access.php

<?php

/**
 * ownCloud – LDAP Access
 *
 * @author Arthur Schiwon
 * @copyright 2012, 2013 Arthur Schiwon blizzz@owncloud.com
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU AFFERO GENERAL PUBLIC LICENSE
 * License as published by the Free Software Foundation; either
 * version 3 of the License, or any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU AFFERO GENERAL PUBLIC LICENSE for more details.
 *
 * You should have received a copy of the GNU Affero General Public
 * License along with this library.  If not, see <http://www.gnu.org/licenses/>.
 *
 */

namespace OCA\user_ldap\lib;

/**
 * Class Access
 * @package OCA\user_ldap\lib
 */
class Access extends LDAPUtility implements user\IUserTools {
	/**
	 * @var \OCA\user_ldap\lib\Connection
	 */
	public $connection;
	public $userManager;
	//never ever check this var directly, always use getPagedSearchResultState
	protected $pagedSearchedSuccessful;

	/**
	 * @var string[] $cookies an array of returned Paged Result cookies
	 */
	protected $cookies = array();

	/**
	 * @var string $lastCookie the last cookie returned from a Paged Results
	 * operation, defaults to an empty string
	 */
	protected $lastCookie = '';

	public function __construct(Connection $connection, ILDAPWrapper $ldap,
		user\Manager $userManager) {
		parent::__construct($ldap);
		$this->connection = $connection;
		$this->userManager = $userManager;
		$this->userManager->setLdapAccess($this);
	}

	/**
	 * @return bool
	 */
	private function checkConnection() {
		return ($this->connection instanceof Connection);
	}

	/**
	 * returns the Connection instance
	 * @return \OCA\user_ldap\lib\Connection
	 */
	public function getConnection() {
		return $this->connection;
	}

	/**
	 * reads a given attribute for an LDAP record identified by a DN
	 * @param string $dn the record in question
	 * @param string $attr the attribute that shall be retrieved
	 *        if empty, just check the record's existence
	 * @param string $filter
	 * @return array|false an array of values on success or an empty
	 *          array if $attr is empty, false otherwise
	 */
	public function readAttribute($dn, $attr, $filter = 'objectClass=*') {
		if(!$this->checkConnection()) {
			\OCP\Util::writeLog('user_ldap',
				'No LDAP Connector assigned, access impossible for readAttribute.',
				\OCP\Util::WARN);
			return false;
		}
		$cr = $this->connection->getConnectionResource();
		if(!$this->ldap->isResource($cr)) {
			//LDAP not available
			\OCP\Util::writeLog('user_ldap', 'LDAP resource not available.', \OCP\Util::DEBUG);
			return false;
		}
		//Cancel possibly running Paged Results operation, otherwise we run in
		//LDAP protocol errors
		$this->abandonPagedSearch();
		// openLDAP requires that we init a new Paged Search. Not needed by AD,
		// but does not hurt either.
		$this->initPagedSearch($filter, array($dn), array($attr), 1, 0);
		$dn = $this->DNasBaseParameter($dn);
		$rr = @$this->ldap->read($cr, $dn, $filter, array($attr));
		if(!$this->ldap->isResource($rr)) {
			if(!empty($attr)) {
				//do not throw this message on userExists check, irritates
				\OCP\Util::writeLog('user_ldap', 'readAttribute failed for DN '.$dn, \OCP\Util::DEBUG);
			}
			//in case an error occurs , e.g. object does not exist
			return false;
		}
		if (empty($attr)) {
			\OCP\Util::writeLog('user_ldap', 'readAttribute: '.$dn.' found', \OCP\Util::DEBUG);
			return array();
		}
		$er = $this->ldap->firstEntry($cr, $rr);
		if(!$this->ldap->isResource($er)) {
			//did not match the filter, return false
			return false;
		}
		//LDAP attributes are not case sensitive
		$result = \OCP\Util::mb_array_change_key_case(
				$this->ldap->getAttributes($cr, $er), MB_CASE_LOWER, 'UTF-8');
		$attr = mb_strtolower($attr, 'UTF-8');

		if(isset($result[$attr]) && $result[$attr]['count'] > 0) {
			$values = array();
			for($i=0;$i<$result[$attr]['count'];$i++) {
				if($this->resemblesDN($attr)) {
					$values[] = $this->sanitizeDN($result[$attr][$i]);
				} elseif(strtolower($attr) === 'objectguid' || strtolower($attr) === 'guid') {
					$values[] = $this->convertObjectGUID2Str($result[$attr][$i]);
				} else {
					$values[] = $result[$attr][$i];
				}
			}
			return $values;
		}
		\OCP\Util::writeLog('user_ldap', 'Requested attribute '.$attr.' not found for '.$dn, \OCP\Util::DEBUG);
		return false;
	}

