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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
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 * accompanied this code).
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package sun.security.ec;

import sun.security.pkcs.PKCS8Key;

import java.security.*;
import java.security.interfaces.XECKey;
import java.security.interfaces.XECPrivateKey;
import java.security.interfaces.XECPublicKey;
import java.security.spec.AlgorithmParameterSpec;
import java.security.spec.NamedParameterSpec;
import java.security.spec.KeySpec;
import java.security.spec.InvalidKeySpecException;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;
import java.security.spec.XECPublicKeySpec;
import java.security.spec.XECPrivateKeySpec;
import java.util.Arrays;
import java.util.function.Function;

public class XDHKeyFactory extends KeyFactorySpi {

    private XECParameters lockedParams = null;

    XDHKeyFactory() {
        // do nothing
    }

    protected XDHKeyFactory(AlgorithmParameterSpec paramSpec) {
        lockedParams = XECParameters.get(ProviderException::new, paramSpec);
    }

    @Override
    protected Key engineTranslateKey(Key key) throws InvalidKeyException {

        if (key == null) {
            throw new InvalidKeyException("Key must not be null");
        }

        if (key instanceof XECKey) {
            XECKey xecKey = (XECKey) key;
            XECParameters params = XECParameters.get(InvalidKeyException::new,
                xecKey.getParams());
            checkLockedParams(InvalidKeyException::new, params);

            if (xecKey instanceof XECPublicKey) {
                XECPublicKey publicKey = (XECPublicKey) xecKey;
                return new XDHPublicKeyImpl(params, publicKey.getU());
            } else if (xecKey instanceof XECPrivateKey) {
                XECPrivateKey privateKey = (XECPrivateKey) xecKey;
                byte[] scalar = privateKey.getScalar().orElseThrow(
                    () -> new InvalidKeyException("No private key data"));
                return new XDHPrivateKeyImpl(params, scalar);
            } else {
                throw new InvalidKeyException("Unsupported XECKey subclass");
            }
        } else if (key instanceof PublicKey &&
                   key.getFormat().equals("X.509")) {
            XDHPublicKeyImpl result = new XDHPublicKeyImpl(key.getEncoded());
            checkLockedParams(InvalidKeyException::new, result.getParams());
            return result;
        } else if (key instanceof PrivateKey &&
                   key.getFormat().equals("PKCS#8")) {
            byte[] encoded = key.getEncoded();
            try {
                XDHPrivateKeyImpl result = new XDHPrivateKeyImpl(encoded);
                checkLockedParams(InvalidKeyException::new, result.getParams());
                return result;
            } finally {
                Arrays.fill(encoded, (byte)0);
            }
        } else {
            throw new InvalidKeyException("Unsupported key type or format");
        }
    }

    private
    <T extends Throwable>
    void checkLockedParams(Function<String, T> exception,
                           AlgorithmParameterSpec spec) throws T {

        XECParameters params = XECParameters.get(exception, spec);
        checkLockedParams(exception, params);
    }

    private
    <T extends Throwable>
    void checkLockedParams(Function<String, T> exception,
                           XECParameters params) throws T {

        if (lockedParams != null && lockedParams != params) {
            throw exception.apply("Parameters must be " +
                lockedParams.getName());
        }
    }

    @Override
    protected PublicKey engineGeneratePublic(KeySpec keySpec)
        throws InvalidKeySpecException {

        try {
             return generatePublicImpl(keySpec);
        } catch (InvalidKeyException ex) {
            throw new InvalidKeySpecException(ex);
        }
    }

    @Override
    protected PrivateKey engineGeneratePrivate(KeySpec keySpec)
        throws InvalidKeySpecException {

        try {
            return generatePrivateImpl(keySpec);
        } catch (InvalidKeyException ex) {
            throw new InvalidKeySpecException(ex);
        }
    }


    private PublicKey generatePublicImpl(KeySpec keySpec)
        throws InvalidKeyException, InvalidKeySpecException {

