Le 03/12/2014 19:10, Jason Orendorff a écrit :
On Wed, Dec 3, 2014 at 9:04 AM, David Bruant<bruan...@gmail.com> wrote:
A script which builds a weakmap may legitimately later assume the weakmap is
filled. However, passing the weakmap to a mixed-trusted (malicious or buggy)
script may result in the weakmap being cleared (and break the assumption of
the weakmap being filled and trigger all sorts of bugs). Like all dumb
things, at web-scale, it will happen.
OK. I read the whole thing, and I appreciate your writing it.
There's something important that's implicit in this argument that I
still don't have yet. If you were using literally any other data
structure, any other object, passing a direct reference to it around
to untrusted code would not only be dumb, but obviously something the
ES spec should not try to defend against. Right? It would be goofy.
Object.freeze and friends were added to the ES spec for the very purpose
of being able to pass direct reference to an object and defend against
unwanted mutations. à propos d'une
Is Object.freeze goofy?
The language just is not that hardened. Arguably, the point of a data
structure is to be useful for storing data, not to be "secure" against
code that **has a direct reference to it**. No?
The way I see it, data structures are a tool to efficiently query data.
They don't *have* to be arbitrarily mutable anytime for this purpose.
It's a point of view problem, but in my opinion, mutability is the
problem, not sharing the same object. Being able to create and share
structured data should not have to mean it can be modified by anyone
anytime. Hence Object.freeze, hence the recent popularity of React.js.
So what's missing here is, I imagine you must see WeakMap, unlike all
the other builtin data structures, as a security feature.
I'm not sure what you mean by "security feature". Any API is a security
feature of sort.
Specifically, it must be a kind of secure data structure where
inserting or deleting particular keys and values into the WeakMap does
*not* pose a threat, but deleting them all does.
Can you explain that a bit more?
I see the invariant you're talking about, I agree it's elegant, but to
be useful it also has to line up with some plausible security use case
and threat model.
The ability to clear any WeakMap anytime needs to be equally justified
in my opinion. I'm curious about plausible use cases.
What about making 'clear' an own property of weakmaps and make it only
capable of clearing the weakmap it's attached to?
David
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