initially checkin

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];
+}
+
+