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Versions: 00 01 02 03 04                                                
Network Working Group                                         B. Dickson
Internet-Draft                                                   GoDaddy
Intended status: Informational                         20 September 2021
Expires: 24 March 2022


          Authenticated DNS over TLS to Authoritative Servers
                   draft-dickson-dprive-adot-auth-04

Abstract

   This Internet Draft proposes a mechanism for DNS resolvers to
   discover support for TLS transport to authoritative DNS servers, to
   validate this indication of support, and to authenticate the TLS
   certificates involved.

   This requires that the name server _names_ are in a DNSSEC signed
   zone.

   This also requires that the delegation of the zone served is
   protected by [I-D.dickson-dnsop-ds-hack], since the NS names are the
   keys used for discovery of TLS transport support.

   Additional recommendations relate to use of various techniques for
   efficiency and scalability, and new EDNS options to minimize round
   trips and for signaling between clients and resolvers.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on 24 March 2022.

Copyright Notice

   Copyright (c) 2021 IETF Trust and the persons identified as the
   document authors.  All rights reserved.



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   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents (https://trustee.ietf.org/
   license-info) in effect on the date of publication of this document.
   Please review these documents carefully, as they describe your rights
   and restrictions with respect to this document.  Code Components
   extracted from this document must include Simplified BSD License text
   as described in Section 4.e of the Trust Legal Provisions and are
   provided without warranty as described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Conventions and Definitions . . . . . . . . . . . . . . . . .   3
   3.  Background  . . . . . . . . . . . . . . . . . . . . . . . . .   3
   4.  Purpose . . . . . . . . . . . . . . . . . . . . . . . . . . .   3
     4.1.  New DNS Elements  . . . . . . . . . . . . . . . . . . . .   4
   5.  Requirements, and Limitations . . . . . . . . . . . . . . . .   4
   6.  DNS Records To Publish for ADoT . . . . . . . . . . . . . . .   5
     6.1.  Server DNS Transport Support Signaling  . . . . . . . . .   5
       6.1.1.  Prerequisite: New SVCB Binding for DNS and DoT  . . .   6
       6.1.2.  Examples  . . . . . . . . . . . . . . . . . . . . . .   7
     6.2.  DANE TLSA Records for ADoT  . . . . . . . . . . . . . . .   7
       6.2.1.  Example . . . . . . . . . . . . . . . . . . . . . . .   7
     6.3.  Signaling DNS Transport for a Name Server . . . . . . . .   8
       6.3.1.  Examples  . . . . . . . . . . . . . . . . . . . . . .   8
     6.4.  Signaling DNS Transport for a Domain  . . . . . . . . . .   9
       6.4.1.  Examples  . . . . . . . . . . . . . . . . . . . . . .   9
   7.  Validation Using DS Records, DNS Records, TLSA Records, and
           DNSSEC Validation . . . . . . . . . . . . . . . . . . . .   9
     7.1.  Complete Example  . . . . . . . . . . . . . . . . . . . .  10
       7.1.1.  DNS Record Data . . . . . . . . . . . . . . . . . . .  10
       7.1.2.  Discussion Point - Wildcard-like Records  . . . . . .  12
       7.1.3.  Resolver Iterative Queries For Final TLS Query  . . .  13
   8.  Signaling Resolver Support and Client Desire for ADoT . . . .  16
     8.1.  Server Side Support Signaling . . . . . . . . . . . . . .  16
     8.2.  Client Side Desire Signaling  . . . . . . . . . . . . . .  16
   9.  Security Considerations . . . . . . . . . . . . . . . . . . .  16
   10. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  17
   11. Normative References  . . . . . . . . . . . . . . . . . . . .  17
   12. Informative References  . . . . . . . . . . . . . . . . . . .  17
   Appendix A.  Acknowledgments  . . . . . . . . . . . . . . . . . .  18
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  18









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1.  Introduction

   The Domain Name System (DNS) predates any concerns over privacy,
   including the possibility of pervasive surveillance.  The original
   transports for DNS were UDP and TCP, unencrypted.  Additionally, DNS
   did not originally have any form of data integrity protection,
   including against active on-path attackers.

