idnits 2.17.1 draft-ietf-dnsop-delegation-trust-maintainance-03.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- No issues found here. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year == Line 522 has weird spacing: '... full i.e. ...' == Line 525 has weird spacing: '...augment i.e. ...' -- The document date (February 8, 2014) is 3735 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for intended status: Informational ---------------------------------------------------------------------------- == Outdated reference: A later version (-06) exists of draft-ietf-dnsop-dnssec-key-timing-03 -- No information found for draft-parent-zones - is the name correct? Summary: 0 errors (**), 0 flaws (~~), 4 warnings (==), 2 comments (--). 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: August 12, 2014 Shinkuro Inc. 6 G. Barwood 8 February 8, 2014 10 Automating DNSSEC delegation trust maintenance 11 draft-ietf-dnsop-delegation-trust-maintainance-03 13 Abstract 15 This document describes a method to allow DNS operators to more 16 easily update DNSSEC Key Signing Keys using DNS as communication 17 channel. This document does not address the initial configuration of 18 trust anchors for a domain. The technique described is aimed at 19 delegations in which it is currently hard to move information from 20 the child to parent. 22 Status of This Memo 24 This Internet-Draft is submitted in full conformance with the 25 provisions of BCP 78 and BCP 79. 27 Internet-Drafts are working documents of the Internet Engineering 28 Task Force (IETF). Note that other groups may also distribute 29 working documents as Internet-Drafts. The list of current Internet- 30 Drafts is at http://datatracker.ietf.org/drafts/current/. 32 Internet-Drafts are draft documents valid for a maximum of six months 33 and may be updated, replaced, or obsoleted by other documents at any 34 time. It is inappropriate to use Internet-Drafts as reference 35 material or to cite them other than as "work in progress." 37 This Internet-Draft will expire on August 12, 2014. 39 Copyright Notice 41 Copyright (c) 2014 IETF Trust and the persons identified as the 42 document authors. All rights reserved. 44 This document is subject to BCP 78 and the IETF Trust's Legal 45 Provisions Relating to IETF Documents 46 (http://trustee.ietf.org/license-info) in effect on the date of 47 publication of this document. Please review these documents 48 carefully, as they describe your rights and restrictions with respect 49 to this document. Code Components extracted from this document must 50 include Simplified BSD License text as described in Section 4.e of 51 the Trust Legal Provisions and are provided without warranty as 52 described in the Simplified BSD License. 54 Table of Contents 56 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 57 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4 58 1.2. Requirements notation . . . . . . . . . . . . . . . . . . 4 59 2. Background . . . . . . . . . . . . . . . . . . . . . . . . . 4 60 2.1. DNS delegations . . . . . . . . . . . . . . . . . . . . . 4 61 2.2. Relationship between Parent and Child DNS operator . . . 5 62 2.2.1. Solution Space . . . . . . . . . . . . . . . . . . . 6 63 2.2.2. DNSSEC key change process . . . . . . . . . . . . . . 7 64 3. CDS / CDNSKEY (Child DS/ Child DNSKEY) record definitions . . 7 65 3.1. CDS Resource Record Format . . . . . . . . . . . . . . . 8 66 3.2. CDNSKEY Resource Record Format . . . . . . . . . . . . . 8 67 4. Automating DS maintainance with CDS/CDNSKEY records . . . . . 8 68 4.1. CDS / CDNSKEY processing rules . . . . . . . . . . . . . 9 69 5. Child's CDS / CDNSKEY Publication . . . . . . . . . . . . . . 9 70 6. Parent side CDS / CDNSKEY Consumption . . . . . . . . . . . . 9 71 6.1. Detecting a changed CDS / CDNSKEY . . . . . . . . . . . . 10 72 6.1.1. CDS / CDNSKEY Polling . . . . . . . . . . . . . . . . 10 73 6.1.2. Other mechanisms . . . . . . . . . . . . . . . . . . 10 74 6.2. Using the new CDS / CDNSKEY records . . . . . . . . . . . 11 75 6.2.1. Parent calculates DS . . . . . . . . . . . . . . . . 11 76 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12 77 8. Privacy Considerations . . . . . . . . . . . . . . . . . . . 12 78 9. Security Considerations . . . . . . . . . . . . . . . . . . . 12 79 10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 13 80 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 14 81 11.1. Normative References . . . . . . . . . . . . . . . . . . 