// NAME
   //      $RCSfile: SnmpContextv3Basis.java,v $
   // DESCRIPTION
   //      [given below in javadoc format]
   // DELTA
   //      $Revision: 3.17 $
   // CREATED
   //      $Date: 2009/03/05 15:51:42 $
   // COPYRIGHT
  //      Westhawk Ltd
  // TO DO
  //
  
  /*
   * Copyright (C) 2005 - 2006 by Westhawk Ltd
   * <a href="www.westhawk.co.uk">www.westhawk.co.uk</a>
   *
   * Permission to use, copy, modify, and distribute this software
   * for any purpose and without fee is hereby granted, provided
   * that the above copyright notices appear in all copies and that
   * both the copyright notice and this permission notice appear in
   * supporting documentation.
   * This software is provided "as is" without express or implied
   * warranty.
   */
  
  package uk.co.westhawk.snmp.stack;
  
  /*-
   * ╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲
   * SNMP Java Client
   * ჻჻჻჻჻჻
   * Copyright 2023 MetricsHub, Westhawk
   * ჻჻჻჻჻჻
   * This program 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.
   *
   * This program 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 Lesser Public License for more details.
   *
   * You should have received a copy of the GNU General Lesser Public
   * License along with this program.  If not, see
   * <http://www.gnu.org/licenses/lgpl-3.0.html>.
   * ╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱
   */
  
  import uk.co.westhawk.snmp.beans.UsmDiscoveryBean;
  import uk.co.westhawk.snmp.event.RequestPduListener;
  import uk.co.westhawk.snmp.pdu.DiscoveryPdu;
  import uk.co.westhawk.snmp.util.SnmpUtilities;
  
  import java.io.ByteArrayInputStream;
  import java.io.IOException;
  import java.util.Enumeration;
  import java.util.Hashtable;
  import java.util.function.BiFunction;
  
  /**
   * This class contains the basis for the SNMP v3 contexts that is needed 
   * by every PDU to send a SNMP v3 request.
   *
   * <p>
   * This class will perform the v3 discovery of the SNMP engine ID and
   * time line if necessary. This is done with the classes
   * <code>TimeWindow</code> and <code>UsmDiscoveryBean</code>.
   * </p>
   *
   * <p>
   * Now that the stack can send traps and receive requests, 
   * it needs to be able to act as an
   * authoritative SNMP engine. This is done via the interface UsmAgent.
   * The DefaultUsmAgent is not guaranteed to work; agents (or rather 
   * authoritative engines) <em>should</em> provide a better implementation.
   * </p>
   *
   * <p>
   * This class will use the User Security Model (USM) as described in 
   * <a href="http://www.ietf.org/rfc/rfc3414.txt">SNMP-USER-BASED-SM-MIB</a>.
   * See also <a href="http://www.ietf.org/rfc/rfc3411.txt">RFC 3411</a>.
   * </p>
   *
   * <p>
   * It is advised to set all the properties of this class before any PDU,
   * using this class, is sent. 
   * All properties are being used to encode the message. Some properties are 
   * being used to decode the Response or Report PDU. 
   * When any of these last properties were changed in between flight there 
   * is a possibility the decoding fails, causing a
   * <code>DecodingException</code>. 
   * </p>
   * 
   * <p>
   * <code>destroy()</code> should be called when the context is no longer
   * used. This is the only way the threads will be stopped and garbage
   * collected.
  * </p>
  *
  * @see SnmpContextv3Face
  * @see SnmpContextv3Pool
  * @see TimeWindow
  * @see UsmAgent
  * @see DefaultUsmAgent
  * @see #setUsmAgent(UsmAgent)
  * @see UsmDiscoveryBean
  *
  * @since 4_14
  * @author <a href="mailto:snmp@westhawk.co.uk">Birgit Arkesteijn</a>
  * @version $Revision: 3.17 $ $Date: 2009/03/05 15:51:42 $
  */
 public abstract class SnmpContextv3Basis extends AbstractSnmpContext
         implements SnmpContextv3Face, Cloneable {
     private static final String version_id = "@(#)$Id: SnmpContextv3Basis.java,v 3.17 2009/03/05 15:51:42 birgita Exp $ Copyright Westhawk Ltd";
 
     public static final int AES128_KEY_LENGTH = 16;
     public static final int AES192_KEY_LENGTH = 24;
     public static final int AES256_KEY_LENGTH = 32;
 
     protected String userName = DEFAULT_USERNAME;
     protected boolean useAuthentication = false;
     protected String userAuthenticationPassword;
     protected byte[] userAuthKeyMD5 = null;
     protected byte[] userAuthKeySHA1 = null;
     protected byte[] userAuthKeySHA256 = null;
     protected byte[] userAuthKeySHA512 = null;
     protected byte[] userAuthKeySHA224 = null;
     protected byte[] userAuthKeySHA384 = null;
     protected int authenticationProtocol = MD5_PROTOCOL;
     protected int privacyProtocol = DES_ENCRYPT;
     protected boolean usePrivacy = false;
     protected String userPrivacyPassword;
     protected byte[] userPrivKeyMD5 = null;
     protected byte[] userPrivKeySHA1 = null;
     protected byte[] userPrivKeySHA256 = null;
     protected byte[] userPrivKeySHA512 = null;
     protected byte[] userPrivKeySHA224 = null;
     protected byte[] userPrivKeySHA384 = null;
     protected byte[] contextEngineId = new byte[0];
     protected String contextName = DEFAULT_CONTEXT_NAME;
     protected UsmAgent usmAgent = null;
 
     private Hashtable msgIdHash = new Hashtable(MAXPDU);
     private static int next_id = 1;
 
