feat(s3): Use multipart upload for chunked uploading

This allows to stream file chunks directly to S3 during upload.

Signed-off-by: Julius Härtl <jus@bitgrid.net>

11 files changed, 578 insertions, 9 deletions

diff --git a/apps/dav/composer/composer/autoload_classmap.php b/apps/dav/composer/composer/autoload_classmap.php
index a100dac1d85..e7e2c34be62 100644
--- a/apps/dav/composer/composer/autoload_classmap.php
+++ b/apps/dav/composer/composer/autoload_classmap.php
@@ -310,8 +310,10 @@ return array(
     'OCA\\DAV\\Traits\\PrincipalProxyTrait' => $baseDir . '/../lib/Traits/PrincipalProxyTrait.php',
     'OCA\\DAV\\Upload\\AssemblyStream' => $baseDir . '/../lib/Upload/AssemblyStream.php',
     'OCA\\DAV\\Upload\\ChunkingPlugin' => $baseDir . '/../lib/Upload/ChunkingPlugin.php',
+    'OCA\\DAV\\Upload\\ChunkingV2Plugin' => $baseDir . '/../lib/Upload/ChunkingV2Plugin.php',
     'OCA\\DAV\\Upload\\CleanupService' => $baseDir . '/../lib/Upload/CleanupService.php',
     'OCA\\DAV\\Upload\\FutureFile' => $baseDir . '/../lib/Upload/FutureFile.php',
+    'OCA\\DAV\\Upload\\PartFile' => $baseDir . '/../lib/Upload/PartFile.php',
     'OCA\\DAV\\Upload\\RootCollection' => $baseDir . '/../lib/Upload/RootCollection.php',
     'OCA\\DAV\\Upload\\UploadFile' => $baseDir . '/../lib/Upload/UploadFile.php',
     'OCA\\DAV\\Upload\\UploadFolder' => $baseDir . '/../lib/Upload/UploadFolder.php',
diff --git a/apps/dav/composer/composer/autoload_static.php b/apps/dav/composer/composer/autoload_static.php
index 4187bb6c6f3..5fa87bc354a 100644
--- a/apps/dav/composer/composer/autoload_static.php
+++ b/apps/dav/composer/composer/autoload_static.php
@@ -325,8 +325,10 @@ class ComposerStaticInitDAV
         'OCA\\DAV\\Traits\\PrincipalProxyTrait' => __DIR__ . '/..' . '/../lib/Traits/PrincipalProxyTrait.php',
         'OCA\\DAV\\Upload\\AssemblyStream' => __DIR__ . '/..' . '/../lib/Upload/AssemblyStream.php',
         'OCA\\DAV\\Upload\\ChunkingPlugin' => __DIR__ . '/..' . '/../lib/Upload/ChunkingPlugin.php',
+        'OCA\\DAV\\Upload\\ChunkingV2Plugin' => __DIR__ . '/..' . '/../lib/Upload/ChunkingV2Plugin.php',
         'OCA\\DAV\\Upload\\CleanupService' => __DIR__ . '/..' . '/../lib/Upload/CleanupService.php',
         'OCA\\DAV\\Upload\\FutureFile' => __DIR__ . '/..' . '/../lib/Upload/FutureFile.php',
+        'OCA\\DAV\\Upload\\PartFile' => __DIR__ . '/..' . '/../lib/Upload/PartFile.php',
         'OCA\\DAV\\Upload\\RootCollection' => __DIR__ . '/..' . '/../lib/Upload/RootCollection.php',
         'OCA\\DAV\\Upload\\UploadFile' => __DIR__ . '/..' . '/../lib/Upload/UploadFile.php',
         'OCA\\DAV\\Upload\\UploadFolder' => __DIR__ . '/..' . '/../lib/Upload/UploadFolder.php',
diff --git a/apps/dav/lib/Connector/Sabre/Directory.php b/apps/dav/lib/Connector/Sabre/Directory.php
index 531ccff9d92..c29070fe921 100644
--- a/apps/dav/lib/Connector/Sabre/Directory.php
+++ b/apps/dav/lib/Connector/Sabre/Directory.php
@@ -38,6 +38,7 @@ use OC\Metadata\FileMetadata;
 use OCA\DAV\Connector\Sabre\Exception\FileLocked;
 use OCA\DAV\Connector\Sabre\Exception\Forbidden;
 use OCA\DAV\Connector\Sabre\Exception\InvalidPath;
+use OCA\DAV\Upload\FutureFile;
 use OCP\Files\FileInfo;
 use OCP\Files\Folder;
 use OCP\Files\ForbiddenException;
diff --git a/apps/dav/lib/Connector/Sabre/Node.php b/apps/dav/lib/Connector/Sabre/Node.php
index ee159cef1d6..2c8d313eefd 100644
--- a/apps/dav/lib/Connector/Sabre/Node.php
+++ b/apps/dav/lib/Connector/Sabre/Node.php
@@ -261,6 +261,10 @@ abstract class Node implements \Sabre\DAV\INode {
 		return $this->info->getId();
 	}
 
