On Wed, 2023-01-04 at 18:06 +0000, Chuck Lever III wrote:

quoted

On Jan 4, 2023, at 12:25 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.

The trend I've seen is that enterprises are moving their important
services out of from behind VPNs and into the cloud. Each such
service is responsible for providing appropriate levels of
authentication and confidentiality via a single-sign on service
and an in-transit encryption capability.

quoted

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.

We had SPKM. Would that not work?

The SPKM spec was withdrawn following review by the IETF security
working groups. Reviving it and pushing it again would require
addressing those comments.

Furthermore, SPKM was always intended as a full blown RPCSEC_GSS
mechanism, which seems like overkill for this use case.

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