<?php

/**
 * @author Martin Dougiamas
 * @license http://www.gnu.org/copyleft/gpl.html GNU Public License
 * @package moodle multiauth
 *
 * Authentication Plugin: LDAP Authentication
 *
 * Authentication using LDAP (Lightweight Directory Access Protocol).
 *
 * 2006-08-28  File created.
 */

if (!defined('MOODLE_INTERNAL')) {
    die('Direct access to this script is forbidden.');    ///  It must be included from a Moodle page
}

// See http://support.microsoft.com/kb/305144 to interprete these values.
if (!defined('AUTH_AD_ACCOUNTDISABLE')) {
    define('AUTH_AD_ACCOUNTDISABLE', 0x0002);
}
if (!defined('AUTH_AD_NORMAL_ACCOUNT')) {
    define('AUTH_AD_NORMAL_ACCOUNT', 0x0200);
}
if (!defined('AUTH_NTLMTIMEOUT')) {  // timewindow for the NTLM SSO process, in secs...
    define('AUTH_NTLMTIMEOUT', 10);
}


require_once($CFG->libdir.'/authlib.php');

/**
 * LDAP authentication plugin.
 */
class auth_plugin_ldap extends auth_plugin_base {

    /**
     * Constructor with initialisation.
     */
    function auth_plugin_ldap() {
        $this->authtype = 'ldap';
        $this->config = get_config('auth/ldap');
        if (empty($this->config->ldapencoding)) {
            $this->config->ldapencoding = 'utf-8';
        }
        if (empty($this->config->user_type)) {
            $this->config->user_type = 'default';
        }

        $default = $this->ldap_getdefaults();

        //use defaults if values not given
        foreach ($default as $key => $value) {
            // watch out - 0, false are correct values too
            if (!isset($this->config->{$key}) or $this->config->{$key} == '') {
                $this->config->{$key} = $value[$this->config->user_type];
            }
        }

        // Hack prefix to objectclass
        if (empty($this->config->objectclass)) {
            // Can't send empty filter
            $this->config->objectclass='(objectClass=*)';
        } else if (stripos($this->config->objectclass, 'objectClass=') === 0) {
            // Value is 'objectClass=some-string-here', so just add ()
            // around the value (filter _must_ have them).
            $this->config->objectclass = '('.$this->config->objectclass.')';
        } else if (stripos($this->config->objectclass, '(') !== 0) {
            // Value is 'some-string-not-starting-with-left-parentheses',
            // which is assumed to be the objectClass matching value.
            // So build a valid filter with it.
            $this->config->objectclass = '(objectClass='.$this->config->objectclass.')';
        } else {
            // There is an additional possible value
            // '(some-string-here)', that can be used to specify any
            // valid filter string, to select subsets of users based
            // on any criteria. For example, we could select the users
            // whose objectClass is 'user' and have the
            // 'enabledMoodleUser' attribute, with something like:
            //
            //   (&(objectClass=user)(enabledMoodleUser=1))
            //
            // This is only used in the functions that deal with the
            // whole potential set of users (currently sync_users()
            // and get_user_list() only).
            //
            // In this particular case we don't need to do anything,
            // so leave $this->config->objectclass as is.
        }

    }

    /**
     * Returns true if the username and password work and false if they are
     * wrong or don't exist.
     *
     * @param string $username The username (with system magic quotes)
     * @param string $password The password (with system magic quotes)
     *
     * @return bool Authentication success or failure.
     */
    function user_login($username, $password) {
        if (! function_exists('ldap_bind')) {
            print_error('auth_ldapnotinstalled','auth');
            return false;
        }

        if (!$username or !$password) {    // Don't allow blank usernames or passwords
            return false;
        }

        $textlib = textlib_get_instance();
        $extusername = $textlib->convert(stripslashes($username), 'utf-8', $this->config->ldapencoding);
        $extpassword = $textlib->convert(stripslashes($password), 'utf-8', $this->config->ldapencoding);

        //
        // Before we connect to LDAP, check if this is an AD SSO login
        // if we succeed in this block, we'll return success early.
        //
        $key = sesskey();
        if (!empty($this->config->ntlmsso_enabled) && $key === $password) {
            $cf = get_cache_flags('auth/ldap/ntlmsess');
            // We only get the cache flag if we retrieve it before
            // it expires (AUTH_NTLMTIMEOUT seconds).
            if (!isset($cf[$key]) || $cf[$key] === '') {
                return false;
            }

            $sessusername = $cf[$key];
            if ($username === $sessusername) {
                unset($sessusername);
                unset($cf);

                // Check that the user is inside one of the configured LDAP contexts
                $validuser = false;
                $ldapconnection = $this->ldap_connect();
                if ($ldapconnection) {
                    // if the user is not inside the configured contexts,
                    // ldap_find_userdn returns false.
                    if ($this->ldap_find_userdn($ldapconnection, $extusername)) {
                        $validuser = true;
                    }
                    $this->ldap_close();
                }

                // Shortcut here - SSO confirmed
                return $validuser;
            }
        } // End SSO processing
        unset($key);

        $ldapconnection = $this->ldap_connect();
        if ($ldapconnection) {
            $ldap_user_dn = $this->ldap_find_userdn($ldapconnection, $extusername);

            //if ldap_user_dn is empty, user does not exist
            if (!$ldap_user_dn) {
                $this->ldap_close();
                return false;
            }

            // Try to bind with current username and password
            $ldap_login = @ldap_bind($ldapconnection, $ldap_user_dn, $extpassword);
            $this->ldap_close();
            if ($ldap_login) {
                return true;
            }
        }
        else {
            $this->ldap_close();
            print_error('auth_ldap_noconnect','auth','',$this->config->host_url);
        }
        return false;
    }

    /**
     * reads userinformation from ldap and return it in array()
     *
     * Read user information from external database and returns it as array().
     * Function should return all information available. If you are saving
     * this information to moodle user-table you should honor syncronization flags
     *
     * @param string $username username (with system magic quotes)
     *
     * @return mixed array with no magic quotes or false on error
     */
    function get_userinfo($username) {
        $textlib = textlib_get_instance();
        $extusername = $textlib->convert(stripslashes($username), 'utf-8', $this->config->ldapencoding);

        $ldapconnection = $this->ldap_connect();
        $attrmap = $this->ldap_attributes();

        $result = array();
        $search_attribs = array();

        foreach ($attrmap as $key=>$values) {
            if (!is_array($values)) {
                $values = array($values);
            }
            foreach ($values as $value) {
                if (!in_array($value, $search_attribs)) {
                    array_push($search_attribs, $value);
                }
            }
        }

        $user_dn = $this->ldap_find_userdn($ldapconnection, $extusername);

        if (!$user_info_result = ldap_read($ldapconnection, $user_dn, $this->config->objectclass, $search_attribs)) {
            return false; // error!
        }
        $user_entry = $this->ldap_get_entries($ldapconnection, $user_info_result);
        if (empty($user_entry)) {
            return false; // entry not found
        }

        foreach ($attrmap as $key=>$values) {
            if (!is_array($values)) {
                $values = array($values);
            }
            $ldapval = NULL;
            foreach ($values as $value) {
                if ((moodle_strtolower($value) == 'dn') || (moodle_strtolower($value) == 'distinguishedname')) {
                    $result[$key] = $user_dn;
                }
                if (!array_key_exists($value, $user_entry[0])) {
                    continue; // wrong data mapping!
                }
                if (is_array($user_entry[0][$value])) {
                    $newval = $textlib->convert($user_entry[0][$value][0], $this->config->ldapencoding, 'utf-8');
                } else {
                    $newval = $textlib->convert($user_entry[0][$value], $this->config->ldapencoding, 'utf-8');
                }
                if (!empty($newval)) { // favour ldap entries that are set
                    $ldapval = $newval;
                }
            }
            if (!is_null($ldapval)) {
                $result[$key] = $ldapval;
            }
        }

        $this->ldap_close();
        return $result;
    }

    /**
     * reads userinformation from ldap and return it in an object
     *
     * @param string $username username (with system magic quotes)
     * @return mixed object or false on error
     */
    function get_userinfo_asobj($username) {
        $user_array = $this->get_userinfo($username);
        if ($user_array == false) {
            return false; //error or not found
        }
        $user_array = truncate_userinfo($user_array);
        $user = new object();
        foreach ($user_array as $key=>$value) {
            $user->{$key} = $value;
        }
        return $user;
    }

    /**
     * returns all usernames from external database
     *
     * get_userlist returns all usernames from external database
     *
     * @return array
     */
    function get_userlist() {
        return $this->ldap_get_userlist("({$this->config->user_attribute}=*)");
    }

    /**
     * checks if user exists on external db
     *
     * @param string $username (with system magic quotes)
     */
    function user_exists($username) {

        $textlib = textlib_get_instance();
        $extusername = $textlib->convert(stripslashes($username), 'utf-8', $this->config->ldapencoding);

        //returns true if given username exist on ldap
        $users = $this->ldap_get_userlist("({$this->config->user_attribute}=".$this->filter_addslashes($extusername).")");
        return count($users);
    }

    /**
     * Creates a new user on external database.
     * By using information in userobject
     * Use user_exists to prevent dublicate usernames
     *
     * @param mixed $userobject  Moodle userobject  (with system magic quotes)
     * @param mixed $plainpass   Plaintext password (with system magic quotes)
     */
    function user_create($userobject, $plainpass) {
        $textlib = textlib_get_instance();
        $extusername = $textlib->convert(stripslashes($userobject->username), 'utf-8', $this->config->ldapencoding);
        $extpassword = $textlib->convert(stripslashes($plainpass), 'utf-8', $this->config->ldapencoding);

        switch ($this->config->passtype) {
            case 'md5':
                $extpassword = '{MD5}' . base64_encode(pack('H*', md5($extpassword)));
                break;
            case 'sha1':
                $extpassword = '{SHA}' . base64_encode(pack('H*', sha1($extpassword)));
                break;
            case 'plaintext':
            default:
                break; // plaintext
        }

        $ldapconnection = $this->ldap_connect();
        $attrmap = $this->ldap_attributes();

        $newuser = array();

        foreach ($attrmap as $key => $values) {
            if (!is_array($values)) {
                $values = array($values);
            }
            foreach ($values as $value) {
                if (!empty($userobject->$key) ) {
                    $newuser[$value] = $textlib->convert(stripslashes($userobject->$key), 'utf-8', $this->config->ldapencoding);
                }
            }
        }

        //Following sets all mandatory and other forced attribute values
        //User should be creted as login disabled untill email confirmation is processed
        //Feel free to add your user type and send patches to paca@sci.fi to add them
        //Moodle distribution

        switch ($this->config->user_type)  {
            case 'edir':
                $newuser['objectClass']   = array("inetOrgPerson","organizationalPerson","person","top");
                $newuser['uniqueId']      = $extusername;
                $newuser['logindisabled'] = "TRUE";
                $newuser['userpassword']  = $extpassword;
                $uadd = ldap_add($ldapconnection, $this->config->user_attribute.'="'.$this->ldap_addslashes($userobject->username).','.$this->config->create_context.'"', $newuser);
                break;
            case 'ad':
                // User account creation is a two step process with AD. First you
                // create the user object, then you set the password. If you try
                // to set the password while creating the user, the operation
                // fails.

