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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) ** Obsolete normative reference: RFC 2845 (Obsoleted by RFC 8945) ** Obsolete normative reference: RFC 5246 (Obsoleted by RFC 8446) ** Obsolete normative reference: RFC 5996 (Obsoleted by RFC 7296) ** Obsolete normative reference: RFC 6347 (Obsoleted by RFC 9147) == Outdated reference: A later version (-17) exists of draft-ietf-homenet-arch-16 Summary: 4 errors (**), 0 flaws (~~), 2 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 HOMENET D. Migault (Ed) 3 Internet-Draft Orange 4 Intended status: Standards Track W. Cloetens 5 Expires: January 5, 2015 SoftAtHome 6 C. Griffiths 7 Dyn 8 R. Weber 9 Nominum 10 July 4, 2014 12 Outsourcing Home Network Authoritative Naming Service 13 draft-mglt-homenet-front-end-naming-delegation-04.txt 15 Abstract 17 CPEs are designed to provide IP connectivity to home networks. Most 18 CPEs assign IP addresses to the nodes of the home network which makes 19 it a good candidate for hosting the naming service. With IPv6, the 20 naming service makes nodes reachable from the home network as well as 21 from the Internet. 23 However, CPEs have not been designed to host such a naming service 24 exposed on the Internet. This may expose the CPEs to resource 25 exhaustion which would make the home network unreachable, and most 26 probably would also affect the home network inner communications. 28 In addition, DNSSEC management and configuration may not be well 29 understood or mastered by regular end users. Misconfiguration may 30 also results in naming service disruption, thus these end users may 31 prefer to rely on third party naming providers. 33 This document describes a homenet naming architecture where the CPEs 34 manage the DNS zone associates to its home network, and outsources 35 the naming service and eventually the DNSSEC management on the 36 Internet to a third party designated as the Public Authoritative 37 Servers. 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 January 5, 2015. 56 Copyright Notice 58 Copyright (c) 2014 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. Requirements notation . . . . . . . . . . . . . . . . . . . . 3 74 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 75 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 76 4. Architecture Description . . . . . . . . . . . . . . . . . . 5 77 4.1. Architecture Overview . . . . . . . . . . . . . . . . . . 5 78 4.2. Example: DNS(SEC) Homenet Zone . . . . . . . . . . . . . 7 79 4.3. Example: CPE necessary parameters for outsourcing . . . . 9 80 5. Synchronization between CPE and Public Authoritative Servers 10 81 5.1. Synchronization with a Hidden Master . . . . . . . . . . 10 82 5.2. Securing Synchronization . . . . . . . . . . . . . . . . 11 83 5.3. CPE Security Policies . . . . . . . . . . . . . . . . . . 12 84 6. DNSSEC compliant Homenet Architecture . . . . . . . . . . . . 13 85 6.1. Zone Signing . . . . . . . . . . . . . . . . . . . . . . 13 86 6.2. Secure Delegation . . . . . . . . . . . . . . . . . . . . 15 87 7. Handling Different Views . . . . . . . . . . . . . . . . . . 15 88 8. Reverse Zone . . . . . . . . . . . . . . . . . . . . . . . . 15 89 9. Security Considerations . . . . . . . . . . . . . . . . . . . 16 90 9.1. Names are less secure than IP addresses . . . . . . . . . 16 91 9.2. Names are less volatile than IP addresses . . . . . . . . 16 92 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16 93 11. Acknowledgment . . . . . . . . . . . . . . . . . . . . . . . 16 94 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 17 95 12.1. Normative References . . . . . . . . . . . . . . . . . . 17 96 12.2. Informational References . . . . . . . . . . . . . . . . 18 98 Appendix A. Document Change Log . . . . . . . . . . . . . . . . 19 99 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 20 101 1. Requirements notation 103 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 104 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 105 document are to be interpreted as described in [RFC2119]. 107 2. Introduction 109 IPv6 provides global end to end IP reachability. To access services 110 hosted in the home network with IPv6 addresses, end users prefer to 111 use names instead of long and complex IPv6 addresses. 113 CPEs are already providing IPv6 connectivity to the home network and 114 generally provide IPv6 addresses or prefixes to the nodes of the home 115 network. This makes the CPEs a good candidate to manage binding 116 between names and IP addresses of the nodes. In addition, 117 [I-D.ietf-homenet-arch] recommends that home networks be resilient to 118 connectivity disruption from the ISP. This requires that a dedicate 119 device inside the home network manage bindings between names and IP 120 addresses of the nodes and builds the DNS Homenet Zone. All this 121 makes the CPE the natural candidate for setting the DNS(SEC) zone 122 file of the home network. 124 CPEs are usually low powered devices designed for the home network, 125 but not for heavy traffic. As a result, hosting the an authoritative 126 DNS service on the Internet may expose the home network to resource 127 exhaustion, which may isolate the home network from the Internet and 128 affect the services hosted by the CPEs, thus affecting the overall 129 home network communications. 