lib/libcrypto/arc4random/getentropy_win.c

   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
  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 }