idnits 2.17.1 draft-ietf-intarea-provisioning-domains-11.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- No issues found here. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year -- The document date (January 31, 2020) is 1545 days in the past. Is this intentional? 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 2818 (Obsoleted by RFC 9110) ** Obsolete normative reference: RFC 4941 (Obsoleted by RFC 8981) ** Obsolete normative reference: RFC 7525 (Obsoleted by RFC 9325) ** Downref: Normative reference to an Informational RFC: RFC 7556 -- Obsolete informational reference (is this intentional?): RFC 6125 (Obsoleted by RFC 9525) -- Obsolete informational reference (is this intentional?): RFC 7049 (Obsoleted by RFC 8949) -- Obsolete informational reference (is this intentional?): RFC 7540 (Obsoleted by RFC 9113) Summary: 4 errors (**), 0 flaws (~~), 1 warning (==), 4 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group P. Pfister 3 Internet-Draft E. Vyncke 4 Intended status: Standards Track Cisco 5 Expires: August 3, 2020 T. Pauly 6 Apple Inc. 7 D. Schinazi 8 Google LLC 9 W. Shao 10 Cisco 11 January 31, 2020 13 Discovering Provisioning Domain Names and Data 14 draft-ietf-intarea-provisioning-domains-11 16 Abstract 18 Provisioning Domains (PvDs) are defined as consistent sets of network 19 configuration information. This allows hosts to manage connections 20 to multiple networks and interfaces simultaneously, such as when a 21 home router provides connectivity through both a broadband and 22 cellular network provider. 24 This document defines a mechanism for explicitly identifying PvDs 25 through a Router Advertisement (RA) option. This RA option announces 26 a PvD identifier, which hosts can compare to differentiate between 27 PvDs. The option can directly carry some information about a PvD and 28 can optionally point to additional PvD information that can be 29 retrieved using HTTP over TLS. 31 Status of This Memo 33 This Internet-Draft is submitted in full conformance with the 34 provisions of BCP 78 and BCP 79. 36 Internet-Drafts are working documents of the Internet Engineering 37 Task Force (IETF). Note that other groups may also distribute 38 working documents as Internet-Drafts. The list of current Internet- 39 Drafts is at https://datatracker.ietf.org/drafts/current/. 41 Internet-Drafts are draft documents valid for a maximum of six months 42 and may be updated, replaced, or obsoleted by other documents at any 43 time. It is inappropriate to use Internet-Drafts as reference 44 material or to cite them other than as "work in progress." 46 This Internet-Draft will expire on August 3, 2020. 48 Copyright Notice 50 Copyright (c) 2020 IETF Trust and the persons identified as the 51 document authors. All rights reserved. 53 This document is subject to BCP 78 and the IETF Trust's Legal 54 Provisions Relating to IETF Documents 55 (https://trustee.ietf.org/license-info) in effect on the date of 56 publication of this document. Please review these documents 57 carefully, as they describe your rights and restrictions with respect 58 to this document. Code Components extracted from this document must 59 include Simplified BSD License text as described in Section 4.e of 60 the Trust Legal Provisions and are provided without warranty as 61 described in the Simplified BSD License. 63 Table of Contents 65 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 66 1.1. Specification of Requirements . . . . . . . . . . . . . . 4 67 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 68 3. Provisioning Domain Identification using Router 69 Advertisements . . . . . . . . . . . . . . . . . . . . . . . 5 70 3.1. PvD ID Option for Router Advertisements . . . . . . . . . 5 71 3.2. Router Behavior . . . . . . . . . . . . . . . . . . . . . 8 72 3.3. Non-PvD-aware Host Behavior . . . . . . . . . . . . . . . 9 73 3.4. PvD-aware Host Behavior . . . . . . . . . . . . . . . . . 9 74 3.4.1. DHCPv6 configuration association . . . . . . . . . . 10 75 3.4.2. DHCPv4 configuration association . . . . . . . . . . 11 76 3.4.3. Connection Sharing by the Host . . . . . . . . . . . 11 77 3.4.4. Usage of DNS Servers . . . . . . . . . . . . . . . . 12 78 4. Provisioning Domain Additional Information . . . . . . . . . 13 79 4.1. Retrieving the PvD Additional Information . . . . . . . . 