Add RDRAND_RNG

For those that are willing to trust uninspectible hardware. :)

Changes RDRAND entropy source to call RDRAND_RNG

Add --rdrand flag to rng cmdlet

1 files changed, 61 insertions, 0 deletions

diff --git a/src/lib/rng/rdrand_rng/rdrand_rng.h b/src/lib/rng/rdrand_rng/rdrand_rng.h
new file mode 100644
index 000000000..b9445f28e
--- /dev/null
+++ b/src/lib/rng/rdrand_rng/rdrand_rng.h
@@ -0,0 +1,61 @@
+/**
+* RDRAND RNG
+* (C) 2016 Jack Lloyd
+*
+* Botan is released under the Simplified BSD License (see license.txt)
+*/
+
+#ifndef BOTAN_RNG_RDRAND_H_
+#define BOTAN_RNG_RDRAND_H_
+
+#include <botan/rng.h>
+
+namespace Botan {
+
+class BOTAN_DLL RDRAND_RNG : public Hardware_RNG
+   {
+   public:
+      /**
+      * On correctly working hardware, RDRAND is always supposed to
+      * succeed within a set number of retries. If after that many
+      * retries RDRAND has still not suceeded, sets ok = false and
+      * returns 0.
+      */
+      static uint32_t rdrand_status(bool& ok);
+
+      /*
+      * Calls RDRAND until it succeeds, this could hypothetically
+      * loop forever on broken hardware.
+      */
+      static uint32_t rdrand();
+
+      /**
+      * Constructor will throw if CPU does not have RDRAND bit set
+      */
+      RDRAND_RNG();
+
+      /**
+      * Uses RDRAND to produce output
+      */
+      void randomize(uint8_t out[], size_t out_len) override;
+
+      /*
+      * No way to provide entropy to RDRAND generator, so add_entropy is ignored
+      */
+      void add_entropy(const uint8_t[], size_t) override
+         { /* no op */ }
+
+      size_t reseed_with_sources(Entropy_Sources&, size_t,
+                               std::chrono::milliseconds) override
+         { return 0; /* no op */ }
+
+      std::string name() const override { return "RDRAND"; }
+
+      bool is_seeded() const override { return true; }
+
+      void clear() override {}
+   };
+
+}
+
+#endif