Botan::Intel_Rdseed Class Reference

#include <rdseed.h>

Inheritance diagram for Botan::Intel_Rdseed:

Public Member Functions
std::string	name () const override
size_t	poll (RandomNumberGenerator &rng) override

Static Public Member Functions
static std::unique_ptr< Entropy_Source >	create (std::string_view type)

Detailed Description

Entropy source using the rdseed instruction first introduced on Intel's Broadwell architecture.

Definition at line 19 of file rdseed.h.

Member Function Documentation

create()

std::unique_ptr< Entropy_Source > Botan::Entropy_Source::create ( std::string_view type )

staticinherited

Return a new entropy source of a particular type, or null Each entropy source may require substantial resources (eg, a file handle or socket instance), so try to share them among multiple RNGs, or just use the preconfigured global list accessed by Entropy_Sources::global_sources()

Definition at line 111 of file entropy_srcs.cpp.

                                                                        {
#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
 
#if defined(BOTAN_HAS_JITTER_RNG)
   if(name == "jitter_rng") {
      return std::make_unique<Jitter_RNG_EntropySource>();
   }
#endif
 
   BOTAN_UNUSED(name);
   return nullptr;
}

References Botan::Processor_RNG::available(), BOTAN_UNUSED, and name().

Referenced by Botan::Entropy_Sources::Entropy_Sources().

name()

std::string Botan::Intel_Rdseed::name ( ) const

inlineoverridevirtual

Returns

name identifying this entropy source

Implements Botan::Entropy_Source.

Definition at line 21 of file rdseed.h.

{ return "rdseed"; }

poll()

size_t Botan::Intel_Rdseed::poll ( RandomNumberGenerator & rng )

overridevirtual

Perform an entropy gathering poll

Parameters

rng	will be provided with entropy via calls to add_entropy

Returns

conservative estimate of actual entropy added to rng during poll

Implements Botan::Entropy_Source.

Definition at line 67 of file rdseed.cpp.

                                                    {
   const size_t RDSEED_BYTES = 1024;
   static_assert(RDSEED_BYTES % 4 == 0, "Bad RDSEED configuration");
 
   if(CPUID::has(CPUID::Feature::RDSEED)) {
      secure_vector<uint32_t> seed;
      seed.reserve(RDSEED_BYTES / 4);
 
      for(size_t p = 0; p != RDSEED_BYTES / 4; ++p) {
         /*
         If at any point we exceed our retry count, we stop the entire seed
         gathering process. This situation will only occur in situations of
         extremely high RDSEED utilization. If RDSEED is currently so highly
         contended, then the rest of the poll is likely to also face contention and
         it is better to quit now rather than (presumably) face very high retry
         times for the rest of the poll.
         */
         if(!read_rdseed(seed)) {
            break;
         }
      }
 
      if(!seed.empty()) {
         rng.add_entropy(reinterpret_cast<const uint8_t*>(seed.data()), seed.size() * sizeof(uint32_t));
      }
   }
 
   // RDSEED is used but not trusted
   return 0;
}

References Botan::RandomNumberGenerator::add_entropy(), Botan::CPUID::has(), and Botan::CPUFeature::RDSEED.

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The documentation for this class was generated from the following files:

• src/lib/entropy/rdseed/rdseed.h
• src/lib/entropy/rdseed/rdseed.cpp