                // Passwords in Active Directory must be encoded as Unicode
                // strings (UCS-2 Little Endian format) and surrounded with
                // double quotes. See http://support.microsoft.com/?kbid=269190
                if (!function_exists('mb_convert_encoding')) {
                    print_error ('auth_ldap_no_mbstring', 'auth');
                }

                // First create the user account, and mark it as disabled.
                $newuser['objectClass'] = array('top','person','user','organizationalPerson');
                $newuser['sAMAccountName'] = $extusername;
                $newuser['userAccountControl'] = AUTH_AD_NORMAL_ACCOUNT |
                                                 AUTH_AD_ACCOUNTDISABLE;
                $userdn = 'cn=' .  $this->ldap_addslashes($extusername) .
                          ',' . $this->config->create_context;
                if (!ldap_add($ldapconnection, $userdn, $newuser)) {
                    print_error ('auth_ldap_ad_create_req', 'auth');
                }

                // Now set the password
                unset($newuser);
                $newuser['unicodePwd'] = mb_convert_encoding('"' . $extpassword . '"',
                                                             "UCS-2LE", "UTF-8");
                if(!ldap_modify($ldapconnection, $userdn, $newuser)) {
                    // Something went wrong: delete the user account and error out
                    ldap_delete ($ldapconnection, $userdn);
                    print_error ('auth_ldap_ad_create_req', 'auth');
                }
                $uadd = true;
                break;
            default:
               print_error('auth_ldap_unsupportedusertype','auth','',$this->config->user_type);
        }
        $this->ldap_close();
        return $uadd;

    }

    function can_reset_password() {
        return !empty($this->config->stdchangepassword);
    }

    function can_signup() {
        return (!empty($this->config->auth_user_create) and !empty($this->config->create_context));
    }

    /**
     * Sign up a new user ready for confirmation.
     * Password is passed in plaintext.
     *
     * @param object $user new user object (with system magic quotes)
     * @param boolean $notify print notice with link and terminate
     */
    function user_signup($user, $notify=true) {
        global $CFG;
        require_once($CFG->dirroot.'/user/profile/lib.php');
        
        if ($this->user_exists($user->username)) {
            print_error('auth_ldap_user_exists', 'auth');
        }

        $plainslashedpassword = $user->password;
        unset($user->password);

        if (! $this->user_create($user, $plainslashedpassword)) {
            print_error('auth_ldap_create_error', 'auth');
        }

        if (! ($user->id = insert_record('user', $user)) ) {
            print_error('auth_emailnoinsert', 'auth');
        }

        /// Save any custom profile field information
        profile_save_data($user);

        $this->update_user_record($user->username);
        update_internal_user_password($user, $plainslashedpassword);

        $user = get_record('user', 'id', $user->id);
        events_trigger('user_created', $user);

        if (! send_confirmation_email($user)) {
            print_error('auth_emailnoemail', 'auth');
        }

        if ($notify) {
            global $CFG;
            $emailconfirm = get_string('emailconfirm');
            $navlinks = array();
            $navlinks[] = array('name' => $emailconfirm, 'link' => null, 'type' => 'misc');
            $navigation = build_navigation($navlinks);

            print_header($emailconfirm, $emailconfirm, $navigation);
            notice(get_string('emailconfirmsent', '', $user->email), "$CFG->wwwroot/index.php");
        } else {
            return true;
        }
    }

    /**
     * Returns true if plugin allows confirming of new users.
     *
     * @return bool
     */
    function can_confirm() {
        return $this->can_signup();
    }

    /**
     * Confirm the new user as registered.
     *
     * @param string $username (with system magic quotes)
     * @param string $confirmsecret (with system magic quotes)
     */
    function user_confirm($username, $confirmsecret) {
        $user = get_complete_user_data('username', $username);

        if (!empty($user)) {
            if ($user->confirmed) {
                return AUTH_CONFIRM_ALREADY;

            } else if ($user->auth != 'ldap') {
                return AUTH_CONFIRM_ERROR;

            } else if ($user->secret == stripslashes($confirmsecret)) {   // They have provided the secret key to get in
                if (!$this->user_activate($username)) {
                    return AUTH_CONFIRM_FAIL;
                }
                if (!set_field("user", "confirmed", 1, "id", $user->id)) {
                    return AUTH_CONFIRM_FAIL;
                }
                if (!set_field("user", "firstaccess", time(), "id", $user->id)) {
                    return AUTH_CONFIRM_FAIL;
                }
                return AUTH_CONFIRM_OK;
            }
        } else {
            return AUTH_CONFIRM_ERROR;
        }
    }

    /**
     * return number of days to user password expires
     *
     * If userpassword does not expire it should return 0. If password is already expired
     * it should return negative value.
     *
     * @param mixed $username username (with system magic quotes)
     * @return integer
     */
    function password_expire($username) {
        $result = 0;

        $textlib = textlib_get_instance();
        $extusername = $textlib->convert(stripslashes($username), 'utf-8', $this->config->ldapencoding);

        $ldapconnection = $this->ldap_connect();
        $user_dn = $this->ldap_find_userdn($ldapconnection, $extusername);
        $search_attribs = array($this->config->expireattr);
        $sr = ldap_read($ldapconnection, $user_dn, '(objectClass=*)', $search_attribs);
        if ($sr)  {
            $info = $this->ldap_get_entries($ldapconnection, $sr);
            if (!empty ($info) and !empty($info[0][$this->config->expireattr][0])) {
                $expiretime = $this->ldap_expirationtime2unix($info[0][$this->config->expireattr][0], $ldapconnection, $user_dn);
                if ($expiretime != 0) {
                    $now = time();
                    if ($expiretime > $now) {
                        $result = ceil(($expiretime - $now) / DAYSECS);
                    }
                    else {
                        $result = floor(($expiretime - $now) / DAYSECS);
                    }
                }
            }
        } else {
            error_log("ldap: password_expire did't find expiration time.");
        }

        //error_log("ldap: password_expire user $user_dn expires in $result days!");
        return $result;
    }

    /**
     * syncronizes user fron external db to moodle user table
     *
     * Sync is now using username attribute.
     *
     * Syncing users removes or suspends users that dont exists anymore in external db.
     * Creates new users and updates coursecreator status of users.
     *
     * @param int $bulk_insert_records will insert $bulkinsert_records per insert statement
     *                         valid only with $unsafe. increase to a couple thousand for
     *                         blinding fast inserts -- but test it: you may hit mysqld's
     *                         max_allowed_packet limit.
     * @param bool $do_updates will do pull in data updates from ldap if relevant
     */
    function sync_users ($bulk_insert_records = 1000, $do_updates = true) {

        global $CFG;

        $textlib = textlib_get_instance();

        $droptablesql = array(); /// sql commands to drop the table (because session scope could be a problem for
                                 /// some persistent drivers like ODBTP (mssql) or if this function is invoked
                                 /// from within a PHP application using persistent connections
        $temptable = $CFG->prefix . 'extuser';
        $createtemptablesql = '';

        // configure a temp table
        print "Configuring temp table\n";
        switch (strtolower($CFG->dbfamily)) {
            case 'mysql':
                $droptablesql[] = 'DROP TEMPORARY TABLE ' . $temptable; // sql command to drop the table (because session scope could be a problem)
                $createtemptablesql = 'CREATE TEMPORARY TABLE ' . $temptable . ' (username VARCHAR(64), PRIMARY KEY (username)) TYPE=MyISAM';
                break;
            case 'postgres':
                $droptablesql[] = 'DROP TABLE ' . $temptable; // sql command to drop the table (because session scope could be a problem)
                $bulk_insert_records = 1; // no support for multiple sets of values
                $createtemptablesql = 'CREATE TEMPORARY TABLE '. $temptable . ' (username VARCHAR(64), PRIMARY KEY (username))';
                break;
            case 'mssql':
                $temptable = '#'. $temptable; /// MSSQL temp tables begin with #
                $droptablesql[] = 'DROP TABLE ' . $temptable; // sql command to drop the table (because session scope could be a problem)
                $bulk_insert_records = 1; // no support for multiple sets of values
                $createtemptablesql = 'CREATE TABLE ' . $temptable . ' (username VARCHAR(64), PRIMARY KEY (username))';
                break;
            case 'oracle':
                $droptablesql[] = 'TRUNCATE TABLE ' . $temptable; // oracle requires truncate before being able to drop a temp table
                $droptablesql[] = 'DROP TABLE ' . $temptable; // sql command to drop the table (because session scope could be a problem)
                $bulk_insert_records = 1; // no support for multiple sets of values
                $createtemptablesql = 'CREATE GLOBAL TEMPORARY TABLE '.$temptable.' (username VARCHAR(64), PRIMARY KEY (username)) ON COMMIT PRESERVE ROWS';
                break;
        }


        execute_sql_arr($droptablesql, true, false); /// Drop temp table to avoid persistence problems later
        echo "Creating temp table $temptable\n";
        if(! execute_sql($createtemptablesql, false) ){
            print  "Failed to create temporary users table - aborting\n";
            exit;
        }

        print "Connecting to ldap...\n";
        $ldapconnection = $this->ldap_connect();

        if (!$ldapconnection) {
            $this->ldap_close();
            print get_string('auth_ldap_noconnect','auth',$this->config->host_url);
            exit;
        }

