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'1') (Obsoleted by RFC 4033, RFC 4034, RFC 4035) ** Obsolete normative reference: RFC 2541 (ref. '2') (Obsoleted by RFC 4641) ** Obsolete normative reference: RFC 3090 (ref. '3') (Obsoleted by RFC 4033, RFC 4034, RFC 4035) == Outdated reference: A later version (-12) exists of draft-ietf-dnsext-keyrr-key-signing-flag-06 == Outdated reference: A later version (-15) exists of draft-ietf-dnsext-delegation-signer-13 == Outdated reference: A later version (-09) exists of draft-ietf-dnsext-dnssec-protocol-01 Summary: 6 errors (**), 0 flaws (~~), 11 warnings (==), 2 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Individual O. Kolkman 3 Internet-Draft RIPE NCC 4 Expires: February 19, 2004 R. Gieben 5 NLnet Labs 6 August 21, 2003 8 DNSSEC key operations 9 draft-kolkman-dnssec-operational-practices-00.txt 11 Status of this Memo 13 This document is an Internet-Draft and is in full conformance with 14 all provisions of Section 10 of RFC2026. 16 Internet-Drafts are working documents of the Internet Engineering 17 Task Force (IETF), its areas, and its working groups. Note that 18 other groups may also distribute working documents as 19 Internet-Drafts. 21 Internet-Drafts are draft documents valid for a maximum of six months 22 and may be updated, replaced, or obsoleted by other documents at any 23 time. It is inappropriate to use Internet-Drafts as reference 24 material or to cite them other than as "work in progress." 26 The list of current Internet-Drafts can be accessed at http:// 27 www.ietf.org/ietf/1id-abstracts.txt. 29 The list of Internet-Draft Shadow Directories can be accessed at 30 http://www.ietf.org/shadow.html. 32 This Internet-Draft will expire on February 19, 2004. 34 Copyright Notice 36 Copyright (C) The Internet Society (2003). All Rights Reserved. 38 Abstract 40 This Internet-Draft is intended as a place holder for considerations 41 and operational practices for DNSSEC key-management. It is intended 42 to be 'long-lived' and result in documentation of best(?) current 43 practices. 45 Table of Contents 47 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 48 2. Time in DNSSEC . . . . . . . . . . . . . . . . . . . . . . . 3 49 2.1 Time definitions . . . . . . . . . . . . . . . . . . . . . . 3 50 2.2 Time considerations . . . . . . . . . . . . . . . . . . . . 4 51 3. Keys . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 52 3.1 Using Key-Signing and Zone-Signing Keys. . . . . . . . . . . 6 53 3.1.1 Motivations for the KSK and ZSK functions . . . . . . . . . 6 54 3.2 Key security considerations . . . . . . . . . . . . . . . . 6 55 3.3 Key rollovers . . . . . . . . . . . . . . . . . . . . . . . 7 56 3.3.1 Zone-signing key rollovers . . . . . . . . . . . . . . . . . 7 57 3.3.2 Key-signing key rollovers . . . . . . . . . . . . . . . . . 10 58 4. Planning for emergency key rollover. . . . . . . . . . . . . 11 59 4.1 KSK compromise . . . . . . . . . . . . . . . . . . . . . . . 12 60 4.2 ZSK compromise . . . . . . . . . . . . . . . . . . . . . . . 12 61 4.3 Compromises of keys configured at the resolver level . . . . 12 62 5. Parental policies. . . . . . . . . . . . . . . . . . . . . . 13 63 6. Initial key exchanges and parental policies 64 considerations. . . . . . . . . . . . . . . . . . . . . . . 13 65 6.1 Storing keys so hashes can be regenerated . . . . . . . . . 13 66 6.2 Self signed keys during upload or not? . . . . . . . . . . . 13 67 6.3 Security lameness checks. . . . . . . . . . . . . . . . . . 13 68 6.4 SIG DS validity period. . . . . . . . . . . . . . . . . . . 13 69 7. Resolver key configuration. . . . . . . . . . . . . . . . . 13 70 8. Security considerations . . . . . . . . . . . . . . . . . . 13 71 9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . 13 72 Normative References . . . . . . . . . . . . . . . . . . . . 14 73 Informative References . . . . . . . . . . . . . . . . . . . 14 74 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 15 75 A. Terminology . . . . . . . . . . . . . . . . . . . . . . . . 15 76 B. Zone-signing key rollover howto . . . . . . . . . . . . . . 16 77 C. Typographic conventions . . . . . . . . . . . . . . . . . . 16 78 Intellectual Property and Copyright Statements . . . . . . . 