Move dav app to PSR-4 (#24527)

* Move Application to correct namespace and PSR-4 it

* Move dav app to PSR-4

7 files changed, 1111 insertions, 0 deletions

diff --git a/apps/dav/lib/DAV/GroupPrincipalBackend.php b/apps/dav/lib/DAV/GroupPrincipalBackend.php
new file mode 100644
index 00000000000..e0568639784
--- /dev/null
+++ b/apps/dav/lib/DAV/GroupPrincipalBackend.php
@@ -0,0 +1,200 @@
+<?php
+/**
+ * @author Thomas Müller <thomas.mueller@tmit.eu>
+ *
+ * @copyright Copyright (c) 2016, ownCloud, Inc.
+ * @license AGPL-3.0
+ *
+ * This code is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License, version 3,
+ * as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License, version 3,
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>
+ *
+ */
+namespace OCA\DAV\DAV;
+
+use OCP\IGroup;
+use OCP\IGroupManager;
+use OCP\IUser;
+use Sabre\DAV\Exception;
+use \Sabre\DAV\PropPatch;
+use Sabre\DAVACL\PrincipalBackend\BackendInterface;
+
+class GroupPrincipalBackend implements BackendInterface {
+
+	const PRINCIPAL_PREFIX = 'principals/groups';
+
+	/** @var IGroupManager */
+	private $groupManager;
+
+	/**
+	 * @param IGroupManager $IGroupManager
+	 */
+	public function __construct(IGroupManager $IGroupManager) {
+		$this->groupManager = $IGroupManager;
+	}
+
+	/**
+	 * Returns a list of principals based on a prefix.
+	 *
+	 * This prefix will often contain something like 'principals'. You are only
+	 * expected to return principals that are in this base path.
+	 *
+	 * You are expected to return at least a 'uri' for every user, you can
+	 * return any additional properties if you wish so. Common properties are:
+	 *   {DAV:}displayname
+	 *
+	 * @param string $prefixPath
+	 * @return string[]
+	 */
+	public function getPrincipalsByPrefix($prefixPath) {
+		$principals = [];
+
+		if ($prefixPath === self::PRINCIPAL_PREFIX) {
+			foreach($this->groupManager->search('') as $user) {
+				$principals[] = $this->groupToPrincipal($user);
+			}
+		}
+
+		return $principals;
+	}
+
+	/**
+	 * Returns a specific principal, specified by it's path.
+	 * The returned structure should be the exact same as from
+	 * getPrincipalsByPrefix.
+	 *
+	 * @param string $path
+	 * @return array
+	 */
+	public function getPrincipalByPath($path) {
+		$elements = explode('/', $path);
+		if ($elements[0] !== 'principals') {
+			return null;
+		}
+		if ($elements[1] !== 'groups') {
+			return null;
+		}
+		$name = $elements[2];
+		$group = $this->groupManager->get($name);
+
+		if (!is_null($group)) {
+			return $this->groupToPrincipal($group);
+		}
+
+		return null;
+	}
+
+	/**
+	 * Returns the list of members for a group-principal
+	 *
+	 * @param string $principal
+	 * @return string[]
+	 * @throws Exception
+	 */
+	public function getGroupMemberSet($principal) {
+		$elements = explode('/', $principal);
+		if ($elements[0] !== 'principals') {
+			return [];
+		}
+		if ($elements[1] !== 'groups') {
+			return [];
+		}
+		$name = $elements[2];
+		$group = $this->groupManager->get($name);
+
+		if (is_null($group)) {
+			return [];
+		}
+
+		return array_map(function($user) {
+			return $this->userToPrincipal($user);
+		}, $group->getUsers());
+	}
+
+	/**
+	 * Returns the list of groups a principal is a member of
+	 *
+	 * @param string $principal
+	 * @return array
+	 * @throws Exception
+	 */
+	public function getGroupMembership($principal) {
+		return [];
+	}
+
+	/**
+	 * Updates the list of group members for a group principal.
+	 *
+	 * The principals should be passed as a list of uri's.
