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'4') (Obsoleted by RFC 4033, RFC 4034, RFC 4035) == Outdated reference: A later version (-15) exists of draft-ietf-dnsext-delegation-signer-12 Summary: 4 errors (**), 0 flaws (~~), 7 warnings (==), 2 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 DNS Extensions O. Kolkman 3 Internet-Draft RIPE NCC 4 Expires: August 18, 2003 J. Schlyter 5 Carlstedt Research & 6 Technology 7 E. Lewis 8 ARIN 9 February 17, 2003 11 KEY RR Key-Signing Key (KSK) Flag 12 draft-ietf-dnsext-keyrr-key-signing-flag-06 14 Status of this Memo 16 This document is an Internet-Draft and is in full conformance with 17 all provisions of Section 10 of RFC2026. 19 Internet-Drafts are working documents of the Internet Engineering 20 Task Force (IETF), its areas, and its working groups. Note that other 21 groups may also distribute working documents as Internet-Drafts. 23 Internet-Drafts are draft documents valid for a maximum of six months 24 and may be updated, replaced, or obsoleted by other documents at any 25 time. It is inappropriate to use Internet-Drafts as reference 26 material or to cite them other than as "work in progress." 28 The list of current Internet-Drafts can be accessed at http:// 29 www.ietf.org/ietf/1id-abstracts.txt. 31 The list of Internet-Draft Shadow Directories can be accessed at 32 http://www.ietf.org/shadow.html. 34 This Internet-Draft will expire on August 18, 2003. 36 Copyright Notice 38 Copyright (C) The Internet Society (2003). All Rights Reserved. 40 Abstract 42 With the DS resource record the concept of key-signing and 43 zone-signing keys has been introduced. During key-exchanges with the 44 parent there is a need to differentiate between these zone- and 45 key-signing keys. We propose a flag to indicate which key is used as 46 key-signing key. 48 Table of Contents 50 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 51 2. The Key-Signing Key (KSK) Flag . . . . . . . . . . . . . . . . 4 52 3. DNSSEC Protocol Changes . . . . . . . . . . . . . . . . . . . 4 53 4. Operational Guidelines . . . . . . . . . . . . . . . . . . . . 4 54 5. Security Considerations . . . . . . . . . . . . . . . . . . . 5 55 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 56 7. Internationalization Considerations . . . . . . . . . . . . . 5 57 8. Document Changes . . . . . . . . . . . . . . . . . . . . . . . 6 58 8.1 draft version 00 -> 01 . . . . . . . . . . . . . . . . . . . . 6 59 8.2 draft version 01 -> 02 . . . . . . . . . . . . . . . . . . . . 6 60 8.3 draft version 02 -> 03 . . . . . . . . . . . . . . . . . . . . 6 61 8.4 draft version 03 -> 04 . . . . . . . . . . . . . . . . . . . . 6 62 8.5 draft version 04 -> 05 . . . . . . . . . . . . . . . . . . . . 6 63 8.6 draft version 05 -> 06 . . . . . . . . . . . . . . . . . . . . 7 64 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 7 65 Normative References . . . . . . . . . . . . . . . . . . . . . 7 66 Informative References . . . . . . . . . . . . . . . . . . . . 8 67 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 8 68 Intellectual Property and Copyright Statements . . . . . . . . 9 70 1. Introduction 72 "All keys are equal but some keys are more equal than others" [6] 74 With the definition of the DS Resource Record [5] the concept of a 75 key being either a key-signing key (KSK) or zone-signing key(ZSK) has 76 been introduced into DNSSEC[3]. A KSK is one that signs the zone's 77 KEY RR set, and is a key that is either used to generate a DS RR or 78 is distributed to resolvers that use the key as the root of a trusted 79 subtree[4]. 81 In early deployment tests, the use of two keys has been prevalent, 82 one key for exchange with delegating zone and the other key to sign 83 the zone. These dual roles were defined to allow a zone to more 84 rapidly change the ZSK without a high volume of traffic needed to 85 make new DS RRs. Because of this, participants have had to manage 86 two keys at all times, one acting as a KSK and the other ZSK (per 87 cryptographic algorithm). In practice, participants used a longer 88 key for the KSK or resorted to writing the footprints on paper. 90 There is a need to differentiate between a KSK and a ZSK by the zone 91 administrator. This need is driven by knowing which keys are to be 92 sent for DS RRs, which keys are to be distributed to resolvers, and 93 which keys are fed to the signer application at the appropriate time. 95 While addressing this need it is important that the distinction is 96 made in a way compatible with single key zone, those whose KSK and 97 ZSK is one in the same. The best way to address this is to define a 98 bit setting in the KEY RR flags field that is ignored in the 99 resolver. This allows for both dual key and single key management to 100 be workable. 