Bug 161396 – Object.setPrototypeOf() should throw when used on a cross-origin Window / Location object

• Component: DOM
• Status: RESOLVED FIXED

[Chris Dumez]

Object.setPrototypeOf() should throw when used on a cross-origin Window / Location object:
- https://html.spec.whatwg.org/#windowproxy-setprototypeof
- https://html.spec.whatwg.org/#location-setprototypeof
- http://www.ecma-international.org/ecma-262/6.0/#sec-object.setprototypeof (step 7)

Firefox and Chrome already throw. However, WebKit merely ignores the call and logs an error message.

[Chris Dumez]

Created attachment 287421 [details]
Patch

[Chris Dumez]

Created attachment 287423 [details]
Patch

[Boris Zbarsky]

Object.setPrototypeOf should throw on a same-origin Window too (but not on same-origin Location).

[Chris Dumez]

(In reply to comment #3)
> Object.setPrototypeOf should throw on a same-origin Window too (but not on
> same-origin Location).

As mentioned in the ChangeLog, I intentionally did not change the same-origin case in this patch. I'll consider making this change in a follow-up.

Also, could you clarify why it would throw for same-origin Location? The specification for Location and Window seems identical:
- https://html.spec.whatwg.org/#windowproxy-setprototypeof
- https://html.spec.whatwg.org/#location-setprototypeof

[Boris Zbarsky]

> I'll consider making this change in a follow-up.

Ah, ok.

> Also, could you clarify why it would throw for same-origin Location? 

I assume that's missing a negative somewhere...

I was wrong.  It looks like the spec says to throw for Object.setPrototypeOf on a same-origin location (and at least Gecko does in fact do that).

[Ryosuke Niwa]

Comment on attachment 287423 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=287423&action=review

> Source/JavaScriptCore/runtime/ObjectConstructor.cpp:233
> +        throwTypeError(exec, ASCIILiteral("permission denied"));

Capitalize p?

[Chris Dumez]

Committed r205205: <http://trac.webkit.org/changeset/205205>