Re: [Acme] AD Review: draft-ietf-acme-tls-alpn-05

[Eric Rescorla <[e-mail]>]

On Wed, Dec 26, 2018 at 6:56 AM Ilari Liusvaara <[e-mail]>
wrote:

> On Mon, Dec 24, 2018 at 12:47:30PM -0800, Eric Rescorla wrote:
> >
> > S 4.
> > >      properly segregates control of those names to the users that own
> > >      them.  This means that if User A registers Host A and User B
> > >      registers Host B the server should not allow a TLS request using a
> > >      SNI value for Host A to be served by User B or Host B to be
> served by
> > >      User A.  If the server allows User B to serve this request it
> allows
> > >      them to illegitimately validate control of Host A to the ACME
> server.
> >
> > Isn't this the property you say doesn't hold in S 6 below. As I
> > understand it, the rationale for this design is that people who opt in
> > to acme-tls/1 won't do this, no?
>
> No. This is a different property than one mentioned in S6. This is due
> to different SNI used.
>

That appears to be what S 6 says as well:

   domain names they controlled (i.e. if User A registered Host A and
   User B registered Host B with a service provider that User A wouldn't
   be able to respond to SNI traffic for Host B).  This turns out not to

So at minimum some improved text is required here.

-Ekr

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