+	 *
+	 * @param string $principal
+	 * @param string[] $members
+	 * @throws Exception
+	 */
+	public function setGroupMemberSet($principal, array $members) {
+		throw new Exception('Setting members of the group is not supported yet');
+	}
+
+	/**
+	 * @param string $path
+	 * @param PropPatch $propPatch
+	 * @return int
+	 */
+	function updatePrincipal($path, PropPatch $propPatch) {
+		return 0;
+	}
+
+	/**
+	 * @param string $prefixPath
+	 * @param array $searchProperties
+	 * @param string $test
+	 * @return array
+	 */
+	function searchPrincipals($prefixPath, array $searchProperties, $test = 'allof') {
+		return [];
+	}
+
+	/**
+	 * @param string $uri
+	 * @param string $principalPrefix
+	 * @return string
+	 */
+	function findByUri($uri, $principalPrefix) {
+		return '';
+	}
+
+	/**
+	 * @param IGroup $group
+	 * @return array
+	 */
+	protected function groupToPrincipal($group) {
+		$groupId = $group->getGID();
+		$principal = [
+			'uri' => "principals/groups/$groupId",
+			'{DAV:}displayname' => $groupId,
+		];
+
+		return $principal;
+	}
+
+	/**
+	 * @param IUser $user
+	 * @return array
+	 */
+	protected function userToPrincipal($user) {
+		$principal = [
+			'uri' => 'principals/users/' . $user->getUID(),
+			'{DAV:}displayname' => $user->getDisplayName(),
+		];
+
+		return $principal;
+	}
+}
diff --git a/apps/dav/lib/DAV/Sharing/Backend.php b/apps/dav/lib/DAV/Sharing/Backend.php
new file mode 100644
index 00000000000..225b773713d
--- /dev/null
+++ b/apps/dav/lib/DAV/Sharing/Backend.php
@@ -0,0 +1,206 @@
+<?php
+/**
+ * @author Lukas Reschke <lukas@owncloud.com>
+ * @author Thomas Müller <thomas.mueller@tmit.eu>
+ *
+ * @copyright Copyright (c) 2016, ownCloud, Inc.
+ * @license AGPL-3.0
+ *
+ * This code is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License, version 3,
+ * as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License, version 3,
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>
+ *
+ */
+
+namespace OCA\DAV\DAV\Sharing;
+
+use OCA\DAV\Connector\Sabre\Principal;
+use OCP\IDBConnection;
+
+class Backend {
+
+	/** @var IDBConnection */
+	private $db;
+	/** @var Principal */
+	private $principalBackend;
+	/** @var string */
+	private $resourceType;
+
+	const ACCESS_OWNER = 1;
+	const ACCESS_READ_WRITE = 2;
+	const ACCESS_READ = 3;
+
+	/**
+	 * @param IDBConnection $db
+	 * @param Principal $principalBackend
+	 * @param string $resourceType
+	 */
+	public function __construct(IDBConnection $db, Principal $principalBackend, $resourceType) {
+		$this->db = $db;
+		$this->principalBackend = $principalBackend;
+		$this->resourceType = $resourceType;
+	}
+
+	/**
+	 * @param IShareable $shareable
+	 * @param string[] $add
+	 * @param string[] $remove
+	 */
+	public function updateShares($shareable, $add, $remove) {
+		foreach($add as $element) {
+			$this->shareWith($shareable, $element);
+		}
+		foreach($remove as $element) {
+			$this->unshare($shareable, $element);
+		}
+	}
+
+	/**
+	 * @param IShareable $shareable
+	 * @param string $element
+	 */
+	private function shareWith($shareable, $element) {
+		$user = $element['href'];
+		$parts = explode(':', $user, 2);
+		if ($parts[0] !== 'principal') {
+			return;
+		}
+
+		// don't share with owner
+		if ($shareable->getOwner() === $parts[1]) {
+			return;
+		}
+
+		// remove the share if it already exists
+		$this->unshare($shareable, $element['href']);
+		$access = self::ACCESS_READ;
+		if (isset($element['readOnly'])) {
+			$access = $element['readOnly'] ? self::ACCESS_READ : self::ACCESS_READ_WRITE;
+		}
+
+		$query = $this->db->getQueryBuilder();
+		$query->insert('dav_shares')
+			->values([
+				'principaluri' => $query->createNamedParameter($parts[1]),
+				'type' => $query->createNamedParameter($this->resourceType),
+				'access' => $query->createNamedParameter($access),
+				'resourceid' => $query->createNamedParameter($shareable->getResourceId())
+			]);
+		$query->execute();
+	}
+
+	/**
+	 * @param $resourceId
+	 */
+	public function deleteAllShares($resourceId) {
+		$query = $this->db->getQueryBuilder();
+		$query->delete('dav_shares')
+			->where($query->expr()->eq('resourceid', $query->createNamedParameter($resourceId)))
+			->andWhere($query->expr()->eq('type', $query->createNamedParameter($this->resourceType)))
+			->execute();
+	}
+
+	/**
+	 * @param IShareable $shareable
+	 * @param string $element
+	 */
+	private function unshare($shareable, $element) {
+		$parts = explode(':', $element, 2);
+		if ($parts[0] !== 'principal') {
+			return;
+		}
+
+		// don't share with owner
+		if ($shareable->getOwner() === $parts[1]) {
+			return;
+		}
+
+		$query = $this->db->getQueryBuilder();
+		$query->delete('dav_shares')
+			->where($query->expr()->eq('resourceid', $query->createNamedParameter($shareable->getResourceId())))
+			->andWhere($query->expr()->eq('type', $query->createNamedParameter($this->resourceType)))
+			->andWhere($query->expr()->eq('principaluri', $query->createNamedParameter($parts[1])))
+		;
+		$query->execute();
+	}
+
+	/**
+	 * Returns the list of people whom this resource is shared with.
