1 /* $OpenBSD: arc4random.c,v 1.41 2014/07/12 13:24:54 deraadt Exp $ */
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>
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.
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.
23 * ChaCha based random number generator for OpenBSD.
35 #include <sys/types.h>
36 #include <sys/param.h>
42 #define KEYSTREAM_ONLY
43 #include "chacha_private.h"
45 #define arc4_min(a, b) ((a) < (b) ? (a) : (b))
47 #define inline __inline
50 #endif /* !__GNUC__ */
52 #define MAP_ANON MAP_ANONYMOUS
58 #define RSBUFSZ (16*BLOCKSZ)
60 /* Marked MAP_INHERIT_ZERO, so zero'd out in fork children. */
62 size_t rs_have; /* valid bytes at end of rs_buf */
63 size_t rs_count; /* bytes till reseed */
66 /* Preserved in fork children. */
68 chacha_ctx rs_chacha; /* chacha context for random keystream */
69 u_char rs_buf[RSBUFSZ]; /* keystream blocks */
72 static inline void _rs_rekey(u_char *dat, size_t datlen);
75 * Basic sanity checking; wish we could do better.
78 fallback_gotdata(char *buf, size_t len)
83 for (i = 0; i < len; ++i)
90 /* fallback for getentropy in case libc returns failure */
92 fallback_getentropy_urandom(void *buf, size_t len)
96 int save_errno = errno;
107 fd = open("/dev/urandom", flags, 0);
115 fcntl(fd, F_SETFD, fcntl(fd, F_GETFD) | FD_CLOEXEC);
118 for (i = 0; i < len; ) {
119 size_t wanted = len - i;
120 ssize_t ret = read(fd, (char*)buf + i, wanted);
123 if (errno == EAGAIN || errno == EINTR)
131 if (fallback_gotdata(buf, len) == 0) {
133 return 0; /* satisfied */
141 _rs_init(u_char *buf, size_t n)
143 if (n < KEYSZ + IVSZ)
147 #ifndef UB_ON_WINDOWS
148 if ((rs = mmap(NULL, sizeof(*rs), PROT_READ|PROT_WRITE,
149 MAP_ANON|MAP_PRIVATE, -1, 0)) == MAP_FAILED)
151 #ifdef MAP_INHERIT_ZERO
152 if (minherit(rs, sizeof(*rs), MAP_INHERIT_ZERO) == -1)
156 rs = malloc(sizeof(*rs));
162 #ifndef UB_ON_WINDOWS
163 if ((rsx = mmap(NULL, sizeof(*rsx), PROT_READ|PROT_WRITE,
164 MAP_ANON|MAP_PRIVATE, -1, 0)) == MAP_FAILED)
167 rsx = malloc(sizeof(*rsx));
173 chacha_keysetup(&rsx->rs_chacha, buf, KEYSZ * 8, 0);
174 chacha_ivsetup(&rsx->rs_chacha, buf + KEYSZ);
180 u_char rnd[KEYSZ + IVSZ];
182 if (getentropy(rnd, sizeof rnd) == -1) {
183 if(errno != ENOSYS ||
184 fallback_getentropy_urandom(rnd, sizeof rnd) == -1) {
188 exit(9); /* windows */
194 _rs_init(rnd, sizeof(rnd));
196 _rs_rekey(rnd, sizeof(rnd));
197 explicit_bzero(rnd, sizeof(rnd)); /* discard source seed */
199 /* invalidate rs_buf */
201 memset(rsx->rs_buf, 0, sizeof(rsx->rs_buf));
203 rs->rs_count = 1600000;
207 _rs_stir_if_needed(size_t len)
209 #ifndef MAP_INHERIT_ZERO
210 static pid_t _rs_pid = 0;
211 pid_t pid = getpid();
213 /* If a system lacks MAP_INHERIT_ZERO, resort to getpid() */
214 if (_rs_pid == 0 || _rs_pid != pid) {
220 if (!rs || rs->rs_count <= len)
222 if (rs->rs_count <= len)
229 _rs_rekey(u_char *dat, size_t datlen)
231 #ifndef KEYSTREAM_ONLY
232 memset(rsx->rs_buf, 0, sizeof(rsx->rs_buf));
234 /* fill rs_buf with the keystream */
235 chacha_encrypt_bytes(&rsx->rs_chacha, rsx->rs_buf,
236 rsx->rs_buf, sizeof(rsx->rs_buf));
237 /* mix in optional user provided data */
241 m = arc4_min(datlen, KEYSZ + IVSZ);
242 for (i = 0; i < m; i++)
243 rsx->rs_buf[i] ^= dat[i];
245 /* immediately reinit for backtracking resistance */
246 _rs_init(rsx->rs_buf, KEYSZ + IVSZ);
247 memset(rsx->rs_buf, 0, KEYSZ + IVSZ);
248 rs->rs_have = sizeof(rsx->rs_buf) - KEYSZ - IVSZ;
252 _rs_random_buf(void *_buf, size_t n)
254 u_char *buf = (u_char *)_buf;
258 _rs_stir_if_needed(n);
260 if (rs->rs_have > 0) {
261 m = arc4_min(n, rs->rs_have);
262 keystream = rsx->rs_buf + sizeof(rsx->rs_buf)
264 memcpy(buf, keystream, m);
265 memset(keystream, 0, m);
270 if (rs->rs_have == 0)
276 _rs_random_u32(uint32_t *val)
279 _rs_stir_if_needed(sizeof(*val));
280 if (rs->rs_have < sizeof(*val))
282 keystream = rsx->rs_buf + sizeof(rsx->rs_buf) - rs->rs_have;
283 memcpy(val, keystream, sizeof(*val));
284 memset(keystream, 0, sizeof(*val));
285 rs->rs_have -= sizeof(*val);
294 _rs_random_u32(&val);
300 arc4random_buf(void *buf, size_t n)
303 _rs_random_buf(buf, n);