14 82 11.2. Informative References . . . . . . . . . . . . . . . . . 14 83 Appendix A. RRR background . . . . . . . . . . . . . . . . . . . 15 84 Appendix B. Changes / Author Notes. . . . . . . . . . . . . . . 16 85 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 18 87 1. Introduction 89 When a DNS operator first signs their zone, they need to communicate 90 their DS record(s) (or DNSKEY(s)) to their parent through some out- 91 of-band method to complete the chain of trust. 93 Each time the child changes/rolls the key that is represented in the 94 parent, the new and/or deleted key information has to be communicated 95 to the parent and published there. How this information is sent to 96 the parent depends on the relationship the child has with the parent. 98 In many cases this is a manual process, and not an easy one. For 99 each key roll, there may be two interactions with the parent. Any 100 manual process is susceptible to mistakes and/or errors. In 101 addition, due to the annoyance factor of the process, operators may 102 avoid performing key rollovers or skip needed steps to publish the 103 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 publish 119 new DS records. To a large extent, the procedures this document 120 follows are as described in [RFC6781] section 4.1.2. 122 This technique is in some ways similar to [RFC5011] style rollovers, 123 but for sub-domains DS records, instead of trust anchors. 125 This technique is designed to be friendly both to fully automated 126 tools and humans. Fully automated tools can perform all the actions 127 needed without human intervention, and thus can monitor when it is 128 safe to move to the next step. 130 The solution described in this document only allows transferring 131 information about DNSSEC keys (DS and DNSKEY) from the child to the 132 parental agent. It lists exactly what the parent should publish, and 133 allows for publication of stand-by keys. A different protocol, 134 [I-D.csync], can be used to maintain other important delegation 135 information, such as NS and glue. These two protocols have been kept 136 as separate solutions because the problems are fundamentally 137 different, and a combined solution is overly complex. 139 This document describes a method for automating maintanance of the 140 delegation trust information, and proposes a polled / periodic 141 trigger for simplicity. Some users may prefer a different trigger, 142 such as a button on a webpage, a REST interface, DNS NOTIFY, etc. 143 These alternate / additional triggers are not discussed in this 144 document. 146 1.1. Terminology 148 The terminology we use is defined in this section 150 Highlighted roles 152 o Child: "The entity on record that has the delegation of the domain 153 from the parent" 155 o Parent: "The domain in which the child is registered" 157 o Child DNS operator: "The entity that maintains and publishes the 158 zone information for the child DNS" 160 o Parent DNS operator: "The entity that maintains and publishes the 161 zone information for the parent 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 RRR is our shorthand for Registry/Registrar/Registrant model of 171 parent child relationship see Appendix A for more. 173 1.2. Requirements notation 175 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 176 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 177 document are to be interpreted as described in [RFC2119]. 179 2. Background 181 2.1. DNS delegations 183 DNS operation consists of delegations of authority. For each 184 delegation there are (most of the time) two parties: the parent and 185 the child. 187 The parent publishes information about the delegations to the child; 188 for the name-servers it publishes an NS [RFC1035] RRset that lists a 189 hint for name-servers that are authoritative for the child. The 190 child also publishes a NS RRset, and this set is the authoritative 191 list of name-servers to the child zone. 193 The second RRset the parent sometimes publishes is the DS [RFC4034] 194 set. The DS RRset provides information about the DNSKEY(s) that the 195 child has told the parent it will use to sign its DNSKEY RRset. In 196 DNSSEC trust relationship between zones is provided by the following 197 chain: 199 parent DNSKEY --> DS --> child DNSKEY. 201 A prior proposal [I-D.auto-cpsync] suggested that the child send an 202 "update" to the parent via a mechanism similar to Dynamic Update. 