+	 *
+	 * Every element in this array should have the following properties:
+	 *   * href - Often a mailto: address
+	 *   * commonName - Optional, for example a first + last name
+	 *   * status - See the Sabre\CalDAV\SharingPlugin::STATUS_ constants.
+	 *   * readOnly - boolean
+	 *   * summary - Optional, a description for the share
+	 *
+	 * @param int $resourceId
+	 * @return array
+	 */
+	public function getShares($resourceId) {
+		$query = $this->db->getQueryBuilder();
+		$result = $query->select(['principaluri', 'access'])
+			->from('dav_shares')
+			->where($query->expr()->eq('resourceid', $query->createNamedParameter($resourceId)))
+			->andWhere($query->expr()->eq('type', $query->createNamedParameter($this->resourceType)))
+			->execute();
+
+		$shares = [];
+		while($row = $result->fetch()) {
+			$p = $this->principalBackend->getPrincipalByPath($row['principaluri']);
+			$shares[]= [
+				'href' => "principal:${row['principaluri']}",
+				'commonName' => isset($p['{DAV:}displayname']) ? $p['{DAV:}displayname'] : '',
+				'status' => 1,
+				'readOnly' => ($row['access'] == self::ACCESS_READ),
+				'{http://owncloud.org/ns}principal' => $row['principaluri'],
+				'{http://owncloud.org/ns}group-share' => is_null($p)
+			];
+		}
+
+		return $shares;
+	}
+
+	/**
+	 * For shared resources the sharee is set in the ACL of the resource
+	 *
+	 * @param int $resourceId
+	 * @param array $acl
+	 * @return array
+	 */
+	public function applyShareAcl($resourceId, $acl) {
+
+		$shares = $this->getShares($resourceId);
+		foreach ($shares as $share) {
+			$acl[] = [
+				'privilege' => '{DAV:}read',
+				'principal' => $share['{' . \OCA\DAV\DAV\Sharing\Plugin::NS_OWNCLOUD . '}principal'],
+				'protected' => true,
+			];
+			if (!$share['readOnly']) {
+				$acl[] = [
+					'privilege' => '{DAV:}write',
+					'principal' => $share['{' . \OCA\DAV\DAV\Sharing\Plugin::NS_OWNCLOUD . '}principal'],
+					'protected' => true,
+				];
+			} else if ($this->resourceType === 'calendar') {
+				// Allow changing the properties of read only calendars,
+				// so users can change the visibility.
+				$acl[] = [
+					'privilege' => '{DAV:}write-properties',
+					'principal' => $share['{' . \OCA\DAV\DAV\Sharing\Plugin::NS_OWNCLOUD . '}principal'],
+					'protected' => true,
+				];
+			}
+		}
+		return $acl;
+	}
+}
diff --git a/apps/dav/lib/DAV/Sharing/IShareable.php b/apps/dav/lib/DAV/Sharing/IShareable.php
new file mode 100644
index 00000000000..f6b6bfa8862
--- /dev/null
+++ b/apps/dav/lib/DAV/Sharing/IShareable.php
@@ -0,0 +1,74 @@
+<?php
+/**
+ * @author Thomas Müller <thomas.mueller@tmit.eu>
+ *
+ * @copyright Copyright (c) 2016, ownCloud, Inc.
