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/*
* Reader of /dev/random and company
* (C) 1999-2009,2013 Jack Lloyd
*
* Distributed under the terms of the Botan license
*/
#include <botan/internal/dev_random.h>
#include <sys/types.h>
#include <sys/select.h>
#include <sys/stat.h>
#include <unistd.h>
#include <fcntl.h>
#include <string.h>
namespace Botan {
namespace {
int open_nonblocking(const char* pathname)
{
#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;
return ::open(pathname, flags);
}
}
/**
Device_EntropySource constructor
Open a file descriptor to each (available) device in fsnames
*/
Device_EntropySource::Device_EntropySource(const std::vector<std::string>& fsnames)
{
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 destructor: close all open devices
*/
Device_EntropySource::~Device_EntropySource()
{
for(size_t i = 0; i != devices.size(); ++i)
::close(devices[i]);
}
/**
* Gather entropy from a RNG device
*/
void Device_EntropySource::poll(Entropy_Accumulator& accum)
{
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;
secure_vector<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());
accum.add(&io_buffer[0], got, ENTROPY_BITS_PER_BYTE);
}
}
}
}
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