+	public function getInternalPath(): string {
+		return $this->info->getInternalPath();
+	}
+
 	/**
 	 * @param string $user
 	 * @return int
diff --git a/apps/dav/lib/Server.php b/apps/dav/lib/Server.php
index a5833e5175f..ada279bc7b2 100644
--- a/apps/dav/lib/Server.php
+++ b/apps/dav/lib/Server.php
@@ -71,9 +71,11 @@ use OCA\DAV\Profiler\ProfilerPlugin;
 use OCA\DAV\Provisioning\Apple\AppleProvisioningPlugin;
 use OCA\DAV\SystemTag\SystemTagPlugin;
 use OCA\DAV\Upload\ChunkingPlugin;
+use OCA\DAV\Upload\ChunkingV2Plugin;
 use OCP\AppFramework\Http\Response;
 use OCP\Diagnostics\IEventLogger;
 use OCP\EventDispatcher\IEventDispatcher;
+use OCP\ICacheFactory;
 use OCP\IRequest;
 use OCP\Profiler\IProfiler;
 use OCP\SabrePluginEvent;
@@ -218,6 +220,7 @@ class Server {
 
 		$this->server->addPlugin(new CopyEtagHeaderPlugin());
 		$this->server->addPlugin(new RequestIdHeaderPlugin(\OC::$server->get(IRequest::class)));
+		$this->server->addPlugin(new ChunkingV2Plugin(\OCP\Server::get(ICacheFactory::class)));
 		$this->server->addPlugin(new ChunkingPlugin());
 
