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/* 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 */
}
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