package net.sourceforge.jsocks.server;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.PushbackInputStream;
import java.net.Socket;

import net.sourceforge.jsocks.ProxyMessage;
import net.sourceforge.jsocks.UDPEncapsulation;

/**
 An implementation of ServerAuthenticator, which does <b>not</b> do
 any authentication.
<P>
<FONT size="+3" color ="FF0000"> Warning!!</font><br> Should not be
used on machines which are not behind the firewall.
<p>
It is only provided to make implementing other authentication schemes
easier.<br>
For Example: <tt><pre>
   class MyAuth extends socks.server.ServerAuthenticator{
    ...
    public ServerAuthenticator startSession(java.net.Socket s){
      if(!checkHost(s.getInetAddress()) return null;
      return super.startSession(s);
    }

    boolean checkHost(java.net.Inetaddress addr){
      boolean allow;
      //Do it somehow
      return allow;
    }
   }
</pre></tt>
*/
public class ServerAuthenticatorNone implements ServerAuthenticator {

    static final byte[] socks5response = {5, 0};

    InputStream in;
    OutputStream out;

    /**
     Creates new instance of the ServerAuthenticatorNone.
    */
    public ServerAuthenticatorNone() {
        this.in = null;
        this.out = null;
    }
    /**
     Constructs new ServerAuthenticatorNone object suitable for returning
     from the startSession function.
     @param in Input stream to return from getInputStream method.
     @param out Output stream to return from getOutputStream method.
    */
    public ServerAuthenticatorNone(InputStream in, OutputStream out) {
        this.in = in;
        this.out = out;
    }
    /**
     Grants access to everyone.Removes authentication related bytes from
     the stream, when a SOCKS5 connection is being made, selects an
     authentication NONE.
     */
    public ServerAuthenticator startSession(Socket s)
    throws IOException {
        PushbackInputStream in =  new PushbackInputStream(s.getInputStream());
        OutputStream out = s.getOutputStream();
        int version = in.read();

        if (version == 5) {
            if (!selectSocks5Authentication(in, out, 0))
                return null;
        }
        else if (version == 4) {
            //Else it is the request message allready, version 4
            in.unread(version);
        }
        else
            return null;

        return new ServerAuthenticatorNone(in, out);
    }

    /**
      Get input stream.
      @return Input stream speciefied in the constructor.
    */
    public InputStream getInputStream() {
        return in;
    }
    /**
      Get output stream.
      @return Output stream speciefied in the constructor.
    */
    public OutputStream getOutputStream() {
        return out;
    }
    /**
      Allways returns null.
      @return null
    */
    public UDPEncapsulation getUdpEncapsulation() {
        return null;
    }

    /**
     Allways returns true.
    */
    public boolean checkRequest(ProxyMessage msg) {
        return true;
    }

    /**
     Allways returns true.
    */
    public boolean checkRequest(java.net.DatagramPacket dp, boolean out) {
        return true;
    }

    /**
     Does nothing.
     */
    public void endSession() {
    }

    /**
      Convinience routine for selecting SOCKSv5 authentication.
      <p>
      This method reads in authentication methods that client supports,
      checks wether it supports given method. If it does, the notification
      method is written back to client, that this method have been chosen
      for authentication. If given method was not found, authentication
      failure message is send to client ([5,FF]).
      @param in Input stream, version byte should be removed from the stream
                before calling this method.
      @param out Output stream.
      @param methodId Method which should be selected.
      @return true if methodId was found, false otherwise.
    */
    static public boolean selectSocks5Authentication(InputStream in,
            OutputStream out,
            int methodId)
    throws IOException {
        int num_methods = in.read();

        if (num_methods <= 0) return false;

        byte method_ids[] = new byte[num_methods];
        byte response[] = new byte[2];
        boolean found = false;
        response[0] = (byte) 5;    //SOCKS version
        response[1] = (byte) 0xFF; //Not found, we are pessimistic
        int bread = 0; //bytes read so far

        while (bread < num_methods)
            bread += in.read(method_ids, bread, num_methods - bread);

        for (int i = 0; i < num_methods; ++i)
            if (method_ids[i] == methodId) {
                found = true;
                response[1] = (byte) methodId;
                break;
            }

        out.write(response);
        return found;
    }
}