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Network Working Group                                          D. BlackaRequest for Comments: 4955                                VeriSign, Inc.Category: Standards Track                                      July 2007DNS Security (DNSSEC) ExperimentsStatus of This Memo   This document specifies an Internet standards track protocol for the   Internet community, and requests discussion and suggestions for   improvements.  Please refer to the current edition of the "Internet   Official Protocol Standards" (STD 1) for the standardization state   and status of this protocol.  Distribution of this memo is unlimited.Copyright Notice   Copyright (C) The IETF Trust (2007).Abstract   This document describes a methodology for deploying alternate, non-   backwards-compatible, DNS Security (DNSSEC) methodologies in an   experimental fashion without disrupting the deployment of standard   DNSSEC.Table of Contents1.  Overview  . . . . . . . . . . . . . . . . . . . . . . . . . . .22.  Definitions and Terminology . . . . . . . . . . . . . . . . . .23.  Experiments . . . . . . . . . . . . . . . . . . . . . . . . . .24.  Method  . . . . . . . . . . . . . . . . . . . . . . . . . . . .35.  Defining an Experiment  . . . . . . . . . . . . . . . . . . . .46.  Considerations  . . . . . . . . . . . . . . . . . . . . . . . .57.  Use in Non-Experiments  . . . . . . . . . . . . . . . . . . . .58.  Security Considerations . . . . . . . . . . . . . . . . . . . .59.  References  . . . . . . . . . . . . . . . . . . . . . . . . . .69.1.  Normative References  . . . . . . . . . . . . . . . . . . .69.2.  Informative References  . . . . . . . . . . . . . . . . . .6Blacka                      Standards Track                     [Page 1]

RFC 4955           DNS Security (DNSSEC) Experiments           July 20071.  Overview   Historically, experimentation with DNSSEC alternatives has been a   problematic endeavor.  There has typically been a desire to both   introduce non-backwards-compatible changes to DNSSEC and to try these   changes on real zones in the public DNS.  This creates a problem when   the change to DNSSEC would make all or part of the zone using those   changes appear bogus (bad) or otherwise broken to existing security-   aware resolvers.   This document describes a standard methodology for setting up DNSSEC   experiments.  This methodology addresses the issue of coexistence   with standard DNSSEC and DNS by using unknown algorithm identifiers   to hide the experimental DNSSEC protocol modifications from standard   security-aware resolvers.2.  Definitions and Terminology   Throughout this document, familiarity with the DNS system (RFC 1035   [5]) and the DNS security extensions (RFC 4033 [2],RFC 4034 [3], andRFC 4035 [4]) is assumed.   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 inRFC 2119 [1].3.  Experiments   When discussing DNSSEC experiments, it is necessary to classify these   experiments into two broad categories:   Backwards-Compatible:  describes experimental changes that, while not      strictly adhering to the DNSSEC standard, are nonetheless      interoperable with clients and servers that do implement the      DNSSEC standard.   Non-Backwards-Compatible:  describes experiments that would cause a      standard security-aware resolver to (incorrectly) determine that      all or part of a zone is bogus, or to otherwise not interoperate      with standard DNSSEC clients and servers.   Not included in these terms are experiments with the core DNS   protocol itself.   The methodology described in this document is not necessary for   backwards-compatible experiments, although it certainly may be used   if desired.Blacka                      Standards Track                     [Page 2]

