/*
* Copyright 2016 Red Hat, Inc. and/or its affiliates
* and other contributors as indicated by the @author tags.
*
* Licensed 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.keycloak.jose.jwk;
import org.keycloak.common.util.Base64Url;
import org.keycloak.common.util.KeyUtils;
import java.math.BigInteger;
import java.security.Key;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.security.PublicKey;
import java.security.interfaces.RSAPublicKey;
/**
* @author <a href="mailto:sthorger@redhat.com">Stian Thorgersen</a>
*/
public class JWKBuilder {
public static final String DEFAULT_PUBLIC_KEY_USE = "sig";
public static final String DEFAULT_MESSAGE_DIGEST = "SHA-256";
private String kid;
private JWKBuilder() {
}
public static JWKBuilder create() {
return new JWKBuilder();
}
public JWKBuilder kid(String kid) {
this.kid = kid;
return this;
}
public JWK rs256(PublicKey key) {
RSAPublicKey rsaKey = (RSAPublicKey) key;
RSAPublicJWK k = new RSAPublicJWK();
String kid = this.kid != null ? this.kid : KeyUtils.createKeyId(key);
k.setKeyId(kid);
k.setKeyType(RSAPublicJWK.RSA);
k.setAlgorithm(RSAPublicJWK.RS256);
k.setPublicKeyUse(DEFAULT_PUBLIC_KEY_USE);
k.setModulus(Base64Url.encode(toIntegerBytes(rsaKey.getModulus())));
k.setPublicExponent(Base64Url.encode(toIntegerBytes(rsaKey.getPublicExponent())));
return k;
}
/**
* Copied from org.apache.commons.codec.binary.Base64
*/
private static byte[] toIntegerBytes(final BigInteger bigInt) {
int bitlen = bigInt.bitLength();
// round bitlen
bitlen = ((bitlen + 7) >> 3) << 3;
final byte[] bigBytes = bigInt.toByteArray();
if (((bigInt.bitLength() % 8) != 0) && (((bigInt.bitLength() / 8) + 1) == (bitlen / 8))) {
return bigBytes;
}
// set up params for copying everything but sign bit
int startSrc = 0;
int len = bigBytes.length;
// if bigInt is exactly byte-aligned, just skip signbit in copy
if ((bigInt.bitLength() % 8) == 0) {
startSrc = 1;
len--;
}
final int startDst = bitlen / 8 - len; // to pad w/ nulls as per spec
final byte[] resizedBytes = new byte[bitlen / 8];
System.arraycopy(bigBytes, startSrc, resizedBytes, startDst, len);
return resizedBytes;
}
}