Problem with signing XML document in two steps - Prepare XML docu ment with SignedInfo, then sign document

["Charlesworth, Chico" <Ch...@softwareag.co.uk>]

Hi,

 

I've got a business requirement whereby I cannot sign a XML document in one
go. First I must "prepare" the XML document where the SignedInfo part of the
XML signature needs to be added to the document, which I can do no problem.
Then using the returned "prepared" document, I later need to sign it, but
this step fails with a nullpointer?? Is this a bug?

 

I can add the SignedInfo XML part to my XML document using the following
code:

 

public org.w3c.dom.Document prepare(org.w3c.dom.Document doc) throws
Exception {

      XMLSignature sig = new XMLSignature(doc, "",
XMLSignature.ALGO_ID_SIGNATURE_DSA);

 

      if ((doc.getParentNode() == null) && (doc.getChildNodes().getLength()
> 0)) {

          // Append signature to root element

          Element rootElmnt = (Element) doc.getChildNodes().item(0);

          rootElmnt.appendChild(sig.getElement());

        } else {

          // Append signature to document

          doc.appendChild(sig.getElement());

        }

 

 

      // Specify the transforms

      Transforms transforms = new Transforms(doc);

      transforms.addTransform(Transforms.TRANSFORM_ENVELOPED_SIGNATURE);

      transforms.addTransform(Transforms.TRANSFORM_C14N_WITH_COMMENTS);

      sig.addDocument("", transforms,
org.apache.xml.security.utils.Constants.ALGO_ID_DIGEST_SHA1);

 

      // Generate Disgest Values

      sig.getSignedInfo().generateDigestValues();      

 

     // Normally would now addKeyInfo(certificate) and
addKeyInfo(certificatePublicKey) and sign(privateKey), 

     // But want to do this in a separate step!!

 

      return doc;

  }

 

Then I try to sign the returned document from the method above with the
following code but this throws a nullpointer???

 

public org.w3c.dom.Document sign(org.w3c.dom.Document doc) throws Exception
{

 

      // Get Signature Node

      Node signatureNode =
XPathAPI.selectSingleNode(doc.getDocumentElement(),
Constants.XMLSignature.SIGNATURE_XPATH);

      XMLSignature sig = new XMLSignature((Element) signatureNode, ""); //
Throws Nullpointer exception at this point

 

      // Add certificate to signature

      sig.addKeyInfo(cert);

      sig.addKeyInfo(cert.getPublicKey());

 

      // Sign Document

      sig.sign(privateKey);

 

      return doc;

  }

 

Any ideas?

Chico.

 

ps. this is what the packages/classes I'm importing:

 

import java.io.*;

 

import java.security.*;

import java.security.cert.*;

 

import javax.xml.transform.TransformerException;

import javax.xml.parsers.*;

 

import org.apache.xpath.XPathAPI;

import org.w3c.dom.*;

import org.xml.sax.*;

 

import org.apache.xml.security.algorithms.MessageDigestAlgorithm;

import org.apache.xml.security.c14n.*;

// import org.apache.xml.security.exceptions.XMLSecurityException;

import org.apache.xml.security.signature.*;

import org.apache.xml.security.keys.*;

import org.apache.xml.security.keys.content.*;

import org.apache.xml.security.keys.content.x509.*;

import org.apache.xml.security.keys.keyresolver.*;

import org.apache.xml.security.keys.storage.*;

import org.apache.xml.security.keys.storage.implementations.*;

import org.apache.xml.security.utils.XMLUtils;

import org.apache.xml.security.transforms.*;

import org.apache.xml.security.Init;

import org.apache.xml.serialize.*;


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