reflection - Is there a way for a SecurityManager in java to selectively grant ReflectPermission("suppressAccessChecks")?

Question

Is there any way for a SecurityManager in Java to selectively grant ReflectPermission("suppressAccessChecks") depending on the details of what setAccessible() is being called on? I don't see any way for this to be done.

For some sandboxed code, it would be very useful (such as for running various dynamic JVM languages) to allow the setAccessible() reflection API to be called, but only when setAccessible() is called on a method/field of a class that originates in the sandboxed code.

Does anyone have any alternative suggestions other than selective granting of ReflectPermission("suppressAccessChecks") if this isn't possible? Perhaps it would be safe to grant in all cases if SecurityManager.checkMemberAccess() is sufficiently restrictive?

Answer 1

Maybe looking at the call stack would be enough for your purposes? Something like:

import java.lang.reflect.ReflectPermission;
import java.security.Permission;

public class Test {
    private static int foo;

    public static void main(String[] args) throws Exception {
        System.setSecurityManager(new SecurityManager() {
            @Override
            public void checkPermission(Permission perm) {
                if (perm instanceof ReflectPermission && "suppressAccessChecks".equals(perm.getName())) {
                    for (StackTraceElement elem : Thread.currentThread().getStackTrace()) {
                        if ("Test".equals(elem.getClassName()) && "badSetAccessible".equals(elem.getMethodName())) {
                            throw new SecurityException();
                        }
                    }
                }
            }
        });

        goodSetAccessible(); // works
        badSetAccessible(); // throws SecurityException
    }

    private static void goodSetAccessible() throws Exception {
        Test.class.getDeclaredField("foo").setAccessible(true);
    }

    private static void badSetAccessible() throws Exception {
        Test.class.getDeclaredField("foo").setAccessible(true);
    }
}