common/util/src/main/java/org/opendaylight/yangtools/util/xml/UntrustedXML.java

   1 /*
   2  * Copyright (c) 2016 Cisco Systems, Inc. and others.  All rights reserved.
   3  *
   4  * This program and the accompanying materials are made available under the
   5  * terms of the Eclipse Public License v1.0 which accompanies this distribution,
   6  * and is available at http://www.eclipse.org/legal/epl-v10.html
   7  */
   8 package org.opendaylight.yangtools.util.xml;
   9
  10 import com.google.common.annotations.Beta;
  11 import java.io.InputStream;
  12 import java.io.Reader;
  13 import java.nio.charset.Charset;
  14 import javax.annotation.Nonnull;
  15 import javax.xml.XMLConstants;
  16 import javax.xml.parsers.DocumentBuilder;
  17 import javax.xml.parsers.DocumentBuilderFactory;
  18 import javax.xml.parsers.ParserConfigurationException;
  19 import javax.xml.parsers.SAXParser;
  20 import javax.xml.parsers.SAXParserFactory;
  21 import javax.xml.stream.XMLInputFactory;
  22 import javax.xml.stream.XMLStreamException;
  23 import javax.xml.stream.XMLStreamReader;
  24 import org.xml.sax.SAXException;
  25
  26 /**
  27  * Set of utility methods for instantiating parser that deal with untrusted XML sources.
  28  *
  29  * @author Robert Varga
  30  */
  31 @Beta
  32 public final class UntrustedXML {
  33     private static final DocumentBuilderFactory DBF;
  34     static {
  35         final DocumentBuilderFactory f = DocumentBuilderFactory.newInstance();
  36         f.setCoalescing(true);
  37         f.setExpandEntityReferences(false);
  38         f.setIgnoringElementContentWhitespace(true);
  39         f.setIgnoringComments(true);
  40         f.setNamespaceAware(true);
  41         f.setXIncludeAware(false);
  42         try {
  43             f.setFeature(XMLConstants.FEATURE_SECURE_PROCESSING, true);
  44             f.setFeature("http://apache.org/xml/features/disallow-doctype-decl", true);
  45             f.setFeature("http://apache.org/xml/features/nonvalidating/load-external-dtd", false);
  46             f.setFeature("http://xml.org/sax/features/external-general-entities", false);
  47             f.setFeature("http://xml.org/sax/features/external-parameter-entities", false);
  48         } catch (final ParserConfigurationException e) {
  49             throw new ExceptionInInitializerError(e);
  50         }
  51         DBF = f;
  52     }
  53
  54     private static final SAXParserFactory SPF;
  55     static {
  56         final SAXParserFactory f = SAXParserFactory.newInstance();
  57         f.setNamespaceAware(true);
  58         f.setXIncludeAware(false);
  59         try {
  60             f.setFeature(XMLConstants.FEATURE_SECURE_PROCESSING, true);
  61             f.setFeature("http://apache.org/xml/features/disallow-doctype-decl", true);
  62             f.setFeature("http://apache.org/xml/features/nonvalidating/load-external-dtd", false);
  63             f.setFeature("http://xml.org/sax/features/external-general-entities", false);
  64             f.setFeature("http://xml.org/sax/features/external-parameter-entities", false);
  65         } catch (final Exception e) {
  66             throw new ExceptionInInitializerError(e);
  67         }
  68
  69         SPF = f;
  70     }
  71
  72     private static final XMLInputFactory XIF;
  73     static {
  74         final XMLInputFactory f = XMLInputFactory.newInstance();
  75
  76         f.setProperty(XMLInputFactory.IS_COALESCING, Boolean.TRUE);
  77         f.setProperty(XMLInputFactory.IS_NAMESPACE_AWARE, Boolean.TRUE);
  78         f.setProperty(XMLInputFactory.IS_SUPPORTING_EXTERNAL_ENTITIES, Boolean.FALSE);
  79         f.setProperty(XMLInputFactory.SUPPORT_DTD, Boolean.FALSE);
  80
  81         XIF = f;
  82     }
  83
  84
  85     /**
  86      * Create a new {@link DocumentBuilder} for dealing with untrusted XML data. This method is equivalent to
  87      * {@link DocumentBuilderFactory#newDocumentBuilder()}, except it does not throw a checked exception.
  88      *
  89      * @return A new DocumentBuilder
  90      * @throws UnsupportedOperationException if the runtime fails to instantiate a good enough builder
  91      */
  92     public static @Nonnull DocumentBuilder newDocumentBuilder() {
  93         try {
  94             return DBF.newDocumentBuilder();
  95         } catch (ParserConfigurationException e) {
  96             throw new UnsupportedOperationException("Failed to instantiate a DocumentBuilder", e);
  97         }
  98     }
  99
 100     /**
 101      * Create a new {@link SAXParser} for dealing with untrusted XML data. This method is equivalent to
 102      * {@link SAXParserFactory#newSAXParser()}, except it does not throw a checked exception.
 103      *
 104      * @return A new SAXParser
 105      * @throws UnsupportedOperationException if the runtime fails to instantiate a good enough builder
 106      */
 107     public static @Nonnull SAXParser newSAXParser() {
 108         try {
 109             return SPF.newSAXParser();
 110         } catch (ParserConfigurationException | SAXException e) {
 111             throw new UnsupportedOperationException("Failed to instantiate a SAXParser", e);
 112         }
 113     }
 114
 115     /**
 116      * Create a new {@link XMLStreamReader} for dealing with untrusted XML data. This method is equivalent to
 117      * {@link XMLInputFactory#createXMLStreamReader(InputStream)}.
 118      *
 119      * @return A new XMLStreamReader
 120      * @throws XMLStreamException when the underlying factory throws it
 121      */
 122     public static @Nonnull XMLStreamReader createXMLStreamReader(final InputStream stream) throws XMLStreamException {
 123         return XIF.createXMLStreamReader(stream);
 124     }
 125
 126     /**
 127      * Create a new {@link XMLStreamReader} for dealing with untrusted XML data. This method is equivalent to
 128      * {@link XMLInputFactory#createXMLStreamReader(InputStream, String)}, except it takes an explict charset argument.
 129      *
 130      * @return A new XMLStreamReader
 131      * @throws XMLStreamException when the underlying factory throws it
 132      */
 133     public static @Nonnull XMLStreamReader createXMLStreamReader(final InputStream stream, final Charset charset)
 134             throws XMLStreamException {
 135         return XIF.createXMLStreamReader(stream, charset.name());
 136     }
 137
 138     /**
 139      * Create a new {@link XMLStreamReader} for dealing with untrusted XML data. This method is equivalent to
 140      * {@link XMLInputFactory#createXMLStreamReader(Reader)}.
 141      *
 142      * @return A new XMLStreamReader
 143      * @throws XMLStreamException when the underlying factory throws it
 144      */
 145     public static @Nonnull XMLStreamReader createXMLStreamReader(final Reader reader) throws XMLStreamException {
 146         return XIF.createXMLStreamReader(reader);
 147     }
 148 }