   DNSSEC (DNS Security extensions) added data integrity protection, but
   did not address privacy concerns.  The original DNS over TLS
   [RFC7858] and DNS over HTTPS [RFC8484] specifications were limited to
   client-to-resolver traffic.

   The remaining privacy component is recursive-to-authoritative
   servers.  This Internet Draft is designed to provide a solution to
   this problem.

2.  Conventions and Definitions

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

3.  Background

   The result is that the parental side of the zone cut has records
   needed for DNS resolution which are not signed and not validatable.

4.  Purpose

   Authoritative DNS over TLS is intended to provide the following for
   communications from recursive resolvers to authoritative servers:

   *  Enable discovery of support for ADoT

   *  Validate the name server name

   *  Validate the server's TLS certificate

   *  Provide channel security using TLS









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4.1.  New DNS Elements

   The following are new protocol components, which are either included
   in this document, or are in other documents.  Some are strictly
   required, while others are strongly suggested components to allow
   better scalability and performance.  Some of the new elements are
   aliases to already documented standards, for purposes of these
   improvements.

   +=======+============+=======+========+=============================+
   |Element| New/Alias/ |Format/|Required|Description                  |
   |       | OPT        |Base   |        |                             |
   +=======+============+=======+========+=============================+
   |DNST   | Alias      |SVCB   |Spec: Y |DNS Transport - support for  |
   |       |            |       |DNS: N  |DoT                          |
   +-------+------------+-------+--------+-----------------------------+
   |TLSADOT| Alias      |TLSA   |Spec:   |TLSA without prefixing       |
   |       |            |       |Opt DNS:|                             |
   |       |            |       |Yes or  |                             |
   |       |            |       |TLSA    |                             |
   +-------+------------+-------+--------+-----------------------------+
   |ADOTD  | New        |OPT RR |N       |Signal desire for ADOT       |
   |       |            |       |        |(client-resolver)            |
   +-------+------------+-------+--------+-----------------------------+
   |ADOTA  | New        |OPT RR |N       |Signal availablity of ADOT   |
   |       |            |       |        |(resolver-client)            |
   +-------+------------+-------+--------+-----------------------------+
   |NSECD  | New        |OPT RR |N       |Signal desire for NSEC(3) for|
   |       |            |       |        |[RFC8198]                    |
   +-------+------------+-------+--------+-----------------------------+
   |NSV    | New        |DNSKEY |Y       |Protect NS - see             |
   |       |            |Alg    |        |[I-D.dickson-dnsop-ds-hack]  |
   +-------+------------+-------+--------+-----------------------------+

                                  Table 1

5.  Requirements, and Limitations

   This protocol depends on correct configuration and operation of the
   respective components, and that those are maintained according to
   Best Current Practices:

   *  Use of DS records [I-D.dickson-dnsop-ds-hack] for the protection
      of the delegation to the authoritative name servers

   *  Use of "glueless" zone(s) for name server names' zone
      [I-D.dickson-dnsop-glueless]




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   *  DNSSEC signing of the zone serving the authoritative name servers'
      names [@RFC4034;@RFC4035;RFC5155]

   *  Proper management of key signing material for DNSSEC

   *  Ongoing management of RRSIGs on a timely basis (avoiding RRSIG
      expiry)

   *  Ensuring TLSA records are kept synchronized with the TLS
      certificates used

   *  Proper management of TLS private keys for TLS certificates used

   There are external dependencies that impact the system security of
   any DNSSEC zone, which are inherently unavoidable in establishing
   this scheme.  Specifially, the original DS record enrollment and any
   updates to the DS records involved in DNSSEC delegations are presumed
   secure and outside of the scope of the DNS protocol per se.

   Other risks relate to normal information security practices,
   including access controls, role based access, audits, multi-factor
   authentication, multi-party controls, etc.  These are out of scope
   for this protocol itself.

6.  DNS Records To Publish for ADoT

   ADoT is a property of DNS servers.  The signaling is done at the
   server level, using a DNS record with the same owner name as the
   server itself (i.e. where the A and AAAA records for the server are
   published).

6.1.  Server DNS Transport Support Signaling

   In order to support ADoT for a DNS server, it is necessary to publish
   a record specifyig explicit DoT support.  This record also indicates
   other supported transports for the DNS server, e.g. the standard
   ports (TCP and UDP port 53).

