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/*
* /dev/random EntropySource
* (C) 1999-2009 Jack Lloyd
*
* Distributed under the terms of the Botan license
*/
#include <botan/es_dev.h>
#include <sys/types.h>
#include <sys/select.h>
#include <sys/stat.h>
#include <unistd.h>
#include <fcntl.h>
namespace Botan {
/**
Close the device, if open
*/
void Device_EntropySource::Device_Reader::close()
{
if(fd > 0) { ::close(fd); fd = -1; }
}
/**
Read bytes from a device file
*/
u32bit Device_EntropySource::Device_Reader::get(byte out[], u32bit length,
u32bit ms_wait_time)
{
if(fd < 0)
return 0;
if(fd >= FD_SETSIZE)
return 0;
fd_set read_set;
FD_ZERO(&read_set);
FD_SET(fd, &read_set);
struct ::timeval timeout;
timeout.tv_sec = 0;
timeout.tv_usec = ms_wait_time * 1000;
if(::select(fd + 1, &read_set, 0, 0, &timeout) < 0)
return 0;
if(!(FD_ISSET(fd, &read_set)))
return 0;
const ssize_t got = ::read(fd, out, length);
if(got <= 0)
return 0;
return static_cast<u32bit>(got);
}
/**
Attempt to open a device
*/
Device_EntropySource::Device_Reader::fd_type
Device_EntropySource::Device_Reader::open(const std::string& 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.c_str(), 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(u32bit i = 0; i != fsnames.size(); ++i)
{
Device_Reader::fd_type fd = Device_Reader::open(fsnames[i]);
if(fd > 0)
devices.push_back(Device_Reader(fd));
}
}
/**
Device_EntropySource destructor: close all open devices
*/
Device_EntropySource::~Device_EntropySource()
{
for(size_t i = 0; i != devices.size(); ++i)
devices[i].close();
}
/**
* Gather entropy from a RNG device
*/
void Device_EntropySource::poll(Entropy_Accumulator& accum)
{
u32bit go_get = std::min<u32bit>(accum.desired_remaining_bits() / 8, 48);
u32bit read_wait_ms = std::max<u32bit>(go_get, 1000);
MemoryRegion<byte>& io_buffer = accum.get_io_buffer(go_get);
for(size_t i = 0; i != devices.size(); ++i)
{
u32bit got = devices[i].get(io_buffer.begin(), io_buffer.size(),
read_wait_ms);
if(got)
{
accum.add(io_buffer.begin(), got, 8);
break;
}
}
}
}
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