     /**
      * Constructor.
      *
      * @param host The host to which the PDU will be sent
      * @param port The port where the SNMP server will be
      * @see AbstractSnmpContext#AbstractSnmpContext(String, int)
      */
     public SnmpContextv3Basis(String host, int port) throws IOException {
         this(host, port, null, STANDARD_SOCKET);
     }
 
     /**
      * Constructor.
      * Parameter typeSocketA should be either STANDARD_SOCKET, TCP_SOCKET or a
      * fully qualified classname.
      *
      * @param host        The host to which the Pdu will be sent
      * @param port        The port where the SNMP server will be
      * @param typeSocketA The local address the server will bind to
      *
      * @see AbstractSnmpContext#AbstractSnmpContext(String, int, String)
      */
     public SnmpContextv3Basis(String host, int port, String typeSocketA)
             throws IOException {
         this(host, port, null, typeSocketA);
     }
 
     /**
      * Constructor.
      * Parameter typeSocketA should be either STANDARD_SOCKET, TCP_SOCKET or a
      * fully qualified classname.
      *
      * @param host        The host to which the PDU will be sent
      * @param port        The port where the SNMP server will be
      * @param bindAddress The local address the server will bind to
      * @param typeSocketA The type of socket to use.
      *
      * @see AbstractSnmpContext#AbstractSnmpContext(String, int, String)
      * @see SnmpContextBasisFace#STANDARD_SOCKET
      * @see SnmpContextBasisFace#TCP_SOCKET
      * @since 4_14
      */
     public SnmpContextv3Basis(String host, int port, String bindAddress, String typeSocketA)
             throws IOException {
         super(host, port, bindAddress, typeSocketA);
 
         if (TimeWindow.getCurrent() == null) {
             TimeWindow timew = new TimeWindow();
         }
         setUsmAgent(createUsmAgent());
     }
 
     public int getVersion() {
         return SnmpConstants.SNMP_VERSION_3;
     }
 
     /**
      * Returns the username.
      *
      * @return the username
      */
     public String getUserName() {
         return userName;
     }
 
     /**
      * Sets the username.
      * This username will be used for all PDUs sent with this context.
      * The username corresponds to the 'msgUserName' in
      * <a href="http://www.ietf.org/rfc/rfc3414.txt">SNMP-USER-BASED-SM-MIB</a>.
      * The default value is "initial".
      *
      * @param newUserName The new username
      * @see #DEFAULT_USERNAME
      */
     public void setUserName(String newUserName) {
         userName = newUserName;
     }
 
     /**
      * Returns if authentication is used or not.
      * By default no authentication will be used.
      *
      * @return true if authentication is used, false if not
      */
     public boolean isUseAuthentication() {
         return useAuthentication;
     }
 
     /**
      * Sets whether authentication has to be used.
      * By default no authentication will be used.
      *
      * @param newUseAuthentication The use of authentication
      */
     public void setUseAuthentication(boolean newUseAuthentication) {
         useAuthentication = newUseAuthentication;
     }
 
     /**
      * Returns the user authentication password.
      * This password will be transformed into the user authentication secret key.
      *
      * @return The user authentication password
      */
     public String getUserAuthenticationPassword() {
         return userAuthenticationPassword;
     }
 
     /**
      * Sets the user authentication password.
      * This password will be transformed into the user authentication secret
      * key. A user MUST set this password.
      *
      * @param newUserAuthPassword The user authentication password
      */
     public void setUserAuthenticationPassword(String newUserAuthPassword) {
         if (newUserAuthPassword != null
                 &&
                 newUserAuthPassword.equals(userAuthenticationPassword) == false) {
             userAuthenticationPassword = newUserAuthPassword;
             userAuthKeyMD5 = null;
             userAuthKeySHA1 = null;
             userAuthKeySHA256 = null;
             userAuthKeySHA512 = null;
             userAuthKeySHA224 = null;
             userAuthKeySHA384 = null;
         }
     }
 
     /**
      * Sets the protocol to be used for authentication.
      * This can either be MD5 or SHA-1.
      * By default MD5 will be used.
      *
      * @param protocol The authentication protocol to be used
      * @see #MD5_PROTOCOL
      * @see #SHA1_PROTOCOL
      */
     public void setAuthenticationProtocol(int protocol)
             throws IllegalArgumentException {
         if (AUTH_PROTOCOLS.contains(protocol)) {
             if (protocol != authenticationProtocol) {
                 authenticationProtocol = protocol;
             }
         } else {
             throw new IllegalArgumentException("Authentication Protocol "
                     + "should be MD5 or SHA1 or SHA256 or SHA512 or SHA224 or SHA384");
         }
     }
 
     /**
      * Returns the protocol to be used for authentication.
      * This can either be MD5 or SHA-1.
      * By default MD5 will be used.
      *
      * @return The authentication protocol to be used
      * @see #MD5_PROTOCOL
      * @see #SHA1_PROTOCOL
      */
     public int getAuthenticationProtocol() {
         return authenticationProtocol;
     }
 
     /**
      * Sets the protocol to be used for privacy.
      * This can either be DES or AES.
      * By default DES will be used.
      *
      * @param protocol The privacy protocol to be used
      * @see SnmpContextv3Face#AES_ENCRYPT
      * @see SnmpContextv3Face#DES_ENCRYPT
      */
     public void setPrivacyProtocol(int protocol)
             throws IllegalArgumentException {
         if (PRIVACY_PROTOCOLS.contains(protocol)) {
             if (protocol != privacyProtocol) {
                 privacyProtocol = protocol;
             }
         } else {
             throw new IllegalArgumentException("Privacy Encryption "
                     + "should be AES, AES192, AES256 or DES");
         }
     }
 
