hacktricks/pentesting-web/deserialization/basic-java-deserialization-objectinputstream-readobject.md

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U ovom POST-u će biti objašnjen primer korišćenja `java.io.Serializable`.

# Serializable

Java `Serializable` interfejs (`java.io.Serializable` je marker interfejs koji vaše klase moraju implementirati ako treba da budu **serializovane** i **deserializovane**. Java objektna serializacija (pisanje) se vrši pomoću [ObjectOutputStream](http://tutorials.jenkov.com/java-io/objectoutputstream.html), a deserializacija (čitanje) se vrši pomoću [ObjectInputStream](http://tutorials.jenkov.com/java-io/objectinputstream.html).

Hajde da vidimo primer sa **klasom Person** koja je **serializovana**. Ova klasa **prepisuje funkciju readObject**, tako da kada se **bilo koji objekat** ove **klase** **deserializuje**, ova **funkcija** će biti **izvršena**.\
U primeru, **readObject funkcija** klase Person poziva funkciju `eat()` njegovog ljubimca, a funkcija `eat()` psa (iz nekog razloga) poziva **calc.exe**. **Videćemo kako da serializujemo i deserializujemo objekat Person da bismo izvršili ovaj kalkulator:**

**Sledeći primer je sa [https://medium.com/@knownsec404team/java-deserialization-tool-gadgetinspector-first-glimpse-74e99e493649](https://medium.com/@knownsec404team/java-deserialization-tool-gadgetinspector-first-glimpse-74e99e493649)**
```java
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");
}
}
```
## Zaključak

Kao što možete videti u ovom vrlo osnovnom primeru, "ranjivost" ovde se pojavljuje jer **readObject** funkcija **poziva druge ranjive funkcije**.


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