        ////
        //// get user's list from ldap to sql in a scalable fashion
        ////
        // prepare some data we'll need
        $filter = '(&('.$this->config->user_attribute.'=*)'.$this->config->objectclass.')';

        $contexts = explode(";",$this->config->contexts);

        if (!empty($this->config->create_context)) {
              array_push($contexts, $this->config->create_context);
        }

        $fresult = array();
        foreach ($contexts as $context) {
            $context = trim($context);
            if (empty($context)) {
                continue;
            }
            begin_sql();
            if ($this->config->search_sub) {
                //use ldap_search to find first user from subtree
                $ldap_result = ldap_search($ldapconnection, $context,
                                           $filter,
                                           array($this->config->user_attribute));
            } else {
                //search only in this context
                $ldap_result = ldap_list($ldapconnection, $context,
                                         $filter,
                                         array($this->config->user_attribute));
            }

            if ($entry = ldap_first_entry($ldapconnection, $ldap_result)) {
                do {
                    $value = ldap_get_values_len($ldapconnection, $entry, $this->config->user_attribute);
                    $value = $textlib->convert($value[0], $this->config->ldapencoding, 'utf-8');
                    // usernames are __always__ lowercase.
                    array_push($fresult, moodle_strtolower($value));
                    if (count($fresult) >= $bulk_insert_records) {
                        $this->ldap_bulk_insert($fresult, $temptable);
                        $fresult = array();
                    }
                } while ($entry = ldap_next_entry($ldapconnection, $entry));
            }
            unset($ldap_result); // free mem

            // insert any remaining users and release mem
            if (count($fresult)) {
                $this->ldap_bulk_insert($fresult, $temptable);
                $fresult = array();
            }
            commit_sql();
        }

        /// preserve our user database
        /// if the temp table is empty, it probably means that something went wrong, exit
        /// so as to avoid mass deletion of users; which is hard to undo
        $count = get_record_sql('SELECT COUNT(username) AS count, 1 FROM ' . $temptable);
        $count = $count->{'count'};
        if ($count < 1) {
            print "Did not get any users from LDAP -- error? -- exiting\n";
            exit;
        } else {
            print "Got $count records from LDAP\n\n";
        }


/// User removal
        // find users in DB that aren't in ldap -- to be removed!
        // this is still not as scalable (but how often do we mass delete?)
        if (!empty($this->config->removeuser)) {
            $sql = "SELECT u.id, u.username, u.email, u.auth 
                    FROM {$CFG->prefix}user u
                        LEFT JOIN $temptable e ON u.username = e.username
                    WHERE u.auth='ldap'
                        AND u.deleted=0
                        AND e.username IS NULL";
            $remove_users = get_records_sql($sql);

            if (!empty($remove_users)) {
                print "User entries to remove: ". count($remove_users) . "\n";

                foreach ($remove_users as $user) {
                    if ($this->config->removeuser == 2) {
                        if (delete_user($user)) {
                            echo "\t"; print_string('auth_dbdeleteuser', 'auth', array($user->username, $user->id)); echo "\n";
                        } else {
                            echo "\t"; print_string('auth_dbdeleteusererror', 'auth', $user->username); echo "\n";
                        }
                    } else if ($this->config->removeuser == 1) {
                        $updateuser = new object();
                        $updateuser->id = $user->id;
                        $updateuser->auth = 'nologin';
                        if (update_record('user', $updateuser)) {
                            echo "\t"; print_string('auth_dbsuspenduser', 'auth', array($user->username, $user->id)); echo "\n";
                        } else {
                            echo "\t"; print_string('auth_dbsuspendusererror', 'auth', $user->username); echo "\n";
                        }
                    }
                }
            } else {
                print "No user entries to be removed\n";
            }
            unset($remove_users); // free mem!
        }

/// Revive suspended users
        if (!empty($this->config->removeuser) and $this->config->removeuser == 1) {
            $sql = "SELECT u.id, u.username
                    FROM $temptable e, {$CFG->prefix}user u
                    WHERE e.username=u.username
                        AND u.auth='nologin'";
            $revive_users = get_records_sql($sql);

            if (!empty($revive_users)) {
                print "User entries to be revived: ". count($revive_users) . "\n";

                begin_sql();
                foreach ($revive_users as $user) {
                    $updateuser = new object();
                    $updateuser->id = $user->id;
                    $updateuser->auth = 'ldap';
                    if (update_record('user', $updateuser)) {
                        echo "\t"; print_string('auth_dbreviveduser', 'auth', array($user->username, $user->id)); echo "\n";
                    } else {
                        echo "\t"; print_string('auth_dbrevivedusererror', 'auth', $user->username); echo "\n";
                    }
                }
                commit_sql();
            } else {
                print "No user entries to be revived\n";
            }

            unset($revive_users);
        }


/// User Updates - time-consuming (optional)
        if ($do_updates) {
            // narrow down what fields we need to update
            $all_keys = array_keys(get_object_vars($this->config));
            $updatekeys = array();
            foreach ($all_keys as $key) {
                if (preg_match('/^field_updatelocal_(.+)$/',$key, $match)) {
                    // if we have a field to update it from
                    // and it must be updated 'onlogin' we
                    // update it on cron
                    if ( !empty($this->config->{'field_map_'.$match[1]})
                         and $this->config->{$match[0]} === 'onlogin') {
                        array_push($updatekeys, $match[1]); // the actual key name
                    }
                }
            }
            // print_r($all_keys); print_r($updatekeys);
            unset($all_keys); unset($key);

        } else {
            print "No updates to be done\n";
        }
        if ( $do_updates and !empty($updatekeys) ) { // run updates only if relevant
            $users = get_records_sql("SELECT u.username, u.id
                                      FROM {$CFG->prefix}user u
                                      WHERE u.deleted=0 AND u.auth='ldap'");
            if (!empty($users)) {
                print "User entries to update: ". count($users). "\n";

                $sitecontext = get_context_instance(CONTEXT_SYSTEM);
                if (!empty($this->config->creators) and !empty($this->config->memberattribute)
                  and $roles = get_roles_with_capability('moodle/legacy:coursecreator', CAP_ALLOW)) {
                    $creatorrole = array_shift($roles);      // We can only use one, let's use the first one
                } else {
                    $creatorrole = false;
                }

                begin_sql();
                $xcount = 0;
                $maxxcount = 100;

                foreach ($users as $user) {
                    echo "\t"; print_string('auth_dbupdatinguser', 'auth', array($user->username, $user->id));
                    if (!$this->update_user_record(addslashes($user->username), $updatekeys)) {
                        echo " - ".get_string('skipped');
                    }
                    echo "\n";
                    $xcount++;

                    // update course creators if needed
                    if ($creatorrole !== false) {
                        if ($this->iscreator($user->username)) {
                            role_assign($creatorrole->id, $user->id, 0, $sitecontext->id, 0, 0, 0, 'ldap');
                        } else {
                            role_unassign($creatorrole->id, $user->id, 0, $sitecontext->id, 'ldap');
                        }
                    }

                    if ($xcount++ > $maxxcount) {
                        commit_sql();
                        begin_sql();
                        $xcount = 0;
                    }
                }
                commit_sql();
                unset($users); // free mem
            }
        } else { // end do updates
            print "No updates to be done\n";
        }

/// User Additions
        // find users missing in DB that are in LDAP
        // note that get_records_sql wants at least 2 fields returned,
        // and gives me a nifty object I don't want.
        // note: we do not care about deleted accounts anymore, this feature was replaced by suspending to nologin auth plugin
        $sql = "SELECT e.username, e.username
                FROM $temptable e LEFT JOIN {$CFG->prefix}user u ON e.username = u.username
                WHERE u.id IS NULL";
        $add_users = get_records_sql($sql); // get rid of the fat

        if (!empty($add_users)) {
            print "User entries to add: ". count($add_users). "\n";

            $sitecontext = get_context_instance(CONTEXT_SYSTEM);
            if (!empty($this->config->creators) and !empty($this->config->memberattribute)
              and $roles = get_roles_with_capability('moodle/legacy:coursecreator', CAP_ALLOW)) {
                $creatorrole = array_shift($roles);      // We can only use one, let's use the first one
            } else {
                $creatorrole = false;
            }

            begin_sql();
            foreach ($add_users as $user) {
                $user = $this->get_userinfo_asobj(addslashes($user->username));

                // prep a few params
                $user->modified   = time();
                $user->confirmed  = 1;
                $user->auth       = 'ldap';
                $user->mnethostid = $CFG->mnet_localhost_id;
                // get_userinfo_asobj() might have replaced $user->username with the value
                // from the LDAP server (which can be mixed-case). Make sure it's lowercase
                $user->username = trim(moodle_strtolower($user->username));
                if (empty($user->lang)) {
                    $user->lang = $CFG->lang;
                }

                $user = addslashes_recursive($user);

                if ($id = insert_record('user',$user)) {
                    echo "\t"; print_string('auth_dbinsertuser', 'auth', array(stripslashes($user->username), $id)); echo "\n";
                    $userobj = $this->update_user_record($user->username);
                    if (!empty($this->config->forcechangepassword)) {
                        set_user_preference('auth_forcepasswordchange', 1, $userobj->id);
                    }
                } else {
                    echo "\t"; print_string('auth_dbinsertusererror', 'auth', $user->username); echo "\n";
                }

