/* rndegd.c  -	interface to the EGD
 *	Copyright (C) 1999, 2000, 2002, 2003 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 <https://www.gnu.org/licenses/>.
 * SPDX-License-Identifier: LGPL-2.1-or-later
 */

#include <config.h>
#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 "types.h"
#include "g10lib.h"
#include "cipher.h"
#include "rand-internal.h"

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

static int egd_socket = -1;

/* Allocated name of the socket if supplied at runtime.  */
static char *user_socket_name;


/* Allocate a new filename from FIRST_PART and SECOND_PART and to
   tilde expansion for first_part.  SECOND_PART might be NULL.
 */
static char *
my_make_filename (const char *first_part, const char *second_part)
{
  size_t n;
  char *name, *home, *p;

  n = strlen(first_part)+1;
  if (second_part)
    n += strlen (second_part) + 1;

  home = NULL;
  if( *first_part == '~' && first_part[1] == '/'
      && (home = getenv("HOME")) && *home )
    n += strlen(home);

  name = _gcry_xmalloc(n);
  p = (home
       ? stpcpy (stpcpy (name, home), first_part+1 )
       : stpcpy (name, first_part) );

  if (second_part)
    strcpy (stpcpy(p,"/"), second_part);

  return name;
}


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, nread = 0;

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


/* Note that his function is not thread-safe.  */
gpg_error_t
_gcry_rndegd_set_socket_name (const char *name)
{
  char *newname;
  struct sockaddr_un addr;

  newname = my_make_filename (name, NULL);
  if (strlen (newname)+1 >= sizeof addr.sun_path)
    {
      xfree (newname);
      return gpg_error_from_syserror ();
    }
  xfree (user_socket_name);
  user_socket_name = newname;
  return 0;
}


/* 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
_gcry_rndegd_connect_socket (int nofail)
{
  int fd;
  const char *bname = NULL;
  char *name;
  struct sockaddr_un addr;
  int addr_len;

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

#ifdef EGD_SOCKET_NAME
  bname = EGD_SOCKET_NAME;
#endif
  if (user_socket_name)
    {
      name = _gcry_strdup (user_socket_name);
      if (!name)
        {
          if (!nofail)
            log_fatal ("error allocating memory in rndegd: %s\n",
                       strerror(errno) );
          return -1;
        }
    }
  else if ( !bname || !*bname )
    name = my_make_filename ("~/.gnupg", "entropy");
  else
    name = my_make_filename (bname, NULL);

  if (strlen(name)+1 >= sizeof addr.sun_path)
    log_fatal ("EGD socketname is too long\n");

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

  fd = socket(AF_UNIX, SOCK_STREAM, 0);
  if (fd == -1 && !nofail)
    log_fatal("can't create unix domain socket: %s\n", strerror(errno) );
  else if (connect (fd, (struct sockaddr*)&addr, addr_len) == -1)
    {
      if (!nofail)
        log_fatal("can't connect to EGD socket `%s': %s\n",
		  name, strerror(errno) );
      close (fd);
      fd = -1;
    }
  xfree (name);
  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
_gcry_rndegd_gather_random (void (*add)(const void*, size_t,
                                        enum random_origins),
                            enum random_origins origin,
                            size_t length, int level )
{
  int fd = egd_socket;
  int n;
  byte buffer[256+2];
  int nbytes;
  int do_restart = 0;

  if( !length )
    return 0;
  if( !level )
    return 0;

 restart:
  if (fd == -1 || do_restart)
    fd = _gcry_rndegd_connect_socket (0);

  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 )
    log_fatal("can't write to the EGD: %s\n", strerror(errno) );
  n = do_read( fd, buffer, 1 );
  if( n == -1 )
    {
      log_error("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 )
        {
          log_error("read error on EGD: %s\n", strerror(errno));
          do_restart = 1;
          goto restart;
	}
      (*add)( buffer, n, origin );
      length -= n;
    }

  if( length )
    {
      log_info (
      _("Please wait, entropy is being gathered. Do some work if it would\n"
        "keep you from getting bored, because it will improve the quality\n"
        "of the entropy.\n") );
    }
  while( length )
    {
      nbytes = length < 255? length : 255;

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

  return 0; /* success */
}