Subject: HPACK security considerations

From: Martin Thomson <[email-masked]>
Date: Tue, 10 Jun 2014 17:12:04 -0700

I just opened https://github.com/http2/http2-spec/pull/517

It's a fairly comprehensive rework of the security considerations
section, which - in my opinion - was a mite too optimistic.  The new
proposal includes coverage of:

* the attack in the general sense,
* how the attack might apply in HPACK and HTTP,
* particular areas of concern,
* how HPACK inherently mitigates these attacks,
* what environments might need additional mitigation, and
* some suggested mitigation strategies.

Mitigation strategies that I have described are:

* actor-based isolation (a generalized application of the origin
isolation principle)
* destroy values on failed guesses (thanks here to Adam Barth for the
idea), either probabilistically, or based on a count, with a
recommendation that shorter values be made harder to guess
* specific protection for "special" header fields

--Martin