   The record type is "DNST" (DNS Transport), which is a specific
   instance of (aka binding for) SVCB with unique RRTYPE.

   The zone serving the record MUST be DNSSEC signed.  The absence of
   the DNST RRTYPE is proved by the NSEC(3) record, or else the DNST
   RRTYPE plus RRSIG is returned in response to a query for this record
   if it exists.






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6.1.1.  Prerequisite: New SVCB Binding for DNS and DoT

   (NB: To be separated out into its own draft and expanded fully.)
   This SVCB binding will be given the RRTYPE value {TBD} with mnemonic
   name DNST ("DNS Transport").  Like any SVCB binding, there is a
   mandatory TargetName (which will normally be ".", indicating the
   target is the same as the record owner name).  The default binding is
   the standard DNS ports, UDP/53 and TCP/53.

   The SVCB binding includes support for an optional ADoT port, which is
   the standard DoT port TCP/853.  This is signaled by "alpn=dot".  The
   actual port number may be overridden with the "DOTport=N" SvcParam,
   and the UDP and TCP ports may also be overridden with optional
   "UDPport=N" and "TCPport=N" SvcParams.

   Since DNST is a type-specific binding, it does NOT require the
   underscore prefix naming that the generic SVCB RRTYPE requires.  It
   may occur anywhere, including at the apex of a DNS zone, and may co-
   exist with any other type that also permits other types.o

   The DNST binding allows both AliasMode and ServiceMode record types
   (per the proposed SVCB standard).  Both mode types use a TargetName
   parameter, which supports same-name usage (TargetName = ".") as well
   as redirected TargetName values.  The resolver must follow AliasMode
   in the same manner as CNAME, i.e. rewriting the QNAME and restarting
   resolution using the new QNAME.

   Once the DNST is in ServiceMode, the authoritative server returns
   both the DNST record(s) and A and AAAA records with the same owner
   name (TargetName).  This reduces the number of queries the resolver
   would otherwise have to make (i.e. two additional queries for A and
   AAAA record types).

6.1.1.1.  Default Ports for DNS

   This scheme uses an SVCB binding for DNS Transport, DNST.  The
   binding has default ports UDP/53 and TCP/53 as the default-alpn.
   These are assumed unless "no-default-alpn" is added as an optional
   SvcParam.

6.1.1.2.  Optional Port for DoT

   The DNST binding uses the defined ALPN for DNS-over-TLS with the
   assigned label "dot".  Use of ADoT is signaled if and only if the the
   SvcParam of "alpn=dot" is present.






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6.1.2.  Examples

   Suppose the name server ns1.example.net supports only the normal DNS
   ports, and the name server ns2.example.net supports both the normal
   ports and ADoT.  The zone example.net would include the records:

       ns1.example.net. IN DNST 1 "."
       ns2.example.net. IN DNST 1 "." alpn=dot

   And similarly, if another zone with many name server names wanted to
   have a policy of all-ADoT support (i.e. every name server supports
   ADoT), they would each be encoded as:

       ns1.example2.net DNST 1 "." alpn=dot
       ns2.example2.net DNST 1 "." alpn=dot
       ns3.example2.net DNST 1 "." alpn=dot
       ns4.example2.net DNST 1 "." alpn=dot

   In each case, the first parameter is the SvcPriority, which must be
   non-zero (zero indicates AliasMode SVCB record type).

   Note that it is possible for the resolver to use alter or ignore
   SvcPriority based on its own local policy.  For instance, a resolver
   to prefer non-DoT over DoT or vice versa.  Local policy might be to
   override SvcPriority ordering, and/or ignore some of the records.
   For example, a resolver might prefer to support mandatory use of DoT
   if present on any server in the NS RRset.

6.2.  DANE TLSA Records for ADoT

   The presence of ADoT requires additionally that a TLSA [RFC6698]
   record be provided.  A new RRTYPE is to be created for this as an
   alias of TLSA, with mnemonic of "TLSADOT" (TLS ADOT Certificate).
   This record will be published at the location NS_NAME, where NS_NAME
   is the name of the name server.  Any valid TLSA RDATA is permitted.
   The use of Certificate Usage types PKIX-TA and PKIX-EE is NOT
   RECOMMENDED since PKIX requires web PKI interactions.  DANE types
   only require DNSSEC support.  The use of Certificate Usage types
   DANE-TA records may provide more flexibility in provisioning and
   validation.  Per [RFC7218][RFC7671] the RECOMMENDED Selector and
   Matching types for this are SPKI and SHA2-256, giving the recommended
   TLSA record type of DANE-TA SPKI SHA2-256.

