Tech-invite3GPPspaceIETF RFCsSIP
93929190898887868584838281807978777675747372717069686766656463626160595857565554535251504948474645444342414039383736353433323130292827262524232221201918171615141312111009080706050403020100
in Index   Prev   Next

RFC 4986

Requirements Related to DNS Security (DNSSEC) Trust Anchor Rollover

Pages: 11
Informational

Top   ToC   RFC4986 - Page 1
Network Working Group                                           H. Eland
Request for Comments: 4986                               Afilias Limited
Category: Informational                                         R. Mundy
                                                            SPARTA, Inc.
                                                              S. Crocker
                                                           Shinkuro Inc.
                                                         S. Krishnaswamy
                                                            SPARTA, Inc.
                                                             August 2007


  Requirements Related to DNS Security (DNSSEC) Trust Anchor Rollover

Status of This Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard of any kind.  Distribution of this
   memo is unlimited.

Abstract

Every DNS security-aware resolver must have at least one Trust Anchor to use as the basis for validating responses from DNS signed zones. For various reasons, most DNS security-aware resolvers are expected to have several Trust Anchors. For some operations, manual monitoring and updating of Trust Anchors may be feasible, but many operations will require automated methods for updating Trust Anchors in their security-aware resolvers. This document identifies the requirements that must be met by an automated DNS Trust Anchor rollover solution for security-aware DNS resolvers.
Top   ToC   RFC4986 - Page 2

Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Background . . . . . . . . . . . . . . . . . . . . . . . . . . 3 4. Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . 4 5. Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 6 5.1. Scalability . . . . . . . . . . . . . . . . . . . . . . . . 6 5.2. No Known Intellectual Property Encumbrance . . . . . . . . 6 5.3. General Applicability . . . . . . . . . . . . . . . . . . . 7 5.4. Support Private Networks . . . . . . . . . . . . . . . . . 7 5.5. Detection of Stale Trust Anchors . . . . . . . . . . . . . 7 5.6. Manual Operations Permitted . . . . . . . . . . . . . . . . 7 5.7. Planned and Unplanned Rollovers . . . . . . . . . . . . . . 7 5.8. Timeliness . . . . . . . . . . . . . . . . . . . . . . . . 8 5.9. High Availability . . . . . . . . . . . . . . . . . . . . . 8 5.10. New RR Types . . . . . . . . . . . . . . . . . . . . . . . 8 5.11. Support for Trust Anchor Maintenance Operations . . . . . . 8 5.12. Recovery from Compromise . . . . . . . . . . . . . . . . . 8 5.13. Non-Degrading Trust . . . . . . . . . . . . . . . . . . . . 8 6. Security Considerations . . . . . . . . . . . . . . . . . . . . 9 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 9 8. Normative References . . . . . . . . . . . . . . . . . . . . . 9
Top   ToC   RFC4986 - Page 3

1. Introduction

The Domain Name System Security Extensions (DNSSEC), as described in [2], [3], and [4], define new records and protocol modifications to DNS that permit security-aware resolvers to validate DNS Resource Records (RRs) from one or more Trust Anchors held by such security- aware resolvers. Security-aware resolvers will have to initially obtain their Trust Anchors in a trustworthy manner to ensure the Trust Anchors are correct and valid. There are a number of ways that this initial step can be accomplished; however, details of this step are beyond the scope of this document. Once an operator has obtained Trust Anchors, initially entering the Trust Anchors into their security-aware resolvers will in many instances be a manual operation. For some operational environments, manual management of Trust Anchors might be a viable approach. However, many operational environments will require a more automated, specification-based method for updating and managing Trust Anchors. This document provides a list of requirements that can be used to measure the effectiveness of any proposed automated Trust Anchor rollover mechanism in a consistent manner.

2. Terminology

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 RFC 2119 [1]. The use of RFC 2119 words in the requirements is intended to unambiguously describe a requirement. If a tradeoff is to be made between conflicting requirements when choosing a solution, the requirement with MUST language will have higher preference than requirements with SHOULD, MAY, or RECOMMENDED language. It is understood that a tradeoff may need to be made between requirements that both contain RFC 2119 language.

