// VECR IO client
//
// spawned by the IO server to handle one client

import java.net.*;
import java.io.*;
import java.util.*;
import javax.crypto.*;
import javax.crypto.spec.*;

public class IOclient extends Thread
{
 // IO protocol
 //
  static final byte DATA   = 0;
  static final byte EOF    = 1;
  static final byte STOP   = 2;
  static final byte SAVE   = 3;

 // network I/O
 //
  private Socket s;
  private DataInputStream in;
  private BufferedOutputStream out;
  private String name;

 // process I/O
 //
  private Process p;
  private ProcessBuilder pb;
  private BufferedInputStream pin;
  private BufferedOutputStream pout;
  private IOcopy copy;

  /* hex conversion code adapted from cryptix.util.core.Hex */

  private static final char[] hexDigits = {
    '0','1','2','3','4','5','6','7','8','9','a','b','c','d','e','f'
  };

  // convert byte array to hex
  //
  public static String hex(byte[] ba)
  {
    char[] buf = new char[ba.length * 2];
    int j = 0;
    int k;

    for (int i = 0; i < ba.length; i++) {
      k = ba[i];
      buf[j++] = hexDigits[(k >>> 4) & 0x0F];
      buf[j++] = hexDigits[ k        & 0x0F];
    }

    return new String(buf);
  }

  public IOclient( Socket s, String name) throws IOException
  {
    this.s = s;
    this.name = name;
    in = new DataInputStream( new BufferedInputStream( s.getInputStream()));
    out = new BufferedOutputStream( s.getOutputStream());
  }

 // save applet output window to "output.txt"
 //
  public void save( String data, String uid, String dir)
  {
    try
    {
     // prepare arguments for subprocess
     //
      ArrayList<String> argv = new ArrayList<String>(10);
      argv.add( "/vecr/IO/bin/save");
      argv.add( "--setuidgid");
      argv.add( uid);
      argv.add( uid);
      argv.add( "--chdir");
      argv.add( dir);

     // create save subprocess
     //
      ProcessBuilder pb = new ProcessBuilder( argv);
      pb.redirectErrorStream( true);
      Process p = pb.start();
      BufferedOutputStream pout = new BufferedOutputStream( p.getOutputStream());
      pout.write( data.getBytes());
      pout.close();
    }
    catch(Exception e)
    {
      synchronized( System.out)
      {
        e.printStackTrace( System.out);
	System.out.flush();
      }
    }
  }

  public void run()
  {
    String line;
    byte b;

    try {

     // read parameters sent by the applet
     //
      String user = in.readUTF();
      String uid = in.readUTF();
      String time = in.readUTF();
      String ticket = in.readUTF();
      String dir = in.readUTF();
      String prog = in.readUTF();
      String args = in.readUTF();

     // read secret data
     //
      FileInputStream fin = new FileInputStream( "/vecr/IO/bin/secret.dat");
      byte secret[] = new byte[64];
      int n = fin.read( secret);
      fin.close();

      if( n < 64)
	throw new SecurityException( "secret.dat is too small");

     // construct authentication data
     //
      SecretKeySpec KS = new SecretKeySpec( secret, "HmacSHA256");
      Mac mac = Mac.getInstance( "HmacSHA256");
      mac.init( KS);

      mac.update( time.getBytes());
      mac.update( user.getBytes());
      mac.update( uid.getBytes());
      String auth = hex( mac.doFinal());

      if( auth.compareTo( ticket) != 0) // client authentication ticket is invalid
      {
	out.write( "Authentication failed\n".getBytes());
	out.flush();
	throw new SecurityException(
	  "Authentication failed for user " + user + " from " + name);
      }

      synchronized( System.out)
      {
        System.out.println(
	  "Authentication succeeded for user " + user + " from " + name);
	System.out.flush();
      }

     // check authentication ticket time limit
     //
      long mytime = System.currentTimeMillis();
      long yourtime = Long.parseLong( time);

      if( mytime - yourtime > 1800000) // 30 minute limit
      {
	out.write( "Authentication data is too old\n".getBytes());
	out.flush();
	throw new SecurityException(
	  "Stale authentication data for user " + user + " from " + name);
      }

     // prepare arguments for subprocess
     //
      ArrayList<String> argv = new ArrayList<String>(25);
      argv.add( "/vecr/IO/bin/run");
      argv.add( "--setuidgid");
      argv.add( uid);
      argv.add( uid);
      argv.add( "--chdir");
      argv.add( dir);
      argv.add( prog);

      String[] user_argv = args.split( "\\s+");
      for( int j = 0; j < user_argv.length; ++j)
	argv.add( user_argv[j]);

      String msg = "Running in " + dir + ": " + prog + " " + args + "\n";
      out.write( msg.getBytes());
      out.flush();

     // create run subprocess
     //
      pb = new ProcessBuilder( argv);
      pb.redirectErrorStream( true);
      p = pb.start();
      pin = new BufferedInputStream( p.getInputStream());    // reads from subprocess stdout
      pout = new BufferedOutputStream( p.getOutputStream()); // writes to subprocess stdin

     // create IO copy thread
     //
      copy = new IOcopy( pin, out);
      copy.start();

     // loop until applet sends STOP
     //
      do
      {
	b = in.readByte();

	switch( b)
	{
	  case DATA:
	    line = in.readUTF();
	    if( pout != null)
	    {
	      pout.write( line.getBytes());
	      pout.write( '\n');
	      pout.flush();
	    }
	    break;

	  case EOF:
	    if( pout != null)
	    {
	      pout.close();
	      pout = null;
	    }
	    break;

	  case STOP:
	    out.write( "\nStop.\n".getBytes());
	    out.flush();
	    p.destroy();
	    p = null;
	    break;

	  case SAVE:
	    save( in.readUTF(), uid, dir);
	    out.write( "\nSaved.\n".getBytes());
	    out.flush();
	    break;

	  default:	// shouldn't happen
	    b = STOP;
	    break;
	}

      } while( b != STOP);

    }
    catch(Exception e)
    {
      synchronized( System.out)
      {
        e.printStackTrace( System.out);
	System.out.flush();
      }
    }
    finally
    {
      Date now = new Date();
      synchronized( System.out)
      {
        System.out.println( now + ": disconnect " + name);
	System.out.flush();
        try
        {
	  if( copy != null) copy.interrupt();
	  if( pin != null) pin.close();
	  if( pout != null) pout.close();
	  if( p != null) p.destroy();
	  in.close();
	  out.close();
          s.close();
        }
        catch( Exception e)
        {
          e.printStackTrace( System.out);
	  System.out.flush();
        }
      }
    }

  }

}