curve25519: Add a plugin providing Curve25519 DH using backend drivers

src/libstrongswan/plugins/curve25519/curve25519_dh.c

@@ -0,0 +1,174 @@
+/*
+ * Copyright (C) 2015 Martin Willi
+ * Copyright (C) 2015 revosec AG
+ *
+ * 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 <string.h>
+#include <stdint.h>
+
+#include "curve25519_dh.h"
+#include "curve25519_drv.h"
+
+typedef struct private_curve25519_dh_t private_curve25519_dh_t;
+
+/**
+ * Private data of an curve25519_dh_t object.
+ */
+struct private_curve25519_dh_t {
+
+	/**
+	 * Public curve25519_dh_t interface.
+	 */
+	curve25519_dh_t public;
+
+	/**
+	 * Shared key, if computed
+	 */
+	u_char shared[CURVE25519_KEY_SIZE];
+
+	/**
+	 * TRUE if shared secret is computed
+	 */
+	bool computed;
+
+	/**
+	 * Curve25519 backend
+	 */
+	curve25519_drv_t *drv;
+};
+
+/**
+ * Generate a valid Curve25519 key
+ */
+static bool generate_key(private_curve25519_dh_t *this)
+{
+	u_char key[CURVE25519_KEY_SIZE];
+	rng_t *rng;
+
+	rng = lib->crypto->create_rng(lib->crypto, RNG_STRONG);
+	if (!rng)
+	{
+		DBG1(DBG_LIB, "no RNG found for quality %N",
+			 rng_quality_names, RNG_STRONG);
+		return FALSE;
+	}
+	if (!rng->get_bytes(rng, CURVE25519_KEY_SIZE, key))
+	{
+		rng->destroy(rng);
+		return FALSE;
+	}
+	rng->destroy(rng);
+
+	return this->drv->set_key(this->drv, key);
+}
+
+METHOD(diffie_hellman_t, set_other_public_value, bool,
+	private_curve25519_dh_t *this, chunk_t value)
+{
+	if (value.len == CURVE25519_KEY_SIZE)
+	{
+		if (this->drv->curve25519(this->drv, value.ptr, this->shared))
+		{
+			this->computed = TRUE;
+			return TRUE;
+		}
+	}
+	return FALSE;
+}
+
+METHOD(diffie_hellman_t, get_my_public_value, bool,
+	private_curve25519_dh_t *this, chunk_t *value)
+{
+	u_char basepoint[CURVE25519_KEY_SIZE] = { 9 };
+
+	*value = chunk_alloc(CURVE25519_KEY_SIZE);
+	if (this->drv->curve25519(this->drv, basepoint, value->ptr))
+	{
+		return TRUE;
+	}
+	free(value->ptr);
+	return FALSE;
+}
+
+METHOD(diffie_hellman_t, set_private_value, bool,
+	private_curve25519_dh_t *this, chunk_t value)
+{
+	if (value.len != CURVE25519_KEY_SIZE)
+	{
+		return FALSE;
+	}
+	return this->drv->set_key(this->drv, value.ptr);
+}
+
+METHOD(diffie_hellman_t, get_shared_secret, bool,
+	private_curve25519_dh_t *this, chunk_t *secret)
+{
+	if (!this->computed)
+	{
+		return FALSE;
+	}
+	*secret = chunk_clone(chunk_from_thing(this->shared));
+	return TRUE;
+}
+
+METHOD(diffie_hellman_t, get_dh_group, diffie_hellman_group_t,
+	private_curve25519_dh_t *this)
+{
+	return CURVE_25519;
+}
+
+METHOD(diffie_hellman_t, destroy, void,
+	private_curve25519_dh_t *this)
+{
+	this->drv->destroy(this->drv);
+	free(this);
+}
+
+/*
+ * Described in header.
+ */
+curve25519_dh_t *curve25519_dh_create(diffie_hellman_group_t group)
+{
+	private_curve25519_dh_t *this;
+
+	if (group != CURVE_25519)
+	{
+		return FALSE;
+	}
+
+	INIT(this,
+		.public = {
+			.dh = {
+				.get_shared_secret = _get_shared_secret,
+				.set_other_public_value = _set_other_public_value,
+				.get_my_public_value = _get_my_public_value,
+				.set_private_value = _set_private_value,
+				.get_dh_group = _get_dh_group,
+				.destroy = _destroy,
+			},
+		},
+		.drv = curve25519_drv_probe(),
+	);
+
+	if (!this->drv)
+	{
+		free(this);
+		return NULL;
+	}
+	if (!generate_key(this))
+	{
+		destroy(this);
+		return NULL;
+	}
+	return &this->public;
+}