[rng] Add ANS X9.82 RBG wrapper functions

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/include/ipxe/rbg.h

@@ -0,0 +1,43 @@
+#ifndef _IPXE_RBG_H
+#define _IPXE_RBG_H
+
+/** @file
+ *
+ * RBG mechanism
+ *
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER );
+
+#include <stdint.h>
+#include <ipxe/drbg.h>
+
+/** An RBG */
+struct random_bit_generator {
+	/** DRBG state */
+	struct drbg_state state;
+};
+
+extern struct random_bit_generator rbg;
+
+/**
+ * Generate bits using RBG
+ *
+ * @v additional	Additional input
+ * @v additional_len	Length of additional input
+ * @v prediction_resist	Prediction resistance is required
+ * @v data		Output buffer
+ * @v len		Length of output buffer
+ * @ret rc		Return status code
+ *
+ * This is the RBG_Generate function defined in ANS X9.82 Part 4
+ * (April 2011 Draft) Section 9.1.2.2.
+ */
+static inline int rbg_generate ( const void *additional, size_t additional_len,
+				 int prediction_resist, void *data,
+				 size_t len ) {
+	return drbg_generate ( &rbg.state, additional, additional_len,
+			       prediction_resist, data, len );
+}
+
+#endif /* _IPXE_RBG_H */