1 files changed, 84 insertions, 0 deletions
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);
+      }
+   }
+
+}