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diff --git a/doc/rfc/rfc3757.txt b/doc/rfc/rfc3757.txt new file mode 100644 index 0000000..31890a4 --- /dev/null +++ b/doc/rfc/rfc3757.txt @@ -0,0 +1,451 @@ + + + + + + +Network Working Group O. Kolkman +Request for Comments: 3757 RIPE NCC +Updates: 3755, 2535 J. Schlyter +Category: Standards Track NIC-SE + E. Lewis + ARIN + April 2004 + + + Domain Name System KEY (DNSKEY) Resource Record (RR) + Secure Entry Point (SEP) Flag + +Status 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 Internet Society (2004). All Rights Reserved. + +Abstract + + With the Delegation Signer (DS) resource record (RR), the concept of + a public key acting as a secure entry point (SEP) has been + introduced. During exchanges of public keys with the parent there is + a need to differentiate SEP keys from other public keys in the Domain + Name System KEY (DNSKEY) resource record set. A flag bit in the + DNSKEY RR is defined to indicate that DNSKEY is to be used as a SEP. + The flag bit is intended to assist in operational procedures to + correctly generate DS resource records, or to indicate what DNSKEYs + are intended for static configuration. The flag bit is not to be + used in the DNS verification protocol. This document updates RFC + 2535 and RFC 3755. + + + + + + + + + + + + + + +Kolkman, et al. Standard Track [Page 1] + +RFC 3757 DNSKEY RR SEP Flag April 2004 + + +Table of Contents + + 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2 + 2. The Secure Entry Point (SEP) Flag. . . . . . . . . . . . . . . 4 + 3. DNSSEC Protocol Changes. . . . . . . . . . . . . . . . . . . . 4 + 4. Operational Guidelines . . . . . . . . . . . . . . . . . . . . 4 + 5. Security Considerations. . . . . . . . . . . . . . . . . . . . 5 + 6. IANA Considerations. . . . . . . . . . . . . . . . . . . . . . 6 + 7. Internationalization Considerations. . . . . . . . . . . . . . 6 + 8. Acknowledgments. . . . . . . . . . . . . . . . . . . . . . . . 6 + 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6 + 9.1. Normative References . . . . . . . . . . . . . . . . . . 6 + 9.2. Informative References . . . . . . . . . . . . . . . . . 6 + 10. Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 7 + 11. Full Copyright Statement . . . . . . . . . . . . . . . . . . . 8 + +1. Introduction + + "All keys are equal but some keys are more equal than others" [6]. + + With the definition of the Delegation Signer Resource Record (DS RR) + [5], it has become important to differentiate between the keys in the + DNSKEY RR set that are (to be) pointed to by parental DS RRs and the + other keys in the DNSKEY RR set. We refer to these public keys as + Secure Entry Point (SEP) keys. A SEP key either used to generate a + DS RR or is distributed to resolvers that use the key as the root of + a trusted subtree [3]. + + In early deployment tests, the use of two (kinds of) key pairs for + each zone has been prevalent. For one kind of key pair the private + key is used to sign just the zone's DNSKEY resource record (RR) set. + Its public key is intended to be referenced by a DS RR at the parent + or configured statically in a resolver. The private key of the other + kind of key pair is used to sign the rest of the zone's data sets. + The former key pair is called a key-signing key (KSK) and the latter + is called a zone-signing key (ZSK). In practice there have been + usually one of each kind of key pair, but there will be multiples of + each at times. + + It should be noted that division of keys pairs into KSK's and ZSK's + is not mandatory in any definition of DNSSEC, not even with the + introduction of the DS RR. But, in testing, this distinction has + been helpful when designing key roll over (key super-cession) + schemes. Given that the distinction has proven helpful, the labels + KSK and ZSK have begun to stick. + + + + + + +Kolkman, et al. Standard Track [Page 2] + +RFC 3757 DNSKEY RR SEP Flag April 2004 + + + There is a need to differentiate the public keys for the key pairs + that are used for key signing from keys that are not used key signing + (KSKs vs ZSKs). This need is driven by knowing which DNSKEYs are to + be sent for generating DS RRs, which DNSKEYs are to be distributed to + resolvers, and which keys are fed to the signer application at the + appropriate time. + + In other words, the SEP bit provides an in-band method to communicate + a DNSKEY RR's intended use to third parties. As