Basic Java Deserialization (ObjectInputStream, readObject)

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इस पोस्ट में java.io.Serializable का उपयोग करते हुए एक उदाहरण समझाया जाएगा।

Serializable

Java Serializable इंटरफेस (java.io.Serializable एक मार्कर इंटरफेस है जिसे आपकी कक्षाओं को लागू करना चाहिए यदि उन्हें सीरियलाइज और डेसिरियलाइज किया जाना है। Java ऑब्जेक्ट सीरियलाइजेशन (लेखन) ObjectOutputStream के साथ किया जाता है और डेसिरियलाइजेशन (पढ़ना) ObjectInputStream के साथ किया जाता है।

आइए एक क्लास Person का उदाहरण देखें जो सीरियलाइजेबल है। यह क्लास readObject फ़ंक्शन को ओवरराइट करती है, इसलिए जब इस क्लास का कोई ऑब्जेक्ट डेसिरियलाइज किया जाता है, तो यह फंक्शन एक्ज़ीक्यूट होगा। उदाहरण में, क्लास Person का readObject फंक्शन उसके पालतू जानवर के eat() फ़ंक्शन को कॉल करता है और कुत्ते का eat() फ़ंक्शन (किसी कारण से) एक calc.exe को कॉल करता है। हम देखेंगे कि इस कैलकुलेटर को चलाने के लिए एक Person ऑब्जेक्ट को कैसे सीरियलाइज और डेसिरियलाइज किया जाए:

निम्नलिखित उदाहरण https://medium.com/@knownsec404team/java-deserialization-tool-gadgetinspector-first-glimpse-74e99e493649 से है

import java.io.Serializable;
import java.io.*;

public class TestDeserialization {
interface Animal {
public void eat();
}
//Class must implements Serializable to be serializable
public static class Cat implements Animal,Serializable {
@Override
public void eat() {
System.out.println("cat eat fish");
}
}
//Class must implements Serializable to be serializable
public static class Dog implements Animal,Serializable {
@Override
public void eat() {
try {
Runtime.getRuntime().exec("calc");
} catch (IOException e) {
e.printStackTrace();
}
System.out.println("dog eat bone");
}
}
//Class must implements Serializable to be serializable
public static class Person implements Serializable {
private Animal pet;
public Person(Animal pet){
this.pet = pet;
}
//readObject implementation, will call the readObject from ObjectInputStream  and then call pet.eat()
private void readObject(java.io.ObjectInputStream stream)
throws IOException, ClassNotFoundException {
pet = (Animal) stream.readObject();
pet.eat();
}
}
public static void GeneratePayload(Object instance, String file)
throws Exception {
//Serialize the constructed payload and write it to the file
File f = new File(file);
ObjectOutputStream out = new ObjectOutputStream(new FileOutputStream(f));
out.writeObject(instance);
out.flush();
out.close();
}
public static void payloadTest(String file) throws Exception {
//Read the written payload and deserialize it
ObjectInputStream in = new ObjectInputStream(new FileInputStream(file));
Object obj = in.readObject();
System.out.println(obj);
in.close();
}
public static void main(String[] args) throws Exception {
// Example to call Person with a Dog
Animal animal = new Dog();
Person person = new Person(animal);
GeneratePayload(person,"test.ser");
payloadTest("test.ser");
// Example to call Person with a Cat
//Animal animal = new Cat();
//Person person = new Person(animal);
//GeneratePayload(person,"test.ser");
//payloadTest("test.ser");
}
}

निष्कर्ष

जैसा कि आप इस बहुत बुनियादी उदाहरण में देख सकते हैं, यहाँ "कमजोरी" इस कारण से प्रकट होती है क्योंकि readObject फ़ंक्शन अन्य कमजोर फ़ंक्शनों को कॉल कर रहा है।

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Serializable

import java.io.Serializable;
import java.io.*;

public class TestDeserialization {
interface Animal {
public void eat();
}
//Class must implements Serializable to be serializable
public static class Cat implements Animal,Serializable {
@Override
public void eat() {
System.out.println("cat eat fish");
}
}
//Class must implements Serializable to be serializable
public static class Dog implements Animal,Serializable {
@Override
public void eat() {
try {
Runtime.getRuntime().exec("calc");
} catch (IOException e) {
e.printStackTrace();
}
System.out.println("dog eat bone");
}
}
//Class must implements Serializable to be serializable
public static class Person implements Serializable {
private Animal pet;
public Person(Animal pet){
this.pet = pet;
}
//readObject implementation, will call the readObject from ObjectInputStream  and then call pet.eat()
private void readObject(java.io.ObjectInputStream stream)
throws IOException, ClassNotFoundException {
pet = (Animal) stream.readObject();
pet.eat();
}
}
public static void GeneratePayload(Object instance, String file)
throws Exception {
//Serialize the constructed payload and write it to the file
File f = new File(file);
ObjectOutputStream out = new ObjectOutputStream(new FileOutputStream(f));
out.writeObject(instance);
out.flush();
out.close();
}
public static void payloadTest(String file) throws Exception {
//Read the written payload and deserialize it
ObjectInputStream in = new ObjectInputStream(new FileInputStream(file));
Object obj = in.readObject();
System.out.println(obj);
in.close();
}
public static void main(String[] args) throws Exception {
// Example to call Person with a Dog
Animal animal = new Dog();
Person person = new Person(animal);
GeneratePayload(person,"test.ser");
payloadTest("test.ser");
// Example to call Person with a Cat
//Animal animal = new Cat();
//Person person = new Person(animal);
//GeneratePayload(person,"test.ser");
//payloadTest("test.ser");
}
}

निष्कर्ष