[stable21] fix(apps): Fix loading info.xml file

lib/base.php

@@ -545,6 +545,11 @@
 	}
 
 	public static function init() {
+		// prevent any XML processing from loading external entities
+		libxml_set_external_entity_loader(static function () {
+			return null;
+		});
+
 		// calculate the root directories
 		OC::$SERVERROOT = str_replace("\\", '/', substr(__DIR__, 0, -4));
 

lib/private/App/CodeChecker/DatabaseSchemaChecker.php

@@ -42,7 +42,7 @@
 
 		libxml_use_internal_errors(true);
 		$loadEntities = libxml_disable_entity_loader(false);
-		$xml = simplexml_load_file($appPath . '/appinfo/database.xml');
+		$xml = simplexml_load_string(file_get_contents($appPath . '/appinfo/database.xml'));
 		libxml_disable_entity_loader($loadEntities);
 
 

lib/private/App/CodeChecker/InfoChecker.php

@@ -44,6 +44,14 @@
 			throw new \RuntimeException("No app with given id <$appId> known.");
 		}
 
+		libxml_set_external_entity_loader(static function ($public, $system, $context) {
+			if ($system === \OC::$SERVERROOT . '/resources/app-info.xsd'
+				|| \OC::$SERVERROOT . '/resources/app-info-shipped.xsd') {
+				return $system;
+			}
+			return null;
+		});
+
 		$xml = new \DOMDocument();
 		$xml->load($appPath . '/appinfo/info.xml');
 
@@ -68,6 +76,10 @@
 			}
 		}
 
+		libxml_set_external_entity_loader(static function () {
+			return null;
+		});
+
 		return $errors;
 	}
 

lib/private/App/InfoParser.php

@@ -33,7 +33,7 @@
 
 use OCP\ICache;
 use function libxml_disable_entity_loader;
-use function simplexml_load_file;
+use function simplexml_load_string;
 
 class InfoParser {
 	/** @var \OCP\ICache|null */
@@ -65,10 +65,10 @@
 		libxml_use_internal_errors(true);
 		if ((PHP_VERSION_ID < 80000)) {
 			$loadEntities = libxml_disable_entity_loader(false);
-			$xml = simplexml_load_file($file);
+			$xml = simplexml_load_string(file_get_contents($file));
 			libxml_disable_entity_loader($loadEntities);
 		} else {
-			$xml = simplexml_load_file($file);
+			$xml = simplexml_load_string(file_get_contents($file));
 		}
 
 		if ($xml === false) {

lib/private/DB/MDB2SchemaReader.php

@@ -67,7 +67,7 @@
 	 */
 	public function loadSchemaFromFile($file, Schema $schema) {
 		$loadEntities = libxml_disable_entity_loader(false);
-		$xml = simplexml_load_file($file);
+		$xml = simplexml_load_string(file_get_contents($file));
 		libxml_disable_entity_loader($loadEntities);
 		foreach ($xml->children() as $child) {
 			/**

lib/private/Installer.php

@@ -344,10 +344,10 @@
 						// Check if appinfo/info.xml has the same app ID as well
 						if ((PHP_VERSION_ID < 80000)) {
 							$loadEntities = libxml_disable_entity_loader(false);
-							$xml = simplexml_load_file($extractDir . '/' . $folders[0] . '/appinfo/info.xml');
+							$xml = simplexml_load_string(file_get_contents($extractDir . '/' . $folders[0] . '/appinfo/info.xml'));
 							libxml_disable_entity_loader($loadEntities);
 						} else {
-							$xml = simplexml_load_file($extractDir . '/' . $folders[0] . '/appinfo/info.xml');
+							$xml = simplexml_load_string(file_get_contents($extractDir . '/' . $folders[0] . '/appinfo/info.xml'));
 						}
 						if ((string)$xml->id !== $appId) {
 							throw new \Exception(