                // add course creators if needed
                if ($creatorrole !== false and $this->iscreator(stripslashes($user->username))) {
                    role_assign($creatorrole->id, $user->id, 0, $sitecontext->id, 0, 0, 0, 'ldap');
                }
            }
            commit_sql();
            unset($add_users); // free mem
        } else {
            print "No users to be added\n";
        }
        $this->ldap_close();
        return true;
    }

    /**
     * Update a local user record from an external source.
     * This is a lighter version of the one in moodlelib -- won't do
     * expensive ops such as enrolment.
     *
     * If you don't pass $updatekeys, there is a performance hit and
     * values removed from LDAP won't be removed from moodle.
     *
     * @param string $username username (with system magic quotes)
     */
    function update_user_record($username, $updatekeys = false) {
        global $CFG;

        //just in case check text case
        $username = trim(moodle_strtolower($username));

        // get the current user record
        $user = get_record('user', 'username', $username, 'mnethostid', $CFG->mnet_localhost_id);
        if (empty($user)) { // trouble
            error_log("Cannot update non-existent user: ".stripslashes($username));
            print_error('auth_dbusernotexist','auth','',$username);
            die;
        }

        // Protect the userid from being overwritten
        $userid = $user->id;

        if ($newinfo = $this->get_userinfo($username)) {
            $newinfo = truncate_userinfo($newinfo);

            if (empty($updatekeys)) { // all keys? this does not support removing values
                $updatekeys = array_keys($newinfo);
            }

            foreach ($updatekeys as $key) {
                if (isset($newinfo[$key])) {
                    $value = $newinfo[$key];
                } else {
                    $value = '';
                }

                if (!empty($this->config->{'field_updatelocal_' . $key})) {
                    if ($user->{$key} != $value) { // only update if it's changed
                        set_field('user', $key, addslashes($value), 'id', $userid);
                    }
                }
            }
        } else {
            return false;
        }
        return get_record_select('user', "id = $userid AND deleted = 0");
    }

    /**
     * Bulk insert in SQL's temp table
     * @param array $users is an array of usernames
     */
    function ldap_bulk_insert($users, $temptable) {

        // bulk insert -- superfast with $bulk_insert_records
        $sql = 'INSERT INTO ' . $temptable . ' (username) VALUES ';
        // make those values safe
        $users = addslashes_recursive($users);
        // join and quote the whole lot
        $sql = $sql . "('" . implode("'),('", $users) . "')";
        print "\t+ " . count($users) . " users\n";
        execute_sql($sql, false);
    }


    /**
     * Activates (enables) user in external db so user can login to external db
     *
     * @param mixed $username    username (with system magic quotes)
     * @return boolen result
     */
    function user_activate($username) {
        $textlib = textlib_get_instance();
        $extusername = $textlib->convert(stripslashes($username), 'utf-8', $this->config->ldapencoding);

        $ldapconnection = $this->ldap_connect();

        $userdn = $this->ldap_find_userdn($ldapconnection, $extusername);
        switch ($this->config->user_type)  {
            case 'edir':
                $newinfo['loginDisabled']="FALSE";
                break;
            case 'ad':
                // We need to unset the ACCOUNTDISABLE bit in the
                // userAccountControl attribute ( see
                // http://support.microsoft.com/kb/305144 )
                $sr = ldap_read($ldapconnection, $userdn, '(objectClass=*)',
                                array('userAccountControl'));
                $info = ldap_get_entries($ldapconnection, $sr);
                $newinfo['userAccountControl'] = $info[0]['userAccountControl'][0]
                                                 & (~AUTH_AD_ACCOUNTDISABLE);
                break;
            default:
                error ('auth: ldap user_activate() does not support selected usertype:"'.$this->config->user_type.'" (..yet)');
        }
        $result = ldap_modify($ldapconnection, $userdn, $newinfo);
        $this->ldap_close();
        return $result;
    }

    /**
     * Disables user in external db so user can't login to external db
     *
     * @param mixed $username    username
     * @return boolean result
     */
/*    function user_disable($username) {
        $textlib = textlib_get_instance();
        $extusername = $textlib->convert(stripslashes($username), 'utf-8', $this->config->ldapencoding);

        $ldapconnection = $this->ldap_connect();

        $userdn = $this->ldap_find_userdn($ldapconnection, $extusername);
        switch ($this->config->user_type)  {
            case 'edir':
                $newinfo['loginDisabled']="TRUE";
                break;
            case 'ad':
                // We need to set the ACCOUNTDISABLE bit in the
                // userAccountControl attribute ( see
                // http://support.microsoft.com/kb/305144 )
                $sr = ldap_read($ldapconnection, $userdn, '(objectClass=*)',
                                array('userAccountControl'));
                $info = auth_ldap_get_entries($ldapconnection, $sr);
                $newinfo['userAccountControl'] = $info[0]['userAccountControl'][0]
                                                 | AUTH_AD_ACCOUNTDISABLE;
                break;
            default:
                error ('auth: ldap user_disable() does not support selected usertype (..yet)');
        }
        $result = ldap_modify($ldapconnection, $userdn, $newinfo);
        $this->ldap_close();
        return $result;
    }*/

    /**
     * Returns true if user should be coursecreator.
     *
     * @param mixed $username    username (without system magic quotes)
     * @return boolean result
     */
    function iscreator($username) {
        if (empty($this->config->creators) or empty($this->config->memberattribute)) {
            return null;
        }

        $textlib = textlib_get_instance();
        $extusername = $textlib->convert($username, 'utf-8', $this->config->ldapencoding);

        return (boolean)$this->ldap_isgroupmember($extusername, $this->config->creators);
    }

    /**
     * Called when the user record is updated.
     * Modifies user in external database. It takes olduser (before changes) and newuser (after changes)
     * conpares information saved modified information to external db.
     *
     * @param mixed $olduser     Userobject before modifications    (without system magic quotes)
     * @param mixed $newuser     Userobject new modified userobject (without system magic quotes)
     * @return boolean result
     *
     */
    function user_update($olduser, $newuser) {

        global $USER;

        if (isset($olduser->username) and isset($newuser->username) and $olduser->username != $newuser->username) {
            error_log("ERROR:User renaming not allowed in LDAP");
            return false;
        }

        if (isset($olduser->auth) and $olduser->auth != 'ldap') {
            return true; // just change auth and skip update
        }

        $attrmap = $this->ldap_attributes();

        // Before doing anything else, make sure really need to update anything
        // in the external LDAP server.
        $update_external = false;
        foreach ($attrmap as $key => $ldapkeys) {
            if (!empty($this->config->{'field_updateremote_'.$key})) {
                $update_external = true;
                break;
            }
        }
        if (!$update_external) {
            return true;
        }

        $textlib = textlib_get_instance();
        $extoldusername = $textlib->convert($olduser->username, 'utf-8', $this->config->ldapencoding);

        $ldapconnection = $this->ldap_connect();

        $search_attribs = array();

        foreach ($attrmap as $key => $values) {
            if (!is_array($values)) {
                $values = array($values);
            }
            foreach ($values as $value) {
                if (!in_array($value, $search_attribs)) {
                    array_push($search_attribs, $value);
                }
            }
        }

        $user_dn = $this->ldap_find_userdn($ldapconnection, $extoldusername);

        $user_info_result = ldap_read($ldapconnection, $user_dn,
                                $this->config->objectclass, $search_attribs);

        if ($user_info_result) {

            $user_entry = $this->ldap_get_entries($ldapconnection, $user_info_result);
            if (empty($user_entry)) {
                $error = 'ldap: Could not find user while updating externally. '.
                         'Details follow: search base: \''.$user_dn.'\'; search filter: \''.
                         $this->config->objectclass.'\'; search attributes: ';
                foreach ($search_attribs as $attrib) {
                    $error .= $attrib.' ';
                }
                error_log($error);
                return false; // old user not found!
            } else if (count($user_entry) > 1) {
                error_log('ldap: Strange! More than one user record found in ldap. Only using the first one.');
                return false;
            }
            $user_entry = $user_entry[0];

            //error_log(var_export($user_entry) . 'fpp' );

            foreach ($attrmap as $key => $ldapkeys) {
                // only process if the moodle field ($key) has changed and we
                // are set to update LDAP with it
                if (isset($olduser->$key) and isset($newuser->$key)
                  and $olduser->$key !== $newuser->$key
                  and !empty($this->config->{'field_updateremote_'. $key})) {
                    // for ldap values that could be in more than one
                    // ldap key, we will do our best to match
                    // where they came from
                    $ambiguous = true;
                    $changed   = false;
                    if (!is_array($ldapkeys)) {
                        $ldapkeys = array($ldapkeys);
                    }
                    if (count($ldapkeys) < 2) {
                        $ambiguous = false;
                    }

                    $nuvalue = $textlib->convert($newuser->$key, 'utf-8', $this->config->ldapencoding);
                    empty($nuvalue) ? $nuvalue = array() : $nuvalue;
                    $ouvalue = $textlib->convert($olduser->$key, 'utf-8', $this->config->ldapencoding);

                    foreach ($ldapkeys as $ldapkey) {
                        $ldapkey   = $ldapkey;
                        $ldapvalue = $user_entry[$ldapkey][0];
                        if (!$ambiguous) {
                            // skip update if the values already match
                            if ($nuvalue !== $ldapvalue) {
                                //this might fail due to schema validation
                                if (@ldap_modify($ldapconnection, $user_dn, array($ldapkey => $nuvalue))) {
                                    continue;
                                } else {
                                    error_log('Error updating LDAP record. Error code: '
                                      . ldap_errno($ldapconnection) . '; Error string : '
                                      . ldap_err2str(ldap_errno($ldapconnection))
                                      . "\nKey ($key) - old moodle value: '$ouvalue' new value: '$nuvalue'");
                                    continue;
                                }
                            }
                        } else {
                            // ambiguous
                            // value empty before in Moodle (and LDAP) - use 1st ldap candidate field
                            // no need to guess
                            if ($ouvalue === '') { // value empty before - use 1st ldap candidate
                                //this might fail due to schema validation
                                if (@ldap_modify($ldapconnection, $user_dn, array($ldapkey => $nuvalue))) {
                                    $changed = true;
                                    continue;
                                } else {
                                    error_log('Error updating LDAP record. Error code: '
                                      . ldap_errno($ldapconnection) . '; Error string : '
                                      . ldap_err2str(ldap_errno($ldapconnection))
                                      . "\nKey ($key) - old moodle value: '$ouvalue' new value: '$nuvalue'");
                                    continue;
                                }
                            }

