JCR-3883: Jackrabbit WebDAV bundle susceptible to XXE/XEE attack (CVE…

…-2015-1833) (ported to 2.4)

git-svn-id: https://svn.apache.org/repos/asf/jackrabbit/branches/2.4@1680798 13f79535-47bb-0310-9956-ffa450edef68

jackrabbit-webdav/src/main/java/org/apache/jackrabbit/webdav/xml/DavDocumentBuilderFactory.java

@@ -0,0 +1,87 @@
+/*
+ * 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.jackrabbit.webdav.xml;
+
+import java.io.IOException;
+
+import javax.xml.XMLConstants;
+import javax.xml.parsers.DocumentBuilder;
+import javax.xml.parsers.DocumentBuilderFactory;
+import javax.xml.parsers.ParserConfigurationException;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.xml.sax.EntityResolver;
+import org.xml.sax.InputSource;
+import org.xml.sax.helpers.DefaultHandler;
+
+/**
+ * Custom {@link DocumentBuilderFactory} extended for use in WebDAV.
+ */
+public class DavDocumentBuilderFactory {
+
+    private static final Logger LOG = LoggerFactory.getLogger(DomUtil.class);
+
+    private final DocumentBuilderFactory DEFAULT_FACTORY = createFactory();
+
+    private DocumentBuilderFactory BUILDER_FACTORY = DEFAULT_FACTORY;
+
+    private DocumentBuilderFactory createFactory() {
+        DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
+        factory.setNamespaceAware(true);
+        factory.setIgnoringComments(true);
+        factory.setIgnoringElementContentWhitespace(true);
+        factory.setCoalescing(true);
+        try {
+            factory.setFeature(XMLConstants.FEATURE_SECURE_PROCESSING, true);
+        } catch (ParserConfigurationException e) {
+            LOG.warn("Secure XML processing is not supported", e);
+        } catch (AbstractMethodError e) {
+            LOG.warn("Secure XML processing is not supported", e);
+        }
+        return factory;
+    }
+
+    public void setFactory(DocumentBuilderFactory documentBuilderFactory) {
+        LOG.debug("DocumentBuilderFactory changed to: " + documentBuilderFactory);
+        BUILDER_FACTORY = documentBuilderFactory != null ? documentBuilderFactory : DEFAULT_FACTORY;
+    }
+
+    /**
+     * An entity resolver that does not allow external entity resolution. See
+     * RFC 4918, Section 20.6
+     */
+    private static final EntityResolver DEFAULT_ENTITY_RESOLVER = new EntityResolver() {
+        @Override
+        public InputSource resolveEntity(String publicId, String systemId) throws IOException {
+            LOG.debug("Resolution of external entities in XML payload not supported - publicId: " + publicId + ", systemId: "
+                    + systemId);
+            throw new IOException("This parser does not support resolution of external entities (publicId: " + publicId
+                    + ", systemId: " + systemId + ")");
+        }
+    };
+
+    public DocumentBuilder newDocumentBuilder() throws ParserConfigurationException {
+        DocumentBuilder db = BUILDER_FACTORY.newDocumentBuilder();
+        if (BUILDER_FACTORY == DEFAULT_FACTORY) {
+            // if this is the default factory: set the default entity resolver as well
+            db.setEntityResolver(DEFAULT_ENTITY_RESOLVER);
+        }
+        db.setErrorHandler(new DefaultHandler());
+        return db;
+    }
+}

jackrabbit-webdav/src/main/java/org/apache/jackrabbit/webdav/xml/DomUtil.java

@@ -28,9 +28,7 @@
 import org.w3c.dom.Text;
 import org.w3c.dom.NamedNodeMap;
 import org.xml.sax.SAXException;
-import org.xml.sax.helpers.DefaultHandler;
 
-import javax.xml.XMLConstants;
 import javax.xml.namespace.QName;
 import javax.xml.parsers.DocumentBuilder;
 import javax.xml.parsers.DocumentBuilderFactory;
@@ -56,26 +54,10 @@ public class DomUtil {
     private static Logger log = LoggerFactory.getLogger(DomUtil.class);
 
