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

3 files changed, 161 insertions, 0 deletions

diff --git a/src/lib/rng/rdrand_rng/info.txt b/src/lib/rng/rdrand_rng/info.txt
new file mode 100644
index 000000000..2e597ebec
--- /dev/null
+++ b/src/lib/rng/rdrand_rng/info.txt
@@ -0,0 +1,16 @@
+define RDRAND_RNG 20160619
+
+need_isa rdrand
+
+<arch>
+x86_32
+x86_64
+</arch>
+
+<cc>
+gcc
+clang
+icc
+msvc
+</cc>
+
diff --git a/src/lib/rng/rdrand_rng/rdrand_rng.cpp b/src/lib/rng/rdrand_rng/rdrand_rng.cpp
new file mode 100644
index 000000000..4d2e51cf8
--- /dev/null
+++ b/src/lib/rng/rdrand_rng/rdrand_rng.cpp
@@ -0,0 +1,84 @@
+/**
+* RDRAND RNG
+* (C) 2016 Jack Lloyd
+*
+* Botan is released under the Simplified BSD License (see license.txt)
+*/
+
+#include <botan/rdrand_rng.h>
+#include <botan/loadstor.h>
+#include <botan/cpuid.h>
+
+#if !defined(BOTAN_USE_GCC_INLINE_ASM)
+  #include <immintrin.h>
+#endif
+
+namespace Botan {
+
+RDRAND_RNG::RDRAND_RNG()
+   {
+   if(!CPUID::has_rdrand())
+      throw Exception("Current CPU does not support RDRAND instruction");
+   }
+
+//static
+uint32_t RDRAND_RNG::rdrand()
+   {
+   bool ok = false;
+   uint32_t r = rdrand_status(ok);
+
+   while(!ok)
+      {
+      r = rdrand_status(ok);
+      }
+
+   return r;
+   }
+
+//static
+uint32_t RDRAND_RNG::rdrand_status(bool& ok)
+   {
+   ok = false;
+   uint32_t r = 0;
+
+   for(size_t i = 0; i != BOTAN_ENTROPY_RDRAND_RETRIES; ++i)
+      {
+#if defined(BOTAN_USE_GCC_INLINE_ASM)
+      int cf = 0;
+
+      // Encoding of rdrand %eax
+      asm(".byte 0x0F, 0xC7, 0xF0; adcl $0,%1" :
+          "=a" (r), "=r" (cf) : "0" (r), "1" (cf) : "cc");
+#else
+      int cf = _rdrand32_step(&r);
+#endif
+      if(1 == cf)
+         {
+         ok = true;
+         return r;
+         }
+      }
+
+   return 0;
+   }
+
+void RDRAND_RNG::randomize(uint8_t out[], size_t out_len)
+   {
+   while(out_len >= 4)
+      {
+      uint32_t r = RDRAND_RNG::rdrand();
+
+      store_le(r, out);
+      out += 4;
+      out_len -= 4;
+      }
+
+   if(out_len) // between 1 and 3 trailing bytes
+      {
+      uint32_t r = RDRAND_RNG::rdrand();
+      for(size_t i = 0; i != out_len; ++i)
+         out[i] = get_byte(i, r);
+      }
+   }
+
+}
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