/*

 * Copyright (c) 2019, 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

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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;

/**

 * A common class for creating various KeyDerivation types.

 */

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);

        }

    }

    /**

     * Handle the TLSv1-1.2 objects, which don't use the HKDF algorithms.

     */

    private SecretKey t12DeriveKey(String algorithm,

            AlgorithmParameterSpec params) throws IOException {

        try {

            KeyAgreement ka = KeyAgreement.getInstance(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);

        }

    }

    /**

     * Handle the TLSv1.3 objects, which use the HKDF algorithms.

     */

    private SecretKey t13DeriveKey(String algorithm,

            AlgorithmParameterSpec params) throws IOException {

        try {

            KeyAgreement ka = KeyAgreement.getInstance(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);

        }

    }

}