Talin wrote:
> Scott Dial wrote:
>> Phillip J. Eby wrote:
>>
>>> A function's func_closure contains cell objects that hold the
>>> variables. These are readable if you can set the func_closure of some
>>> function of your own. If the overall plan includes the ability to restrict
>>> func_closure setting (or reading) in a restricted interpreter, then you
>>> might be okay.
>>
>> Except this function (__getattribute__) has been trapped inside of a
>> class which does not expose it as an attribute. So, you shouldn't be
>> able to get to the func_closure attribute of the __getattribute__
>> function for an instance of the Guard class. I can't come up with a way
>> to defeat this protection, at least. If you have a way, then I'd be
>> interested to hear it.
>
> I've thought of several ways to break it already. Some are repairable,
> I'm not sure that they all are.
>
> For example, neither of the following statements blows up:
>
> print t2.get_name.func_closure[0]
> print object.__getattribute__( t2, '__dict__' )
>
> Still, its perhaps a useful basis for experimentation.
>
> -- Talin
I quickly poked around it in python and realized that in 2.5 (as opposed
to the 2.4 python I was playing in) the cell object exposes
cell_contents.. blargh. So, yes, you can defeat the protection because
the wrapped instance is exposed.
print t2.get_name()
t2.get_name.func_closure[0].cell_contents.im_self.name = 'poop'
print t2.get_name()
Although, your second example with using the object.__getattribute__
doesn't seem to really be an issue. You retrieved the __dict__ for the
Guard class which is empty and is something we should not feel concerned
about being leaked.
Only way I see this as viable is if in "restricted" mode cell_contents
was removed from cell objects.
--
Scott Dial
[EMAIL PROTECTED]
[EMAIL PROTECTED]
_______________________________________________
Python-Dev mailing list
Python-Dev@python.org
http://mail.python.org/mailman/listinfo/python-dev
Unsubscribe:
http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