	/**
	 * checks whether the given attributes value is probably a DN
	 * @param string $attr the attribute in question
	 * @return boolean if so true, otherwise false
	 */
	private function resemblesDN($attr) {
		$resemblingAttributes = array(
			'dn',
			'uniquemember',
			'member'
		);
		return in_array($attr, $resemblingAttributes);
	}

	/**
	 * checks whether the given string is probably a DN
	 * @param string $string
	 * @return boolean
	 */
	public function stringResemblesDN($string) {
		$r = $this->ldap->explodeDN($string, 0);
		// if exploding a DN succeeds and does not end up in
		// an empty array except for $r[count] being 0.
		return (is_array($r) && count($r) > 1);
	}

	/**
	 * sanitizes a DN received from the LDAP server
	 * @param array $dn the DN in question
	 * @return array the sanitized DN
	 */
	private function sanitizeDN($dn) {
		//treating multiple base DNs
		if(is_array($dn)) {
			$result = array();
			foreach($dn as $singleDN) {
				$result[] = $this->sanitizeDN($singleDN);
			}
			return $result;
		}

		//OID sometimes gives back DNs with whitespace after the comma
		// a la "uid=foo, cn=bar, dn=..." We need to tackle this!
		$dn = preg_replace('/([^\\\]),(\s+)/u', '\1,', $dn);

		//make comparisons and everything work
		$dn = mb_strtolower($dn, 'UTF-8');

		//escape DN values according to RFC 2253 – this is already done by ldap_explode_dn
		//to use the DN in search filters, \ needs to be escaped to \5c additionally
		//to use them in bases, we convert them back to simple backslashes in readAttribute()
		$replacements = array(
			'\,' => '\5c2C',
			'\=' => '\5c3D',
			'\+' => '\5c2B',
			'\<' => '\5c3C',
			'\>' => '\5c3E',
			'\;' => '\5c3B',
			'\"' => '\5c22',
			'\#' => '\5c23',
			'('  => '\28',
			')'  => '\29',
			'*'  => '\2A',
		);
		$dn = str_replace(array_keys($replacements), array_values($replacements), $dn);

		return $dn;
	}

	/**
	 * returns a DN-string that is cleaned from not domain parts, e.g.
	 * cn=foo,cn=bar,dc=foobar,dc=server,dc=org
	 * becomes dc=foobar,dc=server,dc=org
	 * @param string $dn
	 * @return string
	 */
	public function getDomainDNFromDN($dn) {
		$allParts = $this->ldap->explodeDN($dn, 0);
		if($allParts === false) {
			//not a valid DN
			return '';
		}
		$domainParts = array();
		$dcFound = false;
		foreach($allParts as $part) {
			if(!$dcFound && strpos($part, 'dc=') === 0) {
				$dcFound = true;
			}
			if($dcFound) {
				$domainParts[] = $part;
			}
		}
		$domainDN = implode(',', $domainParts);
		return $domainDN;
	}

	/**
	 * gives back the database table for the query
	 * @param bool $isUser
	 * @return string
	 */
	private function getMapTable($isUser) {
		if($isUser) {
			return '*PREFIX*ldap_user_mapping';
		} else {
			return '*PREFIX*ldap_group_mapping';
		}
	}