131 In order to avoid resource exhaustion, this document describes an 132 architecture that outsources the authoritative naming service of the 133 home network. More specifically, the DNS(SEC) Homenet Zone built by 134 the CPE is outsourced to Public Authoritative Servers. These servers 135 publish the corresponding DN(SEC) Public Zone on the Internet. 136 Section 4.1 describes the architecture. In order to keep the 137 DNS(SEC) Public Zone up-to-date Section 5 describes how the DNS(SEC) 138 Homenet Zone and the DN(SEC) Public Zone can be synchronized. The 139 proposed architecture aims at deploying DNSSEC and the DNS(SEC) 140 Public Zone is expected to be signed with a secure delegation. The 141 zone signing and secure delegation can be performed either by the CPE 142 or by the Public Authoritative Servers. Section 6 discusses these 143 two alternatives. Section 7 discusses the impact of multiple views 144 and Section 8 discusses the case of the reverse zone. 146 3. Terminology 148 - Customer Premises Equipment: (CPE) is the router providing 149 connectivity to the home network. It is configured and managed 150 by the end user. In this document, the CPE MAY also hosts 151 services such as DHCPv6. This device MAY be provided by the 152 ISP. 154 - Registered Homenet Domain: is the Domain Name associated to the 155 home network. 157 - DNS Homenet Zone: is the DNS zone associated to the home network. 158 This zone is set by the CPE and essentially contains the 159 bindings between names and IP addresses of the nodes of the 160 home network. In this document, the CPE does neither perform 161 any DNSSEC management operations such as zone signing nor 162 provide an authoritative service for the zone. Both are 163 delegated to the Public Authoritative Server. The CPE 164 synchronizes the DNS Homenet Zone with the Public Authoritative 165 Server via a hidden master / slave architecture. The Public 166 Authoritative Server MAY use specific servers for the 167 synchronization of the DNS Homenet Zone: the Public 168 Authoritative Name Server Set as public available name servers 169 for the Registered Homenet Domain. 171 - DNS Homenet Reverse Zone: The reverse zone file associated to the 172 DNS Homenet Zone. 174 - Public Authoritative Server: performs DNSSEC management 175 operations as well as provides the authoritative service for 176 the zone. In this document, the Public Authoritative Server 177 synchronizes the DNS Homenet Zone with the CPE via a hidden 178 master / slave architecture. The Public Authoritative Server 179 acts as a slave and MAY use specific servers called Public 180 Authoritative Name Server Set. Once the Public Authoritative 181 Server synchronizes the DNS Homenet Zone, it signs the zone and 182 generates the DNSSEC Public Zone. Then the Public 183 Authoritative Server hosts the zone as an authoritative server 184 on the Public Authoritative Master(s). 186 - DNSSEC Public Zone: corresponds to the signed version of the DNS 187 Homenet Zone. It is hosted by the Public Authoritative Server, 188 which is authoritative for this zone, and is reachable on the 189 Public Authoritative Master(s). 191 - Public Authoritative Master(s): are the visible name server 192 hosting the DNSSEC Public Zone. End users' resolutions for the 193 Homenet Domain are sent to this server, and this server is a 194 master for the zone. 196 - Public Authoritative Name Server Set: is the server the CPE 197 synchronizes the DNS Homenet Zone. It is configured as a slave 198 and the CPE acts as master. The CPE sends information so the 199 DNSSEC zone can be set and served. 201 - Reverse Public Authoritative Master(s): are the visible name 202 server hosting the DNS Homenet Reverse Zone. End users' 203 resolutions for the Homenet Domain are sent to this server, and 204 this server is a master for the zone. 206 - Reverse Public Authoritative Name Server Set: is the server the 207 CPE synchronizes the DNS Homenet Reverse Zone. It is 208 configured as a slave and the CPE acts as master. The CPE 209 sends information so the DNSSEC zone can be set and served. 211 4. Architecture Description 213 This section describes the architecture for outsourcing the 214 authoritative naming service from the CPE to the Public Authoritative 215 Master(s). Section 4.1 describes the architecture, Section 4.2 and 216 Section 4.3 illustrate this architecture and shows how the DNS(SEC) 217 Homenet Zone should be built by the CPE, as well as lists the 218 necessary parameters the CPE needs to outsource the authoritative 219 naming service. These two section are informational and non 220 normative. 222 4.1. Architecture Overview 224 Figure 1 provides an overview of the architecture. 