19 80 1. Introduction 82 During workshops and early operational deployment test, operators and 83 system administrators have gained knowledge about operating DNSSEC 84 aware DNS services. This document intends to document the current 85 practices and the background on why practices are as they are. 87 The structure of the document is roughly as follows. We start with 88 discussing some of the consideration with respect to timing 89 parameters of DNS in relation to DNSSEC in Section 2. Aspects of Key 90 management such as key rollover schemes are described Section 3. 91 Emergency rollover considerations are addressed in Section 4. The 92 Typographic conventions used in this document are explained in 93 Appendix C 95 Since this is a document with operational suggestions and there is no 96 protocol specifications the RFC2119 [5] language does not apply. 98 2. Time in DNSSEC 100 In pre-DNSSEC DNS all times were relative. The SOA, refresh, retry 101 and expiration timers are counters that are being used to determine 102 the time since the most recent time a slave server synced (or tried 103 to sync) with a master server. The TTL value and the SOA minimum TTL 104 parameter [6] are used to to determine how long a forwarder should 105 cache data after it has been fetched from an authoritative server. 106 DNSSEC introduces an absolute time in the DNS. Signatures in DNSSEC 107 have an expiration date after which the signature is invalid and the 108 signed data is to be considered bad. 110 2.1 Time definitions 112 In this section we will be using a number of time related terms. 113 Within the context of this document the following definitions apply: 115 o "Signature validity period" 117 The period that a signature is valid. It starts at the time 118 specified in the signature inception field of the SIG RR and 119 ends at the time specified in the expiration field of the SIG 120 RR. 122 o "Signature refresh period" 124 Time after which a signature made with a key is replaced with a 125 new signature made with the same key. This replacement takes 126 place in the master zone file. If a signature is created on 127 time T0 and a new signature is made on time T1, the signature 128 refresh time is T1 - T0. If all signatures are refreshed at 129 zone signing than the signature refresh period is equal to the 130 period between two consecutive zone signing operations. 132 o "Key usage period" 134 The period between when data signed with this key first appears 135 in the DNS and the time the authentication chain to this key is 136 broken i.e. the signature over the parental DS RR has expired 137 and this public key is not hard-configured as trusted entry 138 point into verifying resolvers. The "Key usage period" is 139 essentially the window of opportunity for cryptanalists to 140 attack a key. 142 o "Key publication period" 144 The period for which the public part of the key is published in 145 the DNS. The public part of the key can be published in the 146 DNS while it has not yet been used to sign data As soon as a 147 public key is published a brute force attack can be attempted 148 to recover the private key. Publishing the public key in 149 advance (and not signing any data with it) does not guard 150 against this attack. 152 o "Maximum/Minimum Zone TTL" 154 The maximum or minimum value of all the TTLs in your zone. 156 2.2 Time considerations 158 Because of the expiration of signatures one should consider the 159 following. 161 o The Maximum zone TTL of your zone data should be a fraction of 162 your signature validity period. 164 If the the TTL would be of similar order as the signature 165 validity period then all RRsets fetched during the validity 166 period would be cached until the signature expiration time. 167 The result would be that query behavior may become bursty. 169 We suggest the TTL on all the RRs in your zone to be at least 170 an order of magnitude smaller than your signature validity 171 period. 173 o The Minimum zone TTL should be long enough to fetch and verify all 174 the RRs in the authentication chain. 176 1. During validation, some data may expire before 177 validation is complete. The validator should be able to 178 keep all the data, until validation is complete. This 179 applies to all data in the chain of trust: DSs, DNSKEYs, 180 RRSIGs, and the final answers i.e. the RR that is returned 181 for the initial query. 