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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

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 * 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.

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 * 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,

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package sun.security.ssl;

import java.io.IOException;

import java.security.AlgorithmConstraints;

import java.security.CryptoPrimitive;

import java.security.GeneralSecurityException;

import java.security.KeyFactory;

import java.security.KeyPair;

import java.security.KeyPairGenerator;

import java.security.PrivateKey;

import java.security.PublicKey;

import java.security.SecureRandom;

import java.security.interfaces.ECPrivateKey;

import java.security.interfaces.ECPublicKey;

import java.security.spec.AlgorithmParameterSpec;

import java.security.spec.ECGenParameterSpec;

import java.security.spec.ECParameterSpec;

import java.security.spec.ECPoint;

import java.security.spec.ECPublicKeySpec;

import java.util.EnumSet;

import javax.crypto.KeyAgreement;

import javax.crypto.SecretKey;

import javax.crypto.spec.SecretKeySpec;

import javax.net.ssl.SSLHandshakeException;

import sun.security.ssl.CipherSuite.HashAlg;

import sun.security.ssl.SupportedGroupsExtension.NamedGroup;

import sun.security.ssl.SupportedGroupsExtension.NamedGroupType;

import sun.security.ssl.SupportedGroupsExtension.SupportedGroups;

import sun.security.ssl.X509Authentication.X509Credentials;

import sun.security.ssl.X509Authentication.X509Possession;

import sun.security.util.ECUtil;

final class ECDHKeyExchange {

    static final SSLPossessionGenerator poGenerator =

            new ECDHEPossessionGenerator();

    static final SSLKeyAgreementGenerator ecdheKAGenerator =

            new ECDHEKAGenerator();

    static final SSLKeyAgreementGenerator ecdhKAGenerator =

            new ECDHKAGenerator();

    static final class ECDHECredentials implements SSLCredentials {

        final ECPublicKey popPublicKey;

        final NamedGroup namedGroup;

        ECDHECredentials(ECPublicKey popPublicKey, NamedGroup namedGroup) {

            this.popPublicKey = popPublicKey;

            this.namedGroup = namedGroup;

        }

        static ECDHECredentials valueOf(NamedGroup namedGroup,

            byte[] encodedPoint) throws IOException, GeneralSecurityException {

            if (namedGroup.type != NamedGroupType.NAMED_GROUP_ECDHE) {

                throw new RuntimeException(

                    "Credentials decoding:  Not ECDHE named group");

            }

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

                return null;

            }

            ECParameterSpec parameters =

                    JsseJce.getECParameterSpec(namedGroup.oid);

            if (parameters == null) {

                return null;

            }

            ECPoint point = JsseJce.decodePoint(

                    encodedPoint, parameters.getCurve());

            KeyFactory factory = JsseJce.getKeyFactory("EC");

            ECPublicKey publicKey = (ECPublicKey)factory.generatePublic(

                    new ECPublicKeySpec(point, parameters));

            return new ECDHECredentials(publicKey, namedGroup);

        }

    }

    static final class ECDHEPossession implements SSLPossession {

        final PrivateKey privateKey;

        final ECPublicKey publicKey;

        final NamedGroup namedGroup;

        ECDHEPossession(NamedGroup namedGroup, SecureRandom random) {

            try {

                KeyPairGenerator kpg = JsseJce.getKeyPairGenerator("EC");

                ECGenParameterSpec params =

                        (ECGenParameterSpec)namedGroup.getParameterSpec();

                kpg.initialize(params, random);

                KeyPair kp = kpg.generateKeyPair();

                privateKey = kp.getPrivate();

                publicKey = (ECPublicKey)kp.getPublic();

            } catch (GeneralSecurityException e) {

                throw new RuntimeException(

                    "Could not generate ECDH keypair", e);

            }

            this.namedGroup = namedGroup;

        }

        ECDHEPossession(ECDHECredentials credentials, SecureRandom random) {

            ECParameterSpec params = credentials.popPublicKey.getParams();

