On Wed, Jan 4, 2023 at 12:43 PM Trond Myklebust [off-list ref] wrote:

On Wed, 2023-01-04 at 14:25 +0000, Chuck Lever III wrote:

quoted

quoted

On Jan 3, 2023, at 11:41 PM, Trond Myklebust [off-list ref]
wrote:

I've been thinking about how to use a public key infrastructure to
provide stronger authentication of multiple individual users' RPC
calls
and multiplexing them across a shared TLS connection.

Since the client trusts the server through the TLS connection
authentication mechanism, and you have privacy guaranteed by that
TLS
connection, then  really all you want to do is for each RPC call
from
the client to be able to prove that the caller has a specific valid
identity in the PKI chain of trust.

So how about just defining a simple credential (AUTH_X509 ?)
containing
a timestamp, and a distinguished name, and have it be signed using
the
(trusted) private key of the user? Use the timestamp as the basis
for a
TTL for the credential so that the client+server don't have to keep
signing a new cred for each and every RPC call for that user, and
allow
the client to reuse the cred for a while as a shared secret, once
the
signature has been verified by the server.

A laptop typically has a single user. The flexibility of identity
multiplexing isn't necessary in this particular scenario.

Yeah, I don't particularly care about laptop use cases. Most
enterprises set up VPNs for dealing with them because users typically
need access to more services than just a NFS server.

I am interested in the general problem of authenticating RPC users
using certificates, since that is becoming more common due to the rise
of S3 object storage and cloud services. While AD and krb5+LDAP can be
extended into those environments too, there are plenty who choose not
to, because PKI is generally sufficient, and can be more flexible.

It sounds like you want some kind of TLS channel binding (rfc 9266).

However I think in general it's frowned upon to share different
authentication(s) over a secure channel. Or at least it sounds to me
that in rfc 9266 they are not allowing sharing of different
authentications over the same TLS session. But I could be wrong.

--
Trond Myklebust
Linux NFS client maintainer, Hammerspace
trond.myklebust@hammerspace.com