183 2. Frequent re-verification causes load on recursive 184 nameserver. Data at delegation points, DS, DNSKEY and 185 RRSIGs over that those should benefit from caching. The TTL 186 on those should be relatively long. 188 We have seen events where data needed for verification of an 189 authentication chain had expired from caches. 191 We suggest the TTL on DNSKEY and DSs to be at least of the 192 order 10 minutes to an hour and all the other RRs in your zone 193 to be at least 30 seconds. [Editors note: These are initial 194 values] 196 o The signature refresh period should at least be one maximum TTL 197 smaller than the signature validity period. 199 If a zone is resigned shortly before the end of the signature 200 validity period then this may cause simultaneous expire of data 201 from caches which leads to bursty query behavior and increase 202 the load on authoritative servers. 204 o Slave servers will need to be able to fetch newly signed zones 205 well before the data expires from your zone. 207 If a properly implemented slave server is not able to contact a 208 master server for an extended period it will at some point 209 expire and not hand out any data. If the server serves a 210 DNSSEC zone than it may well happen that the signatures expire 211 well before the SOA expiration timer counted down to zero. It 212 is not possible to fully prevent this from happening by 213 tweaking the SOA parameters. But the effects can be minimized 214 if the SOA expiration time is a fraction of the signature 215 validity period. 217 When a zone cannot be updated while signatures in that zone 218 have expired non-secure resolvers will continue to be able to 219 resolve the data served by the particular slave servers. Only 220 security aware resolvers that receive data with expired 221 signatures will experience problems. 223 We suggest the SOA expiration timer being approximately one 224 third or one forth of the signature validity period. 226 We also suggest that operators of nameservers with slave zones 227 develop watchdogs to be able to spot these upcoming signature 228 expirations in slave zones, so that appropriate action can be 229 taken. 231 o [Editor's Note: Need examples here] 233 3. Keys 235 3.1 Using Key-Signing and Zone-Signing Keys. 237 3.1.1 Motivations for the KSK and ZSK functions 239 Although all data in a zone can simply be signed by one single key 240 using two keys has its advantages. Delegation Signer [7] introduced 241 the concept of key-signing and zone-signing keys while 242 Key-signing-flag [4] introduced the concept of a key with the Secure 243 Entry Point flag set; a key that is the first key from the zone when 244 following an authentication chain. When using a key-signing key with 245 the SEP flag set, where the parent has a DS RR pointing to that 246 DNSKEY, and when using zone-signing keys without the SEP flag set 247 one can use the following operational procedures. 249 The zone-signing key can be used to sign all the data in a zone on a 250 regular basis. When a zone-signing key is to be rolled over no 251 interactions with third parties are needed. This allows for 252 relatively short "Signature Validity Periods" (order of days). 254 The key-signing key (with the SEP flag set) is only to be used to 255 sign the Key RR set from the zone apex. If a key-signing key is to 256 be rolled over, there will be interactions with parties other than 257 the zone maintainer such as the registry of the parent zone or 258 administrators of verifying resolvers that have the particular key 259 configured as trusted entry points. Hence, the "Key Usage Time" of 260 these keys can and should be made much longer. Although, given a 261 long enough key, the "Key Usage Time" can be on the order of years we 262 suggest to plan for a "Key Usage Time" of the order of a few months 263 so that a key rollover remains an operational routine. 