     /**
      * Returns the protocol to be used for privacy.
      * This can either be DES or AES.
      * By default DES will be used.
      *
      * @return The privacy protocol to be used
      * @see SnmpContextv3Face#AES_ENCRYPT
      * @see SnmpContextv3Face#DES_ENCRYPT
      */
     public int getPrivacyProtocol() {
         return privacyProtocol;
     }
 
     byte[] getAuthenticationPasswordKeyMD5() {
         if (userAuthKeyMD5 == null) {
             userAuthKeyMD5 = SnmpUtilities.passwordToKeyMD5(userAuthenticationPassword);
         }
         return userAuthKeyMD5;
     }
 
     byte[] getAuthenticationPasswordKeySHA1() {
         if (userAuthKeySHA1 == null) {
             userAuthKeySHA1 = SnmpUtilities.passwordToKeySHA1(userAuthenticationPassword);
         }
         return userAuthKeySHA1;
     }
 
     /**
      * Returns the authentication password key for SHA256.
      * 
      * @return the authentication password key for SHA256
      */
     byte[] getAuthenticationPasswordKeySHA256() {
         if (userAuthKeySHA256 == null) {
             userAuthKeySHA256 = SnmpUtilities.passwordToKeySHA256(userAuthenticationPassword);
         }
         return userAuthKeySHA256;
     }
 
     /**
      * Returns the authentication password key for SHA-384.
      *
      * @return the authentication password key for SHA-384
      */
     byte[] getAuthenticationPasswordKeySHA384() {
         if (userAuthKeySHA384 == null) {
             userAuthKeySHA384 = SnmpUtilities.passwordToKeySHA384(userAuthenticationPassword);
         }
         return userAuthKeySHA384;
     }
 
     /**
      * Returns the authentication password key for SHA-224.
      *
      * @return the authentication password key for SHA-224
      */
     byte[] getAuthenticationPasswordKeySHA224() {
         if (userAuthKeySHA224 == null) {
             userAuthKeySHA224 = SnmpUtilities.passwordToKeySHA224(userAuthenticationPassword);
         }
         return userAuthKeySHA224;
     }
 
     /**
      * Returns the authentication password key for SHa512.
      *
      * @return the authentication password key for SHA512
      */
     byte[] getAuthenticationPasswordKeySHA512() {
         if (userAuthKeySHA512 == null) {
             userAuthKeySHA512 = SnmpUtilities.passwordToKeySHA512(userAuthenticationPassword);
         }
         return userAuthKeySHA512;
     }
 
     byte[] getPrivacyPasswordKeyMD5() {
         if (userPrivKeyMD5 == null) {
             userPrivKeyMD5 = SnmpUtilities.passwordToKeyMD5(userPrivacyPassword);
         }
         return userPrivKeyMD5;
     }
 
     byte[] getPrivacyPasswordKeySHA1() {
         if (userPrivKeySHA1 == null) {
             userPrivKeySHA1 = SnmpUtilities.passwordToKeySHA1(userPrivacyPassword);
         }
         return userPrivKeySHA1;
     }
 
     /**
      * Returns the privacy password key for SHA256.
      * 
      * @return the privacy password key for SHA256
      */
     byte[] getPrivacyPasswordKeySHA256() {
         if (userPrivKeySHA256 == null) {
             userPrivKeySHA256 = SnmpUtilities.passwordToKeySHA256(userPrivacyPassword);
         }
         return userPrivKeySHA256;
     }
 
     /**
      * Returns the privacy password key for SHA-224.
      *
      * @return the privacy password key for SHA-224
      */
     byte[] getPrivacyPasswordKeySHA224() {
         if (userPrivKeySHA224 == null) {
             userPrivKeySHA224 = SnmpUtilities.passwordToKeySHA224(userPrivacyPassword);
         }
         return userPrivKeySHA224;
     }
 
     /**
      * Returns the privacy password key for SHA-384.
      *
      * @return the privacy password key for SHA-384
      */
     byte[] getPrivacyPasswordKeySHA384() {
         if (userPrivKeySHA384 == null) {
             userPrivKeySHA384 = SnmpUtilities.passwordToKeySHA384(userPrivacyPassword);
         }
         return userPrivKeySHA384;
     }
 
     /**
      * Returns the privacy password key for SHA512.
      *
      * @return the privacy password key for SHA512
      */
     byte[] getPrivacyPasswordKeySHA512() {
         if (userPrivKeySHA512 == null) {
             userPrivKeySHA512 = SnmpUtilities.passwordToKeySHA512(userPrivacyPassword);
         }
         return userPrivKeySHA512;
     }
 
     /**
      * Returns if privacy is used or not.
      * By default privacy is not used.
      *
      * @return true if privacy is used, false if not
      */
     public boolean isUsePrivacy() {
         return usePrivacy;
     }
 
     /**
      * Sets whether privacy has to be used.
      * By default privacy is not used.
      * Note, privacy (encryption) without authentication is not allowed.
      *
      * @param newUsePrivacy The use of privacy
      */
     public void setUsePrivacy(boolean newUsePrivacy) {
         usePrivacy = newUsePrivacy;
     }
 
     /**
      * Returns the user privacy password.
      * This password will be transformed into the user privacy secret key.
      *
      * @return The user privacy password
      */
     public String getUserPrivacyPassword() {
         return userPrivacyPassword;
     }
 
     /**
      * Sets the user privacy password.
      * This password will be transformed into the user privacy secret
      * key. A user <em>must</em> set this password in order to use privacy.
      *
      * @param newUserPrivacyPassword The user privacy password
      */
     public void setUserPrivacyPassword(String newUserPrivacyPassword) {
         if (newUserPrivacyPassword != null
                 &&
                 newUserPrivacyPassword.equals(userPrivacyPassword) == false) {
             userPrivacyPassword = newUserPrivacyPassword;
             userPrivKeyMD5 = null;
             userPrivKeySHA1 = null;
             userPrivKeySHA256 = null;
             userPrivKeySHA512 = null;
             userPrivKeySHA224 = null;
             userPrivKeySHA384 = null;
         }
     }
 