	/**
	 * returns the LDAP DN for the given internal ownCloud name of the group
	 * @param string $name the ownCloud name in question
	 * @return string with the LDAP DN on success, otherwise false
	 */
	public function groupname2dn($name) {
		$dn = $this->ocname2dn($name, false);

		if($dn) {
			return $dn;
		}

		return false;
	}

	/**
	 * returns the LDAP DN for the given internal ownCloud name of the user
	 * @param string $name the ownCloud name in question
	 * @return string with the LDAP DN on success, otherwise false
	 */
	public function username2dn($name) {
		$dn = $this->ocname2dn($name, true);
		//Check whether the DN belongs to the Base, to avoid issues on multi-
		//server setups
		if($dn && $this->isDNPartOfBase($dn, $this->connection->ldapBaseUsers)) {
			return $dn;
		}

		return false;
	}

	/**
	 * returns the LDAP DN for the given internal ownCloud name
	 * @param string $name the ownCloud name in question
	 * @param boolean $isUser is it a user? otherwise group
	 * @return string with the LDAP DN on success, otherwise false
	 */
	private function ocname2dn($name, $isUser) {
		$table = $this->getMapTable($isUser);

		$query = \OCP\DB::prepare('
			SELECT `ldap_dn`
			FROM `'.$table.'`
			WHERE `owncloud_name` = ?
		');

		$record = $query->execute(array($name))->fetchOne();
		return $record;
	}

	/**
	 * returns the internal ownCloud name for the given LDAP DN of the group, false on DN outside of search DN or failure
	 * @param string $dn the dn of the group object
	 * @param string $ldapName optional, the display name of the object
	 * @return string with the name to use in ownCloud, false on DN outside of search DN
	 */
	public function dn2groupname($dn, $ldapName = null) {
		//To avoid bypassing the base DN settings under certain circumstances
		//with the group support, check whether the provided DN matches one of
		//the given Bases
		if(!$this->isDNPartOfBase($dn, $this->connection->ldapBaseGroups)) {
			return false;
		}

		return $this->dn2ocname($dn, $ldapName, false);
	}

	/**
	 * returns the internal ownCloud name for the given LDAP DN of the user, false on DN outside of search DN or failure
	 * @param string $dn the dn of the user object
	 * @param string $ldapName optional, the display name of the object
	 * @return string with with the name to use in ownCloud
	 */
	public function dn2username($dn, $ldapName = null) {
		//To avoid bypassing the base DN settings under certain circumstances
		//with the group support, check whether the provided DN matches one of
		//the given Bases
		if(!$this->isDNPartOfBase($dn, $this->connection->ldapBaseUsers)) {
			return false;
		}

		return $this->dn2ocname($dn, $ldapName, true);
	}

	/**
	 * returns an internal ownCloud name for the given LDAP DN, false on DN outside of search DN
	 * @param string $dn the dn of the user object
	 * @param string $ldapName optional, the display name of the object
	 * @param bool $isUser optional, whether it is a user object (otherwise group assumed)
	 * @return string with with the name to use in ownCloud
	 */
	public function dn2ocname($dn, $ldapName = null, $isUser = true) {
		$table = $this->getMapTable($isUser);
		if($isUser) {
			$fncFindMappedName = 'findMappedUser';
			$nameAttribute = $this->connection->ldapUserDisplayName;
		} else {
			$fncFindMappedName = 'findMappedGroup';
			$nameAttribute = $this->connection->ldapGroupDisplayName;
		}

		//let's try to retrieve the ownCloud name from the mappings table
		$ocName = $this->$fncFindMappedName($dn);
		if($ocName) {
			return $ocName;
		}

		//second try: get the UUID and check if it is known. Then, update the DN and return the name.
		$uuid = $this->getUUID($dn, $isUser);
		if($uuid) {
			$query = \OCP\DB::prepare('
				SELECT `owncloud_name`
				FROM `'.$table.'`
				WHERE `directory_uuid` = ?
			');
			$component = $query->execute(array($uuid))->fetchOne();
			if($component) {
				$query = \OCP\DB::prepare('
					UPDATE `'.$table.'`
					SET `ldap_dn` = ?
					WHERE `directory_uuid` = ?
				');
				$query->execute(array($dn, $uuid));
				return $component;
			}
		} else {
			//If the UUID can't be detected something is foul.
			\OCP\Util::writeLog('user_ldap', 'Cannot determine UUID for '.$dn.'. Skipping.', \OCP\Util::INFO);
			return false;
		}

		if(is_null($ldapName)) {
			$ldapName = $this->readAttribute($dn, $nameAttribute);
			if(!isset($ldapName[0]) && empty($ldapName[0])) {
				\OCP\Util::writeLog('user_ldap', 'No or empty name for '.$dn.'.', \OCP\Util::INFO);
				return false;
			}
			$ldapName = $ldapName[0];
		}

		if($isUser) {
			$usernameAttribute = $this->connection->ldapExpertUsernameAttr;
			if(!emptY($usernameAttribute)) {
				$username = $this->readAttribute($dn, $usernameAttribute);
				$username = $username[0];
			} else {
				$username = $uuid;
			}
			$intName = $this->sanitizeUsername($username);
		} else {
			$intName = $ldapName;
		}

