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Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year == The document seems to use 'NOT RECOMMENDED' as an RFC 2119 keyword, but does not include the phrase in its RFC 2119 key words list. -- The document date (May 03, 2014) is 3645 days in the past. Is this intentional? Checking references for intended status: Informational ---------------------------------------------------------------------------- == Outdated reference: A later version (-06) exists of draft-ietf-dnsop-dnssec-key-timing-03 Summary: 0 errors (**), 0 flaws (~~), 3 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 dnsop W. Kumari 3 Internet-Draft Google 4 Intended status: Informational O. Gudmundsson 5 Expires: November 04, 2014 Shinkuro Inc. 6 G. Barwood 8 May 03, 2014 10 Automating DNSSEC Delegation Trust Maintenance 11 draft-ietf-dnsop-delegation-trust-maintainance-13 13 Abstract 15 This document describes a method to allow DNS operators to more 16 easily update DNSSEC Key Signing Keys using the DNS as communication 17 channel. The technique described is aimed at delegations in which it 18 is currently hard to move information from the child to parent. 20 Status of This Memo 22 This Internet-Draft is submitted in full conformance with the 23 provisions of BCP 78 and BCP 79. 25 Internet-Drafts are working documents of the Internet Engineering 26 Task Force (IETF). Note that other groups may also distribute 27 working documents as Internet-Drafts. The list of current Internet- 28 Drafts is at http://datatracker.ietf.org/drafts/current/. 30 Internet-Drafts are draft documents valid for a maximum of six months 31 and may be updated, replaced, or obsoleted by other documents at any 32 time. It is inappropriate to use Internet-Drafts as reference 33 material or to cite them other than as "work in progress." 35 This Internet-Draft will expire on November 04, 2014. 37 Copyright Notice 39 Copyright (c) 2014 IETF Trust and the persons identified as the 40 document authors. All rights reserved. 42 This document is subject to BCP 78 and the IETF Trust's Legal 43 Provisions Relating to IETF Documents 44 (http://trustee.ietf.org/license-info) in effect on the date of 45 publication of this document. Please review these documents 46 carefully, as they describe your rights and restrictions with respect 47 to this document. Code Components extracted from this document must 48 include Simplified BSD License text as described in Section 4.e of 49 the Trust Legal Provisions and are provided without warranty as 50 described in the Simplified BSD License. 52 Table of Contents 54 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 55 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4 56 1.2. Requirements Notation . . . . . . . . . . . . . . . . . . 4 57 2. Background . . . . . . . . . . . . . . . . . . . . . . . . . 4 58 2.1. DNS Delegations . . . . . . . . . . . . . . . . . . . . . 4 59 2.2. Relationship Between Parent and Child DNS Operator . . . 5 60 2.2.1. Solution Space . . . . . . . . . . . . . . . . . . . 6 61 2.2.2. DNSSEC key change process . . . . . . . . . . . . . . 6 62 3. CDS / CDNSKEY (Child DS / Child DNSKEY) Record Definitions . 7 63 3.1. CDS Resource Record Format . . . . . . . . . . . . . . . 7 64 3.2. CDNSKEY Resource Record Format . . . . . . . . . . . . . 8 65 4. Automating DS Maintenance With CDS / CDNSKEY records . . . . 8 66 4.1. CDS / CDNSKEY Processing Rules . . . . . . . . . . . . . 8 67 5. CDS / CDNSKEY Publication . . . . . . . . . . . . . . . . . . 9 68 6. Parent Side CDS / CDNSKEY Consumption . . . . . . . . . . . . 9 69 6.1. Detecting a Changed CDS / CDNSKEY . . . . . . . . . . . . 9 70 6.1.1. CDS / CDNSKEY Polling . . . . . . . . . . . . . . . . 10 71 6.1.2. Polling Triggers . . . . . . . . . . . . . . . . . . 10 72 6.2. Using the New CDS / CDNSKEY Records . . . . . . . . . . . 11 73 6.2.1. Parent Calculates DS . . . . . . . . . . . . . . . . 11 74 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12 75 8. Privacy Considerations . . . . . . . . . . . . . . . . . . . 12 76 9. Security Considerations . . . . . . . . . . . . . . . . . . . 12 77 10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 14 78 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 14 79 11.1. Normative References . . . . . . . . . . . . . . . . . . 14 80 11.2. Informative References . . . . . . . . . . . . . . . . . 14 81 Appendix A. RRR background . . . . . . . . . . . . . . . . . . . 15 82 Appendix B. CDS key rollover example . . . . . . . . . . . . . . 16 83 Appendix C. Changes / Author Notes. . . . . . . . . . . . . . . 17 84 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 21 86 1. Introduction 88 The first time a DNS operator signs a zone, they need to communicate 89 the keying material to their parent through some out-of-band method 90 to complete the chain of trust. Depending on the desires of the 91 parent, the child might send their DNSKEY record, a DS record, or 92 both. 94 Each time the child changes the key that is represented in the 95 parent, the updated and / or deleted key information has to be 96 communicated to the parent and published in the parent's zone. How 97 this information is sent to the parent depends on the relationship 98 the child has with the parent. In many cases this is a manual 99 process, and not an easy one. For each key change, there may be up 100 to two interactions with the parent. Any manual process is 101 susceptible to mistakes and / or errors. In addition, due to the 102 annoyance factor of the process, operators may avoid changing keys or 103 skip needed steps to publish the new DS at the parent. 