Re: [yang-doctors] Yangdoctors last call review of draft-ietf-netconf-keystore-02

[Juergen Schoenwaelder <[e-mail]>]

On Wed, Jul 19, 2017 at 09:06:59PM +0000, Kent Watsen wrote:
> Hi Juergen,
> 
> Thanks for your review.  Below are my responses to your comments.
> 
> PS: why is [e-mail] in the CC?

I used the datatracker form and it does what it does.
 
> - There are a number of binary fields where you show explanatory text
>   in the examples instead of encoded data. Is this always clear?
> 
>   <private-key>...</private-key> <!-- elipsis placeholder for a base64 encoded key -->
> 
> <KENT> This issue has been raised by others as well.  I used to
> have full base64 values, but it made the examples very difficult
> to read.  Hmmm, I like your suggestion, but the resulting line
> is much longer than allowed.  I could line-wrap, but the result
> looks worse.  Any other suggestions?

Assuming people will figure out that ... is just a marker, what about
this?
 
   <private-key>...</private-key> <!-- base64 encoded key  -->

> - I am not sure I understand trusted-host-keys. On systems that have
>   multiple user accounts, you usually have a per account list of
>   trusted host keys in addition to a global system wide list. Perhaps
>   make it clear that this models the global known hosts list only?
> 
> <KENT> it's a list of lists, so there can be many different
> sets a host-keys defined, with each application/use pointing
> to its own entry.  The ietf-ssh-client module's grouping has
> a leafref to a specific entry.  FWIW, this grouping is
> used by ietf-netconf-client module.  At the moment, there
> no other uses of this grouping.  I think that you may be
> getting confused between the key the server presents (the
> host-key) versus the key user presents.
> .

I though these are the authorized host keys? Yes, I am confused. If
these are user public keys, they should not be called host keys. But
yes, I am confused (but I started to read the other documents).

> - Should the document title be aligned with other YANG module
>   definitions, so it is easier to spot it?
> 
> <KENT> I don't understand, what do you mean?
 
We often use "[A] YANG Data Model for ....".

https://en.wikipedia.org/wiki/YANG#Usage_in_Standards

The current name does not say YANG (sometimes I search for YANG in the
RFC index) and Keystore is also pretty broad given the related work we
have.
 
> - Since crypto algorithms come and go, is it reasonable to have the
>   identities defined in a rather static RFC? Would an IANA maintained
>   identity module perhaps make more sense?
> 
> <KENT> Unsure, but I wouldn't suspect needing to make that
> kind of update for a long time.  If we were to define a 
> module for algorithm identities, it might lead to us wanting
> to define every algorithm (not just public-key algs), which
> could take some time...

I think an IANA maintained registry can be as incomplete or complete
as the I-D. I understand that the mechanics of working out the proper
registry can be painful (there likely are already N registries) but
clearly crypto algorithm identities must be easily extensible.

> - Oh, I now see that the key length is embedded in the algorithm
>   identity. Perhaps clarify this earlier, see my confused comments
>   above. Anyway, I think this makes the need for an IANA maintained
>   module even stronger.
> 
> <KENT> yes, but your comment before was valid.  I don't see why
> this makes a stronger case though...

Well, the notion of what is strong changes every N years.

> - Why do certificate names have to be unique across all keys?
> 
> <KENT> because otherwise leafrefs might be ambiguous, right?

OK. Perhaps explain this detail so it is obvious to everybody.

> - Since the certs of a key do not contain a signature, where are signed
>   certificates stored or are they outside the scope of the model?
> 
> <KENT> I'm confused, certificates are signed structures already...

Well, the description of certificates/certificate/value says:

   An unsigned PKCS #7 SignedData structure, as specified
   by Section 9.1 in RFC 2315, containing just certificates
   (no content, signatures, or CRLs), encoded using ASN.1
   distinguished encoding rules (DER), as specified in
   ITU-T X.690.

Yes, I am confused how this works.
 
> - Is there any text needed to explain what happens if actions can't be
>   carried out, e.g., the algorithm identity is not supported? Can a
>   client actually learn which algorithm identities are supported or is
>   the approach simply trial and error?
> 
> <KENT> If an action fails, then standard NC/RC error is returned.
> There is no support to learn which algorithms a server supports,
> but by supporting this module, the server must support all of
> these algorithms.

This may raise a red flag by the security people. They take crypto
agility serious and there might be very valid reasons to not support
some of the algorithms at a certain point in time. Actually, there is
a difference between supporting (in the sense of implemented) and
enabled (in the sense can be used).

Anyway, this is usually regulated by protocol specifications,
protocols often define mandatory to implement algorithms etc. Is the
keystore going to interfer with this? Or should it better be silent
about what is mandatory?
 
> - I am not sure what 'trusted certificate' here really means. What you
>   are modeling is a set of sets of certificates. What such a set means
>   depends on where this list is used. I am not sure what it means for
>   a certificate in such a set to be 'trusted'.
> 
> <KENT> yes, the certs may be used by different modules for
> different use-cases, but they'd always be trusted.  E.g.,
> the certs preinstalled by a browser...

If an application (i.e. a RESTCONF server) trusts some set of
certificates, the certificates in that set become trusted by that
specific application. But without concrete context, isn't it unclear
what is trusting a listed certificate and why?
 
> - What about the // rename to 'data' comment? I like it, renaming to
>   list certificate { key name; leaf name; leaf data; } seems less
>   confusing (and it is even shorter). Perhaps something along this
>   line would be better (not sure I like certificate-set)
> 
> 	 +--rw certificate-set* [name]
>          |  +--rw name                   string
>          |  +--rw description?           string
>          |  +--rw certificate* [name]
>          |     +--rw name    string
>          |     +--rw data?   binary
> 
> 
> <KENT> "set" doesn't sound too bad - dunno.  Regarding moving
> "data", see the tail-end of the email I sent on July 11.

Aha. Not sure this resolves this (or I looked at the wrong message).

/js

-- 
Juergen Schoenwaelder           Jacobs University Bremen gGmbH
Phone: [phone]         Campus Ring 1 | 28759 Bremen | Germany
Fax:   [phone]         <http://www.jacobs-university.de/>