getentropy_win.c revision 356345 
1/*	$OpenBSD: getentropy_win.c,v 1.5 2016/08/07 03:27:21 tb Exp $	*/
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 * Emulation of getentropy(2) as documented at:
20 * http://man.openbsd.org/getentropy.2
21 */
22
23#include <windows.h>
24#include <errno.h>
25#include <stdint.h>
26#include <sys/types.h>
27#include <wincrypt.h>
28#include <process.h>
29
30int	getentropy(void *buf, size_t len);
31
32/*
33 * On Windows, CryptGenRandom is supposed to be a well-seeded
34 * cryptographically strong random number generator.
35 */
36int
37getentropy(void *buf, size_t len)
38{
39	HCRYPTPROV provider;
40
41	if (len > 256) {
42		errno = EIO;
43		return (-1);
44	}
45
46	if (CryptAcquireContext(&provider, NULL, NULL, PROV_RSA_FULL,
47	    CRYPT_VERIFYCONTEXT) == 0)
48		goto fail;
49	if (CryptGenRandom(provider, len, buf) == 0) {
50		CryptReleaseContext(provider, 0);
51		goto fail;
52	}
53	CryptReleaseContext(provider, 0);
54	return (0);
55
56fail:
57	errno = EIO;
58	return (-1);
59}
60