src/org/apache/xml/security/c14n/helper/C14nHelper.java

/*
 * Copyright  1999-2004 The Apache Software Foundation.
 *
 *  Licensed 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.c14n.helper;



import org.apache.xml.security.c14n.CanonicalizationException;
import org.w3c.dom.Attr;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.NamedNodeMap;


/**
 * Temporary swapped static functions from the normalizer Section
 *
 * @author Christian Geuer-Pollmann
 */
public class C14nHelper {

   /**
    * Constructor C14nHelper
    *
    */
   private C14nHelper() {

      // don't allow instantiation
   }

   /**
    * Method namespaceIsRelative
    *
    * @param namespace
    * @return true if the given namespace is relative. 
    */
   public static boolean namespaceIsRelative(Attr namespace) {
      return !namespaceIsAbsolute(namespace);
   }

   /**
    * Method namespaceIsRelative
    *
    * @param namespaceValue
    * @return true if the given namespace is relative.
    */
   public static boolean namespaceIsRelative(String namespaceValue) {
      return !namespaceIsAbsolute(namespaceValue);
   }

   /**
    * Method namespaceIsAbsolute
    *
    * @param namespace
    * @return true if the given namespace is absolute.
    */
   public static boolean namespaceIsAbsolute(Attr namespace) {
      return namespaceIsAbsolute(namespace.getValue());
   }

   /**
    * Method namespaceIsAbsolute
    *
    * @param namespaceValue
    * @return true if the given namespace is absolute.
    */
   public static boolean namespaceIsAbsolute(String namespaceValue) {

      // assume empty namespaces are absolute
      if (namespaceValue.length() == 0) {
         return true;
      }
      return namespaceValue.indexOf(':')>0;
   }

   /**
    * This method throws an exception if the Attribute value contains
    * a relative URI.
    *
    * @param attr
    * @throws CanonicalizationException
    */
   public static void assertNotRelativeNS(Attr attr)
           throws CanonicalizationException {

      if (attr == null) {
         return;
      }

      String nodeAttrName = attr.getNodeName();
      boolean definesDefaultNS = nodeAttrName.equals("xmlns");
      boolean definesNonDefaultNS = nodeAttrName.startsWith("xmlns:");

      if (definesDefaultNS || definesNonDefaultNS) {
         if (namespaceIsRelative(attr)) {
            String parentName = attr.getOwnerElement().getTagName();
            String attrValue = attr.getValue();
            Object exArgs[] = { parentName, nodeAttrName, attrValue };

            throw new CanonicalizationException(
               "c14n.Canonicalizer.RelativeNamespace", exArgs);
         }
      }
   }

   /**
    * This method throws a CanonicalizationException if the supplied Document
    * is not able to be traversed using a TreeWalker.
    *
    * @param document
    * @throws CanonicalizationException
    */
   public static void checkTraversability(Document document)
           throws CanonicalizationException {

      if (!document.isSupported("Traversal", "2.0")) {
         Object exArgs[] = {
            document.getImplementation().getClass().getName() };

         throw new CanonicalizationException(
            "c14n.Canonicalizer.TraversalNotSupported", exArgs);
      }
   }

   /**
    * This method throws a CanonicalizationException if the supplied Element
    * contains any relative namespaces.
    *
    * @param ctxNode
    * @throws CanonicalizationException
    * @see C14nHelper#assertNotRelativeNS(Attr)
    */
   public static void checkForRelativeNamespace(Element ctxNode)
           throws CanonicalizationException {

      if (ctxNode != null) {
         NamedNodeMap attributes = ctxNode.getAttributes();

         for (int i = 0; i < attributes.getLength(); i++) {
            C14nHelper.assertNotRelativeNS((Attr) attributes.item(i));
         }
      } else {
         throw new CanonicalizationException(
            "Called checkForRelativeNamespace() on null");
      }
   }
}