13 80 4.2. Operational Consideration to Providing the PvD Additional 81 Information . . . . . . . . . . . . . . . . . . . . . . . 16 82 4.3. PvD Additional Information Format . . . . . . . . . . . . 16 83 4.3.1. Example . . . . . . . . . . . . . . . . . . . . . . . 18 84 4.4. Detecting misconfiguration and misuse . . . . . . . . . . 18 85 5. Operational Considerations . . . . . . . . . . . . . . . . . 19 86 5.1. Exposing Extra RA Options to PvD-Aware Hosts . . . . . . 19 87 5.2. Different RAs for PvD-Aware and Non-PvD-Aware Hosts . . . 19 88 5.3. Enabling Multi-homing for PvD-Aware Hosts . . . . . . . . 21 89 5.4. Providing Additional Information to PvD-Aware Hosts . . . 22 90 6. Security Considerations . . . . . . . . . . . . . . . . . . . 23 91 7. Privacy Considerations . . . . . . . . . . . . . . . . . . . 24 92 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 25 93 8.1. New entry in the Well-Known URIs Registry . . . . . . . . 26 94 8.2. Additional Information PvD Keys Registry . . . . . . . . 26 95 8.3. PvD Option Flags Registry . . . . . . . . . . . . . . . . 26 96 8.4. PvD JSON Media Type Registration . . . . . . . . . . . . 27 97 9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 28 98 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 28 99 10.1. Normative References . . . . . . . . . . . . . . . . . . 28 100 10.2. Informative References . . . . . . . . . . . . . . . . . 30 101 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 32 103 1. Introduction 105 Provisioning Domains (PvDs) are defined in [RFC7556] as consistent 106 sets of network configuration information. This information includes 107 properties that are traditionally associated with a single networking 108 interface, such as source addresses, DNS configuration, proxy 109 configuration, and gateway addresses. 111 Clients that are aware of PvDs can take advantage of multiple network 112 interfaces simultaneously. This enables using two PvDs in parallel 113 for separate connections or for multi-path transports. 115 While most PvDs today are discovered implicitly (such as by receiving 116 information via Router Advertisements from a router on a network that 117 a client host directly connects to), [RFC7556] also defines the 118 notion of Explicit PvDs. IPsec Virtual Private Networks are 119 considered Explicit PvDs, but Explicit PvDs can also be discovered 120 via the local network router. Discovering Explicit PvDs allows two 121 key advancements in managing multiple PvDs: 123 1. The ability to discover and use multiple PvDs on a single 124 interface, such as when a local router can provide connectivity 125 to two different Internet Service Providers. 127 2. The ability to associate additional information about PvDs to 128 describe the properties of the network. 130 While [RFC7556] defines the concept of Explicit PvDs, it does not 131 define the mechanism for discovering multiple Explicit PvDs on a 132 single network and their additional information. 134 This document specifies a way to identify PvDs with Fully Qualified 135 Domain Names (FQDN), called PvD IDs. Those identifiers are 136 advertised in a new Router Advertisement (RA) [RFC4861] option called 137 the PvD ID Router Advertisement option which, when present, 138 associates the PvD ID with all the information present in the Router 139 Advertisement as well as any configuration object, such as addresses, 140 derived from it. The PVD ID Router Advertisement option may also 141 contain a set of other RA options, along with an optional inner 142 Router Advertisement message header. These options and optional 143 inner header are only visible to 'PvD-aware' hosts, allowing such 144 hosts to have a specialized view of the network configuration. 146 Since PvD IDs are used to identify different ways to access the 147 internet, multiple PvDs (with different PvD IDs) can be provisioned 148 on a single host interface. Similarly, the same PvD ID could be used 149 on different interfaces of a host in order to inform that those PvDs 150 ultimately provide equivalent services. 