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(The document does seem to have the reference to RFC 2119 which the ID-Checklist requires). -- The document date (November 14, 2016) is 2014 days in the past. Is this intentional? Checking references for intended status: Informational ---------------------------------------------------------------------------- == Outdated reference: draft-ietf-curdle-dnskey-eddsa has been published as RFC 8080 == Outdated reference: draft-ietf-dnsop-maintain-ds has been published as RFC 8078 -- Obsolete informational reference (is this intentional?): RFC 6944 (Obsoleted by RFC 8624) 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 D. York 3 Internet-Draft Internet Society 4 Intended status: Informational O. Sury 5 Expires: May 18, 2017 CZ.NIC 6 P. Wouters 7 Red Hat 8 O. Gudmundsson 9 CloudFlare 10 November 14, 2016 12 Observations on Deploying New DNSSEC Cryptographic Algorithms 13 draft-york-dnsop-deploying-dnssec-crypto-algs-04 15 Abstract 17 As new cryptographic algorithms are developed for use in DNSSEC 18 signing and validation, this document captures the steps needed for 19 new algorithms to be deployed and enter general usage. The intent is 20 to ensure a common understanding of the typical deployment process 21 and potentially identify opportunities for improvement of operations. 23 Status of This Memo 25 This Internet-Draft is submitted in full conformance with the 26 provisions of BCP 78 and BCP 79. 28 Internet-Drafts are working documents of the Internet Engineering 29 Task Force (IETF). Note that other groups may also distribute 30 working documents as Internet-Drafts. The list of current Internet- 31 Drafts is at http://datatracker.ietf.org/drafts/current/. 33 Internet-Drafts are draft documents valid for a maximum of six months 34 and may be updated, replaced, or obsoleted by other documents at any 35 time. It is inappropriate to use Internet-Drafts as reference 36 material or to cite them other than as "work in progress." 38 This Internet-Draft will expire on May 18, 2017. 40 Copyright Notice 42 Copyright (c) 2016 IETF Trust and the persons identified as the 43 document authors. All rights reserved. 45 This document is subject to BCP 78 and the IETF Trust's Legal 46 Provisions Relating to IETF Documents 47 (http://trustee.ietf.org/license-info) in effect on the date of 48 publication of this document. Please review these documents 49 carefully, as they describe your rights and restrictions with respect 50 to this document. Code Components extracted from this document must 51 include Simplified BSD License text as described in Section 4.e of 52 the Trust Legal Provisions and are provided without warranty as 53 described in the Simplified BSD License. 55 Table of Contents 57 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 58 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 59 2. Aspects of Deploying New Algorithms . . . . . . . . . . . . . 3 60 2.1. DNS Resolvers Performing Validation . . . . . . . . . . . 4 61 2.1.1. Resolvers and Unknown Algorithms . . . . . . . . . . 4 62 2.2. Authoritative DNS Servers . . . . . . . . . . . . . . . . 5 63 2.3. Signing Software . . . . . . . . . . . . . . . . . . . . 5 64 2.4. Registries . . . . . . . . . . . . . . . . . . . . . . . 6 65 2.5. Registrars . . . . . . . . . . . . . . . . . . . . . . . 6 66 2.6. DNS Hosting Operators . . . . . . . . . . . . . . . . . . 7 67 2.7. Applications . . . . . . . . . . . . . . . . . . . . . . 7 68 3. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . 7 69 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8 70 5. Security Considerations . . . . . . . . . . . . . . . . . . . 8 71 6. References . . . . . . . . . . . . . . . . . . . . . . . . . 8 72 6.1. Normative References . . . . . . . . . . . . . . . . . . 8 73 6.2. Informative References . . . . . . . . . . . . . . . . . 9 74 Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 9 75 Appendix B. Changes . . . . . . . . . . . . . . . . . . . . . . 10 76 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10 78 1. Introduction 80 The DNS Security Extensions (DNSSEC), broadly defined in [RFC4033], 81 [RFC4034] and [RFC4035], make use of cryptographic algorithms in both 82 the signing of DNS records and the validation of DNSSEC signatures by 83 recursive resolvers. 85 The current list of cryptographic algorithms can be found in the IANA 86 "Domain Name System Security (DNSSEC) Algorithm Numbers" registry 87 located at 88 Algorithms are added to this IANA registry through a process defined 89 in [RFC6014]. Note that [RFC6944] provides some guidance as to which 90 of these algorithms should be implemented and supported. 92 Historically DNSSEC signatures have primarily used cryptographic 93 algorithms based on RSA keys. As deployment of DNSSEC has increased 94 there has been interest in using newer and more secure algorithms, 95 particularly those using elliptic curve cryptography. 