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Ebersman 3 Internet-Draft Comcast 4 Intended status: Informational C. Griffiths 5 Expires: November 11, 2015 6 W. Kumari 7 Google 8 J. Livingood 9 Comcast 10 R. Weber 11 Nominum 12 May 10, 2015 14 Definition and Use of DNSSEC Negative Trust Anchors 15 draft-ietf-dnsop-negative-trust-anchors-08 17 Abstract 19 DNS Security Extensions (DNSSEC) is now entering widespread 20 deployment. However, domain signing tools and processes are not yet 21 as mature and reliable as those for non-DNSSEC-related domain 22 administration tools and processes. Negative Trust Anchors 23 (described in this document) can be used to mitigate DNSSEC 24 validation failures. 26 [RFC Editor: Please remove this before publication. This document is 27 being stored in github at https://github.com/wkumari/draft-livingood- 28 dnsop-negative-trust-anchors . Authors accept pull requests, and keep 29 the latest (edit buffer) versions there, so commenters can follow 30 along at home.] 32 Status of This Memo 34 This Internet-Draft is submitted in full conformance with the 35 provisions of BCP 78 and BCP 79. 37 Internet-Drafts are working documents of the Internet Engineering 38 Task Force (IETF). Note that other groups may also distribute 39 working documents as Internet-Drafts. The list of current Internet- 40 Drafts is at http://datatracker.ietf.org/drafts/current/. 42 Internet-Drafts are draft documents valid for a maximum of six months 43 and may be updated, replaced, or obsoleted by other documents at any 44 time. It is inappropriate to use Internet-Drafts as reference 45 material or to cite them other than as "work in progress." 47 This Internet-Draft will expire on November 11, 2015. 49 Copyright Notice 51 Copyright (c) 2015 IETF Trust and the persons identified as the 52 document authors. All rights reserved. 54 This document is subject to BCP 78 and the IETF Trust's Legal 55 Provisions Relating to IETF Documents 56 (http://trustee.ietf.org/license-info) in effect on the date of 57 publication of this document. Please review these documents 58 carefully, as they describe your rights and restrictions with respect 59 to this document. Code Components extracted from this document must 60 include Simplified BSD License text as described in Section 4.e of 61 the Trust Legal Provisions and are provided without warranty as 62 described in the Simplified BSD License. 64 Table of Contents 66 1. Introduction and motivation . . . . . . . . . . . . . . . . . 3 67 1.1. Definition of a Negative Trust Anchor . . . . . . . . . . 3 68 1.2. Domain Validation Failures . . . . . . . . . . . . . . . 4 69 1.3. End User Reaction . . . . . . . . . . . . . . . . . . . . 4 70 1.4. Switching to a Non-Validating Resolver is Not Recommended 5 71 2. Use of a Negative Trust Anchor . . . . . . . . . . . . . . . 5 72 3. Managing Negative Trust Anchors . . . . . . . . . . . . . . . 7 73 3.1. Alerting Users to NTA Use . . . . . . . . . . . . . . . . 7 74 4. Removal of a Negative Trust Anchor . . . . . . . . . . . . . 7 75 5. Comparison to Other DNS Misconfigurations . . . . . . . . . . 8 76 6. Intentionally Broken Domains . . . . . . . . . . . . . . . . 8 77 7. Discovering broken domains . . . . . . . . . . . . . . . . . 9 78 8. Other Considerations . . . . . . . . . . . . . . . . . . . . 11 79 8.1. Security Considerations . . . . . . . . . . . . . . . . . 11 80 8.2. Privacy Considerations . . . . . . . . . . . . . . . . . 11 81 8.3. IANA Considerations . . . . . . . . . . . . . . . . . . . 11 82 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 11 83 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 12 84 10.1. Normative References . . . . . . . . . . . . . . . . . . 12 85 10.2. Informative References . . . . . . . . . . . . . . . . . 12 86 Appendix A. Configuration Examples . . . . . . . . . . . . . . . 13 87 A.1. NLNet Labs Unbound . . . . . . . . . . . . . . . . . . . 13 88 A.2. ISC BIND . . . . . . . . . . . . . . . . . . . . . . . . 13 89 A.3. Nominum Vantio . . . . . . . . . . . . . . . . . . . . . 14 90 Appendix B. Document Change Log . . . . . . . . . . . . . . . . 