102 The key words "MAY","MAY NOT", "MUST", "MUST NOT", "REQUIRED", 103 "RECOMMENDED", "SHOULD", and "SHOULD NOT" in this document are to be 104 interpreted as described in RFC2119. 106 2. The Key-Signing Key (KSK) Flag 108 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3 109 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 1 110 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 111 | flags |K| protocol | algorithm | 112 | |S| | | 113 | |K| | | 114 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 115 | / 116 / public key / 117 / / 118 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 120 KEY RR Format 122 The KSK bit (TBD) in the flags field is assigned to be the 123 key-signing key flag. If the the bit is set to 1 the key is intended 124 to be used as key-signing key. One SHOULD NOT assign special meaning 125 to the key if the bit is set to 0. The document proposes using the 126 current 15th bit [1] as the KSK bit. This way operators can recognize 127 the key-signing by the even or odd-ness of the decimal representation 128 of the flag field. 130 3. DNSSEC Protocol Changes 132 The bit MUST NOT be used during the resolving and verification 133 process. The KSK flag is only used to provide a hint about the 134 different administrative properties of the key and therefore the use 135 of the KSK flag does not change the DNS resolution and resolution 136 protocol. 138 4. Operational Guidelines 140 The KSK bit is set by the key-generator and used by the zone signer: 142 The KSK bit is used to indicate that the key represented in the KEY 143 RR is intended to sign the KEY RR set of the zone. As the KSK bit is 144 within the data that is used to compute a KEY RR's footprint, 145 changing the KSK bit will change the identity of the key within DNS. 147 When a key pair is created, the operator needs to indicate whether 148 the KSK bit is to be set in the KEY RR. The KSK bit is recommended 149 whenever the public key of the key pair will be distributed to the 150 parent zone to build the authentication chain or if the public key is 151 to be distributed for static configuration in verifiers. 153 When signing a zone, it is intended that the key(s) with the KSK bit 154 set (if such keys exist) are used to sign the KEY RR set of the zone. 155 The same key can be used to sign the rest of the zone data too. It 156 is conceivable that not all keys with a KSK bit set will sign the KEY 157 RR set, such keys might be pending retirement or not yet in use. 159 When verifying a RR set, the KSK bit is not intended to play a role. 160 How the key is used by the verifier is not intended to be a 161 consideration at key creation time. 163 Although the KSK flag provides a hint on which key to be used as 164 trusted root, administrators can choose to ignore the flag when 165 configuring a trusted root for their resolvers. 167 Using the flag a key roll over can be automated. The parent can use 168 an existing trust relation to verify key sets in which a new key with 169 the KSK flag appears. 171 5. Security Considerations 173 As stated in Section 3 the flag is not to used in the resolution 174 protocol or to determine the security status of a key. The flag is to 175 be used for administrative purposes only. 177 No trust in a key should be inferred from this flag - trust MUST be 178 inferred from an existing chain of trust or an out-of-band exchange. 180 Since this flag might be used for automating key exchanges, we think 181 the following consideration is in place. 183 Automated mechanisms for roll over of the DS RR might be vulnerable 184 to a class of replay attacks. This might happen after a key exchange 185 where a key set, containing two keys with the KSK flag set, is sent 186 to the parent. The parent verifies the key set with the existing 187 trust relation and creates the new DS RR from the key that the 188 current DS is not pointing to. This key exchange might be replayed. 189 Parents are encouraged to implement a replay defence. A simple 190 defence can be based on a registry of keys that have been used to 191 generate DS RRs during the most recent roll over. 193 6. IANA Considerations 195 draft-ietf-dnsext-restrict-key-for-dnssec [1] eliminates all flags 196 field except for the zone key flag in the KEY RR. We propose to use 197 the 15'th bit as the KSK bit; the decimal representation of the 198 flagfield will then be odd for key-signing keys. 200 7. Internationalization Considerations 201 There are no internationalization considerations. 