+ * @license AGPL-3.0
+ *
+ * This code is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License, version 3,
+ * as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License, version 3,
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>
+ *
+ */
+namespace OCA\DAV\DAV\Sharing;
+use Sabre\DAV\INode;
+
+/**
+ * This interface represents a dav resource that can be shared with other users.
+ *
+ */
+interface IShareable extends INode {
+
+	/**
+	 * Updates the list of shares.
+	 *
+	 * The first array is a list of people that are to be added to the
+	 * resource.
+	 *
+	 * Every element in the add array has the following properties:
+	 *   * href - A url. Usually a mailto: address
+	 *   * commonName - Usually a first and last name, or false
+	 *   * summary - A description of the share, can also be false
+	 *   * readOnly - A boolean value
+	 *
+	 * Every element in the remove array is just the address string.
+	 *
+	 * @param array $add
+	 * @param array $remove
+	 * @return void
+	 */
+	function updateShares(array $add, array $remove);
+
+	/**
+	 * Returns the list of people whom this resource is shared with.
+	 *
+	 * Every element in this array should have the following properties:
+	 *   * href - Often a mailto: address
+	 *   * commonName - Optional, for example a first + last name
+	 *   * status - See the Sabre\CalDAV\SharingPlugin::STATUS_ constants.
+	 *   * readOnly - boolean
+	 *   * summary - Optional, a description for the share
+	 *
+	 * @return array
+	 */
+	function getShares();
+
+	/**
+	 * @return int
+	 */
+	public function getResourceId();
+
+	/**
+	 * @return string
+	 */
+	public function getOwner();
+
+}
\ No newline at end of file
diff --git a/apps/dav/lib/DAV/Sharing/Plugin.php b/apps/dav/lib/DAV/Sharing/Plugin.php
new file mode 100644
index 00000000000..3173d1397ba
--- /dev/null
+++ b/apps/dav/lib/DAV/Sharing/Plugin.php
@@ -0,0 +1,200 @@
+<?php
+/**
+ * @author Thomas Müller <thomas.mueller@tmit.eu>
+ *
+ * @copyright Copyright (c) 2016, ownCloud, Inc.
+ * @license AGPL-3.0
+ *
+ * This code is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License, version 3,
+ * as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License, version 3,
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>
+ *
+ */
+
+namespace OCA\DAV\DAV\Sharing;
+
+use OCA\DAV\Connector\Sabre\Auth;
+use OCA\DAV\DAV\Sharing\Xml\Invite;
+use OCP\IRequest;
+use Sabre\DAV\Exception\BadRequest;
+use Sabre\DAV\Exception\NotFound;
+use Sabre\DAV\INode;
+use Sabre\DAV\PropFind;
+use Sabre\DAV\Server;
+use Sabre\DAV\ServerPlugin;
+use Sabre\HTTP\RequestInterface;
+use Sabre\HTTP\ResponseInterface;
+
+class Plugin extends ServerPlugin {
+
+	const NS_OWNCLOUD = 'http://owncloud.org/ns';
+
+	/** @var Auth */
+	private $auth;
+
+	/** @var IRequest */
+	private $request;
+
+	/**
+	 * Plugin constructor.
+	 *
+	 * @param Auth $authBackEnd
+	 * @param IRequest $request
+	 */
+	public function __construct(Auth $authBackEnd, IRequest $request) {
+		$this->auth = $authBackEnd;
+		$this->request = $request;
+	}
+
+	/**
+	 * Reference to SabreDAV server object.
+	 *
+	 * @var \Sabre\DAV\Server
+	 */
+	protected $server;
+
+	/**
+	 * This method should return a list of server-features.
+	 *
+	 * This is for example 'versioning' and is added to the DAV: header
+	 * in an OPTIONS response.
+	 *
+	 * @return string[]
+	 */
+	function getFeatures() {
+		return ['oc-resource-sharing'];
+	}
+
+	/**
+	 * Returns a plugin name.
+	 *
+	 * Using this name other plugins will be able to access other plugins
+	 * using Sabre\DAV\Server::getPlugin
+	 *
+	 * @return string
+	 */
+	function getPluginName() {
+		return 'oc-resource-sharing';
+	}
+
+	/**
+	 * This initializes the plugin.