14 91 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 17 93 1. Introduction and motivation 95 This document defines a Negative Trust Anchor, which can be used 96 during the transition to ubiquitous DNSSEC deployment. Negative 97 Trust Anchors (NTAs) are configured locally on a validating DNS 98 recursive resolver to shield end users from DNSSEC-related 99 authoritative name server operational errors. Negative Trust Anchors 100 are intended to be temporary, and should not be distributed by IANA 101 or any other organization outside of the administrative boundary of 102 the organization locally implementing a Negative Trust Anchor. 103 Finally, Negative Trust Anchors pertain only to DNSSEC and not to 104 Public Key Infrastructures (PKI) such as X.509. 106 DNSSEC has now entered widespread deployment. However, the DNSSEC 107 signing tools and processes are less mature and reliable than those 108 for non-DNSSEC-related administration. As a result, operators of DNS 109 recursive resolvers, such as Internet Service Providers (ISPs), 110 occasionally observe domains incorrectly managing DNSSEC-related 111 resource records. This mismanagement triggers DNSSEC validation 112 failures, and then causes large numbers of end users to be unable to 113 reach a domain. Many end users tend to interpret this as a failure 114 of their ISP or resolver operator, and may switch to a non-validating 115 resolver or contact their ISP to complain, rather than seeing this as 116 a failure on the part of the domain they wanted to reach. Without 117 the techniques in this document, this pressure may cause the resolver 118 operator to disable (or simply not deploy) DNSSEC validation. Use of 119 a Negative Trust Anchor to temporarily disable DNSSEC validation for 120 a specific misconfigured domain name immediately restores access for 121 end users. This allows the domain's administrators to fix their 122 misconfiguration, while also allowing the organization using the 123 Negative Trust Anchor to keep DNSSEC validation enabled and still 124 reach the misconfigured domain. 126 It is worth noting the following text from [RFC4033] - "In the final 127 analysis, however, authenticating both DNS keys and data is a matter 128 of local policy, which may extend or even override the protocol 129 extensions defined in this document set." A responsibility (one of 130 many) of a caching server operator is to "protect the integrity of 131 the cache." 133 1.1. Definition of a Negative Trust Anchor 135 Trust Anchors are defined in [RFC5914]. A trust anchor should be 136 used by a validating caching resolver as a starting point for 137 building the authentication chain for a signed DNS response. By way 138 of analogy, negative trust anchors stop validation of the 139 authentication chain. Instead, the validator treats any upstream 140 responses as if the zone is unsigned and does not set the AD bit in 141 responses it sends to clients. Note that this is a behavior, and not 142 a separate resource record. This Negative Trust Anchor can 143 potentially be implemented at any level within the chain of trust and 144 would stop validation from that point in the chain down. Validation 145 starts again if there is a positive trust anchor further down in the 146 chain. For example, if there is a NTA at example.com, and a positive 147 trust anchor at foo.bar.example.com, then validation resumes for 148 foo.bar.example.com and anything below it. 150 1.2. Domain Validation Failures 152 A domain name can fail validation for two general reasons: a 153 legitimate security failure such as due to an attack or compromise of 154 some sort, or as a result of misconfiguration on the part of an 155 domain administrator. As domains transition to DNSSEC, the most 156 common reason for a validation failure has been misconfiguration. 157 Thus, domain administrators should be sure to read [RFC6781] in full. 158 They should also pay special attention to Section 4.2, pertaining to 159 key rollovers, which appear to be the cause of many recent validation 160 failures. 162 It is also possible that some DNSSEC validation failures could arise 163 due to differences in how different software developers interpret 164 DNSSEC standards and/or how those developers choose to implement 165 support for DNSSEC. For example, it is conceivable that a domain may 166 be DNSSEC signed properly, and one vendor's DNS recursive resolvers 167 will validate the domain but other vendors' software may fail to 168 validate the domain. 