- From: Brandon Sterne <bsterne@mozilla.com>
- Date: Tue, 01 Mar 2011 09:59:58 -0800
- To: Adam Barth <w3c@adambarth.com>
- CC: Maciej Stachowiak <mjs@apple.com>, Anne van Kesteren <annevk@opera.com>, WebApps WG <public-webapps@w3.org>, Daniel Veditz <dveditz@mozilla.com>
I do think Content Security Policy offers a good opportunity to address the use cases Anne brought up. CSP already has a directive, frame-ancestors, that restricts the context in which a resource can be embedded as a <iframe>, <frame> or <object> to a list of origins. Perhaps we should expand the scope of the directive to include other elements (and change the directive name to something less frame-centric). I'd personally support such a change. -Brandon On 03/01/2011 12:32 AM, Adam Barth wrote: > +dveditz and +bsterne because they have strong opinions about CSP. > > Adam > > > On Tue, Mar 1, 2011 at 12:26 AM, Adam Barth <w3c@adambarth.com> wrote: >> On Mon, Feb 28, 2011 at 11:57 PM, Maciej Stachowiak <mjs@apple.com> wrote: >>> For what it's worth, I think this is a useful draft and a useful technology. Hotlinking prevention is of considerable interest to Web developers, and doing it via server-side Referer checks is inconvenient and error-prone. I hope we can fit it into Web Apps WG, or if not, find another goo home for it at the W3C. >>> >>> One thing I am not totally clear on is how this would fit into CSP. A big focus for CSP is to enable site X to have a policy that prevents it from accidentally including scripts from site Y, and things of that nature. In other words, voluntarily limit the embedding capabilities of site X itself But the desired feature is kind of the opposite of that. I think it would be confusing to stretch CSP to this use case, much as it would have been confusing to reuse CORS for this purpose. >> >> There's been a bunch of discussion on the public-web-security mailing >> list about the scope of CSP. Some folks think that CSP should be a >> narrow feature targeted at mitigating cross-site scripting. Other >> folks (e.g., as articulated in >> <http://w2spconf.com/2010/papers/p11.pdf>) would like to see CSP be >> more of a one-stop shop for configuring security-relevant policy for a >> web site. >> >> From-Origin is closely related to one of the proposed CSP features, >> namely frame-ancestors, which also controls how the given resource can >> be embedded in other documents: >> >> https://wiki.mozilla.org/Security/CSP/Specification >> >> Aside from the aesthetic questions, I'd imagine folks will want to >> include a list of permissible origins in the From-Origin header (or >> else they'd have to give up caching their resources). CSP already has >> syntax, semantics, and processing models for lists of origins, >> including wildcards. At a minimum, we wouldn't want to create a >> gratuitously different syntax for the same thing. >> >> Adam >> >> >>> On Feb 28, 2011, at 11:35 PM, Anne van Kesteren wrote: >>>> The WebFonts WG is looking for a way to prevent cross-origin embedding of fonts as certain font vendors want to license their fonts with such a restriction. Some people think CORS is appropriate for this, some don't. Here is some background material: >>>> >>>> http://weblogs.mozillazine.org/roc/archives/2011/02/distinguishing.html >>>> http://annevankesteren.nl/2011/02/web-platform-consistency >>>> http://lists.w3.org/Archives/Public/public-webfonts-wg/2011Feb/0066.html >>>> >>>> >>>> More generally, having a way to prevent cross-origin embedding of resources can be useful. In addition to license enforcement it can help with: >>>> >>>> * Bandwidth "theft" >>>> * Clickjacking >>>> * Privacy leakage >>>> >>>> To that effect I wrote up a draft that complements CORS. Rather than enabling sharing of resources, it allows for denying the sharing of resources: >>>> >>>> http://dvcs.w3.org/hg/from-origin/raw-file/tip/Overview.html >>>> >>>> And although it might end up being part of the Content Security Policy work I think it would be useful if publish a Working Draft of this work to gather more input, committing us nothing. >>>> >>>> What do you think? >>>> >>>> Kind regards, >>>> >>>> >>>> -- >>>> Anne van Kesteren >>>> http://annevankesteren.nl/ >>>> >>> >>> >>> >>
Received on Tuesday, 1 March 2011 17:59:10 UTC