226 The home network is designated by the Registered Homenet Domain Name 227 -- example.com in Figure 1. The CPE builds the DNS(SEC) Homenet Zone 228 associated to the home network. The content of the DNS(SEC) Homenet 229 Zone is out of the scope of this document. The CPE may host and 230 involve multiple services like a web GUI, DHCP [RFC6644] or mDNS 231 [RFC6762]. These services may coexist and may be used to populate 232 the DNS Homenet Zone. This document assumes the DNS(SEC) Homenet 233 Zone has been populated with domain names that are intended to be 234 publicly published and that are publicly reachable. More 235 specifically, names associated to services or devices that are not 236 expected to be reachable from outside the home network or names bound 237 to non globally reachable IP addresses MUST NOT be part of the 238 DNS(SEC) Homenet Zone. 240 Once the DNS(SEC) Homenet Zone has been built, the CPE does not host 241 the authoritative naming service for it, but instead outsources it to 242 the Public Authoritative Servers. The Public Authoritative Servers 243 take the DNS(SEC) Homenet as an input and publishes the DNS(SEC) 244 Public Zone. In fact the DNS(SEC) Homenet Zone and the DNS(SEC) 245 Public Zone have different names as they may be different. If the 246 CPE does not sign the DNS Homenet Zone, for example, the Public 247 Authoritative Servers may instead sign it on behalf of the CPE. 248 Figure 1 provides a more detailed description of the Public 249 Authoritative Servers, but overall, it is expected that the CPE 250 provides the DNS(SEC) Homenet Zone, the DNS(SEC) Public Zone is 251 derived from the DNS(SEC) Homenet Zone and published on the Internet. 253 As a result, DNS(SEC) queries from the DNS(SEC) Resolvers on the 254 Internet are answered by the Public Authoritative Server and do not 255 reach the CPE. Figure 1 illustrates the case of the resolution of 256 node1.example.com. 258 home network +-------------------+ Internet 259 | | 260 | CPE | 261 | | +----------------------+ 262 +-------+ |+-----------------+| | Public Authoritative | 263 | | || DNS(SEC) Homenet|| | Servers | 264 | node1 | || Zone || |+--------------------+| 265 | | || || ||DNS(SEC) Public Zone|| 266 +-------+ || Homenet Domain ||=========|| || 267 || Name || ^ || (example.com) || 268 node1.\ || (example.com) || | |+--------------------+| 269 example.com |+-----------------+| | +----------------------+ 270 +-------------------+ | ^ | 271 Synchronization | | 272 | | 273 DNSSEC resolution for node1.example.com | v 274 +----------------------+ 275 | | 276 | DNSSEC Resolver | 277 | | 278 +----------------------+ 280 Figure 1: Homenet Naming Architecture Description 282 The Public Authoritative Servers are described in Figure 2. The 283 Public Authoritative Name Server Set receives the DNS(SEC) Homenet 284 Zone as an input. The received zone may be transformed to output the 285 DNS(SEC) Public Zone. Various operations may be performed here, 286 however the one this document considers here is zone signing when the 287 CPE outsources this operation. Implications of such policy are 288 detailed in Section 6 and Section 7. 290 Internet 292 +--------------------------------------------------------+ 293 | Public Authoritative Servers | 294 +--------------------------------------------------------+ 296 +----------------------+ +----------------------+ 297 | | | | 298 | Public Authoritative | | Public Authoritative | 299 | Name Server Set | | Masters | 300 | | | | 301 | +------------------+ | X | +------------------+ | 302 | | DNS(SEC) Homenet | | ^ | | DNS(SEC) Public | | 303 =========>| | Zone | | | | | Zone | | 304 ^ | | | | | | | | | 305 | | | (example.com) | | | | | (example.com) | | 306 | | +------------------+ | | | +------------------+ | 307 | +----------------------+ | +----------------------+ 308 | Homenet to Public Zone 309 Synchronization transformation 310 from the CPE 312 Figure 2: Public Authoritative Servers Description 314 4.2. Example: DNS(SEC) Homenet Zone 316 This section is not normative and intends to illustrate how the CPE 317 builds the DNS(SEC) Homenet Zone. 319 As depicted in Figure 1 and Figure 2, the DNS(SEC) Public Zone is 320 hosted on the Public Authoritative Masters, whereas the DNS(SEC) 321 Homenet Zone is hosted on the CPE. Motivations for keeping these two 322 zones identical are detailed in Section 7, and this section considers 323 that the CPE builds the zone that will be effectively published on 324 the Public Authoritative Masters. In other words "Homenet to Public 325 Zone transformation" is the identity. 327 In that case, the DNS Homenet Zone should configure its Name Server 328 RRset (NS) and Start of Authority (SOA) with the ones associated to 329 the Public Authoritative Masters. This is illustrated in Figure 3. 330 public.masters.example.net is the FQDN of the Public Authoritative 331 Masters, and IP1, IP2, IP3, IP4 are the associated IP addresses. 332 Then the CPE should add the different new nodes that enter the home 333 network, remove those that should be removed and sign the DNS Homenet 334 Zone. 336 $ORIGIN example.com 337 $TTL 1h 339 @ IN SOA public.masters.example.net 340 hostmaster.example.com. ( 341 2013120710 ; serial number of this zone file 342 1d ; slave refresh 343 2h ; slave retry time in case of a problem 344 4w ; slave expiration time 345 1h ; maximum caching time in case of failed 346 ; lookups 347 ) 349 @ NS public.authoritative.servers.example.net 351 public.masters.example.net A @IP1 352 public.masters.example.net A @IP2 353 public.masters.example.net AAAA @IP3 354 public.masters.example.net AAAA @IP4 356 Figure 3: DNS Homenet Zone 358 The SOA RRset is defined in [RFC1033], [RFC1035]. This SOA is 359 specific as it is used for the synchronization between the Hidden 360 Master and the Public Authoritative Name Server Set and published on 361 the DNS Public Authoritative Master. 