6.2.1.  Example

   In the above example, ns2.example.net supports DNS over TLS, and thus
   would need to have a TLSA record.  The zone would include:




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       ns2.example.net. IN TLSADOT DANE-TA SPKI SHA2-256 (hash data)

   If there were another zone containing many DNS server names,
   example2.net, it would be relatively simple to replicate otherwise
   identical records which use the same signing cert (rather than end-
   entity cert) in the TLSADOT record.

   This would look like the following:

       ns1.example2.net IN TLSADOT DANE-TA SPKI SHA2-256 (hash data)
       ns2.example2.net IN TLSADOT DANE-TA SPKI SHA2-256 (hash data)
       ns3.example2.net IN TLSADOT DANE-TA SPKI SHA2-256 (hash data)
       ns4.example2.net IN TLSADOT DANE-TA SPKI SHA2-256 (hash data)
       ns1.example2.net IN A IP4_ADDRESS1
       ns2.example2.net IN A IP4_ADDRESS2
       ns3.example2.net IN A IP4_ADDRESS3
       ns4.example2.net IN A IP4_ADDRESS4
       ns1.example2.net IN AAAA IP6_ADDRESS1
       ns2.example2.net IN AAAA IP6_ADDRESS2
       ns3.example2.net IN AAAA IP6_ADDRESS3
       ns4.example2.net IN AAAA IP6_ADDRESS4

6.3.  Signaling DNS Transport for a Name Server

   This transport signaling MUST only be trusted if the name server
   names for the domain containing the relevant name servers' names are
   protected with [I-D.dickson-dnsop-ds-hack] and validated.  The name
   servers must also be in a DNSSEC signed zone (i.e. securely delegated
   where the delegation has been successfully DNSSEC validated).

   The specific DNS transport that a name server supports is indicated
   via use of an RRSet of RRTYPE "DNST".  This is a SVCB binding, and
   normally will use the TargetName of "." (meaning the same name).  The
   default ALPN (transport mechanisms) are TCP/53 and UDP/53.  The ADoT
   transport support is signaled by "alpn=dot".  There is an existing
   entry for "dot" in the ALPN table, with port TCP/853.

6.3.1.  Examples

   We re-use the same examples from above, indicating whether or not
   individual authoritative name servers support DoT:

       ns1.example.net. IN DNST 1 "."
       ns2.example.net. IN DNST 1 "." alpn=dot

   And similarly, if another zone with many name server names wanted to
   have a policy of all-ADoT support (i.e. every name server supports
   ADoT), this could be encoded as:



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       ns1.example2.net DNST 1 "." alpn=dot
       ns2.example2.net DNST 1 "." alpn=dot
       ns3.example2.net DNST 1 "." alpn=dot
       ns4.example2.net DNST 1 "." alpn=dot

6.4.  Signaling DNS Transport for a Domain

   A domain inherits the signaled transport for the name servers serving
   the domain.

   This transport signaling MUST only be trusted for use of ADoT if the
   delegated name server names for the domain are protected with
   [I-D.dickson-dnsop-ds-hack].

   The delegation to NS names "A" and "B", along with the DS record
   protecting/encoding "A" and "B", results in the DNS transport that is
   signaled for "A" and "B" being applied to the domain being delegated.
   This transport will include ADoT IFF the transport for "A" and "B"
   has included ADoT via DNS records.

6.4.1.  Examples

   No additional configuration is needed, beyond use of authority
   servers which signal DoT support.  The following examples assumes the
   previous DNS records are provisioned:

       example.com NS ns1.example.net. // does not support ADoT
       example.com NS ns2.example.net. // supports ADoT

       example2.com NS ns1.example2.net. // all support ADoT
       example2.com NS ns2.example2.net. // all support ADoT

   In this example, ns1 does not have ADoT support (since the DNS record
   excludes the "alpn=dot" parameter), while ns2 does support ADoT
   (since it includes "alpn=dot").