                            // we found which ldap key to update!
                            if ($ouvalue !== '' and $ouvalue === $ldapvalue ) {
                                //this might fail due to schema validation
                                if (@ldap_modify($ldapconnection, $user_dn, array($ldapkey => $nuvalue))) {
                                    $changed = true;
                                    continue;
                                } else {
                                    error_log('Error updating LDAP record. Error code: '
                                      . ldap_errno($ldapconnection) . '; Error string : '
                                      . ldap_err2str(ldap_errno($ldapconnection))
                                      . "\nKey ($key) - old moodle value: '$ouvalue' new value: '$nuvalue'");
                                    continue;
                                }
                            }
                        }
                    }

                    if ($ambiguous and !$changed) {
                        error_log("Failed to update LDAP with ambiguous field $key".
                                  "  old moodle value: '" . $ouvalue .
                                  "' new value '" . $nuvalue );
                    }
                }
            }
        } else {
            error_log("ERROR:No user found in LDAP");
            $this->ldap_close();
            return false;
        }

        $this->ldap_close();

        return true;

    }

    /**
     * changes userpassword in external db
     *
     * called when the user password is updated.
     * changes userpassword in external db
     *
     * @param  object  $user        User table object  (with system magic quotes)
     * @param  string  $newpassword Plaintext password (with system magic quotes)
     * @return boolean result
     *
     */
    function user_update_password($user, $newpassword) {
    /// called when the user password is updated -- it assumes it is called by an admin
    /// or that you've otherwise checked the user's credentials
    /// IMPORTANT: $newpassword must be cleartext, not crypted/md5'ed

        global $USER;
        $result = false;
        $username = $user->username;

        $textlib = textlib_get_instance();
        $extusername = $textlib->convert(stripslashes($username), 'utf-8', $this->config->ldapencoding);
        $extpassword = $textlib->convert(stripslashes($newpassword), 'utf-8', $this->config->ldapencoding);

        switch ($this->config->passtype) {
            case 'md5':
                $extpassword = '{MD5}' . base64_encode(pack('H*', md5($extpassword)));
                break;
            case 'sha1':
                $extpassword = '{SHA}' . base64_encode(pack('H*', sha1($extpassword)));
                break;
            case 'plaintext':
            default:
                break; // plaintext
        }

        $ldapconnection = $this->ldap_connect();

        $user_dn = $this->ldap_find_userdn($ldapconnection, $extusername);

        if (!$user_dn) {
            error_log('LDAP Error in user_update_password(). No DN for: ' . stripslashes($user->username));
            return false;
        }

        switch ($this->config->user_type) {
            case 'edir':
                //Change password
                $result = ldap_modify($ldapconnection, $user_dn, array('userPassword' => $extpassword));
                if (!$result) {
                    error_log('LDAP Error in user_update_password(). Error code: '
                              . ldap_errno($ldapconnection) . '; Error string : '
                              . ldap_err2str(ldap_errno($ldapconnection)));
                }
                //Update password expiration time, grace logins count
                $search_attribs = array($this->config->expireattr, 'passwordExpirationInterval','loginGraceLimit' );
                $sr = ldap_read($ldapconnection, $user_dn, '(objectClass=*)', $search_attribs);
                if ($sr)  {
                    $info=$this->ldap_get_entries($ldapconnection, $sr);
                    $newattrs = array();
                    if (!empty($info[0][$this->config->expireattr][0])) {
                        //Set expiration time only if passwordExpirationInterval is defined
                        if (!empty($info[0]['passwordExpirationInterval'][0])) {
                           $expirationtime = time() + $info[0]['passwordExpirationInterval'][0];
                           $ldapexpirationtime = $this->ldap_unix2expirationtime($expirationtime);
                           $newattrs['passwordExpirationTime'] = $ldapexpirationtime;
                        }

                        //set gracelogin count
                        if (!empty($info[0]['loginGraceLimit'][0])) {
                           $newattrs['loginGraceRemaining']= $info[0]['loginGraceLimit'][0];
                        }

                        //Store attribute changes to ldap
                        $result = ldap_modify($ldapconnection, $user_dn, $newattrs);
                        if (!$result) {
                           error_log('LDAP Error in user_update_password() when modifying expirationtime and/or gracelogins. Error code: '
                                     . ldap_errno($ldapconnection) . '; Error string : '
                                     . ldap_err2str(ldap_errno($ldapconnection)));
                        }
                    }
                }
                else {
                    error_log('LDAP Error in user_update_password() when reading password expiration time. Error code: '
                              . ldap_errno($ldapconnection) . '; Error string : '
                              . ldap_err2str(ldap_errno($ldapconnection)));
                }
                break;

            case 'ad':
                // Passwords in Active Directory must be encoded as Unicode
                // strings (UCS-2 Little Endian format) and surrounded with
                // double quotes. See http://support.microsoft.com/?kbid=269190
                if (!function_exists('mb_convert_encoding')) {
                    error_log ('You need the mbstring extension to change passwords in Active Directory');
                    return false;
                }
                $extpassword = mb_convert_encoding('"'.$extpassword.'"', "UCS-2LE", $this->config->ldapencoding);
                $result = ldap_modify($ldapconnection, $user_dn, array('unicodePwd' => $extpassword));
                if (!$result) {
                    error_log('LDAP Error in user_update_password(). Error code: '
                              . ldap_errno($ldapconnection) . '; Error string : '
                              . ldap_err2str(ldap_errno($ldapconnection)));
                }
                break;

            default:
                $usedconnection = &$ldapconnection;
                // send ldap the password in cleartext, it will md5 it itself
                $result = ldap_modify($ldapconnection, $user_dn, array('userPassword' => $extpassword));
                if (!$result) {
                    error_log('LDAP Error in user_update_password(). Error code: '
                        . ldap_errno($ldapconnection) . '; Error string : '
                        . ldap_err2str(ldap_errno($ldapconnection)));
                }

        }

        $this->ldap_close();
        return $result;
    }

    //PRIVATE FUNCTIONS starts
    //private functions are named as ldap_*

    /**
     * returns predefined usertypes
     *
     * @return array of predefined usertypes
     */
    function ldap_suppported_usertypes() {
        $types = array();
        $types['edir']='Novell Edirectory';
        $types['rfc2307']='posixAccount (rfc2307)';
        $types['rfc2307bis']='posixAccount (rfc2307bis)';
        $types['samba']='sambaSamAccount (v.3.0.7)';
        $types['ad']='MS ActiveDirectory';
        $types['default']=get_string('default');
        return $types;
    }


    /**
     * Initializes needed variables for ldap-module
     *
     * Uses names defined in ldap_supported_usertypes.
     * $default is first defined as:
     * $default['pseudoname'] = array(
     *                      'typename1' => 'value',
     *                      'typename2' => 'value'
     *                      ....
     *                      );
     *
     * @return array of default values
     */
    function ldap_getdefaults() {
        $default['objectclass'] = array(
                            'edir' => 'User',
                            'rfc2307' => 'posixAccount',
                            'rfc2307bis' => 'posixAccount',
                            'samba' => 'sambaSamAccount',
                            'ad' => 'user',
                            'default' => '*'
                            );
        $default['user_attribute'] = array(
                            'edir' => 'cn',
                            'rfc2307' => 'uid',
                            'rfc2307bis' => 'uid',
                            'samba' => 'uid',
                            'ad' => 'cn',
                            'default' => 'cn'
                            );
        $default['memberattribute'] = array(
                            'edir' => 'member',
                            'rfc2307' => 'member',
                            'rfc2307bis' => 'member',
                            'samba' => 'member',
                            'ad' => 'member',
                            'default' => 'member'
                            );
        $default['memberattribute_isdn'] = array(
                            'edir' => '1',
                            'rfc2307' => '0',
                            'rfc2307bis' => '1',
                            'samba' => '0', //is this right?
                            'ad' => '1',
                            'default' => '0'
                            );
        $default['expireattr'] = array (
                            'edir' => 'passwordExpirationTime',
                            'rfc2307' => 'shadowExpire',
                            'rfc2307bis' => 'shadowExpire',
                            'samba' => '', //No support yet
                            'ad' => 'pwdLastSet',
                            'default' => ''
                            );
        return $default;
    }

    /**
     * return binaryfields of selected usertype
     *
     *
     * @return array
     */
    function ldap_getbinaryfields () {
        $binaryfields = array (
                            'edir' => array('guid'),
                            'rfc2307' => array(),
                            'rfc2307bis' => array(),
                            'samba' => array(),
                            'ad' => array(),
                            'default' => array()
                            );
        if (!empty($this->config->user_type)) {
            return $binaryfields[$this->config->user_type];
        }
        else {
            return $binaryfields['default'];
        }
    }

    function ldap_isbinary ($field) {
        if (empty($field)) {
            return false;
        }
        return array_search($field, $this->ldap_getbinaryfields());
    }