170 1.3. End User Reaction 172 End users generally do not know of, understand, or care about the 173 resolution process that causes connections to happen. This is by 174 design: the point of the DNS is to insulate users from having to 175 remember IP addresses through a friendlier way of naming systems. It 176 follows from this that end users do not, and should not, be expected 177 to know about DNSSEC, validation, or anything of the sort. As a 178 result, end users may misinterpret the failure to reach a domain due 179 to DNSSEC-related misconfiguration . They may (incorrectly) assume 180 that their ISP is purposely blocking access to the domain or that it 181 is a performance failure on the part of their ISP (especially of the 182 ISP's DNS servers). They may contact their ISP to complain, which 183 will incur cost for their ISP. In addition, they may use online 184 tools and sites to complain of this problem, such as via a blog, web 185 forum, or social media site, which may lead to dissatisfaction on the 186 part of other end users or general criticism of an ISP or operator of 187 a DNS recursive resolver. 189 As end users publicize these failures, others may recommend they 190 switch from security-aware DNS resolvers to resolvers not performing 191 DNSSEC validation. This is a shame since the ISP or other DNS 192 recursive resolver operator is actually doing exactly what they are 193 supposed to do in failing to resolve a domain name; this is the 194 expected result when a domain can no longer be validated and it 195 protects end users from a potential security threat. Use of a 196 Negative Trust Anchor would allow the ISP to specifically remedy the 197 failure to reach that domain, without compromising security for other 198 sites. This would result in a satisfied end user, with minimal 199 impact to the ISP, while maintaining the security of DNSSEC for 200 correctly maintained domains. 202 1.4. Switching to a Non-Validating Resolver is Not Recommended 204 As noted in Section 1.3, some people may consider switching to an 205 alternative, non-validating resolver themselves, or may recommend 206 that others do so. But if a domain fails DNSSEC validation and is 207 inaccessible, this could very well be due to a security-related 208 issue. In order to be as safe and secure as possible, end users 209 should not change to DNS servers that do not perform DNSSEC 210 validation as a workaround, and people should not recommend that 211 others do so either. Domains that fail DNSSEC for legitimate reasons 212 (versus misconfiguration) may be in control of hackers or there could 213 be other significant security issues with the domain. 215 Thus, switching to a non-validating resolver to restore access to a 216 domain that fails DNSSEC validation is not a recommended practice, is 217 bad advice to others, is potentially harmful to end user security. 219 2. Use of a Negative Trust Anchor 221 Technical personnel trained in the operation of DNS servers MUST 222 confirm that a failure is due to misconfiguration, as a similar 223 breakage could have occurred if an attacker gained access to a 224 domain's authoritative servers and modified those records or had the 225 domain pointed to their own rogue authoritative servers. They should 226 also confirm that the domain is not intentionally broken, such as for 227 testing purposes as noted in Section 6. Finally, they should make a 228 reasonable attempt to contact the domain owner of the misconfigured 229 zone, preferably prior to implementing the Negative Trust Anchor. 230 Involving trained technical personnel is costly, but operational 231 experience suggests that this is a very rare event, usually on the 232 order of once per quarter (or even less). 234 It is important for the resolver operator to confirm that the domain 235 is still under the ownership / control of the legitimate owner of the 236 domain in order to ensure that disabling validation for a specific 237 domain does not direct users to an address under an attacker's 238 control. Contacting the domain owner and telling them the DNSSEC 239 records that the resolver operator is seeing allows the resolver 240 operator to determine if the issue is a DNSSEC misconfiguration or an 241 attack. 243 In the case of a validation failure due to misconfiguration of a TLD 244 or popular domain name (such as a top 100 website), content or 245 services in the affected TLD or domain could be inaccessible for a 246 large number of users. In such cases, it may be appropriate to use a 247 Negative Trust Anchor as soon as the misconfiguration is confirmed. 