Mobile code object hijack

Thank you for visiting OWASP.org. We have migrated our community to a new web platform and regretably the content for this page needed to be programmatically ported from its previous wiki page. There’s still some work to be done.

Description

This attack consists of a technique to create objects without constructors’ methods by taking advantage of the clone() method of Java-based applications.

If a certain class implements cloneable() method declared as public, but doesn’t has a public constructor method nor is declared as final, it is possible to extend it into a new class and create objects using the clone() method.

The clonable() method certifies that the clone() method functions correctly. A cloned object has the same attributes (variables values) of the original object, but the objects are independent.

Risk Factors

TBD

Examples

In this example, a public class “BankAccount” implements the clonable() method which declares “Object clone(string accountnumber)”:

public class BankAccount implements Cloneable{
public Object clone(String accountnumber) throws CloneNotSupportedException {
    Object returnMe = new BankAccount(account number);
        …
    }
}

An attacker can implement a malicious public class that extends the parent BankAccount class, as follows:

public class MaliciousBankAccount extends BankAccount implements Cloneable {
    public Object clone(String accountnumber) throws CloneNotSupportedException {
        Object returnMe = super.clone();
        …
    }
}

A Java applet from a certain application is acquired and subverted by an attacker. Then, they make the victim accept and run a Trojan or malicious code that was prepared to manipulate objects’ state and behavior. This code is instantiated and executed continuously using default JVM on victim’s machine. When the victim invokes the Java applet from the original application using the same JVM, then the attacker clones the class, they manipulate the attributes values, and then substitutes the original object for the malicious one.