203 The main issue became: How does the child find the actual parental 204 agent/server to send the update to? While that could have been 205 solved via technical means, the proposal died. There is also a 206 similar proposal in [I-D.parent-zones] 208 As the DS record can only be present at the parent (RFC4034 209 [RFC4034]), some other record/method is needed to automate which 210 DNSKEYs are picked to be represented in the parent zone's DS records. 211 One possibility is to use flags in the DNSKEY record. If the SEP bit 212 is set, this indicates that the DNSKEY is intended for use as a 213 secure entry point. This DNSKEY signs the DNSKEY RRset, and the 214 Parental Agent can calculate DS records based on that. But this 215 fails to meet some operating needs, including the child having no 216 influence what DS digest algorithms are used and DS records can only 217 be published for keys that are in the DNSKEY RRset. 219 2.2. Relationship between Parent and Child DNS operator 221 In practical application, there are many different relationships 222 between the parent and child DNS operators. The type of relationship 223 affects how the Child DNS Operator communicates with the parent. 224 This section will highlight some of the different situations, but is 225 by no means a complete list. 227 Different communication paths: 229 o Direct/API: The child can change the delegation information via 230 automated/scripted means EPP[RFC5730] used by many TLDs is an 231 example of this. Another example is the web service's 232 programmatic interfaces that Registrars make available to their 233 Resellers. 235 o User Interface: The Child uses a (web) site set up by the Parental 236 Agent for updating delegation information. 238 o Indirect: The communication has to be transmitted via out-of-band 239 between two parties, such as email, telephone etc.. This is common 240 when the Child's DNS operator is neither the child itself nor the 241 Registrar for the domain but a third party. 243 o Multi-step Combinations: The information flows through an 244 intermediary. It is possible, but unlikely, that all the steps 245 are automated via API's and there are no humans are involved. 247 A domain name holder (Child) may operate its own DNS servers or 248 outsource the operation. While we use the word parent as a singular, 249 parent can consist of single entity or a composite of many discrete 250 parts that have rules and roles. We refer to the entity that the 251 child corresponds with as the Parent. 253 In another common case an enterprise may delegate parts of its name- 254 space to be operated by a group that is not the same as that which 255 operates the enterprise's DNS servers. In this case the flow of 256 information is frequently handled in either an ad hoc manner or via 257 some corporate mechanism; this can range from email to fully- 258 automated operation. The word enterprise above covers all 259 organizations in which the domains are not sold on the open market 260 and there is some relationship between the entities. 262 2.2.1. Solution Space 264 This document is aimed at the cases in which there is an 265 organizational separation of the child and parent. 267 A further complication is when the Child DNS operator is not the 268 Child. There are two common cases of this, 270 a) The Parental Agent (e.g. registrar) handles the DNS operation 272 b) A third party takes care of the DNS operation. 274 If the Parental Agent is the DNS operator, life is much easier; the 275 Parental Agent can inject any delegation changes directly into the 276 Parent's Provisioning system. The techniques described below are not 277 needed in the case when Parental Agent is the DNS operator. 279 In the case of a third party DNS operator, the Child either needs to 280 relay changes in DNS delegation or give the Child DNS Operator access 281 to its delegation/registration account. 283 Some parents want the child to express their DNSKEYS in the form of 284 DS records, while others want to receive the DNSKEY records and 285 calculate the DS records themselves. There is no consensus on which 286 method is better; both have good reasons to exist. The proposal 287 below can operate with both models, but the child needs to be aware 288 of the parental policies. 290 2.2.2. DNSSEC key change process 292 After a Child DNS operator first signs the zone, there is a need to 293 interact with the Parent, for example via the delegation account 294 interface, to "upload / paste-in the zone's DS information". The 295 action of logging in through the delegation account user interface 296 authenticates that the user is authorized to change delegation 297 information for the child published in the parent zone. In the case 298 where the "Child DNS Operator" does not have access to the 299 registration account, the Child needs to perform the action. 