Properly catch whether a share is `null`

Despite it's PHPDoc the function might return `null` which was not properly catched and thus in some situations the share was resolved to the sharing users root directory.

To test this perform the following steps:

* Share file in owncloud 7 (7.0.4.2)
* Delete the parent folder of the shared file
* The share stays is in the DB and the share via the sharelink is inaccessible. (which is good)
* Upgrade to owncloud 8 (8.0.2) (This step is crucial. The bug is not reproduceable without upgrading from 7 to 8. It seems like the old tokens are handled different than the newer ones)
* Optional Step: Logout, Reset Browser Session, etc.
* Access the share via the old share url: almost empty page, but there is a dowload button which adds a "/download" to the URL.
* Upon clicking, a download.zip is downloaded which contains EVERYTHING from the owncloud directory (of the user who shared the file)
* No exception is thrown and no error is logged.

This will add a check whether the share is a valid one and also adds unit tests to prevent further regressions in the future. Needs to be backported to ownCloud 8.

Adding a proper clean-up of the orphaned shares is out-of-scope and would probably require some kind of FK or so.

Fixes https://github.com/owncloud/core/issues/15097

1 files changed, 4 insertions, 1 deletions

diff --git a/apps/files_sharing/application.php b/apps/files_sharing/application.php
index 3302848106f..e23960cf2bb 100644
--- a/apps/files_sharing/application.php
+++ b/apps/files_sharing/application.php
@@ -42,7 +42,7 @@ class Application extends App {
 				$server->getAppConfig(),
 				$server->getConfig(),
 				$c->query('URLGenerator'),
-				$server->getUserManager(),
+				$c->query('UserManager'),
 				$server->getLogger(),
 				$server->getActivityManager()
 			);
@@ -65,6 +65,9 @@ class Application extends App {
 		$container->registerService('URLGenerator', function(SimpleContainer $c) use ($server){
 			return $server->getUrlGenerator();
 		});
+		$container->registerService('UserManager', function(SimpleContainer $c) use ($server){
+			return $server->getUserManager();
+		});
 		$container->registerService('IsIncomingShareEnabled', function(SimpleContainer $c) {
 			return Helper::isIncomingServer2serverShareEnabled();
 		});