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 * Copyright (c) 2006, 2016, 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 java.security.*;
import java.security.interfaces.ECPublicKey;
import java.security.spec.*;

import java.util.EnumSet;
import javax.crypto.SecretKey;
import javax.crypto.KeyAgreement;
import javax.net.ssl.SSLHandshakeException;

/**
 * Helper class for the ECDH key exchange. It generates the appropriate
 * ephemeral keys as necessary and performs the actual shared secret derivation.
 *
 * @since   1.6
 * @author  Andreas Sterbenz
 */
final class ECDHCrypt {

    // our private key
    private PrivateKey privateKey;

    // our public key
    private ECPublicKey publicKey;

    // Called by ServerHandshaker for static ECDH
    ECDHCrypt(PrivateKey privateKey, PublicKey publicKey) {
        this.privateKey = privateKey;
        this.publicKey = (ECPublicKey)publicKey;
    }

    // Called by ServerHandshaker for ephemeral ECDH
    ECDHCrypt(int curveId, SecureRandom random) {
        try {
            KeyPairGenerator kpg = JsseJce.getKeyPairGenerator("EC");
            ECGenParameterSpec params =
                    EllipticCurvesExtension.getECGenParamSpec(curveId);
            kpg.initialize(params, random);
            KeyPair kp = kpg.generateKeyPair();
            privateKey = kp.getPrivate();
            publicKey = (ECPublicKey)kp.getPublic();
        } catch (GeneralSecurityException e) {
            throw new RuntimeException("Could not generate DH keypair", e);
        }
    }

    // Called by ClientHandshaker with params it received from the server
    ECDHCrypt(ECParameterSpec params, SecureRandom random) {
        try {
            KeyPairGenerator kpg = JsseJce.getKeyPairGenerator("EC");
            kpg.initialize(params, random);
            KeyPair kp = kpg.generateKeyPair();
            privateKey = kp.getPrivate();
            publicKey = (ECPublicKey)kp.getPublic();
        } catch (GeneralSecurityException e) {
            throw new RuntimeException("Could not generate DH keypair", e);
        }
    }

    /**
     * Gets the public key of this end of the key exchange.
     */
    PublicKey getPublicKey() {
        return publicKey;
    }

    // called by ClientHandshaker with either the server's static or
    // ephemeral public key
    SecretKey getAgreedSecret(
            PublicKey peerPublicKey) throws SSLHandshakeException {

        try {
            KeyAgreement ka = JsseJce.getKeyAgreement("ECDH");
            ka.init(privateKey);
            ka.doPhase(peerPublicKey, true);
            return ka.generateSecret("TlsPremasterSecret");
        } catch (GeneralSecurityException e) {
            throw (SSLHandshakeException) new SSLHandshakeException(
                "Could not generate secret").initCause(e);
        }
    }

    // called by ServerHandshaker
    SecretKey getAgreedSecret(
            byte[] encodedPoint) throws SSLHandshakeException {

        try {
            ECParameterSpec params = publicKey.getParams();
            ECPoint point =
                    JsseJce.decodePoint(encodedPoint, params.getCurve());
            KeyFactory kf = JsseJce.getKeyFactory("EC");
            ECPublicKeySpec spec = new ECPublicKeySpec(point, params);
            PublicKey peerPublicKey = kf.generatePublic(spec);
            return getAgreedSecret(peerPublicKey);
        } catch (GeneralSecurityException | java.io.IOException e) {
            throw (SSLHandshakeException) new SSLHandshakeException(
                "Could not generate secret").initCause(e);
        }
    }

    // Check constraints of the specified EC public key.
    void checkConstraints(AlgorithmConstraints constraints,
            byte[] encodedPoint) throws SSLHandshakeException {

        try {

            ECParameterSpec params = publicKey.getParams();
            ECPoint point =
                    JsseJce.decodePoint(encodedPoint, params.getCurve());
            ECPublicKeySpec spec = new ECPublicKeySpec(point, params);

            KeyFactory kf = JsseJce.getKeyFactory("EC");
            ECPublicKey publicKey = (ECPublicKey)kf.generatePublic(spec);

            // check constraints of ECPublicKey
            if (!constraints.permits(
                    EnumSet.of(CryptoPrimitive.KEY_AGREEMENT), publicKey)) {
                throw new SSLHandshakeException(
                    "ECPublicKey does not comply to algorithm constraints");
            }
        } catch (GeneralSecurityException | java.io.IOException e) {
            throw (SSLHandshakeException) new SSLHandshakeException(
                    "Could not generate ECPublicKey").initCause(e);
        }
    }

}