363 - MNAME: indicates the primary master. In our case the zone is 364 published on the Public Authoritative Master, and its name MUST 365 be mentioned. If multiple Public Authoritative Masters are 366 involved, one of them MUST be chosen. More specifically, the 367 CPE MUST NOT place the name of the Hidden Master. 369 - RNAME: indicates the email address to reach the administrator. 370 [RFC2142] recommends to use hostmaster@domain and replacing the 371 '@' sign by '.'. 373 - REFRESH and RETRY: indicate respectively in seconds how often 374 slaves need to check the master and the time between two 375 refresh when a refresh has failed. Default value indicated by 376 [RFC1033] are 3600 (1 hour) for refresh and 600 (10 minutes) 377 for retry. This value MAY be long for highly dynamic content. 378 However, Public Authoritative Masters and the CPE are expected 379 to implement NOTIFY [RFC1996]. Then short values MAY increase 380 the bandwidth usage for slaves hosting large number of zones. 381 As a result, default values looks fine. 383 EXPIRE: is the upper limit data SHOULD be kept in absence of 384 refresh. Default value indicated by [RFC1033] is 3600000 about 385 42 days. In home network architectures, the CPE provides both 386 the DNS synchronization and the access to the home network. 387 This device MAY be plug / unplugged by the end user without 388 notification, thus we recommend large period. 390 MINIMUM: indicates the minimum TTL. Default value indicated by 391 [RFC1033] is 86400 (1 day). For home network, this value MAY 392 be reduced, and 3600 (1hour) seems more appropriated. 394 4.3. Example: CPE necessary parameters for outsourcing 396 This section specifies the various parameters required by the CPE to 397 configure the naming architecture of this document. This section is 398 informational, and is intended to clarify the information handled by 399 the CPE and the various settings to be done. 401 Public Authoritative Name Server Set may be defined with the 402 following parameters. These parameters are necessary to establish a 403 secure channel between the CPE and the Public Authoritative Name 404 Server Set: 406 - Public Authoritative Name Server Set: The associated FQDNs or IP 407 addresses of the Public Authoritative Server. IP addresses are 408 optional and the FQDN is sufficient. To secure the binding 409 name and IP addresses, a DNSSEC exchange is required. 410 Otherwise, the IP addresses should be entered manually. 412 - Authentication Method: How the CPE authenticates itself to the 413 Public Server. This MAY depend on the implementation but we 414 should consider at least IPsec, DTLS and TSIG 416 - Authentication data: Associated Data. PSK only requires a single 417 argument. If other authentication mechanisms based on 418 certificates are used, then, files for the CPE private keys, 419 certificates and certification authority should be specified. 421 - Public Authoritative Master(s): The FQDN or IP addresses of the 422 Public Authoritative Master. It MAY correspond to the data 423 that will be set in the NS RRsets and SOA of the DNS Homenet 424 Zone. IP addresses are optional and the FQDN is sufficient. 425 To secure the binding name and IP addresses, a DNSSEC exchange 426 is required. Otherwise, the IP addresses should be entered 427 manually. 429 - Registered Homenet Domain: The domain name the Public 430 Authoritative is configured for DNS slave, DNSSEC zone signing 431 and DNSSEC zone hosting. 433 Setting the DNS(SEC) Homenet Zone requires the following information. 435 - Registered Homenet Domain: The Domain Name of the zone. Multiple 436 Registered Homenet Domain may be provided. This will generate 437 the creation of multiple DNS Homenet Zones. 439 - Public Authoritative Server: The Public Authoritative Servers 440 associated to the Registered Homenet Domain. Multiple Public 441 Authoritative Server may be provided. 443 5. Synchronization between CPE and Public Authoritative Servers 445 The DNS(SEC) Homenet Reverse Zone and the DNS Homenet Zone can be 446 updated either with DNS update [RFC2136] or using a master / slave 447 synchronization. The master / slave mechanism is preferred as it 448 better scales and avoids DoS attacks: First the master notifies the 449 slave the zone must be updated, and leaves the slave to proceed to 450 the update when possible. Then, the NOTIFY message sent by the 451 master is a small packet that is less likely to load the slave. At 452 last, the AXFR query performed by the slave is a small packet sent 453 over TCP (section 4.2 [RFC5936]) which makes unlikely the slave to 454 perform reflection attacks with a forged NOTIFY. On the other hand, 455 DNS updates can use UDP, packets require more processing then a 456 NOTIFY, and they do not provide the server the opportunity to post- 457 pone the update. 459 This document recommends the use of a master / slave mechanism 460 instead of the use of nsupdates. This section details the master / 461 slave mechanism. 