Mass Deface " % self._name_ def __getattr__(self, name): """Get an as-yet undefined attribute value. This calls the get() function that was passed to the constructor. The result is stored as an instance variable so that the next time the same attribute is requested, __getattr__() won't be invoked. If the get() function raises an exception, this is simply passed on -- exceptions are not cached. """ attribute = self._get_(name) self.__dict__[name] = attribute return attribute def Bastion(object, filter = lambda name: name[:1] != '_', name=None, bastionclass=BastionClass): """Create a bastion for an object, using an optional filter. See the Bastion module's documentation for background. Arguments: object - the original object filter - a predicate that decides whether a function name is OK; by default all names are OK that don't start with '_' name - the name of the object; default repr(object) bastionclass - class used to create the bastion; default BastionClass """ raise RuntimeError, "This code is not secure in Python 2.2 and later" # Note: we define *two* ad-hoc functions here, get1 and get2. # Both are intended to be called in the same way: get(name). # It is clear that the real work (getting the attribute # from the object and calling the filter) is done in get1. # Why can't we pass get1 to the bastion? Because the user # would be able to override the filter argument! With get2, # overriding the default argument is no security loophole: # all it does is call it. # Also notice that we can't place the object and filter as # instance variables on the bastion object itself, since # the user has full access to all instance variables! def get1(name, object=object, filter=filter): """Internal function for Bastion(). See source comments.""" if filter(name): attribute = getattr(object, name) if type(attribute) == MethodType: return attribute raise AttributeError, name def get2(name, get1=get1): """Internal function for Bastion(). See source comments.""" return get1(name) if name is None: name = repr(object) return bastionclass(get2, name) def _test(): """Test the Bastion() function.""" class Original: def __init__(self): self.sum = 0 def add(self, n): self._add(n) def _add(self, n): self.sum = self.sum + n def total(self): return self.sum o = Original() b = Bastion(o) testcode = """if 1: b.add(81) b.add(18) print "b.total() =", b.total() try: print "b.sum =", b.sum, except: print "inaccessible" else: print "accessible" try: print "b._add =", b._add, except: print "inaccessible" else: print "accessible" try: print "b._get_.func_defaults =", map(type, b._get_.func_defaults), except: print "inaccessible" else: print "accessible" \n""" exec testcode print '='*20, "Using rexec:", '='*20 import rexec r = rexec.RExec() m = r.add_module('__main__') m.b = b r.r_exec(testcode) if __name__ == '__main__': _test()