301 At a later date, the Child DNS Operator may want to publish a new DS 302 record in the parent, either because they are rolling keys, or 303 because they want to publish a stand-by key. This involves 304 performing the same process as before. Furthermore when this is a 305 manual process with cut and paste, operational mistakes will happen 306 -- or worse, the update action is not performed at all. 308 3. CDS / CDNSKEY (Child DS/ Child DNSKEY) record definitions 310 This document specifies two new DNS RRtypes (CDS and CDNSKEY) that 311 indicates what the Child wants the parent's DS RRset to contain. It 312 allows the Child to present DS records and / or DNSKEY records (for 313 those parents who would rather generate the DS records for their 314 children). 316 The CDS / CDNSKEY records are published in the child zone and gives 317 the child control of what is published for it in the parental zone. 318 The CDS / CDNSKEY RRset expresses what the child would like the DS 319 RRset to look like after the change; it is a "replace" operation, and 320 it is up to the consumer of the records to translate that into the 321 appropriate add/delete operations in the registration systems (and in 322 the case of CDNSKEY, to generate the DS from the DNSKEY). If no CDS 323 / CDNSKEY RRset is present in child, this means that no change is 324 needed. 326 [[RFC Editor: Please remove this paragraph before publication] 327 Version -04 of the ID that became this working group document (http:/ 328 /tools.ietf.org/id/draft-kumari-ogud-dnsop-cds-04.txt) defined a new 329 record (CTA) that could hold either a DS or a DNSKEY record (with a 330 selector to differentiate between them). In a shocking development, 331 there was almost full consensus that this was horrid :-) ] 333 3.1. CDS Resource Record Format 335 The wire and presentation format of the CDS ("Child DS") record is 336 identical to the DS record [RFC4034]. IANA has allocated RR code 59 337 for the CDS record via expert review [I-D.ds-publish]. CDS uses the 338 same registries as DS for its fields 340 No special processing is performed by authoritative servers or by 341 revolvers, when serving or resolving. For all practical purposes CDS 342 is a regular RR type. 344 3.2. CDNSKEY Resource Record Format 346 The wire and presentation format of the CDNSKEY ("Child DNSKEY") 347 record is identical to the DNSKEY record. CDNSKEY uses the same 348 registries as DNSKEY for its fields. 350 No special processing is performed by authoritative servers or by 351 revolvers, when serving or resolving. For all practical purposes 352 CDNSKEY is a regular RR type. 354 4. Automating DS maintainance with CDS/CDNSKEY records 356 CDS/CDNSKEY records are intended to be "consumed" by delegation trust 357 maintainers. The use of CDS/CDNSKEY is optional. 359 Some parents prefer to accept DNSSEC key information in DS format, 360 some parents prefer to accept it in DNSKEY format, and calculate the 361 DS record on the child's behalf. Each method has pros and cons, both 362 technical and policy. This solution is DS vs DNSKEY agnostic, and 363 allows operation with either. 365 If the child knows what the parent prefers, they can publish the 366 parent's preferred record type. If the child does not know (or 367 simply chooses to), they can publish both CDS and CDNSKEY. If the 368 child publishes both, the two RRsets they SHOULD match in content. 369 The parent should use whichever one they choose, but SHOULD NOT query 370 for both and perform consistency checks between the CDS and CDNSKEY 371 records. 373 [Editor note: It is not an error for a child to have published CDS 374 records and not have CDNSKEYs that hash to those records, nor for 375 there to be CDNSKEY records without matching DS records. This is 376 because a child might have been publishing CDS records and then the 377 parent's policy changes to require CDNSKEY records. The child might 378 forget to remove the CDS, etc. This avoids all sorts of error 379 conditions / complexity, etc.] 381 4.1. CDS / CDNSKEY processing rules 383 If there are no CDS / CDNSKEY resource records in the child, this 384 signals that no change should be made to the current DS set. This 385 means that, once the child and parent are in sync, the child DNS 386 operator MAY remove all CDS records from the zone. 388 Following acceptance rules are placed on the CDS / CDNSKEY records as 389 follows: 391 o Location: "the CDS / CDNSKEY record MUST be at the child zone 392 apex". 