XML DSig - NullPointerException while unmarshalling

[Marcin 'golish' Goliszewski]

Hello.

I'm writing an application which creates and verifies XML DSig
signatures. I'm using the Java API described in JSR105 and implemented
in JDK6. I have encountered a weird problem, which I wasn't able to
solve myself. I have the following fragment of source code in my
application:

#v+
public static boolean verifySignature(Element signatureElement) {

DOMValidateContext validateContext = new DOMValidateContext(
new KeyValueKeySelector(), signatureElement);

XMLSignatureFactory signatureFactory = XMLSignatureFactory
.getInstance("DOM");

XMLSignature signature = null;

try {
signature = signatureFactory.unmarshalXMLSignature(validateContext);
} catch (MarshalException e) {
// TODO: add content
}

boolean coreValidity = true;

try {
coreValidity = signature.validate(validateContext);
} catch (XMLSignatureException e) {
// TODO: add content
}

return coreValidity;

}
#v-

Unfortunately, this code reaches the line with the
unmarshalXMLSignature() invocation - a NullPointerException is thrown
inside this method. Here's the stack trace:

#v+
Exception in thread "main" java.lang.NullPointerException
at org.jcp.xml.dsig.internal.dom.DOMReference.<init>(DOMReference.java:156)
at org.jcp.xml.dsig.internal.dom.DOMSignedInfo.<init>(DOMSignedInfo.java:128)
at org.jcp.xml.dsig.internal.dom.DOMXMLSignature.<init>(DOMXMLSignature.java:118)
at org.jcp.xml.dsig.internal.dom.DOMXMLSignatureFactory.unmarshal(DOMXMLSignatureFactory.java:152)
at org.jcp.xml.dsig.internal.dom.DOMXMLSignatureFactory.unmarshalXMLSignature(DOMXMLSignatureFactory.java:116)
at net.xmxp.lib.SignatureVerifier.verifySignature(SignatureVerifier.java:100)
at net.xmxp.receiver.TestReceiver.gotEnvelope(TestReceiver.java:61)
at net.xmxp.receiver.ReceiverConnectionHandler.endElement(ReceiverConnectionHandler.java:513)
at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.endElement(AbstractSAXParser.java:601)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanEndElement(XMLDocumentFragmentScannerImpl.java:1772)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl$FragmentContentDriver.next(XMLDocumentFragmentScannerImpl.java:2923)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl.next(XMLDocumentScannerImpl.java:645)
at com.sun.org.apache.xerces.internal.impl.XMLNSDocumentScannerImpl.next(XMLNSDocumentScannerImpl.java:140)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanDocument(XMLDocumentFragmentScannerImpl.java:508)
at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:807)
at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:737)
at com.sun.org.apache.xerces.internal.parsers.XMLParser.parse(XMLParser.java:107)
at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.parse(AbstractSAXParser.java:1205)
at net.xmxp.receiver.ReceiverConnectionHandler.serve(ReceiverConnectionHandler.java:978)
at net.xmxp.receiver.TestReceiver.main(TestReceiver.java:55)
#v-

According to the javadocs, NullPointerException may be thrown if
validateContext would be null. But it's not. So I did some debugging.
The interesting fragment from the DOMReference class is:

#v+
151 public DOMReference(Element refElem, XMLCryptoContext context)
152 throws MarshalException {
153 // unmarshal Transforms, if specified
154 Element nextSibling = DOMUtils.getFirstChildElement(refElem);
156 List transforms = new ArrayList(5);
157 if (nextSibling.getLocalName().equals("Transforms")) {
158 Element transformElem = DOMUtils.getFirstChildElement(nextSibling);
159 while (transformElem != null) {
160 transforms.add(new DOMTransform(transformElem, context));
161 transformElem = DOMUtils.getNextSiblingElement(transformElem);
162 }
163 nextSibling = DOMUtils.getNextSiblingElement(nextSibling);
164 }
#v-

I've spotted that the NullPointerException is thrown because the
expression nextSibling.getLocalName() in line 156 is null. The weird
thing (at least for me) is the cause for which it's null: according to
the Eclipse debugger the method called is NodeImpl.getLocalName() (which
returns null) instead of ElementImpl.getLocalName(), which AFAIK should
be called. Did anyone encounter this (or a similar) problem? Or maybe
someone has an idea how to solve/avoid this problem?

This problem is repeatable in various environments:
* 64-bit Linux + 64-bit JDK,
* 64-bit Linux + 32-bit JDK,
* 32-bit Linux,
* 32-bit Windows.
All tests were performed using JDK6 because AFAIK previous versions
didn't include a JSR105 implementation.

Thanks in advance for all the help and tips.


Regards,