Re: Gen-art LC review: draft-ietf-netconf-restconf-15

[Robert Sparks <rjsparks@xxxxxxxxxxx>]

On 7/29/16 3:36 PM, Andy Bierman wrote:

Hi,

I will add this review to the list.

A new version in in progress.

Some comments inline

On Fri, Jul 29, 2016 at 1:11 PM, Robert Sparks <rjsparks@xxxxxxxxxxx> wrote:

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Document: draft-ietf-netconf-restconf-15
Reviewer: Robert Sparks
Review Date: 28Jul2016
IETF LC End Date: 3Aug2016
IESG Telechat date: not yet scheduled

Summary:

Major issues:

* I am not finding any discussion in the Security Considerations or in the text around what a server's options are if a client is asking it to keep more state than it is willing or capable of holding. The possible values of the "depth" query parameter (particularly "unbounded") points out that a misconfigured or compromised client might start creating arbitrarily deep trees. Should a server have the ability to say no?

I guess we need more text somewhere explaining the "depth" parameter is

a retrieval filter. 

I got that. It's existence, however, caused me to think about the fact that what is stored at the server can be arbitrarily deep. Clients using POST can build trees that are arbitrarily deep, with bits at the node that are arbitrarily large (subject to the constraints the YANG models put on the node). There should be some discussion acknowledging that this can happen, and discussion of what the server can do if some client starts asking it to store more than it is willing to store.

It is not used to create anything in the server.

The server does not maintain any state except during the processing of

the retrieval request

 

* The third paragraph of 3.7 paraphrases to "SHOULD NOT delete more than one instance unless a proprietary query parameter says it's ok". This isn't really helpful in a specification. Proprietary things are proprietary. The SHOULD NOT already allows proprietary things to do something different without trainwrecking the protocol. Please just delete the 2nd and 3rd sentence from the paragraph.

OK

 

* Section 2.3 says "If X.509 certificate path validation fails and the presented X.509 certificate does not match a locally configured certificate fingerprint, the connection MUST be terminated as defined in [RFC5246]." RFC5246 doesn't really talk about certificate validation, and it certainly doesn't say "the connection MUST be terminated" when certificates fail to validate. What are you trying to point to in RFC5246 here? Should you be pointing somewhere else? (It's perfectly reasonable for the document to reference RFC5246, and it does so elsewhere without problem).

Please suggest replacement text if we are citing the wrong RFC.

I will ask Kent to look into this issue

 

Minor issues:

* "A server MUST support XML or JSON encoding." is ambiguous. (2nd paragraph of 5.2). Did you mean the server MUST support at least one of XML or JSON but not necessarily both? I think you really intended that the server support BOTH types of encoding.

No -- it will be clarified that the server must support at least 1 of the 2

 

* I _think_ I can infer that PUT can't be used with datastore resources. Section 3.4 only speaks of POST and PATCH. Section 4.5 speaks about "target data resource" and is silent about datastore resources. If I've understood the intent, please be explicit about datastore resources in 4.5. If I've misunderstood then more clarity is needed in both 3.4 and 4.5.

The  next draft will be clarified to allow PUT on a datastore resource

Hrmm - that makes me less comfortable that you are actually aligned with 7231. It may just be that you need to be more precise with your description, but per 7231, PUT never creates resources - it can create or replace the state of a resource.

 

* In 3.5.3.1 you restrict identifiers with "MUST NOT start with 'xml' (or any case variant of that string). Please call out why (or point to an existing document that explains why).

OK

 

* The text in 5.3 about access control interacting with caching (added based on my early review I think) doesn't mesh well with paragraph 3 of section 5.5. There you tell the client to use Etag and Last-Modified, but in 5.3 you say it won't work reliably when access permissions change. At the very least 5.5 should point back into the paragraph in 5.3.

Nits/editorial comments:

* Introduction, 4th paragraph - please change "MAY provide" to "provides". Section 3.6 explains the cases where there is choice in what to provide.


* Section 2.3 paragraphs 1 and 2. There is edit-itis here left (I suspect) from working in matching fingerprints. Consider combining and simplifying these two paragraphs after improving the reference issue called out above.

* Section 4 says "Access control mechanisms MUST be used to limit..." This is not a good use of a 2119 MUST. I suggest replacing "MUST be" with "are". The subsequent text already captures the actual normative requirements on the server.

* Section 12 says "this protocol SHOULD be implemented carefully". That is not a good use of a 2119 SHOULD. It is not a protocol requirement. I suggest reformulating this into something like "There are many patterns of attack that have been observed through operational practice with existing management interfaces. It would be wise for implementers to research them, and take them into account when implementing this protocol." It would be far better to provide a pointer to where the implementer should start this research.

* (micronit) Lots of examples are internally inconsistent wrt dates. For instance, look at the 200 OK in section 3.3.3 - it says that back in 2012, a server returned something talking about a library versioned in 2016.

Andy