248 An example of a list of "top N" websites is the "Alexa Top 500 Sites 249 on the Web" [Alexa], , or a list of the of the most-accessed names in 250 the resolver's cache. 252 Once a domain has been confirmed to fail DNSSEC validation due to a 253 DNSSEC-related misconfiguration, an ISP or other DNS recursive 254 resolver operator may elect to use a Negative Trust Anchor for that 255 domain or sub-domain. This instructs their DNS recursive resolver to 256 temporarily NOT perform DNSSEC validation at or in the misconfigured 257 domain. This immediately restores access to the domain for end users 258 while the domain's administrator corrects the misconfiguration(s). 259 It does not and should not involve turning off validation more 260 broadly. 262 A Negative Trust Anchor MUST only be used for a limited duration. 263 Implementors SHOULD allow the operator using the Negative Trust 264 Anchor to set an end time and date associated with any Negative Trust 265 Anchor. Optimally, this time and date is set in a DNS recursive 266 resolver's configuration, though in the short-term this may also be 267 achieved via other systems or supporting processes. Use of a 268 Negative Trust Anchor MUST NOT be automatic. 270 Finally, a Negative Trust Anchor SHOULD be used only in a specific 271 domain or sub-domain and MUST NOT affect validation of other names up 272 the authentication chain. For example, a Negative Trust Anchor for 273 zone1.example.com would affect only names at or below 274 zone1.example.com, and validation would still be performed on 275 example.com, .com, and the root ("."). This Negative Trust Anchor 276 also SHOULD NOT affect names in another branch of the tree (such as 277 example.net). In another example, a Negative Trust Anchor for 278 example.com would affect only names within example.com, and 279 validation would still be performed on .com, and the root ("."). In 280 this scenario, if there is a (probably manually configured) trust 281 anchor for zone1.example.com, validation would be performed for 282 zone1.example.com and subdomains of zone1.example.com. 284 3. Managing Negative Trust Anchors 286 While Negative Trust Anchors have proven useful during the early 287 stages of DNSSEC adoption, domain owners are ultimately responsible 288 for managing and ensuring their DNS records are configured correctly. 290 Most current implementations of DNS validating resolvers currently 291 follow [RFC4033] on configuring a Trust Anchor using either a public 292 key as in a DNSKEY RR or a hash of a public key as in a DS RR. 294 Different DNS validators may have different configuration names for a 295 Negative Trust Anchor. For examples see Appendix A. 297 An NTA placed at a node where there is a configured positive trust 298 anchor takes precendence over that trust anchor, effectively 299 disabling it. Implementations MAY issue a warning when this occurs. 301 3.1. Alerting Users to NTA Use 303 End users of a DNS recursive resolver or other people may wonder why 304 a domain that fails DNSSEC validation resolves with a supposedly 305 validating resolver. As a result, implementors should consider 306 transparently disclosing those Negative Trust Anchors which are 307 currently in place or were in place in the past, such as on a website 308 [Disclosure-Example]. 310 This is particularly important since there is currently no special 311 DNS query response code that could indicate to end users or 312 applications that a Negative Trust Anchor is in place. Such 313 disclosures should optimally include both the data and time that the 314 Negative Trust Anchor was put in place and when it was removed. 316 4. Removal of a Negative Trust Anchor 318 As explored in Section 8.1, using an NTA once the zone correctly 319 validates can have security considerations. It is therefore 320 RECOMMENDED that NTA implementors SHOULD periodically attempt to 321 validate the domain in question, for the period of time that the 322 Negative Trust Anchor is in place, until such validation is again 323 successful. NTAs MUST expire automatically when their configured 324 lifetime ends. The lifetime MUST NOT exceed a week. Before removing 325 the Negative Trust Anchor, all authoritative resolvers listed in the 326 zone should be checked (due to anycast and load balancers it may not 327 be possible to check all instances). 