crypto: Add NULL IV generator

This does not actually allocate an IV and only accepts requests
for size == 0.

src/libstrongswan/crypto/iv/iv_gen_null.c

@@ -0,0 +1,63 @@
+/*
+ * Copyright (C) 2015 Tobias Brunner
+ * Hochschule fuer Technik Rapperswil
+ *
+ * This program 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.  See <http://www.fsf.org/copyleft/gpl.txt>.
+ *
+ * This program 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.
+ */
+
+#include "iv_gen_null.h"
+
+typedef struct private_iv_gen_t private_iv_gen_t;
+
+/**
+ * Private data of an iv_gen_t object.
+ */
+struct private_iv_gen_t {
+
+	/**
+	 * Public iv_gen_t interface.
+	 */
+	iv_gen_t public;
+};
+
+METHOD(iv_gen_t, get_iv, bool,
+	private_iv_gen_t *this, u_int64_t seq, size_t size, u_int8_t *buffer)
+{
+	return size == 0;
+}
+
+METHOD(iv_gen_t, allocate_iv, bool,
+	private_iv_gen_t *this, u_int64_t seq, size_t size, chunk_t *chunk)
+{
+	*chunk = chunk_empty;
+	return size == 0;
+}
+
+METHOD(iv_gen_t, destroy, void,
+	private_iv_gen_t *this)
+{
+	free(this);
+}
+
+iv_gen_t *iv_gen_null_create()
+{
+	private_iv_gen_t *this;
+
+	INIT(this,
+		.public = {
+			.get_iv = _get_iv,
+			.allocate_iv = _allocate_iv,
+			.destroy = _destroy,
+		},
+	);
+
+	return &this->public;
+}

src/libstrongswan/crypto/iv/iv_gen_null.h

@@ -0,0 +1,32 @@
+/*
+ * Copyright (C) 2015 Tobias Brunner
+ * Hochschule fuer Technik Rapperswil
+ *
+ * This program 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.  See <http://www.fsf.org/copyleft/gpl.txt>.
+ *
+ * This program 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.
+ */
+
+/**
+ * @{ @ingroup iv
+ */
+
+#ifndef IV_GEN_NULL_H_
+#define IV_GEN_NULL_H_
+
+#include <crypto/iv/iv_gen.h>
+
+/**
+ * Create an IV generator that does not actually generate an IV.
+ *
+ * @return		IV generator
+ */
+iv_gen_t *iv_gen_null_create();
+
+#endif /** IV_GEN_NULL_H_ @}*/