 		// allow setup of additional plugins
diff --git a/apps/dav/lib/Upload/ChunkingV2Plugin.php b/apps/dav/lib/Upload/ChunkingV2Plugin.php
new file mode 100644
index 00000000000..cb7c802125c
--- /dev/null
+++ b/apps/dav/lib/Upload/ChunkingV2Plugin.php
@@ -0,0 +1,392 @@
+<?php
+
+declare(strict_types=1);
+/*
+ * @copyright Copyright (c) 2021 Julius Härtl <jus@bitgrid.net>
+ *
+ * @author Julius Härtl <jus@bitgrid.net>
+ *
+ * @license GNU AGPL version 3 or any later version
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * 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
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+namespace OCA\DAV\Upload;
+
+use Exception;
+use InvalidArgumentException;
+use OC\Files\Filesystem;
+use OC\Files\ObjectStore\ObjectStoreStorage;
+use OC\Files\View;
+use OC_Hook;
+use OCA\DAV\Connector\Sabre\Directory;
+use OCA\DAV\Connector\Sabre\File;
+use OCP\Files\IMimeTypeDetector;
+use OCP\Files\IRootFolder;
+use OCP\Files\ObjectStore\IObjectStoreMultiPartUpload;
+use OCP\Files\Storage\IChunkedFileWrite;
+use OCP\Files\StorageInvalidException;
+use OCP\ICache;
+use OCP\ICacheFactory;
+use OCP\Lock\ILockingProvider;
+use Sabre\DAV\Exception\BadRequest;
+use Sabre\DAV\Exception\InsufficientStorage;
+use Sabre\DAV\Exception\NotFound;
+use Sabre\DAV\Exception\PreconditionFailed;
+use Sabre\DAV\ICollection;
+use Sabre\DAV\INode;
+use Sabre\DAV\Server;
+use Sabre\DAV\ServerPlugin;
+use Sabre\HTTP\RequestInterface;
+use Sabre\HTTP\ResponseInterface;
+use Sabre\Uri;
+
+class ChunkingV2Plugin extends ServerPlugin {
+	/** @var Server */
+	private $server;
+	/** @var UploadFolder */
+	private $uploadFolder;
+	/** @var ICache */
+	private $cache;
+
+	private ?string $uploadId = null;
+	private ?string $uploadPath = null;
+
+	private const TEMP_TARGET = '.target';
+
+	public const CACHE_KEY = 'chunking-v2';
+	public const UPLOAD_TARGET_PATH = 'upload-target-path';
+	public const UPLOAD_TARGET_ID = 'upload-target-id';
+	public const UPLOAD_ID = 'upload-id';
+
+	private const DESTINATION_HEADER = 'Destination';
+
+	public function __construct(ICacheFactory $cacheFactory) {
+		$this->cache = $cacheFactory->createDistributed(self::CACHE_KEY);
+	}
+
+	/**
+	 * @inheritdoc
+	 */
+	public function initialize(Server $server) {
+		$server->on('afterMethod:MKCOL', [$this, 'afterMkcol']);
+		$server->on('beforeMethod:PUT', [$this, 'beforePut']);
+		$server->on('beforeMethod:DELETE', [$this, 'beforeDelete']);
+		$server->on('beforeMove', [$this, 'beforeMove'], 90);
+
+		$this->server = $server;
+	}
+
+	/**
+	 * @param string $path
+	 * @param bool $createIfNotExists
+	 * @return FutureFile|UploadFile|ICollection|INode
+	 */
+	private function getUploadFile(string $path, bool $createIfNotExists = false) {
+		try {
+			$actualFile = $this->server->tree->getNodeForPath($path);
+			// Only directly upload to the target file if it is on the same storage
+			// There may be further potential to optimize here by also uploading
+			// to other storages directly. This would require to also carefully pick
+			// the storage/path used in getStorage()
+			if ($actualFile instanceof File && $this->uploadFolder->getStorage()->getId() === $actualFile->getNode()->getStorage()->getId()) {
+				return $actualFile;
+			}
+		} catch (NotFound $e) {
+			// If there is no target file we upload to the upload folder first
+		}
+
+		// Use file in the upload directory that will be copied or moved afterwards
+		if ($createIfNotExists) {
+			$this->uploadFolder->createFile(self::TEMP_TARGET);
+		}
+
+		/** @var UploadFile $uploadFile */
+		$uploadFile = $this->uploadFolder->getChild(self::TEMP_TARGET);
+		return $uploadFile->getFile();
+	}
+
+	public function afterMkcol(RequestInterface $request, ResponseInterface $response): bool {
+		try {
+			$this->prepareUpload($request->getPath());
+			$this->checkPrerequisites(false);
+		} catch (BadRequest|StorageInvalidException|NotFound $e) {
+			return true;
+		}
+
+		$this->uploadPath = $this->server->calculateUri($this->server->httpRequest->getHeader(self::DESTINATION_HEADER));
+		$targetFile = $this->getUploadFile($this->uploadPath, true);
+		[$storage, $storagePath] = $this->getUploadStorage($this->uploadPath);
+
+		$this->uploadId = $storage->startChunkedWrite($storagePath);
+
+		$this->cache->set($this->uploadFolder->getName(), [
+			self::UPLOAD_ID => $this->uploadId,
+			self::UPLOAD_TARGET_PATH => $this->uploadPath,
+			self::UPLOAD_TARGET_ID => $targetFile->getId(),
+		], 86400);
+
+		$response->setStatus(201);
+		return true;
+	}
+
+	public function beforePut(RequestInterface $request, ResponseInterface $response): bool {
+		try {
+			$this->prepareUpload(dirname($request->getPath()));
+			$this->checkPrerequisites();
+		} catch (StorageInvalidException|BadRequest|NotFound $e) {
+			return true;
+		}
+