     /**
      * Sets the contextEngineID.
      * See <a href="http://www.ietf.org/rfc/rfc3411.txt">RFC 3411</a>.
      *
      * A contextEngineID uniquely
      * identifies an SNMP entity that may realize an instance of a context
      * with a particular contextName.
      * 
      * <p>
      * Note, when the stack is an authoritative engine, this parameter should
      * equal the UsmAgent.getSnmpEngineId(). See the StackUsage
      * documentation for an explanation.
      * </p>
      *
      * <p>
      * If the contextEngineID is of length zero, the encoder will use the
      * (discovered)
      * snmpEngineId.
      * </p>
      *
      * @see UsmAgent#getSnmpEngineId()
      * @param newContextEngineId The contextEngineID
      */
     public void setContextEngineId(byte[] newContextEngineId)
             throws IllegalArgumentException {
         if (newContextEngineId != null) {
             contextEngineId = newContextEngineId;
         } else {
             throw new IllegalArgumentException("contextEngineId is null");
         }
     }
 
     /**
      * Returns the contextEngineID.
      *
      * @return The contextEngineID
      */
     public byte[] getContextEngineId() {
         return contextEngineId;
     }
 
     /**
      * Sets the contextName.
      * See <a href="http://www.ietf.org/rfc/rfc3411.txt">RFC 3411</a>.
      *
      * A contextName is used to name a context. Each contextName MUST be
      * unique within an SNMP entity.
      * By default this is "" (the empty String).
      *
      * @param newContextName The contextName
      * @see #DEFAULT_CONTEXT_NAME
      */
     public void setContextName(String newContextName) {
         contextName = newContextName;
     }
 
     /**
      * Returns the contextName.
      *
      * @return The contextName
      */
     public String getContextName() {
         return contextName;
     }
 
     /**
      * Adds a discovery pdu. This method adds the PDU (without checking if
      * discovery is needed).
      *
      * @param pdu the discovery pdu
      * @return pdu is succesful added
      * @see AbstractSnmpContext#addPdu(Pdu)
      * @see #addPdu(Pdu)
      */
     public boolean addDiscoveryPdu(DiscoveryPdu pdu)
             throws IOException, PduException {
         // since this is a DiscoveryPdu we do not check for discovery :-)
         return this.addPdu(pdu, false);
     }
 
     /**
      * Adds a PDU. This method adds the PDU and blocks until it has all the
      * discovery parameters it needs.
      *
      * @param pdu the PDU
      * @return pdu is succesful added
      * @see AbstractSnmpContext#addPdu(Pdu)
      * @see #addDiscoveryPdu(DiscoveryPdu)
      */
     public boolean addPdu(Pdu pdu)
             throws IOException, PduException {
         return this.addPdu(pdu, true);
     }
 
     /**
      * Creates the USM agent.
      * 
      * @see DefaultUsmAgent
      * @see #isAuthoritative
      */
     protected UsmAgent createUsmAgent() {
         return new DefaultUsmAgent();
     }
 
     /**
      * Sets the UsmAgent, needed when this stack is used as authoritative
      * SNMP engine. This interface provides authentiation details, like its
      * clock and its Engine ID.
      * 
      * @see DefaultUsmAgent
      * @param agent The USM authoritative interface
      * @since 4_14
      */
     public void setUsmAgent(UsmAgent agent) {
         usmAgent = agent;
     }
 
     /**
      * Returns the UsmAgent.
      * 
      * @see #setUsmAgent
      * @since 4_14
      */
     public UsmAgent getUsmAgent() {
         return usmAgent;
     }
 
     /**
      * Adds a PDU. This method adds the PDU and checks if discovery is
      * needed depending on the parameter <code>checkDiscovery</code>.
      * If discovery is needed this method will block until it has done so.
      * Discovery is only needed if the stack is non authoritative.
      *
      * <p>
      * This method stores the SNMPv3 msgId and PDU
      * request id in a Hashtable.
      * Since the encoding only happens once and every retry sends the same
      * encoded packet, only one msgId is used.
      * </p>
      *
      * @param pdu            the PDU
      * @param checkDiscovery check if discovery is needed
      * @return pdu is succesful added
      * @see AbstractSnmpContext#addPdu(Pdu)
      * @see #addDiscoveryPdu(DiscoveryPdu)
      * @see #addPdu(Pdu)
      */
     protected boolean addPdu(Pdu pdu, boolean checkDiscovery)
             throws IOException, PduException {
         // TODO, when sending response or report, the msgId should be set!
         Integer msgId = pdu.snmpv3MsgId;
         if (msgId == null) {
             msgId = new Integer(next_id++);
         } else if (pdu.isExpectingResponse() == true) {
             // generate a new msgId, even if this is already set. The user
             // could be adding the same PDU more than once to the
             // context.
             msgId = new Integer(next_id++);
         }
         pdu.snmpv3MsgId = msgId;
 
         msgIdHash.put(msgId, new Integer(pdu.req_id));
         if (AsnObject.debug > 6) {
             System.out.println(getClass().getName() + ".addPdu(): msgId="
                     + msgId.toString() + ", Pdu reqId=" + pdu.req_id);
         }
 
         if (checkDiscovery == true && isAuthoritative(pdu.getMsgType()) == false) {
             discoverIfNeeded(pdu);
         }
 
         boolean added = super.addPdu(pdu);
         return added;
     }
 
     /**
      * Removes a PDU. This removes the PDU from the AbstractSnmpContext and
      * clears the link with the SNMPv3 msgId.
      *
      * @param rid the PDU request id
      * @return whether the PDU has been successfully removed
      * @see AbstractSnmpContext#removePdu(int)
      */
     public synchronized boolean removePdu(int rid) {
         boolean removed = super.removePdu(rid);
         if (removed) {
             Enumeration keys = msgIdHash.keys();
             Integer msgIdI = null;
             boolean found = false;
             while (keys.hasMoreElements() && found == false) {
                 msgIdI = (Integer) keys.nextElement();
                 Integer pduIdI = (Integer) msgIdHash.get(msgIdI);
                 found = (pduIdI.intValue() == rid);
             }
             if (found) {
                 msgIdHash.remove(msgIdI);
             }
         }
         return removed;
     }
 
