gnupg/cipher/rndlinux.c

/* rndlinux.c  -  raw random number for OSes with /dev/random
 *	Copyright (C) 1998, 1999, 2000, 2001 Free Software Foundation, Inc.
 *
 * This file is part of GnuPG.
 *
 * GnuPG is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * GnuPG 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
 */


#include <config.h>
#include <stdio.h>
#include <stdlib.h>
#include <assert.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>
#if 0
  #ifdef HAVE_LINUX_RANDOM_H
    #include <sys/ioctl.h>
    #include <asm/types.h>
    #include <linux/random.h>
  #endif
#endif
#include "types.h"
#include "util.h"
#include "ttyio.h"
#include "dynload.h"

#ifdef IS_MODULE
  #define _(a) (a)
#else
  #include "i18n.h"
#endif

static int open_device( const char *name, int minor );
static int gather_random( void (*add)(const void*, size_t, int), int requester,
					  size_t length, int level );

#if 0
#ifdef HAVE_DEV_RANDOM_IOCTL
static ulong
get_entropy_count( int fd )
{
    ulong count;

    if( ioctl( fd, RNDGETENTCNT, &count ) == -1 )
	g10_log_fatal("ioctl(RNDGETENTCNT) failed: %s\n", strerror(errno) );
    return count;
}
#endif
#endif

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

    fd = open( name, O_RDONLY );
    if( fd == -1 )
	g10_log_fatal("can't open %s: %s\n", name, strerror(errno) );
    if( fstat( fd, &sb ) )
	g10_log_fatal("stat() off %s failed: %s\n", name, strerror(errno) );
    /* Don't check device type for better portability */
    /*  if( (!S_ISCHR(sb.st_mode)) && (!S_ISFIFO(sb.st_mode)) )
	  g10_log_fatal("invalid random device!\n" ); */
    return fd;
}


/****************
 * Note:  Using a level of 0 should never block and better add nothing
 * to the pool.  This is easy to accomplish with /dev/urandom.
 */
static int
gather_random( void (*add)(const void*, size_t, int), int requester,
					  size_t length, int level )
{
    static int fd_urandom = -1;
    static int fd_random = -1;
    int fd;
    int n;
    int warn=0;
    byte buffer[768];

    if( level >= 2 ) {
	if( fd_random == -1 )
	    fd_random = open_device( NAME_OF_DEV_RANDOM, 8 );
	fd = fd_random;
    }
    else {
	/* this will also be used for elve 0 but by using /dev/urandom
	 * we can be sure that oit will never block. */
	if( fd_urandom == -1 )
	    fd_urandom = open_device( NAME_OF_DEV_URANDOM, 9 );
	fd = fd_urandom;
    }

  #if 0
  #ifdef HAVE_DEV_RANDOM_IOCTL
    g10_log_info("entropy count of %d is %lu\n", fd, get_entropy_count(fd) );
  #endif
  #endif
    while( length ) {
	fd_set rfds;
	struct timeval tv;
	int rc;

	FD_ZERO(&rfds);
	FD_SET(fd, &rfds);
	tv.tv_sec = 3;
	tv.tv_usec = 0;
	if( !(rc=select(fd+1, &rfds, NULL, NULL, &tv)) ) {
	    if( !warn )
	      #ifdef IS_MODULE
		fprintf(stderr,
	      #else
		tty_printf(
	      #endif
_("\n"
"Not enough random bytes available.  Please do some other work to give\n"
"the OS a chance to collect more entropy! (Need %d more bytes)\n"), (int)length );
	    warn = 1;
	    continue;
	}
	else if( rc == -1 ) {
	  #ifdef IS_MODULE
	    fprintf(stderr,
	  #else
	    tty_printf(
	  #endif
		       "select() error: %s\n", strerror(errno));
	    continue;
	}

	do {
	    int nbytes = length < sizeof(buffer)? length : sizeof(buffer);
	    n = read(fd, buffer, nbytes );
	    if( n >= 0 && n > nbytes ) {
		g10_log_error("bogus read from random device (n=%d)\n", n );
		n = nbytes;
	    }
	} while( n == -1 && errno == EINTR );
	if( n == -1 )
	    g10_log_fatal("read error on random device: %s\n", strerror(errno));
	(*add)( buffer, n, requester );
	length -= n;
    }
    memset(buffer, 0, sizeof(buffer) );

    return 0; /* success */
}



#ifndef IS_MODULE
static
#endif
const char * const gnupgext_version = "RNDLINUX ($Revision$)";

static struct {
    int class;
    int version;
    int (*func)(void);
} func_table[] = {
    { 40, 1, (int (*)(void))gather_random },
};



/****************
 * Enumerate the names of the functions together with informations about
 * this function. Set sequence to an integer with a initial value of 0 and
 * do not change it.
 * If what is 0 all kind of functions are returned.
 * Return values: class := class of function:
 *			   10 = message digest algorithm info function
 *			   11 = integer with available md algorithms
 *			   20 = cipher algorithm info function
 *			   21 = integer with available cipher algorithms
 *			   30 = public key algorithm info function
 *			   31 = integer with available pubkey algorithms
 *			   40 = get gather_random function
 *			   41 = get fast_random_poll function
 *		  version = interface version of the function/pointer
 *			    (currently this is 1 for all functions)
 */

#ifndef IS_MODULE
static
#endif
void *
gnupgext_enum_func( int what, int *sequence, int *class, int *vers )
{
    void *ret;
    int i = *sequence;

    do {
	if ( i >= DIM(func_table) || i < 0 ) {
	    return NULL;
	}
	*class = func_table[i].class;
	*vers  = func_table[i].version;
	ret = func_table[i].func;
	i++;
    } while ( what && what != *class );

    *sequence = i;
    return ret;
}

#ifndef IS_MODULE
void
rndlinux_constructor(void)
{
    register_internal_cipher_extension( gnupgext_version,
					gnupgext_enum_func );
}
#endif