org.apache.xml.security.utils.resolver.implementations.ResolverFragment Maven / Gradle / Ivy

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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.
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/**
 * 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.resolver.implementations;

import org.apache.xml.security.signature.XMLSignatureInput;
import org.apache.xml.security.utils.XMLUtils;
import org.apache.xml.security.utils.resolver.ResourceResolverContext;
import org.apache.xml.security.utils.resolver.ResourceResolverException;
import org.apache.xml.security.utils.resolver.ResourceResolverSpi;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;

/**
 * This resolver is used for resolving same-document URIs like URI="" of URI="#id".
 *
 * @author $Author: coheigea $
 * @see The Reference processing model in the XML Signature spec
 * @see Same-Document URI-References in the XML Signature spec
 * @see Section 4.2 of RFC 2396
 */
public class ResolverFragment extends ResourceResolverSpi {

    private static org.slf4j.Logger log =
        org.slf4j.LoggerFactory.getLogger(ResolverFragment.class);
    
    @Override
    public boolean engineIsThreadSafe() {
        return true;
    }
    
    /**
     * @inheritDoc
     */
    @Override
    public XMLSignatureInput engineResolveURI(ResourceResolverContext context) 
        throws ResourceResolverException {

        Document doc = context.attr.getOwnerElement().getOwnerDocument();

        Node selectedElem = null;
        if (context.uriToResolve.equals("")) {
            /*
             * Identifies the node-set (minus any comment nodes) of the XML
             * resource containing the signature
             */
            if (log.isDebugEnabled()) {
                log.debug("ResolverFragment with empty URI (means complete document)");
            }
            selectedElem = doc;
        } else {
            /*
             * URI="#chapter1"
             * Identifies a node-set containing the element with ID attribute
             * value 'chapter1' of the XML resource containing the signature.
             * XML Signature (and its applications) modify this node-set to
             * include the element plus all descendants including namespaces and
             * attributes -- but not comments.
             */
            String id = context.uriToResolve.substring(1);

            selectedElem = doc.getElementById(id);
            if (selectedElem == null) {
                Object exArgs[] = { id };
                throw new ResourceResolverException(
                    "signature.Verification.MissingID", exArgs, context.uriToResolve, context.baseUri
                );
            }
            if (context.secureValidation) {
                Element start = context.attr.getOwnerDocument().getDocumentElement();
                if (!XMLUtils.protectAgainstWrappingAttack(start, id)) {
                    Object exArgs[] = { id };
                    throw new ResourceResolverException(
                        "signature.Verification.MultipleIDs", exArgs, context.uriToResolve, context.baseUri
                    );
                }
            }
            if (log.isDebugEnabled()) {
                log.debug(
                    "Try to catch an Element with ID " + id + " and Element was " + selectedElem
                );
            }
        }

        XMLSignatureInput result = new XMLSignatureInput(selectedElem);
        result.setSecureValidation(context.secureValidation);
        result.setExcludeComments(true);

        result.setMIMEType("text/xml");
        if (context.baseUri != null && context.baseUri.length() > 0) {
            result.setSourceURI(context.baseUri.concat(context.uriToResolve));      
        } else {
            result.setSourceURI(context.uriToResolve);      
        }
        return result;
    }

    /**
     * Method engineCanResolve
     * @inheritDoc
     * @param context
     */
    public boolean engineCanResolveURI(ResourceResolverContext context) {
        if (context.uriToResolve == null) {
            if (log.isDebugEnabled()) {
                log.debug("Quick fail for null uri");
            }
            return false;
        }
        
        if (context.uriToResolve.equals("") || 
            context.uriToResolve.charAt(0) == '#' && !context.uriToResolve.startsWith("#xpointer(")
        ) {
            if (log.isDebugEnabled()) {
                log.debug("State I can resolve reference: \"" + context.uriToResolve + "\"");
            }
            return true;
        }
        if (log.isDebugEnabled()) {
            log.debug("Do not seem to be able to resolve reference: \"" + context.uriToResolve + "\"");
        }
        return false;
    }

}