/* rndegd.c  -	interface to the EGD
 *	Copyright (C) 1999-2012 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>

#ifndef _WIN32

#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <sys/time.h>
#include <sys/stat.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/un.h>
#include "egd.h"
#include <gnutls_int.h>
#include <gnutls_str.h>
#include <gnutls_errors.h>

#ifdef AF_UNIX
# define LOCAL_SOCKET_TYPE AF_UNIX
#else
# define LOCAL_SOCKET_TYPE AF_LOCAL
#endif

#ifndef offsetof
#define offsetof(type, member) ((size_t) &((type *)0)->member)
#endif

static int egd_socket = -1;

static int
do_write (int fd, void *buf, size_t nbytes)
{
  size_t nleft = nbytes;
  int nwritten;

  while (nleft > 0)
    {
      nwritten = write (fd, buf, nleft);
      if (nwritten < 0)
        {
          if (errno == EINTR)
            continue;
          return -1;
        }
      nleft -= nwritten;
      buf = (char *) buf + nwritten;
    }
  return 0;
}

static int
do_read (int fd, void *buf, size_t nbytes)
{
  int n;
  size_t nread = 0;

  do
    {
      do
        {
          n = read (fd, (char *) buf + nread, nbytes);
        }
      while (n == -1 && errno == EINTR);
      if (n == -1)
        {
          if (nread > 0)
            return nread;
          else return -1;
        }
      if (n == 0)
        return -1;
      nread += n;
      nbytes -= n;
    }
  while (nread < nbytes);
  return nread;
}

static const char *egd_names[] = {
  "/var/run/egd-pool",
  "/dev/egd-pool",
  "/etc/egd-pool",
  "/etc/entropy",
  "/var/run/entropy",
  "/dev/entropy",
  NULL
};

static const char *
find_egd_name (void)
{
  int i = 0;
  struct stat st;

  do
    {
      if (stat (egd_names[i], &st) != 0)
        continue;

      if (st.st_mode & S_IFSOCK)
        {                       /* found */
          return egd_names[i];
        }

    }
  while (egd_names[++i] != NULL);

  return NULL;
}

/* Connect to the EGD and return the file descriptor.  Return -1 on
   error.  With NOFAIL set to true, silently fail and return the
   error, otherwise print an error message and die. */
int
_rndegd_connect_socket (void)
{
  int fd;
  const char *name;
  struct sockaddr_un addr;
  int addr_len;

  if (egd_socket != -1)
    {
      close (egd_socket);
      egd_socket = -1;
    }

  name = find_egd_name ();
  if (name == NULL)
    {
      _gnutls_debug_log ("Could not detect an egd device.\n");
      return -1;
    }

  if (strlen (name) + 1 >= sizeof addr.sun_path)
    {
      _gnutls_debug_log ("EGD socketname is too long\n");
      return -1;
    }

  memset (&addr, 0, sizeof addr);
  addr.sun_family = LOCAL_SOCKET_TYPE;
  _gnutls_str_cpy (addr.sun_path, sizeof(addr.sun_path), name);
  addr_len = (offsetof (struct sockaddr_un, sun_path)
              + strlen (addr.sun_path));

  fd = socket (LOCAL_SOCKET_TYPE, SOCK_STREAM, 0);
  if (fd == -1)
    {
      _gnutls_debug_log ("can't create unix domain socket: %s\n",
                         strerror (errno));
      return -1;
    }
  else if (connect (fd, (struct sockaddr *) &addr, addr_len) == -1)
    {
      _gnutls_debug_log ("can't connect to EGD socket `%s': %s\n",
                         name, strerror (errno));
      close (fd);
      fd = -1;
    }

  if (fd != -1)
    egd_socket = fd;
  return fd;
}

/****************
 * Note: We always use the highest level.
 * To boost the performance we may want to add some
 * additional code for level 1
 *
 * Using a level of 0 should never block and better add nothing
 * to the pool.  So this is just a dummy for EGD.
 */
int
_rndegd_read (int *fd, void *_output, size_t _length)
{
  ssize_t n;
  uint8_t buffer[256 + 2];
  int nbytes;
  int do_restart = 0;
  unsigned char *output = _output;
  ssize_t length = (ssize_t)_length;

  if (!length)
    return 0;

restart:
  if (*fd == -1 || do_restart)
    *fd = _rndegd_connect_socket ();

  do_restart = 0;

  nbytes = length < 255 ? length : 255;
  /* First time we do it with a non blocking request */
  buffer[0] = 1;                /* non blocking */
  buffer[1] = nbytes;

  if (do_write (*fd, buffer, 2) == -1)
    _gnutls_debug_log ("can't write to the EGD: %s\n", strerror (errno));

  n = do_read (*fd, buffer, 1);
  if (n == -1)
    {
      _gnutls_debug_log ("read error on EGD: %s\n", strerror (errno));
      do_restart = 1;
      goto restart;
    }

  n = buffer[0];
  if (n)
    {
      n = do_read (*fd, buffer, n);
      if (n == -1)
        {
          _gnutls_debug_log ("read error on EGD: %s\n", strerror (errno));
          do_restart = 1;
          goto restart;
        }

      if (n > length)
        {
          _gnutls_debug_log ("read error on EGD: returned more bytes!\n");
          n = length;
        }

      memcpy (output, buffer, n);
      output += n;
      length -= n;
    }

  while (length)
    {
      nbytes = length < 255 ? length : 255;

      buffer[0] = 2;            /* blocking */
      buffer[1] = nbytes;
      if (do_write (*fd, buffer, 2) == -1)
        _gnutls_debug_log ("can't write to the EGD: %s\n", strerror (errno));
      n = do_read (*fd, buffer, nbytes);
      if (n == -1)
        {
          _gnutls_debug_log ("read error on EGD: %s\n", strerror (errno));
          do_restart = 1;
          goto restart;
        }

      if (n > length)
        {
          _gnutls_debug_log ("read error on EGD: returned more bytes!\n");
          n = length;
        }

      memcpy (output, buffer, n);
      output += n;
      length -= n;
    }

  return _length;               /* success */
}

#endif