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
30 int 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 */
36 int
getentropy(void * buf,size_t len)37 getentropy(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
56 fail:
57 errno = EIO;
58 return (-1);
59 }
60