329 Once all testing succeeds, a Negative Trust Anchor should be removed 330 as soon as is reasonably possible. One possible method to 331 automatically determine when the NTA can be removed is to send a 332 periodic query for type SOA at the NTA node; if it gets a response 333 that it can validate (whether the response was an actual SOA answer 334 or a NOERROR/NODATA with appropriate NSEC/NSEC3 records), the NTA is 335 presumed no longer to be necessary and is removed. Implementations 336 SHOULD, by default, perform this operation. Note that under some 337 circumstances this is undesirable behavior (for example, if 338 www.example.com has a bad signature, but example.com/SOA is fine) and 339 so implementations may wish to allow the operator to override this 340 spot-check / behavior. 342 When removing the NTA, the implementation SHOULD remove all cached 343 entries at and below the NTA node. 345 5. Comparison to Other DNS Misconfigurations 347 Domain administrators are ultimately responsible for managing and 348 ensuring their DNS records are configured correctly. ISPs or other 349 DNS recursive resolver operators cannot and should not correct 350 misconfigured A, CNAME, MX, or other resource records of domains for 351 which they are not authoritative. Expecting non-authoritative 352 entities to protect domain administrators from any misconfiguration 353 of resource records is therefore unrealistic and unreasonable, and in 354 the long-term is harmful to the delegated design of the DNS and could 355 lead to extensive operational instability and/or variation. 357 With DNSSEC breakage, it is often possible to tell that there is a 358 misconfiguration by looking at the data and not needing to guess what 359 it should have been. 361 6. Intentionally Broken Domains 363 Some domains, such as dnssec-failed.org, have been intentionally 364 broken for testing purposes 365 [Measuring-DNSSEC-Validation-of-Website-Visitors] [Netalyzr]. For 366 example, dnssec-failed.org is a DNSSEC-signed domain that is broken. 367 If an end user is querying a validating DNS recursive resolver, then 368 this or other similarly intentionally broken domains should fail to 369 resolve and should result in a "Server Failure" error (RCODE 2, also 370 known as 'SERVFAIL'). If such a domain resolved successfully, then 371 it is a sign that the DNS recursive resolver is not fully validating. 373 Organizations that utilize Negative Trust Anchors should not add a 374 Negative Trust Anchor for any intentionally broken domain. Such 375 additions are prevented by the requirement that the operator attempt 376 to contact the administrators for the zone that has broken DNSSEC. 378 Organizations operating an intentionally broken domain may wish to 379 consider adding a TXT record for the domain to the effect of "This 380 domain is purposely DNSSEC broken for testing purposes". 382 7. Discovering broken domains 384 Discovering that a domain is DNSSEC broken as result of an operator 385 error instead of an attack is not trivial, and the examples here 386 should be vetted by an experienced professional before taking the 387 decision on implementing an negative trust anchor. 389 One of the key thing to look for when looking at a DNSSEC broken 390 domain is consistency and history. It therefore is good if you have 391 the ability to look at the server's DNS traffic over a long period of 392 time or have a database that stores DNS names associated answers 393 (this is often referred to as a "passive DNS database"). Another 394 invaluable tool is dnsviz (http://www.dnsivz.net) which also stores 395 DNSSEC related data historically. The drawback here is that you need 396 to have it test the domain before the incident occurs. 398 The first and easiest thing to check is if the failure of the domain 399 is consistent across different software implementations. If not, you 400 want to inform the vendor where it fails so that the vendor can look 401 more deeply into the issue. 403 The next thing is to figure out what the actual failure mode is. 404 There are several tools to do this, an incomplete list includes: 406 o DNSViz (http://dnsviz.net) 408 o Verisign DNSSEC debugger (http://dnssec-debugger.verisignlabs.com) 410 o iis.se DNS check (http://dnscheck.iis.se) 412 most of these tools are open source and can be installed locally. 413 However, using the tools over the Internet has the advantage of 414 providing visibility from a different point. 