97 The ECDSA algorithm [RFC6605] has seen some adoption and a new 98 signing algorithm has been proposed: Edwards-curve Digital Signature 99 Algorithm (EdDSA) using a choice of two curves, Ed25519 and Ed448, 100 [I-D.ietf-curdle-dnskey-eddsa]. 102 The challenge is that the deployment of a new cryptographic algorithm 103 for DNSSEC is not a simple process. DNSSEC algorithms are used 104 throughout the DNS infrastructure for tasks such as: 106 o Generation of keys ("DNSKEY" record) for signing 108 o Creation of DNSSEC signatures in zone files ("RRSIG") 110 o Usage in a Delegation Signer ("DS") record {{?RFC3658}} for the 111 "chain of trust" connecting back to the root of DNS 113 o Generation of NSEC/NSEC3 responses by authoritative DNS servers 115 o Validation of DNSSEC signatures by DNS resolvers 117 In order for a new cryptographic algorithm to be fully deployed, all 118 aspects of the DNS infrastructure that interact with DNSSEC must be 119 updated to use the new algorithm. 121 This document outlines the current understanding of the components of 122 the DNS infrastructure that need to be updated to deploy a new 123 cryptographic algorithm. 125 It should be noted that DNSSEC is not alone in complexity of 126 deployment. The IAB documented "Guidelines for Cryptographic 127 Algorithm Agility" in [?!RFC7696] to highlight the importance of this 128 issue. 130 1.1. Terminology 132 In this document, the key words "MUST", "MUST NOT", "REQUIRED", 133 "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", 134 and "OPTIONAL" are to be interpreted as described in BCP 14, RFC 2119 135 [RFC2119]. 137 2. Aspects of Deploying New Algorithms 139 For a new cryptographic algorithm to be deployed in DNSSEC, the 140 following aspects of the DNS infrastructure must be updated: 142 o DNS resolvers performing validation 144 o Authoritative DNS servers 145 o Signing software 147 o Registries 149 o Registrars 151 o DNS Hosting Operators 153 o Applications 155 Each of these aspects is discussed in more detail below. 157 2.1. DNS Resolvers Performing Validation 159 DNS recursive resolvers perform "validation" to check the DNSSEC 160 signatures of records received in a DNS query. To validate the 161 signatures, the resolvers need to be able to understand the algorithm 162 used to create the signatures. 164 In the case of a new algorithm, the resolver software needs to be 165 updated. In some cases this could require waiting until an 166 underlying library is updated to support the new algorithm. 168 Once the software is updated, the updates need to be deployed to all 169 resolvers using that software. This can be challenging in cases of 170 customer-premises equipment (CPE) that does not have any mechanism 171 for automatic updating. 173 2.1.1. Resolvers and Unknown Algorithms 175 It should be noted that section 5.2 of [RFC4035] states: 177 "If the resolver does not support any of the algorithms listed in an 178 authenticated DS RRset, then the resolver will not be able to verify 179 the authentication path to the child zone. In this case, the 180 resolver SHOULD treat the child zone as if it were unsigned." 182 This means that signing a zone with a new algorithm that is not 183 widely supported by DNS resolvers would result in the signatures 184 being ignored and the zone treated as unsigned until resolvers were 185 updated to recognize the new algorithm. 187 Note that in at least one 2016 case the resolver software deployed on 188 customer premises by an Internet service provider (ISP) turned out 189 not to be compliant with RFC 4035. Instead of ignoring the 190 signatures using unknown algorithms and treating the zones as 191 unsigned, the validating resolver rejected the signatures and 192 returned a SERVFAIL to the DNS query. This resulted in the ISP 193 turning off DNSSEC validation on the equipment. Further 194 investigation showed that a newer version of the resolver software 195 did correctly support ECDSA, but now all customer premises equipment 196 must be updated to this new version. 198 The point is that it is not safe to assume all resolver software will 199 correctly implement this part of RFC 4035. 201 2.2. Authoritative DNS Servers 203 Authoritative DNS servers serve out signed DNS records. Serving new 204 DNSSEC signing algorithms should not be a problem as a well-written 205 authoritative DNS server implementation should be agnostic to the RR 206 DATA they serve. 208 The one exception is if the new cryptographic algorithms are used in 209 the creation of NSEC/NSEC3 responses. In the case of new NSEC/NSEC3 210 algorithms, the authoritative DNS server software would need to be 211 updated to be able to use the new algorithms. 213 Note that some authoritative server implementations could include 214 DNSSEC signing as part of the server and thus also fall into the 215 "Signing Software" category below. 