Remove invalid share items from result when missing group membership

Group shares usually have subshare entries for every user. In some
situations it can happen that the user was removed from the group but
the subshare entries still exist.

This fix makes sure that such subshare entries are not returned any more
as the user isn't in the group any more.

lib/private/share/share.php

@@ -1908,6 +1908,12 @@ class Share extends Constants {
 				$items = array_merge($items, $collectionItems);
 			}
 
+			// filter out invalid items, these can appear when subshare entries exist
+			// for a group in which the requested user isn't a member any more
+			$items = array_filter($items, function($item) {
+				return $item['share_type'] !== self::$shareTypeGroupUserUnique;
+			});
+
 			return self::formatResult($items, $column, $backend, $format, $parameters);
 		} elseif ($includeCollections && $collectionTypes && in_array('folder', $collectionTypes)) {
 			// FIXME: Thats a dirty hack to improve file sharing performance,

tests/lib/share/share.php

@@ -898,6 +898,43 @@ class Test_Share extends \Test\TestCase {
 		$this->assertEmpty($expected, 'did not found all expected values');
 	}
 
+	public function testGetShareSubItemsWhenUserNotInGroup() {
+		OCP\Share::shareItem('test', 'test.txt', OCP\Share::SHARE_TYPE_GROUP, $this->group1, \OCP\Constants::PERMISSION_READ);
+
+		$result = \OCP\Share::getItemsSharedWithUser('test', $this->user2);
+		$this->assertCount(1, $result);
+
+		$groupShareId = array_keys($result)[0];
+
+		// remove user from group
+		$userObject = \OC::$server->getUserManager()->get($this->user2);
+		\OC::$server->getGroupManager()->get($this->group1)->removeUser($userObject);
+
+		$result = \OCP\Share::getItemsSharedWithUser('test', $this->user2);
+		$this->assertCount(0, $result);
+
+		// test with buggy data
+		$qb = \OC::$server->getDatabaseConnection()->getQueryBuilder();
+		$qb->insert('share')
+			->values([
+				'share_type' => $qb->expr()->literal(2), // group sub-share
+				'share_with' => $qb->expr()->literal($this->user2),
+				'parent' => $qb->expr()->literal($groupShareId),
+				'uid_owner' => $qb->expr()->literal($this->user1),
+				'item_type' => $qb->expr()->literal('test'),
+				'item_source' => $qb->expr()->literal('test.txt'),
+				'item_target' => $qb->expr()->literal('test.txt'),
+				'file_target' => $qb->expr()->literal('test2.txt'),
+				'permissions' => $qb->expr()->literal(1),
+				'stime' => $qb->expr()->literal(time()),
+			])->execute();
+
+		$result = \OCP\Share::getItemsSharedWithUser('test', $this->user2);
+		$this->assertCount(0, $result);
+
+		$qb->delete('share')->execute();
+	}
+
 	public function testShareItemWithLink() {
 		OC_User::setUserId($this->user1);
 		$token = OCP\Share::shareItem('test', 'test.txt', OCP\Share::SHARE_TYPE_LINK, null, \OCP\Constants::PERMISSION_READ);