    /**
     * take expirationtime and return it as unixseconds
     *
     * takes expriration timestamp as readed from ldap
     * returns it as unix seconds
     * depends on $this->config->user_type variable
     *
     * @param mixed time   Time stamp readed from ldap as it is.
     * @param string $ldapconnection Just needed for Active Directory.
     * @param string $user_dn User distinguished name for the user we are checking password expiration (just needed for Active Directory).
     * @return timestamp
     */
    function ldap_expirationtime2unix ($time, $ldapconnection, $user_dn) {
        $result = false;
        switch ($this->config->user_type) {
            case 'edir':
                $yr=substr($time,0,4);
                $mo=substr($time,4,2);
                $dt=substr($time,6,2);
                $hr=substr($time,8,2);
                $min=substr($time,10,2);
                $sec=substr($time,12,2);
                $result = mktime($hr,$min,$sec,$mo,$dt,$yr);
                break;
            case 'rfc2307':
            case 'rfc2307bis':
                $result = $time * DAYSECS; //The shadowExpire contains the number of DAYS between 01/01/1970 and the actual expiration date
                break;
            case 'ad':
                $result = $this->ldap_get_ad_pwdexpire($time, $ldapconnection, $user_dn);
                break;
            default:
                print_error('auth_ldap_usertypeundefined', 'auth');
        }
        return $result;
    }

    /**
     * takes unixtime and return it formated for storing in ldap
     *
     * @param integer unix time stamp
     */
    function ldap_unix2expirationtime($time) {
        $result = false;
        switch ($this->config->user_type) {
            case 'edir':
                $result=date('YmdHis', $time).'Z';
                break;
            case 'rfc2307':
            case 'rfc2307bis':
                $result = $time ; //Already in correct format
                break;
            default:
                print_error('auth_ldap_usertypeundefined2', 'auth');
        }
        return $result;

    }

    /**
     * checks if user belong to specific group(s)
     * or is in a subtree.
     *
     * Returns true if user belongs group in grupdns string OR
     * if the DN of the user is in a subtree pf the DN provided
     * as "group"
     *
     * @param mixed $username    username
     * @param mixed $groupdns    string of group dn separated by ;
     *
     */
    function ldap_isgroupmember($extusername='', $groupdns='') {
    // Takes username and groupdn(s) , separated by ;
    // Returns true if user is member of any given groups

        $ldapconnection = $this->ldap_connect();

        if (empty($extusername) or empty($groupdns)) {
            return false;
            }

        if ($this->config->memberattribute_isdn) {
            $memberuser = $this->ldap_find_userdn($ldapconnection, $extusername);
        } else {
            $memberuser = $extusername;
        }

        if (empty($memberuser)) {
            return false;
        }

        $groups = explode(";",$groupdns);

        $result = false;
        foreach ($groups as $group) {
            $group = trim($group);
            if (empty($group)) {
                continue;
            }

            // check cheaply if the user's DN sits in a subtree
            // of the "group" DN provided. Granted, this isn't
            // a proper LDAP group, but it's a popular usage.
            if (strpos(strrev($memberuser), strrev($group))===0) {
                $result = true;
                break;
            }

            //echo "Checking group $group for member $username\n";
            $search = ldap_read($ldapconnection, $group,  '('.$this->config->memberattribute.'='.$this->filter_addslashes($memberuser).')', array($this->config->memberattribute));
            if (!empty($search) and ldap_count_entries($ldapconnection, $search)) {
                $info = $this->ldap_get_entries($ldapconnection, $search);

                if (count($info) > 0 ) {
                    // user is member of group
                    $result = true;
                    break;
                }
          }
        }

        return $result;

    }

    /**
     * connects to ldap server
     *
     * Tries connect to specified ldap servers.
     * Returns connection result or error.
     *
     * @return connection result
     */
    function ldap_connect($binddn='',$bindpwd='') {
        // Cache ldap connections (they are expensive to set up
        // and can drain the TCP/IP ressources on the server if we 
        // are syncing a lot of users (as we try to open a new connection
        // to get the user details). This is the least invasive way
        // to reuse existing connections without greater code surgery.
        if(!empty($this->ldapconnection)) {
            $this->ldapconns++;
            return $this->ldapconnection;
        }

        //Select bind password, With empty values use
        //ldap_bind_* variables or anonymous bind if ldap_bind_* are empty
        if ($binddn == '' and $bindpwd == '') {
            if (!empty($this->config->bind_dn)) {
               $binddn = $this->config->bind_dn;
            }
            if (!empty($this->config->bind_pw)) {
               $bindpwd = $this->config->bind_pw;
            }
        }

        $urls = explode(";",$this->config->host_url);

        foreach ($urls as $server) {
            $server = trim($server);
            if (empty($server)) {
                continue;
            }

            $connresult = ldap_connect($server);
            //ldap_connect returns ALWAYS true

            if (!empty($this->config->version)) {
                ldap_set_option($connresult, LDAP_OPT_PROTOCOL_VERSION, $this->config->version);
            }

            // Fix MDL-10921
            if ($this->config->user_type == 'ad') {
                 ldap_set_option($connresult, LDAP_OPT_REFERRALS, 0);
            }

            if (!empty($binddn)) {
                //bind with search-user
                //$debuginfo .= 'Using bind user'.$binddn.'and password:'.$bindpwd;
                $bindresult=ldap_bind($connresult, $binddn,$bindpwd);
            }
            else {
                //bind anonymously
                $bindresult=@ldap_bind($connresult);
            }

            if (!empty($this->config->opt_deref)) {
                ldap_set_option($connresult, LDAP_OPT_DEREF, $this->config->opt_deref);
            }

            if ($bindresult) {
		// Set the connection counter so we can call PHP's ldap_close()
		// when we call $this->ldap_close() for the last 'open' connection.
                $this->ldapconns = 1;  
                $this->ldapconnection = $connresult;
                return $connresult;
            }

            $debuginfo .= "<br/>Server: '$server' <br/> Connection: '$connresult'<br/> Bind result: '$bindresult'</br>";
        }

        //If any of servers are alive we have already returned connection
        print_error('auth_ldap_noconnect_all','auth','', $debuginfo);
        return false;
    }

    /**
     * disconnects from a ldap server
     *
     */
    function ldap_close() {
        $this->ldapconns--;
        if($this->ldapconns == 0) {
            @ldap_close($this->ldapconnection);
            unset($this->ldapconnection);
        }
    }

    /**
     * retuns dn of username
     *
     * Search specified contexts for username and return user dn
     * like: cn=username,ou=suborg,o=org
     *
     * @param mixed $ldapconnection  $ldapconnection result
     * @param mixed $username username (external encoding no slashes)
     *
     */

    function ldap_find_userdn ($ldapconnection, $extusername) {

        //default return value
        $ldap_user_dn = FALSE;

        //get all contexts and look for first matching user
        $ldap_contexts = explode(";",$this->config->contexts);

        if (!empty($this->config->create_context)) {
          array_push($ldap_contexts, $this->config->create_context);
        }

        foreach ($ldap_contexts as $context) {

            $context = trim($context);
            if (empty($context)) {
                continue;
            }

            if ($this->config->search_sub) {
                //use ldap_search to find first user from subtree
                $ldap_result = ldap_search($ldapconnection, $context, "(".$this->config->user_attribute."=".$this->filter_addslashes($extusername).")",array($this->config->user_attribute));

            }
            else {
                //search only in this context
                $ldap_result = ldap_list($ldapconnection, $context, "(".$this->config->user_attribute."=".$this->filter_addslashes($extusername).")",array($this->config->user_attribute));
            }

            $entry = ldap_first_entry($ldapconnection,$ldap_result);

            if ($entry) {
                $ldap_user_dn = ldap_get_dn($ldapconnection, $entry);
                break ;
            }
        }

        return $ldap_user_dn;
    }

    /**
     * retuns user attribute mappings between moodle and ldap
     *
     * @return array
     */

    function ldap_attributes () {
        $moodleattributes = array();
        foreach ($this->userfields as $field) {
            if (!empty($this->config->{"field_map_$field"})) {
                $moodleattributes[$field] = $this->config->{"field_map_$field"};
                if (preg_match('/,/',$moodleattributes[$field])) {
                    $moodleattributes[$field] = explode(',', $moodleattributes[$field]); // split ?
                }
            }
        }
        $moodleattributes['username'] = $this->config->user_attribute;
        return $moodleattributes;
    }

    /**
     * return all usernames from ldap
     *
     * @return array
     */

    function ldap_get_userlist($filter="*") {
    /// returns all users from ldap servers
        $fresult = array();

        $ldapconnection = $this->ldap_connect();

        if ($filter=="*") {
           $filter = '(&('.$this->config->user_attribute.'=*)'.$this->config->objectclass.')';
        }

        $contexts = explode(";",$this->config->contexts);

        if (!empty($this->config->create_context)) {
              array_push($contexts, $this->config->create_context);
        }

        foreach ($contexts as $context) {

            $context = trim($context);
            if (empty($context)) {
                continue;
            }

            if ($this->config->search_sub) {
                //use ldap_search to find first user from subtree
                $ldap_result = ldap_search($ldapconnection, $context,$filter,array($this->config->user_attribute));
            }
            else {
                //search only in this context
                $ldap_result = ldap_list($ldapconnection, $context,
                                         $filter,
                                         array($this->config->user_attribute));
            }

            $users = $this->ldap_get_entries($ldapconnection, $ldap_result);

            //add found users to list
            for ($i=0;$i<count($users);$i++) {
                array_push($fresult, ($users[$i][$this->config->user_attribute][0]) );
            }
        }

        return $fresult;
    }

    /**
     * return entries from ldap
     *
     * Returns values like ldap_get_entries but is
     * binary compatible and return all attributes as array
     *
     * @return array ldap-entries
     */

    function ldap_get_entries($conn, $searchresult) {
    //Returns values like ldap_get_entries but is
    //binary compatible
        $i=0;
        $fresult=array();
        $entry = ldap_first_entry($conn, $searchresult);
        do {
            $attributes = @ldap_get_attributes($conn, $entry);
            for ($j=0; $j<$attributes['count']; $j++) {
                $values = ldap_get_values_len($conn, $entry,$attributes[$j]);
                if (is_array($values)) {
                $fresult[$i][$attributes[$j]] = $values;
                }
                else {
                    $fresult[$i][$attributes[$j]] = array($values);
                }
            }
            $i++;
        }
        while ($entry = @ldap_next_entry($conn, $entry));
        //were done
        return ($fresult);
    }

    function prevent_local_passwords() {
        return !empty($this->config->preventpassindb);
    }