105 DNSSEC provides data integrity to information published in DNS; thus 106 DNS publication can be used to automate maintenance of delegation 107 information. This document describes a method to automate 108 publication of subsequent DS records, after the initial one has been 109 published. 111 Readers are expected to be familiar with DNSSEC, including [RFC4033], 112 [RFC4034], [RFC4035], [RFC5011] and [RFC6781]. 114 This document is a compilation of two earlier drafts: draft-barwood- 115 dnsop-ds-publish[I-D.ds-publish] and draft-wkumari-dnsop-ezkeyroll. 117 This document outlines a technique in which the parent periodically 118 (or upon request) polls its signed children and automatically 119 publishes new DS records. To a large extent, the procedures this 120 document follows are as described in [RFC6781] section 4.1.2. 122 This technique is designed to be friendly both to fully automated 123 tools and humans. Fully automated tools can perform all the actions 124 needed without human intervention, and thus can monitor when it is 125 safe to move to the next step. 127 The solution described in this document only allows transferring 128 information about DNSSEC keys (DS and DNSKEY) from the child to the 129 parental agent. It lists exactly what the parent should publish, and 130 allows for publication of stand-by keys. A different protocol, 131 [I-D.csync], can be used to maintain other important delegation 132 information, such as NS and glue. These two protocols have been kept 133 as separate solutions because the problems are fundamentally 134 different, and a combined solution is overly complex. 136 This document describes a method for automating maintenance of the 137 delegation trust information, and proposes a polled / periodic 138 trigger for simplicity. Some users may prefer a different trigger, 139 for example a button on a webpage, a REST interface or a DNS NOTIFY. 140 These alternate / additional triggers are not discussed in this 141 document. 143 This proposal does not include all operations needed for the 144 maintenance of DNSSEC key material, specifically the initial 145 introduction or complete removal of all keys. Because of this, 146 alternate communications mechanisms must always exist, potentially 147 introducing more complexity. 149 1.1. Terminology 151 The terminology we use is defined in this section. 153 Highlighted roles: 155 o Child: "The entity on record that has the delegation of the domain 156 from the parent" 158 o Parent: "The domain in which the child is registered" 160 o Child DNS Operator: "The entity that maintains and publishes the 161 zone information for the child DNS" 163 o Parental Agent: "The entity that the child has relationship with, 164 to change its delegation information" 166 o Provisioning system: "A system that the operator of the master DNS 167 server operates to maintain the information published in the DNS. 168 This includes the systems that sign the DNS data" 170 1.2. Requirements Notation 172 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 173 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 174 document are to be interpreted as described in [RFC2119]. 176 2. Background 178 2.1. DNS Delegations 180 DNS operation consists of delegations of authority. For each 181 delegation there are (most of the time) two parties: the parent and 182 the child. 184 The parent publishes information about the delegations to the child; 185 for the name servers it publishes an NS [RFC1035] RRset that lists a 186 hint for name servers that are authoritative for the child. The 187 child also publishes a NS RRset, and this set is the authoritative 188 list of name servers to the child zone. 190 The second RRset the parent sometimes publishes is the DS [RFC4034] 191 set. The DS RRset provides information about the DNSKEY(s) that the 192 child has told the parent it will use to sign its DNSKEY RRset. In 193 DNSSEC trust relationship between zones is provided by the following 194 chain: 196 parent DNSKEY --> DS --> child DNSKEY. 198 A prior proposal [I-D.auto-cpsync] suggested that the child send an 199 "update" to the parent via a mechanism similar to Dynamic Update. 200 The main issue became: How does the child find the actual parental 201 agent/server to send the update to? While that could have been 202 solved via technical means, it failed to reach consensus. There is 203 also a similar proposal in [I-D.parent-zones]. 205 As the DS record can only be present at the parent ( [RFC4034]), some 206 other method is needed to automate which DNSKEYs are picked to be 207 represented in the parent zone's DS records. One possibility is to 208 use flags in the DNSKEY record. If the SEP bit is set, this 209 indicates that the DNSKEY is intended for use as a secure entry 210 point. This DNSKEY signs the DNSKEY RRset, and the Parental Agent 211 can calculate DS records based on that. But this fails to meet some 212 operating needs, including the child having no influence what DS 213 digest algorithms are used and DS records can only be published for 214 keys that are in the DNSKEY RRset, and thus this technique would not 215 be compatible with Double-DS ( [RFC6781] ) key rollover. 