XML Digital Signature API Overview and Tutorial

Example 11-5 Validate.java

import javax.xml.crypto.*;
import javax.xml.crypto.dsig.*;
import javax.xml.crypto.dom.*;
import javax.xml.crypto.dsig.dom.DOMValidateContext;
import javax.xml.crypto.dsig.keyinfo.*;
import java.io.FileInputStream;
import java.security.*;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
import javax.xml.parsers.DocumentBuilderFactory;
import org.w3c.dom.Document;
import org.w3c.dom.NodeList;

/**
 * This is a simple example of validating an XML
 * Signature using the JSR 105 API. It assumes the key needed to
 * validate the signature is contained in a KeyValue KeyInfo.
 */
public class Validate {

    //
    // Synopsis: java Validate [document]
    //
    //    where "document" is the name of a file containing the XML document
    //    to be validated.
    //
    public static void main(String[] args) throws Exception {

        // Instantiate the document to be validated
        DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
        dbf.setNamespaceAware(true);
        Document doc =
            dbf.newDocumentBuilder().parse(new FileInputStream(args[0]));

        // Find Signature element
        NodeList nl =
            doc.getElementsByTagNameNS(XMLSignature.XMLNS, "Signature");
        if (nl.getLength() == 0) {
            throw new Exception("Cannot find Signature element");
        }

        // Create a DOM XMLSignatureFactory that will be used to unmarshal the
        // document containing the XMLSignature
        XMLSignatureFactory fac = XMLSignatureFactory.getInstance("DOM");

        // Create a DOMValidateContext and specify a KeyValue KeySelector
        // and document context
        DOMValidateContext valContext = new DOMValidateContext
            (new KeyValueKeySelector(), nl.item(0));

        // unmarshal the XMLSignature
        XMLSignature signature = fac.unmarshalXMLSignature(valContext);

        // Validate the XMLSignature (generated above)
        boolean coreValidity = signature.validate(valContext);

        // Check core validation status
        if (coreValidity == false) {
            System.err.println("Signature failed core validation");
            boolean sv = signature.getSignatureValue().validate(valContext);
            System.out.println("signature validation status: " + sv);
            // check the validation status of each Reference
            Iterator i = signature.getSignedInfo().getReferences().iterator();
            for (int j=0; i.hasNext(); j++) {
                boolean refValid =
                    ((Reference) i.next()).validate(valContext);
                System.out.println("ref["+j+"] validity status: " + refValid);
            }
        } else {
            System.out.println("Signature passed core validation");
        }
    }

    /**
     * KeySelector which retrieves the public key out of the
     * KeyValue element and returns it.
     * NOTE: If the key algorithm doesn't match signature algorithm,
     * then the public key will be ignored.
     */
    private static class KeyValueKeySelector extends KeySelector {
        public KeySelectorResult select(KeyInfo keyInfo,
                                        KeySelector.Purpose purpose,
                                        AlgorithmMethod method,
                                        XMLCryptoContext context)
            throws KeySelectorException {
            if (keyInfo == null) {
                throw new KeySelectorException("Null KeyInfo object!");
            }
            SignatureMethod sm = (SignatureMethod) method;
            List list = keyInfo.getContent();

            for (int i = 0; i < list.size(); i++) {
                XMLStructure xmlStructure = (XMLStructure) list.get(i);
                if (xmlStructure instanceof KeyValue) {
                    PublicKey pk = null;
                    try {
                        pk = ((KeyValue)xmlStructure).getPublicKey();
                    } catch (KeyException ke) {
                        throw new KeySelectorException(ke);
                    }
                    // make sure algorithm is compatible with method
                    if (algEquals(sm.getAlgorithm(), pk.getAlgorithm())) {
                        return new SimpleKeySelectorResult(pk);
                    }
                }
            }
            throw new KeySelectorException("No KeyValue element found!");
        }

        //@@@FIXME: this should also work for key types other than DSA/RSA
        static boolean algEquals(String algURI, String algName) {
            if (algName.equalsIgnoreCase("DSA") &&
                algURI.equalsIgnoreCase("http://www.w3.org/2009/xmldsig11#dsa-sha256")) {
                return true;
            } else if (algName.equalsIgnoreCase("RSA") &&
                       algURI.equalsIgnoreCase("http://www.w3.org/2001/04/xmldsig-more#rsa-sha256")) {
                return true;
            } else {
                return false;
            }
        }
    }

    private static class SimpleKeySelectorResult implements KeySelectorResult {
        private PublicKey pk;
        SimpleKeySelectorResult(PublicKey pk) {
            this.pk = pk;
        }

        public Key getKey() { return pk; }
    }
}

Example 11-6 envelope.xml

<Envelope xmlns="urn:envelope">
</Envelope>

Example 11-7 signature.xml

Example 11-8 GenEnveloped.java

import javax.xml.crypto.*;
import javax.xml.crypto.dsig.*;
import javax.xml.crypto.dom.*;
import javax.xml.crypto.dsig.dom.DOMSignContext;
import javax.xml.crypto.dsig.keyinfo.*;
import javax.xml.crypto.dsig.spec.*;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.OutputStream;
import java.security.*;
import java.util.Collections;
import java.util.Iterator;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.transform.*;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;
import org.w3c.dom.Document;

