/*
 * Copyright (c) 2018, 2020, 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.nio.ByteBuffer;
import java.text.MessageFormat;
import java.util.Collection;
import java.util.Collections;
import java.util.LinkedList;
import java.util.Locale;
import sun.security.ssl.SSLHandshake.HandshakeMessage;
import sun.security.util.HexDumpEncoder;

enum SSLExtension implements SSLStringizer {
    // Extensions defined in RFC 6066
    CH_SERVER_NAME          (0x0000,  "server_name",
                                SSLHandshake.CLIENT_HELLO,
                                ProtocolVersion.PROTOCOLS_TO_13,
                                ServerNameExtension.chNetworkProducer,
                                ServerNameExtension.chOnLoadConsumer,
                                null,
                                null,
                                null,
                                ServerNameExtension.chStringizer),
    SH_SERVER_NAME          (0x0000, "server_name",
                                SSLHandshake.SERVER_HELLO,
                                ProtocolVersion.PROTOCOLS_TO_12,
                                ServerNameExtension.shNetworkProducer,
                                ServerNameExtension.shOnLoadConsumer,
                                null,
                                null,
                                null,
                                ServerNameExtension.shStringizer),
    EE_SERVER_NAME          (0x0000, "server_name",
                                SSLHandshake.ENCRYPTED_EXTENSIONS,
                                ProtocolVersion.PROTOCOLS_OF_13,
                                ServerNameExtension.eeNetworkProducer,
                                ServerNameExtension.eeOnLoadConsumer,
                                null,
                                null,
                                null,
                                ServerNameExtension.shStringizer),
    CH_MAX_FRAGMENT_LENGTH (0x0001, "max_fragment_length",
                                SSLHandshake.CLIENT_HELLO,
                                ProtocolVersion.PROTOCOLS_TO_13,
                                MaxFragExtension.chNetworkProducer,
                                MaxFragExtension.chOnLoadConsumer,
                                null,
                                null,
                                null,
                                MaxFragExtension.maxFragLenStringizer),
    SH_MAX_FRAGMENT_LENGTH (0x0001, "max_fragment_length",
                                SSLHandshake.SERVER_HELLO,
                                ProtocolVersion.PROTOCOLS_TO_12,
                                MaxFragExtension.shNetworkProducer,
                                MaxFragExtension.shOnLoadConsumer,
                                null,
                                MaxFragExtension.shOnTradeConsumer,
                                null,
                                MaxFragExtension.maxFragLenStringizer),
    EE_MAX_FRAGMENT_LENGTH (0x0001, "max_fragment_length",
                                SSLHandshake.ENCRYPTED_EXTENSIONS,
                                ProtocolVersion.PROTOCOLS_OF_13,
                                MaxFragExtension.eeNetworkProducer,
                                MaxFragExtension.eeOnLoadConsumer,
                                null,
                                MaxFragExtension.eeOnTradeConsumer,
                                null,
                                MaxFragExtension.maxFragLenStringizer),
    CLIENT_CERTIFICATE_URL  (0x0002, "client_certificate_url"),
    TRUSTED_CA_KEYS         (0x0003, "trusted_ca_keys"),
    TRUNCATED_HMAC          (0x0004, "truncated_hmac"),

    CH_STATUS_REQUEST       (0x0005, "status_request",
                                SSLHandshake.CLIENT_HELLO,
                                ProtocolVersion.PROTOCOLS_TO_13,
                                CertStatusExtension.chNetworkProducer,
                                CertStatusExtension.chOnLoadConsumer,
                                null,
                                null,
                                null,
                                CertStatusExtension.certStatusReqStringizer),
    SH_STATUS_REQUEST       (0x0005, "status_request",
                                SSLHandshake.SERVER_HELLO,
                                ProtocolVersion.PROTOCOLS_TO_12,
                                CertStatusExtension.shNetworkProducer,
                                CertStatusExtension.shOnLoadConsumer,
                                null,
                                null,
                                null,
                                CertStatusExtension.certStatusReqStringizer),
    CR_STATUS_REQUEST       (0x0005, "status_request"),
    CT_STATUS_REQUEST       (0x0005, "status_request",
                                SSLHandshake.CERTIFICATE,
                                ProtocolVersion.PROTOCOLS_OF_13,
                                CertStatusExtension.ctNetworkProducer,
                                CertStatusExtension.ctOnLoadConsumer,
                                null,
                                null,
                                null,
                                CertStatusExtension.certStatusRespStringizer),