            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 ECDH keypair", e);

            }

            this.namedGroup = credentials.namedGroup;

        }

        @Override

        public byte[] encode() {

            return ECUtil.encodePoint(

                    publicKey.getW(), publicKey.getParams().getCurve());

        }

        // 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 pubKey = (ECPublicKey)kf.generatePublic(spec);

                // check constraints of ECPublicKey

                if (!constraints.permits(

                        EnumSet.of(CryptoPrimitive.KEY_AGREEMENT), pubKey)) {

                    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);

            }

        }

    }

    private static final

            class ECDHEPossessionGenerator implements SSLPossessionGenerator {

        // Prevent instantiation of this class.

        private ECDHEPossessionGenerator() {

            // blank

        }

        @Override

        public SSLPossession createPossession(HandshakeContext context) {

            NamedGroup preferableNamedGroup = null;

            if ((context.clientRequestedNamedGroups != null) &&

                    (!context.clientRequestedNamedGroups.isEmpty())) {

                preferableNamedGroup = SupportedGroups.getPreferredGroup(

                        context.negotiatedProtocol,

                        context.algorithmConstraints,

                        NamedGroupType.NAMED_GROUP_ECDHE,

                        context.clientRequestedNamedGroups);

            } else {

                preferableNamedGroup = SupportedGroups.getPreferredGroup(

                        context.negotiatedProtocol,

                        context.algorithmConstraints,

                        NamedGroupType.NAMED_GROUP_ECDHE);

            }

            if (preferableNamedGroup != null) {

                return new ECDHEPossession(preferableNamedGroup,

                            context.sslContext.getSecureRandom());

            }

            // no match found, cannot use this cipher suite.

            //

            return null;

        }

    }

    private static final

            class ECDHKAGenerator implements SSLKeyAgreementGenerator {

        // Prevent instantiation of this class.

        private ECDHKAGenerator() {

            // blank

        }

        @Override

        public SSLKeyDerivation createKeyDerivation(

                HandshakeContext context) throws IOException {

            if (context instanceof ServerHandshakeContext) {

                return createServerKeyDerivation(

                        (ServerHandshakeContext)context);

            } else {

                return createClientKeyDerivation(

                        (ClientHandshakeContext)context);

            }

        }

        private SSLKeyDerivation createServerKeyDerivation(

                ServerHandshakeContext shc) throws IOException {

            X509Possession x509Possession = null;

            ECDHECredentials ecdheCredentials = null;

            for (SSLPossession poss : shc.handshakePossessions) {

                if (!(poss instanceof X509Possession)) {

                    continue;

                }

                PrivateKey privateKey = ((X509Possession)poss).popPrivateKey;

                if (!privateKey.getAlgorithm().equals("EC")) {

                    continue;

                }

                ECParameterSpec params = ((ECPrivateKey)privateKey).getParams();

                NamedGroup ng = NamedGroup.valueOf(params);

                if (ng == null) {

                    // unlikely, have been checked during cipher suite negotiation.

                    shc.conContext.fatal(Alert.ILLEGAL_PARAMETER,

                        "Unsupported EC server cert for ECDH key exchange");

                }

                for (SSLCredentials cred : shc.handshakeCredentials) {

                    if (!(cred instanceof ECDHECredentials)) {

                        continue;

                    }

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

                        ecdheCredentials = (ECDHECredentials)cred;

                        break;

                    }

                }

                if (ecdheCredentials != null) {

                    x509Possession = (X509Possession)poss;

                    break;

                }

            }

            if (x509Possession == null || ecdheCredentials == null) {

                shc.conContext.fatal(Alert.HANDSHAKE_FAILURE,

                    "No sufficient ECDHE key agreement parameters negotiated");

            }

            return new ECDHEKAKeyDerivation(shc,

                x509Possession.popPrivateKey, ecdheCredentials.popPublicKey);

