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 KEYSTREAM_ONLY 45 #include "chacha.c" 46 47 #define minimum(a, b) ((a) < (b) ? (a) : (b)) 48 49 #if defined(__GNUC__) || defined(_MSC_VER) 50 #define inline __inline 51 #else /* __GNUC__ || _MSC_VER */ 52 #define inline 53 #endif /* !__GNUC__ && !_MSC_VER */ 54 55 #define KEYSZ 32 56 #define IVSZ 8 57 #define BLOCKSZ 64 58 #define RSBUFSZ (16*BLOCKSZ) 59 60 /* Marked INHERIT_ZERO, so zero'd out in fork children. */ 61 static struct _rs { 62 size_t rs_have; /* valid bytes at end of rs_buf */ 63 size_t rs_count; /* bytes till reseed */ 64 } *rs; 65 66 /* Maybe be preserved in fork children, if _rs_allocate() decides. */ 67 static struct _rsx { 68 chacha_ctx rs_chacha; /* chacha context for random keystream */ 69 u_char rs_buf[RSBUFSZ]; /* keystream blocks */ 70 } *rsx; 71 72 static inline int _rs_allocate(struct _rs **, struct _rsx **); 73 static inline void _rs_forkdetect(void); 74 #include "arc4random.h" 75 76 static inline void _rs_rekey(u_char *dat, size_t datlen); 77 78 static inline void 79 _rs_init(u_char *buf, size_t n) 80 { 81 if (n < KEYSZ + IVSZ) 82 return; 83 84 if (rs == NULL) { 85 if (_rs_allocate(&rs, &rsx) == -1) 86 abort(); 87 } 88 89 chacha_keysetup(&rsx->rs_chacha, buf, KEYSZ * 8); 90 chacha_ivsetup(&rsx->rs_chacha, buf + KEYSZ, NULL); 91 } 92 93 static void 94 _rs_stir(void) 95 { 96 u_char rnd[KEYSZ + IVSZ]; 97 98 if (getentropy(rnd, sizeof rnd) == -1) 99 _getentropy_fail(); 100 101 if (!rs) 102 _rs_init(rnd, sizeof(rnd)); 103 else 104 _rs_rekey(rnd, sizeof(rnd)); 105 explicit_bzero(rnd, sizeof(rnd)); /* discard source seed */ 106 107 /* invalidate rs_buf */ 108 rs->rs_have = 0; 109 memset(rsx->rs_buf, 0, sizeof(rsx->rs_buf)); 110 111 rs->rs_count = 1600000; 112 } 113 114 static inline void 115 _rs_stir_if_needed(size_t len) 116 { 117 _rs_forkdetect(); 118 if (!rs || rs->rs_count <= len) 119 _rs_stir(); 120 if (rs->rs_count <= len) 121 rs->rs_count = 0; 122 else 123 rs->rs_count -= len; 124 } 125 126 static inline void 127 _rs_rekey(u_char *dat, size_t datlen) 128 { 129 #ifndef KEYSTREAM_ONLY 130 memset(rsx->rs_buf, 0, sizeof(rsx->rs_buf)); 131 #endif 132 /* fill rs_buf with the keystream */ 133 chacha_encrypt_bytes(&rsx->rs_chacha, rsx->rs_buf, 134 rsx->rs_buf, sizeof(rsx->rs_buf)); 135 /* mix in optional user provided data */ 136 if (dat) { 137 size_t i, m; 138 139 m = minimum(datlen, KEYSZ + IVSZ); 140 for (i = 0; i < m; i++) 141 rsx->rs_buf[i] ^= dat[i]; 142 } 143 /* immediately reinit for backtracking resistance */ 144 _rs_init(rsx->rs_buf, KEYSZ + IVSZ); 145 memset(rsx->rs_buf, 0, KEYSZ + IVSZ); 146 rs->rs_have = sizeof(rsx->rs_buf) - KEYSZ - IVSZ; 147 } 148 149 static inline void 150 _rs_random_buf(void *_buf, size_t n) 151 { 152 u_char *buf = (u_char *)_buf; 153 u_char *keystream; 154 size_t m; 155 156 _rs_stir_if_needed(n); 157 while (n > 0) { 158 if (rs->rs_have > 0) { 159 m = minimum(n, rs->rs_have); 160 keystream = rsx->rs_buf + sizeof(rsx->rs_buf) 161 - rs->rs_have; 162 memcpy(buf, keystream, m); 163 memset(keystream, 0, m); 164 buf += m; 165 n -= m; 166 rs->rs_have -= m; 167 } 168 if (rs->rs_have == 0) 169 _rs_rekey(NULL, 0); 170 } 171 } 172 173 static inline void 174 _rs_random_u32(uint32_t *val) 175 { 176 u_char *keystream; 177 178 _rs_stir_if_needed(sizeof(*val)); 179 if (rs->rs_have < sizeof(*val)) 180 _rs_rekey(NULL, 0); 181 keystream = rsx->rs_buf + sizeof(rsx->rs_buf) - rs->rs_have; 182 memcpy(val, keystream, sizeof(*val)); 183 memset(keystream, 0, sizeof(*val)); 184 rs->rs_have -= sizeof(*val); 185 } 186 187 uint32_t 188 arc4random(void) 189 { 190 uint32_t val; 191 192 _ARC4_LOCK(); 193 _rs_random_u32(&val); 194 _ARC4_UNLOCK(); 195 return val; 196 } 197 198 void 199 arc4random_buf(void *buf, size_t n) 200 { 201 _ARC4_LOCK(); 202 _rs_random_buf(buf, n); 203 _ARC4_UNLOCK(); 204 } 205