152 This document also introduces a mechanism for hosts to retrieve 153 optional additional information related to a specific PvD by means of 154 an HTTP over TLS query using a URI derived from the PvD ID. The 155 retrieved JSON object contains additional information that would 156 typically be considered too large to be directly included in the 157 Router Advertisement, but might be considered useful to the 158 applications, or even sometimes users, when choosing which PvD should 159 be used. 161 For example, if Alice has both a cellular network provider and a 162 broadband provider in her home, her PvD-aware devices and 163 applications would be aware of both available uplinks. These 164 applications could fail-over between these networks, or run 165 connections over both (potentially using multi-path transports). 166 Applications could also select specific uplinks based on the 167 properties of the network; for example, if the cellular network 168 provides free high-quality video streaming, a video-streaming 169 application could select that network while most of the other traffic 170 on Alice's device uses the broadband provider. 172 1.1. Specification of Requirements 174 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 175 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 176 "OPTIONAL" in this document are to be interpreted as described in BCP 177 14 [RFC2119] [RFC8174] when, and only when, they appear in all 178 capitals, as shown here. 180 2. Terminology 182 This document uses the following terminology: 184 Provisioning Domain (PvD): A set of network configuration 185 information; for more information, see [RFC7556]. 187 PvD ID: A Fully Qualified Domain Name (FQDN) used to identify a PvD. 189 Explicit PvD: A PvD uniquely identified with a PvD ID. For more 190 information, see [RFC7556]. 192 Implicit PvD: A PvD that, in the absence of a PvD ID, is identified 193 by the host interface to which it is attached and the address of 194 the advertising router. See also [RFC7556]. 196 PvD-aware host: A host that supports the association of network 197 configuration information into PvDs and the use of these PvDs as 198 described in this document. Also named PvD-aware node in 199 [RFC7556]. 201 3. Provisioning Domain Identification using Router Advertisements 203 Explicit PvDs are identified by a PvD ID. The PvD ID is a Fully 204 Qualified Domain Name (FQDN) that identifies the network operator. 205 Network operators MUST use names that they own or manage to avoid 206 naming conflicts. The same PvD ID MAY be used in several access 207 networks when they ultimately provide identical services (e.g., in 208 all home networks subscribed to the same service); else, the PvD ID 209 MUST be different to follow Section 2.4 of [RFC7556]. 211 3.1. PvD ID Option for Router Advertisements 213 This document introduces a Router Advertisement (RA) option called 214 the PvD Option. It is used to convey the FQDN identifying a given 215 PvD (see Figure 1), bind the PvD ID with configuration information 216 received over DHCPv4 (see Section 3.4.2), enable the use of HTTP over 217 TLS to retrieve the PvD Additional Information JSON object (see 218 Section 4), as well as contain any other RA options which would 219 otherwise be valid in the RA. 221 0 1 2 3 222 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 223 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 224 | Type | Length |H|L|R| Reserved | Delay | 225 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 226 | Sequence Number | ... 227 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ... 228 ... PvD ID FQDN ... 229 ... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 230 ... | Padding | 231 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 232 | ... 233 ... Router Advertisement message header ... 234 ... (Only present when R-flag is set) ... 235 ... | 236 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 237 | Options ... 238 +-+-+-+-+-+-+-+-+-+-+-+- 240 Figure 1: PvD ID Router Advertisements Option Format 242 Type: (8 bits) Set to 21. 244 Length: (8 bits) The length of the option in units of 8 octets, 245 including the Type and Length fields, the Router Advertisement 246 message header, if any, as well as the RA options that are 247 included within the PvD Option. 249 H-flag: (1 bit) 'HTTP' flag stating whether some PvD Additional 250 Information is made available through HTTP over TLS, as described 251 in Section 4. 253 L-flag: (1 bit) 'Legacy' flag stating whether the PvD is associated 254 with IPv4 information assigned using DHCPv4 (see Section 3.4.2). 