1/*	$OpenBSD$	*/
2
3/*
4 * Copyright (c) 2014, Theo de Raadt <deraadt@openbsd.org>
5 * Copyright (c) 2014, Bob Beck <beck@obtuse.com>
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
20#include <windows.h>
21#include <errno.h>
22#include <stdint.h>
23#include <sys/types.h>
24#include <wincrypt.h>
25#include <process.h>
26
27int	getentropy(void *buf, size_t len);
28
29/*
30 * On Windows, CryptGenRandom is supposed to be a well-seeded
31 * cryptographically strong random number generator.
32 */
33int
34getentropy(void *buf, size_t len)
35{
36	HCRYPTPROV provider;
37
38	if (len > 256) {
39		errno = EIO;
40		return -1;
41	}
42
43	if (CryptAcquireContext(&provider, NULL, NULL, PROV_RSA_FULL,
44	    CRYPT_VERIFYCONTEXT) == 0)
45		goto fail;
46	if (CryptGenRandom(provider, len, buf) == 0) {
47		CryptReleaseContext(provider, 0);
48		goto fail;
49	}
50	CryptReleaseContext(provider, 0);
51	return (0);
52
53fail:
54	errno = EIO;
55	return (-1);
56}
57