < sizeof(*val)) 181 _rs_rekey(NULL, 0); 182 keystream = rsx->rs_buf + sizeof(rsx->rs_buf) - rs->rs_have; 183 memcpy(val, keystream, sizeof(*val)); 184 memset(keystream, 0, sizeof(*val)); 185 rs->rs_have -= sizeof(*val); 186 } 187 188 uint32_t 189 arc4random(void) 190 { 191 uint32_t val; 192 193 _ARC4_LOCK(); 194 _rs_random_u32(&val); 195 _ARC4_UNLOCK(); 196 return val; 197 } 198 199 void 200 arc4random_buf(void *buf, size_t n) 201 { 202 _ARC4_LOCK(); 203 _rs_random_buf(buf, n); 204 _ARC4_UNLOCK(); 205 } 206