001/*
002 * The contents of this file are subject to the terms of the Common Development and
003 * Distribution License (the License). You may not use this file except in compliance with the
004 * License.
005 *
006 * You can obtain a copy of the License at legal/CDDLv1.0.txt. See the License for the
007 * specific language governing permission and limitations under the License.
008 *
009 * When distributing Covered Software, include this CDDL Header Notice in each file and include
010 * the License file at legal/CDDLv1.0.txt. If applicable, add the following below the CDDL
011 * Header, with the fields enclosed by brackets [] replaced by your own identifying
012 * information: "Portions copyright [year] [name of copyright owner]".
013 *
014 * Copyright 2013-2015 ForgeRock AS.
015 */
016
017package org.forgerock.json.jose.jws.handlers;
018
019import org.forgerock.json.jose.exceptions.JwsSigningException;
020import org.forgerock.json.jose.jws.JwsAlgorithm;
021import org.forgerock.json.jose.utils.Utils;
022import org.forgerock.util.Reject;
023
024import java.security.InvalidKeyException;
025import java.security.MessageDigest;
026import java.security.NoSuchAlgorithmException;
027import javax.crypto.Mac;
028import javax.crypto.SecretKey;
029import javax.crypto.spec.SecretKeySpec;
030
031/**
032 * An implementation of the SigningHandler which can sign and verify using algorithms from the HMAC family.
033 *
034 * @since 2.0.0
035 */
036public class HmacSigningHandler implements SigningHandler {
037
038    private final byte[] sharedSecret;
039
040    /**
041     * Constructs a new HmacSigningHandler.
042     *
043     * @param sharedSecret The shared secret to use to sign the data.
044     */
045    public HmacSigningHandler(byte[] sharedSecret) {
046        Reject.ifNull(sharedSecret, "Shared secret cannot be null.");
047        this.sharedSecret = sharedSecret.clone();
048    }
049
050    /**
051     * {@inheritDoc}
052     */
053    @Override
054    public byte[] sign(JwsAlgorithm algorithm, String data) {
055        return signWithHMAC(algorithm.getAlgorithm(), sharedSecret, data.getBytes(Utils.CHARSET));
056    }
057
058    /**
059     * {@inheritDoc}
060     */
061    @Override
062    public byte[] sign(final JwsAlgorithm algorithm, final byte[] data) {
063        return signWithHMAC(algorithm.getAlgorithm(), sharedSecret, data);
064    }
065
066    /**
067     * Performs the creation of the MAC for the data using the given Java Cryptographic algorithm.
068     *
069     * @param algorithm The Java Cryptographic algorithm.
070     * @param sharedSecret The shared secret to use to sign the data.
071     * @param data The data to sign.
072     * @return A byte array of the signature.
073     */
074    private byte[] signWithHMAC(String algorithm, byte[] sharedSecret, byte[] data) {
075        try {
076            Mac mac = Mac.getInstance(algorithm);
077            SecretKey secretKey = new SecretKeySpec(sharedSecret, algorithm.toUpperCase());
078            mac.init(secretKey);
079            return mac.doFinal(data);
080        } catch (NoSuchAlgorithmException e) {
081            throw new JwsSigningException("Unsupported Signing Algorithm, " + algorithm, e);
082        } catch (InvalidKeyException e) {
083            throw new JwsSigningException(e);
084        }
085    }
086
087    /**
088     * Verifies that the given signature is valid for the given data.
089     * <p>
090     * Uses the Java Cryptographic algorithm defined by the JwsAlgorithm and private key to create a new signature
091     * of the data to compare against the given signature to see if they are identical.
092     *
093     * This implementation avoids timing attacks by enforcing checking of each element of the
094     * array against one another. We do not rely on Arrays.equal or other methods which
095     * may return early upon discovering a mistake.
096     *
097     * @param algorithm The JwsAlgorithm defining the JavaCryptographic algorithm.
098     * @param data The data that was signed.
099     * @param signature The signature of the data.
100     * @return <code>true</code> if the signature is a valid signature of the data.
101     */
102    @Override
103    public boolean verify(JwsAlgorithm algorithm, byte[] data, byte[] signature) {
104        byte[] signed = signWithHMAC(algorithm.getAlgorithm(), sharedSecret, data);
105        return MessageDigest.isEqual(signed, signature);
106    }
107}