265 3.2 Key security considerations 267 In RFC2541 [2] a number of considerations with respect to the 268 security of keys are described. That document deals in detail with 269 generation, lifetime, size and storage of private keys. 271 In Section 3 of RFC2541 [2], Eastlake does make some hard number 272 suggestions: 13 months for long-lived keys and 36 days for 273 transaction keys but suggestions for key lengths are not made. 275 [Editors note: We consider keylength suggestions outside of scope for 276 this document. Wess Griffin suggested: Hilarie Orman wrote a draft 277 (orman-public-key-lengths-05, it has expired) that had some good 278 discussion of public key lengths and matching them to symmetric 279 cipher key length strengths. Also there's eastlake-randomness2-04 280 that will obsolete RFC1750 that has an appendix on symmetric key 281 lengths. Not really applicable here, but a good discussion of how to 282 choose key lengths.] 284 3.3 Key rollovers 286 Key rollovers are a fact of live when using DNSSEC. A DNSSEC key 287 cannot be used eternally (see RFC2541 [2] and Section 3.2 ). Zone 288 maintainers who are in the process of rolling their keys have to take 289 into account that data they have published in previous versions of 290 their zone still lives in caches. When deploying DNSSEC this becomes 291 an important consideration; ignoring data that may be in caches may 292 lead to loss of service for clients 294 The most pressing example of this is when zone material which is 295 signed with an old key is being validated by a resolver who does not 296 have the old zone key cached. If the old key is no longer present in 297 the current zone, this validation fails, marking the data bad. 298 Alternatively, an attempt could be made to validate data which is 299 signed with a new key against a old key that lives a a local cache, 300 also resulting in data being marked bad. 302 To appreciate the situation one could think of a number of 303 authoritative servers that may not be instantaneously running the 304 same version of a zone and a security aware non-recursive resolver 305 that sits behind security aware caching forwarders. 307 [Editors note: This needs more verbose explanation, nobody will 308 appreciate the situation just yet. Help with text and examples will 309 be appreciated] 311 3.3.1 Zone-signing key rollovers 313 For zone-signing key rollovers there are two ways to make sure that 314 during the rollover the data still in caches can be verified with the 315 new keysets or the newly generated signatures can be verified with 316 the keys still in caches. One schema uses double signatures, it is 317 described in Section 3.3.1.1, the other uses key pre-publication 318 (Section 3.3.1.2). The pros and cons and recomendations are 319 described in Section 3.3.1.3. 321 3.3.1.1 A double signature zone-signing key rollover 323 This section shows how to perform a ZSK key using the double zone 324 data signature scheme. 326 During the rollover stage the new version of the zone file will need 327 to propagate to all authoritative servers and the data that existed 328 in distant caches will need to expire, this will last at least the 329 maximum Zone TTL . 331 normal roll after 333 SOA0 SOA1 SOA2 334 SIG10(SOA0) SIG10(SOA1) SIG11(SOA2) 335 SIG11(SOA1) 337 KEY1 KEY1 KEY1 338 KEY10 KEY10 KEY11 339 KEY11 340 SIG1 (KEY) SIG1 (KEY) SIG1 (KEY) 341 SIG10(KEY) SIG10(KEY) SIG11(KEY) 342 SIG11(KEY) 344 normal: Version 0 of the zone: KEY1 is a key-signing key. Key 10 is 345 used to sign all the data of the zone, it is the zone-signing key. 347 roll: At the rollover stage (SOA serial 1) key 11 is introduced into 348 the keyset and all the data in the zone is signed with KEY 10 and 349 KEY 11. The rollover period will need to exist until all data 350 from version 0 of the zone has expired from remote caches. This 351 will take at least the maximum value of all the TTLs in the 352 version 0 of the zone. 354 after: KEY10 is removed from the zone. All the signatures from KEY10 355 are removed from the zone. The keyset, now only containing KEY11) 356 is resigned with the KEY1. 358 At every instance the data from the previous version of the zone can 359 be verified with the key from the current version. Besides, the data 360 from the current version can be verified with the data from the 361 previous version of the zone. The duration of the rollover phase and 362 the period between rollovers should be at least the "Maximum Zone 363 TTL". 365 To be on the safe side one could make sure that the rollover phase 366 lasts until the signature expiration time of the data in version 0 of 367 the zone. But this date could be considerable longer than the TTL, 368 making the rollover a lengthly procedure. 