217 2.2. Relationship Between Parent and Child DNS Operator 219 In practical application, there are many different relationships 220 between the parent and Child DNS Operators. The type of relationship 221 affects how the Child DNS Operator communicates with the parent. 222 This section will highlight some of the different situations, but is 223 by no means a complete list. 225 Different communication paths: 227 o Direct/API: The child can change the delegation information via 228 automated/scripted means. EPP[RFC5730], used by many TLDs is an 229 example of this. Other examples are web-based programmatic 230 interfaces that Registrars make available to their Resellers. 232 o User Interface: The Child uses a (web) site set up by the Parental 233 Agent for updating delegation information. 235 o Indirect: The communication has to be transmitted via out-of-band 236 between two parties, such as by email or telephone. This is 237 common when the Child's DNS operator is neither the child itself 238 nor the Registrar for the domain but a third party. 240 o Multi-step Combinations: The information flows through an 241 intermediary. It is possible, but unlikely, that all the steps 242 are automated via API's and there are no humans involved. 244 A domain name holder (Child) may operate its own DNS servers or 245 outsource the operation. While we use the word parent as a singular, 246 parent can consist of single entity or a composite of many discrete 247 parts that have rules and roles. We refer to the entity that the 248 child corresponds with as the Parent. 250 An organization (such as an enterprise) may delegate parts of its 251 name-space to be operated by a group that is not the same as that 252 which operates the organization's DNS servers. In some of these 253 cases the flow of information is handled in either an ad hoc manner 254 or via some corporate mechanism; this can range from email to fully- 255 automated operation. 257 2.2.1. Solution Space 259 This document is aimed at the cases in which there is a separation 260 between the child and parent. 262 A further complication is when the Child DNS Operator is not the 263 Child. There are two common cases of this: 265 a) The Parental Agent (e.g. registrar) handles the DNS operation. 267 b) A third party takes care of the DNS operation. 269 If the Parental Agent is the DNS operator, life is much easier; the 270 Parental Agent can inject any delegation changes directly into the 271 Parent's Provisioning system. The techniques described below are not 272 needed in the case when Parental Agent is the DNS operator. 274 In the case of a third party DNS operator, the Child either needs to 275 relay changes in DNS delegation or give the Child DNS Operator access 276 to its delegation/registration account. 278 Some parents want the child to express their DNSKEYs in the form of 279 DS records, while others want to receive the DNSKEY records and 280 calculate the DS records themselves. There is no consensus on which 281 method is better; both have good reasons to exist. This solution is 282 DS vs DNSKEY agnostic, and allows operation with either. 284 2.2.2. DNSSEC key change process 286 After a Child DNS Operator first signs the zone, there is a need to 287 interact with the Parent, for example via a delegation account 288 interface, to "upload / paste-in the zone's DS information". This 289 action of logging in through the delegation account user interface 290 authenticates that the user is authorized to change delegation 291 information for the child published in the parent zone. In the case 292 where the Child DNS Operator does not have access to the registration 293 account, the Child needs to perform the action. 295 At a later date, the Child DNS Operator may want to publish a new DS 296 record in the parent, either because they are changing keys, or 297 because they want to publish a stand-by key. This involves 298 performing the same process as before. Furthermore when this is a 299 manual process with cut and paste, operational mistakes will happen 300 -- or worse, the update action is not performed at all. 302 The Child DNS Operator may also introduce new keys, and can do so 303 when old keys exist and can be used. The Child may also remove old 304 keys, but this document does not support removing all keys. This is 305 to avoid making signed zones unsigned. The Child may not enroll the 306 initial key or introduce a new key when there are no old keys that 307 can be used (without some additional, out of band, validation of the 308 keys), because there is no way to validate the information. 310 3. CDS / CDNSKEY (Child DS / Child DNSKEY) Record Definitions 312 This document specifies two new DNS resource records, CDS and 313 CDNSKEY. These records are used to convey, from one zone to its 314 parent, the desired contents of the zone's DS resource record set 315 residing in the parent zone. 317 The CDS / CDNSKEY resource records are published in the child zone 318 and gives the child control of what is published for it in the 319 parental zone. The CDS / CDNSKEY RRset expresses what the child 320 would like the DS RRset to look like after the change; it is a 321 "replace" operation, and it is up to the consumer of the records to 322 translate that into the appropriate add/delete operations in the 323 provisioning systems (and in the case of CDNSKEY, to generate the DS 324 from the DNSKEY). If no CDS / CDNSKEY RRset is present in child, 325 this means that no change is needed. 