7.  Validation Using DS Records, DNS Records, TLSA Records, and DNSSEC
    Validation

   These records are used to validate corresponding delegation records,
   DNS records, and TLSA records, as follows:

   *  Initial domain NS records are validated using
      [I-D.dickson-dnsop-ds-hack]

   *  All DS records implementing [I-D.dickson-dnsop-ds-hack] must be
      DNSSEC validated prior to use




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   *  Once the NS names have been validated, and the delegations to the
      appropriate name servers are validated, the DNS records for the NS
      name are obtained to identify the DNS transport methods supported.

   *  If ADoT is among the supported transports, the TLSA record for the
      name server is obtained, and used for verification of the TLS
      certificate when making the TLS connection.

7.1.  Complete Example

7.1.1.  DNS Record Data

   Suppose a client requests resolution for the IP address of
   "sensitive-name.example.com".  Suppose the client's resolver has a
   "cold" cache without any entries beyond the standard Root Zone and
   relevant TLD name server records.

   Suppose the following entries are present at their respective TLD
   authority servers, delegating to the respective authority servers:

       // (Single NS for brevity only, please use 2 NS minimum )
       // Unsigned delegations to various single-operator servers
       example2.com NS ns1.example2.net. // all support ADoT
       example3.com NS ns2.example2.net. // all support ADoT
       example4.com NS ns3.example2.net. // all support ADoT
       example5.com NS ns4.example2.net. // all support ADoT

       // Zone serving NS data for single-operator's servers
       example2.net NS ns1.infra2.example
       example2.net NS ns2.infra2.example
       example2.net DS (DS record data)
       // glueless name servers are used

       // Special zone serving NS data for previous zone
       infra2.example NS ns1-glue.infra2.example
       infra2.example NS ns2-glue.infra2.example
       infra2.example DS (DS record data)
       // Note use of glue for only this zone's delegation
       ns1-glue.infra2.example A (glue A data)
       ns1-glue.infra2.example AAAA (glue AAAA data)
       ns2-glue.infra2.example A (glue A data)
       ns2-glue.infra2.example AAAA (glue AAAA data)

   Suppose the following additional entries are in the respective
   authority servers for the ADOT signaling/certs:






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       example2.net SOA ( SOA record data )
       // glueless name servers are used
       example2.net NS ns1.infra2.example
       example2.net NS ns2.infra2.example
       //
       // SVCB records (DNS Transport) for discovery of support
       ns1.example2.net DNST 1 "." alpn=dot
       ns2.example2.net DNST 1 "." alpn=dot
       ns3.example2.net DNST 1 "." alpn=dot
       ns4.example2.net DNST 1 "." alpn=dot
       //
       // ADOT TLSA signing cert
       ns1.example2.net IN TLSADOT DANE-TA SPKI SHA2-256 (hash data)
       ns2.example2.net IN TLSADOT DANE-TA SPKI SHA2-256 (hash data)
       ns3.example2.net IN TLSADOT DANE-TA SPKI SHA2-256 (hash data)
       ns4.example2.net IN TLSADOT DANE-TA SPKI SHA2-256 (hash data)
       //
       // Addresses of name servers serving customer zones
       // E.g. example2.com to example5.com served on these
       ns1.example2.net IN A IP4_ADDRESS1
       ns2.example2.net IN A IP4_ADDRESS2
       ns3.example2.net IN A IP4_ADDRESS3
       ns4.example2.net IN A IP4_ADDRESS4
       ns1.example2.net IN AAAA IP6_ADDRESS1
       ns2.example2.net IN AAAA IP6_ADDRESS2
       ns3.example2.net IN AAAA IP6_ADDRESS3
       ns4.example2.net IN AAAA IP6_ADDRESS4
       //
       // plus RRSIGs and NSEC(3) records and their RRSIGs

       infra2.example SOA ( SOA record data )
       infra2.example NS ns1-glue.infra2.example
       infra2.example NS ns2-glue.infra2.example
       ns1-glue.infra2.example A (same as glue A data)
       ns1-glue.infra2.example AAAA (same as glue AAAA data)
       ns2-glue.infra2.example A (same as glue A data)
       ns2-glue.infra2.example AAAA (same as glue AAAA data)
       //
       //  name server info for example2.net zone
       ns1.infra2.example A (glueless A data)
       ns1.infra2.example AAAA (glueless AAAA data)
       ns2.infra2.example A (glueless A data)
       ns2.infra2.example AAAA (glueless AAAA data)
       //
       // plus RRSIGs and NSEC(3) records and their RRSIGs






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7.1.2.  Discussion Point - Wildcard-like Records

   Wildcards records have RRTYPE(s), but are only instantiated when an
   owner name does not exist.