     /**
-     * Constant for <code>DocumentBuilderFactory</code> which is used
+     * Constant for <code>DavDocumentBuilderFactory</code> which is used
      * to create and parse DOM documents.
      */
-    private static DocumentBuilderFactory BUILDER_FACTORY = createFactory();
-
-    private static DocumentBuilderFactory createFactory() {
-        DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
-        factory.setNamespaceAware(true);
-        factory.setIgnoringComments(true);
-        factory.setIgnoringElementContentWhitespace(true);
-        factory.setCoalescing(true);
-        try {
-            factory.setFeature(XMLConstants.FEATURE_SECURE_PROCESSING, true);
-        } catch (ParserConfigurationException e) {
-            log.warn("Secure XML processing is not supported", e);
-        } catch (AbstractMethodError e) {
-            log.warn("Secure XML processing is not supported", e);
-        }
-        return factory;
-    }
+    private static final DavDocumentBuilderFactory BUILDER_FACTORY = new DavDocumentBuilderFactory();
 
     /**
      * Support the replacement of {@link #BUILDER_FACTORY}. This is useful
@@ -88,7 +70,7 @@ private static DocumentBuilderFactory createFactory() {
      */
     public static void setBuilderFactory(
             DocumentBuilderFactory documentBuilderFactory) {
-        BUILDER_FACTORY = documentBuilderFactory;
+        BUILDER_FACTORY.setFactory(documentBuilderFactory);
     }
 
     /**
@@ -119,11 +101,6 @@ public static Document createDocument()
     public static Document parseDocument(InputStream stream)
             throws ParserConfigurationException, SAXException, IOException {
         DocumentBuilder docBuilder = BUILDER_FACTORY.newDocumentBuilder();
-
-        // Set an error handler to prevent parsers from printing error messages
-        // to standard output!
-        docBuilder.setErrorHandler(new DefaultHandler());
-
         return docBuilder.parse(stream);
     }
 

