I can't use malicous reflection to view values of private fields

Question

I can get the value of the protected field, but the private field throws java.lang.IllegalAccessException. I think I know why I'm getting this exception, but how is reflection used to exploit the contents of private fields, how do I get around this?

Programmer Hat is on
I have created the following Vulnerable class in a netbeans project. I have made a Jar file to distribute it.

public class Vulnerable {
    private int privateSecret;
    protected int protectedSecret;
    int secret;

    public Vulnerable() {
    this.protectedSecret = 11;
    this.privateSecret = 22;
    this.secret = 33;
    }
}

Malicious Hacker Hat is now on
I want to know private hidden fields and I want to know what they contain.
I have the Jar file and I have imported it into my Exploit project.

The following class extends Vulnerable and uses reflection to list fields and try to access the values.

public class ExpliotSubClass extends VulnerableCode.Vulnerable {

    public List<Field> protectedList = new LinkedList<Field>();
    public List<Field> privateList = new LinkedList<Field>();

    public void lists() {
        Field[] declaredFields = this.getClass().getSuperclass().getDeclaredFields();

        for (Field field : declaredFields) {
            int modifiers = field.getModifiers();
            if (Modifier.isPrivate(modifiers)) {
                privateList.add(field);
                System.out.println("Private = " + field.getName());
            } else if (Modifier.isProtected(modifiers)) {
                protectedList.add(field);
                System.out.println("Protected= " + field.getName());
            }
        }
    }


    public Object get(Field field) {
        try {
            return field.get(this);
        } catch (IllegalArgumentException ex) {
            Logger.getLogger(ExpliotSubClass.class.getName()).log(Level.SEVERE,
                                                                  null,
                                                                  ex);
        } catch (IllegalAccessException ex) {
            Logger.getLogger(ExpliotSubClass.class.getName()).log(Level.SEVERE,
                                                                  null,
                                                                  ex);
        }
        return null;
    }
}

Answer 1

In order to access private field you have to set it as accessible:

field.setAccessible(true);

Answer 2

in this lists() method, you should add the following code, before adding the field object to the privateList.

-field.setAccessible(true);

That is the code for the lists method will become

public void lists() { Field[] declaredFields = this.getClass().getSuperclass().getDeclaredFields();

    for (Field field : declaredFields) {
        int modifiers = field.getModifiers();
        if (Modifier.isPrivate(modifiers)) {
            field.setAccessible(true);//Add this
            privateList.add(field);
            System.out.println("Private = " + field.getName());
        } else if (Modifier.isProtected(modifiers)) {
            protectedList.add(field);
            System.out.println("Protected= " + field.getName());
        }
    }
}

Now run your code. It will work.

Answer 3

If you have the .jar can you just decompile it and then parse the .java file to get the info you need?