   If wildcards were instantiated whenever the 3-tuple (name, class,
   type) did not exist, use of wildcard records for DNST and TLSADOT
   would be a logical choice.

   The discussion point is as follows:

   *  Would it make sense to support a wildcard-like behavior for
      covering many owner names which did not have explicit DNST and/or
      TLSADOT records of their own?

   *  If so, when/how would that be signalled?

      -  It could be explicit, using a separate RRTYPE to flag the need
         to use the parent name (zone apex) for the required RRTYPE.

         o  This would support use of NSEC(3) records to check for the
            flag

         o  A resolver could use the flag to optimize cache usage for
            the parent record.  Once the parent is in the cache, the
            flag in the NSEC(3) for the owner name would trigger use of
            the cached parent record.

      -  It could be implicit, meaning the absence of the explicit
         record type results in the need to search for the record type
         at another name (e.g. zone apex).

         o  The lack of explicit record could be detected from NSEC(3)
            records

         o  The implicit flag would be handled the same as the explicit
            flag case above.

   *  The TLSADOT record at the parent zone would only be viable for
      DANE-TA type.

   *  The DNST record at the parent zone would need to inherit the
      original owner name for use by TargetName = "." semantics.








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7.1.3.  Resolver Iterative Queries For Final TLS Query

   (In the following, use of wildcard-type records and semantics is
   assumed, but not explictly described currently.  Literal wildcard
   record labels ("*") are used as a placeholder, pending the above
   Discussion Point's resolution.)

   The following are the necessary queries to various servers necessary
   to do a private TLS-protected lookup.

   Several examples are provided in order, from a presumed cold cache
   state.  Root Priming and TLD queries are presumed to already have
   been complete.

   1.  Query for sensitive-name.example2.com:

       1.  Query for NS for example2.com => get NS ns1.example2.net plus
           DS => validate the DS and proceed

       2.  Query for NS for example2.net => get NS ns1/
           ns2.infra2.example plus DS => validate the DS and proceed

       3.  Query for NS for infra2.example2.net => get NS ns1-glue/
           ns2-glue.infra2.example plus DS plus glue A/AAAA => validate
           the DS and proceed

       4.  Query with NSECD for A for ns1/ns2.infra2.example => get A
           for ns1/ns2.infra2.example plus RRSIGs plus NSEC(3) plus
           RRSIG => validate the RRSIGs and proceed

       5.  Query with NSECD for A for ns1.example2.net => get A for
           ns1.example2.net plus RRSIG plus NSEC(3) plus RRSIG =>
           validate the RRSIGs and proceed

       6.  Query with NSECD for DNST for ns1.example2.net => get DNST
           for *.example2.net plus RRSIG plus special wildcard NSEC(3)s
           plus RRSIGs => validate the RRSIGs and proceed

       7.  Query with NSECD for TLSADOT for ns1.example2.net => get
           TLSADOT for *.example2.net plus RRSIG plus special wildcard
           NSEC(3)s plus RRSIGs => validate the RRSIGs and proceed

       8.  Query over TLS for sensitive-name.example2.com (to
           ns1.example2.net, match TLS cert chain against DANE-TA cert,
           only query once TLS established)

   2.  Query for sensitive-name.example3.com:




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       1.  Query for NS for example2.com => get NS ns1.example2.net plus
           DS => validate the DS and proceed

       2.  Query with NSECD for A for ns1.example2.net => get A for
           ns1.example2.net plus RRSIG plus NSEC(3) plus RRSIG =>
           validate the RRSIGs and proceed

       3.  NB: already have wildcards for DNST and TLSADOT plus NSEC3
           proving no non-wildcards exist for ns1.example2.net for those
           types, synthesize DNST and TLSADOT records)

