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Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) No issues found here. Summary: 0 errors (**), 0 flaws (~~), 1 warning (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 dnsop O. Gudmundsson 3 Internet-Draft CloudFlare 4 Intended status: Standards Track P. Wouters 5 Expires: July 14, 2017 Red Hat 6 January 10, 2017 8 Managing DS records from parent via CDS/CDNSKEY 9 draft-ietf-dnsop-maintain-ds-05 11 Abstract 13 RFC7344 specifies how DNS trust can be maintained across key 14 rollovers in-band between parent and child. This document elevates 15 RFC7344 from informational to standards track and adds a standard 16 track method for initial trust setup and removal of secure entry 17 point. 19 Changing a domain's DNSSEC status can be a complicated matter 20 involving multiple unrelated parties. Some of these parties, such as 21 the DNS operator, might not even be known by all the organizations 22 involved. The inability to disable DNSSEC via in-band signaling is 23 seen as a problem or liability that prevents some DNSSEC adoption at 24 large scale. This document adds a method for in-band signaling of 25 these DNSSEC status changes. 27 This document describes reasonable policies to ease deployment of the 28 initial acceptance of new secure entry points (DS records) 30 It is preferable that operators collaborate on the transfer or move 31 of a domain. The best method is to perform a Key Signing Key ("KSK") 32 plus Zone Signing Key ("ZSK") rollover. If that is not possible, the 33 method using an unsigned intermediate state described in this 34 document can be used to move the domain between two parties. This 35 leaves the domain temporarily unsigned and vulnerable to DNS 36 spoofing, but that is preferred over the alternative of validation 37 failures due to a mismatched DS and DNSKEY record. 39 Status of This Memo 41 This Internet-Draft is submitted in full conformance with the 42 provisions of BCP 78 and BCP 79. 44 Internet-Drafts are working documents of the Internet Engineering 45 Task Force (IETF). Note that other groups may also distribute 46 working documents as Internet-Drafts. The list of current Internet- 47 Drafts is at http://datatracker.ietf.org/drafts/current/. 49 Internet-Drafts are draft documents valid for a maximum of six months 50 and may be updated, replaced, or obsoleted by other documents at any 51 time. It is inappropriate to use Internet-Drafts as reference 52 material or to cite them other than as "work in progress." 54 This Internet-Draft will expire on July 14, 2017. 56 Copyright Notice 58 Copyright (c) 2017 IETF Trust and the persons identified as the 59 document authors. All rights reserved. 61 This document is subject to BCP 78 and the IETF Trust's Legal 62 Provisions Relating to IETF Documents 63 (http://trustee.ietf.org/license-info) in effect on the date of 64 publication of this document. Please review these documents 65 carefully, as they describe your rights and restrictions with respect 66 to this document. Code Components extracted from this document must 67 include Simplified BSD License text as described in Section 4.e of 68 the Trust Legal Provisions and are provided without warranty as 69 described in the Simplified BSD License. 71 Table of Contents 73 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 74 1.1. Introducing a DS record . . . . . . . . . . . . . . . . . 3 75 1.2. Removing a DS Record . . . . . . . . . . . . . . . . . . 3 76 1.3. Notation . . . . . . . . . . . . . . . . . . . . . . . . 4 77 1.4. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4 78 2. The Three Uses of CDS . . . . . . . . . . . . . . . . . . . . 4 79 2.1. The meaning of the CDS RRset . . . . . . . . . . . . . . 5 80 3. Enabling DNSSEC via CDS/CDNSKEY . . . . . . . . . . . . . . . 5 81 3.1. Accept policy via authenticated channel . . . . . . . . . 6 82 3.2. Accept with extra checks . . . . . . . . . . . . . . . . 6 83 3.3. Accept after delay . . . . . . . . . . . . . . . . . . . 6 84 3.4. Accept with challenge . . . . . . . . . . . . . . . . . . 6 85 3.5. Accept from inception . . . . . . . . . . . . . . . . . . 7 86 4. DNSSEC Delete Algorithm . . . . . . . . . . . . . . . . . . . 7 87 5. Security considerations . . . . . . . . . . . . . . . . . . . 8 88 6. IANA considerations . . . . . . . . . . . . . . . . . . . . . 8 89 6.1. Promoting RFC7344 to standards track . . . . . . . . . . 9 90 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 9 91 7.1. Normative References . . . . . . . . . . . . . . . . . . 9 92 7.2. Informative References . . . . . . . . . . . . . . . . . 9 93 Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . 9 94 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9 96 1. Introduction 98 CDS/CDNSKEY [RFC7344] records are used to signal changes in secure 99 entry points. This is one method to maintain delegations that can be 100 used when the DNS operator has no other way to inform the parent that 101 changes are needed. This document elevates [RFC7344] from 102 informational to standards track RFC. 104 In addition, [RFC7344] is lacking two different options for full 105 automated operation to be possible. It did not define a method for 106 the Initial Trust establishment, leaving it open to each parent to 107 come up with an acceptance policy. Additionally, [RFC7344] did not 108 provide a "delete" signal for the child to inform the parent that the 109 DNSSEC security for its domain must be removed. 111 1.1. Introducing a DS record 113 Automated insertion of DS records has been limited for many zones by 114 the requirement that all changes pass through a "registry" of the 115 child zone's parent. This has significantly hindered deployment of 116 DNSSEC at large scale for DNS hosters, as the child zone owner is 117 often not aware or able to update DNS records such as the DS record. 119 This document describes a few possible methods for the parent to 120 accept a request by the child to add a DS record to its zone. These 121 methods have different security properties that addresses different 122 deployment scenarios, all resulting in an automated method of trust 123 introduction. 125 1.2. Removing a DS Record 127 This document introduces the delete option for both CDS and CDNSKEY, 128 allowing a child to signal to the parent to turn off DNSSEC. When a 129 domain is moved from one DNS operator to another, sometimes it is 130 necessary to turn off DNSSEC to facilitate the change of DNS 131 operator. Common scenarios include: 133 1 Alternative to doing a proper DNSSEC algorithm rollover due to 134 operational limitations such as software limitations. 136 2 Moving from a DNSSEC operator to a non-DNSSEC capable operator. 138 3 Moving to an operator that cannot/does-not-want to do a proper 139 DNSSEC rollover. 141 4 When moving between two DNS operators that use disjoint sets of 142 algorithms to sign the zone, thus an algorithm rollover can not be 143 performed. 145 5 The domain holder no longer wants DNSSEC enabled. 147 The lack of a "remove my DNSSEC" option is cited as a reason why some 148 operators cannot deploy DNSSEC, as this is seen as an operational 149 risk. 151 Turning off DNSSEC reduces the security of the domain and thus should 152 only be done carefully, and that decision should be fully under the 153 child domain's control. 155 1.3. Notation 157 Signaling can happen via CDS or CDNSKEY records. The only 158 differences between the two records is how information is 159 represented, and who calculates the DS digest. For clarity, this 160 document uses the term "CDS" throughout the document to mean "either 161 CDS or CDNSKEY". 163 When the document uses the word "parent" it implies an entity that is 164 authorized to insert DS records into the parent zone on behalf of the 165 child domain. Which entity this exactly is does not matter. It 166 could be the Registrar or Reseller that the child domain was 167 purchased from. It could be the Registry that the domain is 168 registered in when allowed. Or it could be some other entity. 170 1.4. Terminology 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. The Three Uses of CDS 178 In general there are three operations that a domain wants to instruct 179 their parent to perform: 181 1 Enable DNSSEC validation, i.e. place an initial DS RRset in the 182 parent. 184 2 Roll over the Key Signing Key ("KSK"), this means updating the DS 185 records in the parent to reflect the new set of KSK's at the 186 child. This could be an ADD operation, a DELETE operation on one 187 or more records while keeping at least one DS RR, or a full 188 REPLACE operation. 190 3 Turn off DNSSEC validation, i.e. delete all the DS records. 192 Rolling the KSK is covered in [RFC7344]. It is considered the safest 193 use case of a CDS/CDNSKEY record as it makes no change to the trust 194 relationship between parent and child. Introduction and removal of 195 DS records are defined in this document. As these CDS/CDNSKEY use 196 cases create or end the trust relationship between the parent and 197 child, these use cases should be carefully implemented and monitored. 199 2.1. The meaning of the CDS RRset 201 The semantic meaning of publishing a CDS RRset is interpreted to 202 mean: 204 "Publishing a CDS or CDNSKEY record signals to the parent that the 205 child desires that the corresponding DS records be synchronized. 206 Every parent or parental agent should have an acceptance policy of 207 these records for the three different use cases involved: Initial DS 208 publication, Key rollover, and Returning to Insecure." 