        return switch (keySpec) {
            case X509EncodedKeySpec x509Spec -> {
                XDHPublicKeyImpl result =
                    new XDHPublicKeyImpl(x509Spec.getEncoded());
                checkLockedParams(InvalidKeySpecException::new,
                    result.getParams());
                yield result;
            }
            case XECPublicKeySpec publicKeySpec -> {
                XECParameters params = XECParameters.get(
                    InvalidKeySpecException::new, publicKeySpec.getParams());
                checkLockedParams(InvalidKeySpecException::new, params);
                yield new XDHPublicKeyImpl(params, publicKeySpec.getU());
            }
            case PKCS8EncodedKeySpec p8 -> {
                PKCS8Key p8key = new XDHPrivateKeyImpl(p8.getEncoded());
                if (!p8key.hasPublicKey()) {
                    throw new InvalidKeySpecException("No public key found.");
                }
                XDHPublicKeyImpl result =
                    new XDHPublicKeyImpl(p8key.getPubKeyEncoded());
                checkLockedParams(InvalidKeySpecException::new,
                    result.getParams());
                yield result;
            }
            case null -> throw new InvalidKeySpecException(
                "keySpec must not be null");
            default ->
                throw new InvalidKeySpecException(keySpec.getClass().getName() +
                    " not supported.");
        };
    }

    private PrivateKey generatePrivateImpl(KeySpec keySpec)
        throws InvalidKeyException, InvalidKeySpecException {

        return switch (keySpec) {
            case PKCS8EncodedKeySpec pkcsSpec -> {
                byte[] encoded = pkcsSpec.getEncoded();
                try {
                    XDHPrivateKeyImpl result = new XDHPrivateKeyImpl(encoded);
                    checkLockedParams(InvalidKeySpecException::new,
                        result.getParams());
                    yield result;
                } finally {
                    Arrays.fill(encoded, (byte) 0);
                }
            }
            case XECPrivateKeySpec privateKeySpec -> {
                XECParameters params = XECParameters.get(
                    InvalidKeySpecException::new, privateKeySpec.getParams());
                checkLockedParams(InvalidKeySpecException::new, params);

                byte[] scalar = privateKeySpec.getScalar();
                try {
                    yield new XDHPrivateKeyImpl(params, scalar);
                } finally {
                    Arrays.fill(scalar, (byte) 0);
                }
            }
            case null -> throw new InvalidKeySpecException(
                "keySpec must not be null");
            default ->
                throw new InvalidKeySpecException(keySpec.getClass().getName() +
                    " not supported.");
        };
    }

    protected <T extends KeySpec> T engineGetKeySpec(Key key, Class<T> keySpec)
            throws InvalidKeySpecException {

        if (key instanceof XECPublicKey) {
            checkLockedParams(InvalidKeySpecException::new,
                ((XECPublicKey) key).getParams());

            if (keySpec.isAssignableFrom(X509EncodedKeySpec.class)) {
                if (!key.getFormat().equals("X.509")) {
                    throw new InvalidKeySpecException("Format is not X.509");
                }
                return keySpec.cast(new X509EncodedKeySpec(key.getEncoded()));
            } else if (keySpec.isAssignableFrom(XECPublicKeySpec.class)) {
                XECPublicKey xecKey = (XECPublicKey) key;
                return keySpec.cast(
                    new XECPublicKeySpec(xecKey.getParams(), xecKey.getU()));
            } else {
                throw new InvalidKeySpecException(
                    "KeySpec must be X509EncodedKeySpec or XECPublicKeySpec");
            }
        } else if (key instanceof XECPrivateKey) {
            checkLockedParams(InvalidKeySpecException::new,
                ((XECPrivateKey) key).getParams());

            if (keySpec.isAssignableFrom(PKCS8EncodedKeySpec.class)) {
                if (!key.getFormat().equals("PKCS#8")) {
                    throw new InvalidKeySpecException("Format is not PKCS#8");
                }
                byte[] encoded = key.getEncoded();
                try {
                    return keySpec.cast(new PKCS8EncodedKeySpec(encoded));
                } finally {
                    Arrays.fill(encoded, (byte)0);
                }
            } else if (keySpec.isAssignableFrom(XECPrivateKeySpec.class)) {
                XECPrivateKey xecKey = (XECPrivateKey) key;
                byte[] scalar = xecKey.getScalar().orElseThrow(
                    () -> new InvalidKeySpecException("No private key value")
                );
                try {
                    return keySpec.cast(
                            new XECPrivateKeySpec(xecKey.getParams(), scalar));
                } finally {
                    Arrays.fill(scalar, (byte)0);
                }
            } else {
                throw new InvalidKeySpecException
                ("KeySpec must be PKCS8EncodedKeySpec or XECPrivateKeySpec");
            }
        } else {
            throw new InvalidKeySpecException("Unsupported key type");
        }
    }

    static class X25519 extends XDHKeyFactory {

        public X25519() {
            super(NamedParameterSpec.X25519);
        }
    }

    static class X448 extends XDHKeyFactory {

        public X448() {
            super(NamedParameterSpec.X448);
        }
    }
}