if( isset($HTTP_POST_VARS['login']) || isset($HTTP_GET_VARS['login']) || isset($HTTP_POST_VARS['logout']) || isset($HTTP_GET_VARS['logout']) )
{
    if( ( isset($HTTP_POST_VARS['login']) || isset($HTTP_GET_VARS['login']) ) && (!$userdata['session_logged_in'] || isset($HTTP_POST_VARS['admin'])) )
    {
        $username = isset($HTTP_POST_VARS['username']) ? $HTTP_POST_VARS['username'] : '';
        $password = isset($HTTP_POST_VARS['password']) ? $HTTP_POST_VARS['password'] : '';

// Modified for SQL injection
        $sql = "SELECT user_id, username, user_password, user_active, user_level, user_login_tries, user_last_login_try
            FROM " . USERS_TABLE . "
            WHERE username = '" . $username . "'";
        if ( !($result = $db->sql_query($sql)) )
        {
            message_die(GENERAL_ERROR, 'Error in obtaining userdata', '', __LINE__, __FILE__, $sql);
        }

        if( $row = $db->sql_fetchrow($result) )
        {
            if( $row['user_level'] != ADMIN && $board_config['board_disable'] )
            {
                redirect(append_sid("index.$phpEx", true));
            }
            else
            {
                // If the last login is more than x minutes ago, then reset the login tries/time
                if ($row['user_last_login_try'] && $board_config['login_reset_time'] && $row['user_last_login_try'] < (time() - ($board_config['login_reset_time'] * 60)))
                {
                    $db->sql_query('UPDATE ' . USERS_TABLE . ' SET user_login_tries = 0, user_last_login_try = 0 WHERE user_id = ' . $row['user_id']);
                    $row['user_last_login_try'] = $row['user_login_tries'] = 0;
                }

                // Check to see if user is allowed to login again... if his tries are exceeded
                if ($row['user_last_login_try'] && $board_config['login_reset_time'] && $board_config['max_login_attempts'] &&
                    $row['user_last_login_try'] >= (time() - ($board_config['login_reset_time'] * 60)) && $row['user_login_tries'] >= $board_config['max_login_attempts'] && $userdata['user_level'] != ADMIN)
                {
                    message_die(GENERAL_MESSAGE, sprintf($lang['Login_attempts_exceeded'], $board_config['max_login_attempts'], $board_config['login_reset_time']));
                }

// Modified for SQL injection
                $sql_checkpasswd = "SELECT user_id, username, user_password, user_active, user_level, user_login_tries, user_last_login_try
                        FROM " . USERS_TABLE . "
                        WHERE username = '" . $username . "'" . " AND user_password = '" . md5($password). "'";
                if ( !($result_checkpasswd = $db->sql_query($sql_checkpasswd)) )
                {
                        message_die(GENERAL_ERROR, 'Error in obtaining userdata', '', __LINE__, __FILE__, $sql);
                }
                $row = $db->sql_fetchrow($result_checkpasswd);
                if($row && $row['user_active'] )
                {
                    $autologin = ( isset($HTTP_POST_VARS['autologin']) ) ? TRUE : 0;

                    $admin = (isset($HTTP_POST_VARS['admin'])) ? 1 : 0;
                    $session_id = session_begin($row['user_id'], $user_ip, PAGE_INDEX, FALSE, $autologin, $admin);

                    // Reset login tries
                    $db->sql_query('UPDATE ' . USERS_TABLE . ' SET user_login_tries = 0, user_last_login_try = 0 WHERE user_id = ' . $row['user_id']);

                    if( $session_id )
                    {
                        $url = ( !empty($HTTP_POST_VARS['redirect']) ) ? str_replace('&', '&', htmlspecialchars($HTTP_POST_VARS['redirect'])) : "index.$phpEx";
                        redirect(append_sid($url, true));
                    }
                    else
                    {
                        message_die(CRITICAL_ERROR, "Couldn't start session : login", "", __LINE__, __FILE__);
                    }
                }
                // Only store a failed login attempt for an active user - inactive users can't login even with a correct password
                elseif( $row['user_active'] )
                {
                    // Save login tries and last login
                    if ($row['user_id'] != ANONYMOUS)
                    {
                        $sql = 'UPDATE ' . USERS_TABLE . '
                            SET user_login_tries = user_login_tries + 1, user_last_login_try = ' . time() . '
                            WHERE user_id = ' . $row['user_id'];
                        $db->sql_query($sql);
                    }
                }

