/*
 * Copyright (c) 2018, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

package sun.security.ssl;

import javax.crypto.KeyAgreement;
import javax.crypto.SecretKey;
import javax.crypto.spec.SecretKeySpec;
import javax.net.ssl.SSLHandshakeException;
import java.io.IOException;
import java.security.GeneralSecurityException;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.spec.AlgorithmParameterSpec;

public class KAKeyDerivation implements SSLKeyDerivation {

    private final String algorithmName;
    private final HandshakeContext context;
    private final PrivateKey localPrivateKey;
    private final PublicKey peerPublicKey;

    KAKeyDerivation(String algorithmName,
                    HandshakeContext context,
                    PrivateKey localPrivateKey,
                    PublicKey peerPublicKey) {
        this.algorithmName = algorithmName;
        this.context = context;
        this.localPrivateKey = localPrivateKey;
        this.peerPublicKey = peerPublicKey;
    }

    @Override
    public
    SecretKey deriveKey(String algorithm,
                        AlgorithmParameterSpec params) throws IOException {
        if (!context.negotiatedProtocol.useTLS13PlusSpec()) {
            return t12DeriveKey(algorithm, params);
        } else {
            return t13DeriveKey(algorithm, params);
        }
    }

    private
    SecretKey t12DeriveKey(String algorithm,
                           AlgorithmParameterSpec params) throws IOException {
        try {
            KeyAgreement ka = JsseJce.getKeyAgreement(algorithmName);
            ka.init(localPrivateKey);
            ka.doPhase(peerPublicKey, true);
            SecretKey preMasterSecret =
            ka.generateSecret("TlsPremasterSecret");
            SSLMasterKeyDerivation mskd =
            SSLMasterKeyDerivation.valueOf(
            context.negotiatedProtocol);
            if (mskd == null) {
                // unlikely
                throw new SSLHandshakeException(
                "No expected master key derivation for protocol: " +
                context.negotiatedProtocol.name);
            }
            SSLKeyDerivation kd = mskd.createKeyDerivation(
            context, preMasterSecret);
            return kd.deriveKey("MasterSecret", params);
        } catch (GeneralSecurityException gse) {
            throw (SSLHandshakeException) new SSLHandshakeException(
            "Could not generate secret").initCause(gse);
        }
    }

    private
    SecretKey t13DeriveKey(String algorithm,
                           AlgorithmParameterSpec params) throws IOException {
        try {
            KeyAgreement ka = JsseJce.getKeyAgreement(algorithmName);
            ka.init(localPrivateKey);
            ka.doPhase(peerPublicKey, true);
            SecretKey sharedSecret =
            ka.generateSecret("TlsPremasterSecret");

            CipherSuite.HashAlg hashAlg = context.negotiatedCipherSuite.hashAlg;
            SSLKeyDerivation kd = context.handshakeKeyDerivation;
            HKDF hkdf = new HKDF(hashAlg.name);
            if (kd == null) {   // No PSK is in use.
                // If PSK is not in use Early Secret will still be
                // HKDF-Extract(0, 0).
                byte[] zeros = new byte[hashAlg.hashLength];
                SecretKeySpec ikm =
                new SecretKeySpec(zeros, "TlsPreSharedSecret");
                SecretKey earlySecret =
                hkdf.extract(zeros, ikm, "TlsEarlySecret");
                kd = new SSLSecretDerivation(context, earlySecret);
            }

            // derive salt secret
            SecretKey saltSecret = kd.deriveKey("TlsSaltSecret", null);

            // derive handshake secret
            return hkdf.extract(saltSecret, sharedSecret, algorithm);
        } catch (GeneralSecurityException gse) {
            throw (SSLHandshakeException) new SSLHandshakeException(
            "Could not generate secret").initCause(gse);
        }
    }
}