Android Open Source - CipherChat Phone Server Socket Handler

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Back to project page CipherChat.

License

The source code is released under:

MIT License

Java Source Code

package com.ist.cipherchat.networking;
// w w w  .ja va  2  s . co m
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.net.ServerSocket;
import java.net.Socket;
import java.security.SecureRandom;

import javax.crypto.spec.SecretKeySpec;

import android.app.Activity;
import android.content.Context;
import android.content.Intent;
import android.util.Log;

import com.desperate.common.NoncePacket;
import com.desperate.common.Utilities;
import com.desperate.common.messages.StartChatMessage;
import com.desperate.common.replies.CheckSessionMessage;
import com.desperate.common.replies.NeedhamSchroederSuccessReply;
import com.desperate.common.replies.ReplyMessage;
import com.desperate.common.replies.StartChatReply;
import com.ist.cipherchat.gui.ChatActivity;
import com.ist.cipherchat.gui.Contacts;
import com.ist.cipherchat.gui.Origin;

public class PhoneServerSocketHandler implements Runnable {

  public static String EXTRA_ENUM = "com.ist.cryptochat.EXTRA_ENUM";
  public static int PHONE_SERVER_TO_CHAT = 555;

  public static ServerSocket serverSocket;
  static Socket clientSocket;

  public ObjectInputStream in;
  private ObjectOutputStream out;

  private Context context;
  private Activity callerActivity;

  private String otherUsername;

  private SecureRandom rand = new SecureRandom();
  private Long nonce;
  private SecretKeySpec sessionKey;

  public PhoneServerSocketHandler(Context context, Activity callerActivity) {
    this.context = context;
    this.callerActivity = callerActivity;

    try {
      PhoneServerSocketHandler.serverSocket = new ServerSocket(OutputSocketHandler.PORT);
    } catch (IOException e) {
      // TODO Auto-generated catch block
      e.printStackTrace();
    }
  }

  @Override
  public void run() {
    // TODO Auto-generated method stub
    Log.d("register", "Listening on port" + OutputSocketHandler.PORT);

    if (serverSocket.isBound()) {
      Log.d("register", "bound on " + OutputSocketHandler.PORT);
    }

    try {
      PhoneServerSocketHandler.clientSocket = serverSocket.accept();
    } catch (IOException e) {
      // TODO Auto-generated catch block
      e.printStackTrace();
    }

    Globals.setServerSocket(clientSocket);
    Log.d("register", "accepted on port" + OutputSocketHandler.PORT + clientSocket.getInetAddress().toString());

    try {

      out = new ObjectOutputStream(PhoneServerSocketHandler.clientSocket.getOutputStream());

      in = new ObjectInputStream(PhoneServerSocketHandler.clientSocket.getInputStream());

      startChatMessage();

      recieveSessionKey();

      callActivity();

    } catch (Exception e) {
      e.printStackTrace();
    }

    Log.d("register", "User B finished NS.");

    // Keep in and out for future chat
    Globals.setOis(in);
    Globals.setOos(out);
    
    // ChatInRunnable chatIn = new ChatInRunnable(in, otherUsername, sessionKey);
    ChatInRunnable chatIn = new ChatInRunnable();

    Thread t = new Thread(chatIn);
    t.start();

  }

  /**
   * Messages 5, 6 and 7, and nonce verification (8)
   */
  private void recieveSessionKey() {

    NoncePacket noncePacket;

    // Message 6, has Rc
    CheckSessionMessage message = new CheckSessionMessage();

    // check message 5
    try {
      StartChatReply reply = (StartChatReply) in.readObject();

      noncePacket = (NoncePacket) Utilities.decipherObject(reply.cipheredNoncePacket, Contacts.sslSocketHandler.getKek());

      if (!reply.verifyTimestamp(Utilities.tolerance)) {
        sendErrorMessage(message, "Wrong time-stamp on NS (step 5)", Utilities.keyToString(noncePacket.sessionKey));
        return;
      }

      if (!reply.remoteHMAC.equals(reply.computeHMAC(Utilities.keyToString(noncePacket.sessionKey)))) {
        sendErrorMessage(message, "Wrong HMAC on NS (step 5)", Utilities.keyToString(noncePacket.sessionKey));
        return;
      }