+	 *
+	 * This function is called by Sabre\DAV\Server, after
+	 * addPlugin is called.
+	 *
+	 * This method should set up the required event subscriptions.
+	 *
+	 * @param Server $server
+	 * @return void
+	 */
+	function initialize(Server $server) {
+		$this->server = $server;
+		$this->server->xml->elementMap['{' . Plugin::NS_OWNCLOUD . '}share'] = 'OCA\\DAV\\DAV\\Sharing\\Xml\\ShareRequest';
+		$this->server->xml->elementMap['{' . Plugin::NS_OWNCLOUD . '}invite'] = 'OCA\\DAV\\DAV\\Sharing\\Xml\\Invite';
+
+		$this->server->on('method:POST', [$this, 'httpPost']);
+		$this->server->on('propFind',    [$this, 'propFind']);
+	}
+
+	/**
+	 * We intercept this to handle POST requests on a dav resource.
+	 *
+	 * @param RequestInterface $request
+	 * @param ResponseInterface $response
+	 * @return null|false
+	 */
+	function httpPost(RequestInterface $request, ResponseInterface $response) {
+
+		$path = $request->getPath();
+
+		// Only handling xml
+		$contentType = $request->getHeader('Content-Type');
+		if (strpos($contentType, 'application/xml') === false && strpos($contentType, 'text/xml') === false)
+			return;
+
+		// Making sure the node exists
+		try {
+			$node = $this->server->tree->getNodeForPath($path);
+		} catch (NotFound $e) {
+			return;
+		}
+
+		$requestBody = $request->getBodyAsString();
+
+		// If this request handler could not deal with this POST request, it
+		// will return 'null' and other plugins get a chance to handle the
+		// request.
+		//
+		// However, we already requested the full body. This is a problem,
+		// because a body can only be read once. This is why we preemptively
+		// re-populated the request body with the existing data.
+		$request->setBody($requestBody);
+
+		$message = $this->server->xml->parse($requestBody, $request->getUrl(), $documentType);
+
+		switch ($documentType) {
+
+			// Dealing with the 'share' document, which modified invitees on a
+			// calendar.
+			case '{' . self::NS_OWNCLOUD . '}share' :
+
+				// We can only deal with IShareableCalendar objects
+				if (!$node instanceof IShareable) {
+					return;
+				}
+
+				$this->server->transactionType = 'post-oc-resource-share';
+
+				// Getting ACL info
+				$acl = $this->server->getPlugin('acl');
+
+				// If there's no ACL support, we allow everything
+				if ($acl) {
+					/** @var \Sabre\DAVACL\Plugin $acl */
+					$acl->checkPrivileges($path, '{DAV:}write');
+				}
+
+				$node->updateShares($message->set, $message->remove);
+
+				$response->setStatus(200);
+				// Adding this because sending a response body may cause issues,
+				// and I wanted some type of indicator the response was handled.
+				$response->setHeader('X-Sabre-Status', 'everything-went-well');
+
+				// Breaking the event chain
+				return false;
+		}
+	}
+
+	/**
+	 * This event is triggered when properties are requested for a certain
+	 * node.
+	 *
+	 * This allows us to inject any properties early.
+	 *
+	 * @param PropFind $propFind
+	 * @param INode $node
+	 * @return void
+	 */
+	function propFind(PropFind $propFind, INode $node) {
+		if ($node instanceof IShareable) {
+
+			$propFind->handle('{' . Plugin::NS_OWNCLOUD . '}invite', function() use ($node) {
+				return new Invite(
+					$node->getShares()
+				);
+			});
+
+		}
+	}
+
+}
diff --git a/apps/dav/lib/DAV/Sharing/Xml/Invite.php b/apps/dav/lib/DAV/Sharing/Xml/Invite.php
new file mode 100644
index 00000000000..ae40ff06701
--- /dev/null
+++ b/apps/dav/lib/DAV/Sharing/Xml/Invite.php
@@ -0,0 +1,168 @@
+<?php
+/**
+ * @author Lukas Reschke <lukas@owncloud.com>
+ * @author Thomas Müller <thomas.mueller@tmit.eu>
+ *
+ * @copyright Copyright (c) 2016, ownCloud, Inc.