       4.  Query over TLS for sensitive-name.example2.com (to
           ns1.example2.net, match TLS cert chain against DANE-TA cert,
           only query once TLS established)

   3.  Query for sensitive-name.example4.com:

       1.  Query for NS for example2.com => get NS ns1.example2.net plus
           DS => validate the DS and proceed

       2.  Query with NSECD for A for ns1.example2.net => get A for
           ns1.example2.net plus RRSIG plus NSEC(3) plus RRSIG =>
           validate the RRSIGs and proceed

       3.  NB: already have wildcards for DNST and TLSADOT plus NSEC3
           proving no non-wildcards exist for ns1.example2.net for those
           types, synthesize DNST and TLSADOT records)

       4.  Query over TLS for sensitive-name.example2.com (to
           ns1.example2.net, match TLS cert chain against DANE-TA cert,
           only query once TLS established)

   4.  Query for sensitive-name.example5.com:

       1.  Query for NS for example2.com => get NS ns1.example2.net plus
           DS => validate the DS and proceed

       2.  Query with NSECD for A for ns1.example2.net => get A for
           ns1.example2.net plus RRSIG plus NSEC(3) plus RRSIG =>
           validate the RRSIGs and proceed

       3.  NB: already have wildcards for DNST and TLSADOT plus NSEC3
           proving no non-wildcards exist for ns1.example2.net for those
           types, synthesize DNST and TLSADOT records)

       4.  Query over TLS for sensitive-name.example2.com (to
           ns1.example2.net, match TLS cert chain against DANE-TA cert,
           only query once TLS established)



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   5.  Query for sensitive-name2.example2.com:

       1.  (Already have delegation entry for example2.com in cache.)

       2.  (Already have A for ns1.example2.net in cache.)

       3.  (Already have all TLS info in the cache.)

       4.  Query over TLS for sensitive-name.example2.com (to
           ns1.example2.net, match TLS cert chain against DANE-TA cert,
           only query once TLS established)

   Once the initial query or queries for a name server zone has been
   done, if that zone uses wildcards for DNST and TLSADOT, the only
   queries needed for a new name server are the A and/or AAAA records.
   Once the initial query for a name server has been done, all of the
   address and TLS information is available in the cache, and the DOT
   query can be made upon receipt of the TLD delegation record.  Once
   the initial query for a second-level domain has been done, the TLD
   delegation and all of the address and TLS information is available in
   the cache, and the DOT query can be made immediately.

   Once a cache is populated with wildcards from the name server domain,
   additional delegation queries require no more trips than those needed
   for normal UDP queries:

   1.  Query for delegation from TLD, and validate the response

   2.  Query for the name server's address(es), and validate the
       response

   3.  Send the query to the authoritative server for the domain with
       the sensitive name (over TLS or over UDP/TCP, depending on
       transport supported by the authoritative server)

   Once a cache is populated with name server addresses and wildcards,
   additional delegation queries require no more trips than those needed
   for normal UDP queries:

   1.  Query for delegation from TLD, and validate the response

   2.  Send the query to the authoritative server for the domain with
       the sensitive name (over TLS or over UDP/TCP, depending on
       transport supported by the authoritative server)







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8.  Signaling Resolver Support and Client Desire for ADoT

   The following presume some new OPT sub-types, to be added to the IANA
   action section or to be split out as separate drafts.  The sub-type
   mnemonics are "ADOTA" (available) and "ADOTD" (desired), each with an
   enumerated set of values and mnemonic codes.  Respectively those are:
   "Always", "Upon Request", and "Never"; and "Force", "If Available",
   and "Never".

8.1.  Server Side Support Signaling

   A DNS server (e.g. recursive resolver or forwarder) MAY signal to
   clients that it offers the use of ADoT.  The mechanism used is to set
   the EDNS option "ADOTA".  The values for this option are "Always",
   "Upon Request", and "Never".  The value "Always" indicates the server
   will always attempt to use ADoT without regards to client requests
   for ADoT.  The value "Upon Request" indicates that the server will
   ONLY use ADoT for upstream queries if the client requests that ADoT
   be used.  These values have no effect on answers served from the
   resolver's cache.  (The "Never" case is unusual, in that it signals
   the server understands the option, but does not perform ADoT.
   Generally this would be used to allow a client to track changes in
   the status, if the client is interested in uses of ADoT.)

