/*
 * Copyright (C) 2000, 2002, 2003, 2004, 2005 Free Software Foundation
 *
 * Author: Nikos Mavroyanopoulos
 *
 * This file is part of GNUTLS.
 *
 * The GNUTLS library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public License
 * as published by the Free Software Foundation; either version 2.1 of
 * the License, or (at your option) any later version.
 *
 * This library 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
 * USA
 *
 */

/* This file contains functions that manipulate a database backend
 * for resumed sessions. 
 */

#include "gnutls_int.h"
#include "gnutls_errors.h"
#include "gnutls_session.h"
#include <gnutls_db.h>
#include "debug.h"
#include <gnutls_session_pack.h>

/**
  * gnutls_db_set_retrieve_function - Sets the function that will be used to get data
  * @session: is a #gnutls_session_t structure.
  * @retr_func: is the function.
  *
  * Sets the function that will be used to retrieve data from the resumed
  * sessions database. This function must return a gnutls_datum_t containing the
  * data on success, or a gnutls_datum_t containing null and 0 on failure.
  *
  * The datum's data must be allocated using the function
  * gnutls_malloc().
  *
  * The first argument to store_function() will be null unless gnutls_db_set_ptr() 
  * has been called.
  *
  **/
void gnutls_db_set_retrieve_function(gnutls_session_t session,
				     gnutls_db_retr_func retr_func)
{
    session->internals.db_retrieve_func = retr_func;
}

/**
  * gnutls_db_set_remove_function - Sets the function that will be used to remove data
  * @session: is a #gnutls_session_t structure.
  * @rem_func: is the function.
  *
  * Sets the function that will be used to remove data from the resumed
  * sessions database. This function must return 0 on success.
  *
  * The first argument to rem_function() will be null unless gnutls_db_set_ptr() 
  * has been called.
  *
  **/
void gnutls_db_set_remove_function(gnutls_session_t session,
				   gnutls_db_remove_func rem_func)
{
    session->internals.db_remove_func = rem_func;
}

/**
  * gnutls_db_set_store_function - Sets the function that will be used to put data
  * @session: is a #gnutls_session_t structure.
  * @store_func: is the function
  *
  * Sets the function that will be used to store data from the resumed
  * sessions database. This function must remove 0 on success. 
  *
  * The first argument to store_function() will be null unless gnutls_db_set_ptr() 
  * has been called.
  *
  **/
void gnutls_db_set_store_function(gnutls_session_t session,
				  gnutls_db_store_func store_func)
{
    session->internals.db_store_func = store_func;
}

/**
  * gnutls_db_set_ptr - Sets a pointer to be sent to db functions
  * @session: is a #gnutls_session_t structure.
  * @ptr: is the pointer
  *
  * Sets the pointer that will be provided to db store, retrieve and delete functions, as
  * the first argument. 
  *
  **/
void gnutls_db_set_ptr(gnutls_session_t session, void *ptr)
{
    session->internals.db_ptr = ptr;
}

/**
  * gnutls_db_get_ptr - Returns the pointer which is sent to db functions
  * @session: is a #gnutls_session_t structure.
  *
  * Returns the pointer that will be sent to db store, retrieve and delete functions, as
  * the first argument. 
  *
  **/
void *gnutls_db_get_ptr(gnutls_session_t session)
{
    return session->internals.db_ptr;
}

/**
  * gnutls_db_set_cache_expiration - Sets the expiration time for resumed sessions.
  * @session: is a #gnutls_session_t structure.
  * @seconds: is the number of seconds.
  *
  * Sets the expiration time for resumed sessions. The default is 3600 (one hour)
  * at the time writing this.
  **/
void gnutls_db_set_cache_expiration(gnutls_session_t session, int seconds)
{
    session->internals.expire_time = seconds;
}

/**
  * gnutls_db_check_entry - checks if the given db entry has expired
  * @session: is a #gnutls_session_t structure.
  * @session_entry: is the session data (not key)
  *
  * This function returns GNUTLS_E_EXPIRED, if the database entry
  * has expired or 0 otherwise. This function is to be used when
  * you want to clear unnesessary session which occupy space in your
  * backend.
  *
  **/
int gnutls_db_check_entry(gnutls_session_t session,
			  gnutls_datum_t session_entry)
{
    time_t timestamp;

    timestamp = time(0);

    if (session_entry.data != NULL)
	if (timestamp -
	    ((security_parameters_st *) (session_entry.data))->timestamp <=
	    session->internals.expire_time
	    || ((security_parameters_st *) (session_entry.data))->
	    timestamp > timestamp
	    || ((security_parameters_st *) (session_entry.data))->
	    timestamp == 0)
	    return GNUTLS_E_EXPIRED;

    return 0;
}

/* The format of storing data is:
 * (forget it). Check gnutls_session_pack.c
 */
int _gnutls_server_register_current_session(gnutls_session_t session)
{
    gnutls_datum_t key;
    gnutls_datum_t content;
    int ret = 0;

    key.data = session->security_parameters.session_id;
    key.size = session->security_parameters.session_id_size;

    if (session->internals.resumable == RESUME_FALSE) {
	gnutls_assert();
	return GNUTLS_E_INVALID_SESSION;
    }

    if (session->security_parameters.session_id == NULL
	|| session->security_parameters.session_id_size == 0) {
	gnutls_assert();
	return GNUTLS_E_INVALID_SESSION;
    }

