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'3') (Obsoleted by RFC 4033, RFC 4034, RFC 4035) ** Obsolete normative reference: RFC 3445 (ref. '4') (Obsoleted by RFC 4033, RFC 4034, RFC 4035) == Outdated reference: A later version (-15) exists of draft-ietf-dnsext-delegation-signer-14 Summary: 4 errors (**), 0 flaws (~~), 8 warnings (==), 2 comments (--).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: January 16, 2004 J. Schlyter 6 E. Lewis 7 ARIN 8 July 18, 2003 10 KEY RR Secure Entry Point (SEP) Flag 11 draft-ietf-dnsext-keyrr-key-signing-flag-08 13 Status of this Memo 15 This document is an Internet-Draft and is in full conformance with 16 all provisions of Section 10 of RFC2026. 18 Internet-Drafts are working documents of the Internet Engineering 19 Task Force (IETF), its areas, and its working groups. Note that 20 other groups may also distribute working documents as Internet- 21 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 January 16, 2004. 36 Copyright Notice 38 Copyright (C) The Internet Society (2003). All Rights Reserved. 40 Abstract 42 With the DS resource record the concept of a key acting as a secure 43 entry point has been introduced. During key-exchanges with the 44 parent there is a need to differentiate secure entry point keys from 45 other keys in the KEY resource record set. A flag bit in the KEY RR 46 is defined to indicate that KEY is to be used as a secure entry 47 point. 49 Table of Contents 51 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 52 2. The Secure Entry Point (SEP) Flag . . . . . . . . . . . . . . 4 53 3. DNSSEC Protocol Changes . . . . . . . . . . . . . . . . . . . 4 54 4. Operational Guidelines . . . . . . . . . . . . . . . . . . . . 4 55 5. Security Considerations . . . . . . . . . . . . . . . . . . . 5 56 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 57 7. Internationalization Considerations . . . . . . . . . . . . . 6 58 8. Document Changes . . . . . . . . . . . . . . . . . . . . . . . 6 59 8.1 draft version 00 -> 01 . . . . . . . . . . . . . . . . . . . . 6 60 8.2 draft version 01 -> 02 . . . . . . . . . . . . . . . . . . . . 6 61 8.3 draft version 02 -> 03 . . . . . . . . . . . . . . . . . . . . 6 62 8.4 draft version 03 -> 04 . . . . . . . . . . . . . . . . . . . . 7 63 8.5 draft version 04 -> 05 . . . . . . . . . . . . . . . . . . . . 7 64 8.6 draft version 05 -> 06 . . . . . . . . . . . . . . . . . . . . 7 65 8.7 draft version 06 -> 07 . . . . . . . . . . . . . . . . . . . . 7 66 8.8 draft version 07 -> 08 . . . . . . . . . . . . . . . . . . . . 7 67 9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 8 68 Normative References . . . . . . . . . . . . . . . . . . . . . 8 69 Informative References . . . . . . . . . . . . . . . . . . . . 8 70 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 9 71 Full Copyright Statement . . . . . . . . . . . . . . . . . . . 10 73 1. Introduction 75 "All keys are equal but some keys are more equal than others" [6] 77 With the definition of the DS Resource Record [5] it has become 78 important to differentiate between the zone keys that are (to be) 79 pointed to by parental DS RRs and other keys in the zone. We refer 80 to these keys as Secure Entry Point (SEP) keys. A SEP key is either 81 used to generate a DS RR or is distributed to resolvers that use the 82 key as the root of a trusted subtree[3]. 84 In early deployment tests, the use of two (kinds of) keys in each 85 zone has been prevalent. One key is used to sign just the zone's KEY 86 RR set and is the key referenced by a DS RR at the parent or 87 configured statically in a resolver. Another key is used to sign the 88 rest of the zone's data sets. The former key is called a key-signing 89 key (KSK) and the latter is called a zone-signing key (ZSK). In 90 practice there have been usually one of each kind of key, but there 91 will be multiples of each at times. 93 It should be noted that division of zone keys into KSK's and ZSK's is 94 not mandatory in any definition of DNSSEC, not even with the 95 introduction of the DS RR. But, in testing, this distinction has 96 been helpful when designing key roll over (key super-cession) 97 schemes. Given that the distinction has proven helpful, the labels 98 KSK and ZSK have begun to stick. 100 There is a need to differentiate between a KSK and a ZSK by the zone 101 administrator. This need is driven by knowing which keys are to be 102 sent for DS RRs, which keys are to be distributed to resolvers, and 103 which keys are fed to the signer application at the appropriate time. 105 The reason for the term "SEP" is a result of the observation that the 106 distinction between KSK and ZSK is only significant to the signer 107 element of the DNS. Servers, resolvers and verifiers do not need to 108 make the distinction. Further, distinguishing between a KSK and ZSK 109 requires more than one bit, as a key could be fulfilling both roles. 