416 Once you figure out what the error is, you need to check if it shows 417 consistently around the world and from all authoritative servers. 418 Use DNS Tools (dig) or DNS looking glasses to verify this. An error 419 that is consistently the same is more likely to be operator caused 420 than an attack. Also if the output from the authoritative server is 421 consistently different from the resolvers output this hints to an 422 attack rather then an error, unless there is EDNS0 client subnet 423 (draft-ietf-dnsop-edns-client-subnet) applied to the domain. 425 A last check is to look at the actual DNS data. Is the result of the 426 query still the same or has it changed? While a lot of DNSSEC errors 427 occur on events that change DNSSEC data, the actual record someone 428 wants to go to often stays the same. If the data is the same, this 429 is an indication (not a guarantee) that the error is operator caused. 430 Keep in mind that with DNS being used to globally balance traffic the 431 data associated to a name might be different in different parts of 432 the Internet. 434 Here are some examples of common DNSSEC failures that have been seen 435 as operator signing errors on the Internet: 437 o RRSIG timing issue. Each signature has an inception time and 438 expiry time, between which it is valid. Letting this time expire 439 without creating a new signature is one of the most common DNSSEC 440 errors. To a lesser extent, this also occurs if signatures were 441 made active before the inception time. For all of these errors 442 your primary check is to check on the data. Signature expiration 443 is also about the only error we see on actual data (like 444 www.example.com). All other errors are more or less related to 445 dealing with the chain of trust established by DS records in the 446 parent zone and DNSKEYs in the child zones. These mostly occur 447 during key rollovers, but are not limited to that. 449 o DNSKEYs in child zone don't match the DS record in the parent 450 zone. There is a big variation of this that can happen at any 451 point in the key lifecycle. DNSViz is the best tools to show 452 problems in the chain. If you debug yourself use dig +multiline 453 so that you can see the key id of a DNSKEY. Common Variations of 454 this can be: 456 * DS pointing to a non existent key in the child zone. Questions 457 for consideration here include: Has there ever been a key (and, 458 if so, was it used)? Has there been a recent change in the 459 DNSKEY RRSet (indicating a key rollover)? Has the actual data 460 in the zone changed? Is the zone DNSSEC signed at all and has 461 it been in the past? 463 * DS pointing to an existent key, but no signatures are made with 464 the key. The checks above should be done, with the addition of 465 checking if another key in the DNSKEY RRSet is now used to sign 466 the records. 468 * Data in DS or DNSKEY doesn't match the other. This is more 469 common in initial setup when there was a copy and paste error. 470 Again checking history on data is the best you can do there. 472 All of the above is just a starting point for consideration when 473 deciding whether or not to deploy a trust anchor. It is not possible 474 to provide a simple checklist to run through to determine whether a 475 domain is broken because of an attack or an operator error. 477 8. Other Considerations 479 8.1. Security Considerations 481 End to end DNSSEC validation will be disabled during the time that a 482 Negative Trust Anchor is used. In addition, the Negative Trust 483 Anchor may be in place after the point in time when the DNS 484 misconfiguration that caused validation to break has been fixed. 485 Thus, there may be a gap between when a domain has been re-secured 486 and when a Negative Trust Anchor is removed. In addition, a Negative 487 Trust Anchor may be put in place by DNS recursive resolver operators 488 without the knowledge of the authoritative domain administrator for a 489 given domain name. However, attempts SHOULD be made to contact and 490 inform the domain administrator prior to putting the NTA in place. 492 One side effect of implementing an NTA is that it may break client 493 applications that assume that a domain is signed and expect an AD bit 494 in the response. It is expected that many application that require 495 DNSSEC for a domain will perform their own validation, and so this 496 should not be a major issue. 