+		[$storage, $storagePath] = $this->getUploadStorage($this->uploadPath);
+
+		$chunkName = basename($request->getPath());
+		$partId = is_numeric($chunkName) ? (int)$chunkName : -1;
+		if (!($partId >= 1 && $partId <= 10000)) {
+			throw new BadRequest('Invalid chunk name, must be numeric between 1 and 10000');
+		}
+
+		$uploadFile = $this->getUploadFile($this->uploadPath);
+		$tempTargetFile = null;
+
+		$additionalSize = (int)$request->getHeader('Content-Length');
+		if ($this->uploadFolder->childExists(self::TEMP_TARGET) && $this->uploadPath) {
+			/** @var UploadFile $tempTargetFile */
+			$tempTargetFile = $this->uploadFolder->getChild(self::TEMP_TARGET);
+			[$destinationDir, $destinationName] = Uri\split($this->uploadPath);
+			/** @var Directory $destinationParent */
+			$destinationParent = $this->server->tree->getNodeForPath($destinationDir);
+			$free = $storage->free_space($destinationParent->getInternalPath());
+			$newSize = $tempTargetFile->getSize() + $additionalSize;
+			if ($free >= 0 && ($tempTargetFile->getSize() > $free || $newSize > $free)) {
+				throw new InsufficientStorage("Insufficient space in $this->uploadPath");
+			}
+		}
+
+		$stream = $request->getBodyAsStream();
+		$storage->putChunkedWritePart($storagePath, $this->uploadId, (string)$partId, $stream, $additionalSize);
+
+		$storage->getCache()->update($uploadFile->getId(), ['size' => $uploadFile->getSize() + $additionalSize]);
+		if ($tempTargetFile) {
+			$storage->getPropagator()->propagateChange($tempTargetFile->getInternalPath(), time(), $additionalSize);
+		}
+
+		$response->setStatus(201);
+		return false;
+	}
+
+	public function beforeMove($sourcePath, $destination): bool {
+		try {
+			$this->prepareUpload(dirname($sourcePath));
+			$this->checkPrerequisites();
+		} catch (StorageInvalidException|BadRequest|NotFound|PreconditionFailed $e) {
+			return true;
+		}
+		[$storage, $storagePath] = $this->getUploadStorage($this->uploadPath);
+
+		$targetFile = $this->getUploadFile($this->uploadPath);
+
+		[$destinationDir, $destinationName] = Uri\split($destination);
+		/** @var Directory $destinationParent */
+		$destinationParent = $this->server->tree->getNodeForPath($destinationDir);
+		$destinationExists = $destinationParent->childExists($destinationName);
+
+
+		// allow sync clients to send the modification and creation time along in a header
+		$updateFileInfo = [];
+		if ($this->server->httpRequest->getHeader('X-OC-MTime') !== null) {
+			$updateFileInfo['mtime'] = $this->sanitizeMtime($this->server->httpRequest->getHeader('X-OC-MTime'));
+			$this->server->httpResponse->setHeader('X-OC-MTime', 'accepted');
+		}
+		if ($this->server->httpRequest->getHeader('X-OC-CTime') !== null) {
+			$updateFileInfo['creation_time'] = $this->sanitizeMtime($this->server->httpRequest->getHeader('X-OC-CTime'));
+			$this->server->httpResponse->setHeader('X-OC-CTime', 'accepted');
+		}
+		$updateFileInfo['mimetype'] = \OCP\Server::get(IMimeTypeDetector::class)->detectPath($destinationName);
+
+		if ($storage->instanceOfStorage(ObjectStoreStorage::class) && $storage->getObjectStore() instanceof IObjectStoreMultiPartUpload) {
+			/** @var ObjectStoreStorage $storage */
+			/** @var IObjectStoreMultiPartUpload $objectStore */
+			$objectStore = $storage->getObjectStore();
+			$parts = $objectStore->getMultipartUploads($storage->getURN($targetFile->getId()), $this->uploadId);
+			$size = 0;
+			foreach ($parts as $part) {
+				$size += $part['Size'];
+			}
+			$free = $storage->free_space($destinationParent->getInternalPath());
+			if ($free >= 0 && ($size > $free)) {
+				throw new InsufficientStorage("Insufficient space in $this->uploadPath");
+			}
+		}
+
+		$destinationInView = $destinationParent->getFileInfo()->getPath() . '/' . $destinationName;
+		$this->completeChunkedWrite($destinationInView);
+
+		$rootView = new View();
+		$rootView->putFileInfo($destinationInView, $updateFileInfo);
+
+		$sourceNode = $this->server->tree->getNodeForPath($sourcePath);
+		if ($sourceNode instanceof FutureFile) {
+			$this->uploadFolder->delete();
+		}
+
+		$this->server->emit('afterMove', [$sourcePath, $destination]);
+		$this->server->emit('afterUnbind', [$sourcePath]);
+		$this->server->emit('afterBind', [$destination]);
+
+		$response = $this->server->httpResponse;
+		$response->setHeader('Content-Type', 'application/xml; charset=utf-8');
+		$response->setHeader('Content-Length', '0');
+		$response->setStatus($destinationExists ? 204 : 201);
+		return false;
+	}
+
+	public function beforeDelete(RequestInterface $request, ResponseInterface $response) {
+		try {
+			$this->prepareUpload($request->getPath());
+			if (!$this->uploadFolder instanceof UploadFolder) {
+				return true;
+			}
+
+			[$storage, $storagePath] = $this->getUploadStorage($this->uploadPath);
+			$storage->cancelChunkedWrite($storagePath, $this->uploadId);
+			return true;
