get the trusted lookup using Unsafe.defineAnonymousClass

LookupProxyTest.java

import java.lang.invoke.MethodHandle;
import java.lang.invoke.MethodHandles;
import java.lang.invoke.MethodHandles.Lookup;
import java.lang.invoke.MethodType;
import java.lang.reflect.Field;
import java.util.Base64;

public class LookupProxyTest {
  static final String PROXY_CLASS =
      "yv66vgAAADUAGQoABAAQCQAKABEHABIHABMBAAY8aW5pdD4BAAMoKVYBAARD" +
      "b2RlAQAPTGluZU51bWJlclRhYmxlAQAGbG9va3VwBwAVAQAGTG9va3VwAQAM" +
      "SW5uZXJDbGFzc2VzAQApKClMamF2YS9sYW5nL2ludm9rZS9NZXRob2RIYW5k" + 
      "bGVzJExvb2t1cDsBAApTb3VyY2VGaWxlAQAQTG9va3VwUHJveHkuamF2YQwA" +
      "BQAGDAAWABcBABxqYXZhL2xhbmcvaW52b2tlL0xvb2t1cFByb3h5AQAQamF2" +
      "YS9sYW5nL09iamVjdAcAGAEAJWphdmEvbGFuZy9pbnZva2UvTWV0aG9kSGFu" +
      "ZGxlcyRMb29rdXABAAtJTVBMX0xPT0tVUAEAJ0xqYXZhL2xhbmcvaW52b2tl" +
      "L01ldGhvZEhhbmRsZXMkTG9va3VwOwEAHmphdmEvbGFuZy9pbnZva2UvTWV0" +
      "aG9kSGFuZGxlcwAhAAMABAAAAAAAAgABAAUABgABAAcAAAAdAAEAAQAAAAUq" +
      "twABsQAAAAEACAAAAAYAAQAAAAUACQAJAA0AAQAHAAAAHAABAAAAAAAEsgAC" +
      "sAAAAAEACAAAAAYAAQAAAAcAAgAOAAAAAgAPAAwAAAAKAAEACgAUAAsAGQ==";
  
  public static void main(String[] args) throws Throwable {
    byte[] array = Base64.getDecoder().decode(PROXY_CLASS);
    Field theUnsafe = sun.misc.Unsafe.class.getDeclaredField("theUnsafe");
    theUnsafe.setAccessible(true);
    sun.misc.Unsafe unsafe = (sun.misc.Unsafe)theUnsafe.get(null);
    Class<?> proxy = unsafe.defineAnonymousClass(java.lang.invoke.MethodHandles.class, array, null);
    MethodHandle mh = MethodHandles.lookup().findStatic(proxy, "lookup", MethodType.methodType(Lookup.class));
    Lookup trusted = (Lookup)mh.invokeExact();
    System.out.println(trusted);
  }
}

FWIW: The base64 encoded class resolves to:

package java.lang.invoke;

public class LookupProxy {

    public LookupProxy() {
    }

    public static MethodHandles.Lookup lookup() {
        return MethodHandles.Lookup.IMPL_LOOKUP;
    }
}