/* allocate space for data */
    ret = _gnutls_session_size(session);
    if (ret < 0) {
	gnutls_assert();
	return ret;
    }
    content.size = ret;

    content.data = gnutls_malloc(content.size);
    if (content.data == NULL) {
	gnutls_assert();
	return GNUTLS_E_MEMORY_ERROR;
    }

/* copy data */
    ret = _gnutls_session_pack(session, &content);
    if (ret < 0) {
	gnutls_free(content.data);
	gnutls_assert();
	return ret;
    }

    ret = _gnutls_store_session(session, key, content);

    gnutls_free(content.data);

    return ret;
}

/* Checks if both db_store and db_retrieve functions have
 * been set up.
 */
static int _gnutls_db_func_is_ok(gnutls_session_t session)
{
    if (session->internals.db_store_func != NULL &&
	session->internals.db_retrieve_func != NULL &&
	session->internals.db_remove_func != NULL)
	return 0;
    else
	return GNUTLS_E_DB_ERROR;
}


int _gnutls_server_restore_session(gnutls_session_t session,
				   uint8 * session_id, int session_id_size)
{
    gnutls_datum_t data;
    gnutls_datum_t key;
    int ret;

    key.data = session_id;
    key.size = session_id_size;

    if (_gnutls_db_func_is_ok(session) != 0) {
	gnutls_assert();
	return GNUTLS_E_INVALID_SESSION;
    }

    data = _gnutls_retrieve_session(session, key);

    if (data.data == NULL) {
	gnutls_assert();
	return GNUTLS_E_INVALID_SESSION;
    }

    /* expiration check is performed inside */
    ret = gnutls_session_set_data(session, data.data, data.size);
    if (ret < 0) {
	gnutls_assert();
	return ret;
    }

    gnutls_free(data.data);

    return 0;
}

int _gnutls_db_remove_session(gnutls_session_t session, uint8 * session_id,
			      int session_id_size)
{
    gnutls_datum_t key;

    key.data = session_id;
    key.size = session_id_size;

    return _gnutls_remove_session(session, key);
}


/* Stores session data to the db backend.
 */
int _gnutls_store_session(gnutls_session_t session,
			  gnutls_datum_t session_id,
			  gnutls_datum_t session_data)
{
    int ret = 0;

    if (session->internals.resumable == RESUME_FALSE) {
	gnutls_assert();
	return GNUTLS_E_INVALID_SESSION;
    }

    if (_gnutls_db_func_is_ok(session) != 0) {
	return GNUTLS_E_DB_ERROR;
    }

    if (session_id.data == NULL || session_id.size == 0) {
	gnutls_assert();
	return GNUTLS_E_INVALID_SESSION;
    }

    if (session_data.data == NULL || session_data.size == 0) {
	gnutls_assert();
	return GNUTLS_E_INVALID_SESSION;
    }
    /* if we can't read why bother writing? */

    if (session->internals.db_store_func != NULL)
	ret =
	    session->internals.db_store_func(session->internals.db_ptr,
					     session_id, session_data);

    return (ret == 0 ? ret : GNUTLS_E_DB_ERROR);

}

/* Retrieves session data from the db backend.
 */
gnutls_datum_t _gnutls_retrieve_session(gnutls_session_t session,
					gnutls_datum_t session_id)
{
    gnutls_datum_t ret = { NULL, 0 };

    if (session_id.data == NULL || session_id.size == 0) {
	gnutls_assert();
	return ret;
    }

    if (session->internals.db_retrieve_func != NULL)
	ret =
	    session->internals.db_retrieve_func(session->internals.db_ptr,
						session_id);

    return ret;

}

/* Removes session data from the db backend.
 */
int _gnutls_remove_session(gnutls_session_t session,
			   gnutls_datum_t session_id)
{
    int ret = 0;

    if (_gnutls_db_func_is_ok(session) != 0) {
	return GNUTLS_E_DB_ERROR;
    }

    if (session_id.data == NULL || session_id.size == 0)
	return GNUTLS_E_INVALID_SESSION;

    /* if we can't read why bother writing? */
    if (session->internals.db_remove_func != NULL)
	ret =
	    session->internals.db_remove_func(session->internals.db_ptr,
					      session_id);

    return (ret == 0 ? ret : GNUTLS_E_DB_ERROR);

}

/**
  * gnutls_db_remove_session - This function will remove the current session data from the database
  * @session: is a #gnutls_session_t structure.
  *
  * This function will remove the current session data from the session
  * database. This will prevent future handshakes reusing these session
  * data. This function should be called if a session was terminated
  * abnormally, and before gnutls_deinit() is called.
  *
  * Normally gnutls_deinit() will remove abnormally terminated sessions.
  *
  **/
void gnutls_db_remove_session(gnutls_session_t session)
{
    /* if the session has failed abnormally it has 
     * to be removed from the db 
     */
    _gnutls_db_remove_session(session,
			      session->security_parameters.session_id,
			      session->security_parameters.
			      session_id_size);
}