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/*************************************************
* Device EntropySource Source File *
* (C) 1999-2008 Jack Lloyd *
*************************************************/
#include <botan/es_dev.h>
#include <sys/select.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/fcntl.h>
#include <unistd.h>
namespace Botan {
namespace {
/*************************************************
* A class handling reading from a device *
*************************************************/
class Device_Reader
{
public:
typedef int fd_type;
Device_Reader(fd_type device_fd) : fd(device_fd) {}
~Device_Reader() { if(fd > 0) { ::close(fd); } }
u32bit get(byte out[], u32bit length);
static fd_type open(const std::string& pathname);
private:
fd_type fd;
};
/*************************************************
* Read from a device file *
*************************************************/
u32bit Device_Reader::get(byte out[], u32bit length)
{
if(fd < 0)
return 0;
if(fd >= FD_SETSIZE)
return 0;
const u32bit READ_WAIT_MS = 10;
fd_set read_set;
FD_ZERO(&read_set);
FD_SET(fd, &read_set);
struct ::timeval timeout;
timeout.tv_sec = 0;
timeout.tv_usec = READ_WAIT_MS * 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;
const u32bit ret = static_cast<u32bit>(got);
if(ret > length)
return 0;
return ret;
}
/*************************************************
* Attempt to open a device *
*************************************************/
int 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);
}
}
/**
* Gather entropy from a RNG device
*/
u32bit Device_EntropySource::slow_poll(byte output[], u32bit length)
{
u32bit read = 0;
for(size_t j = 0; j != fsnames.size(); ++j)
{
Device_Reader reader(Device_Reader::open(fsnames[j]));
read += reader.get(output + read, length - read);
if(read == length)
break;
}
return read;
}
/**
* Fast /dev/random and co poll: limit output to 64 bytes
*/
u32bit Device_EntropySource::fast_poll(byte output[], u32bit length)
{
return slow_poll(output, std::max<u32bit>(length, 64));
}
}
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