Password MIDlet : Security « J2ME « Java

1. Java
2. J2ME
3. Security

Password MIDlet

/*
Wireless Java 2nd edition 
Jonathan Knudsen
Publisher: Apress
ISBN: 1590590775 
*/
import java.io.*;
import java.util.Random;

import javax.microedition.io.*;
import javax.microedition.midlet.*;
import javax.microedition.lcdui.*;

import org.bouncycastle.crypto.Digest;
import org.bouncycastle.crypto.digests.SHA1Digest;

public class PasswordMIDlet extends MIDlet implements CommandListener, Runnable { 
  private Display mDisplay;
  private Form mForm;
  private TextField mUserField, mPasswordField;
  private Random mRandom;
  
  public void startApp() { 
    mDisplay = Display.getDisplay(this);
    mRandom = new Random(System.currentTimeMillis());
    
    if (mForm == null) { 
      mForm = new Form("Login");
      mUserField = new TextField("Name", "jonathan", 32, 0);
      mPasswordField = new TextField("Password", "happy8", 32, 0);
      mForm.append(mUserField);
      mForm.append(mPasswordField);
      
      mForm.addCommand(new Command("Exit", Command.EXIT, 0));
      mForm.addCommand(new Command("Login", Command.SCREEN, 0));
      mForm.setCommandListener(this);
    } 

    mDisplay.setCurrent(mForm);
  } 
  
  public void commandAction(Command c, Displayable s) { 
    if (c.getCommandType() == Command.EXIT) notifyDestroyed();
    else {
      Form waitForm = new Form("Connecting...");
      mDisplay.setCurrent(waitForm);
      Thread t = new Thread(this);
      t.start();
    }
  } 

  public void run() { 
    // Gather the values we'll need.
    long timestamp = System.currentTimeMillis();
    long randomNumber = mRandom.nextLong();
    String user = mUserField.getString();
    byte[] userBytes = user.getBytes();
    byte[] timestampBytes = getBytes(timestamp);
    byte[] randomBytes = getBytes(randomNumber);
    String password = mPasswordField.getString();
    byte[] passwordBytes = password.getBytes();
    
    // Create the message digest.
    Digest digest = new SHA1Digest();
    // Calculate the digest value.
    digest.update(userBytes, 0, userBytes.length);
    digest.update(timestampBytes, 0, timestampBytes.length);
    digest.update(randomBytes, 0, randomBytes.length);
    digest.update(passwordBytes, 0, passwordBytes.length);
    byte[] digestValue = new byte[digest.getDigestSize()];
    digest.doFinal(digestValue, 0);

    // Create the GET URL. The hex encoded message digest value is
    //   included as a parameter.
    URLBuilder ub = new URLBuilder(getAppProperty("PasswordMIDlet-URL"));
    ub.addParameter("user", user);
    ub.addParameter("timestamp",
        new String(HexCodec.bytesToHex(timestampBytes)));
    ub.addParameter("random",
        new String(HexCodec.bytesToHex(randomBytes)));
    ub.addParameter("digest",
        new String(HexCodec.bytesToHex(digestValue)));
    String url = ub.toString();

    try { 
      // Query the server and retrieve the response.
      HttpConnection hc = (HttpConnection)Connector.open(url);
      InputStream in = hc.openInputStream();
      
      int length = (int)hc.getLength();
      byte[] raw = new byte[length];
      in.read(raw);
      String response = new String(raw);
      Alert a = new Alert("Response", response, null, null);
      a.setTimeout(Alert.FOREVER);
      mDisplay.setCurrent(a, mForm);
      in.close();
      hc.close();
    } 
    catch (IOException ioe) { 
      Alert a = new Alert("Exception", ioe.toString(), null, null);
      a.setTimeout(Alert.FOREVER);
      mDisplay.setCurrent(a, mForm);
    } 
  } 
  
  private byte[] getBytes(long x) { 
    byte[] bytes = new byte[8];
    for (int i = 0; i < 8; i++)
      bytes[i] = (byte)(x >> ((7 - i) * 8));
    return bytes;
  } 
  
  public void pauseApp() { } 

  public void destroyApp(boolean unconditional) { } 
} 

class URLBuilder { 
  private StringBuffer mBuffer;
  private boolean mHasParameters;
  
  public URLBuilder(String base) { 
    mBuffer = new StringBuffer(base);
    mHasParameters = false;
  } 
  
  public void addParameter(String name, String value) { 
    // Append a separator.
    if (mHasParameters == false) { 
      mBuffer.append('?');
      mHasParameters = true;
    } 
    else
      mBuffer.append('&');
    // Now tack on the name and value pair. These should
    //   really be URL encoded (see java.net.URLEncoder in
    //   J2SE) but this class appends the name and value
    //   as is, for simplicity. Names or values with spaces
    //   or other special characters will not work correctly.
    mBuffer.append(name);
    mBuffer.append('=');
    mBuffer.append(value);
  } 
  
  public String toString() { 
    return mBuffer.toString();
  } 
} 

class HexCodec { 
  private static final char[] kDigits = { 
    '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
    'a', 'b', 'c', 'd', 'e', 'f'
  } ;
  
  public static char[] bytesToHex(byte[] raw) { 
    int length = raw.length;
    char[] hex = new char[length * 2];
    for (int i = 0; i < length; i++) { 
      int value = (raw[i] + 256) % 256;
      int highIndex = value >> 4;
      int lowIndex = value & 0x0f;
      hex[i * 2 + 0] = kDigits[highIndex];
      hex[i * 2 + 1] = kDigits[lowIndex];
    } 
    return hex;
  } 
  
  public static byte[] hexToBytes(char[] hex) { 
    int length = hex.length / 2;
    byte[] raw = new byte[length];
    for (int i = 0; i < length; i++) { 
      int high = Character.digit(hex[i * 2], 16);
      int low = Character.digit(hex[i * 2 + 1], 16);
      int value = (high << 4) | low;
      if (value > 127) value -= 256;
      raw[i] = (byte)value;
    } 
    return raw;
  } 
  
  public static byte[] hexToBytes(String hex) { 
    return hexToBytes(hex.toCharArray());
  } 
} 



           
       

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