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<?php
/**
 * This program is part of Mahara
 *
 *  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.
 *
 *  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.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301 USA
 *
 * @package    mahara
 * @subpackage core
 * @author     Nigel McNie <nigel@catalyst.net.nz>
 * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL
 * @copyright  (C) 2006,2007 Catalyst IT Ltd http://catalyst.net.nz
 *
 */

defined('INTERNAL') || die();

/** Exception - unknown user */
class AuthUnknownUserException extends Exception {}

/**
 * Base authentication class. Provides a common interface with which
 * authentication can be carried out for system users.
 */
abstract class Auth {

    /**
     * Given a username, password and institution, attempts to log the use in.
     *
     * @param string $username  The username to attempt to authenticate
     * @param string $password  The password to use for the attempt
     * @param string $institute The institution the user belongs to
     * @return bool             Whether the authentication was successful
     * @throws AuthUnknownUserException  If the user is unknown to the
     *                                   authentication method
     */
    public static abstract function authenticate_user_account($username, $password, $institute);

    /**
     * Given a username, returns a hash of information about a user.
     *
     * @param string $username The username to look up information for
     * @return array           The information for the user
     * @throws AuthUnknownUserException If the user is unknown to the
     *                                  authentication method
     */
    public static abstract function get_user_info ($username);

    /**
     * Returns a hash of information that will be rendered into a form
     * when configuring authentication.
     *
     * @return array
     */
    public static function get_config_options () {
    }

    /**
     * Returns the internal name of the auth plugin.
     */
    public static function get_internal_name() {
        return get_string('internalname', 'auth');
    }

    /**
     * Returns the human readable name of the auth plugin.
     */
    public static function get_name() {
        return get_string('name', 'auth');
    }

    /**
     * Returns the descriptoin of the auth plugin
     */
    public static function get_description() {
        return get_string('description', 'auth');
    }

}


/**
 * Handles authentication by setting up a session for a user if they are logged
 * in.
 *
 * This function combined with the Session class is smart - if the user is not
 * logged in then they do not get a session, which prevents simple curl hits
 * or search engine crawls to a page from getting sessions they won't use.
 *
 * Once the user has a session, they keep it even if the log out, so it can
 * be reused. The session does expire, but the expiry time is typically a week
 * or more.
 */
function auth_setup () {
    global $SESSION;
    $time = time();

    // If the system is not installed, let the user through in the hope that
    // they can fix this little problem :)
    if (!get_config('installed')) {
        log_dbg('system not installed, letting user through');
        return;
    }

    // Check the time that the session is set to log out. If the user does
    // not have a session, this time will be 0.
    $sessionlogouttime = $SESSION->get('logout_time');
    if ($sessionlogouttime > $time) {
        if (isset($_GET['logout'])) {
            log_dbg('logging user ' . $SESSION->get('username') . ' out');
            $SESSION->logout();
            $SESSION->add_ok_msg(get_string('loggedoutok', 'mahara'));
            header('Location: ' . get_config('wwwroot'));
            exit;
        }
        // The session is still active, so continue it.
        log_dbg('session still active from previous time');
        return $SESSION->renew();
    }
    else if ($sessionlogouttime > 0) {
        // The session timed out
        log_dbg('session timed out');
        $SESSION->logout();
        $SESSION->add_info_msg(get_string('sessiontimedout', 'mahara'));
        // @todo<nigel>: if page is public, no need to show the login page again
        auth_draw_login_page();
        exit;
    }
    else {
        // There is no session, so we check to see if one needs to be started.
        // First, check if the page is public or the site is configured to be public.
        // @todo<nigel>: implement this :)
        if (false) {
            // No need to hand out a session for such pages
            return;
        }

        $username = (isset($_POST['login_username'])) ? $_POST['login_username'] : '';//clean_requestdata('login_username', PARAM_ALPHA);
        if ($username != '') {
            log_dbg('auth details supplied, attempting to log user in');
            $password = clean_requestdata('login_password', PARAM_ALPHA);
            $institution = clean_requestdata('login_institution', PARAM_INT);
            