8.2.  Client Side Desire Signaling

   A DNS client (e.g. stub or forwarder) MAY signal the desire to have
   the resolver use ADoT.  The mechanism used is to set the EDNS option
   "ADOTD".  The values for this option are "Force", "If Available", and
   "Never".  The value "Force" indicates the server should attempt to
   use ADoT, and return a failure code of XXXX and an EDE value of YYYY
   if the authoritative server does not offer ADoT, or any other ADoT
   failure occurs.  The value "If Available" indicates that the server
   should use ADoT for upstream queries if it is availble, but SHOULD
   NOT allow any downgrades if the authoritative server signals that
   ADoT is available.  These values have no effect on answers served
   from the resolver's cache.  (The "Never" case is unusual, in that it
   signals the client understands the option, but does not perform ADoT.
   Generally this would be used to allow a server to track changes in
   the client base, so the server operator can make informed decisions
   about enabling ADoT.)

9.  Security Considerations

   As outlined above, there could be security issues in various use
   cases.





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10.  IANA Considerations

   This document may or many not have any IANA actions. (e.g. if the
   RRTYPEs, EDNS subtypes, DNSKEY algorithms, etc., are defined in other
   documents, no IANA actions are needed.)

11.  Normative References

   [RFC6698]  Hoffman, P. and J. Schlyter, "The DNS-Based Authentication
              of Named Entities (DANE) Transport Layer Security (TLS)
              Protocol: TLSA", RFC 6698, DOI 10.17487/RFC6698, August
              2012, <https://www.rfc-editor.org/info/rfc6698>.

   [RFC7218]  Gudmundsson, O., "Adding Acronyms to Simplify
              Conversations about DNS-Based Authentication of Named
              Entities (DANE)", RFC 7218, DOI 10.17487/RFC7218, April
              2014, <https://www.rfc-editor.org/info/rfc7218>.

   [RFC7671]  Dukhovni, V. and W. Hardaker, "The DNS-Based
              Authentication of Named Entities (DANE) Protocol: Updates
              and Operational Guidance", RFC 7671, DOI 10.17487/RFC7671,
              October 2015, <https://www.rfc-editor.org/info/rfc7671>.

   [RFC7858]  Hu, Z., Zhu, L., Heidemann, J., Mankin, A., Wessels, D.,
              and P. Hoffman, "Specification for DNS over Transport
              Layer Security (TLS)", RFC 7858, DOI 10.17487/RFC7858, May
              2016, <https://www.rfc-editor.org/info/rfc7858>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

   [RFC8198]  Fujiwara, K., Kato, A., and W. Kumari, "Aggressive Use of
              DNSSEC-Validated Cache", RFC 8198, DOI 10.17487/RFC8198,
              July 2017, <https://www.rfc-editor.org/info/rfc8198>.

   [RFC8484]  Hoffman, P. and P. McManus, "DNS Queries over HTTPS
              (DoH)", RFC 8484, DOI 10.17487/RFC8484, October 2018,
              <https://www.rfc-editor.org/info/rfc8484>.

12.  Informative References

   [I-D.dickson-dnsop-ds-hack]
              Dickson, B., "DS Algorithms for Securing NS and Glue",
              Work in Progress, Internet-Draft, draft-dickson-dnsop-ds-
              hack-00, 11 August 2021,
              <https://datatracker.ietf.org/doc/html/draft-dickson-
              dnsop-ds-hack-00>.



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   [I-D.dickson-dnsop-glueless]
              Dickson, B., "Operating a Glueless DNS Authority Server",
              Work in Progress, Internet-Draft, draft-dickson-dnsop-
              glueless-00, 17 September 2021,
              <https://datatracker.ietf.org/doc/html/draft-dickson-
              dnsop-glueless-00>.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

Appendix A.  Acknowledgments

   Thanks to everyone who helped create the tools that let everyone use
   Markdown to create Internet Drafts, and the RFC Editor for xml2rfc.

   Thanks to Dan York for his Tutorial on using Markdown (specificially
   mmark) for writing IETF drafts.

   Thanks to YOUR NAME HERE for contributions, reviews, etc.

Author's Address

   Brian Dickson
   GoDaddy

   Email: brian.peter.dickson@gmail.com























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