217 2.3. Signing Software 219 The software performing the signing of the records needs to be 220 updated with the new cryptographic algorithm. 222 User interfaces that allow users to interact with the DNSSEC signing 223 software may also need to be updated to reflect the existence of the 224 new algorithm. 226 Note that the key and signatures with the new algorithm will need to 227 co-exist with the existing key and signatures for some period of 228 time. This will have an impact on the size of the DNS records. 230 [NOTE(OS): Shouldn't we just update the language that requires the 231 resolver to be so strict and finally be done with this requirement? 232 Or just give a recommendation in the paragraph on resolver here?] 234 One issue that has been identified is that not all commonly-used 235 signing software releases include support for an algorithm rollover. 236 This software would need to be updated to support rolling an 237 algorithm before any new algorithms could be deployed. 239 2.4. Registries 241 The registry for a top-level domain (TLD) needs to accept DS records 242 using the new cryptographic algorithm. 244 Observations to date have shown that some registries only accept DS 245 records with certain algorithms. Registry representatives have 246 indicated that they verify the accuracy of DS records to reduce 247 technical support incidents and ensure customers do not mistakenly 248 create any outages. 250 However, this means that registries who perform this level of 251 checking must be able to understand new algorithms in order to 252 successfully verify the DS records. 254 Separately, feedback from registrars has indicated that they do not 255 currently have any mechanism to understand what DNSSEC algorithms a 256 registry can accept. 258 2.5. Registrars 260 Registrars perform a critical role in the DNSSEC "chain of trust" of 261 passing the DS record up to the Registry to ensure that the signed 262 zone can be authenticated from the root of DNS all the way to the 263 zone. 265 If the registrar is also providing the DNS hosting services for a 266 domain, the registrar can easily create the "DS" record from the 267 "DNSKEY" record and pass the DS record up to the registry. 269 However, if the authoritative servers for a domain are not with the 270 registrar, then the registrar needs to provide some mechanism to 271 accept a DS record to pass that up to the registry. Typically this 272 is done through a web interface. 274 An issue is that many registrar web interfaces only allow the input 275 of DS records using a listed set of DNSSEC algorithms. Any new 276 cryptographic algorithms need to be added to the web interface in 277 order to be accepted into the registrar's system. 279 Additionally, in a manner similar to registries, many registrars 280 perform some level of verification on the DS record to ensure it was 281 entered "correctly". To do this verification, the registrar's 282 software needs to understand the algorithm used in the DS record. 283 This requires the software to be updated to support the new 284 algorithm. 286 Note that work is currently underway in [I-D.ietf-dnsop-maintain-ds] 287 to provide an automated mechanism to update the DS records with a 288 registry. If this method becomes widely adopted, registrar web 289 interfaces may no longer be needed. 291 2.6. DNS Hosting Operators 293 DNS hosting operators are entities that are operating the 294 authoritative DNS servers for domains and with DNSSEC are also 295 providing the signing of zones. In many cases they may also be the 296 registrar for domain names, but in other cases they are a separate 297 entity providing DNS services to customers. 299 DNS hosting operators need to update their authoritative DNS server 300 software to understand new cryptographic algorithms, but they also 301 need to update their web interfaces and provisioning software to 302 allow configuration and support of new algorithms. 304 2.7. Applications 306 Beyond the recursive resolvers, authoritative servers, web interfaces 307 and provisioning software, it has been observed that some 308 applications (or "apps"), particularly in the mobile environment, are 309 including their own DNS resolvers within the app itself. These 310 recursive resolvers are used by the app instead of the recursive 311 resolver included with the underlying operating system. These 312 applications that perform DNSSEC validation would need to also be 313 updated to understand a new algorithm. 315 In many cases, it may be that an underlying developer library needs 316 to be updated first. It will then depend upon how long it takes the 317 application developer to pull in the updated library. 319 Outside of applications, these developer libraries are also typically 320 used by recursive resolver software and signing software. 