110 Hence, there is no definition for a ZSK bit and another for a KSK 111 bit, just a single bit to assist operational procedures to correctly 112 generate DS RRs, or to indicate what keys are intended for static 113 configuration. 115 In the flow between signer and (parental) key-collector and in the 116 flow between the signer and the resolver configuration it is 117 important to be able to differentiate the SEP keys from the other 118 keys in a KEY RR set. The SEP flag is to be of no interest to the 119 flow between the verifier and the authoritative data store. 121 The key words "MAY","MAY NOT", "MUST", "MUST NOT", "REQUIRED", 122 "RECOMMENDED", "SHOULD", and "SHOULD NOT" in this document are to be 123 interpreted as described in RFC2119. 125 2. The Secure Entry Point (SEP) Flag 127 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3 128 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 1 129 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 130 | flags |S| protocol | algorithm | 131 | |E| | | 132 | |P| | | 133 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 134 | / 135 / public key / 136 / / 137 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 139 KEY RR Format 141 The SEP bit (TBD) in the flags field is assigned to be the secure 142 entry point flag. If the the bit is set to 1 the key is intended to 143 be used as secure entry point key. One SHOULD NOT assign special 144 meaning to the key if the bit is set to 0. The document proposes 145 using the current 15th bit [4] as the SEP bit. This way operators 146 can recognize the secure entry point key by the even or odd-ness of 147 the decimal representation of the flag field. 149 3. DNSSEC Protocol Changes 151 The bit MUST NOT be used during the resolving and verification 152 process. The SEP flag is only used to provide a hint about the 153 different administrative properties of the key and therefore the use 154 of the SEP flag does not change the DNS resolution and resolution 155 protocol. 157 4. Operational Guidelines 159 The SEP bit is set by the key-generator and MAY be used by the zone 160 signer to decide whether the key is to be prepared for input to a DS 161 RR generation function. As the SEP bit is within the data that is 162 used to compute a KEY RR's footprint, changing the SEP bit will 163 change the identity of the key within DNS. 165 When a key pair is created, the operator needs to indicate whether 166 the SEP bit is to be set in the KEY RR. The SEP bit is recommended 167 whenever the public key of the key pair will be distributed to the 168 parent zone to build the authentication chain or if the public key is 169 to be distributed for static configuration in verifiers. 171 When signing a zone, it is intended that the key(s) with the SEP bit 172 set (if such keys exist) are used to sign the KEY RR set of the zone. 173 The same key can be used to sign the rest of the zone data too. It 174 is conceivable that not all keys with a SEP bit set will sign the KEY 175 RR set, such keys might be pending retirement or not yet in use. 177 When verifying a RR set, the SEP bit is not intended to play a role. 178 How the key is used by the verifier is not intended to be a 179 consideration at key creation time. 181 Although the SEP flag provides a hint on which key to be used as 182 trusted root, administrators can choose to ignore the fact that a KEY 183 has its SEP bit set or not when configuring a trusted root for their 184 resolvers. 186 Using the flag a key roll over can be automated. The parent can use 187 an existing trust relation to verify key sets in which a new key with 188 the SEP flag appears. 190 5. Security Considerations 192 As stated in Section 3 the flag is not to used in the resolution 193 protocol or to determine the security status of a key. The flag is 194 to be used for administrative purposes only. 196 No trust in a key should be inferred from this flag - trust MUST be 197 inferred from an existing chain of trust or an out-of-band exchange. 199 Since this flag might be used for automating key exchanges, we think 200 the following consideration is in place. 202 Automated mechanisms for roll over of the DS RR might be vulnerable 203 to a class of replay attacks. This might happen after a key exchange 204 where a key set, containing two keys with the SEP flag set, is sent 205 to the parent. The parent verifies the key set with the existing 206 trust relation and creates the new DS RR from the key that the 207 current DS is not pointing to. This key exchange might be replayed. 208 Parents are encouraged to implement a replay defense. A simple 209 defense can be based on a registry of keys that have been used to 210 generate DS RRs during the most recent roll over. These same 211 considerations apply to entities that configure keys in resolvers. 213 6. IANA Considerations 215 draft-ietf-dnsext-restrict-key-for-dnssec [4] eliminates all flags 216 field except for the zone key flag in the KEY RR. We propose to use 217 the 15'th bit as the SEP bit; the decimal representation of the 218 flagfield will then be odd for key-signing keys. 220 7. Internationalization Considerations 222 Although SEP is a popular acronym in many different languages, there 223 are no internationalization considerations. 