+ * @license AGPL-3.0
+ *
+ * This code is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License, version 3,
+ * as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License, version 3,
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>
+ *
+ */
+namespace OCA\DAV\DAV\Sharing\Xml;
+
+use OCA\DAV\DAV\Sharing\Plugin;
+use Sabre\Xml\Writer;
+use Sabre\Xml\XmlSerializable;
+
+/**
+ * Invite property
+ *
+ * This property encodes the 'invite' property, as defined by
+ * the 'caldav-sharing-02' spec, in the http://calendarserver.org/ns/
+ * namespace.
+ *
+ * @see https://trac.calendarserver.org/browser/CalendarServer/trunk/doc/Extensions/caldav-sharing-02.txt
+ * @copyright Copyright (C) fruux GmbH (https://fruux.com/)
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+class Invite implements XmlSerializable {
+
+	/**
+	 * The list of users a calendar has been shared to.
+	 *
+	 * @var array
+	 */
+	protected $users;
+
+	/**
+	 * The organizer contains information about the person who shared the
+	 * object.
+	 *
+	 * @var array
+	 */
+	protected $organizer;
+
+	/**
+	 * Creates the property.
+	 *
+	 * Users is an array. Each element of the array has the following
+	 * properties:
+	 *
+	 *   * href - Often a mailto: address
+	 *   * commonName - Optional, for example a first and lastname for a user.
+	 *   * status - One of the SharingPlugin::STATUS_* constants.
+	 *   * readOnly - true or false
+	 *   * summary - Optional, description of the share
+	 *
+	 * The organizer key is optional to specify. It's only useful when a
+	 * 'sharee' requests the sharing information.
+	 *
+	 * The organizer may have the following properties:
+	 *   * href - Often a mailto: address.
+	 *   * commonName - Optional human-readable name.
+	 *   * firstName - Optional first name.
+	 *   * lastName - Optional last name.
+	 *
+	 * If you wonder why these two structures are so different, I guess a
+	 * valid answer is that the current spec is still a draft.
+	 *
+	 * @param array $users
+	 */
+	function __construct(array $users, array $organizer = null) {
+
+		$this->users = $users;
+		$this->organizer = $organizer;
+
+	}
+
+	/**
+	 * Returns the list of users, as it was passed to the constructor.
+	 *
+	 * @return array
+	 */
+	function getValue() {
+
+		return $this->users;
+
+	}
+
+	/**
+	 * The xmlSerialize metod is called during xml writing.
+	 *
+	 * Use the $writer argument to write its own xml serialization.
+	 *
+	 * An important note: do _not_ create a parent element. Any element
+	 * implementing XmlSerializble should only ever write what's considered
+	 * its 'inner xml'.
+	 *
+	 * The parent of the current element is responsible for writing a
+	 * containing element.
+	 *
+	 * This allows serializers to be re-used for different element names.
+	 *
+	 * If you are opening new elements, you must also close them again.
+	 *
+	 * @param Writer $writer
+	 * @return void
+	 */
+	function xmlSerialize(Writer $writer) {
+
+		$cs = '{' . Plugin::NS_OWNCLOUD . '}';
+
+		if (!is_null($this->organizer)) {
+
+			$writer->startElement($cs . 'organizer');
+			$writer->writeElement('{DAV:}href', $this->organizer['href']);
+
+			if (isset($this->organizer['commonName']) && $this->organizer['commonName']) {
+				$writer->writeElement($cs . 'common-name', $this->organizer['commonName']);
+			}
+			if (isset($this->organizer['firstName']) && $this->organizer['firstName']) {
+				$writer->writeElement($cs . 'first-name', $this->organizer['firstName']);
+			}
+			if (isset($this->organizer['lastName']) && $this->organizer['lastName']) {
+				$writer->writeElement($cs . 'last-name', $this->organizer['lastName']);
+			}
+			$writer->endElement(); // organizer
+
+		}
+
+		foreach ($this->users as $user) {
+
+			$writer->startElement($cs . 'user');
+			$writer->writeElement('{DAV:}href', $user['href']);
+			if (isset($user['commonName']) && $user['commonName']) {
+				$writer->writeElement($cs . 'common-name', $user['commonName']);
+			}
+			$writer->writeElement($cs . 'invite-accepted');
+
+			$writer->startElement($cs . 'access');
+			if ($user['readOnly']) {
+				$writer->writeElement($cs . 'read');
+			} else {
+				$writer->writeElement($cs . 'read-write');
+			}
+			$writer->endElement(); // access
+
+			if (isset($user['summary']) && $user['summary']) {
+				$writer->writeElement($cs . 'summary', $user['summary']);
+			}
+
+			$writer->endElement(); //user
+
+		}
+
+	}
+}
diff --git a/apps/dav/lib/DAV/Sharing/Xml/ShareRequest.php b/apps/dav/lib/DAV/Sharing/Xml/ShareRequest.php
new file mode 100644
index 00000000000..776fb446b6c
--- /dev/null
+++ b/apps/dav/lib/DAV/Sharing/Xml/ShareRequest.php
@@ -0,0 +1,84 @@
+<?php
+/**
+ * @author Thomas Müller <thomas.mueller@tmit.eu>
+ *
+ * @copyright Copyright (c) 2016, ownCloud, Inc.
