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 
27 int	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  */
33 int
34 getentropy(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 
53 fail:
54 	errno = EIO;
55 	return (-1);
56 }
57