Re: [nfsv4] Martin Duke's Discuss on draft-ietf-nfsv4-rpc-tls-08: (with DISCUSS and COMMENT)

[Chuck Lever <[e-mail]>]

Hi Martin-

Thank you for your comments.


> On Jun 25, 2020, at 4:56 PM, Martin Duke via Datatracker <[e-mail]> wrote:
> 
> ----------------------------------------------------------------------
> DISCUSS:
> ----------------------------------------------------------------------
> 
> This presumably a trivial fix but I think it's important enough to be a DISCUSS:
> 
> I think the document needs some discussion of the security properties of TLS1.3
> early data over TCP, if only to refer to Section 8 of RFC 8446 (replay) and
> mention that it is not forward-secure, unlike the rest of the payload.

We could extend the first paragraph of Section 7, as follows:

OLD:

7.  Security Considerations

   One purpose of the mechanism described in the current document is to
   protect RPC-based applications against threats to the confidentiality
   of RPC transactions and RPC user identities.  A taxonomy of these
   threats appears in Section 5 of [RFC6973].  Also, Section 6 of
   [RFC7525] contains a detailed discussion of technologies used in
   conjunction with TLS.  Implementers should familiarize themselves
   with these materials.

NEW:

7.  Security Considerations

   One purpose of the mechanism described in the current document is to
   protect RPC-based applications against threats to the confidentiality
   of RPC transactions and RPC user identities.  A taxonomy of these
   threats appears in Section 5 of [RFC6973].  Also, Section 6 of
   [RFC7525] contains a detailed discussion of technologies used in
   conjunction with TLS.  Implementers should familiarize themselves
   with these materials.

   Once a TLS session is established, the RPC payload carried on TLSv1.3
   is forward-secure. However, implementers need to be aware that replay
   attacks can occur during session establishment. Remedies for such
   attacks are discussed in detail in Section 8 of [RFC 8446].


> ----------------------------------------------------------------------
> COMMENT:
> ----------------------------------------------------------------------
> 
> Thank you for this draft. I fully support bringing TLS into more use cases of
> this type.
> 
> Some comments:
> Sec 1.
> "Moreover, the use of AUTH_SYS remains common despite the adverse effects that
> acceptance of UIDs and GIDs from unauthenticated clients brings with it.
> Continued use is in part because:
> 
> Per-client deployment and administrative costs are not scalable. Administrators
> must provide keying material for each RPC client, including transient clients.
> Host identity management and user identity management must be enforced in the
> same security realm. In certain environments, different authorities might be
> responsible for provisioning client systems versus provisioning new users."
> 
> The text above says that something is still in use because..., and then
> mentions two things that are bad. I think the two items are supposed to refer
> to GSS?

Indeed, they do.

NEW:

   Moreover, the use of AUTH_SYS remains common despite the adverse
   effects that acceptance of UIDs and GIDs from unauthenticated clients
   brings with it.  Continued use is in part because:

   *  Per-client GSS deployment and administrative costs are not
      scalable.  Administrators must provide keying material for each
      RPC client, including transient clients.

   *  GSS host identity management and user identity management must be
      enforced in the same security realm.  In certain environments,
      different authorities might be responsible for provisioning client
      systems versus provisioning new users.


> Sec 4.2 This sure looks like normative text, so s/must not/MUST NOT "...
> utilize the remote TLS peer identity for RPC user authentication"

This paragraph formerly had MUST NOT, but was rewritten to address this issue:

  https://github.com/chucklever/i-d-rpc-tls/issues/5

There was a concern that the existing statement was not specific enough to make
it a compliance requirement. In particular, some implementations do want to use
the peer identity for access control decisions, though not on a per-user basis.

I'm open to some change here, but I'd like to hear suggestions about wording
to make the new compliance statement more actionable.


> Sec 5.1.2 Similarly, s/should/SHOULD "...employ ConnectionIDs of at least 4
> bytes in length."

No objection to using SHOULD.


--
Chuck Lever