+		} catch (NotFound $e) {
+			return true;
+		}
+	}
+
+	/**
+	 * @throws BadRequest
+	 * @throws PreconditionFailed
+	 * @throws StorageInvalidException
+	 */
+	private function checkPrerequisites(bool $checkUploadMetadata = true): void {
+		if (!$this->uploadFolder instanceof UploadFolder || empty($this->server->httpRequest->getHeader(self::DESTINATION_HEADER))) {
+			throw new BadRequest('Skipping chunked file writing as the destination header was not passed');
+		}
+		if (!$this->uploadFolder->getStorage()->instanceOfStorage(IChunkedFileWrite::class)) {
+			throw new StorageInvalidException('Storage does not support chunked file writing');
+		}
+
+		if ($checkUploadMetadata) {
+			if ($this->uploadId === null || $this->uploadPath === null) {
+				throw new PreconditionFailed('Missing metadata for chunked upload');
+			}
+		}
+	}
+
+	/**
+	 * @return array [IStorage, string]
+	 */
+	private function getUploadStorage(string $targetPath): array {
+		$storage = $this->uploadFolder->getStorage();
+		$targetFile = $this->getUploadFile($targetPath);
+		return [$storage, $targetFile->getInternalPath()];
+	}
+
+	protected function sanitizeMtime(string $mtimeFromRequest): int {
+		if (!is_numeric($mtimeFromRequest)) {
+			throw new InvalidArgumentException('X-OC-MTime header must be an integer (unix timestamp).');
+		}
+
+		return (int)$mtimeFromRequest;
+	}
+
+	/**
+	 * @throws NotFound
+	 */
+	public function prepareUpload($path): void {
+		$this->uploadFolder = $this->server->tree->getNodeForPath($path);
+		$uploadMetadata = $this->cache->get($this->uploadFolder->getName());
+		$this->uploadId = $uploadMetadata[self::UPLOAD_ID] ?? null;
+		$this->uploadPath = $uploadMetadata[self::UPLOAD_TARGET_PATH] ?? null;
+	}
+
+	private function completeChunkedWrite(string $targetAbsolutePath): void {
+		$uploadFile = $this->getUploadFile($this->uploadPath)->getNode();
+		[$storage, $storagePath] = $this->getUploadStorage($this->uploadPath);
+
+		$rootFolder = \OCP\Server::get(IRootFolder::class);
+		$exists = $rootFolder->nodeExists($targetAbsolutePath);
+
+		$uploadFile->lock(ILockingProvider::LOCK_SHARED);
+		$this->emitPreHooks($targetAbsolutePath, $exists);
+		try {
+			$uploadFile->changeLock(ILockingProvider::LOCK_EXCLUSIVE);
+			$storage->completeChunkedWrite($storagePath, $this->uploadId);
+			$uploadFile->changeLock(ILockingProvider::LOCK_SHARED);
+		} catch (Exception $e) {
+			$uploadFile->unlock(ILockingProvider::LOCK_EXCLUSIVE);
+			throw $e;
+		}
+
+		// If the file was not uploaded to the user storage directly we need to copy/move it
+		try {
+			$uploadFileAbsolutePath = Filesystem::getRoot() . $uploadFile->getPath();
+			if ($uploadFileAbsolutePath !== $targetAbsolutePath) {
+				$uploadFile = $rootFolder->get($uploadFile->getFileInfo()->getPath());
+				if ($exists) {
+					$uploadFile->copy($targetAbsolutePath);
+				} else {
+					$uploadFile->move($targetAbsolutePath);
+				}
+			}
+			$this->emitPostHooks($targetAbsolutePath, $exists);
+		} catch (Exception $e) {
+			$uploadFile->unlock(ILockingProvider::LOCK_SHARED);
+			throw $e;
+		}
+	}
+
+	private function emitPreHooks(string $target, bool $exists): void {
+		$hookPath = $this->getHookPath($target);
+		if (!$exists) {
+			OC_Hook::emit(Filesystem::CLASSNAME, Filesystem::signal_create, [
+				Filesystem::signal_param_path => $hookPath,
+			]);
+		} else {
+			OC_Hook::emit(Filesystem::CLASSNAME, Filesystem::signal_update, [
+				Filesystem::signal_param_path => $hookPath,
+			]);
+		}
+		OC_Hook::emit(Filesystem::CLASSNAME, Filesystem::signal_write, [
+			Filesystem::signal_param_path => $hookPath,
+		]);
+	}
+
+	private function emitPostHooks(string $target, bool $exists): void {
+		$hookPath = $this->getHookPath($target);
+		if (!$exists) {
+			OC_Hook::emit(Filesystem::CLASSNAME, Filesystem::signal_post_create, [
+				Filesystem::signal_param_path => $hookPath,
+			]);
+		} else {
+			OC_Hook::emit(Filesystem::CLASSNAME, Filesystem::signal_post_update, [
+				Filesystem::signal_param_path => $hookPath,
+			]);
+		}
+		OC_Hook::emit(Filesystem::CLASSNAME, Filesystem::signal_post_write, [
+			Filesystem::signal_param_path => $hookPath,
+		]);
+	}
+
+	private function getHookPath(string $path): ?string {
+		if (!Filesystem::getView()) {
+			return $path;
+		}
+		return Filesystem::getView()->getRelativePath($path);
+	}
+}
diff --git a/apps/dav/lib/Upload/FutureFile.php b/apps/dav/lib/Upload/FutureFile.php
index eba550a62da..0b158e364cf 100644
--- a/apps/dav/lib/Upload/FutureFile.php
+++ b/apps/dav/lib/Upload/FutureFile.php
@@ -36,7 +36,6 @@ use Sabre\DAV\IFile;
  * @package OCA\DAV\Upload
  */
 class FutureFile implements \Sabre\DAV\IFile {
-
 	/** @var Directory */
 	private $root;
 	/** @var string */
@@ -66,6 +65,10 @@ class FutureFile implements \Sabre\DAV\IFile {
 		return AssemblyStream::wrap($nodes);
 	}
 
