Botan::Device_EntropySource Class Reference

#include <dev_random.h>

Inheritance diagram for Botan::Device_EntropySource:

List of all members.

Public Member Functions
	Device_EntropySource (const std::vector< std::string > &fsnames)
std::string	name () const
void	poll (Entropy_Accumulator &accum)
	~Device_EntropySource ()
Static Public Member Functions
static void	poll_available_sources (class Entropy_Accumulator &accum)

---

Detailed Description

Entropy source reading from kernel devices like /dev/random

Definition at line 20 of file dev_random.h.

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Constructor & Destructor Documentation

Botan::Device_EntropySource::Device_EntropySource

(

const std::vector< std::string > &

fsnames

)

Device_EntropySource constructor Open a file descriptor to each (available) device in fsnames

Definition at line 23 of file dev_random.cpp.

References O_NOCTTY, and O_NONBLOCK.

   {
#ifndef O_NONBLOCK
  #define O_NONBLOCK 0
#endif

#ifndef O_NOCTTY
  #define O_NOCTTY 0
#endif

   const int flags = O_RDONLY | O_NONBLOCK | O_NOCTTY;

   for(auto fsname : fsnames)
      {
      fd_type fd = ::open(fsname.c_str(), flags);

      if(fd >= 0 && fd < FD_SETSIZE)
         m_devices.push_back(fd);
      else if(fd >= 0)
         ::close(fd);
      }
   }

Botan::Device_EntropySource::~Device_EntropySource

(

)

Device_EntropySource destructor: close all open devices

Definition at line 49 of file dev_random.cpp.

   {
   for(size_t i = 0; i != m_devices.size(); ++i)
      ::close(m_devices[i]);
   }

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Member Function Documentation

std::string Botan::Device_EntropySource::name

(

)

const [inline, virtual]

Returns:

name identifying this entropy source

Implements Botan::EntropySource.

Definition at line 23 of file dev_random.h.

{ return "RNG Device Reader"; }

void Botan::Device_EntropySource::poll

(

Entropy_Accumulator &

accum

)

[virtual]

Gather entropy from a RNG device

Implements Botan::EntropySource.

Definition at line 58 of file dev_random.cpp.

References Botan::Entropy_Accumulator::add(), and Botan::Entropy_Accumulator::get_io_buffer().

   {
   if(m_devices.empty())
      return;

   const size_t ENTROPY_BITS_PER_BYTE = 8;
   const size_t MS_WAIT_TIME = 32;
   const size_t READ_ATTEMPT = 32;

   int max_fd = m_devices[0];
   fd_set read_set;
   FD_ZERO(&read_set);
   for(size_t i = 0; i != m_devices.size(); ++i)
      {
      FD_SET(m_devices[i], &read_set);
      max_fd = std::max(m_devices[i], max_fd);
      }

   struct ::timeval timeout;

   timeout.tv_sec = (MS_WAIT_TIME / 1000);
   timeout.tv_usec = (MS_WAIT_TIME % 1000) * 1000;

   if(::select(max_fd + 1, &read_set, nullptr, nullptr, &timeout) < 0)
      return;

   secure_vector<byte>& io_buffer = accum.get_io_buffer(READ_ATTEMPT);

   for(size_t i = 0; i != m_devices.size(); ++i)
      {
      if(FD_ISSET(m_devices[i], &read_set))
         {
         const ssize_t got = ::read(m_devices[i], &io_buffer[0], io_buffer.size());
         if(got > 0)
            accum.add(&io_buffer[0], got, ENTROPY_BITS_PER_BYTE);
         }
      }
   }

void Botan::EntropySource::poll_available_sources

(

class Entropy_Accumulator &

accum

)

[static, inherited]

Definition at line 108 of file entropy_srcs.cpp.

References Botan::Entropy_Accumulator::polling_goal_achieved().

Referenced by Botan::HMAC_RNG::reseed().

   {
   static std::vector<std::unique_ptr<EntropySource>> g_sources(get_default_entropy_sources());

   if(g_sources.empty())
      throw std::runtime_error("No entropy sources enabled at build time, poll failed");

   size_t poll_attempt = 0;

   while(!accum.polling_goal_achieved() && poll_attempt < 16)
      {
      const size_t src_idx = poll_attempt % g_sources.size();
      g_sources[src_idx]->poll(accum);
      ++poll_attempt;
      }
   }

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

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