370 Note that in this example we assumed that the zone did not get 371 modified during the rollover. New data can be introduced in the zone 372 as long as it is signed with both keys. 374 3.3.1.2 Pre-publish keyset rollover 376 This section shows how to perform a ZSK key without the need to sign 377 all the data in ones zone twice. We recommend this method because it 378 has certain advantages in the case of key compromises. A small 379 "HOWTO" for this kind of rollover can be found in Appendix B. 381 normal pre-roll roll after 383 SOA0 SOA1 SOA2 SOA3 384 SIG10(SOA0) SIG10(SOA1) SIG11(SOA2) SIG11(SOA3) 386 KEY1 KEY1 KEY1 KEY1 387 KEY10 KEY10 KEY10 KEY11 388 KEY11 KEY11 389 SIG1 (KEY) SIG1 (KEY) SIG1(KEY) SIG1 (KEY) 390 SIG10(KEY) SIG10(KEY) SIG11(KEY) SIG11(KEY) 392 normal: Version 0 of the zone: KEY1 is a key-signing key. Key 10 is 393 used to sign all the data of the zone, its the zone-signing key. 395 pre-roll: Key 11 is introduced in the keyset. Note that no 396 signatures are generated with this key yet, but this will not 397 prevent brute force attacks on the public key. The minimum 398 duration of this pre-roll phase is the time it takes for the data 399 to propagate to the authoritative servers plus TTL value on the 400 keyset. [FIXME: 3 times the TTL then] 402 roll: 404 At the rollover stage (SOA serial 1) KEY 11 is used to sign the 405 data in the zone (exclusively i.e. all the signatures from KEY10 406 are removed from the zone.). KEY 10 remains published in the 407 keyset. This way data that was loaded into caches from version 1 408 of the zone can still be verified with key sets fetched from 409 version 2 of the zone. 411 The minimum time that the keyset that includes KEY 10 is to be 412 published is the time that it takes for zone data from the 413 previous version of the zone to expire from old caches i.e. the 414 time it takes for this zone to propagate to all authoritative 415 servers plus the maximum TTL value of any of the data in the 416 previous version of the zone. [FIXME: 3 times the TTL then?] 418 after: KEY10 is removed from the zone. The keyset, now only 419 containing KEY11 is resigned with the KEY1. 421 The above scheme can be simplified a bit by always publishing the 422 "future" key immediately after the rollover. The scheme would look 423 like this (we show 2 rollovers): 425 normal roll after 2nd roll 2nd after 427 SOA0 SOA2 SOA3 SOA4 SOA5 428 SIG10(SOA0) SIG11(SOA2) SIG11(SOA3) SIG12(SOA4) SIG12(SOA5) 430 KEY1 KEY1 KEY1 KEY1 KEY1 431 KEY10 KEY10 KEY11 KEY11 KEY12 432 KEY11 KEY11 KEY12 KEY12 KEY13 433 SIG1 (KEY) SIG1 (KEY) SIG1(KEY) SIG1(KEY) SIG1(KEY) 434 SIG10(KEY) SIG11(KEY) SIG11(KEY) SIG12(KEY) SIG12(KEY) 436 Note that the key introduced after the rollover is not used for 437 production yet; the private key can thus be stored in a physically 438 secure space and does not need to be 'fetched' every time a zone 439 needs to be signed. 441 This scheme has the benefit that the key that is intended for future 442 use, can immediately be used during an emergency rollover under the 443 assumption that it was stored physically secure. 445 3.3.1.3 Pros and cons of the schemes 447 A double signature rollover: The drawback of this signing scheme is 448 that during the rollover the amount of signatures in your zone 449 doubles, which may be prohibitive if you have very big zones. 451 Prepublish-keyset rollover. This rollover does not involve signing 452 the zone data twice, but before the actual rollover the new key is 453 published in the keyset and thus available for cryptanalysis 454 attacks. 456 3.3.2 Key-signing key rollovers 458 For the rollover of a key-signing key the same considerations as for 459 the rollover of a zone-signing key apply. However we can use a 460 single double signature scheme to guarantee that old data (only the 461 apex keyset) in caches can be verified with a new keyset and vice 462 verse. 464 normal roll after 466 SOA0 SOA2 SOA3 467 SIG10(SOA0) SIG11(SOA2) SIG11(SOA3) 469 KEY1 KEY1 KEY2 470 KEY2 471 KEY10 KEY10 KEY11 472 KEY11 KEY11 KEY12 473 SIG1 (KEY) SIG1 (KEY) SIG2(KEY) 474 SIG2 (KEY) 475 SIG10(KEY) SIG11(KEY) SIG11(KEY) 477 4. Planning for emergency key rollover. 479 This section deals with what one has to consider in preparation of a 480 reaction to a possible key compromise. Our advice is to have a 481 documented procedure ready for when a key compromise would ever 482 happen. 