394 o Signer: "MUST be signed with a key that is represented in both the 395 current DNSKEY and DS RRset's." 397 o Continuity: "SHOULD NOT break the current delegation if applied to 398 DS RRset" 400 If any these conditions fail the CDS / CDNSKEY record MUST be 401 ignored. 403 5. Child's CDS / CDNSKEY Publication 405 Child DNS Operator SHOULD only publish a CDS or CDNSKEY RRset when it 406 wants to make a change to the DS RRset in the Parent. The CDS / 407 CDNSKEY RRset SHOULD be compliant with the rules in Section 4.1. 408 When the Parent DS is "in-sync" with the CDS / CDNSKEY, the Child DNS 409 Operator MAY delete the CDS / CDNSKEY RRset(s). Note that if the 410 child has published a DNSKEY RR in the CDS, it will have to calculate 411 the DS (using the requested digest algorithm) to do the comparison. 413 A child MAY publish both CDS and CDNSKEY. If a child chooses to 414 publish both, it SHOULD attempt to maintain consistency (a matching 415 CDS for each CDNSKEY) 417 6. Parent side CDS / CDNSKEY Consumption 419 The CDS / CDNSKEY RRset MAY be used by the Parental Agent to update 420 the DS RRset in the parent zone. The Parental Agent for this uses a 421 tool that understands the CDS / CDNSKEY signing rules from 422 Section 4.1 so it may not be able to use a standard validator. 423 Parent SHOULD treat the Continuity rule as "MUST". 425 The parent MUST choose to accept either CDS or CDNSKEY records, and 426 MUST NOT expect there to be both. A parent SHOULD NOT perform a 427 consistency check between CDS and CDNSKEY (other than for 428 informational / debugging use). 430 6.1. Detecting a changed CDS / CDNSKEY 432 How the Parental Agent gets the CDS / CDNSKEY record may differ, 433 below are two examples as how this can take place. 435 Polling The Parental Agent operates a tool that periodically checks 436 each of the children that has a DS record to see if there is a 437 CDS or CDNSKEY record. 439 Pushing The delegation user interface has a button {Fetch DS} when 440 pushed preforms the CDS / CDNSKEY processing. If the Parent 441 zone does not contain DS for this delegation then the "push" 442 MUST be ignored. 444 In either case the Parental Agent MAY apply additional rules that 445 defer the acceptance of a CDS / CDNSKEY change, these rules may 446 include a condition that the CDS / CDNSKEY remains in place and valid 447 for some time period before it is accepted. It may be appropriate in 448 the "Pushing" case to assume that the Child is ready and thus accept 449 changes without delay. 451 6.1.1. CDS / CDNSKEY Polling 453 This is the only defined use of CDS / CDNSKEY in this document. 454 There are limits to the saleability of polling techniques, thus some 455 other mechanism is likely to be specified later that addresses CDS / 456 CDNSKEY usage in the situation where polling does not scale to. 457 Having said that Polling will work in many important cases like 458 enterprises, universities, small TLDs etc. In many regulatory 459 environments the registry is prohibited from talking to the 460 registrant. In most of these cases the registrant has a business 461 relationship with the registrar, and so the registrar can offer this 462 as a service. 464 If the CDS / CDNSKEY RRset does not exist, the Parental Agent MUST 465 take no action. Specifically it MUST NOT delete or alter the 466 existing DS RRset. 468 6.1.2. Other mechanisms 470 It is assumed that other mechanisms will be implemented to trigger 471 the parent to look for an updated CDS / CDNSKEY record. As the CDS / 472 CDNSKEY records are validated with DNSSEC, these mechanisms can be 473 unauthenticated (for example, a child could telephone its parent and 474 request that they process the new CDS or CDNSKEY record, an 475 unauthenticated POST could be made to a webserver (with rate- 476 limiting), etc.) 477 Other documents can specify the trigger conditions. 479 6.2. Using the new CDS / CDNSKEY records 481 Regardless of how the Parental Agent detected changes to a CDS / 482 CDNSKEY RR, the Parental Agent MUST use a DNSSEC validator to obtain 483 a validated CDS / CDNSKEY RRset from the Child zone. It would be a 484 good idea if the Parental Agent checked all NS RRs listed at the 485 delegation. 