RFC 4955           DNS Security (DNSSEC) Experiments           July 20074.  Method   The core of the methodology is the use of strictly unknown algorithm   identifiers when signing the experimental zone, and more importantly,   having only unknown algorithm identifiers in the DS records for the   delegation to the zone at the parent.   This technique works because of the way DNSSEC-compliant validators   are expected to work in the presence of a DS set with only unknown   algorithm identifiers.  FromRFC 4035 [4], Section 5.2:      If the validator does not support any of the algorithms listed in      an authenticated DS RRset, then the resolver has no supported      authentication path leading from the parent to the child.  The      resolver should treat this case as it would the case of an      authenticated NSEC RRset proving that no DS RRset exists, as      described above.   And further:      If the resolver does not support any of the algorithms listed in      an authenticated DS RRset, then the resolver will not be able to      verify the authentication path to the child zone.  In this case,      the resolver SHOULD treat the child zone as if it were unsigned.   Although this behavior isn't strictly mandatory (as marked by MUST),   it is unlikely for a validator to implement a substantially different   behavior.  Essentially, if the validator does not have a usable chain   of trust to a child zone, then it can only do one of two things:   treat responses from the zone as insecure (the recommended behavior),   or treat the responses as bogus.  If the validator chooses the   latter, this will both violate the expectation of the zone owner and   defeat the purpose of the above rule.  However, with local policy, it   is within the right of a validator to refuse to trust certain zones   based on any criteria, including the use of unknown signing   algorithms.   Because we are talking about experiments, it is RECOMMENDED that   private algorithm numbers be used (seeRFC 4034 [3],Appendix A.1.1.   Note that secure handling of private algorithms requires special   handing by the validator logic.  See "Clarifications and   Implementation Notes for DNSSECbis" [6] for further details.)   Normally, instead of actually inventing new signing algorithms, the   recommended path is to create alternate algorithm identifiers that   are aliases for the existing, known algorithms.  While, strictly   speaking, it is only necessary to create an alternate identifier for   the mandatory algorithms, it is suggested that all optional defined   algorithms be aliased as well.Blacka                      Standards Track                     [Page 3]

RFC 4955           DNS Security (DNSSEC) Experiments           July 2007   It is RECOMMENDED that for a particular DNSSEC experiment, a   particular domain name base is chosen for all new algorithms, then   the algorithm number (or name) is prepended to it.  For example, for   experiment A, the base name of "dnssec-experiment-a.example.com" is   chosen.  Then, aliases for algorithms 3 (DSA) and 5 (RSASHA1) are   defined to be "3.dnssec-experiment-a.example.com" and   "5.dnssec-experiment-a.example.com".  However, any unique identifier   will suffice.   Using this method, resolvers (or, more specifically, DNSSEC   validators) essentially indicate their ability to understand the   DNSSEC experiment's semantics by understanding what the new algorithm   identifiers signify.   This method creates two classes of security-aware servers and   resolvers: servers and resolvers that are aware of the experiment   (and thus recognize the experiment's algorithm identifiers and   experimental semantics), and servers and resolvers that are unaware   of the experiment.   This method also precludes any zone from being both in an experiment   and in a classic DNSSEC island of security.  That is, a zone is   either in an experiment and only possible to validate experimentally,   or it is not.5.  Defining an Experiment   The DNSSEC experiment MUST define the particular set of (previously   unknown) algorithm identifiers that identify the experiment and   define what each unknown algorithm identifier means.  Typically,   unless the experiment is actually experimenting with a new DNSSEC   algorithm, this will be a mapping of private algorithm identifiers to   existing, known algorithms.   Normally the experiment will choose a DNS name as the algorithm   identifier base.  This DNS name SHOULD be under the control of the   authors of the experiment.  Then the experiment will define a mapping   between known mandatory and optional algorithms into this private   algorithm identifier space.  Alternately, the experiment MAY use the   Object Identifier (OID) private algorithm space instead (using   algorithm number 254), or MAY choose non-private algorithm numbers,   although this would require an IANA allocation.   For example, an experiment might specify in its description the DNS   name "dnssec-experiment-a.example.com" as the base name, and declare   that "3.dnssec-experiment-a.example.com" is an alias of DNSSEC   algorithm 3 (DSA), and that "5.dnssec-experiment-a.example.com" is an   alias of DNSSEC algorithm 5 (RSASHA1).Blacka                      Standards Track                     [Page 4]