     /**
      * Encodes a discovery PDU packet. This methods encodes without checking
      * if the discovery parameters are all known.
      */
     public byte[] encodeDiscoveryPacket(byte msg_type, int rId, int errstat,
             int errind, Enumeration ve, Object obj)
             throws IOException, EncodingException {
         String engineId = "";
         TimeWindow tWindow = TimeWindow.getCurrent();
         if (tWindow.isSnmpEngineIdKnown(getSendToHostAddress(), hostPort) == true) {
             engineId = tWindow.getSnmpEngineId(getSendToHostAddress(), hostPort);
         }
         TimeWindowNode node = new TimeWindowNode(engineId, 0, 0);
 
         return actualEncodePacket(msg_type, rId, errstat, errind, ve, node,
                 obj);
     }
 
     /**
      * Encodes a PDU. This is for internal use only and should
      * NOT be called by the developer.
      * This is called by the the PDU itself and is added to the interface to
      * cover the different kind of Contexts.
      *
      * <p>
      * When the stack is
      * </p>
      * <ul>
      * <li>
      * authoritative, the timeline details are retrieved from the UsmAgent.
      * </li>
      * <li>
      * non authoritative, this methods first checks if all the discovery
      * parameters are known;
      * <ul>
      * <li>
      * If so, it encodes and returns the bytes.
      * </li>
      * <li>
      * If not, it will throw an EncodingException.
      * </li>
      * </ul>
      * </li>
      * </ul>
      *
      * @see #isAuthoritative(byte)
      * @param msg_type The message type
      * @param rId      The message id
      * @param errstat  The error status
      * @param errind   The error index
      * @param ve       The varbind list
      * @param obj      Additional object (only used in SNMPv3)
      * @return The encoded packet
      */
     public byte[] encodePacket(byte msg_type, int rId, int errstat,
             int errind, Enumeration ve, Object obj)
             throws IOException, EncodingException {
         TimeWindowNode node = null;
         if (isDestroyed == true) {
             throw new EncodingException("Context can no longer be used, since it is already destroyed");
         } else {
             TimeWindow tWindow = TimeWindow.getCurrent();
             if (isAuthoritative(msg_type) == true) {
                 usmAgent.setSnmpContext(this);
                 if (usmAgent.getSnmpEngineId() == null) {
                     throw new EncodingException("UsmAgent "
                             + usmAgent.getClass().getName()
                             + " should provide Engine ID!");
                 }
                 tWindow.updateTimeWindow(usmAgent.getSnmpEngineId(),
                         usmAgent.getSnmpEngineBoots(), usmAgent.getSnmpEngineTime(),
                         this.isUseAuthentication());
                 node = tWindow.getTimeLine(usmAgent.getSnmpEngineId());
             } else {
                 if (tWindow.isSnmpEngineIdKnown(getSendToHostAddress(), hostPort) == false) {
                     throw new EncodingException("Engine ID of host "
                             + getSendToHostAddress()
                             + ", port " + hostPort
                             + " is unknown (rId="
                             + rId + "). Perform discovery.");
                 }
                 String engineId = tWindow.getSnmpEngineId(getSendToHostAddress(), hostPort);
                 node = new TimeWindowNode(engineId, 0, 0);
 
                 if (isUseAuthentication()) {
                     if (tWindow.isTimeLineKnown(engineId) == true) {
                         node = tWindow.getTimeLine(engineId);
                     } else {
                         throw new EncodingException("Time Line of Engine ID of host "
                                 + getSendToHostAddress() + ", port " + hostPort + " is unknown. "
                                 + "Perform discovery.");
                     }
                 }
             }
         }
         return actualEncodePacket(msg_type, rId, errstat, errind, ve, node,
                 obj);
     }
 
     /**
      * Checks the sanity of the context and returns an error message when it
      * is not correct.
      */
     protected String checkContextSanity() {
         String ret = null;
         if (usePrivacy == true) {
             if (userPrivacyPassword == null) {
                 ret = "userPrivacyPassword is null, but usePrivacy is true";
             } else if (userPrivacyPassword.length() == 0) {
                 ret = "userPrivacyPassword is empty, but usePrivacy is true";
             } else if (useAuthentication == false) {
                 ret = "useAuthentication is false, but usePrivacy is true";
             }
         }
 
         if (useAuthentication == true) {
             if (userAuthenticationPassword == null) {
                 ret = "userAuthenticationPassword is null, but useAuthentication is true";
             } else if (userAuthenticationPassword.length() == 0) {
                 ret = "userAuthenticationPassword is empty, but useAuthentication is true";
             }
         }
         return ret;
     }
 
     /**
      * Does the actual encoding.
      *
      * @see #encodeDiscoveryPacket
      * @see #encodePacket
      */
     protected byte[] actualEncodePacket(byte msg_type, int rId, int errstat,
             int errind, Enumeration ve, TimeWindowNode node, Object obj)
             throws IOException, EncodingException {
         AsnEncoderv3 enc = new AsnEncoderv3();
         String msg = checkContextSanity();
         if (msg != null) {
             throw new EncodingException(msg);
         }
 
         int msgId = ((Integer) obj).intValue();
         if (AsnObject.debug > 6) {
             System.out.println(getClass().getName() + ".actualEncodePacket(): msgId="
                     + msgId + ", Pdu reqId=" + rId);
         }
         byte[] packet = enc.EncodeSNMPv3(this, msgId, node,
                 msg_type, rId, errstat, errind, ve);
 
         return packet;
     }
 
     /**
      * Processes an incoming SNMP v3 response.
      */
     protected void processIncomingResponse(ByteArrayInputStream in)
             throws DecodingException, IOException {
         AsnDecoderv3 rpdu = new AsnDecoderv3();
         // don't have to check for context sanity here: if the request was
         // fine, so should be the response
         byte[] bu = null;
         // need to duplicate the message for V3 to rewrite
         int nb = in.available();
         bu = new byte[nb];
         in.read(bu);
         in = new ByteArrayInputStream(bu);
 
