Re: Subresource Integrity strawman.

On 9 Jan 2014, at 8:10 am, Michal Zalewski <> wrote:

> Also, to circle back to the fingerprinting angle: the logged-in state
> aside, let's say that there's a HTML page or a JSON response that is
> mostly static, except for a first name, e-mail address, or a phone
> number somewhere in the body. Further, for the sake of simplicity,
> let's say that it's cacheable on the client.
> I could precompute hashes for the static content + every common first
> name, every phone number in a particular area code, or any of the
> e-mail addresses I care about; and then rapidly attempt to load that
> subresource with varying integrity=. By monitoring violations, I could
> quickly determine that my victim's name on Facebook is Bob, or that
> his number is 650-555-5555, right?
> I don't think this is easily attainable without subresource integrity…

Seems like this could be mitigated by only allowing the integrity-enabled cache to consider responses that are storable by a shared cache… you'd need a proviso that any response loaded over HTTPS needs an explicit CC: public.



Mark Nottingham

Received on Thursday, 9 January 2014 04:25:10 UTC