+	public function getPath() {
+		return $this->root->getFileInfo()->getInternalPath() . '/.file';
+	}
+
 	/**
 	 * @inheritdoc
 	 */
diff --git a/apps/dav/lib/Upload/PartFile.php b/apps/dav/lib/Upload/PartFile.php
new file mode 100644
index 00000000000..8bfe992a987
--- /dev/null
+++ b/apps/dav/lib/Upload/PartFile.php
@@ -0,0 +1,111 @@
+<?php
+/**
+ * @copyright Copyright (c) 2016, ownCloud, Inc.
+ *
+ * @author Christoph Wurst <christoph@winzerhof-wurst.at>
+ * @author Lukas Reschke <lukas@statuscode.ch>
+ * @author Thomas Müller <thomas.mueller@tmit.eu>
+ *
+ * @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\Upload;
+
+use OCA\DAV\Connector\Sabre\Directory;
+use Sabre\DAV\Exception\Forbidden;
+use Sabre\DAV\IFile;
+
+/**
+ * This class represents an Upload part which is not present on the storage itself
+ * but handled directly by external storage services like S3 with Multipart Upload
+ */
+class PartFile implements IFile {
+	/** @var Directory */
+	private $root;
+	/** @var array */
+	private $partInfo;
+
+	public function __construct(Directory $root, array $partInfo) {
+		$this->root = $root;
+		$this->partInfo = $partInfo;
+	}
+
+	/**
+	 * @inheritdoc
+	 */
+	public function put($data) {
+		throw new Forbidden('Permission denied to put into this file');
+	}
+
+	/**
+	 * @inheritdoc
+	 */
+	public function get() {
+		throw new Forbidden('Permission denied to get this file');
+	}
+
+	public function getPath() {
+		return $this->root->getFileInfo()->getInternalPath() . '/' . $this->partInfo['PartNumber'];
+	}
+
+	/**
+	 * @inheritdoc
+	 */
+	public function getContentType() {
+		return 'application/octet-stream';
+	}
+
+	/**
+	 * @inheritdoc
+	 */
+	public function getETag() {
+		return $this->partInfo['ETag'];
+	}
+
+	/**
+	 * @inheritdoc
+	 */
+	public function getSize() {
+		return $this->partInfo['Size'];
+	}
+
+	/**
+	 * @inheritdoc
+	 */
+	public function delete() {
+		$this->root->delete();
+	}
+
+	/**
+	 * @inheritdoc
+	 */
+	public function getName() {
+		return $this->partInfo['PartNumber'];
+	}
+
+	/**
+	 * @inheritdoc
+	 */
+	public function setName($name) {
+		throw new Forbidden('Permission denied to rename this file');
+	}
+
+	/**
+	 * @inheritdoc
+	 */
+	public function getLastModified() {
+		return $this->partInfo['LastModified'];
+	}
+}
diff --git a/apps/dav/lib/Upload/UploadFile.php b/apps/dav/lib/Upload/UploadFile.php
index 023d17955c1..efe1385c8ce 100644
--- a/apps/dav/lib/Upload/UploadFile.php
+++ b/apps/dav/lib/Upload/UploadFile.php
@@ -44,6 +44,10 @@ class UploadFile implements IFile {
 		return $this->file->get();
 	}
 
