/* rndlinux.c  -  raw random number for OSes with /dev/random
 * Copyright (C) 1998, 2001, 2002, 2003, 2007,
 *               2009  Free Software Foundation, Inc.
 *
 * This file is part of Libgcrypt.
 *
 * Libgcrypt is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation; either version 2.1 of
 * the License, or (at your option) any later version.
 *
 * Libgcrypt is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this program; if not, see <http://www.gnu.org/licenses/>.
 */


#include <config.h>
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <sys/time.h>
#include <sys/types.h>
#include <sys/stat.h>
#ifdef HAVE_GETTIMEOFDAY
# include <sys/times.h>
#endif
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include "types.h"
#include "g10lib.h"
#include "rand-internal.h"

static int open_device ( const char *name );


static int
set_cloexec_flag (int fd)
{
  int oldflags;

  oldflags= fcntl (fd, F_GETFD, 0);
  if (oldflags < 0)
    return oldflags;
  oldflags |= FD_CLOEXEC;
  return fcntl (fd, F_SETFD, oldflags);
}



/*
 * Used to open the /dev/random devices (Linux, xBSD, Solaris (if it exists)).
 */
static int
open_device ( const char *name )
{
  int fd;

  fd = open ( name, O_RDONLY );
  if ( fd == -1 )
    log_fatal ("can't open %s: %s\n", name, strerror(errno) );

  if (set_cloexec_flag (fd))
    log_error ("error setting FD_CLOEXEC on fd %d: %s\n",
               fd, strerror (errno));

  /* We used to do the following check, however it turned out that this
     is not portable since more OSes provide a random device which is
     sometimes implemented as another device type.

     struct stat sb;

     if( fstat( fd, &sb ) )
        log_fatal("stat() off %s failed: %s\n", name, strerror(errno) );
     if( (!S_ISCHR(sb.st_mode)) && (!S_ISFIFO(sb.st_mode)) )
        log_fatal("invalid random device!\n" );
  */
  return fd;
}


int
_gcry_rndlinux_gather_random (void (*add)(const void*, size_t,
                                          enum random_origins),
                              enum random_origins origin,
                              size_t length, int level )
{
  static int fd_urandom = -1;
  static int fd_random = -1;
  int fd;
  int n;
  byte buffer[768];
  size_t n_hw;
  size_t want = length;
  size_t last_so_far = 0;
  int any_need_entropy = 0;
  int delay;

  /* First read from a hardware source.  However let it account only
     for up to 50% of the requested bytes.  */
  n_hw = _gcry_rndhw_poll_slow (add, origin);
  if (n_hw > length/2)
    n_hw = length/2;
  if (length > 1)
    length -= n_hw;

  /* Open the requested device.  */
  if (level >= 2)
    {
      if( fd_random == -1 )
        fd_random = open_device ( NAME_OF_DEV_RANDOM );
      fd = fd_random;
    }
  else
    {
      if( fd_urandom == -1 )
        fd_urandom = open_device ( NAME_OF_DEV_URANDOM );
      fd = fd_urandom;
    }

  /* Enter the read loop.  */
  delay = 0;  /* Start with 0 seconds so that we do no block on the
                 first iteration and in turn call the progress function
                 before blocking.  To give the OS a better chance to
                 return with something we will actually use 100ms. */
  while (length)
    {
      fd_set rfds;
      struct timeval tv;
      int rc;

      /* If the system has no limit on the number of file descriptors
         and we encounter an fd which is larger than the fd_set size,
         we don't use the select at all.  The select code is only used
         to emit progress messages.  A better solution would be to
         fall back to poll() if available.  */
#ifdef FD_SETSIZE
      if (fd < FD_SETSIZE)
#endif
        {
          FD_ZERO(&rfds);
          FD_SET(fd, &rfds);
          tv.tv_sec = delay;
          tv.tv_usec = delay? 0 : 100000;
          if ( !(rc=select(fd+1, &rfds, NULL, NULL, &tv)) )
            {
              if (!any_need_entropy || last_so_far != (want - length) )
                {
                  last_so_far = want - length;
                  _gcry_random_progress ("need_entropy", 'X',
                                         (int)last_so_far, (int)want);
                  any_need_entropy = 1;
                }
              delay = 3; /* Use 3 seconds henceforth.  */
              continue;
            }
          else if( rc == -1 )
            {
              log_error ("select() error: %s\n", strerror(errno));
              if (!delay)
                delay = 1; /* Use 1 second if we encounter an error before
                          we have ever blocked.  */
              continue;
            }
        }

      do
        {
          int nbytes = length < sizeof(buffer)? length : sizeof(buffer);
          n = read(fd, buffer, nbytes );
          if( n >= 0 && n > nbytes )
            {
              log_error("bogus read from random device (n=%d)\n", n );
              n = nbytes;
            }
        }
      while( n == -1 && errno == EINTR );
      if ( n == -1 )
        log_fatal("read error on random device: %s\n", strerror(errno));
      (*add)( buffer, n, origin );
      length -= n;
    }
  memset(buffer, 0, sizeof(buffer) );

  if (any_need_entropy)
    _gcry_random_progress ("need_entropy", 'X', (int)want, (int)want);

  return 0; /* success */
}