Security Demands Simplicity (was: Private Slots)

Brendan Eich brendan at mozilla.com
Mon Jan 21 10:24:48 PST 2013


Andreas Rossberg wrote:
>
> On 21 Jan 2013 17:33, "Tom Van Cutsem" <tomvc.be at gmail.com 
> <mailto:tomvc.be at gmail.com>> wrote:
> >
> > So let's revisit the assumption: if a membrane does intercept and 
> wrap symbols, then two previously isolated pieces of code can never 
> come to share the same private symbol.
>
> I'm not sure I understand what "wrapping a symbol" would actually 
> mean. Are you implying that proxies that target a symbol should 
> actually be usable _as_ a symbol?
>
I think Tom meant wrapping as in membrane-wrapping, just as any object 
going through a membrane implemented by a proxy would be wrapped. I.e., 
symbols are not primitive values, they are objects. So membrane-wrapping 
a symbol means making a new symbol that can be mapped back to the 
original when flowing back across the membrane.

We had the old .public idea in play to do something like this. A proxy 
would never get access to a private symbol, only its "public key". If it 
had been endowed with a map of such back to the private identities, then 
it could unwrap. Otherwise, no privacy leak.

It seems even simpler to make symbols a distinct class of object 
(special case for property naming) and otherwise let them be 
membrane-wrapped. (Let's defer typeof result value.)

/be


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