463 5.1. Synchronization with a Hidden Master 465 Uploading and dynamically updating the zone file on the Public 466 Authoritative Name Server Set can be seen as zone provisioning 467 between the CPE (Hidden Master) and the Public Authoritative Name 468 Server Set (Slave Server). This can be handled either in band or out 469 of band. 471 The Public Authoritative Name Server Set is configured as a slave for 472 the Homenet Domain Name. This slave configuration has been 473 previously agreed between the end user and the provider of the Public 474 Authoritative Servers. In order to set the master/ slave 475 architecture, the CPE acts as a Hidden Master Server, which is a 476 regular Authoritative DNS(SEC) Server listening on the WAN interface. 478 The Hidden Master Server is expected to accept SOA [RFC1033], AXFR 479 [RFC1034], and IXFR [RFC1995] queries from its configured slave DNS 480 servers. The Hidden Master Server SHOULD send NOTIFY messages 481 [RFC1996] in order to update Public DNS server zones as updates 482 occur. Because, DNS Homenet Zones are likely to be small, CPE MUST 483 implement AXFR and SHOULD implement IXFR. 485 Hidden Master Server differs from a regular authoritative server for 486 the home network by: 488 - Interface Binding: the Hidden Master Server listens on the WAN 489 Interface, whereas a regular authoritative server for the home 490 network would listen on the home network interface. 492 - Limited exchanges: the purpose of the Hidden Master Server is to 493 synchronizes with the Public Authoritative Name Server Set, not 494 to serve zone. As a result, exchanges are performed with 495 specific nodes (the Public Authoritative Servers). Then 496 exchange types are limited. The only legitimate exchanges are: 497 NOTIFY initiated by the Hidden Master and IXFR or AXFR 498 exchanges initiated by the Public Authoritative Name Server 499 Set. On the other hand regular authoritative servers would 500 respond any hosts on the home network, and any DNS(SEC) query 501 would be considered. The CPE SHOULD filter IXFR/AXFR traffic 502 and drop traffic not initiated by the Public Authoritative 503 Server. The CPE MUST listen for DNS on TCP and UDP and at 504 least allow SOA lookups to the DNS Homenet Zone. 506 5.2. Securing Synchronization 508 Exchange between the Public Servers and the CPE MUST be secured, at 509 least for integrity protection and for authentication. This is the 510 case whatever mechanism is used between the CPE and the Public 511 Authoritative Name Server Set. 513 TSIG [RFC2845] or SIG(0) [RFC2931] can be used to secure the DNS 514 communications between the CPE and the Public DNS(SEC) Servers. TSIG 515 uses a symmetric key which can be managed by TKEY [RFC2930]. 516 Management of the key involved in SIG(0) is performed through zone 517 updates. How to roll the keys with SIG(0) is out-of-scope of this 518 document. The advantage of these mechanisms is that they are only 519 associated with the DNS application. Not relying on shared libraries 520 ease testing and integration. On the other hand, using TSIG, TKEY or 521 SIG(0) requires that these mechanisms to be implemented on the 522 DNS(SEC) Server's implementation running on the CPE, which adds 523 codes. Another disadvantage is that TKEY does not provides 524 authentication mechanism. 526 Protocols like TLS [RFC5246] / DTLS [RFC6347] can be used to secure 527 the transactions between the Public Authoritative Servers and the 528 CPE. The advantage of TLS/DTLS is that this technology is widely 529 deployed, and most of the boxes already embeds a TLS/DTLS libraries, 530 eventually taking advantage of hardware acceleration. Then TLS/DTLS 531 provides authentication facilities and can use certificates to 532 authenticate the Public Authoritative Server and the CPE. On the 533 other hand, using TLS/DTLS requires to integrate DNS exchange over 534 TLS/DTLS, as well as a new service port. This is why we do not 535 recommend this option. 537 IPsec [RFC4301] IKEv2 [RFC5996] can also be used to secure the 538 transactions between the CPE and the Public Authoritative Servers. 539 Similarly to TLS/DTLS, most CPE already embeds a IPsec stack, and 540 IKEv2 provides multiple authentications possibilities with its EAP 541 framework. In addition, IPsec can be used to protect the DNS 542 exchanges between the CPE and the Public Authoritative Servers 543 without any modifications of the DNS Servers or client. DNS 544 integration over IPsec only requires an additional security policy in 545 the Security Policy Database. One disadvantage of IPsec is that it 546 hardly goes through NATs and firewalls. However, in our case, the 547 CPE is connected to the Internet, and IPsec communication between the 548 CPE and Public Authoritative Server SHOULD NOT be impacted by middle 549 boxes. 551 As mentioned above, TSIG, IPsec and TLS/DTLS may be used to secure 552 transactions between the CPE and the Public Authentication Servers. 553 The CPE and Public Authoritative Server SHOULD implement TSIG and 554 IPsec. 556 How the PSK can be used by any of the TSIG, TLS/DTLS or IPsec 557 protocols. Authentication based on certificates implies a mutual 558 authentication and thus requires the CPE to manage a private key, a 559 public key or certificates as well as Certificate Authorities. This 560 adds complexity to the configuration especially on the CPE side. For 561 this reason, we recommend that CPE MAY use PSK or certificate base 562 authentication and that Public Authentication Servers MUST support 563 PSK and certificate based authentication. 