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Apache XML Security for Java supports XML-Signature Syntax and Processing,
W3C Recommendation 12 February 2002, and XML Encryption Syntax and
Processing, W3C Recommendation 10 December 2002. As of version 1.4,
the library supports the standard Java API JSR-105: XML Digital Signature APIs.
/**
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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.keys.keyresolver.implementations;
import java.security.Key;
import java.security.PublicKey;
import java.security.cert.X509Certificate;
import java.util.ArrayList;
import java.util.List;
import javax.crypto.SecretKey;
import org.apache.xml.security.encryption.EncryptedKey;
import org.apache.xml.security.encryption.XMLCipher;
import org.apache.xml.security.encryption.XMLEncryptionException;
import org.apache.xml.security.keys.keyresolver.KeyResolverSpi;
import org.apache.xml.security.keys.storage.StorageResolver;
import org.apache.xml.security.utils.EncryptionConstants;
import org.apache.xml.security.utils.XMLUtils;
import org.w3c.dom.Element;
/**
* The EncryptedKeyResolver
is not a generic resolver. It can
* only be for specific instantiations, as the key being unwrapped will
* always be of a particular type and will always have been wrapped by
* another key which needs to be recursively resolved.
*
* The EncryptedKeyResolver
can therefore only be instantiated
* with an algorithm. It can also be instantiated with a key (the KEK) or
* will search the static KeyResolvers to find the appropriate key.
*
* @author Berin Lautenbach
*/
public class EncryptedKeyResolver extends KeyResolverSpi {
/** {@link org.apache.commons.logging} logging facility */
private static org.apache.commons.logging.Log log =
org.apache.commons.logging.LogFactory.getLog(RSAKeyValueResolver.class);
private Key kek;
private String algorithm;
private List internalKeyResolvers;
/**
* Constructor for use when a KEK needs to be derived from a KeyInfo
* list
* @param algorithm
*/
public EncryptedKeyResolver(String algorithm) {
kek = null;
this.algorithm = algorithm;
}
/**
* Constructor used for when a KEK has been set
* @param algorithm
* @param kek
*/
public EncryptedKeyResolver(String algorithm, Key kek) {
this.algorithm = algorithm;
this.kek = kek;
}
/**
* This method is used to add a custom {@link KeyResolverSpi} to help
* resolve the KEK.
*
* @param realKeyResolver
*/
public void registerInternalKeyResolver(KeyResolverSpi realKeyResolver) {
if (internalKeyResolvers == null) {
internalKeyResolvers = new ArrayList();
}
internalKeyResolvers.add(realKeyResolver);
}
/** @inheritDoc */
public PublicKey engineLookupAndResolvePublicKey(
Element element, String BaseURI, StorageResolver storage
) {
return null;
}
/** @inheritDoc */
public X509Certificate engineLookupResolveX509Certificate(
Element element, String BaseURI, StorageResolver storage
) {
return null;
}
/** @inheritDoc */
public javax.crypto.SecretKey engineLookupAndResolveSecretKey(
Element element, String BaseURI, StorageResolver storage
) {
if (log.isDebugEnabled()) {
log.debug("EncryptedKeyResolver - Can I resolve " + element.getTagName());
}
if (element == null) {
return null;
}
SecretKey key = null;
boolean isEncryptedKey =
XMLUtils.elementIsInEncryptionSpace(element, EncryptionConstants._TAG_ENCRYPTEDKEY);
if (isEncryptedKey) {
if (log.isDebugEnabled()) {
log.debug("Passed an Encrypted Key");
}
try {
XMLCipher cipher = XMLCipher.getInstance();
cipher.init(XMLCipher.UNWRAP_MODE, kek);
if (internalKeyResolvers != null) {
int size = internalKeyResolvers.size();
for (int i = 0; i < size; i++) {
cipher.registerInternalKeyResolver(internalKeyResolvers.get(i));
}
}
EncryptedKey ek = cipher.loadEncryptedKey(element);
key = (SecretKey) cipher.decryptKey(ek, algorithm);
} catch (XMLEncryptionException e) {
if (log.isDebugEnabled()) {
log.debug(e);
}
}
}
return key;
}
}