    // extensions defined in RFC 4681
    USER_MAPPING            (0x0006, "user_mapping"),

    // extensions defined in RFC 5878
    CLIENT_AUTHZ            (0x0007, "client_authz"),
    SERVER_AUTHZ            (0x0008, "server_authz"),

    // extensions defined in RFC 5081
    CERT_TYPE               (0x0009, "cert_type"),

    // extensions defined in RFC 4492 (ECC)
    CH_SUPPORTED_GROUPS     (0x000A, "supported_groups",
                                SSLHandshake.CLIENT_HELLO,
                                ProtocolVersion.PROTOCOLS_TO_13,
                                SupportedGroupsExtension.chNetworkProducer,
                                SupportedGroupsExtension.chOnLoadConsumer,
                                null,
                                null,
                                SupportedGroupsExtension.chOnTradAbsence,
                                SupportedGroupsExtension.sgsStringizer),
    EE_SUPPORTED_GROUPS     (0x000A, "supported_groups",
                                SSLHandshake.ENCRYPTED_EXTENSIONS,
                                ProtocolVersion.PROTOCOLS_OF_13,
                                SupportedGroupsExtension.eeNetworkProducer,
                                SupportedGroupsExtension.eeOnLoadConsumer,
                                null,
                                null,
                                null,
                                SupportedGroupsExtension.sgsStringizer),

    CH_EC_POINT_FORMATS     (0x000B, "ec_point_formats",
                                SSLHandshake.CLIENT_HELLO,
                                ProtocolVersion.PROTOCOLS_TO_12,
                                ECPointFormatsExtension.chNetworkProducer,
                                ECPointFormatsExtension.chOnLoadConsumer,
                                null,
                                null,
                                null,
                                ECPointFormatsExtension.epfStringizer),
    SH_EC_POINT_FORMATS     (0x000B, "ec_point_formats",
                                SSLHandshake.SERVER_HELLO,
                                ProtocolVersion.PROTOCOLS_TO_12,
                                null,   // not use of the producer
                                ECPointFormatsExtension.shOnLoadConsumer,
                                null,
                                null,
                                null,
                                ECPointFormatsExtension.epfStringizer),

    // extensions defined in RFC 5054
    SRP                     (0x000C, "srp"),

    // extensions defined in RFC 5246
    CH_SIGNATURE_ALGORITHMS (0x000D, "signature_algorithms",
                                SSLHandshake.CLIENT_HELLO,
                                ProtocolVersion.PROTOCOLS_12_13,
                                SignatureAlgorithmsExtension.chNetworkProducer,
                                SignatureAlgorithmsExtension.chOnLoadConsumer,
                                SignatureAlgorithmsExtension.chOnLoadAbsence,
                                SignatureAlgorithmsExtension.chOnTradeConsumer,
                                SignatureAlgorithmsExtension.chOnTradeAbsence,
                                SignatureAlgorithmsExtension.ssStringizer),
    CR_SIGNATURE_ALGORITHMS (0x000D, "signature_algorithms",
                                SSLHandshake.CERTIFICATE_REQUEST,
                                ProtocolVersion.PROTOCOLS_OF_13,
                                SignatureAlgorithmsExtension.crNetworkProducer,
                                SignatureAlgorithmsExtension.crOnLoadConsumer,
                                SignatureAlgorithmsExtension.crOnLoadAbsence,
                                SignatureAlgorithmsExtension.crOnTradeConsumer,
                                null,
                                SignatureAlgorithmsExtension.ssStringizer),