327 [[RFC Editor: Please remove this paragraph before publication] 328 Version -04 of the ID that became this working group document (http:/ 329 /tools.ietf.org/id/draft-kumari-ogud-dnsop-cds-04.txt) defined a new 330 record (CTA) that could hold either a DS or a DNSKEY record (with a 331 selector to differentiate between them). In a shocking development, 332 there was almost full consensus that this was horrid :-) ] 334 3.1. CDS Resource Record Format 335 The wire and presentation format of the CDS ("Child DS") resource 336 record is identical to the DS record [RFC4034]. IANA has allocated 337 RR code 59 for the CDS resource record via expert review 338 [I-D.ds-publish]. The CDS RR uses the same registries as DS for its 339 fields. 341 No special processing is performed by authoritative servers or by 342 revolvers, when serving or resolving. For all practical purposes CDS 343 is a regular RR type. 345 3.2. CDNSKEY Resource Record Format 347 The wire and presentation format of the CDNSKEY ("Child DNSKEY") 348 resource record is identical to the DNSKEY record. IANA has 349 allocated RR code TBA1 for the CDNSKEY resource record via expert 350 review. The CDNSKEY RR uses the same registries as DNSKEY for its 351 fields. 353 No special processing is performed by authoritative servers or by 354 revolvers, when serving or resolving. For all practical purposes 355 CDNSKEY is a regular RR type. 357 4. Automating DS Maintenance With CDS / CDNSKEY records 359 CDS / CDNSKEY resource records are intended to be "consumed" by 360 delegation trust maintainers. The use of CDS / CDNSKEY is optional. 362 The child SHOULD publish both CDS and CDNSKEY resource records. If 363 the child knows which the parent consumes, it MAY choose to only 364 publish that record type (for example, some children wish the parent 365 to publish a DS, but they wish to keep the DNSKEY "hidden" until 366 needed). If the child publishes both, the two RRsets MUST match in 367 content. 369 4.1. CDS / CDNSKEY Processing Rules 371 If there are no CDS / CDNSKEY RRset in the child, this signals that 372 no change should be made to the current DS set. This means that, 373 once the child and parent are in sync, the Child DNS Operator MAY 374 remove all CDS and CDNSKEY resource records from the zone. The Child 375 DNS Operator may choose to do this to decrease the size of the zone, 376 or to decrease the workload for the parent (if the parent receives no 377 CDS / CDNSKEY records it can go back to sleep). If it does receive a 378 CDS or CDNSKEY RRset it needs to check them against what is currently 379 published - see Section 5. 381 Following acceptance rules are placed on the CDS / CDNSKEY resource 382 records as follows: 384 o Location: the CDS / CDNSKEY resource records MUST be at the child 385 zone apex. 387 o Signer: MUST be signed with a key that is represented in both the 388 current DNSKEY and DS RRsets (unless the parent uses the CDS / 389 CDNSKEY RRset for initial enrollment, in that case the parent 390 validates the CDS / CDNSKEY through some other means (see 391 Section 6.1 and the Security Considerations.) 393 o Continuity: MUST NOT break the current delegation if applied to DS 394 RRset. 396 If any these conditions fail the CDS / CDNSKEY resource record MUST 397 be ignored. 399 5. CDS / CDNSKEY Publication 401 Child DNS Operator publishes CDS and / or CDNSKEY resource records. 402 In order to be valid, the CDS / CDNSKEY RRset MUST be compliant with 403 the rules in Section 4.1. When the Parent DS is "in sync" with the 404 CDS / CDNSKEY resource records, the Child DNS Operator MAY delete the 405 CDS / CDNSKEY record(s); the child can determine if this is the case 406 by querying for DS records in the parent. 408 6. Parent Side CDS / CDNSKEY Consumption 410 The CDS / CDNSKEY RRset SHOULD be used by the Parental Agent to 411 update the DS RRset in the parent zone. The Parental Agent for this 412 uses a tool that understands the CDS / CDNSKEY signing rules from 413 Section 4.1 so it might not be able to use a standard validator. 415 The parent MUST choose to use either CDNSKEY or CDS resource records 416 as their default updating mechanism. The parent MAY only accept 417 either CDNSKEY or CDS, but it MAY also accept both, so it can use the 418 other in the absence of the default updating mechanism, but it MUST 419 NOT expect there to be both. 421 6.1. Detecting a Changed CDS / CDNSKEY 423 How the Parental Agent gets the CDS / CDNSKEY RRset may differ, below 424 are two examples as how this can take place. 426 Polling The Parental Agent operates a tool that periodically checks 427 each of the children that has a DS record to see if there is a 428 CDS or CDNSKEY RRset. 