alopresto commented on a change in pull request #3507: NIFI-6301 - Added a SafeXMLConfiguration which disables XML DTDs whic… URL: https://github.com/apache/nifi/pull/3507#discussion_r289156539
########## File path: nifi-commons/nifi-security-utils/src/main/java/org/apache/nifi/security/xml/SafeXMLConfiguration.java ########## @@ -0,0 +1,154 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one or more + * contributor license agreements. See the NOTICE file distributed with + * this work for additional information regarding copyright ownership. + * The ASF licenses this file to You under the Apache License, Version 2.0 + * (the "License"); you may not use this file except in compliance with + * the License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ +package org.apache.nifi.security.xml; + +import org.apache.commons.configuration2.HierarchicalConfiguration; +import org.apache.commons.configuration2.XMLConfiguration; +import org.apache.commons.configuration2.ex.ConfigurationException; +import org.apache.commons.configuration2.io.FileLocator; +import org.apache.commons.configuration2.tree.ImmutableNode; +import org.xml.sax.SAXException; +import org.xml.sax.SAXParseException; +import org.xml.sax.helpers.DefaultHandler; + +import javax.xml.parsers.DocumentBuilder; +import javax.xml.parsers.DocumentBuilderFactory; +import javax.xml.parsers.ParserConfigurationException; +import java.io.IOException; +import java.io.InputStream; +import java.io.Reader; + +/** + * For security reasons, this class overrides the Apache commons 'XMLConfiguration' class to disable processing of XML external entity (XXE) declarations. + * This class should be used in all cases where an XML configuration file will be used by NiFi. It is currently used by the XMLFileLookupService. + */ +public class SafeXMLConfiguration extends XMLConfiguration { + + // Schema Langauge key for the parser + private static final String JAXP_SCHEMA_LANGUAGE = + "http://java.sun.com/xml/jaxp/properties/schemaLanguage";; + + // Schema Language for the parser + private static final String W3C_XML_SCHEMA = + "http://www.w3.org/2001/XMLSchema";; + + // These features are used to disable processing external entities in the DocumentBuilderFactory to protect against XXE attacks + private static final String DISALLOW_DOCTYPES = "http://apache.org/xml/features/disallow-doctype-decl";; + private static final String ALLOW_EXTERNAL_GENERAL_ENTITIES = "http://xml.org/sax/features/external-general-entities";; + private static final String ALLOW_EXTERNAL_PARAM_ENTITIES = "http://xml.org/sax/features/external-parameter-entities";; + private static final String ALLOW_EXTERNAL_DTD = "http://apache.org/xml/features/nonvalidating/load-external-dtd";; + + private static final String XXE_ERROR_MESSAGE = "XML configuration file contained an external entity. To eliminate XXE vulnerabilities, NiFi has external entity processing disabled."; + + @Override + public void initFileLocator(FileLocator loc) { Review comment: Moving public method below constructors. ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: [email protected] With regards, Apache Git Services
