tests/test-getrandom.c

   1 /* Test of getting random bytes.
   2    Copyright (C) 2020-2025 Free Software Foundation, Inc.
   3
   4    This program is free software: you can redistribute it and/or modify
   5    it under the terms of the GNU General Public License as published by
   6    the Free Software Foundation, either version 3 of the License, or
   7    (at your option) any later version.
   8
   9    This program is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12    GNU General Public License for more details.
  13
  14    You should have received a copy of the GNU General Public License
  15    along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
  16
  17 /* Written by Bruno Haible.  */
  18
  19 #include <config.h>
  20
  21 #include <sys/random.h>
  22
  23 #include "signature.h"
  24 SIGNATURE_CHECK (getrandom, ssize_t, (void *, size_t, unsigned int));
  25
  26 #include <errno.h>
  27 #include <string.h>
  28
  29 #include "macros.h"
  30
  31 int
  32 main (void)
  33 {
  34   char buf1[8];
  35   char buf2[8];
  36   char large_buf[100000];
  37   ssize_t ret;
  38
  39   /* Check that different calls produce different results (with a high
  40      probability).  */
  41   ret = getrandom (buf1, sizeof (buf1), 0);
  42   if (ret < 0)
  43     ASSERT (errno == ENOSYS);
  44   else
  45     {
  46       ret = getrandom (buf2, sizeof (buf2), 0);
  47       if (ret < 0)
  48         ASSERT (errno == ENOSYS);
  49       else
  50         {
  51           /* It is very unlikely that two calls to getrandom produce the
  52              same results.  */
  53           ASSERT (memcmp (buf1, buf2, sizeof (buf1)) != 0);
  54         }
  55     }
  56
  57   /* Likewise with the "truly random" number generator.  */
  58   ret = getrandom (buf1, sizeof (buf1), GRND_RANDOM);
  59   if (ret < 0)
  60     ASSERT (errno == ENOSYS);
  61   else
  62     {
  63       ret = getrandom (buf2, sizeof (buf2), GRND_RANDOM);
  64       if (ret < 0)
  65         ASSERT (errno == ENOSYS);
  66       else
  67         {
  68           /* It is very unlikely that two calls to getrandom produce the
  69              same results.  */
  70           ASSERT (memcmp (buf1, buf2, sizeof (buf1)) != 0);
  71         }
  72     }
  73
  74   /* Check that GRND_NONBLOCK works.  */
  75   ret = getrandom (large_buf, sizeof (large_buf), GRND_RANDOM | GRND_NONBLOCK);
  76   ASSERT (ret <= (ssize_t) sizeof (large_buf));
  77   /* It is very unlikely that so many truly random bytes were ready.  */
  78   if (ret < 0)
  79     ASSERT (errno == ENOSYS || errno == EAGAIN
  80             || errno == EINVAL /* Solaris */);
  81   else
  82     ASSERT (ret > 0);
  83
  84   if (getrandom (buf1, 1, 0) < 1)
  85     if (getrandom (buf1, 1, GRND_RANDOM) < 1)
  86       {
  87         if (test_exit_status != EXIT_SUCCESS)
  88           return test_exit_status;
  89         fputs ("Skipping test: getrandom is ineffective\n", stderr);
  90         return 77;
  91       }
  92
  93   return test_exit_status;
  94 }