/*
 * Copyright (C) 2006 Martin Willi
 *
 * Copyright (C) secunet Security Networks 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.
 */

/**
 * @defgroup eap_method eap_method
 * @{ @ingroup eap
 */

#ifndef EAP_METHOD_H_
#define EAP_METHOD_H_

typedef struct eap_method_t eap_method_t;
typedef enum eap_role_t eap_role_t;

#include <library.h>
#include <plugins/plugin.h>
#include <utils/identification.h>
#include <eap/eap.h>
#include <encoding/payloads/eap_payload.h>

/**
 * Role of an eap_method, SERVER or PEER (client)
 */
enum eap_role_t {
	EAP_SERVER,
	EAP_PEER,
};
/**
 * enum names for eap_role_t.
 */
extern enum_name_t *eap_role_names;

/**
 * Interface of an EAP method for server and client side.
 *
 * An EAP method initiates an EAP exchange and processes requests and
 * responses. An EAP method may need multiple exchanges before succeeding, and
 * the eap_authentication may use multiple EAP methods to authenticate a peer.
 * To accomplish these requirements, all EAP methods have their own
 * implementation while the eap_authenticator uses one or more of these
 * EAP methods. Sending of EAP(SUCCESS/FAILURE) message is not the job
 * of the method, the eap_authenticator does this.
 * An EAP method may establish a MSK, this is used the complete the
 * authentication. Even if a mutual EAP method is used, the traditional
 * AUTH payloads are required. Only these include the nonces and messages from
 * ike_sa_init and therefore prevent man in the middle attacks.
 * The EAP method must use an initial EAP identifier value != 0, as a preceding
 * EAP-Identity exchange always uses identifier 0.
 */
struct eap_method_t {

	/**
	 * Initiate the EAP exchange.
	 *
	 * initiate() is only usable for server implementations, as clients only
	 * reply to server requests.
	 * A eap_payload is created in "out" if result is NEED_MORE.
	 *
	 * @param out		eap_payload to send to the client
	 * @return
	 * 					- NEED_MORE, if an other exchange is required
	 * 					- FAILED, if unable to create eap request payload
	 */
	status_t (*initiate) (eap_method_t *this, eap_payload_t **out);

	/**
	 * Process a received EAP message.
	 *
	 * A eap_payload is created in "out" if result is NEED_MORE.
	 *
	 * @param in		eap_payload response received
	 * @param out		created eap_payload to send
	 * @return
	 * 					- NEED_MORE, if an other exchange is required
	 * 					- FAILED, if EAP method failed
	 * 					- SUCCESS, if EAP method succeeded
	 */
	status_t (*process) (eap_method_t *this, eap_payload_t *in,
						 eap_payload_t **out);

	/**
	 * Get the EAP type implemented in this method.
	 *
	 * @param vendor	pointer receiving vendor identifier for type, 0 for none
	 * @return			type of the EAP method
	 */
	eap_type_t (*get_type) (eap_method_t *this, uint32_t *vendor);

	/**
	 * Check if this EAP method authenticates the server.
	 *
	 * Some EAP methods provide mutual authentication and
	 * allow authentication using only EAP, if the peer supports it.
	 *
	 * @return			TRUE if methods provides mutual authentication
	 */
	bool (*is_mutual) (eap_method_t *this);

	/**
	 * Get the MSK established by this EAP method.
	 *
	 * Not all EAP methods establish a shared secret. For implementations of
	 * the EAP-Identity method, get_msk() returns the received identity.
	 *
	 * @note Returning NOT_SUPPORTED is important for implementations of EAP
	 * methods that don't establish an MSK.  In particular as client because
	 * key-generating EAP methods MUST fail to process EAP-Success messages if
	 * no MSK is established.
	 *
	 * @param msk			chunk receiving internal stored MSK
	 * @return
	 *						- SUCCESS, if MSK is established
	 * 						- FAILED, if MSK not established (yet)
	 *						- NOT_SUPPORTED, for non-MSK-establishing methods
	 */
	status_t (*get_msk) (eap_method_t *this, chunk_t *msk);

	/**
	 * Get the current EAP identifier.
	 *
	 * @return				current EAP identifier
	 */
	uint8_t (*get_identifier) (eap_method_t *this);

	/**
	 * Set the EAP identifier to a deterministic value, overwriting
	 * the randomly initialized default value.
	 *
	 * @param identifier	current EAP identifier
	 */
	void (*set_identifier) (eap_method_t *this, uint8_t identifier);

	/**
	 * Get authentication details performed by this EAP method.
	 *
	 * After EAP completion, the auth data contains additional information
	 * of the authentication process, used certificates etc.
	 * This method is optional to implement, but if it is, it must return
	 * a valid auth_cfg.
	 *
	 * @return				auth method, internal data
	 */
	auth_cfg_t* (*get_auth)(eap_method_t *this);

	/**
	 * Destroys a eap_method_t object.
	 */
	void (*destroy) (eap_method_t *this);
};

/**
 * Constructor definition for a pluggable EAP method.
 *
 * Each EAP module must define a constructor function which will return
 * an initialized object with the methods defined in eap_method_t.
 * Constructors for server and peers are identical, to support both roles
 * of a EAP method, a plugin needs register two constructors in the
 * eap_manager_t.
 * The passed identities are of type ID_EAP and valid only during the
 * constructor invocation.
 *
 * @param server		ID of the server to use for credential lookup
 * @param peer			ID of the peer to use for credential lookup
 * @return				implementation of the eap_method_t interface
 */
typedef eap_method_t *(*eap_constructor_t)(identification_t *server,
										   identification_t *peer);

/**
 * Helper function to (un-)register EAP methods from plugin features.
 *
 * This function is a plugin_feature_callback_t and can be used with the
 * PLUGIN_CALLBACK macro to register a EAP method constructor.
 *
 * @param plugin		plugin registering the EAP method constructor
 * @param feature		associated plugin feature
 * @param reg			TRUE to register, FALSE to unregister.
 * @param data			data passed to callback, an eap_constructor_t
 */
bool eap_method_register(plugin_t *plugin, plugin_feature_t *feature,
						 bool reg, void *data);

#endif /** EAP_METHOD_H_ @}*/
