DNSOP G. Guette Internet-Draft IRISA / INRIA Expires: February 5, 2005 O. Courtay Thomson R&D August 7, 2004 Requirements for Automated Key Rollover in DNSSEC draft-ietf-dnsop-key-rollover-requirements-01.txt Status of this Memo By submitting this Internet-Draft, I certify that any applicable patent or other IPR claims of which I am aware have been disclosed, and any of which I become aware will be disclosed, in accordance with RFC 3668. 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 February 5, 2005. Copyright Notice Copyright (C) The Internet Society (2004). All Rights Reserved. Abstract This document describes problems that appear during an automated rollover and gives the requirements for the design of communication between parent zone and child zone in an automated rollover process. This document is essentially about key rollover, the rollover of another Resource Record present at delegation point (NS RR) is also discussed. Guette & Courtay Expires February 5, 2005 [Page 1] Internet-Draft Automated Rollover Requirements August 2004 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. The Key Rollover Process . . . . . . . . . . . . . . . . . . . 3 3. Basic Requirements . . . . . . . . . . . . . . . . . . . . . . 4 4. Messages authentication and information exchanged . . . . . . 4 5. Emergency Rollover . . . . . . . . . . . . . . . . . . . . . . 5 6. Other Resource Record concerned by automatic rollover . . . . 5 7. Security consideration . . . . . . . . . . . . . . . . . . . . 5 8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 5 9. Normative References . . . . . . . . . . . . . . . . . . . . . 5 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 6 Intellectual Property and Copyright Statements . . . . . . . . 7 Guette & Courtay Expires February 5, 2005 [Page 2] Internet-Draft Automated Rollover Requirements August 2004 1. Introduction The DNS security extensions (DNSSEC) [4][8][7][9] uses public-key cryptography and digital signatures. It stores the public part of keys in DNSKEY Resource Records (RRs). Because old keys and frequently used keys are vulnerable, they must be renewed periodically. In DNSSEC, this is the case for Zone Signing Keys (ZSKs) and Key Signing Keys (KSKs) [1][2]. Automation of key rollover process is necessary for large zones because there are too many changes to handle a manual administration. Let us consider for example a zone with 100000 secure delegations. If the child zones change their keys once a year on average, that implies 300 changes per day for the parent zone. This amount of changes are hard to manage manually. Automated rollover is optional and resulting from an agreement between the administrator of the parent zone and the administrator of the child zone. Of course, key rollover can also be done manually by administrators. This document describes the requirements for the design of messages of automated key rollover process and focusses on interaction between parent and child zone. 2. The Key Rollover Process Key rollover consists in renewing the DNSSEC keys used to sign resource records in a given DNS zone file. There are two types of rollover, ZSK rollovers and KSK rollovers. In a ZSK rollover, all changes are local to the zone that renews its key: there is no need to contact other zones (e.g., parent zone) to propagate the performed changes because a ZSK has no associated DS record in the parent zone. In a KSK rollover, new DS RR(s) must be created and stored in the parent zone. In consequence, the child zone must contact its parent zone and must notify it about the KSK change(s). Manual key rollover exists and works [3]. The key rollover is built from two parts of different nature: o An algorithm that generates new keys and signs the zone file. It could be local to the zone o The interaction between parent and child zones One example of manual key rollover is: Guette & Courtay Expires February 5, 2005 [Page 3] Internet-Draft Automated Rollover Requirements August 2004 o The child zone creates a new KSK o The child zone waits for the creation of the DS RR in its parent zone o The child zone deletes the old key. In manual rollover, communications are managed by the zone administrators and the security of these communications is out of scope of DNSSEC. Automated key rollover should use a secure communication between parent and child zones. This document concentrates on defining interactions between entities present in key rollover process. 