an example we + present 3 use cases in which the bit is useful: + + The parent is a registry, the parent and the child use secured DNS + queries and responses, with a preexisting trust-relation, or plain + DNS over a secured channel to exchange the child's DNSKEY RR sets. + Since a DNSKEY RR set will contain a complete DNSKEY RRset the SEP + bit can be used to isolate the DNSKEYs for which a DS RR needs to + be created. + + An administrator has configured a DNSKEY as root for a trusted + subtree into security aware resolver. Using a special purpose + tool that queries for the KEY RRs from that domain's apex, the + administrator will be able to notice the roll over of the trusted + anchor by a change of the subset of KEY RRs with the DS flag set. + + A signer might use the SEP bit on the public key to determine + which private key to use to exclusively sign the DNSKEY RRset and + which private key to use to sign the other RRsets in the zone. + + As demonstrated in the above examples it is important to be able to + differentiate the SEP keys from the other keys in a DNSKEY RR set in + the flow between signer and (parental) key-collector and in the flow + between the signer and the resolver configuration. The SEP flag is + to be of no interest to the flow between the verifier and the + authoritative data store. + + The reason for the term "SEP" is a result of the observation that the + distinction between KSK and ZSK key pairs is made by the signer, a + key pair could be used as both a KSK and a ZSK at the same time. To + be clear, the term SEP was coined to lessen the confusion caused by + the overlap. (Once this label was applied, it had the side effect of + removing the temptation to have both a KSK flag bit and a ZSK flag + bit.) + + The key words "MAY","MAY NOT", "MUST", "MUST NOT", "REQUIRED", + "RECOMMENDED", "SHOULD", and "SHOULD NOT" in this document are to be + interpreted as described in BCP 14, RFC 2119 [1]. + + + + + +Kolkman, et al. Standard Track [Page 3] + +RFC 3757 DNSKEY RR SEP Flag April 2004 + + +2. The Secure Entry Point (SEP) Flag + + 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3 + 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | flags |S| protocol | algorithm | + | |E| | | + | |P| | | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | / + / public key / + / / + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + + DNSKEY RR Format + This document assigns the 15th bit in the flags field as the secure + entry point (SEP) bit. If the bit is set to 1 the key is intended to + be used as secure entry point key. One SHOULD NOT assign special + meaning to the key if the bit is set to 0. Operators can recognize + the secure entry point key by the even or odd-ness of the decimal + representation of the flag field. + +3. DNSSEC Protocol Changes + + The bit MUST NOT be used during the resolving and verification + process. The SEP flag is only used to provide a hint about the + different administrative properties of the key and therefore the use + of the SEP flag does not change the DNS resolution protocol or the + resolution process. + +4. Operational Guidelines + + The SEP bit is set by the key-pair-generator and MAY be used by the + zone signer to decide whether the public part of the key pair is to + be prepared for input to a DS RR generation function. The SEP bit is + recommended to be set (to 1) whenever the public key of the key pair + will be distributed to the parent zone to build the authentication + chain or if the public key is to be distributed for static + configuration in verifiers. + + When a key pair is created, the operator needs to indicate whether + the SEP bit is to be set in the DNSKEY RR. As the SEP bit is within + the data that is used to compute the 'key tag field' in the SIG RR, + changing the SEP bit will change the identity of the key within DNS. + In other words, once a key is used to generate signatures, the + setting of the SEP bit is to remain constant. If not, a verifier + will not be able to find the relevant KEY RR. + + + + +Kolkman, et al. Standard Track [Page 4] + +RFC 3757 DNSKEY RR SEP Flag April 2004 + + + When signing a zone, it is intended that the key(s) with the SEP bit + set (if such keys exist) are used to sign the KEY RR set of the zone. + The same key can be used to sign the rest of the zone data too. It + is conceivable that not all keys with a SEP bit set will sign the + DNSKEY RR set, such keys might be