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__ */
55 #define RSBUFSZ (16*BLOCKSZ)
57 /* Marked MAP_INHERIT_ZERO, so zero'd out in fork children. */
59 size_t rs_have; /* valid bytes at end of rs_buf */
60 size_t rs_count; /* bytes till reseed */
63 /* Preserved in fork children. */
65 chacha_ctx rs_chacha; /* chacha context for random keystream */
66 u_char rs_buf[RSBUFSZ]; /* keystream blocks */
69 static inline void _rs_rekey(u_char *dat, size_t datlen);
72 _rs_init(u_char *buf, size_t n)
79 if ((rs = mmap(NULL, sizeof(*rs), PROT_READ|PROT_WRITE,
80 MAP_ANON|MAP_PRIVATE, -1, 0)) == MAP_FAILED)
82 #ifdef MAP_INHERIT_ZERO
83 if (minherit(rs, sizeof(*rs), MAP_INHERIT_ZERO) == -1)
87 rs = malloc(sizeof(*rs));
94 if ((rsx = mmap(NULL, sizeof(*rsx), PROT_READ|PROT_WRITE,
95 MAP_ANON|MAP_PRIVATE, -1, 0)) == MAP_FAILED)
98 rsx = malloc(sizeof(*rsx));
104 chacha_keysetup(&rsx->rs_chacha, buf, KEYSZ * 8, 0);
105 chacha_ivsetup(&rsx->rs_chacha, buf + KEYSZ);
111 u_char rnd[KEYSZ + IVSZ];
113 if (getentropy(rnd, sizeof rnd) == -1) {
117 exit(9); /* windows */
122 _rs_init(rnd, sizeof(rnd));
124 _rs_rekey(rnd, sizeof(rnd));
125 explicit_bzero(rnd, sizeof(rnd)); /* discard source seed */
127 /* invalidate rs_buf */
129 memset(rsx->rs_buf, 0, sizeof(rsx->rs_buf));
131 rs->rs_count = 1600000;
135 _rs_stir_if_needed(size_t len)
137 #ifndef MAP_INHERIT_ZERO
138 static pid_t _rs_pid = 0;
139 pid_t pid = getpid();
141 /* If a system lacks MAP_INHERIT_ZERO, resort to getpid() */
142 if (_rs_pid == 0 || _rs_pid != pid) {
148 if (!rs || rs->rs_count <= len)
150 if (rs->rs_count <= len)
157 _rs_rekey(u_char *dat, size_t datlen)
159 #ifndef KEYSTREAM_ONLY
160 memset(rsx->rs_buf, 0, sizeof(rsx->rs_buf));
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 */
169 m = arc4_min(datlen, KEYSZ + IVSZ);
170 for (i = 0; i < m; i++)
171 rsx->rs_buf[i] ^= dat[i];
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;
180 _rs_random_buf(void *_buf, size_t n)
182 u_char *buf = (u_char *)_buf;
186 _rs_stir_if_needed(n);
188 if (rs->rs_have > 0) {
189 m = arc4_min(n, rs->rs_have);
190 keystream = rsx->rs_buf + sizeof(rsx->rs_buf)
192 memcpy(buf, keystream, m);
193 memset(keystream, 0, m);
198 if (rs->rs_have == 0)
204 _rs_random_u32(uint32_t *val)
207 _rs_stir_if_needed(sizeof(*val));
208 if (rs->rs_have < sizeof(*val))
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);
222 _rs_random_u32(&val);
228 arc4random_buf(void *buf, size_t n)
231 _rs_random_buf(buf, n);