      // Check Rb
      if (!noncePacket.bNonce.equals(nonce) || !noncePacket.requesterUserName.equals(this.otherUsername)) {
        message.accepted = false;

      } else {
        message.accepted = true;

        Globals.setOtherUsername(otherUsername);

        this.sessionKey = noncePacket.sessionKey;
        Globals.setSessionKey(sessionKey);

        // Generate a second nonce, to guarantee A knows the sessionKey
        nonce = rand.nextLong();
        message.setNonce(nonce, sessionKey);
      }

      message.timestamp = System.currentTimeMillis();

      message.remoteHMAC = message.computeHMAC(Utilities.keyToString(sessionKey));

      message.send(out);

      // Receive nonce, decremented
      CheckSessionMessage decrementedNonce = (CheckSessionMessage) in.readObject();
      NeedhamSchroederSuccessReply finalMessage = new NeedhamSchroederSuccessReply();

      // Check HMAC
      if (!decrementedNonce.remoteHMAC.equals(decrementedNonce.computeHMAC(Utilities.keyToString(sessionKey)))) {
        sendErrorMessage(message, "Wrong HMAC on NS (step 7)", Utilities.keyToString(noncePacket.sessionKey));
        return;
      }

      // Check timestamp
      if (!decrementedNonce.verifyTimestamp(Utilities.tolerance)) {
        sendErrorMessage(message, "Wrong TS on NS (step 7)", Utilities.keyToString(noncePacket.sessionKey));
        return;
      }

      Long decNonce = (Long) Utilities.decipherObject(decrementedNonce.bobNonce, sessionKey);
      if (!decNonce.equals(nonce - 1)) {
        sendErrorMessage(message, "Wrong nonce on NS (step 7)", Utilities.keyToString(noncePacket.sessionKey));
        return;
      }

      finalMessage.accepted = true;
      finalMessage.timestamp = System.currentTimeMillis();
      finalMessage.remoteHMAC = finalMessage.computeHMAC(Utilities.keyToString(sessionKey));

      // NS concluded, send message 8
      finalMessage.send(out);


    } catch (Exception e) {
      e.printStackTrace();
    }
  }

  private void startChatMessage() {

    byte[] cipheredNoncePacket;

    try {
      StartChatMessage chatMessage = (StartChatMessage) in.readObject();

      this.otherUsername = chatMessage.requesterUserName;

      nonce = rand.nextLong();

      NoncePacket packet = new NoncePacket(otherUsername, nonce);

      packet.sessionKey = null;

      cipheredNoncePacket = Utilities.cipherObject(packet, Contacts.sslSocketHandler.getKek());

      StartChatReply reply = new StartChatReply(cipheredNoncePacket);

      reply.send(out);

    } catch (Exception e) {
      e.printStackTrace();
    }

  }

  public SecretKeySpec getSessionKey() {
    return sessionKey;
  }

  public String getStrSessionKey() {
    return new String(sessionKey.getEncoded());
  }

  private void callActivity() {
    Intent chatIntent = new Intent(context, ChatActivity.class);

    Origin origin = Origin.PHONESERVERSOCKET;

    chatIntent.putExtra("EXTRA_ENUM", origin.toString());

    chatIntent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);

    callerActivity.startActivityForResult(chatIntent, PHONE_SERVER_TO_CHAT);
  }

  private void sendErrorMessage(ReplyMessage message, String error, String hmacKey) {
    message.accepted = false;
    message.errorMessage = error;
    message.timestamp = System.currentTimeMillis();
    message.remoteHMAC = message.computeHMAC(hmacKey);
    message.send(out);
  }

  public ObjectOutputStream getObjectOutputStream() {
    return out;
  }
}

Java Source Code List

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