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Internet Engineering Task Force                                 S. Huque
Internet-Draft                                                   P. Aras
Intended status: Informational                                Salesforce
Expires: September 03, 2018                               March 02, 2018


                      Multi Provider DNSSEC models
               draft-huque-dnsop-multi-provider-dnssec-00

Abstract

   Many enterprises today employ the service of multiple DNS providers
   to distribute their authoritative DNS service.  Deploying DNSSEC in
   such an environment can have some challenges depending on the
   configuration and feature set in use.  This document will present
   several deployment models that may be suitable.

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
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   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on September 03, 2018.

Copyright Notice

   Copyright (c) 2018 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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   described in the Simplified BSD License.



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Table of Contents

   1.  Introduction and Motivation . . . . . . . . . . . . . . . . .   2
   2.  Deployment Models . . . . . . . . . . . . . . . . . . . . . .   2
     2.1.  Serve Only model  . . . . . . . . . . . . . . . . . . . .   2
     2.2.  Sign and Serve models . . . . . . . . . . . . . . . . . .   3
       2.2.1.  Model 1 . . . . . . . . . . . . . . . . . . . . . . .   3
       2.2.2.  Model 2 . . . . . . . . . . . . . . . . . . . . . . .   4
       2.2.3.  Model 3 . . . . . . . . . . . . . . . . . . . . . . .   4
     2.3.  Inline Signing models . . . . . . . . . . . . . . . . . .   4
   3.  Signing Algorithm Considerations  . . . . . . . . . . . . . .   4
   4.  Validating Resolver Behavior  . . . . . . . . . . . . . . . .   5
   5.  Key Rollover Considerations . . . . . . . . . . . . . . . . .   5
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   5
     8.2.  Informative References  . . . . . . . . . . . . . . . . .   5
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   5

1.  Introduction and Motivation

   Many enterprises today employ the service of multiple DNS providers
   to distribute their authoritative DNS service.  Two providers are
   fairly typical and this allows the DNS service to survive a complete
   failure of any single provider.  This document outlines some possible
   models of DNSSEC deployment in such an environment.

2.  Deployment Models

   The two main models discussed are (1) where the zone owner runs a
   master signing server and essentially treats the managed DNS
   providers as secondary servers, the "Serve Only" model, and (2) where
   the managed DNS providers each act like primary servers, signing data
   received from the zone owner and serving it out to DNS queriers, the
   "Sign and Serve" model.

2.1.  Serve Only model

   The most straightforward deployment model is one in which the zone
   owner runs a primary master DNS server, and manages the signing of
   zone data.  The master server uses DNS zone transfer mechanisms (AXFR
   /IXFR) to distribute the signed zone to multiple DNS providers.

   This is also arguably the most secure model because the zone owner
   holds the private signing keys.  The managed DNS providers cannot
   serve bogus data (either maliciously or because of compromise of
   their systems) without detection by validating resolvers.



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   One notable limitation of this model is that it may not work with DNS
   authoritative server configurations that use certain non-standardized
   DNS features.  Some of these features like DNS based Global Server
   Load Balancing (GSLB), dynamic failover pools, etc. rely on querier
   specific responses, or responses based on real-time state
   examination, and so, the answer and corresponding signature has to be
   determined at the authoritative server being queried, at the time of
   the query, or both.

2.2.  Sign and Serve models

   In this category of models, multiple providers each independently
   sign and serve the same zone.  The zone owner typically uses
   provider-specific APIs to update zone content at each of the
   providers, and relies on the provider to perform signing of the data.
   The main challenge here is to manage the contents of the DNSKEY and
   DS RRset in such a way that validating resolvers always have a viable
   path to authenticate the DNSSEC signature chain no matter which
   provider they query and obtain responses from.

   These models can support DNSSEC even for the non-standard features
   mentioned previously, if the DNS providers have the capability of
   signing the response data generated by those features.  Since these
   responses are often generated dynamically at query time, one method
   is for the provider to perform online signing (also known as on-the-
   fly signing).  However, another possible approach is to pre-compute
   all the possible response sets and associated signatures and then
   algorithmically determine at query time which response set needs to
   be returned.

   In these models, the function of coordinating the DNSKEY or DS RRset
   does not involve the providers communicating directly with each
   other, which they are unlikely to do since they typically have a
   contractual relationship only with the customer.

   The following descriptions consider the case of two DNS providers,
   but the model is generalizable to any number.

2.2.1.  Model 1

   o  Customer holds the KSK and manages the DS record.

   o  Each provider has their own ZSK which is used to sign data

   o  Providers have an API that customer uses to query the ZSK public
      key, and insert a combined DNSKEY RRset that includes both ZSKs
      and the KSK, signed by the KSK.




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   o  Key rollovers need coordinated customer participation to update
      and re-sign the DNSKEY RRset.

2.2.2.  Model 2

   o  Each provider has their own KSK and ZSK.

   o  Each provider also includes the ZSK of the other provider -
      delivered to them by the customer via some API mechanism

   o  DNSKEY RRset is signed independently by each provider using their
      own KSK.

   o  Customer manages the DS record that includes both KSKs.

   o  KSK rollovers need coordinated customer participation to update
      the DS.

2.2.3.  Model 3

   Possible models in which KSK and/or ZSK key pairs are shared across
   providers are not currently discussed.  Preliminary discussion with
   some providers has revealed that this is not a mode all of them are
   comfortable with, as they do not want to share signing keys with
   other parties.

2.3.  Inline Signing models

   In this model, the zone owner runs a master server but does not
   perform zone signing, instead pushing out the zone (typically via
   zone transfer mechanisms) to multiple providers, and relying on those
   providers to sign the zone data before serving them out.  This model
   has to address the same set of requirements as the Sign-and-Serve
   model regarding managing the DNSKEY and DS RRsets.  However, assuming
   standardized zone transfers mechanisms are being used to push out the
   zone to the providers, it likely also has the limitation that non-
   standardized DNS features cannot be supported or signed.  This model
   is not discussed further.

3.  Signing Algorithm Considerations

   [TBD: at the very least we have to consider whether any or all of
   these schemes require algorithms to be the same or not, or benefit
   from algorithms being the same.  Current DNS specifications indicate
   that if there are multiple algorithms in the DNSKEY RRset, then data
   records need to be signed with at least one of each algorithm, (how
   does that work with online signing?).  Multiple signatures per record
   set is a cost that probably few operators want to bear.]



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4.  Validating Resolver Behavior

   TBD

5.  Key Rollover Considerations

   TBD

6.  IANA Considerations

   This document includes no request to IANA.

7.  Security Considerations

   [TBD]

8.  References

8.1.  Normative References

   [RFC4033]  Arends, R., Austein, R., Larson, M., Massey, D., and S.
              Rose, "DNS Security Introduction and Requirements", RFC
              4033, March 2005.

   [RFC4034]  Arends, R., Austein, R., Larson, M., Massey, D., and S.
              Rose, "Resource Records for the DNS Security Extensions",
              RFC 4034, March 2005.

   [RFC4035]  Arends, R., Austein, R., Larson, M., Massey, D., and S.
              Rose, "Protocol Modifications for the DNS Security
              Extensions", RFC 4035, March 2005.

8.2.  Informative References

   [RFC3552]  Rescorla, E. and B. Korver, "Guidelines for Writing RFC
              Text on Security Considerations", BCP 72, RFC 3552, July
              2003.

Authors' Addresses

   Shumon Huque
   Salesforce

   Email: shuque@gmail.com







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   Pallavi Aras
   Salesforce

   Email: paras@salesforce.com















































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