/*

 * Copyright (c) 2015, 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

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

package sun.security.ssl;

import java.io.IOException;

import java.nio.charset.*;

import java.util.*;

import javax.net.ssl.*;

/*

 * [RFC 7301]

 * This TLS extension facilitates the negotiation of application-layer protocols

 * within the TLS handshake. Clients MAY include an extension of type

 * "application_layer_protocol_negotiation" in the (extended) ClientHello

 * message. The "extension_data" field of this extension SHALL contain a

 * "ProtocolNameList" value:

 *

 *     enum {

 *         application_layer_protocol_negotiation(16), (65535)

 *     } ExtensionType;

 *

 *     opaque ProtocolName<1..2^8-1>;

 *

 *     struct {

 *         ProtocolName protocol_name_list<2..2^16-1>

 *     } ProtocolNameList;

 */

final class ALPNExtension extends HelloExtension {

    final static int ALPN_HEADER_LENGTH = 1;

    final static int MAX_APPLICATION_PROTOCOL_LENGTH = 255;

    final static int MAX_APPLICATION_PROTOCOL_LIST_LENGTH = 65535;

    private int listLength = 0;     // ProtocolNameList length

    private List<String> protocolNames = null;

    // constructor for ServerHello

    ALPNExtension(String protocolName) throws SSLException {

        this(new String[]{ protocolName });

    }

    // constructor for ClientHello

    ALPNExtension(String[] protocolNames) throws SSLException {

        super(ExtensionType.EXT_ALPN);

        if (protocolNames.length == 0) { // never null, never empty

            throw new IllegalArgumentException(

                "The list of application protocols cannot be empty");

        }

        this.protocolNames = Arrays.asList(protocolNames);

        for (String p : protocolNames) {

            int length = p.getBytes(StandardCharsets.UTF_8).length;

            if (length == 0) {

                throw new SSLProtocolException(

                    "Application protocol name is empty");

            }

            if (length <= MAX_APPLICATION_PROTOCOL_LENGTH) {

                listLength += length + ALPN_HEADER_LENGTH;

            } else {

                throw new SSLProtocolException(

                    "Application protocol name is too long: " + p);

            }

            if (listLength > MAX_APPLICATION_PROTOCOL_LIST_LENGTH) {

                throw new SSLProtocolException(

                    "Application protocol name list is too long");

            }

        }

    }

    // constructor for ServerHello for parsing ALPN extension

    ALPNExtension(HandshakeInStream s, int len) throws IOException {

        super(ExtensionType.EXT_ALPN);

        if (len >= 2) {

            listLength = s.getInt16(); // list length

            if (listLength < 2 || listLength + 2 != len) {

                throw new SSLProtocolException(

                    "Invalid " + type + " extension: incorrect list length " +

                    "(length=" + listLength + ")");

            }

        } else {

            throw new SSLProtocolException(

                "Invalid " + type + " extension: insufficient data " +

                "(length=" + len + ")");

        }

        int remaining = listLength;

        this.protocolNames = new ArrayList<>();

        while (remaining > 0) {

            // opaque ProtocolName<1..2^8-1>; // RFC 7301

            byte[] bytes = s.getBytes8();

            if (bytes.length == 0) {

                throw new SSLProtocolException("Invalid " + type +

                    " extension: empty application protocol name");

            }

            String p =

                new String(bytes, StandardCharsets.UTF_8); // app protocol

            protocolNames.add(p);

            remaining -= bytes.length + ALPN_HEADER_LENGTH;

        }

        if (remaining != 0) {

            throw new SSLProtocolException(

                "Invalid " + type + " extension: extra data " +

                "(length=" + remaining + ")");

        }

    }

    List<String> getPeerAPs() {

        return protocolNames;

    }

    /*

     * Return the length in bytes, including extension type and length fields.

     */

    @Override

    int length() {

        return 6 + listLength;

    }

    @Override

    void send(HandshakeOutStream s) throws IOException {

        s.putInt16(type.id);

        s.putInt16(listLength + 2); // length of extension_data

        s.putInt16(listLength);     // length of ProtocolNameList

        for (String p : protocolNames) {

            s.putBytes8(p.getBytes(StandardCharsets.UTF_8));

        }

    }

    @Override

    public String toString() {

        StringBuilder sb = new StringBuilder();

        if (protocolNames == null || protocolNames.isEmpty()) {

            sb.append("<empty>");

        } else {

            for (String protocolName : protocolNames) {

                sb.append("[" + protocolName + "]");

            }

        }

        return "Extension " + type +

            ", protocol names: " + sb;

    }

}