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Subject: Re: RFC:Doing a NFSv4.1/4.2 Kerberized mount without a machine
 credential
From:   Trond Myklebust <trondmy@kernel.org>
To:     Chuck Lever III <chuck.lever@oracle.com>
Cc:     Rick Macklem <rick.macklem@gmail.com>,
        Linux NFS Mailing List <linux-nfs@vger.kernel.org>
Date:   Wed, 04 Jan 2023 12:25:54 -0500
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On Wed, 2023-01-04 at 14:25 +0000, Chuck Lever III wrote:
> 
> 
> > On Jan 3, 2023, at 11:41 PM, Trond Myklebust <trondmy@kernel.org>
> > 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.

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