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/fault.h"
  24 #include "lib/util/genrand.h"
  25
  26 #include <gnutls/gnutls.h>
  27 #include <gnutls/crypto.h>
  28
  29 /*
  30  * Details about the GnuTLS CSPRNG:
  31  *
  32  * https://nikmav.blogspot.com/2017/03/improving-by-simplifying-gnutls-prng.html
  33  */
  34
  35
  36 _NORETURN_ static void genrand_panic(int err,
  37                                      const char *location,
  38                                      const char *func)
  39 {
  40         char buf[200];
  41         snprintf(buf, sizeof(buf),
  42                  "%s:%s: GnuTLS could not generate a random buffer: %s [%d]\n",
  43                  location, func, gnutls_strerror_name(err), err);
  44         smb_panic(buf);
  45 }
  46
  47
  48 _PUBLIC_ void generate_random_buffer(uint8_t *out, size_t len)
  49 {
  50         /* Random number generator for temporary keys. */
  51         int ret = gnutls_rnd(GNUTLS_RND_RANDOM, out, len);
  52         if (ret != 0) {
  53                 genrand_panic(ret, __location__, __func__);
  54         }
  55 }
  56
  57 _PUBLIC_ void generate_secret_buffer(uint8_t *out, size_t len)
  58 {
  59         /*
  60          * Random number generator for long term keys.
  61          *
  62          * The key generator, will re-seed after a fixed amount of bytes is
  63          * generated (typically less than the nonce), and will also re-seed
  64          * based on time, i.e., after few hours of operation without reaching
  65          * the limit for a re-seed. For its re-seed it mixes data obtained
  66          * from the OS random device with the previous key.
  67          */
  68         int ret = gnutls_rnd(GNUTLS_RND_KEY, out, len);
  69         if (ret != 0) {
  70                 genrand_panic(ret, __location__, __func__);
  71         }
  72 }
  73
  74 _PUBLIC_ void generate_nonce_buffer(uint8_t *out, size_t len)
  75 {
  76         /*
  77          * Random number generator for nonce and initialization vectors.
  78          *
  79          * The nonce generator will reseed after outputting a fixed amount of
  80          * bytes (typically few megabytes), or after few hours of operation
  81          * without reaching the limit has passed.
  82          */
  83         int ret = gnutls_rnd(GNUTLS_RND_NONCE, out, len);
  84         if (ret != 0) {
  85                 genrand_panic(ret, __location__, __func__);
  86         }
  87 }