--- /dev/null
+/* Test of getting random bytes.
+ Copyright (C) 2020 Free Software Foundation, Inc.
+
+ This program is free software: you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published by
+ the Free Software Foundation; either version 3 of the License, or
+ (at your option) any later version.
+
+ This program is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with this program. If not, see <https://www.gnu.org/licenses/>. */
+
+/* Written by Bruno Haible. */
+
+#include <config.h>
+
+#include <sys/random.h>
+
+#include "signature.h"
+SIGNATURE_CHECK (getrandom, ssize_t, (void *, size_t, unsigned int));
+
+#include <errno.h>
+#include <string.h>
+
+#include "macros.h"
+
+int
+main (void)
+{
+ char buf1[8];
+ char buf2[8];
+ char large_buf[100000];
+ ssize_t ret;
+
+ /* Check that different calls produce different results (with a high
+ probability). */
+ ret = getrandom (buf1, sizeof (buf1), 0);
+ if (ret < 0)
+ ASSERT (errno == ENOSYS);
+ else
+ {
+ ret = getrandom (buf2, sizeof (buf2), 0);
+ if (ret < 0)
+ ASSERT (errno == ENOSYS);
+ else
+ {
+ /* It is very unlikely that two calls to getrandom produce the
+ same results. */
+ ASSERT (memcmp (buf1, buf2, sizeof (buf1)) != 0);
+ }
+ }
+
+ /* Likewise with the "truly random" number generator. */
+ ret = getrandom (buf1, sizeof (buf1), GRND_RANDOM);
+ if (ret < 0)
+ ASSERT (errno == ENOSYS);
+ else
+ {
+ ret = getrandom (buf2, sizeof (buf2), GRND_RANDOM);
+ if (ret < 0)
+ ASSERT (errno == ENOSYS);
+ else
+ {
+ /* It is very unlikely that two calls to getrandom produce the
+ same results. */
+ ASSERT (memcmp (buf1, buf2, sizeof (buf1)) != 0);
+ }
+ }
+
+ /* Check that GRND_NONBLOCK works. */
+ ret = getrandom (large_buf, sizeof (large_buf), GRND_RANDOM | GRND_NONBLOCK);
+ /* It is very unlikely that so many truly random bytes were ready. */
+ if (ret < 0)
+ ASSERT (errno == ENOSYS || errno == EAGAIN);
+ else
+ ASSERT (ret > 0 && ret < sizeof (large_buf));
+
+ return 0;
+}