As people have pointed out, this is now DANCE.

On Tue, May 20, 2025 at 11:05 PM Viktor Dukhovni <[email protected]>
wrote:

> On Tue, May 20, 2025 at 03:46:10PM -0400, Phillip Hallam-Baker wrote:
>
> > > > Browser does TLS client side auth presenting the cert it was issued.
> > >
> > > With TLSA 3 1 X records, this could be just a raw public key.
> > >
> >
> > That isn't going to work because users have multiple devices. It isn't
> > worth building out anything for the single device use case.
>
> Nothing about a raw public key makes it "single device".  The
> "certificate" content (name binding) is in the TLSA record, and
> so everything else in the certificate is often redundant.
>
> > Each device should have its own key. Much easier to make that work
> > correctly...
>
> Of course, and its own "3 1 1" record (separate DNS name, separate
> "3 1 1" payload binding the key for that device).
>
> > I did also consider the LetsEncrypt/ACME route but what does that buy
> > us?  The relying party in this case has just as much opportunity to
> > perform an unspoofed DNS lookup as a CA. Not sure what WebPKI is
> > buying us.
>
> Not much at all for client certificates.
>
> > > I may be able to do add the relevant support in OpenSSL, DANE for
> server
> > > certs is already implemented, the main obstacle is that there isn't a
> > > ubiquitous API for authenticating client-provided DNSSEC chains.  So
> > > validation of the client chain or fetching it on demand would be up to
> > > the application via its preferred DNS library, and not directly
> > > performed by OpenSSL.  Once the server provides the relevant TLSA
> > > records to the library, the certificate verification can proceed using
> > > existing DANE support which is essentially direction agnostic.
> > >
> >
> > Perhaps a side meeting in MADRID, maybe some of the browser folk could
> > provide input...
>
> I'm yet to make travel plans, but may well attend.  If so, sure let's
> meet.  Indeed we last met in person at a Berlin IETF circa 2014, where
> this topic may even have come up.  Shumon was there too.
>
> > There are multiple issues here.
> >
> > 1) Client to server signalling.
> > 2) Server to client signalling.
> > 3) Issue of the certificate signing certificates.
> > 4) Issue of the end entity certificates.
> > 5) Signalling enrollment for TCSA
>
> Yes, all of the above.  My SMTP server supports and sees some
> connections with clients that use the DANE TLSA "3 1 [012]"
> records to validate the negotiated raw public key.
>
> --
>     Viktor.
>
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