565 5.3. CPE Security Policies 567 This section details security policies related to the Hidden Master / 568 Slave synchronization. 570 The Hidden Master, as described in this document SHOULD drop any 571 queries from the home network. This can be performed with port 572 binding and/or firewall rules. 574 The Hidden Master SHOULD drop on the WAN interface any DNS queries 575 that is not issued from the Public Authoritative Server Name Server 576 Set. 578 The Hidden Master SHOULD drop any outgoing packets other than DNS 579 NOTIFY query, SOA response, IXFR response or AXFR responses. 581 The Hidden Master SHOULD drop any incoming packets other than DNS 582 NOTIFY response, SOA query, IXFR query or AXFR query. 584 The Hidden Master SHOULD drop any non protected IXFR or AXFR 585 exchange. This depends how the synchronization is secured. 587 6. DNSSEC compliant Homenet Architecture 589 [I-D.ietf-homenet-arch] in Section 3.7.3 recommends DNSSEC to be 590 deployed on the both the authoritative server and the resolver. The 591 resolver side is out of scope of this document, and only the 592 authoritative part is considered. 594 Deploying DNSSEC requires signing the zone and configuring a secure 595 delegation. As described in Section 4.1, signing can be performed by 596 the CPE or by the Public Authoritative Servers. Section 6.1 details 597 the implications of these two alternatives. Similarly, the secure 598 delegation can be performed by the CPE or by the Public Authoritative 599 Servers. Section 6.2 discusses these two alternatives. 601 6.1. Zone Signing 603 This section discusses the pros and cons when zone signing is 604 performed by the CPE or by the Public Authoritative Servers. It is 605 recommended to sign the zone by the CPE unless there is a strong 606 argument against it, like a CPE that is not able to sign the zone. 607 In that case zone signing may be performed by the Public 608 Authoritative Servers on behalf of the CPE. 610 Reasons for signing the zone by the CPE are: 612 - 1: Keeping the Homenet Zone and the Public Zone equals. This 613 aspect is discussed in detail in Section 7. More specifically, 614 if the CPE signs the DNS Homenet Zone, then, the CPE has the 615 ability to host the authoritative naming service of the homenet 616 for DNSSEC queries coming from within the network. As a 617 result, a query will be resolved the same way whether it is 618 sent from the home network or from the Internet. On the other 619 hand, if the CPE does not sign the DNS Homenet Zone, either it 620 acts as an authoritative server for the home network or not. 621 If the CPE is an authoritative server for queries initiated 622 from within the home network, then nodes connected to both 623 networks-- the home network and the Internet -- do not have a 624 unique resolution. Devices that may be impacted are mobile 625 phones with Radio Access Network interfaces and WLAN 626 interfaces. Alternatively if the CPE does not act as an 627 authoritative server, it goes against the principles 628 connectivity disruption independence exposed in 629 [I-D.ietf-homenet-arch] section 4.4.1 and 3.7.5. In case of 630 connectivity disruption, naming resolution for nodes inside the 631 home network for nodes in the home network are not possible. 633 - 2: Privacy and Integrity of the DNS Zone are better guaranteed. 634 When the Zone is signed by the CPE, it makes modification of 635 the DNS data -- for example for flow redirection -- not 636 possible. As a result, signing the Homenet Zone by the CPE 637 provides better protection for the end user privacy. 639 Reasons for signing the zone by the Public Authoritative Servers are: 641 - 1: The CPE is not able to sign the zone, most likely because its 642 firmware does not make it possible. However the reason is 643 expected to be less and less valid over time. 645 - 2: Outsourcing DNSSEC management operations. Management 646 operations involve key-roll over which can be done 647 automatically by the CPE and transparently for the end user. 648 As result avoiding DNSSEC management is mostly motivated by bad 649 software implementations. 651 - 3: Reducing the impact of CPE replacement on the Public Zone. 652 Unless the CPE private keys are backuped, CPE replacement 653 results in a emergency key roll over. This can be mitigated 654 also by using relatively small TTLs. 656 - 4: Reducing configuration impacts on the end user. Unless there 657 are some zero configuration mechanisms to provide credentials 658 between the new CPE and the Public Authoritative Name Server 659 Sets. Authentications to Public Authoritative Name Server Set 660 should be re-configured. As CPE replacement is not expected to 661 happen regularly, end users may not be at ease with such 662 configuration settings. However, mechanisms as described in 663 [I-D.mglt-homenet-naming-architecture-dhc-options] use DHCP 664 Options to outsource the configuration and avoid this issue. 666 - 5: Public Authoritative Servers are more likely to handle securely 667 private keys than the CPE. However, having all private 668 information at one place may also balance that risk. 670 6.2. Secure Delegation 672 The secure delegation is set if the DS RRset is properly set in the 673 parent zone. Secure delegation can be performed by the CPE or the 674 Public Authoritative Servers. 