		//a new user/group! Add it only if it doesn't conflict with other backend's users or existing groups
		//disabling Cache is required to avoid that the new user is cached as not-existing in fooExists check
		//NOTE: mind, disabling cache affects only this instance! Using it
		// outside of core user management will still cache the user as non-existing.
		$originalTTL = $this->connection->ldapCacheTTL;
		$this->connection->setConfiguration(array('ldapCacheTTL' => 0));
		if(($isUser && !\OCP\User::userExists($intName))
			|| (!$isUser && !\OC_Group::groupExists($intName))) {
			if($this->mapComponent($dn, $intName, $isUser)) {
				$this->connection->setConfiguration(array('ldapCacheTTL' => $originalTTL));
				return $intName;
			}
		}
		$this->connection->setConfiguration(array('ldapCacheTTL' => $originalTTL));

		$altName = $this->createAltInternalOwnCloudName($intName, $isUser);
		if($this->mapComponent($dn, $altName, $isUser)) {
			return $altName;
		}

		//if everything else did not help..
		\OCP\Util::writeLog('user_ldap', 'Could not create unique name for '.$dn.'.', \OCP\Util::INFO);
		return false;
	}

	/**
	 * gives back the user names as they are used ownClod internally
	 * @param array $ldapUsers an array with the ldap Users result in style of array ( array ('dn' => foo, 'uid' => bar), ... )
	 * @return array an array with the user names to use in ownCloud
	 *
	 * gives back the user names as they are used ownClod internally
	 */
	public function ownCloudUserNames($ldapUsers) {
		return $this->ldap2ownCloudNames($ldapUsers, true);
	}

	/**
	 * gives back the group names as they are used ownClod internally
	 * @param array $ldapGroups an array with the ldap Groups result in style of array ( array ('dn' => foo, 'cn' => bar), ... )
	 * @return array an array with the group names to use in ownCloud
	 *
	 * gives back the group names as they are used ownClod internally
	 */
	public function ownCloudGroupNames($ldapGroups) {
		return $this->ldap2ownCloudNames($ldapGroups, false);
	}

	/**
	 * @param string $dn
	 * @return bool|string
	 */
	private function findMappedUser($dn) {
		static $query = null;
		if(is_null($query)) {
			$query = \OCP\DB::prepare('
				SELECT `owncloud_name`
				FROM `'.$this->getMapTable(true).'`
				WHERE `ldap_dn` = ?'
			);
		}
		$res = $query->execute(array($dn))->fetchOne();
		if($res) {
			return  $res;
		}
		return false;
	}

	/**
	 * @param string $dn
	 * @return bool|string
	 */
	private function findMappedGroup($dn) {
		static $query = null;
		if(is_null($query)) {
			$query = \OCP\DB::prepare('
					SELECT `owncloud_name`
					FROM `'.$this->getMapTable(false).'`
					WHERE `ldap_dn` = ?'
			);
		}
		$res = $query->execute(array($dn))->fetchOne();
		if($res) {
			return  $res;
		}
		return false;
	}

	/**
	 * @param array $ldapObjects
	 * @param bool $isUsers
	 * @return array
	 */
	private function ldap2ownCloudNames($ldapObjects, $isUsers) {
		if($isUsers) {
			$nameAttribute = $this->connection->ldapUserDisplayName;
		} else {
			$nameAttribute = $this->connection->ldapGroupDisplayName;
		}
		$ownCloudNames = array();

		foreach($ldapObjects as $ldapObject) {
			$nameByLDAP = isset($ldapObject[$nameAttribute]) ? $ldapObject[$nameAttribute] : null;
			$ocName = $this->dn2ocname($ldapObject['dn'], $nameByLDAP, $isUsers);
			if($ocName) {
				$ownCloudNames[] = $ocName;
				if($isUsers) {
					//cache the user names so it does not need to be retrieved
					//again later (e.g. sharing dialogue).
					$this->cacheUserExists($ocName);
					$this->cacheUserDisplayName($ocName, $nameByLDAP);
				}
			}
			continue;
		}
		return $ownCloudNames;
	}

