lib/util/genrand.c

   1 /*
   2    Unix SMB/CIFS implementation.
   3
   4    Functions to create reasonable random numbers for crypto use.
   5
   6    Copyright (C) Jeremy Allison 2001
   7
   8    This program is free software; you can redistribute it and/or modify
   9    it under the terms of the GNU General Public License as published by
  10    the Free Software Foundation; either version 3 of the License, or
  11    (at your option) any later version.
  12
  13    This program is distributed in the hope that it will be useful,
  14    but WITHOUT ANY WARRANTY; without even the implied warranty of
  15    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16    GNU General Public License for more details.
  17
  18    You should have received a copy of the GNU General Public License
  19    along with this program.  If not, see <http://www.gnu.org/licenses/>.
  20 */
  21
  22 #include "replace.h"
  23 #include "lib/util/genrand.h"
  24
  25 #include <gnutls/gnutls.h>
  26 #include <gnutls/crypto.h>
  27
  28 /*
  29  * Details about the GnuTLS CSPRNG:
  30  *
  31  * https://nikmav.blogspot.com/2017/03/improving-by-simplifying-gnutls-prng.html
  32  */
  33
  34 _PUBLIC_ void generate_random_buffer(uint8_t *out, int len)
  35 {
  36         /* Random number generator for temporary keys. */
  37         gnutls_rnd(GNUTLS_RND_RANDOM, out, len);
  38 }
  39
  40 _PUBLIC_ void generate_secret_buffer(uint8_t *out, int len)
  41 {
  42         /*
  43          * Random number generator for long term keys.
  44          *
  45          * The key generator, will re-seed after a fixed amount of bytes is
  46          * generated (typically less than the nonce), and will also re-seed
  47          * based on time, i.e., after few hours of operation without reaching
  48          * the limit for a re-seed. For its re-seed it mixes mixes data obtained
  49          * from the OS random device with the previous key.
  50          */
  51         gnutls_rnd(GNUTLS_RND_KEY, out, len);
  52 }
  53
  54 _PUBLIC_ void generate_nonce_buffer(uint8_t *out, int len)
  55 {
  56         /*
  57          * Random number generator for nonce and initialization vectors.
  58          *
  59          * The nonce generator will reseed after outputting a fixed amount of
  60          * bytes (typically few megabytes), or after few hours of operation
  61          * without reaching the limit has passed.
  62          */
  63         gnutls_rnd(GNUTLS_RND_NONCE, out, len);
  64 }