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Re: [XHR] Constructor behavior seems to be underdefined

From: Boris Zbarsky <bzbarsky@MIT.EDU>
Date: Mon, 02 Apr 2012 01:50:21 -0400
Message-ID: <4F793E1D.2090304@mit.edu>
To: Simon Pieters <simonp@opera.com>
CC: Cameron McCormack <cam@mcc.id.au>, public-webapps@w3.org, "public-script-coord@w3.org" <public-script-coord@w3.org>
On 4/2/12 1:33 AM, Simon Pieters wrote:
>> Yes, but what do they use for the origin of the Worker object itself?
>
> "Run a worker for the resulting absolute URL, with the script's browsing
> context of the script that invoked the method as the owner browsing
> context, with the script's document of the script that invoked the
> method as the owner document, with the origin of the entry script as the
> owner origin, and with worker global scope as the global scope."
> http://www.whatwg.org/specs/web-apps/current-work/multipage/workers.html#dom-worker
>
> Well, that's origin for the worker *script*.

Yes, that's not the same thing.

> The Worker *object* doesn't have an origin, I think.

Well, what controls which scripts can touch the Worker object?  That 
should be controlled by the origin of the window or document it's 
associated with, but the spec doesn't define what that is.

>> I.e. if you create one and then one of the documents involved has
>> .domain set on it, what happens?
>
> The document's effective script origin changes. The origin doesn't.

Sure.

> Workers use origin, not effective script origin, so setting
> document.domain should have no effect on workers even if you set it
> before creating the worker.

I think you're missing my point.

Say I have two documents d1 and d2, in windows w1 and w2 respectively. 
These are same-effective-origin (whether because they started that way 
or because both set document.origin to the same thing doesn't matter). 
Assume script in w1 has a reference to w2 (e.g. w2 is in a subframe).

Script running in w1 does:

   var worker = new w2.Worker(some_url);

Then script in w2 changes d2.origin, which changes the effective origin 
of w2 and d2.  What happens to script that runs later on in w1 and tries 
to call a method on |worker|?

For comparison, if Worker is replaced with Image in the above scenario, 
the correct answer is "a security exception is thrown" because for 
purposes of touching the image object itself what matters is whether the 
effective origin of the script that's running matches the effective 
origin of the image's ownerDocument.  Not that the spec actually says 
this anywhere that I can tell...

> http://www.whatwg.org/specs/web-apps/current-work/multipage/origin-0.html#origin-0
> has rules for specific things.

Yes, that's talking about a different thing entirely (e.g. for images 
this defines an origin for the image _data_, not for the image object 
itself; the two can obviously differ when the image load is not 
same-origin with the page the <img> tag is in).

Perhaps the spec terminology for the thing I'm after here is "effective 
script origin"?  That seems to be what it uses for Document.  But maybe 
it only does that so it can define it for scripts by reference to the 
document that loaded them?

In any case, the concept I'm after is "the thing that determines whether 
script at a particular effective script origin can touch your 
properties".  The spec (_some_ spec, at least) needs to define the value 
of this concept for all objects.  The simplest thing is to piggyback on 
the existing "all objects are associated with some global" bit in WebIDL 
and say that for a given object this concept has the same value as the 
global it's associated with (which is what Gecko, say, does in 
practice).  But then you have to define what the value of this concept 
is for globals (for Windows it would be the effective script origin of 
the .document, I believe) and which global each object is associated 
with (the point of this thread).

-Boris

-Boris
Received on Monday, 2 April 2012 05:50:53 GMT

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