Tags: jar rev java
Rating:
You reach a large metal door. It's protected by large yellow bars. There appears to be an panel with a keypad...
[Bunker.jar](https://github.com/Nightxade/ctf-writeups/blob/master/assets/CTFs/Cyber-Cooperative-CTF-2023/rev/Bunker.jar)
---
We're given a .jar file to reverse. [JADX](https://github.com/skylot/jadx) is a great tool for doing exactly that. I'm personally using the GUI version of JADX.
This is the only Java file in the JADX decompilation:
```java
package defpackage;
import java.awt.Component;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JTextField;
import javax.swing.UIManager;
/* compiled from: bunker.java */
/* renamed from: Bunker reason: default package */
/* loaded from: Bunker.jar:Bunker.class */
class Bunker extends JFrame implements ActionListener {
static JFrame f;
static JTextField l;
String output = "";
Bunker() {
}
public static void main(String[] strArr) {
f = new JFrame("Bunker");
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (Exception e) {
System.err.println(e.getMessage());
}
Bunker bunker = new Bunker();
l = new JTextField(8);
l.setEditable(false);
JButton jButton = new JButton("0");
JButton jButton2 = new JButton("1");
JButton jButton3 = new JButton("2");
JButton jButton4 = new JButton("3");
JButton jButton5 = new JButton("4");
JButton jButton6 = new JButton("5");
JButton jButton7 = new JButton("6");
JButton jButton8 = new JButton("7");
JButton jButton9 = new JButton("8");
JButton jButton10 = new JButton("9");
JPanel jPanel = new JPanel();
jButton.addActionListener(bunker);
jButton2.addActionListener(bunker);
jButton3.addActionListener(bunker);
jButton4.addActionListener(bunker);
jButton5.addActionListener(bunker);
jButton6.addActionListener(bunker);
jButton7.addActionListener(bunker);
jButton8.addActionListener(bunker);
jButton9.addActionListener(bunker);
jButton10.addActionListener(bunker);
jPanel.add(l);
jPanel.add(jButton);
jPanel.add(jButton2);
jPanel.add(jButton3);
jPanel.add(jButton4);
jPanel.add(jButton5);
jPanel.add(jButton6);
jPanel.add(jButton7);
jPanel.add(jButton8);
jPanel.add(jButton9);
jPanel.add(jButton10);
f.add(jPanel);
f.setSize(120, 500);
f.show();
}
public void actionPerformed(ActionEvent actionEvent) {
this.output += actionEvent.getActionCommand();
l.setText(this.output);
if (this.output.length() == 8) {
System.err.print("USER ENTERED: ");
System.err.println(this.output);
l.setText("");
if (this.output.equals("72945810")) {
StringBuilder sb = new StringBuilder();
for (int i = 0; i < "Q^XSNZD^\\WKk\u0004\tnCVKJkTOPYCm_AGLYUEmPZFLCETFP[[E".length(); i++) {
sb.append((char) ("Q^XSNZD^\\WKk\u0004\tnCVKJkTOPYCm_AGLYUEmPZFLCETFP[[E".charAt(i) ^ this.output.charAt(i % this.output.length())));
}
JOptionPane.showMessageDialog((Component) null, sb.toString());
} else {
JOptionPane.showMessageDialog((Component) null, "=== BUNKER CODE INVALID ===");
}
this.output = "";
}
}
}
```
Seems like the code is just `72945810`.
Run the program with `java -jar Bunker.jar` and input the code into the numeric keypad to get the flag!
flag{bunker_11_says_await_further_instruction}