pending retirement or not yet in + use. + + When verifying a RR set, the SEP bit is not intended to play a role. + How the key is used by the verifier is not intended to be a + consideration at key creation time. + + Although the SEP flag provides a hint on which public key is to be + used as trusted root, administrators can choose to ignore the fact + that a DNSKEY has its SEP bit set or not when configuring a trusted + root for their resolvers. + + Using the SEP flag a key roll over can be automated. The parent can + use an existing trust relation to verify DNSKEY RR sets in which a + new DNSKEY RR with the SEP flag appears. + +5. Security Considerations + + As stated in Section 3 the flag is not to be used in the resolution + protocol or to determine the security status of a key. The flag is + to be used for administrative purposes only. + + No trust in a key should be inferred from this flag - trust MUST be + inferred from an existing chain of trust or an out-of-band exchange. + + Since this flag might be used for automating public key exchanges, we + think the following consideration is in place. + + Automated mechanisms for roll over of the DS RR might be vulnerable + to a class of replay attacks. This might happen after a public key + exchange where a DNSKEY RR set, containing two DNSKEY RRs with the + SEP flag set, is sent to the parent. The parent verifies the DNSKEY + RR set with the existing trust relation and creates the new DS RR + from the DNSKEY RR that the current DS RR is not pointing to. This + key exchange might be replayed. Parents are encouraged to implement + a replay defense. A simple defense can be based on a registry of + keys that have been used to generate DS RRs during the most recent + roll over. These same considerations apply to entities that + configure keys in resolvers. + + + + + + + + +Kolkman, et al. Standard Track [Page 5] + +RFC 3757 DNSKEY RR SEP Flag April 2004 + + +6. IANA Considerations + + IANA has assigned the 15th bit in the DNSKEY Flags Registry (see + Section 4.3 of [4]) as the Secure Entry Point (SEP) bit. + +7. Internationalization Considerations + + Although SEP is a popular acronym in many different languages, there + are no internationalization considerations. + +8. Acknowledgments + + The ideas documented in this document are inspired by communications + we had with numerous people and ideas published by other folk. Among + others Mark Andrews, Rob Austein, Miek Gieben, Olafur Gudmundsson, + Daniel Karrenberg, Dan Massey, Scott Rose, Marcos Sanz and Sam Weiler + have contributed ideas and provided feedback. + + This document saw the light during a workshop on DNSSEC operations + hosted by USC/ISI in August 2002. + +9. References + +9.1. Normative References + + [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement + Levels", BCP 14, RFC 2119, March 1997. + + [2] Eastlake, D., "Domain Name System Security Extensions", RFC + 2535, March 1999. + + [3] Lewis, E., "DNS Security Extension Clarification on Zone + Status", RFC 3090, March 2001. + + [4] Weiler, S., "Legacy Resolver Compatibility for Delegation Signer + (DS)", RFC 3755, April 2004. + +9.2. Informative References + + [5] Gudmundsson, O., "Delegation Signer (DS) Resource Record (RR)", + RFC 3658, December 2003. + + [6] Orwell, G. and R. Steadman (illustrator), "Animal Farm; a Fairy + Story", ISBN 0151002177 (50th anniversary edition), April 1996. + + + + + + + +Kolkman, et al. Standard Track [Page 6] + +RFC 3757 DNSKEY RR SEP Flag April 2004 + + +10. Authors' Addresses + + Olaf M. Kolkman + RIPE NCC + Singel 256 + Amsterdam 1016 AB + NL + + Phone: +31 20 535 4444 + EMail: olaf@ripe.net + URI: http://www.ripe.net/ + + + Jakob Schlyter + NIC-SE + Box 5774 + SE-114 87 Stockholm + Sweden + + EMail: jakob@nic.se + URI: http://www.nic.se/ + + + Edward P. Lewis + ARIN + 3635 Concorde Parkway Suite 200 + Chantilly, VA 20151 + US + + Phone: +1 703 227 9854 + EMail: edlewis@arin.net + URI: http://www.arin.net/ + + + + + + + + + + + + + + + + + + + +Kolkman, et al. Standard Track [Page 7] + +RFC 3757 DNSKEY RR SEP Flag April 2004 + + +11. Full Copyright Statement + + Copyright (C) The Internet Society (2004). 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 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. + +Acknowledgement + + Funding for the RFC Editor function is currently provided by the + Internet Society. + + + + + + + + + +Kolkman, et al. Standard Track [Page 8] + |