    CH_SIGNATURE_ALGORITHMS_CERT (0x0032, "signature_algorithms_cert",
                                SSLHandshake.CLIENT_HELLO,
                                ProtocolVersion.PROTOCOLS_12_13,
                                CertSignAlgsExtension.chNetworkProducer,
                                CertSignAlgsExtension.chOnLoadConsumer,
                                null,
                                CertSignAlgsExtension.chOnTradeConsumer,
                                null,
                                CertSignAlgsExtension.ssStringizer),
    CR_SIGNATURE_ALGORITHMS_CERT (0x0032, "signature_algorithms_cert",
                                SSLHandshake.CERTIFICATE_REQUEST,
                                ProtocolVersion.PROTOCOLS_OF_13,
                                CertSignAlgsExtension.crNetworkProducer,
                                CertSignAlgsExtension.crOnLoadConsumer,
                                null,
                                CertSignAlgsExtension.crOnTradeConsumer,
                                null,
                                CertSignAlgsExtension.ssStringizer),

    // extensions defined in RFC 5764
    USE_SRTP                (0x000E, "use_srtp"),

    // extensions defined in RFC 6520
    HEARTBEAT               (0x000E, "heartbeat"),

    // extension defined in RFC 7301 (ALPN)
    CH_ALPN                 (0x0010, "application_layer_protocol_negotiation",
                                SSLHandshake.CLIENT_HELLO,
                                ProtocolVersion.PROTOCOLS_TO_13,
                                AlpnExtension.chNetworkProducer,
                                AlpnExtension.chOnLoadConsumer,
                                AlpnExtension.chOnLoadAbsence,
                                null,
                                null,
                                AlpnExtension.alpnStringizer),
    SH_ALPN                 (0x0010, "application_layer_protocol_negotiation",
                                SSLHandshake.SERVER_HELLO,
                                ProtocolVersion.PROTOCOLS_TO_12,
                                AlpnExtension.shNetworkProducer,
                                AlpnExtension.shOnLoadConsumer,
                                AlpnExtension.shOnLoadAbsence,
                                null,
                                null,
                                AlpnExtension.alpnStringizer),
    EE_ALPN                 (0x0010, "application_layer_protocol_negotiation",
                                SSLHandshake.ENCRYPTED_EXTENSIONS,
                                ProtocolVersion.PROTOCOLS_OF_13,
                                AlpnExtension.shNetworkProducer,
                                AlpnExtension.shOnLoadConsumer,
                                AlpnExtension.shOnLoadAbsence,
                                null,
                                null,
                                AlpnExtension.alpnStringizer),

    // extensions defined in RFC 6961
    CH_STATUS_REQUEST_V2    (0x0011, "status_request_v2",
                                SSLHandshake.CLIENT_HELLO,
                                ProtocolVersion.PROTOCOLS_TO_12,
                                CertStatusExtension.chV2NetworkProducer,
                                CertStatusExtension.chV2OnLoadConsumer,
                                null,
                                null,
                                null,
                                CertStatusExtension.certStatusReqV2Stringizer),
    SH_STATUS_REQUEST_V2    (0x0011, "status_request_v2",
                                SSLHandshake.SERVER_HELLO,
                                ProtocolVersion.PROTOCOLS_TO_12,
                                CertStatusExtension.shV2NetworkProducer,
                                CertStatusExtension.shV2OnLoadConsumer,
                                null,
                                null,
                                null,
                                CertStatusExtension.certStatusReqV2Stringizer),

    // extensions defined in RFC 6962
    SIGNED_CERT_TIMESTAMP   (0x0012, "signed_certificate_timestamp"),

    // extensions defined in RFC 7250
    CLIENT_CERT_TYPE        (0x0013, "padding"),
    SERVER_CERT_TYPE        (0x0014, "server_certificate_type"),

    // extensions defined in RFC 7685
    PADDING                 (0x0015, "client_certificate_type"),

    // extensions defined in RFC 7366
    ENCRYPT_THEN_MAC        (0x0016, "encrypt_then_mac"),

