This site is the archived OWASP Foundation Wiki and is no longer accepting Account Requests.
To view the new OWASP Foundation website, please visit https://owasp.org
Mobile code: non-final public field
- This is an Attack. To view all attacks, please see the Attack Category page.
ASDR Table of Contents
Description
This attack aims to manipulate non-final public variables used in mobile code by injecting malicious values on it, mostly in Java and C++ applications.
When a public member variable or class used in mobile code isn’t declared as final, its values can be maliciously manipulated by any function that has access to it in order to extend the application code or acquire critical information about the application.
Risk Factors
TBD
Examples
A Java applet from a certain application is acquired and subverted by an attacker. Then, he makes the victim accept and run a Trojan or malicious code that was prepared to manipulate non-final objects’ state and behavior. This code is instantiated and executed continuously using default JVM on the victim’s machine. When the victim invokes the Java applet from the original application using the same JVM, the malicious process could be mixed with original applet, thus it modifies values of non-final objects and executes under victim’s credentials.
In the following example, the class “any_class” is declared as final and “server_addr” variable is not:
public final class any_class extends class_Applet {
public URL server_addr;
…
}
In this case, the value of “server_addr” variable could be set by any other function that has access to it, thus changing the application behavior. A proper way to declare this variable is:
public class any_class extends class_Applet {
public final URL server_addr;
…
}
When a variable is declared as final its value cannot be modified.
External References
http://cwe.mitre.org/data/definitions/493.html – Mobile Code: non-final public field http://www.fortifysoftware.com/vulncat/ - Unsafe Mobile Code: Access Violation http://www.fortifysoftware.com/vulncat/ - Unsafe Mobile Code: Public finalize() Method