+	public function getId() {
+		return $this->file->getId();
+	}
+
 	public function getContentType() {
 		return $this->file->getContentType();
 	}
@@ -75,4 +79,16 @@ class UploadFile implements IFile {
 	public function getLastModified() {
 		return $this->file->getLastModified();
 	}
+
+	public function getInternalPath(): string {
+		return $this->file->getInternalPath();
+	}
+
+	public function getFile(): File {
+		return $this->file;
+	}
+
+	public function getNode() {
+		return $this->file->getNode();
+	}
 }
diff --git a/apps/dav/lib/Upload/UploadFolder.php b/apps/dav/lib/Upload/UploadFolder.php
index bb7c494cee3..66c190d84d9 100644
--- a/apps/dav/lib/Upload/UploadFolder.php
+++ b/apps/dav/lib/Upload/UploadFolder.php
@@ -24,20 +24,25 @@
  */
 namespace OCA\DAV\Upload;
 
+use OC\Files\ObjectStore\ObjectStoreStorage;
 use OCA\DAV\Connector\Sabre\Directory;
+use OCP\Files\ObjectStore\IObjectStoreMultiPartUpload;
+use OCP\Files\Storage\IStorage;
 use Sabre\DAV\Exception\Forbidden;
 use Sabre\DAV\ICollection;
 
