src/win32/rand.c

   1 /*****************************************************************************
   2  * rand.c : non-predictible random bytes generator
   3  *****************************************************************************
   4  * Copyright © 2007 Rémi Denis-Courmont
   5  * $Id$
   6  *
   7  * This program is free software; you can redistribute it and/or modify it
   8  * under the terms of the GNU Lesser General Public License as published by
   9  * the Free Software Foundation; either version 2.1 of the License, or
  10  * (at your option) any later version.
  11  *
  12  * This program is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  15  * GNU Lesser General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU Lesser General Public License
  18  * along with this program; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
  20  *****************************************************************************/
  21
  22 #ifdef HAVE_CONFIG_H
  23 # include "config.h"
  24 #endif
  25
  26 #include <vlc_common.h>
  27 #include <vlc_rand.h>
  28
  29 #include <wincrypt.h>
  30
  31 void vlc_rand_bytes (void *buf, size_t len)
  32 {
  33     HCRYPTPROV hProv;
  34     size_t count = len;
  35     uint8_t *p_buf = (uint8_t *)buf;
  36
  37     /* fill buffer with pseudo-random data */
  38     while (count > 0)
  39     {
  40         unsigned int val;
  41         val = rand();
  42         if (count < sizeof (val))
  43         {
  44             memcpy (p_buf, &val, count);
  45             break;
  46         }
  47
  48         memcpy (p_buf, &val, sizeof (val));
  49         count -= sizeof (val);
  50         p_buf += sizeof (val);
  51     }
  52
  53     /* acquire default encryption context */
  54     if( CryptAcquireContext(
  55         &hProv,                 // Variable to hold returned handle.
  56         NULL,                   // Use default key container.
  57         MS_DEF_PROV,            // Use default CSP.
  58         PROV_RSA_FULL,          // Type of provider to acquire.
  59         CRYPT_VERIFYCONTEXT) )  // Flag values
  60     {
  61         /* fill buffer with pseudo-random data, intial buffer content
  62            is used as auxillary random seed */
  63         CryptGenRandom(hProv, len, buf);
  64         CryptReleaseContext(hProv, 0);
  65     }
  66 }