es_egd.cpp

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/*
* EGD EntropySource
* (C) 1999-2009 Jack Lloyd
*
* Distributed under the terms of the Botan license
*/
 
#include <botan/internal/es_egd.h>
#include <botan/parsing.h>
#include <botan/exceptn.h>
#include <cstring>
#include <stdexcept>
 
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
 
#include <sys/socket.h>
#include <sys/un.h>
 
#ifndef PF_LOCAL
  #define PF_LOCAL PF_UNIX
#endif
 
namespace Botan {
 
EGD_EntropySource::EGD_Socket::EGD_Socket(const std::string& path) :
   socket_path(path), m_fd(-1)
   {
   }
 
/**
* Attempt a connection to an EGD/PRNGD socket
*/
int EGD_EntropySource::EGD_Socket::open_socket(const std::string& path)
   {
   int fd = ::socket(PF_LOCAL, SOCK_STREAM, 0);
 
   if(fd >= 0)
      {
      sockaddr_un addr;
      std::memset(&addr, 0, sizeof(addr));
      addr.sun_family = PF_LOCAL;
 
      if(path.length() >= sizeof(addr.sun_path))
         throw std::invalid_argument("EGD socket path is too long");
 
      std::strncpy(addr.sun_path, path.c_str(), sizeof(addr.sun_path));
 
      int len = sizeof(addr.sun_family) + std::strlen(addr.sun_path) + 1;
 
      if(::connect(fd, reinterpret_cast<struct ::sockaddr*>(&addr), len) < 0)
         {
         ::close(fd);
         fd = -1;
         }
      }
 
   return fd;
   }
 
/**
* Attempt to read entropy from EGD
*/
size_t EGD_EntropySource::EGD_Socket::read(byte outbuf[], size_t length)
   {
   if(length == 0)
      return 0;
 
   if(m_fd < 0)
      {
      m_fd = open_socket(socket_path);
      if(m_fd < 0)
         return 0;
      }
 
   try
      {
      // 1 == EGD command for non-blocking read
      byte egd_read_command[2] = {
         1, static_cast<byte>(std::min<size_t>(length, 255)) };
 
      if(::write(m_fd, egd_read_command, 2) != 2)
         throw std::runtime_error("Writing entropy read command to EGD failed");
 
      byte out_len = 0;
      if(::read(m_fd, &out_len, 1) != 1)
         throw std::runtime_error("Reading response length from EGD failed");
 
      if(out_len > egd_read_command[1])
         throw std::runtime_error("Bogus length field received from EGD");
 
      ssize_t count = ::read(m_fd, outbuf, out_len);
 
      if(count != out_len)
         throw std::runtime_error("Reading entropy result from EGD failed");
 
      return static_cast<size_t>(count);
      }
   catch(std::exception)
      {
      this->close();
      // Will attempt to reopen next poll
      }
 
   return 0;
   }
 
void EGD_EntropySource::EGD_Socket::close()
   {
   if(m_fd > 0)
      {
      ::close(m_fd);
      m_fd = -1;
      }
   }
 
/**
* EGD_EntropySource constructor
*/
EGD_EntropySource::EGD_EntropySource(const std::vector<std::string>& paths)
   {
   for(size_t i = 0; i != paths.size(); ++i)
      sockets.push_back(EGD_Socket(paths[i]));
   }
 
EGD_EntropySource::~EGD_EntropySource()
   {
   for(size_t i = 0; i != sockets.size(); ++i)
      sockets[i].close();
   sockets.clear();
   }
 
/**
* Gather Entropy from EGD
*/
void EGD_EntropySource::poll(Entropy_Accumulator& accum)
   {
   size_t go_get = std::min<size_t>(accum.desired_remaining_bits() / 8, 32);
 
   MemoryRegion<byte>& io_buffer = accum.get_io_buffer(go_get);
 
   for(size_t i = 0; i != sockets.size(); ++i)
      {
      size_t got = sockets[i].read(&io_buffer[0], io_buffer.size());
 
      if(got)
         {
         accum.add(&io_buffer[0], got, 6);
         break;
         }
      }
   }
 
}