diff options
Diffstat (limited to 'cipher/random.c')
-rw-r--r-- | cipher/random.c | 67 |
1 files changed, 67 insertions, 0 deletions
diff --git a/cipher/random.c b/cipher/random.c new file mode 100644 index 00000000..73a9a3eb --- /dev/null +++ b/cipher/random.c @@ -0,0 +1,67 @@ +/* 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]; +} + + |