Page History

...

The compliant solution correctly implements security manager checks in all constructors, methods that can modify internal state and methods that retrieve internal state. As a result, an attacker cannot create an instance of the object with modified state (using deserialization) and cannot simply read the serialized byte stream to uncover sensitive data (using serialization).

Code Block

bgColor	#ccccff

import java.io.Serializable;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;

public final class SecureCreditCard implements java.io.Serializable {

  //private internal state
  private String credit_card;
  private static final String DEFAULT = "DEFAULT";

  public SecureCreditCard() {
    //initialize credit_card to default value
    credit_card = DEFAULT;
  }

  //allows callers to modify (private) internal state
  public void changeCC(String newCC) {
    if (credit_card.equals(newCC)) {
      // no change
      return;
    } else {
      // check permissions to modify credit_card
      performSecurityManagerCheck();
      validateInput(newCC);
      credit_card = newCC;
    }
  }

  // readObject correctly enforces checks during deserialization
  private void readObject(java.io.ObjectInputStream in) {
    in.defaultReadObject();
    // if the deserialized name does not match the default value normally
    // created at construction time, duplicate the checks
    if (!DEFAULT.equals(credit_card)) {
      performSecurityManagerCheck();
      validateInput(credit_card);
    }
  }

  // allows callers to retrieve internal state
  public String getValue() {
  // check permission to get value
    performSecurityManagerCheck();
    return somePublicValue;
  }

  // writeObject correctly enforces checks during serialization
  private void writeObject(java.io.ObjectOutputStream out) {
    // duplicate check from getValue()
    performSecurityManagerCheck();
    out.writeObject(credit_card);
  }
}

...

Space shortcuts

Page tree

Versions Compared

Old Version 13

New Version 14

Key