Allow the internal DH implementation to be overridden

Crypto library wrappers can now override the internal DH (group 5)
implementation. As a starting point, this is done with OpenSSL. The
new mechanism is currently available only for WPS (i.e., IKEv2 still
depends on the internal DH implementation).

src/crypto/dh_group5.c

@@ -0,0 +1,40 @@
+/*
+ * Diffie-Hellman group 5 operations
+ * Copyright (c) 2009, Jouni Malinen <j@w1.fi>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * Alternatively, this software may be distributed under the terms of BSD
+ * license.
+ *
+ * See README and COPYING for more details.
+ */
+
+#include "includes.h"
+
+#include "common.h"
+#include "dh_groups.h"
+#include "dh_group5.h"
+
+
+void * dh5_init(struct wpabuf **priv, struct wpabuf **publ)
+{
+	*publ = dh_init(dh_groups_get(5), priv);
+	if (*publ == 0)
+		return NULL;
+	return (void *) 1;
+}
+
+
+struct wpabuf * dh5_derive_shared(void *ctx, const struct wpabuf *peer_public,
+				  const struct wpabuf *own_private)
+{
+	return dh_derive_shared(peer_public, own_private, dh_groups_get(5));
+}
+
+
+void dh5_free(void *ctx)
+{
+}