| /* ==================================================================== |
| 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.poi.util; |
| |
| import java.io.IOException; |
| import java.io.StringReader; |
| import java.lang.reflect.Method; |
| import java.util.concurrent.TimeUnit; |
| |
| import javax.xml.XMLConstants; |
| import javax.xml.parsers.ParserConfigurationException; |
| import javax.xml.parsers.SAXParserFactory; |
| |
| import org.xml.sax.EntityResolver; |
| import org.xml.sax.InputSource; |
| import org.xml.sax.SAXException; |
| import org.xml.sax.XMLReader; |
| |
| |
| /** |
| * Provides handy methods for working with SAX parsers and readers |
| */ |
| public final class SAXHelper { |
| private static final POILogger logger = POILogFactory.getLogger(SAXHelper.class); |
| private static long lastLog; |
| |
| private SAXHelper() {} |
| |
| /** |
| * Creates a new SAX XMLReader, with sensible defaults |
| */ |
| public static synchronized XMLReader newXMLReader() throws SAXException, ParserConfigurationException { |
| XMLReader xmlReader = saxFactory.newSAXParser().getXMLReader(); |
| xmlReader.setEntityResolver(IGNORING_ENTITY_RESOLVER); |
| trySetSAXFeature(xmlReader, XMLConstants.FEATURE_SECURE_PROCESSING); |
| trySetXercesSecurityManager(xmlReader); |
| return xmlReader; |
| } |
| |
| static final EntityResolver IGNORING_ENTITY_RESOLVER = new EntityResolver() { |
| @Override |
| public InputSource resolveEntity(String publicId, String systemId) |
| throws SAXException, IOException { |
| return new InputSource(new StringReader("")); |
| } |
| }; |
| |
| private static final SAXParserFactory saxFactory; |
| static { |
| try { |
| saxFactory = SAXParserFactory.newInstance(); |
| saxFactory.setValidating(false); |
| saxFactory.setNamespaceAware(true); |
| } catch (RuntimeException re) { |
| logger.log(POILogger.WARN, "Failed to create SAXParserFactory", re); |
| throw re; |
| } catch (Exception e) { |
| logger.log(POILogger.WARN, "Failed to create SAXParserFactory", e); |
| throw new RuntimeException("Failed to create SAXParserFactory", e); |
| } catch (Error e) { |
| // catches NoClassDefFoundError, which may be due to a local class path issue |
| // This may occur if the code is run inside a web container |
| // or a restricted JVM |
| // See bug 61170: https://bz.apache.org/bugzilla/show_bug.cgi?id=61170 |
| logger.log(POILogger.WARN, "Failed to create SAXParserFactory", e); |
| throw e; |
| } |
| } |
| |
| private static void trySetSAXFeature(XMLReader xmlReader, String feature) { |
| try { |
| xmlReader.setFeature(feature, true); |
| } catch (Exception e) { |
| logger.log(POILogger.WARN, "SAX Feature unsupported", feature, e); |
| } catch (AbstractMethodError ame) { |
| logger.log(POILogger.WARN, "Cannot set SAX feature because outdated XML parser in classpath", feature, ame); |
| } |
| } |
| |
| private static void trySetXercesSecurityManager(XMLReader xmlReader) { |
| // Try built-in JVM one first, standalone if not |
| for (String securityManagerClassName : new String[] { |
| "com.sun.org.apache.xerces.internal.util.SecurityManager", |
| "org.apache.xerces.util.SecurityManager" |
| }) { |
| try { |
| Object mgr = Class.forName(securityManagerClassName).newInstance(); |
| Method setLimit = mgr.getClass().getMethod("setEntityExpansionLimit", Integer.TYPE); |
| setLimit.invoke(mgr, 4096); |
| xmlReader.setProperty("http://apache.org/xml/properties/security-manager", mgr); |
| // Stop once one can be setup without error |
| return; |
| } catch (Throwable e) { // NOSONAR - also catch things like NoClassDefError here |
| // throttle the log somewhat as it can spam the log otherwise |
| if(System.currentTimeMillis() > lastLog + TimeUnit.MINUTES.toMillis(5)) { |
| logger.log(POILogger.WARN, "SAX Security Manager could not be setup [log suppressed for 5 minutes]", e); |
| lastLog = System.currentTimeMillis(); |
| } |
| } |
| } |
| } |
| } |