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Apache XML Security for Java supports XML-Signature Syntax and Processing,
W3C Recommendation 12 February 2002, and XML Encryption Syntax and
Processing, W3C Recommendation 10 December 2002. As of version 1.4,
the library supports the standard Java API JSR-105: XML Digital Signature APIs.
/**
* 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.xml.security.utils;
import java.lang.reflect.Constructor;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import javax.xml.transform.ErrorListener;
import javax.xml.transform.SourceLocator;
import javax.xml.transform.TransformerException;
import org.apache.xml.security.transforms.implementations.FuncHere;
import org.apache.xml.utils.PrefixResolver;
import org.apache.xml.utils.PrefixResolverDefault;
import org.apache.xpath.Expression;
import org.apache.xpath.XPath;
import org.apache.xpath.XPathContext;
import org.apache.xpath.compiler.FunctionTable;
import org.apache.xpath.objects.XObject;
import org.w3c.dom.Document;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
/**
* An implementation of XPathAPI using Xalan. This supports the "here()" function defined in the digital
* signature spec.
*/
class XalanXPathAPI implements XPathAPI {
private static final org.slf4j.Logger LOG =
org.slf4j.LoggerFactory.getLogger(XalanXPathAPI.class);
private String xpathStr;
private XPath xpath;
private static FunctionTable funcTable;
private static boolean installed;
private XPathContext context;
static {
fixupFunctionTable();
}
/**
* Use an XPath string to select a nodelist.
* XPath namespace prefixes are resolved from the namespaceNode.
*
* @param contextNode The node to start searching from.
* @param xpathnode
* @param str
* @param namespaceNode The node from which prefixes in the XPath will be resolved to namespaces.
* @return A NodeIterator, should never be null.
*
* @throws TransformerException
*/
public NodeList selectNodeList(
Node contextNode, Node xpathnode, String str, Node namespaceNode
) throws TransformerException {
// Execute the XPath, and have it return the result
XObject list = eval(contextNode, xpathnode, str, namespaceNode);
// Return a NodeList.
return list.nodelist();
}
/**
* Evaluate an XPath string and return true if the output is to be included or not.
* @param contextNode The node to start searching from.
* @param xpathnode The XPath node
* @param str The XPath expression
* @param namespaceNode The node from which prefixes in the XPath will be resolved to namespaces.
*/
public boolean evaluate(Node contextNode, Node xpathnode, String str, Node namespaceNode)
throws TransformerException {
XObject object = eval(contextNode, xpathnode, str, namespaceNode);
return object.bool();
}
/**
* Clear any context information from this object
*/
public void clear() {
xpathStr = null;
xpath = null;
context = null;
}
public static boolean isInstalled() {
return installed;
}
private XObject eval(Node contextNode, Node xpathnode, String str, Node namespaceNode)
throws TransformerException {
if (context == null) {
context = new XPathContext(xpathnode);
context.setSecureProcessing(true);
}
// Create an object to resolve namespace prefixes.
// XPath namespaces are resolved from the input context node's document element
// if it is a root node, or else the current context node (for lack of a better
// resolution space, given the simplicity of this sample code).
Node resolverNode =
(namespaceNode.getNodeType() == Node.DOCUMENT_NODE)
? ((Document) namespaceNode).getDocumentElement() : namespaceNode;
PrefixResolverDefault prefixResolver = new PrefixResolverDefault(resolverNode);
if (!str.equals(xpathStr)) {
if (str.indexOf("here()") > 0) {
context.reset();
}
xpath = createXPath(str, prefixResolver);
xpathStr = str;
}
// Execute the XPath, and have it return the result
int ctxtNode = context.getDTMHandleFromNode(contextNode);
return xpath.execute(context, ctxtNode, prefixResolver);
}
private XPath createXPath(String str, PrefixResolver prefixResolver) throws TransformerException {
XPath xpath = null;
Class[] classes = new Class[]{String.class, SourceLocator.class, PrefixResolver.class, int.class,
ErrorListener.class, FunctionTable.class};
Object[] objects =
new Object[]{str, null, prefixResolver, XPath.SELECT, null, funcTable};
try {
Constructor constructor = XPath.class.getConstructor(classes);
xpath = (XPath) constructor.newInstance(objects);
} catch (Exception ex) {
LOG.debug(ex.getMessage(), ex);
}
if (xpath == null) {
xpath = new XPath(str, null, prefixResolver, XPath.SELECT, null);
}
return xpath;
}
private static synchronized void fixupFunctionTable() {
installed = false;
if (new FunctionTable().functionAvailable("here")) {
LOG.debug("Here function already registered");
installed = true;
return;
}
LOG.debug("Registering Here function");
/**
* Try to register our here() implementation as internal function.
*/
try {
Class[] args = {String.class, Expression.class};
Method installFunction = FunctionTable.class.getMethod("installFunction", args);
if ((installFunction.getModifiers() & Modifier.STATIC) != 0) {
Object[] params = {"here", new FuncHere()};
installFunction.invoke(null, params);
installed = true;
}
} catch (Exception ex) {
LOG.debug("Error installing function using the static installFunction method", ex);
}
if (!installed) {
try {
funcTable = new FunctionTable();
Class[] args = {String.class, Class.class};
Method installFunction = FunctionTable.class.getMethod("installFunction", args);
Object[] params = {"here", FuncHere.class};
installFunction.invoke(funcTable, params);
installed = true;
} catch (Exception ex) {
LOG.debug("Error installing function using the static installFunction method", ex);
}
}
if (installed) {
LOG.debug("Registered class {} for XPath function 'here()' function in internal table", FuncHere.class.getName());
} else {
LOG.debug("Unable to register class {} for XPath function 'here()' function in internal table", FuncHere.class.getName());
}
}
}