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Re: style-src and inline style

From: Collin Jackson <collin.jackson@sv.cmu.edu>
Date: Thu, 14 Apr 2011 15:55:23 -0700
Message-ID: <BANLkTinioEzphnmJcmgFdb3B0rtyoEQZig@mail.gmail.com>
To: Adam Barth <w3c@adambarth.com>
Cc: Brandon Sterne <bsterne@mozilla.com>, Bil Corry <bil@corry.biz>, gaz Heyes <gazheyes@gmail.com>, Daniel Veditz <dveditz@mozilla.com>, public-web-security@w3.org
On Thu, Apr 14, 2011 at 3:38 PM, Adam Barth <w3c@adambarth.com> wrote:

> On Thu, Apr 14, 2011 at 1:51 PM, Brandon Sterne <bsterne@mozilla.com>
> wrote:
> > On 4/11/11 11:19 AM, Brandon Sterne wrote:
> >> On 4/7/11 9:17 AM, Collin Jackson wrote:
> >>> I'd like to suggest option 3, which is to block inline styles by
> default
> >>> only if a style-src directive is present (authors can use style-src
> >>> 'inline' if they want to use style-src with inline styles).
> >>>
> >>> Attaching default blocking behaviors to specific directives rather than
> >>> to the entirety of CSP makes the spec more extensible and allows us to
> >>> support a variety of use cases while still keeping policies simple.
> >>
> >> I think this is the best solution offered so far.  If there are no
> >> objections, I'll make this change to the spec draft as well.
> >
> > I'm in the process of making this change, and I'm wondering how best to
> > extend this to be consistent with script-src.
> >
> > The proposal is to disable inline style when style-src is present and
> > only allow it when the 'inline' keyword is added to style-src.
> >
> > For script-src, however, adding the 'inline' keyword to script-src is
> > less desirable than the disable-xss-protection options token we had
> > previously (from the standpoint of conveying sufficient caution when
> > enabling inline script).  One option would be to change 'inline' to
> > 'inline-style' that only has an effect when declared inside style-src,
> > and have a different keyword for inline script, potentially keeping
> > 'disable-xss-protection'.  Yes, that would be less consistent
> > syntactically, but it would preserve the "Foot Gun Here" element.
> >
> > Separately, it's somewhat less elegant to say that inline script is
> > disabled when any of:
> >
> >  1. script-src
> >  2. object-src
> >  3. ...
> >
> > are present (rather than the single style-src directive), but I haven't
> > really heard a better suggestion so far.
>
> One option is to say that inline script is disabled when script-src is
> present (i.e., not triggering that restriction on object-src).  The
> thought process is that you can't tell the "src" of inline script, so
> script-src should block it.


Should we disable inline objects (via data: URLs) when object-src is present
(i.e., not triggering that restriction on script-src)?

Collin Jackson
Received on Thursday, 14 April 2011 22:56:31 GMT

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