484 [Editors note: We are much in favor of a rollover tactic that keeps 485 the authentication chain intact as long as possible. This has as a 486 result that one has to take all the regular rollover properties into 487 account.] 489 When the private material of one of your keys is compromised it can 490 be used by 'blackhats' for as long as a valid authentication chain 491 exists. A authentication chain remains intact for: 493 as long as a signature over the compromised key made by another 494 key in the authentication chain is valid, 496 as long as a parental DS RR (and signature) points to the 497 compromised key, 499 as long as the key is anchored in a resolver and is used as a 500 starting point for validation. (This is hardest to update.) 502 While an authentication chain to your compromised key exists your 503 name-space is vulnerable to abuse by the "black-hat". Zone operators 504 have to make a trade off if the abuse of the compromised key is worse 505 than having data in caches that cannot be validated. If the zone 506 operator chooses to break the authentication chain to the compromised 507 key, data in caches signed with this key can not be validated. On 508 the other hand if the zone administrator chooses to take the path of 509 a regular roll-over the "black-hat" can spoof data so that it appears 510 to be valid, note that this kind of attack will usually be localized 511 in the Internet topology. 513 4.1 KSK compromise 515 When the KSK has been compromised the parent must be notified as soon 516 as possible and in a secure means. The keyset of the zone SHOULD 517 also be resigned as soon as possible. Care must be taken to not 518 break the authentication chain. The local zone can only be resigned 519 with the new KSK when the parent's zone has been updated with the new 520 KSK. Before this update takes place it would be best to drop the 521 security status of a zone all together: the parent removes the DS of 522 the child at the next zone update. After that the child can be made 523 secure again. An additional danger of a key compromise is that the 524 compromised key can be used to facilitate a legitemate key/ds and/or 525 nameserver rollover at the parent. When that happens the domain can 526 be in dispute. An out of band and secure notify mechanism to contact 527 a parent is really needed in this case. 529 4.2 ZSK compromise 531 Though not as bad as a KSK compromise mainly because there is no 532 parental interaction required. The zone must still be resigned with 533 a new ZSK as soon as possible. As this is a local operation and 534 requires no communication between the parent and child this can be 535 achieved quickly. One has to take into account though that just as 536 with a normal rollover immediate disappearance from the old 537 compromised key may lead to verification problems. The 538 pre-publication scheme as discussed above minimizes that problem. 540 4.3 Compromises of keys configured at the resolver level 542 A key can also be pre-configured in resolvers. If DNSSEC is rolled 543 out as planned the root key should be pre-configured in every secure 544 aware resolver on the planet. [Editors Note: add more about 545 authentication of a newly received resolver key] 547 If that key is compromised all the resolvers should be notified of 548 this fact. Zone administrators may consider setting up a mailing 549 list to communicate the fact that a KSK is about to be rolled over. 550 This communication will of course need to be secured e.g. by using 551 digital signatures. 553 Key must be removed as soon as possible. Non updated resolver will 554 have a problem. [Editors Note: this should be extended a bit more] 556 5. Parental policies. 558 6. Initial key exchanges and parental policies considerations. 560 6.1 Storing keys so hashes can be regenerated 562 6.2 Self signed keys during upload or not? 564 6.3 Security lameness checks. 566 6.4 SIG DS validity period. 