	/**
	 * caches a user as existing
	 * @param string $ocName the internal ownCloud username
	 */
	public function cacheUserExists($ocName) {
		$this->connection->writeToCache('userExists'.$ocName, true);
	}

	/**
	 * caches the user display name
	 * @param string $ocName the internal ownCloud username
	 * @param string $displayName the display name
	 */
	public function cacheUserDisplayName($ocName, $displayName) {
		$cacheKeyTrunk = 'getDisplayName';
		$this->connection->writeToCache($cacheKeyTrunk.$ocName, $displayName);
	}

	/**
	 * creates a unique name for internal ownCloud use for users. Don't call it directly.
	 * @param string $name the display name of the object
	 * @return string with with the name to use in ownCloud or false if unsuccessful
	 *
	 * Instead of using this method directly, call
	 * createAltInternalOwnCloudName($name, true)
	 */
	private function _createAltInternalOwnCloudNameForUsers($name) {
		$attempts = 0;
		//while loop is just a precaution. If a name is not generated within
		//20 attempts, something else is very wrong. Avoids infinite loop.
		while($attempts < 20){
			$altName = $name . '_' . rand(1000,9999);
			if(!\OCP\User::userExists($altName)) {
				return $altName;
			}
			$attempts++;
		}
		return false;
	}

	/**
	 * creates a unique name for internal ownCloud use for groups. Don't call it directly.
	 * @param string $name the display name of the object
	 * @return string with with the name to use in ownCloud or false if unsuccessful.
	 *
	 * Instead of using this method directly, call
	 * createAltInternalOwnCloudName($name, false)
	 *
	 * Group names are also used as display names, so we do a sequential
	 * numbering, e.g. Developers_42 when there are 41 other groups called
	 * "Developers"
	 */
	private function _createAltInternalOwnCloudNameForGroups($name) {
		$query = \OCP\DB::prepare('
			SELECT `owncloud_name`
			FROM `'.$this->getMapTable(false).'`
			WHERE `owncloud_name` LIKE ?
		');

		$usedNames = array();
		$res = $query->execute(array($name.'_%'));
		while($row = $res->fetchRow()) {
			$usedNames[] = $row['owncloud_name'];
		}
		if(!($usedNames) || count($usedNames) === 0) {
			$lastNo = 1; //will become name_2
		} else {
			natsort($usedNames);
			$lastName = array_pop($usedNames);
			$lastNo = intval(substr($lastName, strrpos($lastName, '_') + 1));
		}
		$altName = $name.'_'.strval($lastNo+1);
		unset($usedNames);

		$attempts = 1;
		while($attempts < 21){
			// Check to be really sure it is unique
			// while loop is just a precaution. If a name is not generated within
			// 20 attempts, something else is very wrong. Avoids infinite loop.
			if(!\OC_Group::groupExists($altName)) {
				return $altName;
			}
			$altName = $name . '_' . ($lastNo + $attempts);
			$attempts++;
		}
		return false;
	}

	/**
	 * creates a unique name for internal ownCloud use.
	 * @param string $name the display name of the object
	 * @param boolean $isUser whether name should be created for a user (true) or a group (false)
	 * @return string with with the name to use in ownCloud or false if unsuccessful
	 */
	private function createAltInternalOwnCloudName($name, $isUser) {
		$originalTTL = $this->connection->ldapCacheTTL;
		$this->connection->setConfiguration(array('ldapCacheTTL' => 0));
		if($isUser) {
			$altName = $this->_createAltInternalOwnCloudNameForUsers($name);
		} else {
			$altName = $this->_createAltInternalOwnCloudNameForGroups($name);
		}
		$this->connection->setConfiguration(array('ldapCacheTTL' => $originalTTL));

		return $altName;
	}

	/**
	 * retrieves all known groups from the mappings table
	 * @return array with the results
	 *
	 * retrieves all known groups from the mappings table
	 */
	private function mappedGroups() {
		return $this->mappedComponents(false);
	}

	/**
	 * retrieves all known users from the mappings table
	 * @return array with the results
	 *
	 * retrieves all known users from the mappings table
	 */
	private function mappedUsers() {
		return $this->mappedComponents(true);
	}