203 8. Document Changes 205 8.1 draft version 00 -> 01 207 Clean up of references and correction of typos; 209 modified Abstract text a little; 211 Added explicit warning for replay attacks to the security section; 213 Removed the text that hinted on a distinction between a 214 key-signing key configured in resolvers and in parent zones. 216 8.2 draft version 01 -> 02 218 Added IANA and Internationalization section. 220 Split references into informational and normative. 222 Spelling and style corrections. 224 8.3 draft version 02 -> 03 226 Changed the name from KS to KSK, this to prevent confusion with 227 NS, DS and other acronyms in DNS. 229 In the security section: Rewrote the section so that it does not 230 suggest to use a particular type of registry and that it is clear 231 that a key registry is only one of the defences possible. 233 Spelling and style corrections. 235 8.4 draft version 03 -> 04 237 Text has been made consistent with the statement: 'No special 238 meaning should be assigned to the bit not being set.' 240 Made explicit that the keytag changes in SIG RR. 242 8.5 draft version 04 -> 05 244 One occurrence of must and one occurrence of should uppercased 245 (RFC2119). 247 Reordering of sentences in section 3, so that the point of the bit 248 NOT being used in resolving is made directly. 250 To make explicit that the KSK is used at key generation and at 251 signing time I added the first sentence to section 4. 253 Some minor style and spelling corrections. 255 8.6 draft version 05 -> 06 257 References and acronyms where stripped from the Abstract. the 258 Introduction and the the Operational Guideline section were 259 rewritten in such a way that the draft does not suggest any use of 260 the bit in the verification process and that the draft does not 261 enforce, but suggests, the use of a key- and zone-signing key. 263 Added 'and verification' in the sentence "MUST NOT be used during 264 the resolving and verification process" (protocol changes 265 section). 267 9. Acknowledgements 269 The ideas documented in this document are inspired by communications 270 we had with numerous people and ideas published by other folk. Among 271 others Mark Andrews, Olafur Gudmundsson, Daniel Karrenberg, Dan 272 Massey, Marcos Sanz and Sam Weiler have contributed ideas and 273 provided feedback. 275 This document saw the light during a workshop on DNSSEC operations 276 hosted by USC/ISI. 278 Normative References 280 [1] Massey, D. and S. Rose, "Limiting the Scope of the KEY Resource 281 Record out", draft-ietf-dnsext-restrict-key-for-dnssec-04 (work 282 in progress), September 2002. 284 [2] Bradner, S., "Key words for use in RFCs to Indicate Requirement 285 Levels", BCP 14, RFC 2119, March 1997. 287 [3] Eastlake, D., "Domain Name System Security Extensions", RFC 288 2535, March 1999. 290 [4] Lewis, E., "DNS Security Extension Clarification on Zone 291 Status", RFC 3090, March 2001. 293 Informative References 295 [5] Gudmundsson, O., "Delegation Signer Resource Record", 296 draft-ietf-dnsext-delegation-signer-12 (work in progress), 297 December 2002. 299 [6] Orwell, G. and R. Steadman (illustrator), "Animal Farm; a Fairy 300 Story"", ISBN 0151002177 (50th anniversery edition), April 1996. 302 Authors' Addresses 304 Olaf M. Kolkman 305 RIPE NCC 306 Singel 256 307 Amsterdam 1016 AB 308 NL 310 Phone: +31 20 535 4444 311 EMail: olaf@ripe.net 312 URI: http://www.ripe.net/ 314 Jakob Schlyter 315 Carlstedt Research & Technology 316 Stora Badhusgatan 18-20 317 Goteborg SE-411 21 318 Sweden 320 EMail: jakob@crt.se 321 URI: http://www.crt.se/~jakob/ 323 Edward P. Lewis 324 ARIN 325 3635 Concorde Parkway Suite 200 326 Chantilly, VA 20151 327 US 329 Phone: +1 703 227 9854 330 EMail: edlewis@arin.net 331 URI: http://www.arin.net/ 333 Intellectual Property Statement 335 The IETF takes no position regarding the validity or scope of any 336 intellectual property or other rights that might be claimed to 337 pertain to the implementation or use of the technology described in 338 this document or the extent to which any license under such rights 339 might or might not be available; neither does it represent that it 340 has made any effort to identify any such rights. 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