568 Since the DS can be replayed as long as it has a valid signature a 569 short signature validity period over the DS minimizes the time a 570 child is vulnerable in the case of a compromise of the child's KSK. 571 A signature validity period that is too short introduces the 572 possibility that a zone is marked BAD in case of a configuration 573 error in the signer; there may not be enough time to fix the problems 574 before signatures expire. Something as mundane as weekends show the 575 need for a DS signature lifetimes longer than 2 days. We recommend 576 the minimum for a DS signature validity period to be about 2 days. 578 The maximum signature lifetime of the DS record depends on how long 579 child zones are willing to be vulnerable after a key compromise. We 580 consider a signature validity period of the order of a week a good 581 compromise between the operational constraints of the parent and 582 minimizing damage for the child. 584 7. Resolver key configuration. 586 Zone keys may be hard configured in resolver configurations. In case 587 of a compromise of a SEP key these "distant" resolvers will need to 588 be informed of a compromise and will need to take appropriate action. 589 A special purpose maillist on which such a compromise can be 590 announced (securely) and a set of procedures for securely publishing 591 the new SEP key should be considered. 593 8. Security considerations 595 DNSSEC adds data integrity to the DNS. This document tries to assess 596 considerations to operate a stable and secure DNSSEC service. 598 9. Acknowledgments 600 We, the folk mentioned as authors, only acted as editors. Most of 601 the ideas in this draft where the result of collective efforts during 602 workshops and discussions and try outs. 604 At the risk of forgetting individuals who where the original 605 contributors of the ideas we like to acknowledge people who where 606 actively involved in the compilation of this document. In 607 alphabetical order: Olafur Gudmundsson, Wesley Griffin. 609 Kolkman and Gieben take the blame for all mistakes. 611 Normative References 613 [1] Eastlake, D., "Domain Name System Security Extensions", RFC 614 2535, March 1999. 616 [2] Eastlake, D., "DNS Security Operational Considerations", RFC 617 2541, March 1999. 619 [3] Lewis, E., "DNS Security Extension Clarification on Zone 620 Status", RFC 3090, March 2001. 622 [4] Lewis, E., Kolkman, O. and J. Schlyter, "KEY RR Key-Signing Key 623 (KSK) Flag", draft-ietf-dnsext-keyrr-key-signing-flag-06 (work 624 in progress), February 2003. 626 Informative References 628 [5] Bradner, S., "Key words for use in RFCs to Indicate Requirement 629 Levels", BCP 14, RFC 2119, March 1997. 631 [6] Andrews, M., "Negative Caching of DNS Queries (DNS NCACHE)", RFC 632 2308, March 1998. 634 [7] Gudmundsson, O., "Delegation Signer Resource Record", 635 draft-ietf-dnsext-delegation-signer-13 (work in progress), March 636 2003. 638 [8] Arends, R., "Protocol Modifications for the DNS Security 639 Extensions", draft-ietf-dnsext-dnssec-protocol-01 (work in 640 progress), March 2003. 642 Authors' Addresses 644 Olaf M. Kolkman 645 RIPE NCC 646 Singel 256 647 Amsterdam 1016 AB 648 NL 650 Phone: +31 20 535 4444 651 EMail: olaf@ripe.net 652 URI: http://www.ripe.net/ 654 Miek Gieben 655 NLnet Labs 656 Kruislaan 419 657 Amsterdam 1098 VA 658 NL 660 EMail: miek@nlnetlabs.nl 661 URI: http://www.nlnetlabs.nl 663 Appendix A. Terminology 665 In this document there is some jargon used that is defined in other 666 documents. In most cases we have not copied the text from the 667 documents defining the terms but give a more elaborate explanation of 668 the meaning. Note that these explanations should not be seen as 669 authoritative. 671 Private and Public Keys: DNSSEC secures the DNS through the use of 672 public key cryptography. Public key cryptography is based on the 673 existence of 2 keys, a public key and a private key. The public 674 keys are published in the DNS by use of the KEY Resource Record 675 (KEY RR). Private keys are supposed to remain private i.e. 676 should not be exposed to parties not-authorized to do the actual 677 signing. 679 Signer: The system that has access to the private key material and 680 signs the Resource Record sets in a zone. A signer may be 681 configured to sign only parts of the zone e.g. only those RRsets 682 for which existing signatures are about to expire. 