430 Pushing The delegation user interface has a button {Fetch DS} when 431 pushed performs the CDS / CDNSKEY processing. If the Parent 432 zone does not contain DS for this delegation then the "push" 433 SHOULD be ignored. If the Parental Agent displays the contents 434 of the CDS / CDSNKEY to the user and gets confirmation that 435 this represents their key, the Parental Agent MAY use this for 436 initial enrollment (when the Parent zone does not contain the 437 DS for this delegation). 439 In either case the Parental Agent MAY apply additional rules that 440 defer the acceptance of a CDS / CDNSKEY change, these rules may 441 include a condition that the CDS / CDNSKEY remains in place and valid 442 for some time period before it is accepted. It may be appropriate in 443 the "Pushing" case to assume that the Child is ready and thus accept 444 changes without delay. 446 6.1.1. CDS / CDNSKEY Polling 448 This is the only defined use of CDS / CDNSKEY resource records in 449 this document. There are limits to the scalability of polling 450 techniques, thus some other mechanism is likely to be specified later 451 that addresses CDS / CDNSKEY resource record usage in the situation 452 where polling does not scale to. Having said that, Polling will work 453 in many important cases such as enterprises, universities and smaller 454 TLDs. In many regulatory environments the registry is prohibited 455 from talking to the registrant. In most of these cases the 456 registrant has a business relationship with the registrar, and so the 457 registrar can offer this as a service. 459 If the CDS / CDNSKEY RRset does not exist, the Parental Agent MUST 460 take no action. Specifically it MUST NOT delete or alter the 461 existing DS RRset. 463 6.1.2. Polling Triggers 465 It is assumed that other mechanisms will be implemented to trigger 466 the parent to look for an updated CDS / CDNSKEY RRsets. As the CDS / 467 CDNSKEY resource records are validated with DNSSEC, these mechanisms 468 can be unauthenticated. As an example, a child could telephone its 469 parent and request that they process the new CDS or CDNSKEY resource 470 records or an unauthenticated POST could be made to a webserver (with 471 rate-limiting). 473 Other documents can specify the trigger conditions. 475 6.2. Using the New CDS / CDNSKEY Records 477 Regardless of how the Parental Agent detected changes to a CDS / 478 CDNSKEY RRset, the Parental Agent SHOULD use a DNSSEC validator to 479 obtain a validated CDS / CDNSKEY RRset from the Child zone. A NOT 480 RECOMMENDED exception to this is if the parent performs some 481 additional validation on the data to confirm that it is the "correct" 482 key. 484 The Parental Agent MUST ensure that previous versions of the CDS / 485 CDNSKEY RRset do not overwrite more recent versions. This MAY be 486 accomplished by checking that the signature inception in the RRSIG 487 for CDS / CDNSKEY RRset is later and / or the serial number on the 488 child's SOA is greater. This may require the Parental Agent to 489 maintain some state information. 491 The Parental Agent MAY take extra security measures. For example, to 492 mitigate the possibility that a Child's key signing key has been 493 compromised, the Parental Agent may, for example, inform (by email or 494 other methods) the Child DNS Operator of the change. However the 495 precise out-of-band measures that a parent zone SHOULD take are 496 outside the scope of this document. 498 Once the Parental Agent has obtained a valid CDS / CDNSKEY RRset it 499 MUST check the publication rules from section 4.1. In particular the 500 Parental Agent MUST check the Continuity rule and do its best not to 501 invalidate the Child zone. Once checked and if the information in 502 the CDS / CDNSKEY and DS differ it may apply the changes to the 503 parent zone. If the parent consumes CDNSKEY, the parent should 504 calculate the DS before doing this comparison. 506 6.2.1. Parent Calculates DS 508 There are cases where the Parent wants to calculate the DS record due 509 to policy reasons. In this case, the Child publishes CDNSKEY records 510 and the parent calculates the DS records on behalf of the children. 512 When a Parent operates in "calculate DS" mode it can operate in one 513 of two sub-modes: 515 full: it only publishes DS records it calculates from DNSKEY 516 records, 518 augment: it will make sure there are DS records for the digest 519 algorithm(s) it requires(s). 521 In the case where the parent fetches the CDNSKEY RRset and calculates 522 the DS it MAY be the case that the DS published in the parent zone is 523 not identical with the data in the CDS resource record made available 524 by the child. 526 7. IANA Considerations 528 IANA has assigned RR Type code 59 for the CDS resource record. This 529 was done for an earlier version of this document[I-D.ds-publish] This 530 document is to become the reference for CDS RRtype. 532 IANA is requested to assign another RR Type for the CDNSKEY, and to 533 replace TBA1 with this value (currently 60 is still free, it would be 534 nice if that were assigned...) 