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Versions: 00 01 02 draft-ietf-dnsop-algorithm-update

dnsop                                                         P. Wouters
Internet-Draft                                                   Red Hat
Intended status: Standards Track                                 O. Sury
Expires: September 18, 2016                                       CZ.NIC
                                                          March 17, 2016


  Algorithm Implementation Requirements and Usage Guidance for DNSSEC
              draft-wouters-sury-dnsop-algorithm-update-00

Abstract

   The DNSSEC protocol makes use of various cryptographic algorithms in
   order to provide authentication of DNS data and proof of non-
   existence.  To ensure interoperability between DNS resolvers and DNS
   authoritative servers, it is necessary to specify a set of algorithm
   implementation requirements and usage guidance to ensure that there
   is at least one algorithm that all implementations support.  This
   document defines the current algorithm implementation requirements
   and usage guidance for DNSSEC.

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 http://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 September 18, 2016.

Copyright Notice

   Copyright (c) 2016 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
   Provisions Relating to IETF Documents
   (http://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



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   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  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Updating Algorithm Implementation Requirements and Usage
           Guidance  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.2.  Updating Algorithm Requirement Levels . . . . . . . . . .   2
     1.3.  Document Audience . . . . . . . . . . . . . . . . . . . .   3
   2.  Conventions Used in This Document . . . . . . . . . . . . . .   4
   3.  Algorithm Selection . . . . . . . . . . . . . . . . . . . . .   4
     3.1.  DNSKEY Algorithms . . . . . . . . . . . . . . . . . . . .   4
     3.2.  DS and CDS Algorithms . . . . . . . . . . . . . . . . . .   5
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   5.  Operational Considerations  . . . . . . . . . . . . . . . . .   7
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   7
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   7
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   7
     8.2.  Informative References  . . . . . . . . . . . . . . . . .   7

1.  Introduction

   The DNSSEC signing algorithms are defined by various RFCs, including
   [RFC4034], [RFC5155], [RFC5702], [RFC5933], [RFC6605],
   [I-D.ietf-curdle-dnskey-ed25519] and [I-D.ietf-curdle-dnskey-ed448].
   DNSSEC is used to provide authentication of data.  To ensure
   interoperability, a set of "mandatory-to-implement" DNSKEY algorithms
   are defined.

1.1.  Updating Algorithm Implementation Requirements and Usage Guidance

   The field of cryptography evolves continuously.  New stronger
   algorithms appear and existing algorithms are found to be less secure
   then originally thought.  Therefore, algorithm implementation
   requirements and usage guidance need to be updated from time to time
   to reflect the new reality.  The choices for algorithms must be
   conservative to minimize the risk of algorithm compromise.

1.2.  Updating Algorithm Requirement Levels

   The mandatory-to-implement algorithm of tomorrow should already be
   available in most implementations of DNSSEC by the time it is made
   mandatory.  This document attempts to identify and introduce those
   algorithms for future mandatory-to-implement status.  There is no



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   guarantee that the algorithms in use today may become mandatory in
   the future.  Published algorithms are continuously subjected to
   cryptographic attack and may become too weak or could become
   completely broken before this document is updated.

   This document only provides recommendations for the mandatory-to-
   implement algorithms or algorithms too weak that are recommended not
   to be implemented.  As a result, any algorithm listed at the
   [DNSKEY-IANA] registry not mentioned in this document MAY be
   implemented.  For clarification and consistency, an algorithm will be
   set to MAY only when it has been downgraded.

   Although this document updates the algorithms to keep the DNSSEC
   authentication secure over time, it also aims at providing
   recommendations so that DNSSEC implementations remain interoperable.
   DNSSEC interoperability is addressed by an incremental introduction
   or deprecation of algorithms.