3. Background

DNS resolvers need to have one or more starting points to use in obtaining DNS answers. The starting points for stub resolvers are normally the IP addresses for one or more recursive name servers. The starting points for recursive name servers are normally IP addresses for DNS Root name servers. Similarly, security-aware resolvers must have one or more starting points to use for building the authenticated chain to validate a signed DNS response. Instead of IP addresses, DNSSEC requires that each resolver trust one or more
Top   ToC   RFC4986 - Page 4
   DNSKEY RRs or DS RRs as their starting point.  Each of these starting
   points is called a Trust Anchor.

   It should be noted that DNSKEY RRs and DS RRs are not Trust Anchors
   when they are created by the signed zone operator nor are they Trust
   Anchors because the records are published in the signed zone.  A
   DNSKEY RR or DS RR becomes a Trust Anchor when an operator of a
   security-aware resolver determines that the public key or hash will
   be used as a Trust Anchor.  Thus, the signed zone operator that
   created and/or published these RRs may not know if any of the DNSKEY
   RRs or DS RRs associated with their zone are being used as Trust
   Anchors by security-aware resolvers.  The obvious exceptions are the
   DNSKEY RRs for the Root Zone, which will be used as Trust Anchors by
   many security-aware resolvers.  For various reasons, DNSKEY RRs or DS
   RRs from zones other than Root can be used by operators of security-
   aware resolvers as Trust Anchors.  It follows that responsibility
   lies with the operator of the security-aware resolver to ensure that
   the DNSKEY and/or DS RRs they have chosen to use as Trust Anchors are
   valid at the time they are used by the security-aware resolver as the
   starting point for building the authentication chain to validate a
   signed DNS response.

   When operators of security-aware resolvers choose one or more Trust
   Anchors, they must also determine the method(s) they will use to
   ensure that they are using valid RRs and that they are able to
   determine when RRs being used as Trust Anchors should be replaced or
   removed.  Early adopters of DNS signed zones have published
   information about the processes and methods they will use when their
   DNSKEY and/or DS RRs change so that operators of security-aware
   resolvers can manually change the Trust Anchors at the appropriate
   time.  This manual approach will not scale and, therefore, drives the
   need for an automated specification-based approach for rollover of
   Trust Anchors for security-aware resolvers.

4. Definitions

This document uses the definitions contained in RFC 4033, section 2, plus the following additional definitions: Trust Anchor: From RFC 4033, "A configured DNSKEY RR or DS RR hash of a DNSKEY RR. A validating security-aware resolver uses this public key or hash as a starting point for building the authentication chain to a signed DNS response." Additionally, a DNSKEY RR or DS RR is associated with precisely one point in the DNS hierarchy, i.e., one DNS zone. Multiple Trust Anchors MAY be associated with each DNS zone and MAY be held by any number of security-aware resolvers. Security-aware resolvers MAY have Trust Anchors from multiple DNS zones. Those responsible for the
Top   ToC   RFC4986 - Page 5
      operation of security-aware resolvers are responsible for
      determining the set of RRs that will be used as Trust Anchors by
      that resolver.

   Initial Trust Relationship:  Operators of security-aware resolvers
      must ensure that they initially obtain any Trust Anchors in a
      trustworthy manner.  For example, the correctness of the Root Zone
      DNSKEY RR(s) could be verified by comparing what the operator
      believes to be the Root Trust Anchor(s) with several 'well-known'
      sources such as the IANA web site, the DNS published Root Zone and
      the publication of the public key in well-known hard-copy forms.
      For other Trust Anchors, the operator must ensure the accuracy and
      validity of the DNSKEY and/or DS RRs before designating them Trust
      Anchors.  This might be accomplished through a combination of
      technical, procedural, and contractual relationships, or use other
      existing trust relationships outside the current DNS protocol.