210 In short, the CDS RRset is an instruction to the parent to modify the 211 DS RRset if the CDS and DS Reset's differ. 213 The acceptance policy for CDS in the rollover case is "seeing" 214 according to [RFC7344]. The acceptance policy in the Delete case is 215 seeing a (validly signed) CDS RRset with the delete operation 216 specified in this document. 218 3. Enabling DNSSEC via CDS/CDNSKEY 220 There are number of different models for managing initial trust, but 221 in the general case, the child wants to enable global validation. As 222 long as the child is insecure, DNS answers can be forged. The goal 223 is to promote the child from insecure to secure as soon as reasonably 224 possible by the parent. This means that the period from the child's 225 publication of CDS/CDNSKEY RRset to the parent publishing the 226 synchronized DS RRset should be as short as possible. 228 One important use case is how a third party DNS operator can upload 229 its DNSSEC information to the parent, so the parent can publish a DS 230 record for the child. In this case there is a possibility of setting 231 up some kind of authentication mechanism and submission mechanism 232 that is outside the scope of this document. 234 Below are some policies that parents can use. These policies assume 235 that the notifications can be verified or authenticated. 237 3.1. Accept policy via authenticated channel 239 In this case the parent is notified via authenticated channel UI/API 240 that a CDS/CDNSKEY RRset exists. In the case of a CDS RRset the 241 parent retrieves the CDS RRset and inserts the corresponding DS RRset 242 as requested. In the case of CDNSKEY the parent retrieves the 243 CDNSKEY RRset and calculates the DS record(s). Parents may limit the 244 DS record type based on local policy. Parents SHOULD NOT refuse CDS/ 245 CDNSKEY updates that do not (yet) have a matching DNSKEY in the child 246 zone. This will allow the child to prepublish a spare (and 247 potentially offline) DNSKEY. 249 3.2. Accept with extra checks 251 In this case the parent checks that the source of the notification is 252 allowed to request the DS insertion. The checks could include 253 whether this is a trusted entity, whether the nameservers correspond 254 to the requester, whether there have been any changes in registration 255 in the last few days, etc. The parent can also send a notification 256 requesting a confirmation, for example by sending email to the 257 registrant requesting a confirmation. The end result is that the CDS 258 RRset is accepted at the end of the checks or when the out-of-band 259 confirmation is received. Any extra checks should have proper rate 260 limiting in place to prevent abuse. 262 3.3. Accept after delay 264 In this case, if the parent deems the request valid, it starts 265 monitoring the CDS RRset at the child nameservers over period of time 266 to make sure nothing changes. After some time or after a number of 267 checks, preferably from different vantage points in the network, the 268 parent accepts the CDS RRset as a valid signal to update its DS RRset 269 for this child. 271 3.4. Accept with challenge 273 In this case the parent instructs the requester to insert some record 274 into the child domain to prove it has the ability to do so (i.e., it 275 is the operator of the zone). This method imposes a new task on the 276 parent to monitor the child zone to see if the challenge has been 277 added to the zone. The parent should verify the challenge is 278 published by all the child's nameservers and should test for this 279 challenge from various diverse network locations to increase the 280 security of this method as much as possible. 282 3.5. Accept from inception 284 If a parent is adding a new child domain that is not currently 285 delegated at all, it could use the child CDS/CDNSKEY RRset to 286 immediately publish a DS RRset along with the new NS RRset. This 287 would ensure that the new child domain is never active in an insecure 288 state. 290 4. DNSSEC Delete Algorithm 292 This document defines the previously reserved DNS Security Algorithm 293 Number of value 0 in the context of CDS and CDNSKEY records to mean 294 that the entire DS RRset at the parent must be removed. The value 0 295 remains reserved for the DS and DNSKEY records. 297 No DNSSEC validator can treat algorithm 0 as a valid signature 298 algorithm. If a validator sees a DNSKEY or DS record with this 299 algorithm value, it must treat it as unknown. Accordingly, the zone 300 is treated as unsigned unless there are other algorithms present. In 301 general the value 0 should never be used in the context of DNSKEY and 302 DS records. 304 The CERT record [RFC4398] defines the value 0 similarly to mean the 305 algorithm in the CERT record is not defined in DNSSEC. 