Re: [TLS] The case for a single stream of data

[Ilari Liusvaara <[e-mail]>]

On Tue, May 09, 2017 at 10:35:37AM -0700, Colm MacCárthaigh wrote:
> On Tue, May 9, 2017 at 9:41 AM, Salz, Rich <[e-mail]> wrote:

> >The second problem is that middle-boxes can break any signaling. For
> > example a CDN or TLS accelerator may enable 0-RTT towards the back-end
> > origin without enabling it to the original client. In this model, the
> > client has *no* way to reason about retries or replay.
> >
> > A CDN is not a middlebox.  As far as the client is concerned a CDN *is*
> > the origin.
> 
> 
> No I don't think this works in transactional systems. For example; suppose
> the client performs an update or write "through" the CDN, and 0-RTT is
> being used on both sides. In the 0-RTT world, the CDN might be subject to
> replay between the CDN and the Origin. But as defined, the actual client
> gets no visibility of that. That breaks careful clients.  For example they
> may get a 500 back and assume that the request failed, without knowing that
> the request may be replayed any time in the next 10 seconds and therefore
> succeed.

Doesn't this imply that clients or CDN are using unsafe HTTP methods in
0-RTT data? Which is of course _seriously_ broken.

Because HTTP specification expressly forbids any and all updates and
writes using safe methods. Ignoring that causes very severe security
vulernabilities even today (e.g., causes essentially undefendable CSRF
attacks).



-Ilari