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<?php
/**
* SPDX-FileCopyrightText: 2022-2024 Nextcloud GmbH and Nextcloud contributors
* SPDX-FileCopyrightText: 2019 ownCloud GmbH
* SPDX-License-Identifier: AGPL-3.0-only
*/
namespace OCA\DAV\DAV;
use OCA\DAV\Connector\Sabre\Exception\Forbidden;
use OCA\DAV\Connector\Sabre\File as DavFile;
use OCA\Files_Versions\Sabre\VersionFile;
use OCP\Files\Folder;
use OCP\Files\NotFoundException;
use OCP\Files\Storage\ISharedStorage;
use Sabre\DAV\Exception\NotFound;
use Sabre\DAV\Server;
use Sabre\DAV\ServerPlugin;
use Sabre\HTTP\RequestInterface;
/**
* Sabre plugin for restricting file share receiver download:
*/
class ViewOnlyPlugin extends ServerPlugin {
private ?Server $server = null;
public function __construct(
private ?Folder $userFolder,
) {
}
/**
* 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.
*/
public function initialize(Server $server): void {
$this->server = $server;
//priority 90 to make sure the plugin is called before
//Sabre\DAV\CorePlugin::httpGet
$this->server->on('method:GET', [$this, 'checkViewOnly'], 90);
$this->server->on('method:COPY', [$this, 'checkViewOnly'], 90);
$this->server->on('method:MOVE', [$this, 'checkViewOnly'], 90);
}
/**
* Disallow download via DAV Api in case file being received share
* and having special permission
*
* @throws Forbidden
* @throws NotFoundException
*/
public function checkViewOnly(RequestInterface $request): bool {
$path = $request->getPath();
try {
assert($this->server !== null);
$davNode = $this->server->tree->getNodeForPath($path);
if ($davNode instanceof DavFile) {
// Restrict view-only to nodes which are shared
$node = $davNode->getNode();
} elseif ($davNode instanceof VersionFile) {
$node = $davNode->getVersion()->getSourceFile();
$currentUserId = $this->userFolder?->getOwner()?->getUID();
// The version source file is relative to the owner storage.
// But we need the node from the current user perspective.
if ($node->getOwner()->getUID() !== $currentUserId) {
$nodes = $this->userFolder->getById($node->getId());
$node = array_pop($nodes);
if (!$node) {
throw new NotFoundException('Version file not accessible by current user');
}
}
} else {
return true;
}
$storage = $node->getStorage();
if (!$storage->instanceOfStorage(ISharedStorage::class)) {
return true;
}
// Extract extra permissions
/** @var ISharedStorage $storage */
$share = $storage->getShare();
$attributes = $share->getAttributes();
if ($attributes === null) {
return true;
}
// Check if read-only and on whether permission can download is both set and disabled.
$canDownload = $attributes->getAttribute('permissions', 'download');
if ($canDownload !== null && !$canDownload) {
throw new Forbidden('Access to this shared resource has been denied because its download permission is disabled.');
}
} catch (NotFound $e) {
// File not found
}
return true;
}
}
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