    // extensions defined in RFC 7627
    CH_EXTENDED_MASTER_SECRET  (0x0017, "extended_master_secret",
                                SSLHandshake.CLIENT_HELLO,
                                ProtocolVersion.PROTOCOLS_TO_12,
                                ExtendedMasterSecretExtension.chNetworkProducer,
                                ExtendedMasterSecretExtension.chOnLoadConsumer,
                                ExtendedMasterSecretExtension.chOnLoadAbsence,
                                null,
                                null,
                                ExtendedMasterSecretExtension.emsStringizer),
    SH_EXTENDED_MASTER_SECRET  (0x0017, "extended_master_secret",
                                SSLHandshake.SERVER_HELLO,
                                ProtocolVersion.PROTOCOLS_TO_12,
                                ExtendedMasterSecretExtension.shNetworkProducer,
                                ExtendedMasterSecretExtension.shOnLoadConsumer,
                                ExtendedMasterSecretExtension.shOnLoadAbsence,
                                null,
                                null,
                                ExtendedMasterSecretExtension.emsStringizer),

    // extensions defined in RFC draft-ietf-tokbind-negotiation
    TOKEN_BINDING           (0x0018, "token_binding "),

    // extensions defined in RFC 7924
    CACHED_INFO             (0x0019, "cached_info"),

    // extensions defined in RFC 4507/5077
    SESSION_TICKET          (0x0023, "session_ticket"),

    // extensions defined in TLS 1.3
    CH_EARLY_DATA           (0x002A, "early_data"),
    EE_EARLY_DATA           (0x002A, "early_data"),
    NST_EARLY_DATA          (0x002A, "early_data"),

    CH_SUPPORTED_VERSIONS   (0x002B, "supported_versions",
                                SSLHandshake.CLIENT_HELLO,
                                ProtocolVersion.PROTOCOLS_TO_13,
                                SupportedVersionsExtension.chNetworkProducer,
                                SupportedVersionsExtension.chOnLoadConsumer,
                                null,
                                null,
                                null,
                                SupportedVersionsExtension.chStringizer),
    SH_SUPPORTED_VERSIONS   (0x002B, "supported_versions",
                                SSLHandshake.SERVER_HELLO,
                                        // and HelloRetryRequest
                                ProtocolVersion.PROTOCOLS_OF_13,
                                SupportedVersionsExtension.shNetworkProducer,
                                SupportedVersionsExtension.shOnLoadConsumer,
                                null,
                                null,
                                null,
                                SupportedVersionsExtension.shStringizer),
    HRR_SUPPORTED_VERSIONS  (0x002B, "supported_versions",
                                SSLHandshake.HELLO_RETRY_REQUEST,
                                ProtocolVersion.PROTOCOLS_OF_13,
                                SupportedVersionsExtension.hrrNetworkProducer,
                                SupportedVersionsExtension.hrrOnLoadConsumer,
                                null,
                                null,
                                null,
                                SupportedVersionsExtension.hrrStringizer),
    MH_SUPPORTED_VERSIONS   (0x002B, "supported_versions",
                                SSLHandshake.MESSAGE_HASH,
                                ProtocolVersion.PROTOCOLS_OF_13,
                                SupportedVersionsExtension.hrrReproducer,
                                null, null, null,
                                null,
                                SupportedVersionsExtension.hrrStringizer),

    CH_COOKIE               (0x002C, "cookie",
                                SSLHandshake.CLIENT_HELLO,
                                ProtocolVersion.PROTOCOLS_OF_13,
                                CookieExtension.chNetworkProducer,
                                CookieExtension.chOnLoadConsumer,
                                null,
                                CookieExtension.chOnTradeConsumer,
                                null,
                                CookieExtension.cookieStringizer),
    HRR_COOKIE              (0x002C, "cookie",
                                SSLHandshake.HELLO_RETRY_REQUEST,
                                ProtocolVersion.PROTOCOLS_OF_13,
                                CookieExtension.hrrNetworkProducer,
                                CookieExtension.hrrOnLoadConsumer,
                                null, null,
                                null,
                                CookieExtension.cookieStringizer),
    MH_COOKIE               (0x002C, "cookie",
                                SSLHandshake.MESSAGE_HASH,
                                ProtocolVersion.PROTOCOLS_OF_13,
                                CookieExtension.hrrNetworkReproducer,
                                null, null, null,
                                null,
                                CookieExtension.cookieStringizer),