         AsnSequence asnTopSeq = rpdu.DecodeSNMPv3(in);
         int msgId = rpdu.getMessageId(asnTopSeq);
         Integer rid = (Integer) msgIdHash.get(new Integer(msgId));
         if (rid != null) {
             if (AsnObject.debug > 6) {
                 System.out.println(getClass().getName() + ".processIncomingResponse(): msgId="
                         + msgId + ", Pdu reqId=" + rid);
             }
             Pdu pdu = getPdu(rid);
             try {
                 AsnPduSequence pduSeq = rpdu.processSNMPv3(this, asnTopSeq, bu, false);
                 if (pduSeq != null) {
                     // got a message
                     Integer rid2 = new Integer(pduSeq.getReqId());
                     if (AsnObject.debug > 6) {
                         System.out.println(getClass().getName() + ".processIncomingResponse():"
                                 + " rid2=" + rid2);
                     }
 
                     Pdu newPdu = null;
                     if (rid2.intValue() != rid.intValue()) {
                         newPdu = getPdu(rid2);
                         if (AsnObject.debug > 3) {
                             System.out.println(getClass().getName() + ".processIncomingResponse(): "
                                     + "pduReqId of msgId (" + rid.intValue()
                                     + ") != pduReqId of Pdu (" + rid2.intValue()
                                     + ")");
                         }
                         if (newPdu == null) {
                             if (AsnObject.debug > 3) {
                                 System.out.println(getClass().getName() + ".processIncomingResponse(): "
                                         + "Using pduReqId of msgId (" + rid.intValue() + ")");
                             }
                         }
                     }
 
                     if (newPdu != null) {
                         pdu = newPdu;
                     }
                 } else {
                     if (AsnObject.debug > 6) {
                         System.out.println(getClass().getName() + ".processIncomingResponse():"
                                 + " pduSeq is null.");
                     }
                 }
 
                 if (pdu != null) {
                     pdu.fillin(pduSeq);
                 } else {
                     if (AsnObject.debug > 6) {
                         System.out.println(getClass().getName() + ".processIncomingResponse(): No Pdu with reqid "
                                 + rid.intValue());
                     }
                 }
             } catch (DecodingException exc) {
                 if (pdu != null) {
                     pdu.setErrorStatus(AsnObject.SNMP_ERR_DECODING_EXC, exc);
                     pdu.fillin(null);
                 } else {
                     throw exc;
                 }
             }
         } else {
             if (AsnObject.debug > 3) {
                 System.out.println(getClass().getName() + ".processIncomingResponse(): Pdu of msgId " + msgId
                         + " is already answered");
             }
             rid = new Integer(-1);
         }
     }
 
     /**
      * Returns if we send this PDU in authoritative role or not.
      * The engine who sends a Response, a Trapv2 or a Report is
      * authoritative.
      *
      * @since 4_14
      * @return true if authoritative, false if not.
      */
     // Note: for when adding INFORM
     // When sending an INFORM, the receiver is the authoritative engine, so
     // the INFORM does NOT have to be added to this list!
     protected boolean isAuthoritative(byte msg_type) {
         return (msg_type == AsnObject.GET_RSP_MSG
                 ||
                 msg_type == AsnObject.TRPV2_REQ_MSG
                 ||
                 msg_type == AsnObject.GET_RPRT_MSG);
     }
 
     void discoverIfNeeded(Pdu pdu)
             throws IOException, PduException {
         UsmDiscoveryBean discBean = null;
         boolean isNeeded = false;
 
         TimeWindow tWindow = TimeWindow.getCurrent();
         String engineId = tWindow.getSnmpEngineId(getSendToHostAddress(), hostPort);
         if (engineId == null) {
             isNeeded = true;
             discBean = new UsmDiscoveryBean(
                     getSendToHostAddress(), hostPort, bindAddr, typeSocket);
             discBean.setRetryIntervals(pdu.getRetryIntervals());
         }
 
         if (isUseAuthentication()) {
             if (isNeeded) {
                 discBean.setAuthenticationDetails(userName,
                         userAuthenticationPassword, authenticationProtocol);
             } else if (tWindow.isTimeLineKnown(engineId) == false) {
                 isNeeded = true;
                 discBean = new UsmDiscoveryBean(
                         getSendToHostAddress(), hostPort, bindAddr, typeSocket);
                 discBean.setAuthenticationDetails(userName,
                         userAuthenticationPassword, authenticationProtocol);
                 discBean.setRetryIntervals(pdu.getRetryIntervals());
             }
 
             if (isNeeded && isUsePrivacy()) {
                 discBean.setPrivacyDetails(userPrivacyPassword, privacyProtocol);
             }
         }
 
         if (isNeeded) {
             discBean.startDiscovery();
 
         }
 
         // If contextEngineId is null or of length zero, set
         // it to the snmpEngineId.
         if (contextEngineId == null || contextEngineId.length == 0) {
             engineId = tWindow.getSnmpEngineId(getSendToHostAddress(), hostPort);
             setContextEngineId(SnmpUtilities.toBytes(engineId));
         }
     }
 
