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)
144 if (n < KEYSZ + IVSZ)
148 #ifndef UB_ON_WINDOWS
149 if ((rs = mmap(NULL, sizeof(*rs), PROT_READ|PROT_WRITE,
150 MAP_ANON|MAP_PRIVATE, -1, 0)) == MAP_FAILED)
152 #ifdef MAP_INHERIT_ZERO
153 if (minherit(rs, sizeof(*rs), MAP_INHERIT_ZERO) == -1)
157 rs = malloc(sizeof(*rs));
163 #ifndef UB_ON_WINDOWS
164 if ((rsx = mmap(NULL, sizeof(*rsx), PROT_READ|PROT_WRITE,
165 MAP_ANON|MAP_PRIVATE, -1, 0)) == MAP_FAILED)
168 rsx = malloc(sizeof(*rsx));
174 chacha_keysetup(&rsx->rs_chacha, buf, KEYSZ * 8, 0);
175 chacha_ivsetup(&rsx->rs_chacha, buf + KEYSZ);
181 u_char rnd[KEYSZ + IVSZ];
183 if (getentropy(rnd, sizeof rnd) == -1) {
184 if(errno != ENOSYS ||
185 fallback_getentropy_urandom(rnd, sizeof rnd) == -1) {
189 exit(9); /* windows */
195 _rs_init(rnd, sizeof(rnd));
197 _rs_rekey(rnd, sizeof(rnd));
198 explicit_bzero(rnd, sizeof(rnd)); /* discard source seed */
200 /* invalidate rs_buf */
202 memset(rsx->rs_buf, 0, sizeof(rsx->rs_buf));
204 rs->rs_count = 1600000;
208 _rs_stir_if_needed(size_t len)
210 #ifndef MAP_INHERIT_ZERO
211 static pid_t _rs_pid = 0;
212 pid_t pid = getpid();
214 /* If a system lacks MAP_INHERIT_ZERO, resort to getpid() */
215 if (_rs_pid == 0 || _rs_pid != pid) {
221 if (!rs || rs->rs_count <= len)
223 if (rs->rs_count <= len)
230 _rs_rekey(u_char *dat, size_t datlen)
232 #ifndef KEYSTREAM_ONLY
233 memset(rsx->rs_buf, 0, sizeof(rsx->rs_buf));
235 /* fill rs_buf with the keystream */
236 chacha_encrypt_bytes(&rsx->rs_chacha, rsx->rs_buf,
237 rsx->rs_buf, sizeof(rsx->rs_buf));
238 /* mix in optional user provided data */
242 m = arc4_min(datlen, KEYSZ + IVSZ);
243 for (i = 0; i < m; i++)
244 rsx->rs_buf[i] ^= dat[i];
246 /* immediately reinit for backtracking resistance */
247 _rs_init(rsx->rs_buf, KEYSZ + IVSZ);
248 memset(rsx->rs_buf, 0, KEYSZ + IVSZ);
249 rs->rs_have = sizeof(rsx->rs_buf) - KEYSZ - IVSZ;
253 _rs_random_buf(void *_buf, size_t n)
255 u_char *buf = (u_char *)_buf;
259 _rs_stir_if_needed(n);
261 if (rs->rs_have > 0) {
262 m = arc4_min(n, rs->rs_have);
263 keystream = rsx->rs_buf + sizeof(rsx->rs_buf)
265 memcpy(buf, keystream, m);
266 memset(keystream, 0, m);
271 if (rs->rs_have == 0)
277 _rs_random_u32(uint32_t *val)
280 _rs_stir_if_needed(sizeof(*val));
281 if (rs->rs_have < sizeof(*val))
283 keystream = rsx->rs_buf + sizeof(rsx->rs_buf) - rs->rs_have;
284 memcpy(val, keystream, sizeof(*val));
285 memset(keystream, 0, sizeof(*val));
286 rs->rs_have -= sizeof(*val);
295 _rs_random_u32(&val);
301 arc4random_buf(void *buf, size_t n)
304 _rs_random_buf(buf, n);