307 The contents of the CDS or CDNSKEY RRset MUST contain one RR and only 308 contain the exactly the fields as shown below. 310 1 CDS 0 0 0 0 312 2 CDNSKEY 0 3 0 0 314 The keying material payload is represented by a single 0. This 315 record is signed in the same way as regular CDS/CDNSKEY RRsets are 316 signed. This is a change in format from strict interpretation of 317 [RFC7344] and may cause problems with some deployed software. 319 Strictly speaking the CDS record could be "CDS X 0 X" as only the 320 DNSKEY algorithm is what signals the DELETE operation, but for 321 clarity the "0 0 0" notation is mandated - this is not a definition 322 of DS Digest algorithm 0. The same argument applies to "CDNSKEY 0 3 323 0", the value 3 in second field is mandated by [RFC4034] section 324 2.1.2. 326 Once the parent has verified the CDS/CDNSKEY RRset and it has passed 327 other acceptance tests, the parent MUST remove the DS RRset. After 328 waiting a sufficient amount of time - depending on the parental TTL's 329 - the child can start the process of turning off DNSSEC. 331 5. Security considerations 333 Turning off DNSSEC reduces the security of the domain and thus should 334 only be done as a last resort in preventing DNSSEC validation errors 335 due to mismatched DS and DNSKEY records. 337 Users should keep in mind that re-establishing trust in delegation 338 can be hard and takes time. Before deciding to complete the rollover 339 via an unsigned state, all other options should be considered first. 341 A parent SHOULD ensure that when it is allowing a child to become 342 securely delegated, that it has a reasonable assurance that the CDS/ 343 CDNSKEY RRset that is used to bootstrap the security is visible from 344 a geographically and topologically diverse view. It SHOULD also 345 ensure that the zone validates correctly if the parent publishes the 346 DS record. A parent zone might also consider sending an email to its 347 contact addresses to give the child zone a warning that security will 348 be enabled after a certain amount of wait time - thus allowing a 349 child administrator to cancel the request. 351 This document describes a few possible acceptance criteria for the 352 Initial Trust establishment. Due to a large variety of legal 353 frameworks surrounding parent domains (TLDs in particular) this 354 document cannot give a definitive list of valid acceptance criteria. 355 Parental zones should look at the listed methods and pick the most 356 secure method possible within their legal and technical scenario, 357 possibly further securing the acceptance criteria, as long as the 358 deployed method still enables a fully automated method for non-direct 359 parties such as third party DNS hosters. 361 6. IANA considerations 363 This document updates entry number 0 of the "DNS Security Algorithm 364 Numbers" IANA Registry as follows: 366 +------+---------+-------+-------+-------+--------------------------+ 367 | Numb | Descrip | Mnemo | Zone | Trans | Reference | 368 | er | tion | nic | Signi | . | | 369 | | | | ng | Sec. | | 370 +------+---------+-------+-------+-------+--------------------------+ 371 | 0 | Delete | DELET | N | N | [RFC4034][RFC4398]RFC- | 372 | | DS | E | | | THIS-DOCUMENT] | 373 +------+---------+-------+-------+-------+--------------------------+ 375 6.1. Promoting RFC7344 to standards track 377 Experience has shown that CDS/CDNSKEY are useful in the deployment of 378 DNSSEC. [RFC7344] was published as Informational, this document 379 elevates RFC7344 to standards track. 381 7. References 383 7.1. Normative References 385 [RFC4034] Arends, R., Austein, R., Larson, M., Massey, D., and S. 386 Rose, "Resource Records for the DNS Security Extensions", 387 RFC 4034, DOI 10.17487/RFC4034, March 2005, 388 . 390 [RFC7344] Kumari, W., Gudmundsson, O., and G. Barwood, "Automating 391 DNSSEC Delegation Trust Maintenance", RFC 7344, 392 DOI 10.17487/RFC7344, September 2014, 393 . 395 7.2. Informative References 397 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 398 Requirement Levels", BCP 14, RFC 2119, 399 DOI 10.17487/RFC2119, March 1997, 400 . 402 [RFC4398] Josefsson, S., "Storing Certificates in the Domain Name 403 System (DNS)", RFC 4398, DOI 10.17487/RFC4398, March 2006, 404 . 406 Appendix A. Acknowledgments 408 This document is generated using the mmark tool that Miek Gieben has 409 developed. We thank number of people that have provided feedback and 410 useful comments including Bob Harold, John Levine, Matthijs 411 Mekking(!), Dan York, Shane Kerr, Jacques Latour. 413 Authors' Addresses 415 Olafur Gudmundsson 416 CloudFlare 418 Email: olafur+ietf@cloudflare.com 419 Paul Wouters 420 Red Hat 422 Email: pwouters@redhat.com