536 8. Privacy Considerations 538 All of the information handled / transmitted by this protocol is 539 public information published in the DNS. 541 9. Security Considerations 543 This work is for the normal case; when things go wrong there is only 544 so much that automation can fix. 546 If child breaks DNSSEC validation by removing all the DNSKEYs that 547 are represented in the DS set its only repair actions are to contact 548 the parent or restore the DNSKEYs in the DS set. 550 In the event of a compromise of the server or system generating 551 signatures for a zone, an attacker might be able to generate and 552 publish new CDS / CDNSKEY resource records. The modified CDS / 553 CDNSKEY records will be picked up by this technique and so may allow 554 the attacker to extend the effective time of his attack. If there is 555 a delay in accepting changes to DS, as in [RFC5011], then the 556 attacker needs to hope his activity is not detected before the DS in 557 the parent is changed. If this type of change takes place, the child 558 needs to contact the parent (possibly via a registrar web interface) 559 and remove any compromised DS keys. 561 A compromise of the account with the parent (e.g. registrar) will not 562 be mitigated by this technique, as the "new registrant" can delete / 563 modify the DS records at will. 565 While it may be tempting, this SHOULD NOT be used for initial 566 enrollment of keys since there is no way to ensure that the initial 567 key is the correct one. If is used, strict rules for inclusion of 568 keys such as hold down times, challenge data inclusion or similar, 569 ought to be used, along with some kind of challenge mechanism. A 570 child cannot use this mechanism to go from signed to unsigned 571 (publishing an empty CDS / CDNSKEY RRset means no-change should be 572 made in the parent). 574 The CDS RR type should allow for enhanced security by simplifying 575 process. Since key change is automated, updating a DS RRset by other 576 means may be regarded as unusual and subject to extra security 577 checks. 579 As this introduces a new mechanism to update information in the 580 parent it MUST be clear who is fetching the records and creating the 581 appropriate records in the parent zone. Specifically some operations 582 may use other mechanisms than what is described here. For example, a 583 registrar may assume that it is maintaining the DNSSEC key 584 information in the registry, and may have this cached. If the 585 registry is fetching the CDS / CDNSKEY RRset then the registry and 586 registrar may have different views of the DNSSEC key material and the 587 result of such a situation is unclear. Therefore, this mechanism 588 SHOULD NOT be use to bypass intermediaries that might cache 589 information and because of that get the wrong state. 591 If there is a failure in applying changes in the child zone to all 592 DNS servers listed in either parent or child NS set it is possible 593 that the Parental agent may get confused, either because it gets 594 different answers on different checks or CDS RR validation fails. In 595 the worst case, the Parental Agent performs an action reversing a 596 prior action but after the child signing system decides to take the 597 next step in the key change process, resulting in a broken 598 delegation. 600 DNS is a loosely coherent distributed database with local caching; 601 therefore, it is important to allow old information to expire from 602 caches before deleting DS or DNSKEY records. Similarly, it is 603 important to allow new records to propagate through the DNS before 604 use, see [RFC6781] and [I-D.key-time] 606 It is common practice for users to outsource their DNS hosting to a 607 third-party DNS provider. In order for that provider to be able to 608 maintain the DNSSEC information some users give the provider their 609 registrar login credentials (which obviously has negative security 610 implications). Deploying the solution described in this document 611 allows the 3rd party DNS provider to maintain the DNSSEC information 612 without giving them the registrar credentials, thereby improving 613 security. 615 By automating the maintenance of the DNSSEC key information (and 616 removing humans from the process), we expect to decrease the number 617 of DNSSEC related outages, which should increase DNSSEC deployment. 619 10. Acknowledgements 621 We would like to thank a large number of folk, including: Mark 622 Andrews, Joe Abley, Jaap Akkerhuis, Roy Arends, Doug Barton, Brian 623 Dickson, Paul Ebersman, Tony Finch, Jim Galvin, Paul Hoffman, Samir 624 Hussain, Tatuya Jinmei, Olaf Kolkman, Stephan Lagerholm, Cricket Liu, 625 Matt Larson, Marco Sanz, Antoin Verschuren, Suzanne Woolf, Paul 626 Wouters, John Dickinson, Timothe Litt and Edward Lewis. 628 Special thanks to Wes Hardaker for contributing significant text and 629 creating the complementary (CSYNC) solution, and to Patrik Faltstrom, 630 Paul Hoffman, Matthijs Mekking, Mukund Sivaraman and Jeremy C. Reed 631 for text and in-depth review. 633 There were a number of other folk with whom we discussed this, 634 apologies for not remembering everyone. 636 11. References 638 11.1. Normative References 640 [RFC1035] Mockapetris, P., "Domain names - implementation and 641 specification", STD 13, RFC 1035, November 1987. 643 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 644 Requirement Levels", BCP 14, RFC 2119, March 1997. 646 [RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S. 647 Rose, "DNS Security Introduction and Requirements", RFC 648 4033, March 2005. 650 [RFC4034] Arends, R., Austein, R., Larson, M., Massey, D., and S. 651 Rose, "Resource Records for the DNS Security Extensions", 652 RFC 4034, March 2005. 