            $authtype = auth_get_authtype_for_institution($institution);
            safe_require('auth', $authtype, 'lib.php');
            $authclass = 'Auth_' . ucfirst($authtype);
            try {
                if (eval("return $authclass::authenticate_user_account(\$username, \$password, \$institution);")) {
                    log_dbg('user ' . $username . ' logged in OK');
                    $USER = eval("return $authclass::get_user_info(\$username);");
                    $SESSION->login($USER);
                    $USER->logout_time = $SESSION->get('logout_time');
                    return $USER;
                }
                else {
                    // Login attempt failed
                    log_dbg('login attempt FAILED');
                    $SESSION->add_err_msg(get_string('loginfailed', 'mahara'));
                    auth_draw_login_page();
                    exit;
                }
            }
            catch (AuthUnknownUserException $e) {
                log_dbg('unknown user ' . $username);
                $SESSION->add_err_msg(get_string('loginfailed', 'mahara'));
                auth_draw_login_page();
                exit;
            }
        }
        else {
            // No login attempt, no session and page is private
            log_dbg('no session or old session, and page is private');
            auth_draw_login_page();
            exit;
        }
    }
}

/**
 * Given an institution, returns the authentication method used by it.
 *
 * @return string
 * @todo<nigel>: Currently, the system doesn't have a concept of institution
 * at the database level, so the internal authentication method is assumed.
 */
function auth_get_authtype_for_institution($institution) {
    return 'internal';
}

/**
 * Creates and displays the transient login page
 *
 */
function auth_draw_login_page() {
    $smarty = smarty();
    require_once('form.php');


    $elements = array(
        'login' => array(
            'type'   => 'fieldset',
            'legend' => get_string('login', 'mahara'),
            'elements' => array(
                'login_username' => array(
                    'type'        => 'text',
                    'title'       => get_string('username', 'mahara'),
                    'description' => get_string('usernamedesc', 'mahara'),
                    'help'        => get_string('usernamehelp', 'mahara'),
                    'required'    => true
                ),
                'login_password' => array(
                    'type'        => 'password',
                    'title'       => get_string('password', 'mahara'),
                    'description' => get_string('passworddesc', 'mahara'),
                    'help'        => get_string('passwordhelp', 'mahara'),
                    'required'    => true,
                    'value'       => ''
                )
            )
        ),

        'submit' => array(
            'type'  => 'submit',
            'value' => get_string('login', 'mahara')
        )
    );

    // The login page is completely transient, and it is smart because it
    // remembers the GET and POST data sent to it and resends that on
    // afterwards. 
    $action = '';
    if ($_GET) {
        if (isset($_GET['logout'])) {
            // You can log the user out on any particular page by appending
            // ?logout to the URL. In this case, we don't want the "action"
            // of the url to include that, or be blank, else the next time
            // the user logs in they will be logged out again.
            $action = hsc(substr($_SERVER['REQUEST_URI'], 0, strpos($_SERVER['REQUEST_URI'], '?')));
        } else {
            $action = '?';
            foreach ($_GET as $key => $value) {
                if ($key != 'logout') {
                    $action .= hsc($key) . '=' . hsc($value) . '&amp;';
                }
            }
            $action = substr($action, 0, -5);
        }
    }
    if ($_POST) {
        foreach ($_POST as $key => $value) {
            // @todo<nigel>: probably won't pass arrays properly
            if (!isset($elements[$key]) && !isset($elements['login']['elements'][$key])) {
                $elements[$key] = array(
                    'type'  => 'hidden',
                    'value' => $value
                );
            }
        }
    }

    $form = array(
        'name' => 'login',
        'method' => 'post',
        'action' => $action,
        'elements' => $elements
    );

    $smarty->assign('login_form', form($form));
    $smarty->display('login.tpl');
    exit;
}

function login_validate($form, $values) {
    if (!validate_username($values['login_username'])) {
        $form->set_error('login_username', get_string('Username is not in valid form, it can only'
           . ' contain alphanumeric characters, underscores, full stops and @ symbols', 'mahara'));
    }
}

function login_submit($values) {
    // Do nothing with the form submission - auth_setup() will handle it
    //global $SESSION;
    //$SESSION->add_ok_msg('logged in!');
    //header('Location: ' . get_config('wwwroot'));
    //exit;
}

?>