487 The Parental Agent MUST ensure that old versions of the CDS / CDNSKEY 488 RRset do not overwrite newer versions. This MAY be accomplished by 489 checking that the signature inception in the RRSIG for CDS / CDNSKEY 490 is newer and/or the serial number on the child's SOA is greater. 491 This may require the Parental Agent to maintain some state 492 information. 494 The Parental Agent MAY take extra security measures. For example, to 495 mitigate the possibility that a Child's key signing key has been 496 compromised, the Parental Agent may, for example, inform (by email or 497 other methods ) the Child DNS operator of the change. However the 498 precise out-of-band measures that a parent zone SHOULD take are 499 outside the scope of this document. 501 Once the Parental Agent has obtained a valid CDS / CDNSKEY it MAY 502 double check the publication rules from section 4.1. In particular 503 the Parental Agent MUST double check the Continuity rule and do its 504 best not to invalidate the Child zone. Once checked and if the CDS / 505 CDNSKEY and DS "differ" it may apply the changes to the parent zone. 506 If the parent consumes CDNSKEY, the parent should calculate the DS 507 before doing this comparison. 509 6.2.1. Parent calculates DS 511 There are cases where the Parent wants to calculate the DS record due 512 to policy reasons. In this case, the Child publishes CDNSKEY records 513 containing DNSKEYs. 515 The parent calculates the DS records on behalf of the children. The 516 DNS Parent needs to publish guidelines for the children as to what 517 digest algorithms are acceptable in the CDS record. 519 When a Parent operates in "calculate DS" mode it can operate in one 520 of two sub-modes 522 full i.e. it only publishes DS records it calculates from DNSKEY 523 records, 525 augment i.e. it will make sure there are DS records for the digest 526 algorithm(s) it requires(s). 528 Implications on Parental Agent are that the CDNSKEY and DS are not 529 exactly the same after update thus it needs to take that into 530 consideration when checking CDNSKEY records. Same goes for the Child 531 DNS Operator, it needs to be able to detect that the new DS RRset is 532 "equivalent" to the current CDNSKEY RRset, thus it can remove the 533 CDNSKEY RRset. 535 7. IANA Considerations 537 IANA has assigned RR Type code 59 for CDS. This was done for an 538 earlier version of this document[I-D.ds-publish] This document is to 539 become the reference for CDS RRtype. 541 IANA is requested to assign another RR Type for the CDNSKEY. 543 8. Privacy Considerations 545 All of the information handled / transmitted by this protocol is 546 public information published in the DNS. 548 9. Security Considerations 550 This work is for the normal case; when things go wrong there is only 551 so much that automation can fix. 553 If child breaks DNSSEC validation by removing all the DNSKEYs that 554 are represented in the DS set its only repair actions are to contact 555 the parent or restore the DNSKEYs in the DS set. 557 In the event of a compromise of the server or system generating 558 signatures for a zone, an attacker might be able to generate and 559 publish new CDS records. The modified CDS records will be picked up 560 by this technique and so may allow the attacker to extend the 561 effective time of his attack. If there a delay in accepting changes 562 to DS, as in [RFC5011], then the attacker needs to hope his activity 563 is not detected before the DS in parent is changed. If this type of 564 change takes place, the child needs to contact the parent (possibly 565 via a registrar web interface) and remove any compromised DS keys. 567 A compromise of the account with the parent (e.g. registrar) will not 568 be mitigated by this technique, as the "new registrant" can delete/ 569 modify the DS records at will. 571 While it may be tempting, this SHOULD NOT be used for initial 572 enrollment of keys since there is no way to ensure that the initial 573 key is the correct one. If is used, strict rules for inclusion of 574 keys like hold down times, challenge data inclusion etc., ought to be 575 used, along with some kind of challenge mechanism. A child cannot 576 use this mechanism to go from signed to unsigned (publishing an empty 577 CDS / CDNSKEY RRset means no-change should be made in the parent). 579 The CDS RR type should allow for enhanced security by simplifying 580 process. Since rollover is automated, updating a DS RRset by other 581 means may be regarded as unusual and subject to extra security 582 checks. 