   Trust Anchor Distribution:  The method or methods used to convey the
      DNSKEY and/or DS RR(s) between the signed zone operator and the
      security-aware resolver operator.  The method or methods MUST be
      deemed sufficiently trustworthy by the operator of the security-
      aware resolver to ensure source authenticity and integrity of the
      new RRs to maintain the Initial Trust Relationship required to
      designate those RRs as Trust Anchors.

   Trust Anchor Maintenance:  Any change in a validating security-aware
      resolver to add a new Trust Anchor, delete an existing Trust
      Anchor, or replace an existing Trust Anchor with another.  This
      change might be accomplished manually or in some automated manner.
      Those responsible for the operation of the security-aware resolver
      are responsible for establishing policies and procedures to ensure
      that a sufficient Initial Trust Relationship is in place before
      adding Trust Anchors for a particular DNS zone to their security-
      aware resolver configuration.

   Trust Anchor Revocation and Removal:  The invalidation of a
      particular Trust Anchor that results when the operator of the
      signed zone revokes or removes a DNSKEY RR or DS RR that is being
      used as a Trust Anchor by any security-aware resolver.  It is
      possible that a zone administrator may invalidate more than one RR
      at one point in time; therefore, it MUST be clear to both the zone
      administrator and the security-aware resolver the exact RR(s) that
      have been revoked or removed so the proper Trust Anchor or Trust
      Anchors are removed.
Top   ToC   RFC4986 - Page 6
   Trust Anchor Rollover:  The method or methods necessary for the
      secure replacement of one or multiple Trust Anchors held by
      security-aware resolvers.  Trust Anchor Rollover should be
      considered a subset of Trust Anchor Maintenance.

   Normal or Pre-Scheduled Trust Anchor Rollover:  The operator of a
      DNSSEC signed zone has issued a new DNSKEY and/or DS RR(s) as a
      part of an operational routine.

   Emergency or Non-Scheduled Trust Anchor Rollover:  The operator of a
      signed zone has issued a new DNSKEY and/or DS RR(s) as part of an
      exceptional event.

   Emergency Trust Anchor Revocation:  The operator of a signed zone
      wishes to indicate that the current DNSKEY and/or DS RR(s) are no
      longer valid as part of an exceptional event.

5. Requirements

Following are the requirements for DNSSEC automated specification- based Trust Anchor Rollover:

5.1. Scalability

The automated Trust Anchor Rollover solution MUST be capable of scaling to Internet-wide usage. The probable largest number of instances of security-aware resolvers needing to rollover a Trust Anchor will be those that use the public key(s) for the Root Zone as Trust Anchor(s). This number could be extremely large if a number of applications have embedded security-aware resolvers. The automated Trust Anchor Rollover solution MUST be able to support Trust Anchors for multiple zones and multiple Trust Anchors for each DNS zone. The number of Trust Anchors that might be configured into any one validating security-aware resolver is not known with certainty at this time; in most cases it will be less than 20 but it may even be as high as one thousand.

5.2. No Known Intellectual Property Encumbrance

Because trust anchor rollover is likely to be "mandatory-to- implement", section 8 of [5] requires that the technical solution chosen must not be known to be encumbered or must be available under royalty-free terms. For this purpose, "royalty-free" is defined as follows: worldwide, irrevocable, perpetual right to use, without fee, in commerce or otherwise, where "use" includes descriptions of algorithms,
Top   ToC   RFC4986 - Page 7
   distribution and/or use of hardware implementations, distribution
   and/or use of software systems in source and/or binary form, in all
   DNS or DNSSEC applications including registry, registrar, domain name
   service including authority, recursion, caching, forwarding, stub
   resolver, or similar.

   In summary, no implementor, distributor, or operator of the
   technology chosen for trust anchor management shall be expected or
   required to pay any fee to any IPR holder for the right to implement,
   distribute, or operate a system which includes the chosen mandatory-
   to-implement solution.

5.3. General Applicability

The solution MUST provide the capability to maintain Trust Anchors in security-aware resolvers for any and all DNS zones.

5.4. Support Private Networks

The solution MUST support private networks with their own DNS hierarchy.

