Re: [Taps] Paul Wouters' Yes on draft-ietf-taps-interface-24: (with COMMENT)

[Michael Welzl <[e-mail]>]

Dear Paul,

I now see what happened here. I have made this harder to track by answering the DISCUSS items only in my email - when, in fact, we have addressed or at least discussed everything on github. I’m sorry!  There were so many emails, I also didn’t want to make the answers too long.

As a general comment, for everyone else who might see this: if you miss answers to your COMMENTS, we’re sorry!  - but you’re likely to find them fast by going to:
https://github.com/ietf-tapswg/api-drafts/issues
… removing “is:open” from the search field but instead writing your last name there.


Paul, please see below:


> ----------------------------------------------------------------------
> COMMENT:
> ----------------------------------------------------------------------
> 
> I updated my discuss items to non-blocking comments. I'm still a bit concerned
> that some security items are not fully addressed by the API or its Security
> Considerations. Resolving my comments would make the document a bit more clear
> and useful I think.
> 
> I'm not sure that the model really expands from netflows to IP flows (or TOR)
> in the future.
> 
> I'm not sure the Security Considerations warn enough about re-using the same
> credentials with different protocols/auth mechanisms. (eg TLS and IKEv2, or TLS
> 1.2 and QUIC, or using RSA as RSA-PKCS1.5 as well as RSA-PSS)
> 
> Unqualified Hostname vs FQDN seems a security risk punted mostly to the
> application.

These are new comments as part of the COMMENT block. As with the others, we will file an issue on our github and resolve them there. Personally, I think we should use these comments to strengthen our security considerations section (e.g., to warn about the security risk when not using an FQDN. Indeed such a warning does now exist in the text, and using an FQDN is qualified  with a SHOULD, but the security considerations section could point at it once again).


Here comes an answer for the other COMMENT items on the basis of what happened on github:


> I don't understand this code:
> 
>        Connection := Preconnection.Initiate()
>        Connection2 := Connection.Clone()
> 
>        Connection -> Ready<>
>        Connection2 -> Ready<>
> 
>        //---- Ready event handler for any Connection C begin ----
>        C.Send(messageDataRequest)
> 
> Where does "C" come from in "C.Send" ? The comment says "any Connection C"?

Issue: https://github.com/ietf-tapswg/api-drafts/issues/1368
PR to resolve: https://github.com/ietf-tapswg/api-drafts/pull/1413

We hope that the text that we added makes this clear enough: this code block is an event handler for Connection C. Either it gets C as a parameter, or it’s in some other way associated to Connection C.


> I have a question on this code:
> 
>        Preconnections are reusable after being used to initiate a
>        Connection, whether this Connection was closed or not. Hence, it
>        would be correct to continue as follows after the above example:
> 
>        //.. carry out adjustments to the Preconnection, if desired
>        Connection := Preconnection.Initiate()
> 
> What would happen here? I can imagine a "compiler" turning this into
> a noop.  I can also see it would kill the existing Connection state and
> start a new one. This could be to a different IP address (eg if the DNS
> name has A and AAAA). When starting a new one, what would happen to any
> Message or Event queues for Connection ?

Issue: https://github.com/ietf-tapswg/api-drafts/issues/1369
PR to resolve: https://github.com/ietf-tapswg/api-drafts/issues/1369

A Preconnection is just a data structure, used as a template to create a Connection - so, the call to Initiate() after adjustments wouldn’t affect the already ongoing Connection.
We hope that the text that we added makes this clear enough now.


>        Preconnection.AddRemote(RemoteCandidates)
> 
> Should this not technically be:
> 
>        Preconnection.AddRemote([]RemoteCandidates)
> 
> as the array contains at least a host and a stun server candidate?
> 
> Maybe this is just the difference between you using the variable you define
> that has been assigned, versus a more C like prototype format, eg:
> 
>        Preconnection := NewPreconnection([]LocalEndpoint,
> 
> So I guess if your example here had set LocalEndpoint := [a,b] you would not
> have used [] in the call ?

Issue: https://github.com/ietf-tapswg/api-drafts/issues/1371
Commit: https://github.com/ietf-tapswg/api-drafts/commit/e1ca6015d25c8a2a3f78f99cfc552ed4fd63019e

… this should be resolved now.


> Section 6.1.4
> 
> Perhaps it would be useful to add a Local Endpoint with ephemeral port before
> the Local Endpoint with static port example, as the ephemeral port should be
> the far more common case. Right now the examples might give the wrong impression
> a local port MUST be specified.

Yes, good catch, thanks!   - addressed:

Issue: https://github.com/ietf-tapswg/api-drafts/issues/1374
PR: https://github.com/ietf-tapswg/api-drafts/pull/1431


> SecurityParameters.Set() seems to allow to set our identiy and our certificate,
> but not the remote peer's identity or certificate? For example, one might want
> to pin a remote certificate and not just rely on a WithHostname() identifier
> being present as subjectAltname on a certificate.

Issue: https://github.com/ietf-tapswg/api-drafts/issues/1375
PR: https://github.com/ietf-tapswg/api-drafts/pull/1430
(this PR introduces client- and server- certificates)


>       The Connection state, which can be one of the following:
>        Establishing, Established, Closing, or Closed.
> 
> I think the text in Section 8 should more clearly show the property names if the
> goal is to have different implementations use the identical name. Eg in this
> case, why not write: The Connection state ("state"). The next two entries are
> similarly lacking a clear keyword to use:
> 
>        Whether the Connection can be used to send data.
> 
>        Whether the Connection can be used to receive data.
> 
> eg. why not define words for these to implementations will use the same words,
> in this case perhaps ReadySend and ReadyRcv ?
> Writing that now, perhaps "state" should be "State" then ?

Issue: https://github.com/ietf-tapswg/api-drafts/issues/1377
PR: https://github.com/ietf-tapswg/api-drafts/pull/1437

This PR incorporates your suggestion by introducing three read-only properties: connState (to query for “Establishing”, “Established”, “Closing”, “Closed"), canSend, canReceive.


> Section 8.1.1:
> 
>        If this property is an Integer
> 
> It is best to define the actual type in this document and not let
> implementations choose, if the goal is to try and harmonize implementations. I
> also see no non-integer value being given here ?

We got a similar comment about this from Lars Eggert, so we discussed both in this issue:
https://github.com/ietf-tapswg/api-drafts/issues/1346

This is a more general thing, affecting several properties. After trying and discussing (at an interim) a somewhat heavy-handed approach to solve this for all of them:
https://github.com/ietf-tapswg/api-drafts/pull/1409
… we ended up with what we agreed was a better way to do it, in this PR: https://github.com/ietf-tapswg/api-drafts/pull/1410

Now it’s a non-negative Integer, with a defined special value of 0, and how to specify "Full Coverage” is explained in the text.


I hope this helps - my apologies for not immediately answering how we addressed the COMMENT items !

Cheers,
Michael