	/**
	 * @param boolean $isUsers
	 * @return array
	 */
	private function mappedComponents($isUsers) {
		$table = $this->getMapTable($isUsers);

		$query = \OCP\DB::prepare('
			SELECT `ldap_dn`, `owncloud_name`
			FROM `'. $table . '`'
		);

		return $query->execute()->fetchAll();
	}

	/**
	 * inserts a new user or group into the mappings table
	 * @param string $dn the record in question
	 * @param string $ocName the name to use in ownCloud
	 * @param bool $isUser is it a user or a group?
	 * @return bool true on success, false otherwise
	 *
	 * inserts a new user or group into the mappings table
	 */
	private function mapComponent($dn, $ocName, $isUser = true) {
		$table = $this->getMapTable($isUser);

		$sqlAdjustment = '';
		$dbType = \OCP\Config::getSystemValue('dbtype');
		if($dbType === 'mysql' || $dbType == 'oci') {
			$sqlAdjustment = 'FROM DUAL';
		}

		$insert = \OCP\DB::prepare('
			INSERT INTO `'.$table.'` (`ldap_dn`, `owncloud_name`, `directory_uuid`)
				SELECT ?,?,?
				'.$sqlAdjustment.'
				WHERE NOT EXISTS (
					SELECT 1
					FROM `'.$table.'`
					WHERE `ldap_dn` = ?
						OR `owncloud_name` = ?)
		');

		//feed the DB
		$insRows = $insert->execute(array($dn, $ocName,
										  $this->getUUID($dn, $isUser), $dn,
										  $ocName));

		if(\OCP\DB::isError($insRows)) {
			return false;
		}

		if($insRows === 0) {
			return false;
		}

		if($isUser) {
			//make sure that email address is retrieved prior to login, so user
			//will be notified when something is shared with him
			$this->userManager->get($ocName)->update();
		}

		return true;
	}

	/**
	 * @param string $filter
	 * @param string|string[] $attr
	 * @param int $limit
	 * @param int $offset
	 * @return array
	 */
	public function fetchListOfUsers($filter, $attr, $limit = null, $offset = null) {
		return $this->fetchList($this->searchUsers($filter, $attr, $limit, $offset), (count($attr) > 1));
	}

	/**
	 * @param string $filter
	 * @param string|string[] $attr
	 * @param int $limit
	 * @param int $offset
	 * @return array
	 */
	public function fetchListOfGroups($filter, $attr, $limit = null, $offset = null) {
		return $this->fetchList($this->searchGroups($filter, $attr, $limit, $offset), (count($attr) > 1));
	}

	/**
	 * @param array $list
	 * @param bool $manyAttributes
	 * @return array
	 */
	private function fetchList($list, $manyAttributes) {
		if(is_array($list)) {
			if($manyAttributes) {
				return $list;
			} else {
				return array_unique($list, SORT_LOCALE_STRING);
			}
		}

		//error cause actually, maybe throw an exception in future.
		return array();
	}

	/**
	 * executes an LDAP search, optimized for Users
	 * @param string $filter the LDAP filter for the search
	 * @param string|string[] $attr optional, when a certain attribute shall be filtered out
	 * @param integer $limit
	 * @param integer $offset
	 * @return array with the search result
	 *
	 * Executes an LDAP search
	 */
	public function searchUsers($filter, $attr = null, $limit = null, $offset = null) {
		return $this->search($filter, $this->connection->ldapBaseUsers, $attr, $limit, $offset);
	}

	/**
	 * @param string $filter
	 * @param string|string[] $attr
	 * @param int $limit
	 * @param int $offset
	 * @return false|int
	 */
	public function countUsers($filter, $attr = array('dn'), $limit = null, $offset = null) {
		return $this->count($filter, $this->connection->ldapBaseUsers, $attr, $limit, $offset);
	}

	/**
	 * executes an LDAP search, optimized for Groups
	 * @param string $filter the LDAP filter for the search
	 * @param string|string[] $attr optional, when a certain attribute shall be filtered out
	 * @param integer $limit
	 * @param integer $offset
	 * @return array with the search result
	 *
	 * Executes an LDAP search
	 */
	public function searchGroups($filter, $attr = null, $limit = null, $offset = null) {
		return $this->search($filter, $this->connection->ldapBaseGroups, $attr, $limit, $offset);
	}

