Share common SAE and EAP-pwd functionality: suitable groups

Start sharing common SAE and EAP-pwd functionality by adding a new
source code file that can be included into both. This first step is
bringing in a shared function to check whether a group is suitable.

Signed-off-by: Jouni Malinen <jouni@codeaurora.org>

src/common/dragonfly.c

@@ -0,0 +1,27 @@
+/*
+ * Shared Dragonfly functionality
+ * Copyright (c) 2012-2016, Jouni Malinen <j@w1.fi>
+ * Copyright (c) 2019, The Linux Foundation
+ *
+ * This software may be distributed under the terms of the BSD license.
+ * See README for more details.
+ */
+
+#include "utils/includes.h"
+
+#include "utils/common.h"
+#include "dragonfly.h"
+
+
+int dragonfly_suitable_group(int group, int ecc_only)
+{
+	/* Enforce REVmd rules on which SAE groups are suitable for production
+	 * purposes: FFC groups whose prime is >= 3072 bits and ECC groups
+	 * defined over a prime field whose prime is >= 256 bits. Furthermore,
+	 * ECC groups defined over a characteristic 2 finite field and ECC
+	 * groups with a co-factor greater than 1 are not suitable. */
+	return group == 19 || group == 20 || group == 21 ||
+		group == 28 || group == 29 || group == 30 ||
+		(!ecc_only &&
+		 (group == 15 || group == 16 || group == 17 || group == 18));
+}