     /**
      * Adds the specified request pdu listener to receive PDUs on the
      * specified listening context that matches this context.
      * This method will call usmAgent.setSnmpContext(this).
      *
      * <p>
      * Don't use the TCP_SOCKET when listening for request PDUs. It doesn't
      * provide functionality to send a response back.
      * </p>
      *
      * @see AbstractSnmpContext#addRequestPduListener(RequestPduListener,
      *      ListeningContextPool)
      *
      * @param l        The request PDU listener
      * @param lcontext The listening context
      */
     public void addRequestPduListener(RequestPduListener l, ListeningContextPool lcontext)
             throws IOException {
         super.addRequestPduListener(l, lcontext);
 
         usmAgent.setSnmpContext(this);
         TimeWindow tWindow = TimeWindow.getCurrent();
         if (usmAgent.getSnmpEngineId() == null) {
             throw new IOException("UsmAgent "
                     + usmAgent.getClass().getName()
                     + " should provide Engine ID!");
         }
         tWindow.setSnmpEngineId(usmAgent.MYFAKEHOSTNAME, hostPort, usmAgent.getSnmpEngineId());
         tWindow.updateTimeWindow(usmAgent.getSnmpEngineId(),
                 usmAgent.getSnmpEngineBoots(), usmAgent.getSnmpEngineTime(),
                 this.isUseAuthentication());
     }
 
     /**
      * Copies all parameters into another SnmpContextv3.
      */
     public Object cloneParameters(SnmpContextv3Face clContext) {
         clContext.setUserName(new String(userName));
         clContext.setUseAuthentication(useAuthentication);
         if (userAuthenticationPassword != null) {
             clContext.setUserAuthenticationPassword(
                     new String(userAuthenticationPassword));
         }
         clContext.setAuthenticationProtocol(authenticationProtocol);
 
         clContext.setUsePrivacy(usePrivacy);
         if (userPrivacyPassword != null) {
             clContext.setUserPrivacyPassword(new String(userPrivacyPassword));
         }
         clContext.setPrivacyProtocol(privacyProtocol);
 
         clContext.setContextName(new String(contextName));
 
         int l = contextEngineId.length;
         byte[] newContextEngineId = new byte[l];
         System.arraycopy(contextEngineId, 0, newContextEngineId, 0, l);
         clContext.setContextEngineId(newContextEngineId);
 
         clContext.setUsmAgent(usmAgent);
         return clContext;
     }
 
     /**
      * Returns the hash key. This key is built out of all properties. It
      * serves as key for a hashtable of (v3) contexts.
      *
      * @since 4_14
      * @return The hash key
      */
     public String getHashKey() {
         StringBuffer buffer = new StringBuffer();
         buffer.append(hostname);
         buffer.append("_").append(hostPort);
         buffer.append("_").append(bindAddr);
         buffer.append("_").append(typeSocket);
         buffer.append("_").append(useAuthentication);
         buffer.append("_").append(PROTOCOL_NAMES[authenticationProtocol]);
         buffer.append("_").append(PROTOCOL_NAMES[privacyProtocol]);
         buffer.append("_").append(userAuthenticationPassword);
         buffer.append("_").append(userName);
         buffer.append("_").append(usePrivacy);
         buffer.append("_").append(userPrivacyPassword);
         buffer.append("_").append(SnmpUtilities.toHexString(contextEngineId));
         buffer.append("_").append(contextName);
         buffer.append("_v").append(getVersion());
 
         return buffer.toString();
     }
 
     /**
      * Returns a string representation of the object.
      * 
      * @return The string
      */
     public String toString() {
         StringBuffer buffer = new StringBuffer(getClass().getName() + "[");
         buffer.append("host=").append(hostname);
         buffer.append(", sendToHost=").append(getSendToHostAddress());
         buffer.append(", port=").append(hostPort);
         buffer.append(", bindAddress=").append(bindAddr);
         buffer.append(", socketType=").append(typeSocket);
         buffer.append(", contextEngineId=").append(SnmpUtilities.toHexString(contextEngineId));
         buffer.append(", contextName=").append(contextName);
         buffer.append(", userName=").append(userName);
         buffer.append(", useAuthentication=").append(useAuthentication);
         buffer.append(", authenticationProtocol=").append(PROTOCOL_NAMES[authenticationProtocol]);
         buffer.append(", userAuthenticationPassword=").append(userAuthenticationPassword);
         buffer.append(", usePrivacy=").append(usePrivacy);
         buffer.append(", privacyProtocol=").append(PROTOCOL_NAMES[privacyProtocol]);
         buffer.append(", userPrivacyPassword=").append(userPrivacyPassword);
         buffer.append(", #trapListeners=").append(trapSupport.getListenerCount());
         buffer.append(", #pduListeners=").append(pduSupport.getListenerCount());
         buffer.append("]");
         return buffer.toString();
     }
 