654 [RFC4035] Arends, R., Austein, R., Larson, M., Massey, D., and S. 655 Rose, "Protocol Modifications for the DNS Security 656 Extensions", RFC 4035, March 2005. 658 [RFC5011] StJohns, M., "Automated Updates of DNS Security (DNSSEC) 659 Trust Anchors", STD 74, RFC 5011, September 2007. 661 [RFC6781] Kolkman, O., Mekking, W., and R. Gieben, "DNSSEC 662 Operational Practices, Version 2", RFC 6781, December 663 2012. 665 11.2. Informative References 667 [I-D.auto-cpsync] 668 Mekking, W., "Automated (DNSSEC) Child Parent 669 Synchronization using DNS UPDATE", draft-mekking-dnsop- 670 auto-cpsync-01 (work in progress), December 2010. 672 [I-D.csync] 673 Hardaker, W., "Child To Parent Synchronization in DNS", 674 draft-hardaker-dnsop-csync-02 (work in progress), July 675 2013. 677 [I-D.ds-publish] 678 Barwood, G., "DNS Transport", draft-barwood-dnsop-ds- 679 publish-02 (work in progress), June 2011. 681 [I-D.key-time] 682 Mekking, W., "DNSSEC Key Timing Considerations", draft- 683 ietf-dnsop-dnssec-key-timing-03 (work in progress), July 684 2012. 686 [I-D.parent-zones] 687 Andrews, M., "Updating Parent Zones", draft-andrews-dnsop- 688 update-parent-zones-04 (work in progress), November 2013. 690 [RFC5730] Hollenbeck, S., "Extensible Provisioning Protocol (EPP)", 691 STD 69, RFC 5730, August 2009. 693 [RFC5910] Gould, J. and S. Hollenbeck, "Domain Name System (DNS) 694 Security Extensions Mapping for the Extensible 695 Provisioning Protocol (EPP)", RFC 5910, May 2010. 697 Appendix A. RRR background 699 RRR is our shorthand for Registry/Registrar/Registrant model of 700 parent child relationship. 702 In the RRR world, the different parties are frequently from different 703 organizations. In the single enterprise world there are also 704 organizational / geographical / cultural separations that affect how 705 information flows from a Child to the parent. 707 Due to the complexity of the different roles and interconnections, 708 automation of delegation information has not yet occurred. There 709 have been proposals to automate this, in order to improve the 710 reliability of the DNS. These proposals have not gained enough 711 traction to become standards. 713 For example in many of the TLD cases there is the RRR model 714 (Registry, Registrar and Registrant). The Registry operates DNS for 715 the TLD, the Registrars accept registrations and place information 716 into the Registries database. The Registrant only communicates with 717 the Registrar; frequently the Registry is not allowed to communicate 718 with the Registrant. In that case as far as the registrant is 719 concerned the Registrar is the same entity as the Parent. 721 In many RRR cases the Registrar and Registry communicate via 722 EPP[RFC5730] and use the EPP DNSSEC extension [RFC5910]. In a number 723 of ccTLDs there are other mechanisms in use as well as EPP, but in 724 general there seems to be a movement towards EPP usage when DNSSEC is 725 enabled in the TLD. 727 Appendix B. CDS key rollover example 729 This section shows an example on how CDS is used when performing a 730 KSK rollover, this example will demonstrate the the double DS 731 rollover method from section 4.1.2 in [RFC6781]. Other rollovers 732 using CDNSKEY and double KSK are left as an exersize to the reader. 733 The table below does not reflect the ZSK keys as they are not 734 material during KSK rollovers. The wait states below are highlight 735 what RRset needs to expire from caches before progressign to the next 736 step. 738 +-------+---------------+----------+---------+------------+---------+ 739 | Step | State | Parent | Child | DNSKEY and | Child | 740 | | | DS | KSK | CDS signer | CDS | 741 +-------+---------------+----------+---------+------------+---------+ 742 | 0 | Beginning | A | A | A | | 743 | 1 | Add CDS | A | A | A | AB | 744 | 2 | Wait for DS | A | A | A | AB | 745 | | change | | | | | 746 | 3 | Updated DS | AB | A | A | AB | 747 | 4 | wait > DS TTL | AB | A | A | AB | 748 | 5 | Actual | AB | B | B | AB | 749 | | Rollover | | | | | 750 | 6 | wait > DNSKEY | AB | B | B | AB | 751 | | TTL | | | | | 752 | 7 | Cleanup | AB | B | B | B | 753 | | starts | | | | | 754 | 8 | Parent | B | B | B | B | 755 | | updates | | | | | 756 | 9 | Optional CDS | B | B | B | | 757 | | delete | | | | | 758 +-------+---------------+----------+---------+------------+---------+ 760 Table 1: States 762 End text 764 Appendix C. Changes / Author Notes. 766 [RFC Editor: Please remove this section before publication ] 768 WG-12 to WG-13 770 o Added appendix B showing Key rollover using CDS. 772 WG-11 to WG-12 774 o Many nits and helpful grammar fixes from Jeremy C. Reed. 776 WG-10 to WG-11 778 o More useful text from Matthijs. 780 o Explained why the child might want to remove the CDS / CDNSKEY 781 Records. 783 WG-09 to WG-10 785 o Incorporated off list comments from Stephan Lagerholm. Largest 786 change is fixing discrepancy between parent MAY perform OOB 787 validation and the Signer rule in 4.1. Clarified by updating 788 signer rule to allow enrolment if validation is performed OOB. 790 WG-08 to WG-09 792 o New text from Paul Hoffman for the first paragraph of the intro. 794 o And a modification from Jaap. 796 WG-07 to WG-08 798 o Incorporated text from Antoin Verschuren at the end of Section 6. 