256 R-flag: (1 bit) 'Router Advertisement' flag stating whether the PvD 257 Option header is followed (right after padding to the next 64 bits 258 boundary) by a Router Advertisement message header (see section 259 4.2 of [RFC4861]). The usage of the inner message header is 260 described in Section 3.4. 262 Reserved: (13 bits) Reserved for later use. It MUST be set to zero 263 by the sender and ignored by the receiver. 265 Delay: (4 bits) Unsigned integer used to delay HTTP GET queries from 266 hosts by a randomized backoff (see Section 4.1). If the H-flag is 267 not set, senders SHOULD set the delay to zero, and receivers 268 SHOULD ignore the value. 270 Sequence Number: (16 bits) Sequence number for the PvD Additional 271 Information, as described in Section 4. If the H-flag is not set, 272 senders SHOULD set the Sequence Number to zero, and receivers 273 SHOULD ignore the value. 275 PvD ID FQDN: The FQDN used as PvD ID encoded in DNS format, as 276 described in Section 3.1 of [RFC1035]. Domain name compression 277 described in Section 4.1.4 of [RFC1035] MUST NOT be used. 279 Padding: Zero or more padding octets to the next 8 octet boundary 280 (see Section 4.6 of [RFC4861]). It MUST be set to zero by the 281 sender, and ignored by the receiver. 283 RA message header: (16 octets) When the R-flag is set, a full Router 284 Advertisement message header as specified in [RFC4861]. The 285 sender MUST set the 'Type' to 134, the value for "Router 286 Advertisement", and set the 'Code' to 0. Receivers MUST ignore 287 both of these fields. The 'Checksum' MUST be set to 0 by the 288 sender; non-zero checksums MUST be ignored by the receiver without 289 causing the processing of the message to fail. All other fields 290 are to be set and parsed as specified in [RFC4861] or any updating 291 documents. 293 Options: Zero or more RA options that would otherwise be valid as 294 part of the Router Advertisement main body, but are instead 295 included in the PvD Option so as to be ignored by hosts that are 296 not PvD-aware. 298 Figure 2 shows an example of a PvD Option with "example.org" as the 299 PvD ID FQDN and including both a Recursive DNS Server (RDNSS) option 300 and a prefix information option. It has a Sequence Number of 123, 301 and indicates the presence of additional information that is expected 302 to be fetched with a delay factor of 1. 304 0 1 2 3 305 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 306 +---------------+-----------------------------------------------+ 307 | Type: 21 | Length: 12 |1|0|0| Reserved |Delay:1| 308 +---------------+-------------------------------+---------------+ 309 | Seq number: 123 | 7 | e | 310 +---------------+-----------------------------------------------+ 311 | x | a | m | p | 312 +---------------------------------------------------------------+ 313 | l | e | 3 | o | 314 +---------------------------------------------------------------+ 315 | r | g | 0 | 0 (padding) | 316 +---------------------------------------------------------------+ 317 | 0 (padding) | 0 (padding) | 0 (padding) | 0 (padding) | 318 +---------------+---------------+---------------+---------------+ 319 | RDNSS option (RFC 8106) length: 5 ... 320 ... ... 321 ... | 322 +---------------------------------------------------------------+ 323 | Prefix Information Option (RFC 4861) length: 4 ... 324 ... | 325 ... | 326 +---------------------------------------------------------------+ 328 Figure 2 330 3.2. Router Behavior 332 A router MAY send RAs containing one PvD Option, but MUST NOT include 333 more than one PvD Option in each RA. The PvD Option MUST NOT contain 334 further PvD Options. 336 The PvD Option MAY contain zero, one, or more RA options which would 337 otherwise be valid as part of the same RA. Such options are 338 processed by PvD-aware hosts, while ignored by other hosts as per 339 section 4.2 of [RFC4861]. 341 In order to provide multiple different PvDs, a router MUST send 342 multiple RAs. RAs sent from different link-local source addresses 343 establish distinct implicit PvDs, in the absence of a PvD Option. 344 Explicit PvDs MAY share link-local source addresses with an Implicit 345 PvD and any number of other Explicit PvDs. 347 In other words, different Explicit PvDs MAY be advertised with RAs 348 using the same link-local source address; but different Implicit 349 PvDs, advertised by different RAs, MUST use different link-local 350 addresses because these Implicit PvDs are identified by the source 351 addresses of the RAs. If a link-local address on the router is 352 changed, then any new RA will be interpreted as a different Implicit 353 PvD by PvD-aware hosts. 