jackrabbit-webdav/src/test/java/org/apache/jackrabbit/webdav/xml/ParserTest.java

@@ -0,0 +1,143 @@
+/*
+ * 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.jackrabbit.webdav.xml;
+
+import java.io.ByteArrayInputStream;
+import java.io.File;
+import java.io.FileOutputStream;
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.OutputStream;
+import java.io.UnsupportedEncodingException;
+
+import javax.xml.parsers.DocumentBuilder;
+import javax.xml.parsers.DocumentBuilderFactory;
+import javax.xml.parsers.ParserConfigurationException;
+
+import junit.framework.TestCase;
+
+import org.w3c.dom.Document;
+import org.w3c.dom.Element;
+import org.xml.sax.EntityResolver;
+import org.xml.sax.InputSource;
+import org.xml.sax.SAXException;
+
+public class ParserTest extends TestCase {
+
+    // see <http://en.wikipedia.org/wiki/Billion_laughs#Details>
+    public void testBillionLaughs() throws UnsupportedEncodingException {
+
+        String testBody = "<?xml version=\"1.0\"?>" + "<!DOCTYPE lolz [" + " <!ENTITY lol \"lol\">" + " <!ELEMENT lolz (#PCDATA)>"
+                + " <!ENTITY lol1 \"&lol;&lol;&lol;&lol;&lol;&lol;&lol;&lol;&lol;&lol;\">"
+                + " <!ENTITY lol2 \"&lol1;&lol1;&lol1;&lol1;&lol1;&lol1;&lol1;&lol1;&lol1;&lol1;\">"
+                + " <!ENTITY lol3 \"&lol2;&lol2;&lol2;&lol2;&lol2;&lol2;&lol2;&lol2;&lol2;&lol2;\">"
+                + " <!ENTITY lol4 \"&lol3;&lol3;&lol3;&lol3;&lol3;&lol3;&lol3;&lol3;&lol3;&lol3;\">"
+                + " <!ENTITY lol5 \"&lol4;&lol4;&lol4;&lol4;&lol4;&lol4;&lol4;&lol4;&lol4;&lol4;\">"
+                + " <!ENTITY lol6 \"&lol5;&lol5;&lol5;&lol5;&lol5;&lol5;&lol5;&lol5;&lol5;&lol5;\">"
+                + " <!ENTITY lol7 \"&lol6;&lol6;&lol6;&lol6;&lol6;&lol6;&lol6;&lol6;&lol6;&lol6;\">"
+                + " <!ENTITY lol8 \"&lol7;&lol7;&lol7;&lol7;&lol7;&lol7;&lol7;&lol7;&lol7;&lol7;\">"
+                + " <!ENTITY lol9 \"&lol8;&lol8;&lol8;&lol8;&lol8;&lol8;&lol8;&lol8;&lol8;&lol8;\">" + "]>" + "<lolz>&lol9;</lolz>";
+        InputStream is = new ByteArrayInputStream(testBody.getBytes("UTF-8"));
+
+        try {
+            DomUtil.parseDocument(is);
+            fail("parsing this document should cause an exception");
+        } catch (Exception expected) {
+        }
+    }
+
+    public void testExternalEntities() throws IOException {
+
+        String dname = "target";
+        String fname = "test.xml";
+
+        File f = new File(dname, fname);
+        OutputStream os = new FileOutputStream(f);
+        os.write("testdata".getBytes());
+        os.close();
+
+        String testBody = "<?xml version='1.0'?>\n<!DOCTYPE foo [" + " <!ENTITY test SYSTEM \"file:" + dname + "/" + fname + "\">"
+                + "]>\n<foo>&test;</foo>";
+        InputStream is = new ByteArrayInputStream(testBody.getBytes("UTF-8"));
+
+        try {
+            Document d = DomUtil.parseDocument(is);
+            Element root = d.getDocumentElement();
+            String text = DomUtil.getText(root);
+            fail("parsing this document should cause an exception, but the following external content was included: " + text);
+        } catch (Exception expected) {
+        }
+    }
+
+    public void testCustomEntityResolver() throws ParserConfigurationException, SAXException, IOException {
+
+        try {
+            DocumentBuilderFactory dbf = new DocumentBuilderFactory() {
+
+                DocumentBuilderFactory def = DocumentBuilderFactory.newInstance();
+
+                @Override
+                public void setFeature(String name, boolean value) throws ParserConfigurationException {
+                    def.setFeature(name, value);
+                }
+
+                @Override
+                public void setAttribute(String name, Object value) throws IllegalArgumentException {
+                    def.setAttribute(name, value);
+                }
+
+                @Override
+                public DocumentBuilder newDocumentBuilder() throws ParserConfigurationException {
+                    DocumentBuilder db = def.newDocumentBuilder();
+                    db.setEntityResolver(new EntityResolver() {
+                        @Override
+                        public InputSource resolveEntity(String publicId, String systemId) throws SAXException, IOException {
+                            if ("foo:test".equals(systemId)) {
+                                return new InputSource(new ByteArrayInputStream("foo&amp;bar".getBytes("UTF-8")));
+                            } else {
+                                return null;
+                            }
+                        }
+                    });
+                    return db;
+                }
+
+                @Override
+                public boolean getFeature(String name) throws ParserConfigurationException {
+                    return def.getFeature(name);
+                }
+
+                @Override
+                public Object getAttribute(String name) throws IllegalArgumentException {
+                    return def.getAttribute(name);
+                }
+            };
+
+            DomUtil.setBuilderFactory(dbf);
+            String testBody = "<?xml version='1.0'?>\n<!DOCTYPE foo [" + " <!ENTITY test SYSTEM \"foo:test\">"
+                    + "]>\n<foo>&test;</foo>";
+            InputStream is = new ByteArrayInputStream(testBody.getBytes("UTF-8"));
+
+            Document d = DomUtil.parseDocument(is);
+            Element root = d.getDocumentElement();
+            String text = DomUtil.getText(root);
+            assertEquals("custom entity resolver apparently not called", "foo&bar", text);
+        } finally {
+            DomUtil.setBuilderFactory(null);
+        }
+    }
+}

jackrabbit-webdav/src/test/java/org/apache/jackrabbit/webdav/xml/TestAll.java

@@ -33,6 +33,7 @@ public static Test suite() {
         TestSuite suite = new TestSuite("org.apache.jackrabbit.webdav.xml tests");
 
         suite.addTestSuite(NamespaceTest.class);
+        suite.addTestSuite(ParserTest.class);
 
         return suite;
     }