/*

* Entropy Source Polling

* (C) 2008-2010,2015 Jack Lloyd

*

* Botan is released under the Simplified BSD License (see license.txt)

*/

#include <botan/entropy_src.h>

#include <botan/rng.h>

#if defined(BOTAN_HAS_SYSTEM_RNG)

  #include <botan/system_rng.h>

#endif

#if defined(BOTAN_HAS_PROCESSOR_RNG)

  #include <botan/processor_rng.h>

#endif

#if defined(BOTAN_HAS_ENTROPY_SRC_RDSEED)

  #include <botan/internal/rdseed.h>

#endif

#if defined(BOTAN_HAS_ENTROPY_SRC_WIN32)

  #include <botan/internal/es_win32.h>

#endif

#if defined(BOTAN_HAS_ENTROPY_SRC_GETENTROPY)

  #include <botan/internal/getentropy.h>

#endif

namespace Botan {

namespace {

#if defined(BOTAN_HAS_SYSTEM_RNG)

class System_RNG_EntropySource final : public Entropy_Source

   {

   public:

      size_t poll(RandomNumberGenerator& rng) override

         {

         const size_t poll_bits = BOTAN_RNG_RESEED_POLL_BITS;

         rng.reseed_from_rng(system_rng(), poll_bits);

         return poll_bits;

         }

      std::string name() const override { return "system_rng"; }

   };

#endif

#if defined(BOTAN_HAS_PROCESSOR_RNG)

class Processor_RNG_EntropySource final : public Entropy_Source

   {

   public:

      size_t poll(RandomNumberGenerator& rng) override

         {

         /*

         * Intel's documentation for RDRAND at

         * https://software.intel.com/en-us/articles/intel-digital-random-number-generator-drng-software-implementation-guide

         * claims that software can guarantee a reseed event by polling enough data:

         * "There is an upper bound of 511 samples per seed in the implementation

         * where samples are 128 bits in size and can provide two 64-bit random

         * numbers each."

         *

         * By requesting 65536 bits we are asking for 512 samples and thus are assured

         * that at some point in producing the output, at least one reseed of the

         * internal state will occur.

         *

         * The reseeding conditions of the POWER and ARM processor RNGs are not known

         * but probably work in a somewhat similar manner. The exact amount requested

         * may be tweaked if and when such conditions become publically known.

         */

         const size_t poll_bits = 65536;

         rng.reseed_from_rng(m_hwrng, poll_bits);

         // Avoid trusting a black box, don't count this as contributing entropy:

         return 0;

         }

      std::string name() const override { return m_hwrng.name(); }

   private:

      Processor_RNG m_hwrng;

   };

#endif

}

std::unique_ptr<Entropy_Source> Entropy_Source::create(const std::string& name)

   {

#if defined(BOTAN_HAS_SYSTEM_RNG)

   if(name == "system_rng")

      {

      return std::make_unique<System_RNG_EntropySource>();

      }

#endif

#if defined(BOTAN_HAS_PROCESSOR_RNG)

   if(name == "hwrng")

      {

      if(Processor_RNG::available())

         {

         return std::make_unique<Processor_RNG_EntropySource>();

         }

      }

#endif

#if defined(BOTAN_HAS_ENTROPY_SRC_RDSEED)

   if(name == "rdseed")

      {

      return std::make_unique<Intel_Rdseed>();

      }

#endif

#if defined(BOTAN_HAS_ENTROPY_SRC_GETENTROPY)

   if(name == "getentropy")

      {

      return std::make_unique<Getentropy>();

      }

#endif

#if defined(BOTAN_HAS_ENTROPY_SRC_WIN32)

   if(name == "system_stats")

      {

      return std::make_unique<Win32_EntropySource>();

      }

#endif

   BOTAN_UNUSED(name);

   return nullptr;

   }

void Entropy_Sources::add_source(std::unique_ptr<Entropy_Source> src)

   {

   if(src.get())

      {

      m_srcs.push_back(std::move(src));

      }

   }

std::vector<std::string> Entropy_Sources::enabled_sources() const

   {

   std::vector<std::string> sources;

   for(size_t i = 0; i != m_srcs.size(); ++i)

      {

      sources.push_back(m_srcs[i]->name());

      }

   return sources;

   }

size_t Entropy_Sources::poll(RandomNumberGenerator& rng,

                             size_t poll_bits,

                             std::chrono::milliseconds timeout)

   {

   typedef std::chrono::system_clock clock;

   auto deadline = clock::now() + timeout;

   size_t bits_collected = 0;

   for(size_t i = 0; i != m_srcs.size(); ++i)

      {

      bits_collected += m_srcs[i]->poll(rng);

      if (bits_collected >= poll_bits || clock::now() > deadline)

         break;

      }

   return bits_collected;

   }

size_t Entropy_Sources::poll_just(RandomNumberGenerator& rng, const std::string& the_src)

   {

   for(size_t i = 0; i != m_srcs.size(); ++i)

      {

      if(m_srcs[i]->name() == the_src)

         {

         return m_srcs[i]->poll(rng);

         }

      }

   return 0;

   }

Entropy_Sources::Entropy_Sources(const std::vector<std::string>& sources)

   {

   for(auto&& src_name : sources)

      {

      add_source(Entropy_Source::create(src_name));

      }

   }

Entropy_Sources& Entropy_Sources::global_sources()

   {

   static Entropy_Sources global_entropy_sources(BOTAN_ENTROPY_DEFAULT_SOURCES);

   return global_entropy_sources;

   }

}