Java

JAVA.CLASS.SER.DNS : Deserializing Non-Serializable Class (Java)

Summary

A non-private, non-interface class C does not implement Serializable, but also does not define method void readObject(java.io.ObjectInputStream).

An attacker can therefore subclass C with a class that implements Serializable and use this as the basis of a deserialization attack.

The checker takes the existence of a readObject() method to indicate that the programmer has accounted for the possibility of deserialization and taken steps to prevent it, for example by throwing an exception whenever readObject() is invoked.

Properties

Class Name Deserializing Non-Serializable Class (Java)
Significance security
Mnemonic JAVA.CLASS.SER.DNS
Categories
CWE CWE:913 Improper Control of Dynamically-Managed Code Resources
OWASP-2017 OWASP-2017:A8 Insecure deserialization
OWASP-2021 OWASP-2021:A8 Software and data integrity failures
Availability Available for Java only.
Enabling Checks for this warning class are disabled by default. To enable them, add the following WARNING_FILTER rule to the project configuration file. 
WARNING_FILTER += allow class="Deserializing Non-Serializable Class (Java)"

Example 

// C.java
import java.io.Serializable;

public class C implements Serializable {    /* Deserializable Class (Java) warning issued here
                                             * C is explicitly serializable. 
                                             */ 
  private static final long serialVersionUID = 6045080196558799656L;
}

// D.java
public class D {}                           /* Deserializing Non-Serializable Class (Java) warning issued here
                                             * D is not explicitly serializable but does not implement a readObject() method. 
                                             */ 

// B.java
import java.io.ObjectInputStream;

public class B {                                                       // ok: not explicitly serializable, and implements readObject() method (which always throws an exception) 
  private void readObject(ObjectInputStream stream) {
        throw new RuntimeException("Deserialization is not allowed");
  }
}

In this example, the programmer should: 

import java.io.Serializable;

public class C {
  private void readObject(ObjectInputStream stream) {
      throw new RuntimeException("Deserialization is not allowed");
  }
}

public class D {
  private void readObject(ObjectInputStream stream) {
      throw new RuntimeException("Deserialization is not allowed");
  }
}

Relevant Configuration File Parameters

The following configuration file parameters affect checks for this warning class.