W3C home > Mailing lists > Public > public-webappsec@w3.org > January 2014

Re: Subresource Integrity and fingerprinting

From: Mike West <mkwst@google.com>
Date: Thu, 9 Jan 2014 09:16:21 +0100
Message-ID: <CAKXHy=dXfhWVx62DkOtg+k63ByOAOHp_9NmUfUuwg_0s99UFmw@mail.gmail.com>
To: Mark Nottingham <mnot@mnot.net>
Cc: Michal Zalewski <lcamtuf@coredump.cx>, Devdatta Akhawe <dev.akhawe@gmail.com>, Joel Weinberger <jww@chromium.org>, "public-webappsec@w3.org" <public-webappsec@w3.org>, Frederik Braun <fbraun@mozilla.com>
Relying on CORS assumes that any sensitive data that should be available
cross-origin would have appropriate headers applied to any response.

-mike

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On Thu, Jan 9, 2014 at 9:14 AM, Mark Nottingham <mnot@mnot.net> wrote:

> Doesn't relying on CORS assume that sensitive data will never be available
> cross-origin?
>
> Sent from my iPhone
>
> On 9 Jan 2014, at 3:26 pm, Michal Zalewski <lcamtuf@coredump.cx> wrote:
>
> >> What is the mitigation that you're agreeing with, Michal? Only
> performing
> >> integrity checks on resources delivered with explicitly public
> cache-control
> >> or CORS headers?
> >
> > Well, Eduardo's take is that we should just require CORS and not dance
> > around it. Maybe that would work, although it does require explicit
> > cooperation of the third-party site that hosts a particular download,
> > has a copy of jQuery, etc. I'd imagine this won't always be painless.
> >
> > An alternative would be to unconditionally fail if integrity= is
> > specified and none of the following three conditions are met:
> >
> > 1) The subresource is same-origin with the requestor,
> >
> > 2) The subresource is publicly cacheable by proxies (either due to
> > implicit caching rules, or due to Cache-Control),
> >
> > 3) There is a CORS header that explicitly permits this subresource to
> > be accessed across origins.
> >
> > /mz
>
Received on Thursday, 9 January 2014 08:17:10 UTC

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