 class UploadFolder implements ICollection {
-
 	/** @var Directory */
 	private $node;
 	/** @var CleanupService */
 	private $cleanupService;
+	/** @var IStorage */
+	private $storage;
 
-	public function __construct(Directory $node, CleanupService $cleanupService) {
+	public function __construct(Directory $node, CleanupService $cleanupService, IStorage $storage) {
 		$this->node = $node;
 		$this->cleanupService = $cleanupService;
+		$this->storage = $storage;
 	}
 
 	public function createFile($name, $data = null) {
@@ -66,6 +71,23 @@ class UploadFolder implements ICollection {
 			$children[] = new UploadFile($child);
 		}
 
+		if ($this->storage->instanceOfStorage(ObjectStoreStorage::class)) {
+			/** @var ObjectStoreStorage $storage */
+			$objectStore = $this->storage->getObjectStore();
+			if ($objectStore instanceof IObjectStoreMultiPartUpload) {
+				$cache = \OC::$server->getMemCacheFactory()->createDistributed(ChunkingV2Plugin::CACHE_KEY);
+				$uploadSession = $cache->get($this->getName());
+				if ($uploadSession) {
+					$uploadId = $uploadSession[ChunkingV2Plugin::UPLOAD_ID];
+					$id = $uploadSession[ChunkingV2Plugin::UPLOAD_TARGET_ID];
+					$parts = $objectStore->getMultipartUploads($this->storage->getURN($id), $uploadId);
+					foreach ($parts as $part) {
+						$children[] = new PartFile($this->node, $part);
+					}
+				}
+			}
+		}
+
 		return $children;
 	}
 
@@ -94,4 +116,8 @@ class UploadFolder implements ICollection {
 	public function getLastModified() {
 		return $this->node->getLastModified();
 	}
+
+	public function getStorage() {
+		return $this->storage;
+	}
 }
diff --git a/apps/dav/lib/Upload/UploadHome.php b/apps/dav/lib/Upload/UploadHome.php
index 35d47b6a82a..6664d8c85b6 100644
--- a/apps/dav/lib/Upload/UploadHome.php
+++ b/apps/dav/lib/Upload/UploadHome.php
@@ -32,7 +32,6 @@ use Sabre\DAV\Exception\Forbidden;
 use Sabre\DAV\ICollection;
 
 class UploadHome implements ICollection {
-
 	/** @var array */
 	private $principalInfo;
 	/** @var CleanupService */
@@ -55,12 +54,12 @@ class UploadHome implements ICollection {
 	}
 
 	public function getChild($name): UploadFolder {
-		return new UploadFolder($this->impl()->getChild($name), $this->cleanupService);
+		return new UploadFolder($this->impl()->getChild($name), $this->cleanupService, $this->getStorage());
 	}
 
 	public function getChildren(): array {
 		return array_map(function ($node) {
-			return new UploadFolder($node, $this->cleanupService);
+			return new UploadFolder($node, $this->cleanupService, $this->getStorage());
 		}, $this->impl()->getChildren());
 	}
 
@@ -89,14 +88,24 @@ class UploadHome implements ICollection {
 	 * @return Directory
 	 */
 	private function impl() {
+		$view = $this->getView();
+		$rootInfo = $view->getFileInfo('');
+		return new Directory($view, $rootInfo);
+	}
+
+	private function getView() {
 		$rootView = new View();
 		$user = \OC::$server->getUserSession()->getUser();
 		Filesystem::initMountPoints($user->getUID());
 		if (!$rootView->file_exists('/' . $user->getUID() . '/uploads')) {
 			$rootView->mkdir('/' . $user->getUID() . '/uploads');
 		}
-		$view = new View('/' . $user->getUID() . '/uploads');
-		$rootInfo = $view->getFileInfo('');
-		return new Directory($view, $rootInfo);
+		return new View('/' . $user->getUID() . '/uploads');
+	}
+
+	private function getStorage() {
+		$view = $this->getView();
+		$storage = $view->getFileInfo('')->getStorage();
+		return $storage;
 	}
 }