    PSK_KEY_EXCHANGE_MODES  (0x002D, "psk_key_exchange_modes",
                                SSLHandshake.CLIENT_HELLO,
                                ProtocolVersion.PROTOCOLS_OF_13,
                                PskKeyExchangeModesExtension.chNetworkProducer,
                                PskKeyExchangeModesExtension.chOnLoadConsumer,
                                PskKeyExchangeModesExtension.chOnLoadAbsence,
                                null,
                                PskKeyExchangeModesExtension.chOnTradeAbsence,
                                PskKeyExchangeModesExtension.pkemStringizer),
    CERTIFICATE_AUTHORITIES (0x002F, "certificate_authorities"),
    OID_FILTERS             (0x0030, "oid_filters"),
    POST_HANDSHAKE_AUTH     (0x0030, "post_handshake_auth"),

    CH_KEY_SHARE            (0x0033, "key_share",
                                SSLHandshake.CLIENT_HELLO,
                                ProtocolVersion.PROTOCOLS_OF_13,
                                KeyShareExtension.chNetworkProducer,
                                KeyShareExtension.chOnLoadConsumer,
                                null,
                                null,
                                KeyShareExtension.chOnTradAbsence,
                                KeyShareExtension.chStringizer),
    SH_KEY_SHARE            (0x0033, "key_share",
                                SSLHandshake.SERVER_HELLO,
                                ProtocolVersion.PROTOCOLS_OF_13,
                                KeyShareExtension.shNetworkProducer,
                                KeyShareExtension.shOnLoadConsumer,
                                KeyShareExtension.shOnLoadAbsence,
                                null,
                                null,
                                KeyShareExtension.shStringizer),
    HRR_KEY_SHARE           (0x0033, "key_share",
                                SSLHandshake.HELLO_RETRY_REQUEST,
                                ProtocolVersion.PROTOCOLS_OF_13,
                                KeyShareExtension.hrrNetworkProducer,
                                KeyShareExtension.hrrOnLoadConsumer,
                                null, null, null,
                                KeyShareExtension.hrrStringizer),
    MH_KEY_SHARE            (0x0033, "key_share",
                                SSLHandshake.MESSAGE_HASH,
                                ProtocolVersion.PROTOCOLS_OF_13,
                                KeyShareExtension.hrrNetworkReproducer,
                                null, null, null, null,
                                KeyShareExtension.hrrStringizer),

    // Extensions defined in RFC 5746
    CH_RENEGOTIATION_INFO   (0xff01, "renegotiation_info",
                                SSLHandshake.CLIENT_HELLO,
                                ProtocolVersion.PROTOCOLS_TO_12,
                                RenegoInfoExtension.chNetworkProducer,
                                RenegoInfoExtension.chOnLoadConsumer,
                                RenegoInfoExtension.chOnLoadAbsence,
                                null,
                                null,
                                RenegoInfoExtension.rniStringizer),
    SH_RENEGOTIATION_INFO   (0xff01, "renegotiation_info",
                                SSLHandshake.SERVER_HELLO,
                                ProtocolVersion.PROTOCOLS_TO_12,
                                RenegoInfoExtension.shNetworkProducer,
                                RenegoInfoExtension.shOnLoadConsumer,
                                RenegoInfoExtension.shOnLoadAbsence,
                                null,
                                null,
                                RenegoInfoExtension.rniStringizer),