355 As specified in [RFC4861] and [RFC6980], when the set of options 356 causes the size of an advertisement to exceed the link MTU, multiple 357 router advertisements MUST be sent to avoid fragmentation, each 358 containing a subset of the options. In such cases, the PvD Option 359 header (i.e., all fields except the 'Options' field) MUST be repeated 360 in all the transmitted RAs. The options within the 'Options' field, 361 MAY be transmitted only once, included in one of the transmitted PvD 362 Options. 364 3.3. Non-PvD-aware Host Behavior 366 As the PvD Option has a new option code, non-PvD-aware hosts will 367 simply ignore the PvD Option and all the options it contains (see 368 section 4.2 of [RFC4861]. This ensures the backward compatibility 369 required in Section 3.3 of [RFC7556]. This behavior allows for a 370 mixed-mode network where a mix of PvD-aware and non-PvD-aware hosts 371 coexist. 373 3.4. PvD-aware Host Behavior 375 Hosts MUST associate received RAs and included configuration 376 information (e.g., Router Valid Lifetime, Prefix Information 377 [RFC4861], Recursive DNS Server [RFC8106], Routing Information 378 [RFC4191] options) with the Explicit PvD identified by the first PvD 379 Option present in the received RA, if any, or with the Implicit PvD 380 identified by the host interface and the source address of the 381 received RA otherwise. If an RA message header is present both 382 within the PvD Option and outside it, the header within the PvD 383 Option takes precedence. 385 In case multiple PvD Options are found in a given RA, hosts MUST 386 ignore all but the first PvD Option. 388 If a host receives PvD Options flags that it does not recognize 389 (currently in the Reserved field), it MUST ignore these flags. 391 Similarly, hosts MUST associate all network configuration objects 392 (e.g., default routers, addresses, more specific routes, DNS 393 Recursive Resolvers) with the PvD associated with the RA that 394 provisioned the object. For example, addresses that are generated 395 using a received Prefix Information option (PIO) are associated with 396 the PvD of the last received RA which included the given PIO. 398 PvD IDs MUST be compared in a case-insensitive manner as defined by 399 [RFC4343]. For example, "pvd.example.com." or "PvD.Example.coM." 400 would refer to the same PvD. 402 While performing PvD-specific operations such as resolving names, 403 executing the default address selection algorithm [RFC6724] or 404 executing the default router selection algorithm when forwarding 405 packets ([RFC4861], [RFC4191] and [RFC8028]), hosts and applications 406 MAY consider only the configuration associated with any non-empty 407 subset of PvDs. For example, a host MAY associate a given process 408 with a specific PvD, or a specific set of PvDs, while associating 409 another process with another PvD. A PvD-aware application might also 410 be able to select, on a per-connection basis, which PvDs should be 411 used. In particular, constrained devices such as small battery 412 operated devices (e.g., IoT), or devices with limited CPU or memory 413 resources may purposefully use a single PvD while ignoring some 414 received RAs containing different PvD IDs. 416 The way an application expresses its desire to use a given PvD, or a 417 set of PvDs, or the way this selection is enforced, is out of the 418 scope of this document. Useful insights about these considerations 419 can be found in [I-D.kline-mif-mpvd-api-reqs]. 421 3.4.1. DHCPv6 configuration association 423 When a host retrieves stateless configuration elements using DHCPv6 424 (e.g., DNS recursive resolvers or DNS domain search lists [RFC3646]), 425 they MUST be associated with all the explicit and implicit PvDs 426 received on the same interface and contained in a RA with the O-flag 427 set [RFC4861]. 429 When a host retrieves stateful assignments using DHCPv6, such 430 assignments MUST be associated with the received PvD which was 431 received with RAs with the M-flag set and including a matching PIO. 432 A PIO is considered to match a DHCPv6 assignment when the IPv6 prefix 433 from the PIO includes the assignment from DHCPv6. For example, if a 434 PvD's associated PIO defines the prefix 2001:db8:cafe::/64, a DHCPv6 435 IA_NA message that assigns the address 2001:db8:cafe::1234:4567 would 436 be considered to match. 