/* OVOAP Trusted Authentication Server - Multithreaded version */

import java.io.*;
import java.net.*;

public class ovoapMT
{

    static final int BSIZE = 512;
    static final int NSIZE = 64;
    static final short TASPORT = 21004;

    static void genkey(byte[] Key) // generates random key
    {
	for(int i=Key.length-1;i>=0;i--)
	    Key[i] = (byte)((int)(Math.random()*256));
    }

    // read until buffer is full:
    static void readFully(DataInputStream din, byte[] buf) throws Exception
    {
	int len = buf.length;
	int br; // byte read;
	int total = 0;
	while (total<len)
	    {
		br = din.read(buf,total,(len-total));
		total += br;
	    }
    }


public static void main(String[] args) throws Exception
 {
     ServerSocket sfd;
     Socket cfd;
     sfd = new ServerSocket(TASPORT);
     sfd.setReuseAddress(true);
     System.out.println("OVOAP Authentication Server Started ...");

     while (true)
     {
      cfd = sfd.accept();
      cfd.setSoTimeout(20000);
      System.out.println("**ovoap TAS connection from "+cfd.getInetAddress());
      Thread CT = new Thread(new clientthread(cfd));
      CT.start();
     } // main loop
 } // main

} // ovapMT


class clientthread implements Runnable
{ 
    static final int BSIZE = 512;
    static final int NSIZE = 64;
    static final short TASPORT = 20004;

     Socket cfd;
     DataInputStream din, fink, finp;
     DataOutputStream dout;
     byte[] keyS = new byte[BSIZE];  // session key
     byte[] keyA = new byte[BSIZE];
     byte[] keyB = new byte[BSIZE];
     byte[] sbuf = new byte[BSIZE];
     int[] pA = new int[BSIZE];
     int[] pB = new int[BSIZE];
     byte[] name = new byte[NSIZE*2];
     byte[] stamp = new byte[BSIZE];

    public clientthread(Socket c) {cfd=c;}

    public void run()
    {
	try { serve(); }
	catch (Exception e) {}
    }

    public void serve() throws Exception
    {
      int i, j;
      try {
 	  
 	    din = new DataInputStream(cfd.getInputStream());
	    dout = new DataOutputStream(cfd.getOutputStream());
	    // get names of A and B
	    j = din.read(name,0,NSIZE*2);
	    if (j!=NSIZE*2) throw new Exception("invalid data");
	    String A = myutils.bufToString(name,0,64);
	    String B = myutils.bufToString(name,64,64);
	    if (A.equals(B)) throw new Exception("can't spoof yourself");
	    System.out.println("TAS: client "+A+" wants to connect to server "+B);

            ovoapMT.genkey(keyS); // generate session key
	    ovoapMT.genkey(stamp); // generate session stamp

	    // load permutation and key files:
	    fink = new DataInputStream(new FileInputStream(A+".xkey"));
	    j = fink.read(keyA,0,BSIZE);
	    fink.close();
	    finp = new DataInputStream(new FileInputStream(A+".perm"));
	    for(i=0;i<BSIZE;i++) pA[i]=finp.readInt();
	    finp.close();
	    fink = new DataInputStream(new FileInputStream(B+".xkey"));
	    j = fink.read(keyB,0,BSIZE);
	    fink.close();
	    finp = new DataInputStream(new FileInputStream(B+".perm"));
	    for(i=0;i<BSIZE;i++) pB[i]=finp.readInt();
	    finp.close();
	    
	    // send permA(keyA(keyS))
	    for(i=0;i<BSIZE;i++)
		sbuf[pA[i]] = (byte)((byte)keyS[i]^(byte)keyA[i]);
	    dout.write(sbuf,0,BSIZE);
	    // send permA(keyA(stamp))
	    for(i=0;i<BSIZE;i++)
		sbuf[pA[i]] = (byte)((byte)stamp[i]^(byte)keyA[i]);
	    dout.write(sbuf,0,BSIZE);

	    for(i=0;i<BSIZE;i++)
		sbuf[pB[i]] = (byte)((byte)keyS[i]^(byte)keyB[i]);
	    dout.write(sbuf,0,BSIZE);
	    for(i=0;i<BSIZE;i++)
		sbuf[pB[i]] = (byte)((byte)stamp[i]^(byte)keyB[i]);
	    dout.write(sbuf,0,BSIZE);
	    // send permB(keyB(stamp))
	    
	    dout.flush();  // make sure everything written
	    
	    din.close();
	    dout.close();
	    cfd.close();
	    System.out.println("ovoap TAS: closing connection to "+A);

	  } 
	  catch (Exception e) { System.out.println(e); }
    } // run
} // clientthread