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/*
* Reader of /dev/random and company
* (C) 1999-2009,2013 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
#include <botan/internal/dev_random.h>
#include <botan/exceptn.h>
#include <sys/types.h>
#include <sys/select.h>
#include <sys/stat.h>
#include <unistd.h>
#include <errno.h>
#include <fcntl.h>
namespace Botan {
/**
Device_EntropySource constructor
Open a file descriptor to each (available) device in fsnames
*/
Device_EntropySource::Device_EntropySource(const std::vector<std::string>& fsnames)
{
#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;
m_max_fd = 0;
for(auto fsname : fsnames)
{
int fd = ::open(fsname.c_str(), flags);
if(fd < 0)
{
/*
ENOENT or EACCES is normal as some of the named devices may not exist
on this system. But any other errno value probably indicates
either a bug in the application or file descriptor exhaustion.
*/
if(errno != ENOENT && errno != EACCES)
throw Exception("Opening OS RNG device failed with errno " +
std::to_string(errno));
}
else
{
if(fd > FD_SETSIZE)
{
::close(fd);
throw Exception("Open of OS RNG succeeded but fd is too large for fd_set");
}
m_dev_fds.push_back(fd);
m_max_fd = std::max(m_max_fd, fd);
}
}
}
/**
Device_EntropySource destructor: close all open devices
*/
Device_EntropySource::~Device_EntropySource()
{
for(int fd : m_dev_fds)
{
// ignoring return value here, can't throw in destructor anyway
::close(fd);
}
}
/**
* Gather entropy from a RNG device
*/
size_t Device_EntropySource::poll(RandomNumberGenerator& rng)
{
size_t bits = 0;
if(m_dev_fds.size() > 0)
{
fd_set read_set;
FD_ZERO(&read_set);
for(int dev_fd : m_dev_fds)
{
FD_SET(dev_fd, &read_set);
}
secure_vector<uint8_t> io_buf(BOTAN_SYSTEM_RNG_POLL_REQUEST);
struct ::timeval timeout;
timeout.tv_sec = (BOTAN_SYSTEM_RNG_POLL_TIMEOUT_MS / 1000);
timeout.tv_usec = (BOTAN_SYSTEM_RNG_POLL_TIMEOUT_MS % 1000) * 1000;
if(::select(m_max_fd + 1, &read_set, nullptr, nullptr, &timeout) > 0)
{
for(int dev_fd : m_dev_fds)
{
if(FD_ISSET(dev_fd, &read_set))
{
const ssize_t got = ::read(dev_fd, io_buf.data(), io_buf.size());
if(got > 0)
{
rng.add_entropy(io_buf.data(), static_cast<size_t>(got));
bits += got * 8;
}
}
}
}
}
return bits;
}
}
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