1/*	$OpenBSD: getentropy_freebsd.c,v 1.3 2016/08/07 03:27:21 tb Exp $	*/
2
3/*
4 * Copyright (c) 2014 Pawel Jakub Dawidek <pjd@FreeBSD.org>
5 * Copyright (c) 2014 Brent Cook <bcook@openbsd.org>
6 *
7 * Permission to use, copy, modify, and distribute this software for any
8 * purpose with or without fee is hereby granted, provided that the above
9 * copyright notice and this permission notice appear in all copies.
10 *
11 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
12 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
13 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
14 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
15 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
16 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
17 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
18 *
19 * Emulation of getentropy(2) as documented at:
20 * http://man.openbsd.org/getentropy.2
21 */
22
23#include <sys/types.h>
24#include <sys/sysctl.h>
25
26#include <errno.h>
27#include <stddef.h>
28
29/*
30 * Derived from lib/libc/gen/arc4random.c from FreeBSD.
31 */
32static size_t
33getentropy_sysctl(u_char *buf, size_t size)
34{
35	int mib[2];
36	size_t len, done;
37
38	mib[0] = CTL_KERN;
39	mib[1] = KERN_ARND;
40	done = 0;
41
42	do {
43		len = size;
44		if (sysctl(mib, 2, buf, &len, NULL, 0) == -1)
45			return (done);
46		done += len;
47		buf += len;
48		size -= len;
49	} while (size > 0);
50
51	return (done);
52}
53
54int
55getentropy(void *buf, size_t len)
56{
57	if (len <= 256 && getentropy_sysctl(buf, len) == len)
58		return (0);
59
60	errno = EIO;
61	return (-1);
62}
63