438 In cases where an address would be assigned by DHCPv6 and no matching 439 PvD could be found, hosts MAY associate the assigned address with any 440 implicit PvD received on the same interface or to multiple implicit 441 PvDs received on the same interface. This is intended to resolve 442 backward compatibility issues with rare deployments choosing to 443 assign addresses with DHCPv6 while not sending any matching PIO. 444 Implementations are suggested to flag or log such scenarios as errors 445 to help detect misconfigurations. 447 3.4.2. DHCPv4 configuration association 449 Associating DHCPv4 [RFC2131] configuration elements with Explicit 450 PvDs allows hosts to treat a set of IPv4 and IPv6 configurations as a 451 single PvD with shared properties. For example, consider a router 452 that provides two different uplinks. One could be a broadband 453 network that has data rate and streaming properties described in PvD 454 additional information and that provides both IPv4 and IPv6 network 455 access. The other could be a cellular network that provides only 456 IPv6 network access, and uses NAT64 [RFC6146]. The broadband network 457 can be represented by an Explicit PvD that points to the additional 458 information, and also marks association with DHCPv4 information. The 459 cellular network can be represented by a different Explicit PvD that 460 is not associated with DHCPv4. 462 When a PvD-aware host retrieves configuration elements from DHCPv4, 463 the information is associated either with a single Explicit PvD on 464 that interface, or else with all Implicit PvDs on the same interface. 466 An Explicit PvD indicates its association with DHCPv4 information by 467 setting the L-flag in the PvD RA Option. If there is exactly one 468 Explicit PvD that sets this flag, hosts MUST associate the DHCPv4 469 information with that PvD. Multiple Explicit PvDs on the same 470 interface marking this flag is a misconfiguration, and hosts SHOULD 471 NOT associate the DHCPv4 information with any Explicit PvD in this 472 case. 474 If no single Explicit PvD claims association with DHCPv4, the 475 configuration elements coming from DHCPv4 MUST be associated with all 476 Implicit PvDs identified by the interface on which the DHCPv4 477 transaction happened. This maintains existing host behavior. 479 3.4.3. Connection Sharing by the Host 481 The situation when a host shares connectivity from an upstream 482 interface (e.g., cellular) to a downstream interface (e.g., Wi-Fi) is 483 known as 'tethering'. Techniques such as ND-proxy [RFC4389], 64share 484 [RFC7278] or prefix delegation (e.g., using DHCPv6-PD [RFC8415]) may 485 be used for that purpose. 487 Whenever the RAs received from the upstream interface contain a PVD 488 RA option, hosts that are sharing connectivity SHOULD include a PVD 489 option within the RAs sent downstream with: 491 o The same PVD-ID FQDN 493 o The same H-flag, Delay and Sequence Number values 494 o The L bit set whenever the host is sharing IPv4 connectivity 495 received from the same upstream interface 497 o The bits from the Reserved field set to 0 499 The values of the R-flag, Router Advertisement message header and 500 Options field depend on whether the connectivity should be shared 501 only with PvD-aware hosts or not (see Section 3.2). In particular, 502 all options received within the upstream PvD Option and included in 503 the downstream RA SHOULD be included in the downstream PvD Option. 505 3.4.4. Usage of DNS Servers 507 PvD-aware hosts can be provisioned with recursive DNS servers via RA 508 options passed within an Explicit PvD, via RA options associated with 509 an Implicit PvD, via DHCPv6 or DHCPv4, or from some other 510 provisioning mechanism that creates an Explicit PvD (such as a VPN). 511 In all of these cases, the recursive DNS server addresses SHOULD be 512 associated with the corresponding PvD. Specifically, queries sent to 513 a configured recursive DNS server SHOULD be sent from a local IP 514 address that was provisioned for the PvD via RA or DHCP. Answers 515 received from the DNS server SHOULD only be used on the same PvD. 517 PvD-aware applications will be able to select which PvD(s) to use for 518 DNS resolution and connections, which allows them to effectively use 519 multiple Explicit PvDs. In order to support non-PvD-aware 520 applications, however, PvD-aware hosts SHOULD ensure that non-PvD- 521 aware name resolution APIs like "getaddrinfo" only use resolvers from 522 a single PvD for a given query. Handling DNS across PvDs is 523 discussed in Section 5.2.1 of [RFC7556], and PvD APIs are discussed 524 in Section 6 of [RFC7556]. 