fixes #1083 Random number improvements

1 files changed, 40 insertions, 0 deletions

diff --git a/src/platform/posix/posix_rand_getrandom.c b/src/platform/posix/posix_rand_getrandom.c
new file mode 100644
index 00000000..489b2c76
--- /dev/null
+++ b/src/platform/posix/posix_rand_getrandom.c
@@ -0,0 +1,40 @@
+//
+// Copyright 2020 Staysail Systems, Inc. <info@staysail.tech>
+//
+// This software is supplied under the terms of the MIT License, a
+// copy of which should be located in the distribution where this
+// file was obtained (LICENSE.txt).  A copy of the license may also be
+// found online at https://opensource.org/licenses/MIT.
+//
+
+// getrandom is not as nice as arc4random, but on platforms where it
+// exists and arc4random does not, we should use it.
+//
+// getrandom will block only if the urandom device is not seeded yet.
+// That can only happen during very early boot (earlier than we should
+// normally be running.  This is the only time it can fail with correct
+// arguments, and then only if it is interrupted with a signal.
+
+#include <sys/random.h>
+
+#include "core/nng_impl.h"
+
+#ifdef NNG_HAVE_GETRANDOM
+
+uint32_t
+nni_random(void)
+{
+	uint32_t val;
+
+	// Documentation claims that as long as we are not using
+	// GRND_RANDOM and buflen < 256, this should never fail.
+	// The exception here is that we could fail if for some
+	// reason we got a signal while blocked at very early boot
+	// (i.e. /dev/urandom was not yet seeded).
+	if (getrandom(&val, sizeof(val), 0) != sizeof(val)) {
+		nni_panic("getrandom failed");
+	}
+	return (val);
+}
+
+#endif
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