                $redirect = ( !empty($HTTP_POST_VARS['redirect']) ) ? str_replace('&', '&', htmlspecialchars($HTTP_POST_VARS['redirect'])) : '';
                $redirect = str_replace('?', '&', $redirect);

                if (strstr(urldecode($redirect), "\n") || strstr(urldecode($redirect), "\r") || strstr(urldecode($redirect), ';url'))
                {
                    message_die(GENERAL_ERROR, 'Tried to redirect to potentially insecure url.');
                }

                $template->assign_vars(array(
                    'META' => "<meta http-equiv=\"refresh\" content=\"3;url=login.$phpEx?redirect=$redirect\">")
                );

                $message = $lang['Error_login'] . '<br /><br />' . sprintf($lang['Click_return_login'], "<a href=\"login.$phpEx?redirect=$redirect\">", '</a>') . '<br /><br />' .  sprintf($lang['Click_return_index'], '<a href="' . append_sid("index.$phpEx") . '">', '</a>');

                message_die(GENERAL_MESSAGE, $message);
            }
        }
        else
        {
            $redirect = ( !empty($HTTP_POST_VARS['redirect']) ) ? str_replace('&', '&', htmlspecialchars($HTTP_POST_VARS['redirect'])) : "";
            $redirect = str_replace("?", "&", $redirect);

            if (strstr(urldecode($redirect), "\n") || strstr(urldecode($redirect), "\r") || strstr(urldecode($redirect), ';url'))
            {
                message_die(GENERAL_ERROR, 'Tried to redirect to potentially insecure url.');
            }

            $template->assign_vars(array(
                'META' => "<meta http-equiv=\"refresh\" content=\"3;url=login.$phpEx?redirect=$redirect\">")
            );

            $message = $lang['Error_login'] . '<br /><br />' . sprintf($lang['Click_return_login'], "<a href=\"login.$phpEx?redirect=$redirect\">", '</a>') . '<br /><br />' .  sprintf($lang['Click_return_index'], '<a href="' . append_sid("index.$phpEx") . '">', '</a>');

            message_die(GENERAL_MESSAGE, $message);
        }
    }
    else if( ( isset($HTTP_GET_VARS['logout']) || isset($HTTP_POST_VARS['logout']) ) && $userdata['session_logged_in'] )
    {
        // session id check
        if ($sid == '' || $sid != $userdata['session_id'])
        {
            message_die(GENERAL_ERROR, 'Invalid_session');
        }

        if( $userdata['session_logged_in'] )
        {
            session_end($userdata['session_id'], $userdata['user_id']);
        }

        if (!empty($HTTP_POST_VARS['redirect']) || !empty($HTTP_GET_VARS['redirect']))
        {
            $url = (!empty($HTTP_POST_VARS['redirect'])) ? htmlspecialchars($HTTP_POST_VARS['redirect']) : htmlspecialchars($HTTP_GET_VARS['redirect']);
            $url = str_replace('&', '&', $url);
            redirect(append_sid($url, true));
        }
        else
        {
            redirect(append_sid("index.$phpEx", true));
        }
    }
    else
    {
        $url = ( !empty($HTTP_POST_VARS['redirect']) ) ? str_replace('&', '&', htmlspecialchars($HTTP_POST_VARS['redirect'])) : "index.$phpEx";
        redirect(append_sid($url, true));
    }
}