676 The DS RRset can be updated manually by the CPE or the Public 677 Authoritative Servers. This can be used then with nsupdate for 678 example bu requires the CPE or the Public Authoritative Server to be 679 authenticated by the Parent Zone Server. Such a trust channel 680 between the CPE and the Parent Zone server may be hard to maintain, 681 and thus may be easier to establish with the Public Authoritative 682 Server. On the other hand, 683 [I-D.ietf-dnsop-delegation-trust-maintainance] may mitigate such 684 issues. 686 7. Handling Different Views 688 The issue raised by handling different views of the DNS Homenet Zone 689 or a DNS Homenet Zone that differs from the Public Zone is that a 690 given DNS query may lead to different responses. The responses may 691 be different values for the queried RRsets or different RCODE or 692 different RRsets types in the responses for DNS/DNSSEC responses. 694 The document does not recommend the CPE manages different views, 695 since devices may be connected to different networks at the same time 696 or may flip / flop from one network to the other. 698 8. Reverse Zone 700 Most of the description considered the DNS Homenet Zone as the non- 701 Reverse Zone. This section is focused on the Reverse Zone. 703 First, all considerations for the DNS Homenet Zone apply to the 704 Reverse Homenet Zone. The main difference between the Reverse DNS 705 Homenet Zone and the DNS Homenet Zone is that the parent zone of the 706 Reverse Homenet Zone is most likely managed by the ISP. As the ISP 707 also provides the IP prefix to the CPE, it may be able to 708 authenticate the CPE. If the Reverse Public Authoritative Name 709 Server Set is managed by the ISP, credentials to authenticate the CPE 710 for the zone synchronization may be set automatically and 711 transparently to the end user. 712 [I-D.mglt-homenet-naming-architecture-dhc-options] describes how 713 automatic configuration may be performed. 715 9. Security Considerations 717 The Homenet Naming Architecture described in this document solves 718 exposing the CPE's DNS service as a DoS attack vector. 720 9.1. Names are less secure than IP addresses 722 This document describes how an End User can make his services and 723 devices from his home network reachable on the Internet with Names 724 rather than IP addresses. This exposes the home network to attackers 725 since names are expected to provide less randomness than IP 726 addresses. The naming delegation protects the End User's privacy by 727 not providing the complete zone of the home network to the ISP. 728 However, using the DNS with names for the home network exposes the 729 home network and its components to dictionary attacks. In fact, with 730 IP addresses, the Interface Identifier is 64 bit length leading to 731 2^64 possibilities for a given subnetwork. This is not to mention 732 that the subnet prefix is also of 64 bit length, thus providing 733 another 2^64 possibilities. On the other hand, names used either for 734 the home network domain or for the devices present less randomness 735 (livebox, router, printer, nicolas, jennifer, ...) and thus exposes 736 the devices to dictionary attacks. 738 9.2. Names are less volatile than IP addresses 740 IP addresses may be used to locate a device, a host or a Service. 741 However, home networks are not expected to be assigned the same 742 Prefix over time. As a result observing IP addresses provides some 743 ephemeral information about who is accessing the service. On the 744 other hand, Names are not expected to be as volatile as IP addresses. 745 As a result, logging Names, over time, may be more valuable that 746 logging IP addresses, especially to profile End User's 747 characteristics. 749 PTR provides a way to bind an IP address to a Name. In that sense 750 responding to PTR DNS queries may affect the End User's Privacy. For 751 that reason we recommend that End Users may choose to respond or not 752 to PTR DNS queries and may return a NXDOMAIN response. 754 10. IANA Considerations 756 This document has no actions for IANA. 758 11. Acknowledgment 760 The authors wish to thank Philippe Lemordant for its contributions on 761 the early versions of the draft, Ole Troan for pointing out issues 762 with the IPv6 routed home concept and placing the scope of this 763 document in a wider picture, Mark Townsley for encouragement and 764 injecting a healthy debate on the merits of the idea, Ulrik de Bie 765 for providing alternative solutions, Paul Mockapetris, Christian 766 Jacquenet, Francis Dupont and Ludovic Eschard for their remarks on 767 CPE and low power devices, Olafur Gudmundsson for clarifying DNSSEC 768 capabilities of small devices, Simon Kelley for its feedback as 769 dnsmasq implementer. Andrew Sullivan, Mark Andrew, Ted Lemon, Mikael 770 Abrahamson and Michael Richardson, Ray Bellis for their feed backs on 771 handling different views as well as clarifying the impact of 772 outsourcing the zone signing operation outside the CPE. 774 12. References 776 12.1. Normative References 778 [RFC1034] Mockapetris, P., "Domain names - concepts and facilities", 779 STD 13, RFC 1034, November 1987. 781 [RFC1035] Mockapetris, P., "Domain names - implementation and 782 specification", STD 13, RFC 1035, November 1987. 784 [RFC1995] Ohta, M., "Incremental Zone Transfer in DNS", RFC 1995, 785 August 1996. 