684 KSK: A Key-Signing key (KSK) is a key that is used for exclusively 685 signing the apex keyset. The fact that a key is a KSK is only 686 relevant to the signing tool. 688 ZSK: A Zone signing key (ZSK) is a key that is used for signing all 689 data in a zone. The fact that a key is a ZSK is only relevant to 690 the signing tool. 692 Singing Zone Rollover: The term used for the event where an 693 administrator joyfully rolls over the keys while producing melodic 694 sound patterns. 696 Appendix B. Zone-signing key rollover howto 698 Using the pre-published signature scheme and the most conservative 699 method to assure oneself that data does not live in distant caches 700 here follows the "HOWTO". [WES: has some comments about this] 702 STEP 0, the preparation: Create two keys and publish them both in 703 your keyset. Mark one of the keys as "active" and the other as 704 "published". Use the "active" key for signing your zone data. 705 Store the private part of the "published" key, preferably 706 off-line. 708 STEP 1, determine expiration: At the beginning of the rollover: 709 make a note of the highest expiration time of signatures in your 710 zonefile created with the current key currently marked as 711 "active". 713 Wait until the expiration time marked in STEP 1 715 STEP 2 Then start using the key that was marked as "published" to 716 sign your data i.e. mark it as "active". Stop using the key that 717 was marked as "active", mark it as "rolled". 719 STEP 3: It is safe to engage in a new rollover (STEP 1) after at 720 least "signature validity period". 722 Appendix C. Typographic conventions 724 The following typographic conventions are used in this document: 726 Key notation: A key is denoted by KEYx, where x is a number, x could 727 be thought of as the key id. 729 Signature notation: Signatures are denoted as SIGx(RRset), which 730 means that RRset is signed with KEYx. 732 Optionally the RRset can be written in full: SIG1(KEY1, KEY2). 733 Which is the signature made with KEY1 over the keyset containing 734 KEY1 and KEY2. 736 Zone representation: Using the above notation we have simplify the 737 representation of a signed ZONE by leaving out all unneeded 738 details such as the names and by just representing all non zone 739 apex data by "ZD" (Zone Data). 741 SOA representation: Soa's are represented as SOA x, where x is the 742 serial number. 744 Using this notation the following zone : 746 example.net. 600 IN SOA ns.example.net. ernie.example.net. ( 747 10 ; serial 748 450 ; refresh (7 minutes 30 seconds) 749 600 ; retry (10 minutes) 750 345600 ; expire (4 days) 751 300 ; minimum (5 minutes) 752 ) 753 600 SIG SOA 5 2 600 20130522213204 ( 754 20130422213204 14 example.net. 755 cmL62SI6iAX46xGNQAdQ... ) 756 600 NS a.iana-servers.net. 757 600 NS b.iana-servers.net. 758 600 SIG NS 5 2 600 20130507213204 ( 759 20130407213204 14 example.net. 760 SO5epiJei19AjXoUpFnQ ... ) 761 3600 KEY 256 3 5 ( 762 EtRB9MP5/AvOuVO0I8XDxy0... 763 ) ; key id = 14 764 3600 KEY 256 3 5 ( 765 gsPW/Yy19GzYIY+Gnr8HABU... 766 ) ; key id = 15 767 3600 SIG KEY 5 2 3600 20130522213204 ( 768 20130422213204 14 example.net. 769 J4zCe8QX4tXVGjV4e1r9... ) 770 3600 SIG KEY 5 2 3600 20130522213204 ( 771 20130422213204 15 example.net. 772 keVDCOpsSeDReyV6O... ) 773 600 NXT a.example.net. NS SOA TXT SIG KEY NXT 774 600 SIG NXT 5 2 600 20130507213204 ( 775 20130407213204 14 example.net. 776 obj3HEp1GjnmhRjX... ) 777 a.example.net. 600 IN TXT "A label" 778 600 SIG TXT 5 3 600 20130507213204 ( 779 20130407213204 14 example.net. 780 IkDMlRdYLmXH7QJnuF3v... ) 781 600 NXT b.example.com. TXT SIG NXT 782 600 SIG NXT 5 3 600 20130507213204 ( 783 20130407213204 14 example.net. 784 bZMjoZ3bHjnEz0nIsPMM... ) 786 ... 788 is reduced to the following represenation: 790 SOA10 791 SIG14(SOA10) 793 KEY14 794 KEY15 796 SIG14(KEY) 797 SIG15(KEY) 799 The rest of the zone data has the same signature as the SOA record. 801 Intellectual Property Statement 803 The IETF takes no position regarding the validity or scope of any 804 intellectual property or other rights that might be claimed to 805 pertain to the implementation or use of the technology described in 806 this document or the extent to which any license under such rights 807 might or might not be available; neither does it represent that it 808 has made any effort to identify any such rights. Information on the 809 IETF's procedures with respect to rights in standards-track and 810 standards-related documentation can be found in BCP-11. 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