	/**
	 * returns the number of available groups
	 * @param string $filter the LDAP search filter
	 * @param string[] $attr optional
	 * @param int|null $limit
	 * @param int|null $offset
	 * @return int|bool
	 */
	public function countGroups($filter, $attr = array('dn'), $limit = null, $offset = null) {
		return $this->count($filter, $this->connection->ldapBaseGroups, $attr, $limit, $offset);
	}

	/**
	 * retrieved. Results will according to the order in the array.
	 * @param int $limit optional, maximum results to be counted
	 * @param int $offset optional, a starting point
	 * @return array|false array with the search result as first value and pagedSearchOK as
	 * second | false if not successful
	 */
	private function executeSearch($filter, $base, &$attr = null, $limit = null, $offset = null) {
		if(!is_null($attr) && !is_array($attr)) {
			$attr = array(mb_strtolower($attr, 'UTF-8'));
		}

		// See if we have a resource, in case not cancel with message
		$cr = $this->connection->getConnectionResource();
		if(!$this->ldap->isResource($cr)) {
			// Seems like we didn't find any resource.
			// Return an empty array just like before.
			\OCP\Util::writeLog('user_ldap', 'Could not search, because resource is missing.', \OCP\Util::DEBUG);
			return false;
		}

		//check whether paged search should be attempted
		$pagedSearchOK = $this->initPagedSearch($filter, $base, $attr, intval($limit), $offset);

		$linkResources = array_pad(array(), count($base), $cr);
		$sr = $this->ldap->search($linkResources, $base, $filter, $attr);
		$error = $this->ldap->errno($cr);
		if(!is_array($sr) || $error !== 0) {
			\OCP\Util::writeLog('user_ldap',
				'Error when searching: '.$this->ldap->error($cr).
					' code '.$this->ldap->errno($cr),
				\OCP\Util::ERROR);
			\OCP\Util::writeLog('user_ldap', 'Attempt for Paging?  '.print_r($pagedSearchOK, true), \OCP\Util::ERROR);
			return false;
		}

		return array($sr, $pagedSearchOK);
	}

	/**
	 * processes an LDAP paged search operation
	 * @param array $sr the array containing the LDAP search resources
	 * @param string $filter the LDAP filter for the search
	 * @param array $base an array containing the LDAP subtree(s) that shall be searched
	 * @param int $iFoundItems number of results in the search operation
	 * @param int $limit maximum results to be counted
	 * @param int $offset a starting point
	 * @param bool $pagedSearchOK whether a paged search has been executed
	 * @param bool $skipHandling required for paged search when cookies to
	 * prior results need to be gained
	 * @return array|false array with the search result as first value and pagedSearchOK as
	 * second | false if not successful
	 */
	private function processPagedSearchStatus($sr, $filter, $base, $iFoundItems, $limit, $offset, $pagedSearchOK, $skipHandling) {
		if($pagedSearchOK) {
			$cr = $this->connection->getConnectionResource();
			foreach($sr as $key => $res) {
				$cookie = null;
				if($this->ldap->controlPagedResultResponse($cr, $res, $cookie)) {
					$this->setPagedResultCookie($base[$key], $filter, $limit, $offset, $cookie);
				}
			}

			//browsing through prior pages to get the cookie for the new one
			if($skipHandling) {
				return;
			}
			// if count is bigger, then the server does not support
			// paged search. Instead, he did a normal search. We set a
			// flag here, so the callee knows how to deal with it.
			if($iFoundItems <= $limit) {
				$this->pagedSearchedSuccessful = true;
			}
		} else {
			if(!is_null($limit)) {
				\OCP\Util::writeLog('user_ldap', 'Paged search was not available', \OCP\Util::INFO);
			}
		}
	}

	/**
	 * executes an LDAP search, but counts the results only
	 * @param string $filter the LDAP filter for the search
	 * @param array $base an array containing the LDAP subtree(s) that shall be searched
	 * @param string|string[] $attr optional, array, one or more attributes that shall be
	 * retrieved. Results will according to the order in the array.
	 * @param int $limit optional, maximum results to be counted
	 * @param int $offset optional, a starting point
	 * @param bool $skipHandling indicates whether the pages search operation is