   It is expected that deprecation of an algorithm is performed
   gradually.  This provides time for various implementations to update
   their implemented algorithms while remaining interoperable.  Unless
   there are strong security reasons, an algorithm is expected to be
   downgraded from MUST to MUST- or SHOULD, instead of MUST NOT.
   Similarly, an algorithm that has not been mentioned as mandatory-to-
   implement is expected to be introduced with a SHOULD instead of a
   MUST.

   Since the effects of using an unknown DNSKEY algorithm is for the
   zone to be treated as insecure, it is recommended that algorithms
   downgraded to SHOULD- or below are no longer used by authoritative
   nameservers and DNSSEC signers to create new DNSKEY's.  This will
   allow for algorithms to slowly become more unused over time.  Once
   deployment has reached a sufficiently low point these algorithms can
   finally be marked as MUST NOT so that recursive nameservers can
   remove support for these algorithms.

   Recursive nameservers are encouraged to keep support for all
   algorithms not marked as MUST NOT.

1.3.  Document Audience











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   The recommendations of this document mostly target DNSSEC
   implementers as implementations need to meet both high security
   expectations as well as high interoperability between various vendors
   and with different versions.  Interoperability requires a smooth move
   to more secure algorithms.  This may differ from a user point of view
   that may deploy and configure DNSSEC with only the safest algorithm.
   On the other hand, comments and recommendations from this document
   are also expected to be useful for such users.

2.  Conventions Used in This Document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].

   We define some additional terms here:

   SHOULD+   This term means the same as SHOULD.  However, it is likely
             that an algorithm marked as SHOULD+ will be promoted at some
             future time to be a MUST.
   SHOULD-   This term means the same as SHOULD.  However, an algorithm
             marked as SHOULD- may be deprecated to a MAY in a future
             version of this document.
   MUST-     This term means the same as MUST.  However, we expect at
             some point that this algorithm will no longer be a MUST in a
             future document.  Although its status will be determined at
             a later time, it is reasonable to expect that if a future
             revision of a document alters the status of a MUST-
             algorithm, it will remain at least a SHOULD or a SHOULD-.

                                  Table 1

3.  Algorithm Selection

3.1.  DNSKEY Algorithms

   Recommendations for DNSKEY algorithms

   +--------+--------------------+----------------+-------------------+
   | Number | Mnemonics          | DNSSEC Signing | DNSSEC Validation |
   +--------+--------------------+----------------+-------------------+
   | 1      | RSAMD5             | MUST NOT       | MUST NOT          |
   | 3      | DSA                | MUST NOT       | MUST NOT          |
   | 5      | RSASHA1            | MUST-          | MUST-             |
   | 6      | DSA-NSEC3-SHA1     | MUST NOT       | MUST NOT          |
   | 7      | RSASHA1-NSEC3-SHA1 | MUST-          | MUST-             |
   | 8      | RSASHA256          | MUST           | MUST              |
   | 10     | RSASHA512          | SHOULD         | MUST              |



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   | 12     | ECC-GOST           | SHOULD         | SHOULD            |
   | 13     | ECDSAP256SHA256    | SHOULD+        | MUST              |
   | 14     | ECDSAP384SHA384    | SHOULD+        | SHOULD+           |
   | TBD    | ED25519            | SHOULD+        | SHOULD+           |
   | TBD    | ED448              | SHOULD         | SHOULD+           |
   +--------+--------------------+----------------+-------------------+

                                  Table 2

   RSAMD5 is not widely deployed and there is an industry-wide trend to
   deprecate MD5 usage.

   RSASHA1 and RSASHA1-NSEC3-SHA1 are widely deployed, although zones
   deploying it are recommended to switch to RSASHA256 as there is an
   industry-wide trend to deprecate SHA1 usage.  RSASHA1 does not
   support NSEC3.  RSASHA1-NSEC3-SHA1 can be used with or without NSEC3.

   DSA and DSA-NSEC3-SHA1 are not widely deployed and vulnerable to
   private key compromise when generating signatures using a weak or
   compromised random number generator.

