fix(OC_Helper): properly calculate quota of shared storages

- resolves #55659

First we need to properly handle shared storages,
because there the quota is the quota of the user who owns the nodes,
not the user who shared the nodes.

Second if no user can be fetched then we cannot get the global storage
info, thus in this case (public share?) we need to safe-guard.

Signed-off-by: Ferdinand Thiessen <opensource@fthiessen.de>

Author: susnux

build/psalm-baseline.xml

@@ -4207,9 +4207,6 @@
     <InternalMethod>
       <code><![CDATA[getAbsolutePath]]></code>
     </InternalMethod>
-    <UndefinedInterfaceMethod>
-      <code><![CDATA[getQuota]]></code>
-    </UndefinedInterfaceMethod>
   </file>
   <file src="lib/private/legacy/OC_User.php">
     <UndefinedClass>

lib/private/legacy/OC_Helper.php

@@ -8,6 +8,10 @@
 use bantu\IniGetWrapper\IniGetWrapper;
 use OC\Files\FilenameValidator;
 use OC\Files\Filesystem;
+use OC\Files\ObjectStore\HomeObjectStoreStorage;
+use OC\Files\Storage\Home;
+use OC\Files\Storage\Wrapper\Quota;
+use OCP\Files\FileInfo;
 use OCP\Files\Mount\IMountPoint;
 use OCP\IBinaryFinder;
 use OCP\ICacheFactory;
@@ -181,24 +185,31 @@ public static function getStorageInfo($path, $rootInfo = null, $includeMountPoin
 			self::$quotaIncludeExternalStorage = false;
 		}
 		if (self::$quotaIncludeExternalStorage) {
-			if ($storage->instanceOfStorage('\OC\Files\Storage\Home')
+			if ($storage->instanceOfStorage(ISharedStorage::class)) {
+				// we must use the shared nodes owner,
+				// because if user A shared a file with user B and B shares this again,
+				// then the share initiator is user B but the quota that this counts in is user A's quota.
+				/** @var ISharedStorage $storage */
+				$user = $storage->getShare()->getNode()->getOwner();
+			} elseif (
+				$storage->instanceOfStorage('\OC\Files\Storage\Home')
 				|| $storage->instanceOfStorage('\OC\Files\ObjectStore\HomeObjectStoreStorage')
 			) {
-				/** @var \OC\Files\Storage\Home $storage */
+				/** @var Home|HomeObjectStoreStorage $storage */
 				$user = $storage->getUser();
 			} else {
 				$user = \OC::$server->getUserSession()->getUser();
 			}
-			$quota = $user?->getQuotaBytes() ?? \OCP\Files\FileInfo::SPACE_UNKNOWN;
-			if ($quota !== \OCP\Files\FileInfo::SPACE_UNLIMITED) {
+			$quota = $user?->getQuotaBytes() ?? FileInfo::SPACE_UNKNOWN;
+			if ($user !== null && $quota !== FileInfo::SPACE_UNLIMITED) {
 				// always get free space / total space from root + mount points
 				return self::getGlobalStorageInfo($quota, $user, $mount);
 			}
 		}
 
 		// TODO: need a better way to get total space from storage
 		if ($sourceStorage->instanceOfStorage('\OC\Files\Storage\Wrapper\Quota')) {
-			/** @var \OC\Files\Storage\Wrapper\Quota $storage */
+			/** @var Quota $sourceStorage */
 			$quota = $sourceStorage->getQuota();
 		}
 		try {