+ * @license AGPL-3.0
+ *
+ * This code is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License, version 3,
+ * as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License, version 3,
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>
+ *
+ */
+namespace OCA\DAV\DAV\Sharing\Xml;
+
+use OCA\DAV\DAV\Sharing\Plugin;
+use Sabre\Xml\Reader;
+use Sabre\Xml\XmlDeserializable;
+
+class ShareRequest implements XmlDeserializable {
+
+    public $set = [];
+
+    public $remove = [];
+
+    /**
+     * Constructor
+     *
+     * @param array $set
+     * @param array $remove
+     */
+    function __construct(array $set, array $remove) {
+
+        $this->set = $set;
+        $this->remove = $remove;
+
+    }
+
+    static function xmlDeserialize(Reader $reader) {
+
+        $elements = $reader->parseInnerTree([
+            '{' . Plugin::NS_OWNCLOUD. '}set'    => 'Sabre\\Xml\\Element\\KeyValue',
+            '{' . Plugin::NS_OWNCLOUD . '}remove' => 'Sabre\\Xml\\Element\\KeyValue',
+        ]);
+
+        $set = [];
+        $remove = [];
+
+        foreach ($elements as $elem) {
+            switch ($elem['name']) {
+
+                case '{' . Plugin::NS_OWNCLOUD . '}set' :
+                    $sharee = $elem['value'];
+
+                    $sumElem = '{' . Plugin::NS_OWNCLOUD . '}summary';
+                    $commonName = '{' . Plugin::NS_OWNCLOUD . '}common-name';
+
+                    $set[] = [
+                        'href'       => $sharee['{DAV:}href'],
+                        'commonName' => isset($sharee[$commonName]) ? $sharee[$commonName] : null,
+                        'summary'    => isset($sharee[$sumElem]) ? $sharee[$sumElem] : null,
+                        'readOnly'   => !array_key_exists('{' . Plugin::NS_OWNCLOUD . '}read-write', $sharee),
+                    ];
+                    break;
+
+                case '{' . Plugin::NS_OWNCLOUD . '}remove' :
+                    $remove[] = $elem['value']['{DAV:}href'];
+                    break;
+
+            }
+        }
+
+        return new self($set, $remove);
+
+    }
+
+}
diff --git a/apps/dav/lib/DAV/SystemPrincipalBackend.php b/apps/dav/lib/DAV/SystemPrincipalBackend.php
new file mode 100644
index 00000000000..8001ec4e6c6
--- /dev/null
+++ b/apps/dav/lib/DAV/SystemPrincipalBackend.php
@@ -0,0 +1,179 @@
+<?php
+/**
+ * @author Thomas Müller <thomas.mueller@tmit.eu>
+ *
+ * @copyright Copyright (c) 2016, ownCloud, Inc.
+ * @license AGPL-3.0
+ *
+ * This code is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License, version 3,
+ * as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License, version 3,
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>
+ *
+ */
+
+namespace OCA\DAV\DAV;
+
+use Sabre\DAVACL\PrincipalBackend\AbstractBackend;
+use Sabre\HTTP\URLUtil;
+
+class SystemPrincipalBackend extends AbstractBackend {
+
+	/**
+	 * Returns a list of principals based on a prefix.
+	 *
+	 * This prefix will often contain something like 'principals'. You are only
+	 * expected to return principals that are in this base path.
