--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/pws-random.c	Tue Feb 10 11:29:54 2015 +0100
@@ -0,0 +1,61 @@
+/*
+ * Copyright (C) 2015 Guido Berhoerster <guido+libpws@berhoerster.name>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included
+ * in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+ * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+ * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
+ * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+ * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+#include "compat.h"
+#include "pws-internal.h"
+
+#ifdef	HAVE_ARC4RANDOM
+/* prefer system arc4random(3) implementation */
+#include <stdlib.h>
+#else /* HAVE_ARC4RANDOM */
+#ifdef	HAVE_GETENTROPY
+/*
+ * otherwise use system getentropy(2) implementation or fallback to seed
+ * Yarrow-256 PRNG from libnettle
+ */
+#include <unistd.h>
+#endif /* HAVE_GETENTROPY */
+#include <nettle/yarrow.h>
+#endif /* HAVE_ARC4RANDOM */
+
+#include "pws-internal.h"
+
+int
+pws_random_bytes(void *buf, size_t buf_size)
+{
+#ifdef	HAVE_ARC4RANDOM
+	arc4random_buf(buf, buf_size);
+#else /* HAVE_ARC4RANDOM */
+	struct yarrow256_ctx	ctx;
+	unsigned char		seed_buf[YARROW256_SEED_FILE_SIZE];
+
+	if (getentropy(&seed_buf, sizeof (seed_buf)) != 0) {
+		return (-1);
+	}
+	yarrow256_init(&ctx, 0, NULL);
+	yarrow256_seed(&ctx, sizeof (seed_buf), seed_buf);
+	yarrow256_random(&ctx, buf_size, buf);
+#endif /* HAVE_ARC4RANDOM */
+
+	return (0);
+}