498 8.2. Privacy Considerations 500 There are no privacy considerations in this document. 502 8.3. IANA Considerations 504 There are no IANA considerations in this document. 506 9. Acknowledgements 508 Several people made contributions of text to this document and/or 509 played an important role in the development and evolution of this 510 document. This in some cases included performing a detailed review 511 of this document and then providing feedback and constructive 512 criticism for future revisions, or engaging in a healthy debate over 513 the subject of the document. All of this was helpful and therefore 514 the following individuals merit acknowledgement: Joe Abley,John 515 Barnitz, Tom Creighton, Marco Davids, Brian Dickson, Patrik Falstrom, 516 Tony Finch, Chris Ganster, Olafur Gudmundsson, Peter Hagopian, Wes 517 Hardaker, Paul Hoffman, Shane Kerr, Murray Kucherawy, Rick Lamb, Marc 518 Lampo, Scott Rose, Ted Lemon, Antoin Verschuren, Paul Vixie, Patrik 519 Wallstrom, W.C.A. Wijngaards, Nick Weaver 520 Edward Lewis, Evan Hunt, Andew Sullivan and Tatuya Jinmei provided 521 especially large amounts of text and / or detailed review. 523 10. References 525 10.1. Normative References 527 [RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S. 528 Rose, "DNS Security Introduction and Requirements", RFC 529 4033, March 2005. 531 [RFC5914] Housley, R., Ashmore, S., and C. Wallace, "Trust Anchor 532 Format", RFC 5914, June 2010. 534 [RFC6781] Kolkman, O., Mekking, W., and R. Gieben, "DNSSEC 535 Operational Practices, Version 2", RFC 6781, December 536 2012. 538 10.2. Informative References 540 [Alexa] Alexa, an Amazon.com Company, "Alexa "The top 500 sites on 541 the web. "", , May 2015, . 543 [Disclosure-Example] 544 Comcast, "faa.gov Failing DNSSEC Validation (Fixed)", 545 Comcast , February 2013, 546 . 549 [Measuring-DNSSEC-Validation-of-Website-Visitors] 550 Mens, J., "Is my Web site being used via a DNSSEC- 551 validator?", July 2012, . 554 [Netalyzr] 555 Weaver, N., Kreibich, C., Nechaev, B., and V. Paxson, 556 "Implications of Netalyzr's DNS Measurements", Securing 557 and Trusting Internet Names, SATIN 2011 SATIN 2011, April 558 2011, . 561 [Unound-Configuration] 562 Wijngaards, W., "Unbound: How to Turn Off DNSSEC", June 563 2010, . 566 Appendix A. Configuration Examples 568 The section contains example configurations to achieve Negative Trust 569 Anchor functionality for the zone foo.example.com. 571 Note: These are simply examples - nameserver operators are expected 572 to test and understand the implications of these operations. Note 573 also that some of available implementations may not implement all 574 recommended functionality in this document. In that case it is 575 advisable to request the developer or vendor of the implementation to 576 support the missing feature, rather than start using the incomplete 577 implementation. 579 A.1. NLNet Labs Unbound 581 Unbound lets us simply disable validation checking for a specific 582 zone by adding configuration statements to unbound.conf: 584 server: 585 domain-insecure: "foo.example.com" 587 Using the 'unbound-control' command one can add and remove Negative 588 Trust Anchors without restarting the nameserver. 590 Using the "unbound-control" command: 591 list_insecure list domain-insecure zones 592 insecure_add zone add domain-insecure zone 593 insecure_remove zone remove domain-insecure zone 595 Items added with the "unbound-control" command are added to the 596 running server and are lost when the server is restarted. Items from 597 unbound.conf stay after restart. 599 For additional information see [Unound-Configuration] 601 A.2. ISC BIND 603 Use the "rndc" command: 605 nta -dump 606 List all negative trust anchors. 607 nta [-lifetime duration] [-force] domain [view] 608 Set a negative trust anchor, disabling DNSSEC validation 609 for the given domain. 610 Using -lifetime specifies the duration of the NTA, up 611 to one week. The default is one hour. 612 Using -force prevents the NTA from expiring before its 613 full lifetime, even if the domain can validate sooner. 614 nta -remove domain [view] 615 Remove a negative trust anchor, re-enabling validation 616 for the given domain. 