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 _rs_init(u_char *buf, size_t n)
82 if ((rs = mmap(NULL, sizeof(*rs), PROT_READ|PROT_WRITE,
83 MAP_ANON|MAP_PRIVATE, -1, 0)) == MAP_FAILED)
85 #ifdef MAP_INHERIT_ZERO
86 if (minherit(rs, sizeof(*rs), MAP_INHERIT_ZERO) == -1)
90 rs = malloc(sizeof(*rs));
97 if ((rsx = mmap(NULL, sizeof(*rsx), PROT_READ|PROT_WRITE,
98 MAP_ANON|MAP_PRIVATE, -1, 0)) == MAP_FAILED)
101 rsx = malloc(sizeof(*rsx));
107 chacha_keysetup(&rsx->rs_chacha, buf, KEYSZ * 8, 0);
108 chacha_ivsetup(&rsx->rs_chacha, buf + KEYSZ);
114 u_char rnd[KEYSZ + IVSZ];
116 if (getentropy(rnd, sizeof rnd) == -1) {
120 exit(9); /* windows */
125 _rs_init(rnd, sizeof(rnd));
127 _rs_rekey(rnd, sizeof(rnd));
128 explicit_bzero(rnd, sizeof(rnd)); /* discard source seed */
130 /* invalidate rs_buf */
132 memset(rsx->rs_buf, 0, sizeof(rsx->rs_buf));
134 rs->rs_count = 1600000;
138 _rs_stir_if_needed(size_t len)
140 #ifndef MAP_INHERIT_ZERO
141 static pid_t _rs_pid = 0;
142 pid_t pid = getpid();
144 /* If a system lacks MAP_INHERIT_ZERO, resort to getpid() */
145 if (_rs_pid == 0 || _rs_pid != pid) {
151 if (!rs || rs->rs_count <= len)
153 if (rs->rs_count <= len)
160 _rs_rekey(u_char *dat, size_t datlen)
162 #ifndef KEYSTREAM_ONLY
163 memset(rsx->rs_buf, 0, sizeof(rsx->rs_buf));
165 /* fill rs_buf with the keystream */
166 chacha_encrypt_bytes(&rsx->rs_chacha, rsx->rs_buf,
167 rsx->rs_buf, sizeof(rsx->rs_buf));
168 /* mix in optional user provided data */
172 m = arc4_min(datlen, KEYSZ + IVSZ);
173 for (i = 0; i < m; i++)
174 rsx->rs_buf[i] ^= dat[i];
176 /* immediately reinit for backtracking resistance */
177 _rs_init(rsx->rs_buf, KEYSZ + IVSZ);
178 memset(rsx->rs_buf, 0, KEYSZ + IVSZ);
179 rs->rs_have = sizeof(rsx->rs_buf) - KEYSZ - IVSZ;
183 _rs_random_buf(void *_buf, size_t n)
185 u_char *buf = (u_char *)_buf;
189 _rs_stir_if_needed(n);
191 if (rs->rs_have > 0) {
192 m = arc4_min(n, rs->rs_have);
193 keystream = rsx->rs_buf + sizeof(rsx->rs_buf)
195 memcpy(buf, keystream, m);
196 memset(keystream, 0, m);
201 if (rs->rs_have == 0)
207 _rs_random_u32(uint32_t *val)
210 _rs_stir_if_needed(sizeof(*val));
211 if (rs->rs_have < sizeof(*val))
213 keystream = rsx->rs_buf + sizeof(rsx->rs_buf) - rs->rs_have;
214 memcpy(val, keystream, sizeof(*val));
215 memset(keystream, 0, sizeof(*val));
216 rs->rs_have -= sizeof(*val);
225 _rs_random_u32(&val);
231 arc4random_buf(void *buf, size_t n)
234 _rs_random_buf(buf, n);