Need

Secure deserialization process

Context

Description

import java.io.ObjectInputStream;
import java.io.IOException;
import java.io.InputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

    protected void doPost(HttpServletRequest request, HttpServletResponse response) {...

The above code represents a servlet in a Java backend application that reads a serialized object from the HTTP request stream and deserializes it without any validation or type checking. The `doPost` method gets the input stream from the request, wraps it in an `ObjectInputStream` and then reads an object from the stream using the `readObject` method. This is insecure because an attacker can create a malicious payload, serialize it and then send it to the server. The server will then deserialize the object without checking its content or type, leading to potential security vulnerabilities such as remote code execution, privilege escalation, or denial of service attacks. The vulnerability lies in the fact that the application blindly trusts the incoming data and does not perform any validation checks before deserializing the object. This is a classic example of insecure deserialization. The best practice to mitigate this risk is to avoid deserialization of untrusted data. If this is not possible, you should implement strict type constraints during the deserialization process and also apply input validation techniques to ensure the integrity of the data.

import java.io.IOException;
import java.io.InputStream;
import java.io.ObjectInputStream;
import java.io.ObjectStreamClass;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class SecureDeserializationServlet extends HttpServlet {...

The above code fixes the insecure deserialization vulnerability by implementing a whitelist approach to restrict the types of objects that can be deserialized. The `resolveClass` method in `ObjectInputStream` is overridden to check if the class of the object being deserialized is in the whitelist. If it is not, an `InvalidClassException` is thrown, preventing the deserialization of unauthorized classes. The deserialized object is then cast to a specific type before being processed. This ensures that the object is of the expected type and prevents ClassCastException at runtime. Please replace `com.example.Class1` and `com.example.Class2` with the actual classes that you expect to deserialize. This approach significantly reduces the risk of insecure deserialization attacks by ensuring that only authorized and expected classes can be deserialized. However, for a more secure approach, consider using a secure serialization mechanism, such as JSON or XML, instead of Java serialization.

References