618 A.3. Nominum Vantio 620 ** 622 *negative-trust-anchors* 624 _Format_: name 626 _Command Channel_: view.update name=world negative-trust- 627 anchors=(foo.example.com) 629 _Command Channel_: resolver.update name=res1 negative-trust- 630 anchors=(foo.example.com) 632 *Description*: Disables DNSSEC validation for a domain, even if the 633 domain is under an existing security root. 635 Appendix B. Document Change Log 637 [RFC Editor: This section is to be removed before publication] 639 -07 to -08 641 o Added some cleanup from Paul Hoffman and Evan Hunt. 643 o Some better text on how to make Unbound do this, provided by 644 W.C.A. Wijngaards. 646 -06 to -07 648 Addressed a large number of comments from Paul Hoffman, Scott Rose 649 and some more from Jinmei. 651 -05 to -06 652 o A bunch of comments from Tony Finch. 654 -04 to -05 656 o A large bunch of cleanups from Jinmei. Thanks! 658 o Also clarified that if there is an NTA at foo.bar.baz.example, and 659 a positive *trust anchor* at bar.baz.example, the most specific 660 wins. I'm not very happy with this text, any additional text 661 gratefully accepted... 663 -03 to -04: 665 o Addressed some comment from an email from Jinmei that I had 666 missed. Turns out others had made many of the same comments, and 667 so most had already been addressed. 669 -02 to -03: 671 o Included text from Ralph into Appendix B 673 o A bunch of comments from Andrew Sullivan ('[DNSOP] negative-trust- 674 anchors-02" - Mar 18th) 676 o Updated keywords 678 -01 to -02: 680 o Gah! I forgot to run spell check. And I type like a chimpanzee 681 with bad hand-eye coordination... 683 -00 to -01: 685 o Stole chunks of text from Ed Lewis' mailing list "tirade" :-) 687 o New rndc usage text from Evan. 689 o Deleted the (already resolved) open issues from Appendix C, moved 690 the unresolved issues into github, resolved them! 692 o Clarification that automated removal is best removal method, and 693 how to implement (Evan Hunt) 695 o Clarify that an NTA is not a RR (Rick Lamb) 697 o Grammar fixes. 699 Ind-07 - WG-00: 701 o Simply updated name to reflect WG doc. 703 Individual-00: First version published as an individual draft. 705 Individual-01: Fixed minor typos and grammatical nits. Closed all 706 open editorial items. 708 Individual-02: Simple date change to keep doc from expiring. 709 Substantive updates planned. 711 Individual-03: Changes to address feedback from Paul Vixie, by adding 712 a new section "Limited Time and Scope of Use". Changes to address 713 issues raised by Antoin Verschuren and Patrik Wallstrom, by adding a 714 new section "Intentionally Broken Domains" and added two related 715 references. Added text to address the need for manual investigation, 716 as suggested by Patrik Falstrom. Added a suggestion on notification 717 as suggested by Marc Lampo. Made several additions and changes 718 suggested by Ralf Weber, Wes Hardaker, Nick Weaver, Tony Finch, Shane 719 Kerr, Joe Abley, Murray Kucherawy, Olafur Gudmundsson. 721 Individual-04: Moved the section defining a NTA forward, and added 722 new text to the Abstract and Introduction per feedback from Paul 723 Hoffman. 725 Individual-05: Incorporated feedback from the DNSOP WG list received 726 on 2/17/13 and 2/18/13. This is likely the final version before the 727 IETF 86 draft cutoff date. Updated references to RFC6781 to RFC6781, 728 per March Davids. 730 Individual-06: Added more OPEN issues to continue tracking WG 731 discussion. No changes in the main document - just expanded issue 732 tracking. 734 Individual-07: Refresh document - needs revision and rework before 735 IETF-91. Planning to add more contributors. 737 o Using github issue tracker - go see https://github.com/wkumari/ 738 draft-livingood-dnsop-negative-trust-anchors for more details. 740 o A bunch of readability improvments. 742 o Issue: Notify the domain owner of the validation failure - 743 resolved. 745 o Issue: Make the NTA as specific as possible - resolved. 747 Authors' Addresses 749 Paul Ebersman 750 Comcast 751 One Comcast Center 752 1701 John F. Kennedy Boulevard 753 Philadelphia, PA 19103 754 US 756 Email: ebersman-ietf@dragon.net 758 Chris Griffiths 760 Email: cgriffiths@gmail.com 762 Warren Kumari 763 Google 764 1600 Amphitheatre Parkway 765 Mountain View, CA 94043 766 US 768 Email: warren@kumari.net 769 URI: http://www.google.com 771 Jason Livingood 772 Comcast 773 One Comcast Center 774 1701 John F. Kennedy Boulevard 775 Philadelphia, PA 19103 776 US 778 Email: jason_livingood@cable.comcast.com 779 URI: http://www.comcast.com 781 Ralf Weber 782 Nominum 784 Email: Ralf.Weber@nominum.com 785 URI: http://www.nominum.com