[Harmony Proxies] Proposal: Property fixing

Tom Van Cutsem tomvc.be at gmail.com
Fri Jun 17 07:35:40 PDT 2011


2011/6/16 David Bruant <david.bruant at labri.fr>
>
>  I think I see also a potential security issue. In Tom's code, getters and
> setters of the non-configurable properties trigger code of what was in the
> handler. This is useful as a user to keep triggering the get and set traps,
> but it also leaks a reference to these functions (after a call to
> Object.getOwnPropertyDescriptor). In the current proposal, before a property
> becomes non-configurable, there is no access to any trap (unless having
> access to the object which implies having indirect access to all traps or
> the handler itself). After becoming a non-configurable accessor property,
> the get and set trap applied to the non-configurable properties become
> available as independant functions that can be passed around.
> Currently, one can revoke the access to an object with a membrane/wrapper,
> but with the leak, I think that all getter/setters will have to be wrapped
> as well (their call trap in particular)? Ok, maybe there is no security
> issue, but it adds a little bit more work.
>

I don't think there is a potential "leak" in the case of membranes: the
non-configurable property's get/set traps forward to handler.get/set, which,
if |handler| refers to a revoked proxy, will throw and not penetrate the
membrane, as expected.


> I was first enthousiastic by the general idea of keeping get/set traps
> through getter/setters (came up first with the fix trap, I think), but since
> there is an API allowing to extract these functions independently, I'm not
> really sure it's a good idea (in general) anymore.
>
> David
>
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