Listing 4. GSSServer

/****
    GSSServer.java
****/

import org.ietf.jgss.*;
import java.io.*;
import java.net.Socket;
import java.net.ServerSocket;

import java.util.*;
import java.security.*;
import javax.security.auth.callback.*;
import javax.security.auth.login.*;
import javax.security.auth.Subject;
import com.sun.security.auth.callback.TextCallbackHandler;

public class GSSServer implements java.security.PrivilegedAction {

    //Handles callback from the JAAS framework.
    BeanCallbackHandler beanCallbackHandler = null;

    //The main object that handles all JAAS login.
    LoginContext serverLC = null;    

    //The context for secure communication with client.
    GSSContext serverGSSContext = null;
 
    //Socket and streams used for communication.
    ServerSocket serverSocket = null;
    DataInputStream inStream = null; 
    DataOutputStream outStream = null;

    //Name and port of server.
    String serverName = null;
    int serverPort;
	
    //Configuration file and the name of the client configuration.
    String confFile = null;
    String confName = null;

    public static void main(String[] args) throws IOException, GSSException 
    {

        if (args.length < 6) {
            System.err.println("Usage: java <options> 
                                  RemoteServer <server name> <port>
                                  <relam> <kdc> <conf file> <conf name>");
            System.exit(-1);
        }
		
        GSSContext context = null;
        GSSServer server = new GSSServer (args[0]/*serverName*/, 
                                          args[1]/*password*/, 
                                          Integer.parseInt(args[2])/*port*/, 
                                          args[3]/*kerberos realm name*/, 
                                          args[4]/*kdc address*/, 
                                          args[5]/*confFile*/, 
                                          args[6]/*confName*/);

        //Starting the server.
        server.startServer();
      
    }//main


    //GSSServer constructor 
    public GSSServer (String serverName, String password, 
                      int serverPort, String kerberosRealm, 
                      String kdcAddress, String confFile, String confName) 
    {
        beanCallbackHandler = new BeanCallbackHandler(serverName, password);
        this.serverName = serverName;
        this.serverPort = serverPort;
        this.confName = confName;
        System.setProperty("java.security.krb5.realm", kerberosRealm);
        System.setProperty("java.security.krb5.kdc", kdcAddress);
        System.setProperty("java.security.auth.login.config", confFile);

    }//GSSServer
	

    public boolean startServer()
    {			  
        try {
             serverLC = new LoginContext(confName, beanCallbackHandler);
             serverLC.login();
             Subject.doAs(serverLC.getSubject(), this); 
             return true;
        } catch (Exception e) {
             System.out.println(">>> GSSServer... 
                                     Secure Context not established.." );
 	         return false;
        }//catch
	     
    }//start


    public Object run()
    {
        try {
            serverSocket = new ServerSocket(serverPort);
            GSSManager manager = GSSManager.getInstance();
            Oid kerberos = new Oid("1.2.840.113554.1.2.2");

            System.out.println(">>> GSSServer starts.... 
                                    Waiting for incoming connection");

            GSSName serverGSSName = manager.createName(serverName,null);
            GSSCredential serverGSSCreds = manager.createCredential(serverGSSName,
                                           GSSCredential.INDEFINITE_LIFETIME,
	                                     kerberos,
                                           //The server accepts secure context request.
	                                     GSSCredential.ACCEPT_ONLY);

	        serverGSSContext = manager.createContext(serverGSSCreds);

              Socket clientSocket = serverSocket.accept();
	        inStream = new DataInputStream(clientSocket.getInputStream());
	        outStream = new DataOutputStream(clientSocket.getOutputStream());

              byte[] byteToken = null;
    
              while (!serverGSSContext.isEstablished()) 
              {
                  byteToken = new byte[inStream.readInt()];
                  inStream.readFully(byteToken);
                  byteToken = serverGSSContext.acceptSecContext (byteToken, 
                                                                 0, byteToken.length);

                  if (byteToken!= null) 
                  {
                      outStream.writeInt(byteToken.length);
                      outStream.write(byteToken);
                      outStream.flush();
                  }//if
             }//while (!context.isEstablished())
				 
             String clientName =serverGSSContext.getTargName().toString();
             String serverName = serverGSSContext.getSrcName().toString();
             MessageProp msgProp = new MessageProp(0, false);
    
             byteToken = new byte[inStream.readInt()];
             inStream.readFully(byteToken);

             //Unwrapping and verifiying the received message.
             byte[] message = serverGSSContext.unwrap(byteToken, 0,
                                                      byteToken.length, msgProp);

             System.out.println(">>> GSSServer Message 
                                     ["+new String(message)+" ] received");

             //Wrapping the response message.
             message = new String(">>> GSSServer Secure Context establish between
                                      ["+clientName+"] and ["+serverName+"]").getBytes();

             message = serverGSSContext.wrap(message, 0, 
                                             message.length, msgProp);
             outStream.writeInt(message.length);
             outStream.write(message);
             outStream.flush();				 
             System.out.println(">>> GSSServer Message 
                                     ["+new String(message)+"] sent");

             //Disposing and closing client and server sockets.
             serverGSSContext.dispose();
             clientSocket.close();
             serverSocket.close();
             System.out.println(">>> GSSServer shutdown.... ");
         }//try
         catch(java.lang.Exception e){
             e.printStackTrace();
         }

       return null;
	   
    }//run

}//GSSServer