Subject: [dns-privacy] John Scudder's No Objection on draft-ietf-dprive-xfr-over-tls-11: (with COMMENT)

From: John Scudder via Datatracker <[email-masked]>
Date: Tue, 04 May 2021 13:02:56 -0700

John Scudder has entered the following ballot position for
draft-ietf-dprive-xfr-over-tls-11: No Objection

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COMMENT:
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Thanks for the well-written and easy to follow spec. Below are some comments
you may want to take into consideration.

1. Abstract

   XFR-over-TLS (XoT).  Additionally, this specification updates
   RFC1995, RFC5936 and RFC7766.

Please say a few words about how the spec updates those RFCs, don’t make the
reader go digging for it.

2. Section 1

   transfers (this draft) is orthogonal to preventing zone enumeration,
   though they aim to protect the same information.

s/this draft/this document/

3. Sections 6.1, 6.2

   3.  If the primary serial is higher than the secondaries serial

s/secondaries/secondary’s/

4. Section 6.3

   This section attempts to presents a rationale for considering

“Attempts to present”. But really, why not just “presents”?

5. Section 6.3

   Since the SOA of the published zone can be trivially discovered by
   simply querying the publicly available authoritative servers leakage

Comma between “servers” and “leakage”.

6. Section 6.3.2

   For hidden primaries or secondaries the SOA response leaks only the
   degree of SOA serial number lag of any downstream secondary.

I don’t understand. This either means the sentence would make sense if only I
had the right domain knowledge (which is OK then), or it means the sentence
doesn’t make sense (which isn’t).

7. Section 7

   The following sections include detailed clarifications on the updates
   to XFR behavior implied in [RFC7766] and how the use of [RFC7828]
   applies specifically to XFR exchanges.  It also discusses how IXFR
   and AXFR can reuse the same TCP connection.

“They also discuss” — agreement in number with “the following sections”.

8. Section 7.4

   This specification for XoT updates the guidance in [RFC7766] to
   provide the same separation of connection purpose (regular queries
   and zone transfers) for all transports being used on top of TCP.

The “for XoT” confuses this sentence, making it sound a bit like the advice is
restricted to XoT. I think those two words should be struck, it would be just
fine as “this specification updates…”

9. Section 8.1

   For improved security all implementations of this specification MUST
   use only TLS 1.3 [RFC8446] or later.

Improved compared to what? I think the first three words could go, then the
question wouldn’t come up.

9. Section 8.4 (also 10.4)

   o  the server MUST validate the client is authorized to request or
      proxy a zone transfer by using one or both of the following:

      *  an IP based ACL (which can be either per-message or per-
         connection)

      *  Mutual TLS (mTLS)

The former is weaker, surely? I see Martin also raised this in his comments, I
agree with what he wrote. It’s odd to see these two authorization methods, with
very different security properties, presented as equivalent with no discussion
anywhere of their relative (de)merits.

10. Section 8.8.1 (also 8.9.3)

   The goal of padding AXoT responses would be two fold:

“Is”, not “would be” (also 893)

11. Section 10.2

   SIG(0) [RFC2931] similarly also provides a mechanism to digitally

Similarly, or also — pick one.

12. Section 11

   The XoT authentication requirement specified in Section 8.4 addresses
   the issue of ensuring that the transfers is encrypted between the two

“Transfers are” or “transfer is”.

13. Section 11

   endpoints directly involved in the current transfers.  The following
   table summarized the properties of a selection of the mechanisms

“Summarizes”

14. Appendix A

   For completeness, it is noted that an earlier version of the
   specification suggested using a XoT specific ALPN to negotiate TLS

Please define APLN on first use

15. A.4

   As an aside, whilst [RFC7766] makes a general purpose distinction to
   clients in the usage of connections (between regular queries and zone

Do you mean “general purpose distinction between clients“? The use of “to”
doesn’t make sense to me.

16. A.4

   Client behavior to REFUSED response is not clearly defined (see
   below).

I do not see anything relevant below.

---

From: Sara Dickinson <[email-masked]>
Date: Thu, 6 May 2021 11:13:15 +0100

> On 4 May 2021, at 21:02, John Scudder via Datatracker <[email-masked]> wrote:
> 

Propose: 
 "Additionally, this specification updates RFC1995 and RFC5936 with respect to efficient use of TCP connections, and RFC7766 with respect to the recommended number of connections between a client and server for each transport.

> Comma between “servers” and “leakage”.

Ack to all the above corrections.

> doesn’t make sense (which isn’t).

Probably better written as:

“For hidden XFR servers (either primaries of secondaries) an SOA response directly from that server only additionally leaks the degree of SOA serial number lag of any downstream secondary of that server.”

Does that help?

> fine as “this specification updates…”

Ack to both. 

> question wouldn’t come up.

Ah - compared to stub to recursive DoT which was specified in 2015 and only required to use TLS 1.2 or later….but I’ll update as suggested

> anywhere of their relative (de)merits.

Please see the thread in response to Ben’s DISCUSS on this. 

> Please define APLN on first use

Yup to all the above. 

> doesn’t make sense to me.

The advice referred to is advice for clients about how many connections they should open. Suggest:

“makes a general purpose distinction in the advice to clients about their usage of connections"

> I do not see anything relevant below.

Good catch - this text used to be in the body of the document. It should reference section 8.7.

Thanks and regards

Sara.

---

From: John Scudder <[email-masked]>
Date: Thu, 6 May 2021 20:03:52 +0000

Hi Sara,

Thanks for your prompt reply. In short: that all sounds good. I’ll move further discussion, if any, of point 9 (IP ACLs) to Ben’s thread.

Regards,

—John

On May 6, 2021, at 6:13 AM, Sara Dickinson <[email-masked]<mailto:[email-masked]>> wrote:

On 4 May 2021, at 21:02, John Scudder via Datatracker <[email-masked]<mailto:[email-masked]>> wrote:

Please refer to https://urldefense.com/v3/__https://www.ietf.org/iesg/statement/discuss-criteria.html__;!!NEt6yMaO-gk!RSdMPZScekk0Bl8Y_uEy97Zb7mgbnIzs_Eyz8fNRTHPux5ABrf-whrGWP5iqug$
for more information about DISCUSS and COMMENT positions.

The document, along with other ballot positions, can be found here:
https://urldefense.com/v3/__https://datatracker.ietf.org/doc/draft-ietf-dprive-xfr-over-tls/__;!!NEt6yMaO-gk!RSdMPZScekk0Bl8Y_uEy97Zb7mgbnIzs_Eyz8fNRTHPux5ABrf-whrGzhqb-PA$

1. Abstract

Propose:

2. Section 1

3. Sections 6.1, 6.2

4. Section 6.3

5. Section 6.3

6. Section 6.3.2

Does that help?

7. Section 7

8. Section 7.4

Ack to both.

9. Section 8.1

    *  Mutual TLS (mTLS)

11. Section 10.2

12. Section 11

13. Section 11

“Summarizes”

14. Appendix A

Yup to all the above.

15. A.4

16. A.4

Thanks and regards

Sara.