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/* random.c - random number generator
* Copyright (c) 1997 by Werner Koch (dd9jn)
*
* This file is part of G10.
*
* G10 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.
*
* G10 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 <errno.h>
#include "util.h"
#include "cipher.h"
static struct {
int level;
int len;
byte buffer[100]; /* fixme: should this be allocated in secure space? */
} cache;
/****************
* Fill the buffer with LENGTH bytes of cryptologic strong
* random bytes. level 0 is not very strong, 1 is strong enough
* for most usage, 2 is good for key generation stuff but may be very slow.
*/
void
randomize_buffer( byte *buffer, size_t length, int level )
{
FILE *fp;
if( level == 2 )
level = 1; /* 2 is much too slow */
fp = fopen(level < 2? "/dev/urandom":"/dev/random", "r");
if( !fp )
log_fatal("can't open random device: %s\n", strerror(errno) );
for( ; length; length-- )
*buffer++ = getc(fp);
fclose(fp);
}
byte
get_random_byte( int level )
{
if( !cache.len || cache.level < level ) {
randomize_buffer(cache.buffer, DIM(cache.buffer), level );
cache.level = level;
cache.len = DIM(cache.buffer);
}
return cache.buffer[--cache.len];
}
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