526 Maintaining the correct usage of DNS within PvDs avoids various 527 practical errors, such as: 529 o A PvD associated with a VPN or otherwise private network may 530 provide DNS answers that contain addresses inaccessible over 531 another PvD. This includes the DNS queries to retrieve PvD 532 additional information, which could otherwise send identifying 533 information to the recursive DNS system (see Section 4.1). 535 o A PvD that uses a NAT64 [RFC6146] and DNS64 [RFC6147] will 536 synthesize IPv6 addresses in DNS answers that are not globally 537 routable, and would be invalid on other PvDs. Conversely, an IPv4 538 address resolved via DNS on another PvD cannot be directly used on 539 a NAT64 network. 541 4. Provisioning Domain Additional Information 543 Additional information about the network characteristics can be 544 retrieved based on the PvD ID. This set of information is called PvD 545 Additional Information, and is encoded as a JSON object [RFC8259]. 546 This JSON object is restricted to the I-JSON profile, as defined in 547 [RFC7493]. 549 The purpose of this JSON object is to provide additional information 550 to applications on a client host about the connectivity that is 551 provided using a given interface and source address. It typically 552 includes data that would be considered too large, or not critical 553 enough, to be provided within an RA option. The information 554 contained in this object MAY be used by the operating system, network 555 libraries, applications, or users, in order to decide which set of 556 PvDs should be used for which connection, as described in 557 Section 3.4. 559 The additional information related to a PvD is specifically intended 560 to be optional, and is targeted at optimizing or informing the 561 behavior of user-facing hosts. This information can be extended to 562 provide hints for host system behavior (such as captive portal or 563 walled-garden PvD detection) or application behavior (describing 564 application-specific services offered on a given PvD). This content 565 may not be appropriate for light-weight Internet of Things (IoT) 566 devices. IoT devices might need only a subset of the information, 567 and would in some cases prefer a smaller representation like CBOR 568 ([RFC7049]). Delivering a reduced version of the PvD Additional 569 Information designed for such devices is not defined in this 570 document. 572 4.1. Retrieving the PvD Additional Information 574 When the H-flag of the PvD Option is set, hosts MAY attempt to 575 retrieve the PvD Additional Information associated with a given PvD 576 by performing an HTTP over TLS [RFC2818] GET query to https:///.well-known/pvd. Inversely, hosts MUST NOT do so whenever the 578 H-flag is not set. 580 Recommendations for how to use TLS securely can be found in 581 [RFC7525]. 583 When a host retrieves the PvD Additional Information, it MUST verify 584 that the TLS server certificate is valid for the performed request; 585 specifically, that a DNS-ID [RFC6125] on the certificate is equal to 586 the PvD ID expressed as an FQDN. This validation indicates that the 587 owner of the FQDN authorizes its use with the prefix advertised by 588 the router. If this validation fails, hosts MUST close the 589 connection and treat the PvD as if it has no Additional Information. 591 HTTP requests and responses for PvD additional information use the 592 "application/pvd+json" media type (see Section 8). Clients SHOULD 593 include this media type as an Accept header field in their GET 594 requests, and servers MUST mark this media type as their Content-Type 595 header field in responses. 