   RSASHA512 is at the SHOULD level for DNSSEC Signing because it has
   not seen wide deployment, but there are some deployments hence DNSSEC
   Validation MUST implement RSASHA512 to ensure interoperability.

   ECC-GOST is at the SHOULD level because it has not seen wide
   deployment.

   ECDSAP256SHA256 and ECDSAP384SHA384 provide more strength for
   signature size than RSASHA256 and RSASHA512 variants.  It is expected
   to be raised to MUST once they have been deployed more widely for
   DNSSEC Signing.  ECDSAP256SHA256 has seen raise in the deployment, so
   it's set to MUST level for DNSSEC Validation.

   ED25519 and ED448 uses Edwards-curve Digital Security Algorithm
   (EdDSA).  There are three main advantages of the EdDSA algorithm: It
   does not require the use of a unique random number for each
   signature, there are no padding or truncation issues as with ECDSA,
   and it is more resilient to side-channel attacks.  Hence we expect
   that those algorithms will be raised to MUST once they have been
   deployed more widely.

3.2.  DS and CDS Algorithms

   Recommendations for Delegation Signer Digest Algorithms.  These also
   apply to the CDS RRTYPE as specified in [RFC7344]





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   +--------+-----------------+-------------------+-------------------+
   | Number | Mnemonics       | DNSSEC Delegation | DNSSEC Validation |
   +--------+-----------------+-------------------+-------------------+
   | 0      | NULL (CDS only) | MUST NOT [*]      | MUST NOT [*]      |
   | 1      | SHA-1           | SHOULD NOT        | MUST-             |
   | 2      | SHA-256         | MUST              | MUST              |
   | 3      | GOST R 34.11-94 | MAY               | SHOULD            |
   | 4      | SHA-384         | MAY               | SHOULD+           |
   +--------+-----------------+-------------------+-------------------+

   [*] - This is a special type of CDS record signaling removal of DS at
                the parent in [I-D.ietf-dnsop-maintain-ds]

                                  Table 3

   NULL is a special case, see [I-D.ietf-dnsop-maintain-ds]

   SHA-1 is in wide use for DS records, but its use is discouraged as it
   is an aging algorithm.  Users of SHA-1 SHOULD upgrade to SHA-256.

   SHA-256 is in wide use and considered strong.

   GOST R 34.11-94 is not in wide use.  It is still recommended to be
   supported in validators so that adoption can increase.

   SHA-384 is not in wide use.  It is still recommended to be supported
   in validators so that adoption can increase.

4.  Security Considerations

   The security of cryptographic-based systems depends on both the
   strength of the cryptographic algorithms chosen and the strength of
   the keys used with those algorithms.  The security also depends on
   the engineering of the protocol used by the system to ensure that
   there are no non-cryptographic ways to bypass the security of the
   overall system.

   This document concerns itself with the selection of cryptographic
   algorithms for the use of DNSSEC, specifically with the selection of
   "mandatory-to-implement" algorithms.  The algorithms identified in
   this document as "MUST implement" or "SHOULD implement" are not known
   to be broken at the current time, and cryptographic research so far
   leads us to believe that they will likely remain secure into the
   foreseeable future.  However, this isn't necessarily forever and it
   is expected that new revisions of this document will be issued from
   time to time to reflect the current best practice in this area.





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   Retiring an algorithm too soon would result in a signed zone with
   such an algorithm to be downgraded to the equivalent of an unsigned
   zone.  Therefore, algorithm deprecation must be done very slowly and
   only after careful consideration and measurements of its use.

5.  Operational Considerations

   DNSKEY algorithm rollover in a live zone is a complex process.  See
   [RFC6781] and [RFC7583] for guidelines on how to perform algorithm
   rollovers.

6.  IANA Considerations

   This document makes no requests of IANA.

7.  Acknowledgements

   This document borrows text from RFC 4307 by Jeffrey I.  Schiller of
   the Massachusetts Institute of Technology (MIT) and the 4307bis
   document by Yoav Nir, Tero Kivinen, Paul Wouters and Daniel Migault.
   Much of the original text has been copied verbatim.