RFC 4955           DNS Security (DNSSEC) Experiments           July 2007   Resolvers MUST only recognize the experiment's semantics when present   in a zone signed by one or more of these algorithm identifiers.  This   is necessary to isolate the semantics of one experiment from any   others that the resolver might understand.   In general, resolvers involved in the experiment are expected to   understand both standard DNSSEC and the defined experimental DNSSEC   protocol, although this isn't required.6.  Considerations   There are a number of considerations with using this methodology.   1.  If an unaware validator does not correctly follow the rules laid       out inRFC 4035 (e.g., the validator interprets a DNSSEC record       prior to validating it), or if the experiment is broader in scope       that just modifying the DNSSEC semantics, the experiment may not       be sufficiently masked by this technique.  This may cause       unintended resolution failures.   2.  It will not be possible for security-aware resolvers unaware of       the experiment to build a chain of trust through an experimental       zone.7.  Use in Non-Experiments   This general methodology MAY be used for non-backwards compatible   DNSSEC protocol changes that start out as or become standards.  In   this case:   o  The protocol change SHOULD use public IANA allocated algorithm      identifiers instead of private algorithm identifiers.  This will      help identify the protocol change as a standard, rather than an      experiment.   o  Resolvers MAY recognize the protocol change in zones not signed      (or not solely signed) using the new algorithm identifiers.8.  Security Considerations   Zones using this methodology will be considered insecure by all   resolvers except those aware of the experiment.  It is not generally   possible to create a secure delegation from an experimental zone that   will be followed by resolvers unaware of the experiment.   Implementers should take into account any security issues that may   result from environments being configured to trust both experimental   and non-experimental zones.  If the experimental zone is moreBlacka                      Standards Track                     [Page 5]

RFC 4955           DNS Security (DNSSEC) Experiments           July 2007   vulnerable to attacks, it could, for example, be used to promote   trust in zones not part of the experiment, possibly under the control   of an attacker.9.  References9.1.  Normative References   [1]  Bradner, S., "Key words for use in RFCs to Indicate Requirement        Levels",BCP 14,RFC 2119, March 1997.   [2]  Arends, R., Austein, R., Larson, M., Massey, D., and S. Rose,        "DNS Security Introduction and Requirements",RFC 4033,        March 2005.   [3]  Arends, R., Austein, R., Larson, M., Massey, D., and S. Rose,        "Resource Records for the DNS Security Extensions",RFC 4034,        March 2005.   [4]  Arends, R., Austein, R., Larson, M., Massey, D., and S. Rose,        "Protocol Modifications for the DNS Security Extensions",RFC 4035, March 2005.9.2.  Informative References   [5]  Mockapetris, P., "Domain names - implementation and        specification", STD 13,RFC 1035, November 1987.   [6]  Weiler, S. and R. Austein, "Clarifications and Implementation        Notes for DNSSECbis", Work in Progress, March 2007.Author's Address   David Blacka   VeriSign, Inc.   21355 Ridgetop Circle   Dulles, VA  20166   US   Phone: +1 703 948 3200   EMail: davidb@verisign.com   URI:http://www.verisignlabs.comBlacka                      Standards Track                     [Page 6]

RFC 4955           DNS Security (DNSSEC) Experiments           July 2007Full Copyright Statement   Copyright (C) The IETF Trust (2007).   This document is subject to the rights, licenses and restrictions   contained inBCP 78, and except as set forth therein, the authors   retain all their rights.   This document and the information contained herein are provided on an   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND   THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS   OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF   THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED   WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.Intellectual Property   The IETF takes no position regarding the validity or scope of any   Intellectual Property Rights or other rights that might be claimed to   pertain to the implementation or use of the technology described in   this document or the extent to which any license under such rights   might or might not be available; nor does it represent that it has   made any independent effort to identify any such rights.  Information   on the procedures with respect to rights in RFC documents can be   found inBCP 78 andBCP 79.   Copies of IPR disclosures made to the IETF Secretariat and any   assurances of licenses to be made available, or the result of an   attempt made to obtain a general license or permission for the use of   such proprietary rights by implementers or users of this   specification can be obtained from the IETF on-line IPR repository athttp://www.ietf.org/ipr.   The IETF invites any interested party to bring to its attention any   copyrights, patents or patent applications, or other proprietary   rights that may cover technology that may be required to implement   this standard.  Please address the information to the IETF at   ietf-ipr@ietf.org.Acknowledgement   Funding for the RFC Editor function is currently provided by the   Internet Society.Blacka                      Standards Track                     [Page 7]