Botan::Device_EntropySource Class Reference

#include <dev_random.h>

Inheritance diagram for Botan::Device_EntropySource:

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

Detailed Description

Entropy source reading from kernel devices like /dev/random

Definition at line 20 of file dev_random.h.

Constructor & Destructor Documentation

Device_EntropySource()

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 41 of file dev_random.cpp.

   {
   for(size_t i = 0; i != fsnames.size(); ++i)
      {
      fd_type fd = open_nonblocking(fsnames[i].c_str());
      if(fd >= 0 && fd < FD_SETSIZE)
         devices.push_back(fd);
      }
   }

~Device_EntropySource()

Botan::Device_EntropySource::~Device_EntropySource

(

)

Device_EntropySource destructor: close all open devices

Definition at line 54 of file dev_random.cpp.

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

Member Function Documentation

name()

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

inlinevirtual

Returns

name identifying this entropy source

Implements Botan::EntropySource.

Definition at line 23 of file dev_random.h.

{ return "RNG Device Reader"; }

poll()

void Botan::Device_EntropySource::poll ( Entropy_Accumulator & accum )

virtual

Gather entropy from a RNG device

Implements Botan::EntropySource.

Definition at line 63 of file dev_random.cpp.

   {
   if(devices.empty())
      return;
 
   const size_t ENTROPY_BITS_PER_BYTE = 8;
   const size_t MS_WAIT_TIME = 32;
   const size_t READ_ATTEMPT = accum.desired_remaining_bits() / 4;
 
   MemoryRegion<byte>& io_buffer = accum.get_io_buffer(READ_ATTEMPT);
 
   int max_fd = devices[0];
   fd_set read_set;
   FD_ZERO(&read_set);
   for(size_t i = 0; i != devices.size(); ++i)
      {
      FD_SET(devices[i], &read_set);
      max_fd = std::max(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, 0, 0, &timeout) < 0)
      return;
 
   for(size_t i = 0; i != devices.size(); ++i)
      {
      if(FD_ISSET(devices[i], &read_set))
         {
         const ssize_t got = ::read(devices[i], &io_buffer[0], io_buffer.size());
         if(got > 0)
            accum.add(&io_buffer[0], got, ENTROPY_BITS_PER_BYTE);
         }
      }
   }

References Botan::Entropy_Accumulator::add(), Botan::Entropy_Accumulator::desired_remaining_bits(), Botan::Entropy_Accumulator::get_io_buffer(), and Botan::MemoryRegion< T >::size().

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

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