    // TLS 1.3 PSK extension must be last
    CH_PRE_SHARED_KEY       (0x0029, "pre_shared_key",
                                SSLHandshake.CLIENT_HELLO,
                                ProtocolVersion.PROTOCOLS_OF_13,
                                PreSharedKeyExtension.chNetworkProducer,
                                PreSharedKeyExtension.chOnLoadConsumer,
                                PreSharedKeyExtension.chOnLoadAbsence,
                                PreSharedKeyExtension.chOnTradeConsumer,
                                PreSharedKeyExtension.chOnTradAbsence,
                                PreSharedKeyExtension.chStringizer),
    SH_PRE_SHARED_KEY       (0x0029, "pre_shared_key",
                                SSLHandshake.SERVER_HELLO,
                                ProtocolVersion.PROTOCOLS_OF_13,
                                PreSharedKeyExtension.shNetworkProducer,
                                PreSharedKeyExtension.shOnLoadConsumer,
                                PreSharedKeyExtension.shOnLoadAbsence,
                                null, null,
                                PreSharedKeyExtension.shStringizer);

    final int id;
    final SSLHandshake handshakeType;
    final String name;
    final ProtocolVersion[] supportedProtocols;
    final HandshakeProducer networkProducer;
    final ExtensionConsumer onLoadConsumer;
    final HandshakeAbsence  onLoadAbsence;
    final HandshakeConsumer onTradeConsumer;
    final HandshakeAbsence  onTradeAbsence;
    final SSLStringizer stringizer;

    // known but unsupported extension
    private SSLExtension(int id, String name) {
        this.id = id;
        this.handshakeType = SSLHandshake.NOT_APPLICABLE;
        this.name = name;
        this.supportedProtocols = new ProtocolVersion[0];
        this.networkProducer = null;
        this.onLoadConsumer = null;
        this.onLoadAbsence = null;
        this.onTradeConsumer = null;
        this.onTradeAbsence = null;
        this.stringizer = null;
    }

    // supported extension
    private SSLExtension(int id, String name, SSLHandshake handshakeType,
            ProtocolVersion[] supportedProtocols,
            HandshakeProducer producer,
            ExtensionConsumer onLoadConsumer, HandshakeAbsence onLoadAbsence,
            HandshakeConsumer onTradeConsumer, HandshakeAbsence onTradeAbsence,
            SSLStringizer stringize) {
        this.id = id;
        this.handshakeType = handshakeType;
        this.name = name;
        this.supportedProtocols = supportedProtocols;
        this.networkProducer = producer;
        this.onLoadConsumer = onLoadConsumer;
        this.onLoadAbsence = onLoadAbsence;
        this.onTradeConsumer = onTradeConsumer;
        this.onTradeAbsence = onTradeAbsence;
        this.stringizer = stringize;
    }

    static SSLExtension valueOf(SSLHandshake handshakeType, int extensionType) {
        for (SSLExtension ext : SSLExtension.values()) {
            if (ext.id == extensionType &&
                    ext.handshakeType == handshakeType) {
                return ext;
            }
        }

        return null;
    }

    static String nameOf(int extensionType) {
        for (SSLExtension ext : SSLExtension.values()) {
            if (ext.id == extensionType) {
                return ext.name;
            }
        }

        return "unknown extension";
    }

    static boolean isConsumable(int extensionType) {
        for (SSLExtension ext : SSLExtension.values()) {
            if (ext.id == extensionType &&
                    ext.onLoadConsumer != null) {
                return true;
            }
        }

        return false;
    }

    public byte[] produce(ConnectionContext context,
            HandshakeMessage message) throws IOException {
        if (networkProducer != null) {
            return networkProducer.produce(context, message);
        } else {
            throw new UnsupportedOperationException(
                    "Not yet supported extension producing.");
        }
    }

    public void consumeOnLoad(ConnectionContext context,
            HandshakeMessage message, ByteBuffer buffer) throws IOException {
        if (onLoadConsumer != null) {
            onLoadConsumer.consume(context, message, buffer);
        } else {
            throw new UnsupportedOperationException(
                    "Not yet supported extension loading.");
        }
    }

    public void consumeOnTrade(ConnectionContext context,
            HandshakeMessage message) throws IOException {
        if (onTradeConsumer != null) {
            onTradeConsumer.consume(context, message);
        } else {
            throw new UnsupportedOperationException(
                    "Not yet supported extension processing.");
        }
    }