787 [RFC1996] Vixie, P., "A Mechanism for Prompt Notification of Zone 788 Changes (DNS NOTIFY)", RFC 1996, August 1996. 790 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 791 Requirement Levels", BCP 14, RFC 2119, March 1997. 793 [RFC2136] Vixie, P., Thomson, S., Rekhter, Y., and J. Bound, 794 "Dynamic Updates in the Domain Name System (DNS UPDATE)", 795 RFC 2136, April 1997. 797 [RFC2142] Crocker, D., "MAILBOX NAMES FOR COMMON SERVICES, ROLES AND 798 FUNCTIONS", RFC 2142, May 1997. 800 [RFC2845] Vixie, P., Gudmundsson, O., Eastlake, D., and B. 801 Wellington, "Secret Key Transaction Authentication for DNS 802 (TSIG)", RFC 2845, May 2000. 804 [RFC2930] Eastlake, D., "Secret Key Establishment for DNS (TKEY 805 RR)", RFC 2930, September 2000. 807 [RFC2931] Eastlake, D., "DNS Request and Transaction Signatures ( 808 SIG(0)s)", RFC 2931, September 2000. 810 [RFC4301] Kent, S. and K. Seo, "Security Architecture for the 811 Internet Protocol", RFC 4301, December 2005. 813 [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security 814 (TLS) Protocol Version 1.2", RFC 5246, August 2008. 816 [RFC5936] Lewis, E. and A. Hoenes, "DNS Zone Transfer Protocol 817 (AXFR)", RFC 5936, June 2010. 819 [RFC5996] Kaufman, C., Hoffman, P., Nir, Y., and P. Eronen, 820 "Internet Key Exchange Protocol Version 2 (IKEv2)", RFC 821 5996, September 2010. 823 [RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer 824 Security Version 1.2", RFC 6347, January 2012. 826 [RFC6644] Evans, D., Droms, R., and S. Jiang, "Rebind Capability in 827 DHCPv6 Reconfigure Messages", RFC 6644, July 2012. 829 [RFC6762] Cheshire, S. and M. Krochmal, "Multicast DNS", RFC 6762, 830 February 2013. 832 12.2. Informational References 834 [I-D.ietf-dnsop-delegation-trust-maintainance] 835 Kumari, W., Gudmundsson, O., and G. Barwood, "Automating 836 DNSSEC Delegation Trust Maintenance", draft-ietf-dnsop- 837 delegation-trust-maintainance-14 (work in progress), June 838 2014. 840 [I-D.ietf-homenet-arch] 841 Chown, T., Arkko, J., Brandt, A., Troan, O., and J. Weil, 842 "IPv6 Home Networking Architecture Principles", draft- 843 ietf-homenet-arch-16 (work in progress), June 2014. 845 [I-D.mglt-homenet-naming-architecture-dhc-options] 846 Migault, D., Cloetens, W., Griffiths, C., and R. Weber, 847 "DHCP Options for Homenet Naming Architecture", draft- 848 mglt-homenet-naming-architecture-dhc-options-02 (work in 849 progress), July 2014. 851 [RFC1033] Lottor, M., "Domain administrators operations guide", RFC 852 1033, November 1987. 854 Appendix A. Document Change Log 856 [RFC Editor: This section is to be removed before publication] 858 -04: 860 *Clarifications on zone signing 862 *Rewording 864 *Adding section on different views 866 *architecture clarifications 868 -03: 870 *Simon's comments taken into consideration 872 *Adding SOA, PTR considerations 874 *Removing DNSSEC performance paragraphs on low power devices 876 *Adding SIG(0) as a mechanism for authenticating the servers 878 *Goals clarification: the architecture described in the document 1) 879 does not describe new protocols, and 2) can be adapted to specific 880 cases for advance users. 882 -02: 884 *remove interfaces: "Public Authoritative Server Naming Interface" is 885 replaced by "Public Authoritative Master(s)". "Public Authoritative 886 Server Management Interface" is replaced by "Public Authoritative 887 Name Server Set". 889 -01.3: 891 *remove the authoritative / resolver services of the CPE. 892 Implementation dependent 894 *remove interactions with mdns and dhcp. Implementation dependent. 896 *remove considerations on low powered devices 898 *remove position toward homenet arch 900 *remove problem statement section 901 -01.2: 903 * add a CPE description to show that the architecture can fit CPEs 905 * specification of the architecture for very low powered devices. 907 * integrate mDNS and DHCP interactions with the Homenet Naming 908 Architecture. 910 * Restructuring the draft. 1) We start from the homenet-arch draft to 911 derive a Naming Architecture, then 2) we show why CPE need mechanisms 912 that do not expose them to the Internet, 3) we describe the 913 mechanisms. 915 * I remove the terminology and expose it in the figures A and B. 917 * remove the Front End Homenet Naming Architecture to Homenet Naming 919 -01: 921 * Added C. Griffiths as co-author. 923 * Updated section 5.4 and other sections of draft to update section 924 on Hidden Master / Slave functions with CPE as Hidden Master/Homenet 925 Server. 927 * For next version, address functions of MDNS within Homenet Lan and 928 publishing details northbound via Hidden Master. 930 -00: First version published. 932 Authors' Addresses 934 Daniel Migault 935 Orange 936 38 rue du General Leclerc 937 92794 Issy-les-Moulineaux Cedex 9 938 France 940 Phone: +33 1 45 29 60 52 941 Email: daniel.migault@orange.com 942 Wouter Cloetens 943 SoftAtHome 944 vaartdijk 3 701 945 3018 Wijgmaal 946 Belgium 948 Email: wouter.cloetens@softathome.com 950 Chris Griffiths 951 Dyn 952 150 Dow Street 953 Manchester, NH 03101 954 US 956 Email: cgriffiths@dyn.com 957 URI: http://dyn.com 959 Ralf Weber 960 Nominum 961 2000 Seaport Blvd #400 962 Redwood City, CA 94063 963 US 965 Email: ralf.weber@nominum.com 966 URI: http://www.nominum.com