/*

 * 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 java.io.IOException;

import java.math.BigInteger;

import java.security.*;

import java.security.interfaces.XECPublicKey;

import java.security.spec.*;

import sun.security.ssl.NamedGroup.NamedGroupSpec;

import sun.security.util.*;

/**

 * Specifics for XEC/XDH Keys/Exchanges

 */

final class XDHKeyExchange {

    static final SSLKeyAgreementGenerator xdheKAGenerator

            = new XDHEKAGenerator();

    static final class XDHECredentials implements NamedGroupCredentials {

        final XECPublicKey popPublicKey;

        final NamedGroup namedGroup;

        XDHECredentials(XECPublicKey popPublicKey, NamedGroup namedGroup) {

            this.popPublicKey = popPublicKey;

            this.namedGroup = namedGroup;

        }

        @Override

        public PublicKey getPublicKey() {

            return popPublicKey;

        }

        @Override

        public NamedGroup getNamedGroup() {

            return namedGroup;

        }

        /**

         * Parse the encoded Point into the XDHECredentials using the

         * namedGroup.

         */

        static XDHECredentials valueOf(NamedGroup namedGroup,

                byte[] encodedPoint) throws IOException,

                GeneralSecurityException {

            if (namedGroup.spec != NamedGroupSpec.NAMED_GROUP_XDH) {

                throw new RuntimeException(

                        "Credentials decoding:  Not XDH named group");

            }

            if (encodedPoint == null || encodedPoint.length == 0) {

                return null;

            }

            byte[] uBytes = encodedPoint.clone();

            Utilities.reverseBytes(uBytes);

            BigInteger u = new BigInteger(1, uBytes);

            XECPublicKeySpec xecPublicKeySpec = new XECPublicKeySpec(

                    new NamedParameterSpec(namedGroup.name), u);

            KeyFactory factory = KeyFactory.getInstance(namedGroup.algorithm);

            XECPublicKey publicKey = (XECPublicKey) factory.generatePublic(

                    xecPublicKeySpec);

            return new XDHECredentials(publicKey, namedGroup);

        }

    }

    static final class XDHEPossession implements NamedGroupPossession {

        final PrivateKey privateKey;

        final XECPublicKey publicKey;

        final NamedGroup namedGroup;

        XDHEPossession(NamedGroup namedGroup, SecureRandom random) {

            try {

                KeyPairGenerator kpg

                        = KeyPairGenerator.getInstance(namedGroup.algorithm);

                kpg.initialize(namedGroup.keAlgParamSpec, random);

                KeyPair kp = kpg.generateKeyPair();

                privateKey = kp.getPrivate();

                publicKey = (XECPublicKey) kp.getPublic();

            } catch (GeneralSecurityException e) {

                throw new RuntimeException(

                        "Could not generate XDH keypair", e);

            }

            this.namedGroup = namedGroup;

        }

        @Override

        public byte[] encode() {

            byte[] uBytes = ECUtil.trimZeroes(publicKey.getU().toByteArray());

            int expLength;

            switch (namedGroup) {

                case X25519:

                    expLength = 32;

                    break;

                case X448:

                    expLength = 56;

                    break;

                default:

                    throw new RuntimeException("Invalid XDH group");

            }

            if (uBytes.length > expLength) {

                throw new RuntimeException("Encoded XDH key too large");

            }

            if (uBytes.length != expLength) {

                byte[] tmp = new byte[expLength];

                System.arraycopy(uBytes, 0, tmp,

                        expLength - uBytes.length, uBytes.length);

                uBytes = tmp;

            }

            Utilities.reverseBytes(uBytes);

            return (uBytes);

        }

        @Override

        public PublicKey getPublicKey() {

            return publicKey;

        }

        @Override

        public NamedGroup getNamedGroup() {

            return namedGroup;

        }

        @Override

        public PrivateKey getPrivateKey() {

            return privateKey;

        }

    }

    private static final class XDHEKAGenerator

            implements SSLKeyAgreementGenerator {

        // Prevent instantiation of this class.

        private XDHEKAGenerator() {

            // blank

        }

        @Override

        public SSLKeyDerivation createKeyDerivation(

                HandshakeContext context) throws IOException {

            XDHEPossession xdhePossession = null;

            XDHECredentials xdheCredentials = null;

            for (SSLPossession poss : context.handshakePossessions) {

                if (!(poss instanceof XDHEPossession)) {

                    continue;

                }

                NamedGroup ng = ((XDHEPossession) poss).namedGroup;

                for (SSLCredentials cred : context.handshakeCredentials) {

                    if (!(cred instanceof XDHECredentials)) {

                        continue;

                    }

                    if (ng.equals(((XDHECredentials) cred).namedGroup)) {

                        xdheCredentials = (XDHECredentials) cred;

                        break;

                    }

                }

                if (xdheCredentials != null) {

                    xdhePossession = (XDHEPossession) poss;

                    break;

                }

            }

            if (xdhePossession == null || xdheCredentials == null) {

                context.conContext.fatal(Alert.HANDSHAKE_FAILURE,

                        "No sufficient XDHE key agreement "

                        + "parameters negotiated");

            }

            return new KAKeyDerivation("XDH", context,

                    xdhePossession.privateKey, xdheCredentials.popPublicKey);

        }

    }

}