Network Working Group H. Eland Internet-Draft Afilias Limited Intended status: Informational R. Mundy Expires: May 31, 2007 SPARTA, Inc. S. Crocker Shinkuro Inc. S. Krishnaswamy SPARTA, Inc. November 27, 2006 Requirements related to DNSSEC Trust Anchor Rollover draft-ietf-dnsext-rollover-requirements-04 Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. 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." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on May 31, 2007. Copyright Notice Copyright (C) The Internet Society (2006). 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 Eland, et al. Expires May 31, 2007 [Page 1] Internet-Draft DNSSEC Trust Anchor Rollover Requirements November 2006 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. Table of Contents 1 Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 3 Background . . . . . . . . . . . . . . . . . . . . . . . . . . 3 4 Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . 4 5 Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 6 5.1 Scalability . . . . . . . . . . . . . . . . . . . . . . . . 6 5.2 No Intellectual Property Encumbrance . . . . . . . . . . . 7 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 . . . . . . . . . . . . . . 8 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 . . . . . . . . . . . . . . . . . . . . 9 6 Security Considerations . . . . . . . . . . . . . . . . . . . . 9 7 IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 9 8 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 9 9 Normative References . . . . . . . . . . . . . . . . . . . . . 9 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 10 Intellectual Property and Copyright Statements . . . . . . . . . . 11 Eland, et al. Expires May 31, 2007 [Page 2] Internet-Draft DNSSEC Trust Anchor Rollover Requirements November 2006 1 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 RECOMMEND language. It is understood that a tradeoff may need to be made between requirements that both contain RFC2119 language. 2 Introduction The Domain Name System Security Extensions (DNSSEC) as described in [2] [3] and [4] defines 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 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 up- dating and managing Trust Anchors. Several mechanisms for automated specification-based approaches have been proposed to the DNS Extensions (dnsext) Working Group but each seems to be solving a somewhat different group of requirements. As a result, the Working Group determined that a requirements document needed to be developed so that each of the proposed mechanisms can be measured against a consistent set of requirements. This document provides these Trust Anchor Rollover requirements. 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 Eland, et al. Expires May 31, 2007 [Page 3] Internet-Draft DNSSEC Trust Anchor Rollover Requirements November 2006 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 DNSKEY RR or DS RR 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 operation 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 RR(s) for the root zone that will be used 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 change the Trust Anchors at the appropriate time. This 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: Eland, et al. Expires May 31, 2007 [Page 4] Internet-Draft DNSSEC Trust Anchor Rollover Requirements November 2006 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 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 operation of security-aware resolvers are responsible for determining which RRs will be used for Trust Anchors by that resolver. Initial Trust Relationship: An operator of a security-aware resolver 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 contract relationships or use other existing trust relationships outside of 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 operation and the security-aware resolver operation. 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 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. Eland, et al. Expires May 31, 2007 [Page 5] Internet-Draft DNSSEC Trust Anchor Rollover Requirements November 2006 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 security-aware resolver the exact RR(s) that have been revoked or removed so the proper Trust Anchor or Trust Anchors are removed. 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 sub-set of Trust Anchor Maintenance. Normal or Pre-Scheduled Trust Anchor Rollover: The operator of a DNSSEC signed zone has issued 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 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 useage. The probable largest number of instances of security-aware resolvers needing to rollover a Trust Anchor will be for the root zone. This number could be extremely large (possibly many millions) 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. Eland, et al. Expires May 31, 2007 [Page 6] Internet-Draft DNSSEC Trust Anchor Rollover Requirements November 2006 5.2 No Intellectual Property Encumbrance Because trust anchor rollover is likely to be "mandatory-to- implement", section 8 of [5] requires that the technology 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: world wide, irrevocable, perpetual right to use, without fee, in commerce or otherwise, where "use" includes descriptions of algorithms, 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 rollover. Implementation of the rollover protocol is likely to be mandatory, but that's out of scope for this requirements document. Eland, et al. Expires May 31, 2007 [Page 7] Internet-Draft DNSSEC Trust Anchor Rollover Requirements November 2006 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. 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 which 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. Eland, et al. Expires May 31, 2007 [Page 8] Internet-Draft DNSSEC Trust Anchor Rollover Requirements November 2006 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. 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 IANA Considerations This document has no actions for the IANA. 8 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. 9. 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. Eland, et al. Expires May 31, 2007 [Page 9] Internet-Draft DNSSEC Trust Anchor Rollover Requirements November 2006 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. 7075 Samuel Morse Dr. Columbia, MD 21046 USA Email: mundy@sparta.com Steve Crocker Shinkuro Inc. 1025 Vermont Ave Washington, DC 20005 USA Email: steve@shinkuro.com Suresh Krishnaswamy SPARTA, Inc. 7075 Samuel Morse Dr. Columbia, MD 21046 USA Email: suresh@sparta.com Eland, et al. Expires May 31, 2007 [Page 10] Internet-Draft DNSSEC Trust Anchor Rollover Requirements November 2006 Full Copyright Statement Copyright (C) The Internet Society (2006). 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. 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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. Acknowledgment Funding for the RFC Editor function is provided by the IETF Administrative Support Activity (IASA). Eland, et al. Expires May 31, 2007 [Page 11]