1 /* $OpenBSD: arc4random.c,v 1.54 2015/09/13 08:31:47 guenther 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>
7 * Copyright (c) 2014, Theo de Raadt <deraadt@openbsd.org>
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.
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.
23 * ChaCha based random number generator for OpenBSD.
26 #include <sys/cdefs.h>
27 __FBSDID("$FreeBSD$");
29 #include "namespace.h"
38 #include <sys/types.h>
41 #include "libc_private.h"
42 #include "un-namespace.h"
45 #define KEYSTREAM_ONLY
48 #define minimum(a, b) ((a) < (b) ? (a) : (b))
50 #if defined(__GNUC__) || defined(_MSC_VER)
51 #define inline __inline
52 #else /* __GNUC__ || _MSC_VER */
54 #endif /* !__GNUC__ && !_MSC_VER */
59 #define RSBUFSZ (16*BLOCKSZ)
61 /* Marked INHERIT_ZERO, so zero'd out in fork children. */
63 size_t rs_have; /* valid bytes at end of rs_buf */
64 size_t rs_count; /* bytes till reseed */
67 /* Maybe be preserved in fork children, if _rs_allocate() decides. */
69 chacha_ctx rs_chacha; /* chacha context for random keystream */
70 u_char rs_buf[RSBUFSZ]; /* keystream blocks */
73 static inline int _rs_allocate(struct _rs **, struct _rsx **);
74 static inline void _rs_forkdetect(void);
75 #include "arc4random.h"
77 static inline void _rs_rekey(u_char *dat, size_t datlen);
80 _rs_init(u_char *buf, size_t n)
86 if (_rs_allocate(&rs, &rsx) == -1)
90 chacha_keysetup(&rsx->rs_chacha, buf, KEYSZ * 8);
91 chacha_ivsetup(&rsx->rs_chacha, buf + KEYSZ, NULL);
97 u_char rnd[KEYSZ + IVSZ];
99 if (getentropy(rnd, sizeof rnd) == -1)
103 _rs_init(rnd, sizeof(rnd));
105 _rs_rekey(rnd, sizeof(rnd));
106 explicit_bzero(rnd, sizeof(rnd)); /* discard source seed */
108 /* invalidate rs_buf */
110 memset(rsx->rs_buf, 0, sizeof(rsx->rs_buf));
112 rs->rs_count = 1600000;
116 _rs_stir_if_needed(size_t len)
119 if (!rs || rs->rs_count <= len)
121 if (rs->rs_count <= len)
128 _rs_rekey(u_char *dat, size_t datlen)
130 #ifndef KEYSTREAM_ONLY
131 memset(rsx->rs_buf, 0, sizeof(rsx->rs_buf));
133 /* fill rs_buf with the keystream */
134 chacha_encrypt_bytes(&rsx->rs_chacha, rsx->rs_buf,
135 rsx->rs_buf, sizeof(rsx->rs_buf));
136 /* mix in optional user provided data */
140 m = minimum(datlen, KEYSZ + IVSZ);
141 for (i = 0; i < m; i++)
142 rsx->rs_buf[i] ^= dat[i];
144 /* immediately reinit for backtracking resistance */
145 _rs_init(rsx->rs_buf, KEYSZ + IVSZ);
146 memset(rsx->rs_buf, 0, KEYSZ + IVSZ);
147 rs->rs_have = sizeof(rsx->rs_buf) - KEYSZ - IVSZ;
151 _rs_random_buf(void *_buf, size_t n)
153 u_char *buf = (u_char *)_buf;
157 _rs_stir_if_needed(n);
159 if (rs->rs_have > 0) {
160 m = minimum(n, rs->rs_have);
161 keystream = rsx->rs_buf + sizeof(rsx->rs_buf)
163 memcpy(buf, keystream, m);
164 memset(keystream, 0, m);
169 if (rs->rs_have == 0)
175 _rs_random_u32(uint32_t *val)
179 _rs_stir_if_needed(sizeof(*val));
180 if (rs->rs_have < sizeof(*val))
182 keystream = rsx->rs_buf + sizeof(rsx->rs_buf) - rs->rs_have;
183 memcpy(val, keystream, sizeof(*val));
184 memset(keystream, 0, sizeof(*val));
185 rs->rs_have -= sizeof(*val);
194 _rs_random_u32(&val);
200 arc4random_buf(void *buf, size_t n)
203 _rs_random_buf(buf, n);