W3C home > Mailing lists > Public > public-webappsec@w3.org > March 2016

Re: [CSP] "sri" source expression to enforce SRI

From: Neil Matatall <oreoshake@github.com>
Date: Wed, 16 Mar 2016 07:18:15 -1000
Message-ID: <CAASU7Q55yDDi6ZxKF4bH85COinG87K40H9sO+Gi+0wYG5a_afQ@mail.gmail.com>
To: Patrick Toomey <patrick.toomey@github.com>
Cc: Frederik Braun <fbraun@mozilla.com>, "public-webappsec@w3.org" <public-webappsec@w3.org>
What can we do to get this moving? No matter the form, I don't think
there's any disagreement about whether or not this is valuable. We're
starting to see a proliferation of SRI attributes included in example
snippets for 3rd party assets. It's my gut instinct* that SRI has the
possibility of eclipsing CSP in terms of adoption, but that's a
different topic. It sounds like CSP bloat and SRI changes are the
biggest hurdles. Something that may alleviate both concerns:

  block-non-sri-resources: stylesheets, scripts(, images, videos, unicorns)

I would still love to see this as a part of CSP, especially if we're
talking about adding something related to noopener
https://twitter.com/mikewest/status/710025892970504193. Maybe this
separate header value can also work as a directive, just remove [:,]

* I'll take bets

On Tue, Feb 16, 2016 at 5:44 AM, Patrick Toomey
<patrick.toomey@github.com> wrote:
> On Wed, Feb 10, 2016 at 7:47 AM Frederik Braun <fbraun@mozilla.com> wrote:
>> On 09.02.2016 19:35, Craig Francis wrote:
>> > I'm forgetting the discussion a bit, but CSP already gives us:
>> >
>> > block-all-mixed-content
>> > upgrade-insecure-requests
>> >
>> > Maybe we could keep it as just one directive:
>> >
>> > block-non-sri-resources
>> >
>> > Or am I missing the more advanced cases like saying SRI is required for
>> > all JavaScript files, but not on CSS (doubt that is useful, as you might
>> > as well do both)... or maybe in the future SRI could be added to images,
>> > video, etc?
>> We'd need to think about compatibility assuming SRI will expand to other
>> tags.
>> I would be surprised if nobody wanted a report-mode and a block-mode and
>> a way to specify which subresources/elements should be subject to the
>> policy. (The list of elements could be abbreviated with a short-hand
>> form, e.g., "sri-v1" meaning scripts & styles.)
>> I guess this level of complexity (and Mark Nottingham's comment about
>> HPACK and entropy) warrants its own header?
> I'm curious where the line should be drawn between extending CSP and adding
> a new header? Not having been involved with CSP from day one, maybe this has
> already been discussed. But, I feel like CSP is a natural place to
> centralize on browser based security policies (like x-frame-options
> migrating to frame-ancestors). Adding a new header for each and every new
> good idea for browser security doesn't seem to scale. As has been mentioned
> in this thread prior, it feels like we are starting to bump up against
> practical size consideration issues. Whether the CSP header itself grows too
> large or we end up adding 50 headers to each HTTP response, there is an
> issue of bloat. It would be a shame to place some artificial cap on good
> ideas based on concerns for adding too many new headers and/or stretching
> the size of the CSP header. I personally feel like moving toward a
> centralized policy/manifest/resource sounds like the best way to handle
> this, but I think most of that discussion is best had over in the "header
> size and policy delivery" thread. I just wanted to bring it up here since I
> think the "where do we put it" discussion should be deferred until later,
> since it seems like this is a general concern for almost anything new that
> is proposed.
Received on Wednesday, 16 March 2016 17:18:45 UTC

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