    /**
     * Returns true if this authentication plugin is 'internal'.
     *
     * @return bool
     */
    function is_internal() {
        return false;
    }

    /**
     * Returns true if this authentication plugin can change the user's
     * password.
     *
     * @return bool
     */
    function can_change_password() {
        return !empty($this->config->stdchangepassword) or !empty($this->config->changepasswordurl);
    }

    /**
     * Returns the URL for changing the user's pw, or empty if the default can
     * be used.
     *
     * @return string url
     */
    function change_password_url() {
        if (empty($this->config->stdchangepassword)) {
            return $this->config->changepasswordurl;
        } else {
            return '';
        }
    }

    /**
     * Will get called before the login page is shown, if NTLM SSO
     * is enabled, and the user is in the right network, we'll redirect
     * to the magic NTLM page for SSO...
     *
     */
    function loginpage_hook() {
        global $CFG, $SESSION;

        // HTTPS is potentially required
        httpsrequired();
 
        if (($_SERVER['REQUEST_METHOD'] === 'GET'         // Only on initial GET of loginpage
                || ($_SERVER['REQUEST_METHOD'] === 'POST'
                   && (get_referer() != strip_querystring(qualified_me()))))
                                                           // Or when POSTed from another place
                                                           // See MDL-14071
           && !empty($this->config->ntlmsso_enabled)     // SSO enabled
           && !empty($this->config->ntlmsso_subnet)      // have a subnet to test for
           && empty($_GET['authldap_skipntlmsso'])       // haven't failed it yet
           && (isguestuser() || !isloggedin())           // guestuser or not-logged-in users
            && address_in_subnet(getremoteaddr(), $this->config->ntlmsso_subnet)) {

            // First, let's remember where we were trying to get to before we got here
            if (empty($SESSION->wantsurl)) {
                $SESSION->wantsurl = (array_key_exists('HTTP_REFERER', $_SERVER) &&
                                      $_SERVER['HTTP_REFERER'] != $CFG->wwwroot &&
                                      $_SERVER['HTTP_REFERER'] != $CFG->wwwroot.'/' &&
                                      $_SERVER['HTTP_REFERER'] != $CFG->httpswwwroot.'/login/' &&
                                      $_SERVER['HTTP_REFERER'] != $CFG->httpswwwroot.'/login/index.php')
                    ? $_SERVER['HTTP_REFERER'] : NULL;
            }

            // Now start the whole NTLM machinery.
            if(!empty($this->config->ntlmsso_ie_fastpath)) {
                // Shortcut for IE browsers: skip the attempt page at all
                if(check_browser_version('MSIE')) {
                    $sesskey = sesskey();
                    redirect($CFG->wwwroot.'/auth/ldap/ntlmsso_magic.php?sesskey='.$sesskey);
                } else {
                    redirect($CFG->httpswwwroot.'/login/index.php?authldap_skipntlmsso=1');
                }
            } else {
                redirect($CFG->wwwroot.'/auth/ldap/ntlmsso_attempt.php');
            }
        }
 
        // No NTLM SSO, Use the normal login page instead.

        // If $SESSION->wantsurl is empty and we have a 'Referer:' header, the login
        // page insists on redirecting us to that page after user validation. If
        // we clicked on the redirect link at the ntlmsso_finish.php page instead
        // of waiting for the redirection to happen, then we have a 'Referer:' header
        // we don't want to use at all. As we can't get rid of it, just point
        // $SESSION->wantsurl to $CFG->wwwroot (after all, we came from there).
        if (empty($SESSION->wantsurl)
            && (get_referer() == $CFG->httpswwwroot.'/auth/ldap/ntlmsso_finish.php')) {

            $SESSION->wantsurl = $CFG->wwwroot;
        }
    }

    /**
     * To be called from a page running under NTLM's
     * "Integrated Windows Authentication". 
     *
     * If successful, it will set a special "cookie" (not an HTTP cookie!) 
     * in cache_flags under the "auth/ldap/ntlmsess" "plugin" and return true.
     * The "cookie" will be picked up by ntlmsso_finish() to complete the
     * process.
     *
     * On failure it will return false for the caller to display an appropriate
     * error message (probably saying that Integrated Windows Auth isn't enabled!)
     *
     * NOTE that this code will execute under the OS user credentials, 
     * so we MUST avoid dealing with files -- such as session files.
     * (The caller should set $nomoodlecookie before including config.php)
     *
     */
    function ntlmsso_magic($sesskey) {
        if (isset($_SERVER['REMOTE_USER']) && !empty($_SERVER['REMOTE_USER'])) {

            // HTTP __headers__ seem to be sent in ISO-8859-1 encoding
            // (according to my reading of RFC-1945, RFC-2616 and RFC-2617 and
            // my local tests), so we need to convert the REMOTE_USER value
            // (i.e., what we got from the HTTP WWW-Authenticate header) into UTF-8
            $textlib = textlib_get_instance();
            $username = $textlib->convert($_SERVER['REMOTE_USER'], 'iso-8859-1', 'utf-8');

            $username = substr(strrchr($username, '\\'), 1); //strip domain info
            $username = moodle_strtolower($username); //compatibility hack
            set_cache_flag('auth/ldap/ntlmsess', $sesskey, $username, AUTH_NTLMTIMEOUT);
            return true;
        }
        return false;
    }

    /**
     * Find the session set by ntlmsso_magic(), validate it and 
     * call authenticate_user_login() to authenticate the user through
     * the auth machinery.
     * 
     * It is complemented by a similar check in user_login().
     * 
     * If it succeeds, it never returns. 
     *
     */
    function ntlmsso_finish() {
        global $CFG, $USER, $SESSION;

        $key = sesskey();
        $cf = get_cache_flags('auth/ldap/ntlmsess');
        if (!isset($cf[$key]) || $cf[$key] === '') {
            return false;
        }
        $username   = $cf[$key];
        // Here we want to trigger the whole authentication machinery
        // to make sure no step is bypassed...
        $user = authenticate_user_login($username, $key);
        if ($user) {
            add_to_log(SITEID, 'user', 'login', "view.php?id=$USER->id&course=".SITEID,
                       $user->id, 0, $user->id);
            $USER = complete_user_login($user);

            // Cleanup the key to prevent reuse...
            // and to allow re-logins with normal credentials
            unset_cache_flag('auth/ldap/ntlmsess', $key);

            /// Redirection
            if (user_not_fully_set_up($USER)) {
                $urltogo = $CFG->wwwroot.'/user/edit.php';
                // We don't delete $SESSION->wantsurl yet, so we get there later
            } else if (isset($SESSION->wantsurl) and (strpos($SESSION->wantsurl, $CFG->wwwroot) === 0)) {
                $urltogo = $SESSION->wantsurl;    /// Because it's an address in this site
                unset($SESSION->wantsurl);
            } else {
                // no wantsurl stored or external - go to homepage
                $urltogo = $CFG->wwwroot.'/';
                unset($SESSION->wantsurl);
            }
            redirect($urltogo);
        }
        // Should never reach here.
        return false;
    }    

    /**
     * Sync roles for this user
     *
     * @param $user object user object (without system magic quotes)
     */
    function sync_roles($user) {
        $iscreator = $this->iscreator($user->username);
        if ($iscreator === null) {
            return; //nothing to sync - creators not configured
        }

        if ($roles = get_roles_with_capability('moodle/legacy:coursecreator', CAP_ALLOW)) {
            $creatorrole = array_shift($roles);      // We can only use one, let's use the first one
            $systemcontext = get_context_instance(CONTEXT_SYSTEM);

            if ($iscreator) { // Following calls will not create duplicates
                role_assign($creatorrole->id, $user->id, 0, $systemcontext->id, 0, 0, 0, 'ldap');
            } else {
                //unassign only if previously assigned by this plugin!
                role_unassign($creatorrole->id, $user->id, 0, $systemcontext->id, 'ldap');
            }
        }
    }

    /**
     * Prints a form for configuring this authentication plugin.
     *
     * This function is called from admin/auth.php, and outputs a full page with
     * a form for configuring this plugin.
     *
     * @param array $page An object containing all the data for this page.
     */
    function config_form($config, $err, $user_fields) {
        include 'config.html';
    }

    /**
     * Processes and stores configuration data for this authentication plugin.
     */
    function process_config($config) {
        // set to defaults if undefined
        if (!isset($config->host_url))
            { $config->host_url = ''; }
        if (empty($config->ldapencoding))
            { $config->ldapencoding = 'utf-8'; }
        if (!isset($config->contexts))
            { $config->contexts = ''; }
        if (!isset($config->user_type))
            { $config->user_type = 'default'; }
        if (!isset($config->user_attribute))
            { $config->user_attribute = ''; }
        if (!isset($config->search_sub))
            { $config->search_sub = ''; }
        if (!isset($config->opt_deref))
            { $config->opt_deref = ''; }
        if (!isset($config->preventpassindb))
            { $config->preventpassindb = 0; }
        if (!isset($config->bind_dn))
            {$config->bind_dn = ''; }
        if (!isset($config->bind_pw))
            {$config->bind_pw = ''; }
        if (!isset($config->version))
            {$config->version = '2'; }
        if (!isset($config->objectclass))
            {$config->objectclass = ''; }
        if (!isset($config->memberattribute))
            {$config->memberattribute = ''; }
        if (!isset($config->memberattribute_isdn))
            {$config->memberattribute_isdn = ''; }
        if (!isset($config->creators))
            {$config->creators = ''; }
        if (!isset($config->create_context))
            {$config->create_context = ''; }
        if (!isset($config->expiration))
            {$config->expiration = ''; }
        if (!isset($config->expiration_warning))
            {$config->expiration_warning = '10'; }
        if (!isset($config->expireattr))
            {$config->expireattr = ''; }
        if (!isset($config->gracelogins))
            {$config->gracelogins = ''; }
        if (!isset($config->graceattr))
            {$config->graceattr = ''; }
        if (!isset($config->auth_user_create))
            {$config->auth_user_create = ''; }
        if (!isset($config->forcechangepassword))
            {$config->forcechangepassword = 0; }
        if (!isset($config->stdchangepassword))
            {$config->stdchangepassword = 0; }
        if (!isset($config->passtype))
            {$config->passtype = 'plaintext'; }
        if (!isset($config->changepasswordurl))
            {$config->changepasswordurl = ''; }
        if (!isset($config->removeuser))
            {$config->removeuser = 0; }
        if (!isset($config->ntlmsso_enabled))
            {$config->ntlmsso_enabled = 0; }
        if (!isset($config->ntlmsso_subnet))
            {$config->ntlmsso_subnet = ''; }
        if (!isset($config->ntlmsso_ie_fastpath))
            {$config->ntlmsso_ie_fastpath = 0; }