3. Basic Requirements The main constraint to respect during a key rollover is that the chain of trust MUST be preserved, even if a resolver retrieves some RRs from recursive cache server. Every RR MUST be verifiable at any time, every RRs exchanged during the rollover should be authenticated and their integrity should be guaranteed. Two entities act during a KSK rollover: the child zone and its parent zone. These zones are generally managed by different administrators. These administrators should agree on some parameters like availability of automated rollover, the maximum delay between notification of changes in the child zone and the resigning of the parent zone. The child zone needs to know this delay to schedule its changes. 4. Messages authentication and information exchanged Every exchanged message MUST be authenticated and the authentication tool MUST be a DNSSEC tool such as TSIG [6], SIG(0) [5] or DNSSEC request with verifiable SIG records. Once the changes related to a KSK are made in a child zone, this zone MUST notify its parent zone in order to create the new DS RR and store this DS RR in parent zone file. The parent zone MUST receive all the child keys that needs the creation of associated DS RRs in the parent zone. Some errors could occur during transmission between child zone and parent zone. Key rollover solution MUST be fault tolerant, i.e. at any time the rollover MUST be in a consistent state and all RRs MUST be verifiable, even if an error occurs. That is to say that it MUST remain a valid chain of trust. Guette & Courtay Expires February 5, 2005 [Page 4] Internet-Draft Automated Rollover Requirements August 2004 5. Emergency Rollover A key of a zone might be compromised and this key MUST be changed as soon as possible. Fast changes could break the chain of trust. The part of DNS tree having this zone as apex can become unverifiable, but the break of the chain of trust is necessary if we want to no one can use the compromised key to spoof DNS data. In case of emergency rollover, the administrators of parent and child zones should create new key(s) and DS RR(s) as fast as possible in order to reduce the time the chain of trust is broken. 6. Other Resource Record concerned by automatic rollover NS records are also present at delegation point, so when the child zone renews some NS RR, the corresponding records at delegation point in parent zone (glue) MUST be updated. NS records are concerned by rollover and this rollover could be automated too. In this case, when the child zone notifies its parent zone that some NS records have been changed, the parent zone MUST verify that these NS records are present in child zone before doing any changes in its own zone file. This allows to avoid inconsistency between NS records at delegation point and NS records present in the child zone. 7. Security consideration This document describes requirements to design an automated key rollover in DNSSEC based on DNSSEC security. In the same way, as plain DNSSEC, the automatic key rollover contains no mechanism protecting against denial of service (DoS). The security level obtain after an automatic key rollover, is the security level provided by DNSSEC. 8. Acknowledgments The authors want to acknowledge Francis Dupont, Mohsen Souissi, Bernard Cousin, Bertrand L‰onard and members of IDsA project for their contribution to this document. 9 Normative References [1] Gudmundsson, O., "Delegation Signer (DS) Resource Record (RR)", RFC 3658, December 2003. [2] Kolkman, O., Schlyter, J. and E. Lewis, "Domain Name System KEY (DNSKEY) Resource Record (RR) Secure Entry Point (SEP) Flag", RFC 3757, May 2004. Guette & Courtay Expires February 5, 2005 [Page 5] Internet-Draft Automated Rollover Requirements August 2004 [3] Kolkman, O., "DNSSEC Operational Practices", draft-ietf-dnsop-dnssec-operational-practice-01 (work in progress), May 2004. [4] Eastlake, D., "Domain Name System Security Extensions", RFC 2535, March 1999. [5] Eastlake, D., "DNS Request and Transaction Signatures ( SIG(0)s)", RFC 2931, September 2000. [6] Vixie, P., Gudmundsson, O., Eastlake, D. and B. Wellington, "Secret Key Transaction Authentication for DNS (TSIG)", RFC 2845, May 2000. [7] Arends, R., "Resource Records for the DNS Security Extensions", draft-ietf-dnsext-dnssec-records-09 (work in progress), July 2004. [8] Arends, R., Austein, R., Massey, D., Larson, M. and S. Rose, "DNS Security Introduction and Requirements", draft-ietf-dnsext-dnssec-intro-11 (work in progress), July 2004. [9] Arends, R., "Protocol Modifications for the DNS Security Extensions", draft-ietf-dnsext-dnssec-protocol-07 (work in progress), July 2004. Authors' Addresses Gilles Guette IRISA / INRIA Campus de Beaulieu 35042 Rennes CEDEX FR EMail: gilles.guette@irisa.fr URI: http://www.irisa.fr Olivier Courtay Thomson R&D 1, avenue Belle Fontaine 35510 Cesson S‰vign‰ CEDEX FR EMail: olivier.courtay@thomson.net Guette & Courtay Expires February 5, 2005 [Page 6] Internet-Draft Automated Rollover Requirements August 2004 Intellectual Property Statement 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. 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