/*
 * Copyright (c) 2020, Azul Systems, Inc. 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 com.sun.jndi.ldap.sasl;

import javax.naming.NamingException;
import javax.security.sasl.SaslException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.security.cert.CertificateEncodingException;
import java.security.cert.X509Certificate;
import java.util.Arrays;
import java.util.Hashtable;

This class implements the Channel Binding for TLS as defined in

    Channel Bindings for TLS
Format of the Channel Binding data is also defined in

    On the Use of Channel Bindings to Secure Channels
section 2.1.
/**
 * This class implements the Channel Binding for TLS as defined in
 * <a href="https://www.ietf.org/rfc/rfc5929.txt">
 *     Channel Bindings for TLS</a>
 *
 * Format of the Channel Binding data is also defined in
 * <a href="https://www.ietf.org/rfc/rfc5056.txt">
 *     On the Use of Channel Bindings to Secure Channels</a>
 * section 2.1.
 *
 */

public class TlsChannelBinding {

    // TLS channel binding type property
    public static final String CHANNEL_BINDING_TYPE =
            "com.sun.jndi.ldap.tls.cbtype";

    // internal TLS channel binding property
    public static final String CHANNEL_BINDING =
            "jdk.internal.sasl.tlschannelbinding";

    public enum TlsChannelBindingType {

        
Channel binding on the basis of TLS Finished message.
TLS_UNIQUE is defined by RFC 5929 but is not supported
by the current LDAP stack.
/**
         * Channel binding on the basis of TLS Finished message.
         * TLS_UNIQUE is defined by RFC 5929 but is not supported
         * by the current LDAP stack.
         */
        TLS_UNIQUE("tls-unique"),

        
Channel binding on the basis of TLS server certificate.
/**
         * Channel binding on the basis of TLS server certificate.
         */
        TLS_SERVER_END_POINT("tls-server-end-point");

        public String getName() {
            return name;
        }

        final private String name;
        TlsChannelBindingType(String name) {
            this.name = name;
        }
    }

    
Parse value of "com.sun.jndi.ldap.tls.cbtype" property
Params:
cbType – 
Throws:
NamingException – 
Returns:
TLS Channel Binding type or null if
        "com.sun.jndi.ldap.tls.cbtype" property has not been set./**
     * Parse value of "com.sun.jndi.ldap.tls.cbtype" property
     * @param  cbType
     * @return TLS Channel Binding type or null if
     *         "com.sun.jndi.ldap.tls.cbtype" property has not been set.
     * @throws NamingException
     */
    public static TlsChannelBindingType parseType(String cbType) throws NamingException {
        if (cbType != null) {
            if (cbType.equals(TlsChannelBindingType.TLS_SERVER_END_POINT.getName())) {
                return TlsChannelBindingType.TLS_SERVER_END_POINT;
            } else {
                throw new NamingException("Illegal value for " +
                        CHANNEL_BINDING_TYPE + " property.");
            }
        }
        return null;
    }

    final private TlsChannelBindingType cbType;
    final private byte[] cbData;

    
Construct tls-server-end-point Channel Binding data
Params:
serverCertificate – 
Throws:
SaslException – /**
     * Construct tls-server-end-point Channel Binding data
     * @param serverCertificate
     * @throws SaslException
     */
    public static TlsChannelBinding create(X509Certificate serverCertificate) throws SaslException {
        try {
            final byte[] prefix =
                TlsChannelBindingType.TLS_SERVER_END_POINT.getName().concat(":").getBytes();
            String hashAlg = serverCertificate.getSigAlgName().
                    replace("SHA", "SHA-").toUpperCase();
            int ind = hashAlg.indexOf("WITH");
            if (ind > 0) {
                hashAlg = hashAlg.substring(0, ind);
                if (hashAlg.equals("MD5") || hashAlg.equals("SHA-1")) {
                    hashAlg = "SHA-256";
                }
            } else {
                hashAlg = "SHA-256";
            }
            MessageDigest md = MessageDigest.getInstance(hashAlg);
            byte[] hash = md.digest(serverCertificate.getEncoded());
            byte[] cbData = Arrays.copyOf(prefix, prefix.length + hash.length );
            System.arraycopy(hash, 0, cbData, prefix.length, hash.length);
            return new TlsChannelBinding(TlsChannelBindingType.TLS_SERVER_END_POINT, cbData);
        } catch (NoSuchAlgorithmException | CertificateEncodingException e) {
            throw new SaslException("Cannot create TLS channel binding data", e);
        }
    }

    private TlsChannelBinding(TlsChannelBindingType cbType, byte[] cbData) {
        this.cbType = cbType;
        this.cbData = cbData;
    }

    public TlsChannelBindingType getType() {
        return cbType;
    }

    public byte[] getData() {
        return cbData;
    }
}