Android Open Source - CipherChat Message

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License

The source code is released under:
MIT License
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Java Source Code

package com.desperate.common;
//  w w  w .ja  va  2  s . c  o m
import java.io.IOException;
import java.io.ObjectOutputStream;
import java.io.Serializable;
import java.lang.reflect.Field;

import javax.crypto.Mac;
import javax.crypto.spec.SecretKeySpec;

public abstract class Message implements Serializable {

  private static final long serialVersionUID = -7388046942771669624L;

  public Long timestamp;

  public String remoteHMAC;

  /**
   * Gets a string representative of the whole message, to be hashed with {@link #computeHMAC(String)}. The hash will assure the integrity of this
   * info, and nothing else.
   * <p>
   * This should include the timestamp. It's up to the subclass to implement this correctly.
   * 
   * @return String with all info that needs integrity check
   */
  public abstract String getStringToHMAC();

  /**
   * Computes the HMAC of this message, as it is. This is implemented in {@link #Message} and is final: subclasses cannot change it. To set what
   * information should enter the digest, override the {@link #getStringToHMAC()} method.
   * <p>
   * To verify integrity, the resulting HMAC should be checked against the {@link #remoteHMAC} received.
   * 
   * @param secret
   *            Secret to be used in the HMAC
   * @return The HMAC of the message
   */
  public final String computeHMAC(String secret) {

    String type = "HmacSHA256";

    try {
      SecretKeySpec secretKey = new SecretKeySpec(secret.getBytes(Utilities.charset), type);
      Mac mac = Mac.getInstance(type);
      mac.init(secretKey);

      String plainString = getStringToHMAC();

      byte[] bytes = mac.doFinal(plainString.getBytes(Utilities.charset));

      return new String(bytes, Utilities.charset);

    } catch (Exception e) {

      e.printStackTrace();
      throw new RuntimeException(e);
    }
  }

  public boolean verifyTimestamp(Long tolerance) {

    boolean isValid = timestamp > System.currentTimeMillis() - tolerance;

    return isValid;
  }

  /**
   * Sends the message through the specified stream. The stream is assumed to have been connected to a socket.
   * 
   * @param socketStream
   */
  public void send(ObjectOutputStream socketStream) {

    try {
      socketStream.writeObject(this);

      System.out.println(this.toString());
      
      /*
      if (this.remoteHMAC == null)
        System.out.println("Warning: message sent without HMAC.");*/

    } catch (IOException e) {

      System.out.println("Could not send message.");
      e.printStackTrace();
    }
  }

  @Override
  public String toString() {
    StringBuilder result = new StringBuilder();
    String newLine = System.getProperty("line.separator");

    result.append(this.getClass().getSimpleName());
    result.append(" object {");
    result.append(newLine);

    // determine fields declared in this class only (no fields of superclass)
    Field[] fields = this.getClass().getFields();

    // print field names paired with their values
    for (Field field : fields) {

      if (field.getName().contains("key") || field.getName().contains("password") || field.getName().contains("HMAC"))
        continue;

      result.append("  ");
      try {
        result.append(field.getName());
        result.append(": ");
        // requires access to private field:
        result.append(field.get(this));
      } catch (IllegalAccessException ex) {
      }
      result.append(newLine);
    }
    result.append("}\n");

    return result.toString();
  }

}
Java Source Code List
