Implement SSL in a Java chat

Question

I am having a tremendous difficulty implementing SSL in a basic java chat. I was able to do the server and the client as well, but when it comes to implementing ssl, it always crashes and I can not continue.

Where should I start to do the implementation next to my code? The code I'm showing here has a very simple graphical interface using swing.

ClientChat

package clientchat;

import javax.swing.JOptionPane;
import static javax.swing.JOptionPane.*;


public class ClientChat {

public static void main(String[] args) {

    String nome = JOptionPane.showInputDialog(null, "Type your name: ", PLAIN_MESSAGE);

    InterfaceChat chat = new InterfaceChat(name);
    chat.setVisible(true);
}

}

Interface Client

package clientchat;

import java.awt.event.KeyEvent;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintStream;
import java.net.*;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.swing.JOptionPane;
import static javax.swing.JOptionPane.ERROR_MESSAGE;

public class InterfaceChat extends javax.swing.JFrame {

private BufferedReader b;
private InputStreamReader i;
private String nome;
private Socket s;

public InterfaceChat(String nome) {
    this.nome = nome;
    try {
        s = new Socket("127.0.0.1", 5000);
    } catch (Exception e) {
        JOptionPane.showMessageDialog(null, "Não se conectou ao servidor",   "", ERROR_MESSAGE);
        System.exit(0);
    }
    initComponents();

    Thread();
}
private void Thread(){
    Thread t = new Thread(new Runnable() {
    String mensagem;    
        @Override
        public void run() {
            try{
                i = new InputStreamReader(s.getInputStream());
                b = new BufferedReader(i);

                while((mensagem = b.readLine())!= null){
                    mensagemRecebida.setText(mensagemRecebida.getText() +  mensagem + "\n");
                }

            }catch(IOException e){
                JOptionPane.showMessageDialog(null, "Erro na conexão com o servidor","",ERROR_MESSAGE);
            }
        }
    });
    t.start();
}

/**
 * This method is called from within the constructor to initialize the form.
 * WARNING: Do NOT modify this code. The content of this method is always
 * regenerated by the Form Editor.
 */
@SuppressWarnings("unchecked")
// <editor-fold defaultstate="collapsed" desc="Generated Code">                          
private void initComponents() {

    jScrollPane1 = new javax.swing.JScrollPane();
    mensagemRecebida = new javax.swing.JTextArea();
    jScrollPane2 = new javax.swing.JScrollPane();
    enviarMensagem = new javax.swing.JTextArea();
    jButton1 = new javax.swing.JButton();
    jButton2 = new javax.swing.JButton();

    setDefaultCloseOperation(javax.swing.WindowConstants.DO_NOTHING_ON_CLOSE);

    mensagemRecebida.setColumns(20);
    mensagemRecebida.setRows(5);
    jScrollPane1.setViewportView(mensagemRecebida);

    enviarMensagem.setColumns(20);
    enviarMensagem.setRows(5);
    enviarMensagem.addKeyListener(new java.awt.event.KeyAdapter() {
        public void keyPressed(java.awt.event.KeyEvent evt) {
            enviarMensagemKeyPressed(evt);
        }
    });
    jScrollPane2.setViewportView(enviarMensagem);

    jButton1.setText("Enviar");
    jButton1.addActionListener(new java.awt.event.ActionListener() {
        public void actionPerformed(java.awt.event.ActionEvent evt) {
            jButton1ActionPerformed(evt);
        }
    });

    jButton2.setText("Sair");
    jButton2.addActionListener(new java.awt.event.ActionListener() {
        public void actionPerformed(java.awt.event.ActionEvent evt) {
            jButton2ActionPerformed(evt);
        }
    });

    javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
    getContentPane().setLayout(layout);
    layout.setHorizontalGroup(
        layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGroup(layout.createSequentialGroup()
            .addContainerGap()
            .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                .addComponent(jScrollPane1)
                .addGroup(layout.createSequentialGroup()
                    .addComponent(jScrollPane2, javax.swing.GroupLayout.PREFERRED_SIZE, 312, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                    .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                        .addComponent(jButton1, javax.swing.GroupLayout.DEFAULT_SIZE, 99, Short.MAX_VALUE)
                        .addComponent(jButton2, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))))
            .addContainerGap())
    );
    layout.setVerticalGroup(
        layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGroup(layout.createSequentialGroup()
            .addContainerGap(javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
            .addComponent(jScrollPane1, javax.swing.GroupLayout.PREFERRED_SIZE, 252, javax.swing.GroupLayout.PREFERRED_SIZE)
            .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
            .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING, false)
                .addGroup(layout.createSequentialGroup()
                    .addComponent(jButton1, javax.swing.GroupLayout.PREFERRED_SIZE, 40, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                    .addComponent(jButton2))
                .addComponent(jScrollPane2, javax.swing.GroupLayout.PREFERRED_SIZE, 0, Short.MAX_VALUE)))
    );

    pack();
}// </editor-fold>                        

private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {                                         

    String mensagem = nome + ": ";

    try {
        PrintStream ps = new PrintStream(s.getOutputStream());
        mensagem += enviarMensagem.getText();

        ps.println(mensagem);
        ps.flush();
        enviarMensagem.setText("");
    } catch (IOException e) {
        JOptionPane.showMessageDialog(null, "Não conseguiu enviar a mensagem", "", ERROR_MESSAGE);
    }
}                                        

private void enviarMensagemKeyPressed(java.awt.event.KeyEvent evt) {                                          
    if (evt.getKeyCode() == KeyEvent.VK_ENTER) {
        String mensagem = nome + ": ";

        try {
            PrintStream ps = new PrintStream(s.getOutputStream());
            mensagem += enviarMensagem.getText();

            ps.println(mensagem);
            ps.flush();
            enviarMensagem.setText("");
        } catch (IOException e) {
            JOptionPane.showMessageDialog(null, "Não conseguiu enviar a mensagem", "", ERROR_MESSAGE);
        }
    }
}                                         

private void jButton2ActionPerformed(java.awt.event.ActionEvent evt) {                                         
    try{
        s.close();
        System.exit(0);
    }
    catch(IOException e){
        e.printStackTrace();
    }
}                                        

// Variables declaration - do not modify                     
private javax.swing.JTextArea enviarMensagem;
private javax.swing.JButton jButton1;
private javax.swing.JButton jButton2;
private javax.swing.JScrollPane jScrollPane1;
private javax.swing.JScrollPane jScrollPane2;
private javax.swing.JTextArea mensagemRecebida;
// End of variables declaration                   
}

Server

import java.io.IOException;
import java.io.PrintStream;
import java.net.*;
import java.util.ArrayList;
import javax.net.ssl.SSLServerSocket;
import javax.net.ssl.SSLServerSocketFactory;
import javax.net.ssl.SSLSocket;

public class ServidorChat {

public static void main(String[] args) {
    ArrayList<PrintStream> clientes = new ArrayList<>(); 
    try{
        SSLServerSocketFactory factory = (SSLServerSocketFactory) SSLServerSocketFactory.getDefault();
        SSLServerSocket server = (SSLServerSocket) factory.createServerSocket(5000);

        while(true){
            SSLSocket sslsocket = (SSLSocket) server.accept();

            //guarda o endereço dos clientes
            clientes.add(new PrintStream(sslsocket.getOutputStream()));
            Mensagem mensagem = new Mensagem(sslsocket, clientes);
        }


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

Message Server

public class Mensagem {

private SSLSocket s;
private ArrayList<PrintStream> clientes;

public Mensagem(SSLSocket s, ArrayList<PrintStream> clientes) {
    this.s = s;
    this.clientes = clientes;
    Thread();
}

private void Thread() {
    Thread t = new Thread(new Runnable() {

        @Override
        public void run() {
            String mensagem = "";
            try {
                InputStreamReader i = new InputStreamReader(s.getInputStream());
                BufferedReader b = new BufferedReader(i);

                while ((mensagem = b.readLine()) != null) {
                    enviarMensagem(mensagem);
                }

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

}

private void enviarMensagem(String mensagem) {
    for (int i = 0; i < clientes.size(); i++) {
        clientes.get(i).println(mensagem);
        clientes.get(i).flush();