        }

        private SSLKeyDerivation createClientKeyDerivation(

                ClientHandshakeContext chc) throws IOException {

            ECDHEPossession ecdhePossession = null;

            X509Credentials x509Credentials = null;

            for (SSLPossession poss : chc.handshakePossessions) {

                if (!(poss instanceof ECDHEPossession)) {

                    continue;

                }

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

                for (SSLCredentials cred : chc.handshakeCredentials) {

                    if (!(cred instanceof X509Credentials)) {

                        continue;

                    }

                    PublicKey publicKey = ((X509Credentials)cred).popPublicKey;

                    if (!publicKey.getAlgorithm().equals("EC")) {

                        continue;

                    }

                    ECParameterSpec params =

                            ((ECPublicKey)publicKey).getParams();

                    NamedGroup namedGroup = NamedGroup.valueOf(params);

                    if (namedGroup == null) {

                        // unlikely, should have been checked previously

                        chc.conContext.fatal(Alert.ILLEGAL_PARAMETER,

                            "Unsupported EC server cert for ECDH key exchange");

                    }

                    if (ng.equals(namedGroup)) {

                        x509Credentials = (X509Credentials)cred;

                        break;

                    }

                }

                if (x509Credentials != null) {

                    ecdhePossession = (ECDHEPossession)poss;

                    break;

                }

            }

            if (ecdhePossession == null || x509Credentials == null) {

                chc.conContext.fatal(Alert.HANDSHAKE_FAILURE,

                    "No sufficient ECDH key agreement parameters negotiated");

            }

            return new ECDHEKAKeyDerivation(chc,

                ecdhePossession.privateKey, x509Credentials.popPublicKey);

        }

    }

    private static final

            class ECDHEKAGenerator implements SSLKeyAgreementGenerator {

        // Prevent instantiation of this class.

        private ECDHEKAGenerator() {

            // blank

        }

        @Override

        public SSLKeyDerivation createKeyDerivation(

                HandshakeContext context) throws IOException {

            ECDHEPossession ecdhePossession = null;

            ECDHECredentials ecdheCredentials = null;

            for (SSLPossession poss : context.handshakePossessions) {

                if (!(poss instanceof ECDHEPossession)) {

                    continue;

                }

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

                for (SSLCredentials cred : context.handshakeCredentials) {

                    if (!(cred instanceof ECDHECredentials)) {

                        continue;

                    }

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

                        ecdheCredentials = (ECDHECredentials)cred;

                        break;

                    }

                }

                if (ecdheCredentials != null) {

                    ecdhePossession = (ECDHEPossession)poss;

                    break;

                }

            }

            if (ecdhePossession == null || ecdheCredentials == null) {

                context.conContext.fatal(Alert.HANDSHAKE_FAILURE,

                    "No sufficient ECDHE key agreement parameters negotiated");

            }

            return new ECDHEKAKeyDerivation(context,

                ecdhePossession.privateKey, ecdheCredentials.popPublicKey);

        }

    }

    private static final

            class ECDHEKAKeyDerivation implements SSLKeyDerivation {

        private final HandshakeContext context;

        private final PrivateKey localPrivateKey;

        private final PublicKey peerPublicKey;

        ECDHEKAKeyDerivation(HandshakeContext context,

                PrivateKey localPrivateKey,

                PublicKey peerPublicKey) {

            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("ECDH");

                ka.init(localPrivateKey);

                ka.doPhase(peerPublicKey, true);

                SecretKey preMasterSecret =

                        ka.generateSecret("TlsPremasterSecret");

                SSLMasterKeyDerivation mskd =

                        SSLMasterKeyDerivation.valueOf(

                                context.negotiatedProtocol);

                SSLKeyDerivation kd = mskd.createKeyDerivation(

                        context, preMasterSecret);

            } 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("ECDH");

                ka.init(localPrivateKey);

                ka.doPhase(peerPublicKey, true);

                SecretKey sharedSecret =

                        ka.generateSecret("TlsPremasterSecret");

                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);

            }

        }

    }

}