X509KeySelector.java

package es.uji.security.crypto.xmldsign;

import java.security.Key;
import java.security.PublicKey;
import java.util.Iterator;

import java.security.cert.X509Certificate;
import javax.xml.crypto.*;
import javax.xml.crypto.dsig.SignatureMethod;
import javax.xml.crypto.dsig.keyinfo.KeyInfo;
import javax.xml.crypto.dsig.keyinfo.X509Data;

public class X509KeySelector extends KeySelector
{
    @SuppressWarnings("unchecked")
    public KeySelectorResult select(KeyInfo keyInfo, KeySelector.Purpose purpose,
            AlgorithmMethod method, XMLCryptoContext context) throws KeySelectorException
    {
        Iterator ki = keyInfo.getContent().iterator();

        while (ki.hasNext())
        {
            XMLStructure info = (XMLStructure) ki.next();
            if (!(info instanceof X509Data))
                continue;
            X509Data x509Data = (X509Data) info;
            Iterator xi = x509Data.getContent().iterator();
            while (xi.hasNext())
            {
                Object o = xi.next();
                if (!(o instanceof X509Certificate))
                    continue;
                final PublicKey key = ((X509Certificate) o).getPublicKey();
                // Make sure the algorithm is compatible
                // with the method.
                if (algEquals(method.getAlgorithm(), key.getAlgorithm()))
                {
                    return new KeySelectorResult()
                    {
                        public Key getKey()
                        {
                            return key;
                        }
                    };
                }
            }
        }
        throw new KeySelectorException("No key found!");
    }

    static boolean algEquals(String algURI, String algName)
    {
        if ((algName.equalsIgnoreCase("DSA") && algURI.equalsIgnoreCase(SignatureMethod.DSA_SHA1))
                || (algName.equalsIgnoreCase("RSA") && algURI
                        .equalsIgnoreCase(SignatureMethod.RSA_SHA1)))
        {
            return true;
        }
        else
        {
            return false;
        }
    }
}