5.5. Detection of Stale Trust Anchors

The Trust Anchor Rollover solution MUST allow a validating security- aware resolver to be able to detect if the DNSKEY and/or DS RR(s) can no longer be updated given the current set of actual trust-anchors. In these cases, the resolver should inform the operator of the need to reestablish initial trust.

5.6. Manual Operations Permitted

The operator of a security-aware resolver may choose manual or automated rollover, but the rollover protocol must allow the implementation to support both automated and manual Trust Anchor Maintenance operations. Implementation of the rollover protocol is likely to be mandatory, but that's out of scope for this requirements document.

5.7. Planned and Unplanned Rollovers

The solution MUST permit both planned (pre-scheduled) and unplanned (non-scheduled) rollover of Trust Anchors. Support for providing an Initial Trust Relationship is OPTIONAL.
Top   ToC   RFC4986 - Page 8

5.8. Timeliness

Resource Records used as Trust Anchors SHOULD be able to be distributed to security-aware resolvers in a timely manner. Security-aware resolvers need to acquire new and remove revoked DNSKEY and/or DS RRs that are being used as Trust Anchors for a zone such that no old RR is used as a Trust Anchor for long after the zone issues new or revokes existing RRs.

5.9. High Availability

Information about the zone administrator's view of the state of Resource Records used as Trust Anchors SHOULD be available in a trustworthy manner at all times to security-aware resolvers. Information about Resource Records that a zone administrator has invalidated and that are known to be used as Trust Anchors should be available in a trustworthy manner for a reasonable length of time.

5.10. New RR Types

If a Trust Anchor Rollover solution requires new RR types or protocol modifications, this should be considered in the evaluation of solutions. The working group needs to determine whether such changes are a good thing or a bad thing or something else.

5.11. Support for Trust Anchor Maintenance Operations

The Trust Anchor Rollover solution MUST support operations that allow a validating security-aware resolver to add a new Trust Anchor, delete an existing Trust Anchor, or replace an existing Trust Anchor with another.

5.12. Recovery from Compromise

The Trust Anchor Rollover solution MUST allow a security-aware resolver to be able to recover from the compromise of any of its configured Trust Anchors for a zone so long as at least one other key, which is known to have not been compromised, is configured as a Trust Anchor for that same zone at that resolver.

5.13. Non-Degrading Trust

The Trust Anchor Rollover solution MUST provide sufficient means to ensure authenticity and integrity so that the existing trust relation does not degrade by performing the rollover.
Top   ToC   RFC4986 - Page 9

6. Security Considerations

This document defines overall requirements for an automated specification-based Trust Anchor Rollover solution for security-aware resolvers but specifically does not define the security mechanisms needed to meet these requirements.

7. Acknowledgements

This document reflects the majority opinion of the DNSEXT Working Group members on the topic of requirements related to DNSSEC trust anchor rollover. The contributions made by various members of the working group to improve the readability and style of this document are graciously acknowledged.

8. Normative References

[1] Bradner, S., "Key Words for Use in RFCs to Indicate Requirement Levels", 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. [5] Bradner, S., "Intellectual Property Rights in IETF Technology", RFC 3979, March 2005.
Top   ToC   RFC4986 - Page 10

Authors' Addresses

Howard Eland Afilias Limited 300 Welsh Road Building 3, Suite 105 Horsham, PA 19044 USA EMail: heland@afilias.info Russ Mundy SPARTA, Inc. 7110 Samuel Morse Dr. Columbia, MD 21046 USA EMail: mundy@sparta.com Steve Crocker Shinkuro Inc. 1025 Vermont Ave, Suite 820 Washington, DC 20005 USA EMail: steve@shinkuro.com Suresh Krishnaswamy SPARTA, Inc. 7110 Samuel Morse Dr. Columbia, MD 21046 USA EMail: suresh@sparta.com
Top   ToC   RFC4986 - Page 11
Full Copyright Statement

   Copyright (C) The IETF Trust (2007).

   This document is subject to the rights, licenses and restrictions
   contained in BCP 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 in BCP 78 and BCP 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 at
   http://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.