    void absentOnLoad(ConnectionContext context,
            HandshakeMessage message) throws IOException {
        if (onLoadAbsence != null) {
            onLoadAbsence.absent(context, message);
        } else {
            throw new UnsupportedOperationException(
                    "Not yet supported extension absence processing.");
        }
    }

    void absentOnTrade(ConnectionContext context,
            HandshakeMessage message) throws IOException {
        if (onTradeAbsence != null) {
            onTradeAbsence.absent(context, message);
        } else {
            throw new UnsupportedOperationException(
                    "Not yet supported extension absence processing.");
        }
    }

    public boolean isAvailable(ProtocolVersion protocolVersion) {
        for (int i = 0; i < supportedProtocols.length; i++) {
            if (supportedProtocols[i] == protocolVersion) {
                return true;
            }
        }

        return false;
    }

    @Override
    public String toString() {
        return name;
    }

    @Override
    public String toString(ByteBuffer byteBuffer) {
        MessageFormat messageFormat = new MessageFormat(
            "\"{0} ({1})\": '{'\n" +
            "{2}\n" +
            "'}'",
            Locale.ENGLISH);

        String extData;
        if (stringizer == null) {
            HexDumpEncoder hexEncoder = new HexDumpEncoder();
            String encoded = hexEncoder.encode(byteBuffer.duplicate());
            extData = encoded;
        } else {
            extData = stringizer.toString(byteBuffer);
        }

        Object[] messageFields = {
            this.name,
            this.id,
            Utilities.indent(extData)
        };

        return messageFormat.format(messageFields);
    }

    //////////////////////////////////////////////////////
    // Nested extension, consumer and producer interfaces.

    static interface ExtensionConsumer {
        void consume(ConnectionContext context,
                HandshakeMessage message, ByteBuffer buffer) throws IOException;
    }

    
A (transparent) specification of extension data.
This interface contains no methods or constants. Its only purpose is to
group all extension data.  All extension data should implement this
interface if the data is expected to handle in the following handshake
processes.
/**
     * A (transparent) specification of extension data.
     *
     * This interface contains no methods or constants. Its only purpose is to
     * group all extension data.  All extension data should implement this
     * interface if the data is expected to handle in the following handshake
     * processes.
     */
    static interface SSLExtensionSpec {
        // blank
    }

    // Default enabled client extensions.
    static final class ClientExtensions {
        static final Collection<SSLExtension> defaults;

        static {
            Collection<SSLExtension> extensions = new LinkedList<>();
            for (SSLExtension extension : SSLExtension.values()) {
                if (extension.handshakeType != SSLHandshake.NOT_APPLICABLE) {
                    extensions.add(extension);
                }
            }

            // Switch off SNI extention?
            boolean enableExtension =
                Utilities.getBooleanProperty("jsse.enableSNIExtension", true);
            if (!enableExtension) {
                extensions.remove(CH_SERVER_NAME);
            }

            // To switch off the max_fragment_length extension.
            //
            // Note that "jsse.enableMFLNExtension" is the CSR approved
            // property name.  However, "jsse.enableMFLExtension" was used
            // in the original implementation.  Temporarily, if either of
            // the two properties set to true, the extension is switch on.
            // We may remove the "jsse.enableMFLExtension" property in the
            // future.  Please don't continue to use the misspelling property.
            enableExtension =
                Utilities.getBooleanProperty(
                        "jsse.enableMFLNExtension", false) ||
                Utilities.getBooleanProperty(
                        "jsse.enableMFLExtension", false);
            if (!enableExtension) {
                extensions.remove(CH_MAX_FRAGMENT_LENGTH);
            }

            defaults = Collections.unmodifiableCollection(extensions);
        }
    }

    // Default enabled server extensions.
    static final class ServerExtensions {
        static final Collection<SSLExtension> defaults;

        static {
            Collection<SSLExtension> extensions = new LinkedList<>();
            for (SSLExtension extension : SSLExtension.values()) {
                if (extension.handshakeType != SSLHandshake.NOT_APPLICABLE) {
                    extensions.add(extension);
                }
            }

            defaults = Collections.unmodifiableCollection(extensions);
        }
    }
}