800 o Comments from Paul Hoffman and Tim W 802 WG-06 to WG-07 804 o Incorporated nits / editorial comments from Tim Wicinski. 806 o 808 * Reference for Mark's draft was incorrect, Wes Hardaker doesn't 809 work for ISC :-P 811 * Normalized CDS record / CDS resource record / records / etc. 813 * Language cleanup / nits / poor grammar. 815 * removed "punted" colloquialism. 817 WG-05 to WG-06 819 o Consensus (according to me!) was that mail thread said "Child MAY 820 remove the CDS record". Changed to accommodate. 822 o "The proposal below can operate with both models, but the child 823 needs to be aware of the parental policies." - removed "but the 824 child needs to be aware of the parental policies.". This is no 825 longer true, as we suggest publishing both CDS and CDSNKEY. 827 o Added: "without some additional out of band process" to "The Child 828 may not enroll the initial key or introduce a new key when there 829 are no old keys that can be used (without some additional, out of 830 band, validation of the keys), because there is no way to validate 831 the information." 833 o Added a bit to the IANA section, requesting that TBA1 be replaced 834 with the IANA allocated code. 836 o Removed: "Some parents prefer to accept DNSSEC key information in 837 DS format, some parents prefer to accept it in DNSKEY format, and 838 calculate the DS record on the child's behalf. Each method has 839 pros and cons, both technical and policy. This solution is DS vs 840 DNSKEY agnostic, and allows operation with either." from Section 4 841 as it is covered in Section 2.2.1 843 o Remove a bunch of comments from the XML. I was getting tired of 844 scrolling past them. If the authors need them back, they are in 845 SVN commit 47. 847 WG-04 to WG-05 849 o More comments from Patrik, Paul and Ed. 851 o Many nits and fixes from Matthijs Mekking. 853 o Outstanding question: Should we remove the "Child SHOULD remove 854 the CDS record" text? Mail sent to list. 856 WG-03 to WG-04 858 o Large number of comments and changes from Patrik. 860 WG-02 to WG-03 861 o Fixed some references to RFC 5011 - from Samir Hussain. 863 o Fixed some spelling / typos - from Samir Hussain. 865 o A number of clarifications on the meaning on an empty / non- 866 existant CDS RRset - thanks to JINMEI, Tatuya 868 o Be consistent in mentioning both CDS and CDNSKEY throughout the 869 document. 871 WG-01 to WG-02 873 o Many nits and suggestions from Mukund. 875 o Matthijs: " I still think that it is too strong that the Child DNS 876 Operator SHOULD/MUST delete the CDS RRset when the Parent DS is 877 "in sync". This should be a MAY" 879 WG-00 to WG-01 881 o Addressed Vancouver: "Paul Hoffmann: NOT ready for WGLC. None of 882 the 2 documents explain why there is a split between the two 883 strategies." Thanks to Paul for providing text. 885 From -05 to WG-00: 887 o Nothing changed, resubmit under new name. 889 From 04 to 05 891 o Renamed the record back to CDS. 893 From 03 to 04. 895 o Added text explaining that CDS and CSYNC complement each other, 896 not replace or compete. 898 o Changed format of record to be to allow the 899 publication of DS **or** DNSKEY. 901 o Bunch of text changed to cover the above. 903 o Added a bit more text on the polling scaling stuff, expectation 904 that other triggers will be documented. 906 From 02 to 03 908 o Applied comments by Matthijs Mekking 909 o Incorporated suggestions from Edward Lewis about structure 911 o Reworked structure to be easier for implementors to follow 913 o Applied many suggestions from a wonderful thorough review by John 914 Dickinson 916 o Removed the going Unsigned option 918 From 01 to 02 920 o Major restructuring to facilitate easier discussion 922 o Lots of comments from DNSOP mailing list incorporated, including 923 making draft DNSKEY/DS neutral, explain different relationships 924 that exists, 926 o added more people to acks. 928 o added description of enterprise situations 930 o Unified on using Parental Agent over Parental Representative 932 o Removed redundant text when possible 934 o Added text to explain what can go wrong if not all child DNS 935 servers are in sync. 937 o Reference prior work by Matthijs Mekking 939 o Added text when parent calculates DS from DNSKEY 941 From - to -1. 943 o Removed from section .1: "If a child zone has gone unsigned, i.e. 944 no DNSKEY and no RRSIG in the zone, the parental representative 945 MAY treat that as intent to go unsigned. (NEEDS DISCUSSION)." 946 Added new text at end. -- suggestion by Scott Rose 20/Feb/13. 948 o Added some background on the different DNS Delegation operating 949 situations and how they affect interaction of parties. This moved 950 some blocks of text from later sections into here. 952 o Number of textual improvements from Stephan Lagerholm 954 o Added motivation why CDS is needed in CDS definition section 956 o Unified terminology in the document. 958 o Much more background 960 Authors' Addresses 962 Warren Kumari 963 Google 964 1600 Amphitheatre Parkway 965 Mountain View, CA 94043 966 US 968 Email: warren@kumari.net 970 Olafur Gudmundsson 971 Shinkuro Inc. 972 4922 Fairmont Av, Suite 250 973 Bethesda, MD 20814 974 USA 976 Email: ogud@ogud.com 978 George Barwood 979 33 Sandpiper Close 980 Gloucester GL2 4LZ 981 United Kingdom 983 Email: george.barwood@blueyonder.co.uk