584 If there is a failure in applying changes in child zone to all DNS 585 servers listed in either parent or child NS set it is possible that 586 the Parental agent may get confused either not perform action because 587 it gets different answers on different checks or CDS validation 588 fails. In the worst case, Parental Agent performs an action 589 reversing a prior action but after the child signing system decides 590 to take the next step in rollover, resulting in a broken delegation. 592 DNS is a loosely coherent distributed database with local caching; 593 therefore, it is important to allow old information to expire from 594 caches before deleting DS or DNSKEY records. Similarly, it is 595 important to allow new records to propagate through the DNS before 596 use, see [RFC6781] and [I-D.key-time] 598 It is common practice for users to outsource their DNS hosting to a 599 3rd party DNS provider. In order for that provider to be able to 600 maintain the DNSSEC information some users give the provider their 601 registrar login credentials (which obviously has negative security 602 implications). Deploying the solution described in this document 603 allows the 3rd party DNS provider to maintain the DNSSEC information 604 without giving them the registrar credentials, thereby improving 605 security. 607 By automating the maintenance of the DNSSEC key information (and 608 removing humans from the process) we expect to decrease the number of 609 DNSSEC related outages, which should increase DNSSEC deployment. 611 10. Acknowledgements 613 We would like to thank a large number of folk, including: Mark 614 Andrews, Joe Abley, Jaap Akkerhuis, Roy Arends, Doug Barton, Brian 615 Dickinson, Paul Ebersman, Tony Finch, Patrik Faltsrom, Jim Galvin, 616 Paul Hoffman, Samir Hussain, Tatuya Jinmei, Olaf Kolkman, Cricket 617 Liu, Stephan Lagerholm, Matt Larson, Marco Sanz, Antoin Verschuren, 618 Suzanne Woolf, Paul Wouters, Matthijs Meeking, John Dickinson, 619 Timothe Litt and Edward Lewis. 621 Special thanks to Wes Hardaker for contributing significant text and 622 creating the complementary (CSYNC) solution, and to Paul Hoffman and 623 Mukund Sivaraman for text and review. 625 There were a number of other folk with whom we discussed this, 626 apologies for not remembering everyone. 628 11. References 630 11.1. Normative References 632 [RFC1035] Mockapetris, P., "Domain names - implementation and 633 specification", STD 13, RFC 1035, November 1987. 635 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 636 Requirement Levels", BCP 14, RFC 2119, March 1997. 638 [RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S. 639 Rose, "DNS Security Introduction and Requirements", RFC 640 4033, March 2005. 642 [RFC4034] Arends, R., Austein, R., Larson, M., Massey, D., and S. 643 Rose, "Resource Records for the DNS Security Extensions", 644 RFC 4034, March 2005. 646 [RFC4035] Arends, R., Austein, R., Larson, M., Massey, D., and S. 647 Rose, "Protocol Modifications for the DNS Security 648 Extensions", RFC 4035, March 2005. 650 [RFC5011] StJohns, M., "Automated Updates of DNS Security (DNSSEC) 651 Trust Anchors", STD 74, RFC 5011, September 2007. 653 [RFC6781] Kolkman, O., Mekking, W., and R. Gieben, "DNSSEC 654 Operational Practices, Version 2", RFC 6781, December 655 2012. 657 11.2. Informative References 659 [I-D.auto-cpsync] 660 Mekking, W., "Automated (DNSSEC) Child Parent 661 Synchronization using DNS UPDATE", draft-mekking-dnsop- 662 auto-cpsync-01 (work in progress), December 2010. 664 [I-D.csync] 665 Hardaker, W., "Child To Parent Synchronization in DNS", 666 draft-hardaker-dnsop-csync-02 (work in progress), July 667 2013. 669 [I-D.ds-publish] 670 Barwood, G., "DNS Transport", draft-barwood-dnsop-ds- 671 publish-02 (work in progress), June 2011. 673 [I-D.key-time] 674 Mekking, W., "DNSSEC Key Timing Considerations", draft- 675 ietf-dnsop-dnssec-key-timing-03 (work in progress), July 676 2012. 678 [I-D.parent-zones] 679 Andrews, M., "Updating Parent Zones", November 2013. 681 [RFC5730] Hollenbeck, S., "Extensible Provisioning Protocol (EPP)", 682 STD 69, RFC 5730, August 2009. 684 [RFC5910] Gould, J. and S. Hollenbeck, "Domain Name System (DNS) 685 Security Extensions Mapping for the Extensible 686 Provisioning Protocol (EPP)", RFC 5910, May 2010. 688 Appendix A. RRR background 690 In the RRR world, the different parties are frequently from different 691 organizations. In the single enterprise world there are also 692 organizational/geographical/cultural separations that affect how 693 information flows from a Child to the parent. 