W3C home > Mailing lists > Public > public-webappsec@w3.org > June 2013

Re: [filter-effects][css-masking] Move security model for resources to CSP

From: Boris Zbarsky <bzbarsky@MIT.EDU>
Date: Sat, 01 Jun 2013 18:16:21 -0400
Message-ID: <51AA72B5.9010200@mit.edu>
To: Dirk Schulze <dschulze@adobe.com>
CC: "public-webappsec@w3.org" <public-webappsec@w3.org>
On 6/1/13 2:25 PM, Dirk Schulze wrote:
> It can't for SVG Masks, SVG Filters and SVG Paint Servers (pattern, linearGradient, radialGradient). They just influence the visual appearance on the screen without read backs.

I assume we're disregarding timing channel attacks for the time being, 
right?

> The following example would NOT expose data:
>      <clipPath>
>          <text>Password</text>
>      </clipPath>

Again, I'm more worried about stealing path data.  Especially path data 
that's not necessarily meant to be a clipping path in the SVG being 
linked to.  Is that something I should worry about, or only things that 
are explicitly inside <clipPath> elements in the target svg?  If it's 
the latter, that helps a lot.

> But the text can be transformed to a path (for instance with Illustrator). Then evil.com can clip an element with this resource and somehow try to get the hit regions (let the user move over the the object a lot of times like you would do on a lottery scratch ticket).

Nah, you just use elementFromPoint from 
http://dev.w3.org/csswg/cssom-view/#extensions-to-the-document-interface 
and do whatever sort of sampling you want.

> This would mean that mybank.com would not use a proper session management

Huh?  If you're logged into the bank at the same time as you happen to 
load an evil site, we need to worry about that.

> The clip-path property does allow CSS Shapes as well: clip-path: polygon() [1]. This is very helpful for doing CSS animations or transitions on a clipping path. Do you think that could be a possible threat for privacy as well?

As much as "must be inside <clipPath> SVG".

-Boris
Received on Saturday, 1 June 2013 22:16:51 UTC

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