On Oct 31, 2011, at 4:34 PM, Tab Atkins Jr. wrote: > On Mon, Oct 31, 2011 at 10:30 AM, Vincent Hardy <vhardy@adobe.com> wrote: >> Tab: you mention that more things than the shading language are contentious. >> Can you explain what these contentious issues are? >> Are you referring to the issues raised on the mailing list: >> http://www.w3.org/Graphics/fx/wiki/Custom_Filters#Issues_List >> or something else? > > I'm specifically referring to the issue of selecting through a vertex > filter, and the security issues with using a fragment shader to > extract information through a timing channel. Both of these are > unaddressed and probably difficult to deal with, and may take a decent > amount of time to deal with. The issue of selection in a shader (vertex and/or fragment) is the same as with other filter effect. It may be more obvious with vertex shaders, but essentially, the issue is the same. There has been a lot of discussion on the timing attack, but I would note two important things: a. it is much harder to time the processing time in a CSS shader than in WebGL. You can basically time a shader the same way to time any rendering in HTML/CSS/SVG. b. from discussions with Dean on the webkit-dev mailing list (I think Dean will forward his points), it is possible to mount a timing attack with regular filters. My point here is that these issues are important but not unique to CSS shaders. They apply to filter effects in general and I think they should be addressed together, one more reason to want to keep filter effects and shaders together. > > >> The CSS shaders proposal responds to the feCustom 'question' in the 'Filter >> Effects' specification and it seems more natural to integrate it than keep >> it a separate specification. > > Or we can just move the definition of <feCustom> to Shaders. Sure, but my point was that CSS shaders are in the scope of Filter Effects. VincentReceived on Tuesday, 1 November 2011 00:10:33 UTC
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