        // save settings
        set_config('host_url', $config->host_url, 'auth/ldap');
        set_config('ldapencoding', $config->ldapencoding, 'auth/ldap');
        set_config('host_url', $config->host_url, 'auth/ldap');
        set_config('contexts', $config->contexts, 'auth/ldap');
        set_config('user_type', $config->user_type, 'auth/ldap');
        set_config('user_attribute', $config->user_attribute, 'auth/ldap');
        set_config('search_sub', $config->search_sub, 'auth/ldap');
        set_config('opt_deref', $config->opt_deref, 'auth/ldap');
        set_config('preventpassindb', $config->preventpassindb, 'auth/ldap');
        set_config('bind_dn', $config->bind_dn, 'auth/ldap');
        set_config('bind_pw', $config->bind_pw, 'auth/ldap');
        set_config('version', $config->version, 'auth/ldap');
        set_config('objectclass', trim($config->objectclass), 'auth/ldap');
        set_config('memberattribute', $config->memberattribute, 'auth/ldap');
        set_config('memberattribute_isdn', $config->memberattribute_isdn, 'auth/ldap');
        set_config('creators', $config->creators, 'auth/ldap');
        set_config('create_context', $config->create_context, 'auth/ldap');
        set_config('expiration', $config->expiration, 'auth/ldap');
        set_config('expiration_warning', $config->expiration_warning, 'auth/ldap');
        set_config('expireattr', $config->expireattr, 'auth/ldap');
        set_config('gracelogins', $config->gracelogins, 'auth/ldap');
        set_config('graceattr', $config->graceattr, 'auth/ldap');
        set_config('auth_user_create', $config->auth_user_create, 'auth/ldap');
        set_config('forcechangepassword', $config->forcechangepassword, 'auth/ldap');
        set_config('stdchangepassword', $config->stdchangepassword, 'auth/ldap');
        set_config('passtype', $config->passtype, 'auth/ldap');
        set_config('changepasswordurl', $config->changepasswordurl, 'auth/ldap');
        set_config('removeuser', $config->removeuser, 'auth/ldap');
        set_config('ntlmsso_enabled', (int)$config->ntlmsso_enabled, 'auth/ldap');
        set_config('ntlmsso_subnet', $config->ntlmsso_subnet, 'auth/ldap');
        set_config('ntlmsso_ie_fastpath', (int)$config->ntlmsso_ie_fastpath, 'auth/ldap');

        return true;
    }

    /**
     * Quote control characters in texts used in ldap filters - see RFC 4515/2254
     *
     * @param string
     */
    function filter_addslashes($text) {
        $text = str_replace('\\', '\\5c', $text);
        $text = str_replace(array('*',    '(',    ')',    "\0"),
                            array('\\2a', '\\28', '\\29', '\\00'), $text);
        return $text;
    }

    /**
     * The order of the special characters in these arrays _IS IMPORTANT_.
     * Make sure '\\5C' (and '\\') are the first elements of the arrays.
     * Otherwise we'll double replace '\' with '\5C' which is Bad(tm)
     */ 
    var $LDAP_DN_QUOTED_SPECIAL_CHARS = array('\\5c','\\20','\\22','\\23','\\2b','\\2c','\\3b','\\3c','\\3d','\\3e','\\00');
    var $LDAP_DN_SPECIAL_CHARS        = array('\\',  ' ',   '"',   '#',   '+',   ',',   ';',   '<',   '=',   '>',   "\0");

    /**
     * Quote control characters in distinguished names used in ldap - See RFC 4514/2253
     *
     * @param string
     * @return string
     */
    function ldap_addslashes($text) {
        $text = str_replace ($this->LDAP_DN_SPECIAL_CHARS,
                             $this->LDAP_DN_QUOTED_SPECIAL_CHARS,
                             $text);
        return $text;
    }

    /**
     * Get password expiration time for a given user from Active Directory
     *
     * @param string $pwdlastset The time last time we changed the password.
     * @param resource $lcapconn The open LDAP connection.
     * @param string $user_dn The distinguished name of the user we are checking.
     *
     * @return string $unixtime
     */
    function ldap_get_ad_pwdexpire($pwdlastset, $ldapconn, $user_dn){
        define ('ROOTDSE', '');
        // UF_DONT_EXPIRE_PASSWD value taken from MSDN directly
        define ('UF_DONT_EXPIRE_PASSWD', 0x00010000);

        global $CFG;

        if (!function_exists('bcsub')) {
            error_log ('You need the BCMath extension to use grace logins with Active Directory');
            return 0;
        }

        // If UF_DONT_EXPIRE_PASSWD flag is set in user's
        // userAccountControl attribute, the password doesn't expire.
        $sr = ldap_read($ldapconn, $user_dn, '(objectClass=*)',
                        array('userAccountControl'));
        if (!$sr) {
            error_log("ldap: error getting userAccountControl for $user_dn");
            // don't expire password, as we are not sure it has to be
            // expired or not.
            return 0;
        }

        $info = $this->ldap_get_entries($ldapconn, $sr);
        $useraccountcontrol = $info[0]['userAccountControl'][0];
        if ($useraccountcontrol & UF_DONT_EXPIRE_PASSWD) {
            // password doesn't expire.
            return 0;
        }

        // If pwdLastSet is zero, the user must change his/her password now
        // (unless UF_DONT_EXPIRE_PASSWD flag is set, but we already
        // tested this above)
        if ($pwdlastset === '0') {
            // password has expired
            return -1;
        }

        // ----------------------------------------------------------------
        // Password expiration time in Active Directory is the composition of
        // two values:
        //
        //   - User's pwdLastSet attribute, that stores the last time
        //     the password was changed.
        //
        //   - Domain's maxPwdAge attribute, that sets how long
        //     passwords last in this domain.
        //
        // We already have the first value (passed in as a parameter). We
        // need to get the second one. As we don't know the domain DN, we
        // have to query rootDSE's defaultNamingContext attribute to get
        // it. Then we have to query that DN's maxPwdAge attribute to get
        // the real value.
        //
        // Once we have both values, we just need to combine them. But MS
        // chose to use a different base and unit for time measurements.
        // So we need to convert the values to Unix timestamps (see
        // details below).
        // ----------------------------------------------------------------

        $sr = ldap_read($ldapconn, ROOTDSE, '(objectClass=*)',
                        array('defaultNamingContext'));
        if (!$sr) {
            error_log("ldap: error querying rootDSE for Active Directory");
            return 0;
        }

        $info = $this->ldap_get_entries($ldapconn, $sr);
        $domaindn = $info[0]['defaultNamingContext'][0];

        $sr = ldap_read ($ldapconn, $domaindn, '(objectClass=*)',
                         array('maxPwdAge'));
        $info = $this->ldap_get_entries($ldapconn, $sr);
        $maxpwdage = $info[0]['maxPwdAge'][0];

        // ----------------------------------------------------------------
        // MSDN says that "pwdLastSet contains the number of 100 nanosecond
        // intervals since January 1, 1601 (UTC), stored in a 64 bit integer".
        //
        // According to Perl's Date::Manip, the number of seconds between
        // this date and Unix epoch is 11644473600. So we have to
        // substract this value to calculate a Unix time, once we have
        // scaled pwdLastSet to seconds. This is the script used to
        // calculate the value shown above:
        //
        //    #!/usr/bin/perl -w
        //
        //    use Date::Manip;
        //
        //    $date1 = ParseDate ("160101010000 UTC");
        //    $date2 = ParseDate ("197001010000 UTC");
        //    $delta = DateCalc($date1, $date2, \$err);
        //    $secs = Delta_Format($delta, 0, "%st");
        //    print "$secs \n";
        //
        // MSDN also says that "maxPwdAge is stored as a large integer that
        // represents the number of 100 nanosecond intervals from the time
        // the password was set before the password expires." We also need
        // to scale this to seconds. Bear in mind that this value is stored
        // as a _negative_ quantity (at least in my AD domain).
        //
        // As a last remark, if the low 32 bits of maxPwdAge are equal to 0,
        // the maximum password age in the domain is set to 0, which means
        // passwords do not expire (see
        // http://msdn2.microsoft.com/en-us/library/ms974598.aspx)
        //
        // As the quantities involved are too big for PHP integers, we
        // need to use BCMath functions to work with arbitrary precision
        // numbers.
        // ----------------------------------------------------------------


        // If the low order 32 bits are 0, then passwords do not expire in
        // the domain. Just do '$maxpwdage mod 2^32' and check the result
        // (2^32 = 4294967296)
        if (bcmod ($maxpwdage, 4294967296) === '0') {
            return 0;
        }

        // Add up pwdLastSet and maxPwdAge to get password expiration
        // time, in MS time units. Remember maxPwdAge is stored as a
        // _negative_ quantity, so we need to substract it in fact.
        $pwdexpire = bcsub ($pwdlastset, $maxpwdage);

        // Scale the result to convert it to Unix time units and return
        // that value.
        return bcsub( bcdiv($pwdexpire, '10000000'), '11644473600');
    }

}

?>