Server Error

javax.net.ssl.SSLException: Unrecognized SSL message, plaintext connection?
at sun.security.ssl.InputRecord.handleUnknownRecord(InputRecord.java:710)
at sun.security.ssl.InputRecord.read(InputRecord.java:527)
at sun.security.ssl.SSLSocketImpl.readRecord(SSLSocketImpl.java:973)
at   sun.security.ssl.SSLSocketImpl.performInitialHandshake(SSLSocketImpl.java:1375)
at sun.security.ssl.SSLSocketImpl.readDataRecord(SSLSocketImpl.java:928)
at sun.security.ssl.AppInputStream.read(AppInputStream.java:105)
at sun.nio.cs.StreamDecoder.readBytes(StreamDecoder.java:284)
at sun.nio.cs.StreamDecoder.implRead(StreamDecoder.java:326)
at sun.nio.cs.StreamDecoder.read(StreamDecoder.java:178)
at java.io.InputStreamReader.read(InputStreamReader.java:184)
at java.io.BufferedReader.fill(BufferedReader.java:161)
at java.io.BufferedReader.readLine(BufferedReader.java:324)
at java.io.BufferedReader.readLine(BufferedReader.java:389)
at servidorchat.Mensagem$1.run(Mensagem.java:31)
at java.lang.Thread.run(Thread.java:745)

Answer 1

s = new Socket("127.0.0.1", 5000);

You created a plaintext connection, just as it says in the error message. You need

s = SSLSocketFactory.getInstance().createSocket("127.0.0.1", 5000);

After that everything should work, provided your server certificate is trusted by the client.

Answer 2

You will have to use SSLContext for this purpose. Check out the sample code which I implemented in one of my applications below. Client context means you become the client and call some back end. Server context means you accept the client requests.

public class SSLUtil {
    private static String KEY_STORE_TYPE = "JKS";
    private static String TRUST_STORE_TYPE = "JKS";
    private static String KEY_MANAGER_TYPE = "SunX509";
    private static String TRUST_MANAGER_TYPE = "SunX509";
    private static String PROTOCOL = "TLS";

    private static SSLContext serverSSLCtx = null;
    private static SSLContext clientSSLCtx = null;

    public static SSLContext createServerSSLContext(final String keyStoreLocation,
                                                    final String keyStorePwd)
                                                                             throws KeyStoreException,
                                                                             NoSuchAlgorithmException,
                                                                             CertificateException,
                                                                             FileNotFoundException,
                                                                             IOException,
                                                                             UnrecoverableKeyException,
                                                                             KeyManagementException {
        if (serverSSLCtx == null) {
            KeyStore keyStore = KeyStore.getInstance(KEY_STORE_TYPE);
            keyStore.load(new FileInputStream(keyStoreLocation), keyStorePwd.toCharArray());
            KeyManagerFactory keyManagerFactory = KeyManagerFactory.getInstance(KEY_MANAGER_TYPE);
            keyManagerFactory.init(keyStore, keyStorePwd.toCharArray());
            serverSSLCtx = SSLContext.getInstance(PROTOCOL);
            serverSSLCtx.init(keyManagerFactory.getKeyManagers(), null, null);
        }

        return serverSSLCtx;
    }

    public static SSLContext createClientSSLContext(final String trustStoreLocation,
                                                    final String trustStorePwd)
                                                                               throws KeyStoreException,
                                                                               NoSuchAlgorithmException,
                                                                               CertificateException,
                                                                               FileNotFoundException,
                                                                               IOException,
                                                                               KeyManagementException {
        if (clientSSLCtx == null) {
            KeyStore trustStore = KeyStore.getInstance(TRUST_STORE_TYPE);
            trustStore.load(new FileInputStream(trustStoreLocation), trustStorePwd.toCharArray());
            TrustManagerFactory trustManagerFactory =
                                                      TrustManagerFactory.getInstance(TRUST_MANAGER_TYPE);
            trustManagerFactory.init(trustStore);
            clientSSLCtx = SSLContext.getInstance(PROTOCOL);
            clientSSLCtx.init(null, trustManagerFactory.getTrustManagers(), null);
        }

        return clientSSLCtx;

    }

}

Hope this helps. Happy coding !