/**
 * This is a simple example of generating an Enveloped XML
 * Signature using the JSR 105 API. The resulting signature will look
 * like (key and signature values will be different):
 *
 * <pre><code>
 *<Envelope xmlns="urn:envelope">
 * <Signature xmlns="http://www.w3.org/2000/09/xmldsig#">
 *   <SignedInfo>
 *     <CanonicalizationMethod Algorithm="http://www.w3.org/TR/2001/REC-xml-c14n-20010315"/>
 *     <SignatureMethod Algorithm="http://www.w3.org/2000/09/xmldsig#dsa-sha256"/>
 *     <Reference URI="">
 *       <Transforms>
 *         <Transform Algorithm="http://www.w3.org/2000/09/xmldsig#enveloped-signature"/>
 *       </Transforms>
 *       <DigestMethod Algorithm="http://www.w3.org/2001/04/xmlenc#sha256"/>
 *       <DigestValue>K8M/lPbKnuMDsO0Uzuj75lQtzQI=<DigestValue>
 *     </Reference>
 *   </SignedInfo>
 *   <SignatureValue>
 *     DpEylhQoiUKBoKWmYfajXO7LZxiDYgVtUtCNyTgwZgoChzorA2nhkQ==
 *   </SignatureValue>
 *   <KeyInfo>
 *     <KeyValue>
 *       <DSAKeyValue>
 *         <P>
 *           rFto8uPQM6y34FLPmDh40BLJ1rVrC8VeRquuhPZ6jYNFkQuwxnu/wCvIAMhukPBL
 *           FET8bJf/b2ef+oqxZajEb+88zlZoyG8g/wMfDBHTxz+CnowLahnCCTYBp5kt7G8q
 *           UobJuvjylwj1st7V9Lsu03iXMXtbiriUjFa5gURasN8=
 *         </P>
 *         <Q>
 *           kEjAFpCe4lcUOdwphpzf+tBaUds=
 *         </Q>
 *         <G>
 *           oe14R2OtyKx+s+60O5BRNMOYpIg2TU/f15N3bsDErKOWtKXeNK9FS7dWStreDxo2
 *           SSgOonqAd4FuJ/4uva7GgNL4ULIqY7E+mW5iwJ7n/WTELh98mEocsLXkNh24HcH4
 *           BZfSCTruuzmCyjdV1KSqX/Eux04HfCWYmdxN3SQ/qqw=
 *         </G>
 *         <Y>
 *           pA5NnZvcd574WRXuOA7ZfC/7Lqt4cB0MRLWtHubtJoVOao9ib5ry4rTk0r6ddnOv
 *           AIGKktutzK3ymvKleS3DOrwZQgJ+/BDWDW8kO9R66o6rdjiSobBi/0c2V1+dkqOg
 *           jFmKz395mvCOZGhC7fqAVhHat2EjGPMfgSZyABa7+1k=
 *         </Y>
 *       </DSAKeyValue>
 *     </KeyValue>
 *   </KeyInfo>
 * </Signature>
 *</Envelope>
 * </code></pre>
 */
public class GenEnveloped {

    //
    // Synopsis: java GenEnveloped [document] [output]
    //
    //    where "document" is the name of a file containing the XML document
    //    to be signed, and "output" is the name of the file to store the
    //    signed document. The 2nd argument is optional - if not specified,
    //    standard output will be used.
    //
    public static void main(String[] args) throws Exception {

        // Create a DOM XMLSignatureFactory that will be used to generate the
        // enveloped signature
        XMLSignatureFactory fac = XMLSignatureFactory.getInstance("DOM");

        // Create a Reference to the enveloped document (in this case we are
        // signing the whole document, so a URI of "" signifies that) and
        // also specify the SHA256 digest algorithm and the ENVELOPED Transform.
        Reference ref = fac.newReference
            ("", fac.newDigestMethod(DigestMethod.SHA256, null),
             Collections.singletonList
              (fac.newTransform
                (Transform.ENVELOPED, (TransformParameterSpec) null)),
             null, null);

        // Create the SignedInfo
        SignedInfo si = fac.newSignedInfo
            (fac.newCanonicalizationMethod
             (CanonicalizationMethod.INCLUSIVE_WITH_COMMENTS,
              (C14NMethodParameterSpec) null),
             fac.newSignatureMethod("http://www.w3.org/2000/09/xmldsig#dsa-sha256", null),
             Collections.singletonList(ref));

        // Create a DSA KeyPair
        KeyPairGenerator kpg = KeyPairGenerator.getInstance("DSA");
        kpg.initialize(2048);
        KeyPair kp = kpg.generateKeyPair();

        // Create a KeyValue containing the DSA PublicKey that was generated
        KeyInfoFactory kif = fac.getKeyInfoFactory();
        KeyValue kv = kif.newKeyValue(kp.getPublic());

        // Create a KeyInfo and add the KeyValue to it
        KeyInfo ki = kif.newKeyInfo(Collections.singletonList(kv));

        // Instantiate the document to be signed
        DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
        dbf.setNamespaceAware(true);
        Document doc =
            dbf.newDocumentBuilder().parse(new FileInputStream(args[0]));

        // Create a DOMSignContext and specify the DSA PrivateKey and
        // location of the resulting XMLSignature's parent element
        DOMSignContext dsc = new DOMSignContext
            (kp.getPrivate(), doc.getDocumentElement());

        // Create the XMLSignature (but don't sign it yet)
        XMLSignature signature = fac.newXMLSignature(si, ki);

        // Marshal, generate (and sign) the enveloped signature
        signature.sign(dsc);

        // output the resulting document
        OutputStream os;
        if (args.length > 1) {
           os = new FileOutputStream(args[1]);
        } else {
           os = System.out;
        }

        TransformerFactory tf = TransformerFactory.newInstance();
        Transformer trans = tf.newTransformer();
        trans.transform(new DOMSource(doc), new StreamResult(os));
    }
}

Example 11-9 envelope.xml

<Envelope xmlns="urn:envelope">
</Envelope>