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

John Scudder via Datatracker <noreply@ietf.org> Tue, 04 May 2021 20:02 UTC

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Subject: [dns-privacy] John Scudder's No Objection on draft-ietf-dprive-xfr-over-tls-11: (with COMMENT)
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John Scudder has entered the following ballot position for
draft-ietf-dprive-xfr-over-tls-11: No Objection

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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


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-

      *  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


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

I do not see anything relevant below.