695 Due to the complexity of the different roles and interconnections, 696 automation of delegation information has been punted in the past. 697 There have been some proposals to automate this, in order to improve 698 the reliability of the DNS. These proposals have not gained enough 699 traction to become standards. 701 For example in many of the TLD cases there is the RRR model 702 (Registry, Registrar and Registrant). The Registry operates DNS for 703 the TLD, the Registrars accept registrations and place information 704 into the Registries database. The Registrant only communicates with 705 the Registrar; frequently the Registry is not allowed to communicate 706 with the Registrant. In that case as far as the registrant is 707 concerned the Registrar == Parent. 709 In many RRR cases the Registrar and Registry communicate via 710 EPP[RFC5730] and use the EPP DNSSEC extension [RFC5910]. In a number 711 of ccTLDs there are other mechanisms in use as well as EPP, but in 712 general there seems to be a movement towards EPP usage when DNSSEC is 713 enabled in the TLD. 715 Appendix B. Changes / Author Notes. 717 [RFC Editor: Please remove this section before publication ] 719 WG-02 to WG-03 721 o Fixed some references to RFC 5011 - from Samir Hussain. 723 o Fixed some spelling / typos - from Samir Hussain. 725 o A number of clarifiations on the meaning on an empty / non- 726 existant CDS RRset - thanks to JINMEI, Tatuya 728 o Be consistent in mentioning both CDS and CDNSKEY throughout the 729 document. 731 WG-01 to WG-02 733 o Many nits and suggestions from Mukund. 735 o Matthijs: " I still think that it is too strong that the Child DNS 736 Operator SHOULD/MUST delete the CDS RRset when the Parent DS is 737 "in-sync". This should be a MAY" 739 WG-00 to WG-01 741 o Addressed Vancouver: "Paul Hoffmann: NOT ready for WGLC. None of 742 the 2 documents explain why there is a split between the two 743 strategies." Thanks to Paul for providing text. 745 From -05 to WG-00: 747 o Nothing rchanged, resubmit under new name. 749 From 04 to 05 751 o Renamed the record back to CDS. 753 From 03 to 04. 755 o Added text explaining that CDS and CSYNC complement each other, 756 not replace or compete. 758 o Changed format of record to be to allow the 759 publication of DS **or** DNSKEY. 761 o Bunch of text changed to cover the above. 763 o Added a bit more text on the polling scaling stuff, expectation 764 that other triggers will be documented. 766 From 02 to 03 768 o Applied comments by Matthijs Mekking 770 o Incorporated suggestions from Edward Lewis about structure 772 o Reworked structure to be easier for implementors to follow 774 o Applied many suggestions from a wonderful thorough review by John 775 Dickinson 777 o Removed the going Unsigned option 779 From 01 to 02 781 o Major restructuring to facilitate easier discussion 783 o Lots of comments from DNSOP mailing list incorporated, including 784 making draft DNSKEY/DS neutral, explain different relationships 785 that exists, 787 o added more people to acks. 789 o added description of enterprise situations 791 o Unified on using Parental Agent over Parental Representative 793 o Removed redundant text when possible 795 o Added text to explain what can go wrong if not all child DNS 796 servers are in sync. 798 o Reference prior work by Matthijs Mekking 800 o Added text when parent calculates DS from DNSKEY 802 From - to -1. 804 o Removed from section .1: "If a child zone has gone unsigned, i.e. 805 no DNSKEY and no RRSIG in the zone, the parental representative 806 MAY treat that as intent to go unsigned. (NEEDS DISCUSSION)." 807 Added new text at end. -- suggestion by Scott Rose 20/Feb/13. 809 o Added some background on the different DNS Delegation operating 810 situations and how they affect interaction of parties. This moved 811 some blocks of text from later sections into here. 813 o Number of textual improvements from Stephan Lagerholm 815 o Added motivation why CDS is needed in CDS definition section 817 o Unified terminology in the document. 819 o Much more background 821 Authors' Addresses 823 Warren Kumari 824 Google 825 1600 Amphitheatre Parkway 826 Mountain View, CA 94043 827 US 829 Email: warren@kumari.net 831 Olafur Gudmundsson 832 Shinkuro Inc. 833 4922 Fairmont Av, Suite 250 834 Bethesda, MD 20814 835 USA 837 Email: ogud@ogud.com 839 George Barwood 840 33 Sandpiper Close 841 Gloucester GL2 4LZ 842 United Kingdom 844 Email: george.barwood@blueyonder.co.uk