322 3. Conclusion 324 This document provides a view into the steps necessary for the 325 deployment of new cryptographic algorithms in DNSSEC at the time of 326 this publication. In order to more rapidly roll out new DNSSEC 327 algorithms, these steps must be understood and hopefully improved 328 over time. 330 It should be noted that a common theme to emerge from all discussions 331 is a general reluctance to update or change any DNS-related software. 332 "If it isn't broken, don't fix it" is a common refrain. While 333 perhaps understandable from a stability point of view, this attitude 334 creates a challenge for deploying new algorithms. 336 One potential idea suggested during discussions was for some kind of 337 web-based testing tool that could assist people in understanding what 338 algorithms are supported by different servers and sites. 340 It is also quite clear that any deployment of new algorithms for 341 DNSSEC use will take a few years to propagate throughout the 342 infrastructure. This needs to be factored in as new algorithms are 343 proposed. 345 4. IANA Considerations 347 This document does not make any requests of IANA. 349 5. Security Considerations 351 No new security considerations are created by this document. 353 It should be noted that there are security considerations regarding 354 changing DNSSEC algorithms that are mentioned in both [RFC6781] and 355 [RFC7583]. 357 6. References 359 6.1. Normative References 361 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 362 Requirement Levels", BCP 14, RFC 2119, 363 DOI 10.17487/RFC2119, March 1997, 364 . 366 [RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S. 367 Rose, "DNS Security Introduction and Requirements", 368 RFC 4033, DOI 10.17487/RFC4033, March 2005, 369 . 371 [RFC4034] Arends, R., Austein, R., Larson, M., Massey, D., and S. 372 Rose, "Resource Records for the DNS Security Extensions", 373 RFC 4034, DOI 10.17487/RFC4034, March 2005, 374 . 376 [RFC4035] Arends, R., Austein, R., Larson, M., Massey, D., and S. 377 Rose, "Protocol Modifications for the DNS Security 378 Extensions", RFC 4035, DOI 10.17487/RFC4035, March 2005, 379 . 381 6.2. Informative References 383 [I-D.ietf-curdle-dnskey-eddsa] 384 Sury, O. and R. Edmonds, "EdDSA for DNSSEC", draft-ietf- 385 curdle-dnskey-eddsa-01 (work in progress), October 2016. 387 [I-D.ietf-dnsop-maintain-ds] 388 Gudmundsson, O. and P. Wouters, "Managing DS records from 389 parent via CDS/CDNSKEY", draft-ietf-dnsop-maintain-ds-04 390 (work in progress), October 2016. 392 [RFC6014] Hoffman, P., "Cryptographic Algorithm Identifier 393 Allocation for DNSSEC", RFC 6014, DOI 10.17487/RFC6014, 394 November 2010, . 396 [RFC6605] Hoffman, P. and W. Wijngaards, "Elliptic Curve Digital 397 Signature Algorithm (DSA) for DNSSEC", RFC 6605, 398 DOI 10.17487/RFC6605, April 2012, 399 . 401 [RFC6781] Kolkman, O., Mekking, W., and R. Gieben, "DNSSEC 402 Operational Practices, Version 2", RFC 6781, 403 DOI 10.17487/RFC6781, December 2012, 404 . 406 [RFC6944] Rose, S., "Applicability Statement: DNS Security (DNSSEC) 407 DNSKEY Algorithm Implementation Status", RFC 6944, 408 DOI 10.17487/RFC6944, April 2013, 409 . 411 [RFC7583] Morris, S., Ihren, J., Dickinson, J., and W. Mekking, 412 "DNSSEC Key Rollover Timing Considerations", RFC 7583, 413 DOI 10.17487/RFC7583, October 2015, 414 . 416 Appendix A. Acknowledgements 418 The information in this document evolved out of several mailing list 419 discussions and also through engagement with participants in the 420 following sessions or events: 422 o DNSSEC Workshop at ICANN 53 (Buenos Aires) 424 o DNSSEC Workshop at ICANN 55 (Marrakech) 426 o Spring 2016 DNS-OARC meeeting (Buenos Aires) 428 o various IETF 95 working groups (Buenos Aires) 429 o Panel session at RIPE 72 (Copenhagen) 431 o DNSSEC Workshop at ICANN 56 (Helsinki) 433 The authors thank the participants of the various sessions for their 434 feedback. 436 Appendix B. Changes 438 NOTE TO RFC EDITOR - Please remove this "Changes" section prior to 439 publication. Thank you. 441 o Revision -04 corrected the references which did not appear in -03 442 due to an error in the markdown source. 444 o Revision -03 removed the reference to the location of the ISP in 445 the text added in version -02. 447 o Revision -02 added text to the resolver section about an example 448 where resolver software did not correctly follow RFC 4035 and 449 treat packets with unknown algorithms as unsigned. The markdown 450 source of this I-D was also migrated to the markdown syntax 451 favored by the 'mmark' tool. 453 o Revision -01 adds text about authoritative servers needing an 454 update if the algorithm is for NSEC/NSEC3. Also expands 455 acknowledgements. 457 Authors' Addresses 459 Dan York 460 Internet Society 462 Email: york@isoc.org 464 Ondrej Sury 465 CZ.NIC 467 Email: ondrej.sury@nic.cz 469 Paul Wouters 470 Red Hat 472 Email: pwouters@redhat.com 473 Olafur Gudmundsson 474 CloudFlare 476 Email: olafur+ietf@cloudflare.com