     /**
      * Generates the privacy key based on the authentication protocol.
      *
      * @param engineId               The SNMP engine ID.
      * @param authenticationProtocol The authentication protocol.
      * @param privacyProtocol        The privacyProtocol.
      * @return The generated privacy key.
      */
 	protected byte[] generatePrivacyKey(String engineId, int authenticationProtocol, int privacyProtocol) {
 		byte[] derivedPrivacyKey;
 		byte[] localizedPrivacyKey = null;
 		switch (authenticationProtocol) {
 			case MD5_PROTOCOL:
 				if (privacyProtocol != AES_ENCRYPT && privacyProtocol != DES_ENCRYPT) {
 					throw new IllegalArgumentException(
 							"Unsupported privacy protocol for MD5: " + PROTOCOL_NAMES[privacyProtocol]);
 				}
 				derivedPrivacyKey = getPrivacyPasswordKeyMD5();
 				return SnmpUtilities.getLocalizedKeyMD5(derivedPrivacyKey, engineId);
 			case SHA1_PROTOCOL:
 				if (privacyProtocol != AES_ENCRYPT && privacyProtocol != DES_ENCRYPT) {
 					throw new IllegalArgumentException(
 							"Unsupported privacy protocol for SHA1: " + PROTOCOL_NAMES[privacyProtocol]);
 				}
 				derivedPrivacyKey = getPrivacyPasswordKeySHA1();
 				return SnmpUtilities.getLocalizedKeySHA1(derivedPrivacyKey, engineId);
 			case SHA224_PROTOCOL: {
 				if (privacyProtocol != AES_ENCRYPT && privacyProtocol != DES_ENCRYPT
 						&& privacyProtocol != AES192_ENCRYPT) {
 					throw new IllegalArgumentException(
 							"Unsupported privacy protocol for SHA224: " + PROTOCOL_NAMES[privacyProtocol]);
 				}
 				derivedPrivacyKey = getPrivacyPasswordKeySHA224();
 				return SnmpUtilities.getLocalizedKeySHA224(derivedPrivacyKey, engineId);
 			}
 			case SHA256_PROTOCOL: {
 				derivedPrivacyKey = getPrivacyPasswordKeySHA256();
 				localizedPrivacyKey = deriveKey(engineId, derivedPrivacyKey, SnmpUtilities::getLocalizedKeySHA256,
 						privacyProtocol);
 				return localizedPrivacyKey;
 			}
 			case SHA384_PROTOCOL: {
 				derivedPrivacyKey = getPrivacyPasswordKeySHA384();
 				localizedPrivacyKey = deriveKey(engineId, derivedPrivacyKey, SnmpUtilities::getLocalizedKeySHA384,
 						privacyProtocol);
 				return localizedPrivacyKey;
 			}
 			case SHA512_PROTOCOL: {
 				derivedPrivacyKey = getPrivacyPasswordKeySHA512();
 				localizedPrivacyKey = deriveKey(engineId, derivedPrivacyKey, SnmpUtilities::getLocalizedKeySHA512,
 						privacyProtocol);
 				return localizedPrivacyKey;
 			}
 			default:
 				throw new IllegalArgumentException("Unsupported authentication protocol: " + authenticationProtocol);
 			}
 	}
     
     /**
      * Derives a final privacy key
      *
      * @param engineId          The SNMP engine ID.
      * @param derivedPrivacyKey The SNMP engine ID.
      * @param localizeKey         A function that localizes the key using the derived key and engine ID.
      * @param privacyProtocol   The privacyProtocol
      * @return The derived privacy key.
      */
     private static byte[] deriveKey(
     		String engineId,
     		byte[] derivedPrivacyKey,
     		BiFunction<byte[],
     		String, byte[]> localizeKey,
     		int privacyProtocol) {
         byte[] localizedPrivacyKeyBase = localizeKey.apply(derivedPrivacyKey, engineId);
         switch (privacyProtocol) {
             case AES_ENCRYPT:
             case AES192_ENCRYPT:
             case AES256_ENCRYPT:
             case DES_ENCRYPT:
 				return localizedPrivacyKeyBase;
             default:
                 throw new IllegalArgumentException("Unsupported privacy protocol: " + PROTOCOL_NAMES[privacyProtocol]);
         }
      }
  
 
     /**
      * Computes the fingerprint for the given SNMP message.
      *
      * @param snmpEngineId           The SNMP engine ID.
      * @param authenticationProtocol The authentication protocol.
      * @param computedFingerprint    The computed fingerprint.
      * @param message                The SNMP message.
      * @return The computed fingerprint.
      */
     protected byte[] computeFingerprint(String snmpEngineId, int authenticationProtocol, byte[] computedFingerprint,
             byte[] message) {
         if (authenticationProtocol == MD5_PROTOCOL) {
             byte[] passwKey = getAuthenticationPasswordKeyMD5();
             byte[] authkey = SnmpUtilities.getLocalizedKeyMD5(passwKey, snmpEngineId);
             computedFingerprint = SnmpUtilities.getFingerPrintMD5(authkey, message);
         } else if (authenticationProtocol == SHA1_PROTOCOL) {
             byte[] passwKey = getAuthenticationPasswordKeySHA1();
             byte[] authkey = SnmpUtilities.getLocalizedKeySHA1(passwKey, snmpEngineId);
             computedFingerprint = SnmpUtilities.getFingerPrintSHA1(authkey, message);
         } else if (authenticationProtocol == SHA256_PROTOCOL) {
             byte[] passwKey = getAuthenticationPasswordKeySHA256();
             byte[] authkey = SnmpUtilities.getLocalizedKeySHA256(passwKey, snmpEngineId);
             computedFingerprint = SnmpUtilities.getFingerPrintSHA256(authkey, message);
         } else if (authenticationProtocol == SHA512_PROTOCOL) {
             byte[] passwKey = getAuthenticationPasswordKeySHA512();
             byte[] authkey = SnmpUtilities.getLocalizedKeySHA512(passwKey, snmpEngineId);
             computedFingerprint = SnmpUtilities.getFingerPrintSHA512(authkey, message);
         } else if (authenticationProtocol == SHA224_PROTOCOL) {
             byte[] passwKey = getAuthenticationPasswordKeySHA224();
             byte[] authkey = SnmpUtilities.getLocalizedKeySHA224(passwKey, snmpEngineId);
             computedFingerprint = SnmpUtilities.getFingerPrintSHA224(authkey, message);
         } else if (authenticationProtocol == SHA384_PROTOCOL) {
             byte[] passwKey = getAuthenticationPasswordKeySHA384();
             byte[] authkey = SnmpUtilities.getLocalizedKeySHA384(passwKey, snmpEngineId);
             computedFingerprint = SnmpUtilities.getFingerPrintSHA384(authkey, message);
         }
         return computedFingerprint;
     }
 
 }