   We wish to thank Olafur Gudmundsson and Paul Hoffman for their
   imminent feedback.

8.  References

8.1.  Normative References

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

8.2.  Informative References

   [RFC4034]  Arends, R., Austein, R., Larson, M., Massey, D., and S.
              Rose, "Resource Records for the DNS Security Extensions",
              RFC 4034, DOI 10.17487/RFC4034, March 2005,
              <http://www.rfc-editor.org/info/rfc4034>.

   [RFC5155]  Laurie, B., Sisson, G., Arends, R., and D. Blacka, "DNS
              Security (DNSSEC) Hashed Authenticated Denial of
              Existence", RFC 5155, DOI 10.17487/RFC5155, March 2008,
              <http://www.rfc-editor.org/info/rfc5155>.

   [RFC5702]  Jansen, J., "Use of SHA-2 Algorithms with RSA in DNSKEY
              and RRSIG Resource Records for DNSSEC", RFC 5702, DOI



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              10.17487/RFC5702, October 2009,
              <http://www.rfc-editor.org/info/rfc5702>.

   [RFC5933]  Dolmatov, V., Ed., Chuprina, A., and I. Ustinov, "Use of
              GOST Signature Algorithms in DNSKEY and RRSIG Resource
              Records for DNSSEC", RFC 5933, DOI 10.17487/RFC5933, July
              2010, <http://www.rfc-editor.org/info/rfc5933>.

   [RFC6605]  Hoffman, P. and W. Wijngaards, "Elliptic Curve Digital
              Signature Algorithm (DSA) for DNSSEC", RFC 6605, DOI
              10.17487/RFC6605, April 2012,
              <http://www.rfc-editor.org/info/rfc6605>.

   [RFC6781]  Kolkman, O., Mekking, W., and R. Gieben, "DNSSEC
              Operational Practices, Version 2", RFC 6781, DOI 10.17487/
              RFC6781, December 2012,
              <http://www.rfc-editor.org/info/rfc6781>.

   [RFC7344]  Kumari, W., Gudmundsson, O., and G. Barwood, "Automating
              DNSSEC Delegation Trust Maintenance", RFC 7344, DOI
              10.17487/RFC7344, September 2014,
              <http://www.rfc-editor.org/info/rfc7344>.

   [RFC7583]  Morris, S., Ihren, J., Dickinson, J., and W. Mekking,
              "DNSSEC Key Rollover Timing Considerations", RFC 7583, DOI
              10.17487/RFC7583, October 2015,
              <http://www.rfc-editor.org/info/rfc7583>.

   [I-D.ietf-curdle-dnskey-ed25519]
              Sury, O. and R. Edmonds, "Ed25519 for DNSSEC", draft-ietf-
              curdle-dnskey-ed25519-01 (work in progress), February
              2016.

   [I-D.ietf-curdle-dnskey-ed448]
              Sury, O. and R. Edmonds, "Ed448 for DNSSEC", draft-ietf-
              curdle-dnskey-ed448-00 (work in progress), March 2016.

   [I-D.ietf-dnsop-maintain-ds]
              Gu[eth]mundsson, O. and P. Wouters, "Managing DS records
              from parent via CDS/CDNSKEY", draft-ietf-dnsop-maintain-
              ds-00 (work in progress), December 2015.

   [DNSKEY-IANA]
              , "DNSKEY Algorithms", , <http://www.iana.org/assignments/
              dns-sec-alg-numbers/dns-sec-alg-numbers.xhtml>.

   [DS-IANA]  , "Delegation Signer Digest Algorithms", , <http://
              www.iana.org/assignments/ds-rr-types/ds-rr-types.xhtml>.



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Authors' Addresses

   Paul Wouters
   Red Hat

   EMail: pwouters@redhat.com


   Ondrej Sury
   CZ.NIC

   EMail: ondrej.sury@nic.cz







































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