1 /*	$OpenBSD: getentropy_netbsd.c,v 1.4 2020/10/12 22:08:33 deraadt 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  */
32 static size_t
33 getentropy_sysctl(u_char *buf, size_t size)
34 {
35 	const int mib[2] = { CTL_KERN, KERN_ARND };
36 	size_t len, done;
37 
38 	done = 0;
39 
40 	do {
41 		len = size;
42 		if (sysctl(mib, 2, buf, &len, NULL, 0) == -1)
43 			return (done);
44 		done += len;
45 		buf += len;
46 		size -= len;
47 	} while (size > 0);
48 
49 	return (done);
50 }
51 
52 int
53 getentropy(void *buf, size_t len)
54 {
55 	if (len <= 256 &&
56 	    getentropy_sysctl(buf, len) == len) {
57 		return (0);
58 	}
59 
60 	errno = EIO;
61 	return (-1);
62 }
63