[lamps] Re: TLS Client Certificates; a survey

[Viktor Dukhovni <[e-mail]>]

On Mon, Mar 23, 2026 at 12:11:03PM -0500, Nico Williams wrote:

> I've been imagining a TLS extension that includes details on how to
> connect to a service that will have the same server certificate (or
> substantially similar: same names and issuer) as the one being presented
> as a client certificate (with serverAuth and not clientAuth).  Then the
> server can connect, verify that the "client's server" has the same (or
> substantially similar) certificate as the client and... presto: you're
> using the serverAuth certificate as intended, as a server certificate! :D
> 
> The connection details extension would carry: the FQDN that the client
> is authenticating as, and optionally one or more IP address and port
> number pairs.

The workaround is much simpler, the server operator opts in to enable
the workaround, and then serverAuth-only certs presented by a client are
validated as server certificates (in terms of EKU requirements), even
though the peer's actual rôle is "client".

-- 
    Viktor.  🇺🇦 Слава Україні!