Re: [TLS] [dns-privacy] Martin Duke's No Objection on draft-ietf-dprive-xfr-over-tls-11: (with COMMENT)

Sara Dickinson <> Thu, 29 April 2021 12:51 UTC

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From: Sara Dickinson <>
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Date: Thu, 29 Apr 2021 13:51:29 +0100
Cc: DNS Privacy Working Group <>,
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To: Martin Thomson <>
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Subject: Re: [TLS] [dns-privacy] Martin Duke's No Objection on draft-ietf-dprive-xfr-over-tls-11: (with COMMENT)
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> On 29 Apr 2021, at 01:09, Martin Thomson <> wrote:
> On Wed, Apr 28, 2021, at 20:27, Sara Dickinson wrote:
>> An early version of this specification proposed a XoT specific ALPN in 
>> order to distinguish this from a connection intended to perform 
>> recursive to authoritative DoT (often called ADoT). ADoT is not yet 
>> specified, but is the subject of ongoing discussions in DPRIVE. The 
>> working group rejected this idea for XoT and switched to the current 
>> spec which does not use an ALPN at all. 
> No new protocol should use TLS without ALPN.  It only opens space for cross-protocol attacks.  Did the working group consider this possibility in their discussions?

What the working group asked for following the ALPN discussion was that the document contain a description of the options an authoritative nameserver that supports XoT can use to manage TLS connections and the queries received on those connections  - that is provided in Appendix A:

As more context, the document also covers various existing mechanisms that can be used to manage zone transfers (including IP ACLs and TSIG) and how they combine with Strict and Mutual TLS authentication. The document specifies that the server MUST use either an IP ACL or mTLS to authenticate the XoT client.