Annotate places depending on strong random numbers

This commit adds a new wrapper, random_get_bytes(), that is currently
defined to use os_get_random() as is. The places using
random_get_bytes() depend on the returned value being strong random
number, i.e., something that is infeasible for external device to
figure out. These values are used either directly as a key or as
nonces/challenges that are used as input for key derivation or
authentication.

The remaining direct uses of os_get_random() do not need as strong
random numbers to function correctly.

src/crypto/random.h

@@ -0,0 +1,20 @@
+/*
+ * Random number generator
+ * Copyright (c) 2010, Jouni Malinen <j@w1.fi>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * Alternatively, this software may be distributed under the terms of BSD
+ * license.
+ *
+ * See README and COPYING for more details.
+ */
+
+#ifndef RANDOM_H
+#define RANDOM_H
+
+#define random_get_bytes(b, l) os_get_random((b), (l))
+
+#endif /* RANDOM_H */