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/*
 * Copyright (C) 2006-2010 Alfresco Software Limited.
 *
 * This file is part of Alfresco
 *
 * Alfresco is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * Alfresco 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 Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with Alfresco. If not, see .
 */

package org.filesys.server.auth.kerberos;

import java.io.IOException;

import org.filesys.server.auth.asn.DERBuffer;
import org.filesys.server.auth.asn.DERGeneralizedTime;
import org.filesys.server.auth.asn.DERInteger;
import org.filesys.server.auth.asn.DERObject;
import org.filesys.server.auth.asn.DEROctetString;
import org.filesys.server.auth.asn.DERSequence;
import org.filesys.util.HexDump;

/**
 * Encrypted AP-REP Part Class
 *
 * @author gkspencer
 */
public class EncApRepPart {

    // AP-REP fields
    //
    // Microseconds
    private int m_microseconds;

    // Timestamp
    private String m_timestamp;

    // Sub-key
    private int m_subKeyType;
    private byte[] m_subKey;

    // Sequence number
    private int m_seqNo;

    /**
     * Default constructor
     */
    public EncApRepPart() {
    }

    /**
     * Class constructor
     *
     * @param blob byte[]
     * @exception IOException Error parsing security blob
     */
    public EncApRepPart(byte[] blob) throws IOException {
        parseApRep(blob);
    }

    /**
     * Return the timestamp
     *
     * @return String
     */
    public final String getTimestamp() {
        return m_timestamp;
    }

    /**
     * Return the sub-key type
     *
     * @return int
     */
    public final int getSubKeyType() {
        return m_subKeyType;
    }

    /**
     * Return the sub-key
     *
     * @return byte[]
     */
    public final byte[] getSubKey() {
        return m_subKey;
    }

    /**
     * Return the sequence number
     *
     * @return int
     */
    public final int getSequenceNumber() {
        return m_seqNo;
    }

    /**
     * Set the sub-key and type
     *
     * @param keyType int
     * @param subkey  byte[]
     */
    public final void setSubkey(int keyType, byte[] subkey) {
        m_subKeyType = keyType;
        m_subKey = subkey;
    }

    /**
     * Parse the ASN/1 encoded AP-REP encrypted part
     *
     * @param apRep byte[]
     * @exception IOException Error parsing security blob
     */
    public final void parseApRep(byte[] apRep)
            throws IOException {

        // Create a stream to parse the ASN.1 encoded blob
        DERBuffer derBuf = new DERBuffer(apRep);

        DERObject derObj = derBuf.unpackObject();
        if (derObj instanceof DERSequence) {

            // Enumerate the AP-REP objects
            DERSequence derSeq = (DERSequence) derObj;

            for (int idx = 0; idx < derSeq.numberOfObjects(); idx++) {

                // Read an object
                derObj = (DERObject) derSeq.getObjectAt(idx);

                if (derObj != null && derObj.isTagged()) {
                    switch (derObj.getTagNo()) {

                        // Timestamp
                        case 0:
                            if (derObj instanceof DERGeneralizedTime) {
                                DERGeneralizedTime derTime = (DERGeneralizedTime) derObj;
                                m_timestamp = derTime.getValue();
                            }
                            break;

                        // Microseconds
                        case 1:
                            if (derObj instanceof DERInteger) {
                                DERInteger derInt = (DERInteger) derObj;
                                m_microseconds = (int) derInt.getValue();
                            }
                            break;

                        // Sub-key
                        case 2:
                            if (derObj instanceof DERSequence) {
                                DERSequence derEncSeq = (DERSequence) derObj;

                                // Enumerate the sequence
                                for (int i = 0; i < derEncSeq.numberOfObjects(); i++) {

                                    // Get the current sequence element
                                    derObj = (DERObject) derEncSeq.getObjectAt(i);

                                    if (derObj != null && derObj.isTagged()) {
                                        switch (derObj.getTagNo()) {

                                            // Encryption key type
                                            case 0:
                                                if (derObj instanceof DERInteger) {
                                                    DERInteger derInt = (DERInteger) derObj;
                                                    m_subKeyType = (int) derInt.getValue();
                                                }
                                                break;

                                            // Encryption key
                                            case 1:
                                                if (derObj instanceof DEROctetString) {
                                                    DEROctetString derOct = (DEROctetString) derObj;
                                                    m_subKey = derOct.getValue();
                                                }
                                                break;
                                        }
                                    }
                                }
                            }
                            break;

                        // Sequence number
                        case 3:
                            if (derObj instanceof DERInteger) {
                                DERInteger derInt = (DERInteger) derObj;
                                m_seqNo = (int) derInt.getValue();
                            }
                            break;
                    }
                }
            }
        }
    }

    /**
     * ASN.1 encode the encrypted AP-REP blob
     *
     * @return byte[]
     * @exception IOException Error encoding security blob
     */
    public final byte[] encodeApRep()
            throws IOException {

        // Build the sequence of tagged objects
        DERSequence derList = new DERSequence();

        // Add the Kerberos time
        DERGeneralizedTime derTime = new DERGeneralizedTime(getTimestamp());
        derTime.setTagNo(0);
        derList.addObject(derTime);

        // Add the microseconds
        DERInteger derInt = new DERInteger(m_microseconds);
        derInt.setTagNo(1);
        derList.addObject(derInt);

        // Create the encryption key value
        DERSequence derSeq = new DERSequence(2);

        DERObject derObj = new DERInteger(m_subKeyType);
        derObj.setTagNo(0);
        derSeq.addObject(derObj);

        derObj = new DEROctetString(m_subKey);
        derObj.setTagNo(1);
        derSeq.addObject(derObj);

        // Add the sub-key
        derSeq.setTagNo(2);
        derList.addObject(derSeq);

        // Add the sequence number
        DERInteger derIntSeq = new DERInteger(m_seqNo);
        derIntSeq.setTagNo(3);
        derList.addObject(derIntSeq);

        // Pack the objects
        DERBuffer derBuf = new DERBuffer(256);
        derBuf.packApplicationSpecific(27, derList);

        // Return the packed encrypted part AP-REP blob
        return derBuf.getBytes();
    }

    /**
     * Return the AP-REP as a string
     *
     * @return String
     */
    public String toString() {
        StringBuilder str = new StringBuilder();

        str.append("[AP-REP uSec=");
        str.append(m_microseconds);
        str.append(",Time=");
        str.append(getTimestamp());
        str.append(",SubKey=Type=");
        str.append(getSubKeyType());
        str.append(",Key=");
        str.append(getSubKey() != null ? HexDump.hexString(getSubKey()) : "null");
        str.append(",SeqNo=");
        str.append(getSequenceNumber());
        str.append("]");

        return str.toString();
    }
}