225 8. Document Changes 227 8.1 draft version 00 -> 01 229 Clean up of references and correction of typos; 231 modified Abstract text a little; 233 Added explicit warning for replay attacks to the security section; 235 Removed the text that hinted on a distinction between a key- 236 signing key configured in resolvers and in parent zones. 238 8.2 draft version 01 -> 02 240 Added IANA and Internationalization section. 242 Split references into informational and normative. 244 Spelling and style corrections. 246 8.3 draft version 02 -> 03 248 Changed the name from KS to KSK, this to prevent confusion with 249 NS, DS and other acronyms in DNS. 251 In the security section: Rewrote the section so that it does not 252 suggest to use a particular type of registry and that it is clear 253 that a key registry is only one of the defenses possible. 255 Spelling and style corrections. 257 8.4 draft version 03 -> 04 259 Text has been made consistent with the statement: ' No special 260 meaning should be assigned to the bit not being set.' 262 Made explicit that the key tag changes in SIG RR. 264 8.5 draft version 04 -> 05 266 One occurrence of must and one occurrence of should uppercased 267 (RFC2119). 269 Reordering of sentences in section 3, so that the point of the bit 270 NOT being used in resolving is made directly. 272 To make explicit that the KSK is used at key generation and at 273 signing time I added the first sentence to section 4. 275 Some minor style and spelling corrections. 277 8.6 draft version 05 -> 06 279 References and acronyms where stripped from the Abstract. the 280 Introduction and the the Operational Guideline section were 281 rewritten in such a way that the draft does not suggest any use of 282 the bit in the verification process and that the draft does not 283 enforce, but suggests, the use of a key- and zone-signing key. 285 Added 'and verification' in the sentence "MUST NOT be used during 286 the resolving and verification process" (protocol changes 287 section). 289 8.7 draft version 06 -> 07 291 Based on comments during the last call we changed the name from 292 KSK-flag to SEP flag. The introduction was rewritten to reflect 293 the motivations of this name change and to stress that the SEP key 294 is not relevant to the signer process. 296 8.8 draft version 07 -> 08 298 During the edit of version 07, a paragraph got dropped from the 299 introduction (See message by Lewis dd June 19, subject " Fwd: Re: 300 NOTIFY + SIG(0) + DS => secure parent update?" (http:// 301 ops.ietf.org/lists/nhamedroppers/namedroppers.2003/msg01336.html). 302 This version re-introduces the paragraph, which caused some 303 reordering and style changes in the introduction. 305 9. Acknowledgments 307 The ideas documented in this document are inspired by communications 308 we had with numerous people and ideas published by other folk. Among 309 others Mark Andrews, Miek Gieben, Olafur Gudmundsson, Daniel 310 Karrenberg, Dan Massey, Marcos Sanz and Sam Weiler have contributed 311 ideas and provided feedback. 313 This document saw the light during a workshop on DNSSEC operations 314 hosted by USC/ISI. 316 Normative References 318 [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement 319 Levels", BCP 14, RFC 2119, March 1997. 321 [2] Eastlake, D., "Domain Name System Security Extensions", RFC 322 2535, March 1999. 324 [3] Lewis, E., "DNS Security Extension Clarification on Zone 325 Status", RFC 3090, March 2001. 327 [4] Massey, D. and S. Rose, "Limiting the Scope of the KEY Resource 328 Record (RR)", RFC 3445, December 2002. 330 Informative References 332 [5] Gudmundsson, O., "Delegation Signer Resource Record", draft- 333 ietf-dnsext-delegation-signer-14 (work in progress), May 2003. 335 [6] Orwell, G. and R. Steadman (illustrator), "Animal Farm; a Fairy 336 Story"", ISBN 0151002177 (50th anniversery edition), April 1996. 338 Authors' Addresses 340 Olaf M. Kolkman 341 RIPE NCC 342 Singel 256 343 Amsterdam 1016 AB 344 NL 346 Phone: +31 20 535 4444 347 EMail: olaf@ripe.net 348 URI: http://www.ripe.net/ 350 Jakob Schlyter 351 Karl Gustavsgatan 15 352 Goteborg SE-411 25 353 Sweden 355 EMail: jakob@schlyter.se 357 Edward P. Lewis 358 ARIN 359 3635 Concorde Parkway Suite 200 360 Chantilly, VA 20151 361 US 363 Phone: +1 703 227 9854 364 EMail: edlewis@arin.net 365 URI: http://www.arin.net/ 367 Full Copyright Statement 369 Copyright (C) The Internet Society (2003). All Rights Reserved. 371 This document and translations of it may be copied and furnished to 372 others, and derivative works that comment on or otherwise explain it 373 or assist in its implementation may be prepared, copied, published 374 and distributed, in whole or in part, without restriction of any 375 kind, provided that the above copyright notice and this paragraph are 376 included on all such copies and derivative works. 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