+	 *
+	 * You are expected to return at least a 'uri' for every user, you can
+	 * return any additional properties if you wish so. Common properties are:
+	 *   {DAV:}displayname
+	 *   {http://sabredav.org/ns}email-address - This is a custom SabreDAV
+	 *     field that's actually injected in a number of other properties. If
+	 *     you have an email address, use this property.
+	 *
+	 * @param string $prefixPath
+	 * @return array
+	 */
+	function getPrincipalsByPrefix($prefixPath) {
+		$principals = [];
+
+		if ($prefixPath === 'principals/system') {
+			$principals[] = [
+				'uri' => 'principals/system/system',
+				'{DAV:}displayname' => 'system',
+			];
+		}
+
+		return $principals;
+	}
+
+	/**
+	 * Returns a specific principal, specified by it's path.
+	 * The returned structure should be the exact same as from
+	 * getPrincipalsByPrefix.
+	 *
+	 * @param string $path
+	 * @return array
+	 */
+	function getPrincipalByPath($path) {
+
+		if ($path === 'principals/system/system') {
+			$principal = [
+				'uri' => 'principals/system/system',
+				'{DAV:}displayname' => 'system',
+			];
+			return $principal;
+		}
+
+		return null;
+	}
+
+	/**
+	 * Updates one ore more webdav properties on a principal.
+	 *
+	 * The list of mutations is stored in a Sabre\DAV\PropPatch object.
+	 * To do the actual updates, you must tell this object which properties
+	 * you're going to process with the handle() method.
+	 *
+	 * Calling the handle method is like telling the PropPatch object "I
+	 * promise I can handle updating this property".
+	 *
+	 * Read the PropPatch documentation for more info and examples.
+	 *
+	 * @param string $path
+	 * @param \Sabre\DAV\PropPatch $propPatch
+	 * @return void
+	 */
+	function updatePrincipal($path, \Sabre\DAV\PropPatch $propPatch) {
+	}
+
+	/**
+	 * This method is used to search for principals matching a set of
+	 * properties.
+	 *
+	 * This search is specifically used by RFC3744's principal-property-search
+	 * REPORT.
+	 *
+	 * The actual search should be a unicode-non-case-sensitive search. The
+	 * keys in searchProperties are the WebDAV property names, while the values
+	 * are the property values to search on.
+	 *
+	 * By default, if multiple properties are submitted to this method, the
+	 * various properties should be combined with 'AND'. If $test is set to
+	 * 'anyof', it should be combined using 'OR'.
+	 *
+	 * This method should simply return an array with full principal uri's.
+	 *
+	 * If somebody attempted to search on a property the backend does not
+	 * support, you should simply return 0 results.
+	 *
+	 * You can also just return 0 results if you choose to not support
+	 * searching at all, but keep in mind that this may stop certain features
+	 * from working.
+	 *
+	 * @param string $prefixPath
+	 * @param array $searchProperties
+	 * @param string $test
+	 * @return array
+	 */
+	function searchPrincipals($prefixPath, array $searchProperties, $test = 'allof') {
+		return [];
+	}
+
+	/**
+	 * Returns the list of members for a group-principal
+	 *
+	 * @param string $principal
+	 * @return array
+	 */
+	function getGroupMemberSet($principal) {
+		// TODO: for now the group principal has only one member, the user itself
+		$principal = $this->getPrincipalByPath($principal);
+		if (!$principal) {
+			throw new \Sabre\DAV\Exception('Principal not found');
+		}
+
+		return [$principal['uri']];
+	}
+
+	/**
+	 * Returns the list of groups a principal is a member of
+	 *
+	 * @param string $principal
+	 * @return array
+	 */
+	function getGroupMembership($principal) {
+		list($prefix, $name) = URLUtil::splitPath($principal);
+
+		if ($prefix === 'principals/system') {
+			$principal = $this->getPrincipalByPath($principal);
+			if (!$principal) {
+				throw new \Sabre\DAV\Exception('Principal not found');
+			}
+
+			return [];
+		}
+		return [];
+	}
+
+	/**
+	 * Updates the list of group members for a group principal.
+	 *
+	 * The principals should be passed as a list of uri's.
+	 *
+	 * @param string $principal
+	 * @param array $members
+	 * @return void
+	 */
+	function setGroupMemberSet($principal, array $members) {
+		throw new \Sabre\DAV\Exception('Setting members of the group is not supported yet');
+	}
+}