597 Note that the DNS name resolution of the PvD ID, any connections made 598 for certficate validation (such as OCSP [RFC6960]), and the HTTP 599 request itself MUST be performed using the considered PvD. In other 600 words, the name resolution, PKI checks, source address selection, as 601 well as the next-hop router selection MUST be performed while using 602 exclusively the set of configuration information attached with the 603 PvD, as defined in Section 3.4. In some cases, it may therefore be 604 necessary to wait for an address to be available for use (e.g., once 605 the Duplicate Address Detection or DHCPv6 processes are complete) 606 before initiating the HTTP over TLS query. In order to address 607 privacy concerns around linkability of the PvD HTTP connection with 608 future user-initiated connections, if the host has a temporary 609 address per [RFC4941] in this PvD, then it SHOULD use a temporary 610 address to fetch the PvD Additional Information and MAY deprecate the 611 used temporary address and generate a new temporary address 612 afterward. 614 If the HTTP status of the answer is greater than or equal to 400 the 615 host MUST close its connection and consider that there is no 616 additional PvD information. If the HTTP status of the answer is 617 between 300 and 399, inclusive, it MUST follow the redirection(s). 618 If the HTTP status of the answer is between 200 and 299, inclusive, 619 the response is expected to be a single JSON object. 621 After retrieval of the PvD Additional Information, hosts MUST 622 remember the last Sequence Number value received in an RA including 623 the same PvD ID. Whenever a new RA for the same PvD is received with 624 a different Sequence Number value, or whenever the expiry date for 625 the additional information is reached, hosts MUST deprecate the 626 additional information and stop using it. 628 Hosts retrieving a new PvD Additional Information object MUST check 629 for the presence and validity of the mandatory fields specified in 630 Section 4.3. A retrieved object including an expiration time that is 631 already past or missing a mandatory element MUST be ignored. 633 In order to avoid synchronized queries toward the server hosting the 634 PvD Additional Information when an object expires, object updates are 635 delayed by a randomized backoff time. 637 o When a host performs a JSON object update after it detected a 638 change in the PvD Option Sequence Number, it MUST add a delay 639 before sending the query. The target time for the delay is 640 calculated as a random time between zero and 2**(10 + Delay) 641 milliseconds, where 'Delay' corresponds to the 4-bit unsigned 642 integer in the last received PvD Option. 644 o When a host last retrieved a JSON object at time A that includes a 645 expiry time B using the "expires" key, and the host is configured 646 to keep the PvD information up to date, it MUST add some 647 randomness into its calculation of the time to fetch the update. 648 The target time for fetching the updated object is calculated as a 649 uniformly random time in the interval [(B-A)/2,B]. 651 In the example Figure 2, the delay field value is 1, this means that 652 the host calculates its delay by choosing a uniformly random time 653 between 0 and 2**(10 + 1) milliseconds, i.e., between 0 and 2048 654 milliseconds. 656 Since the 'Delay' value is directly within the PvD Option rather than 657 the object itself, an operator may perform a push-based update by 658 incrementing the Sequence Number value while changing the Delay value 659 depending on the criticality of the update and its PvD Additional 660 Information servers capacity. 662 In addition to adding a random delay when fetching Additional 663 Information, hosts MUST enforce a minimum time between requesting 664 Additional Information for a given PvD on the same network. This 665 minimum time is RECOMMENDED to be 10 seconds, in order to avoid hosts 666 causing a denial-of-service on the PvD server. Hosts also MUST limit 667 the number of requests that are made to different PvD Additional 668 Information servers on the same network within a short period of 669 time. A RECOMMENDED value is to issue no more than five PvD 670 Additional Information requests in total on a given network within 10 671 seconds. For more discussion, see Section 6. 673 The PvD Additional Information object includes a set of IPv6 prefixes 674 (under the key "prefixes") which MUST be checked against all the 675 Prefix Information Options advertised in the RA. If any of the 676 prefixes included in any associated PIO is not covered by at least 677 one of the listed prefixes, the associated PvD information MUST be 678 considered to be a misconfiguration, and MUST NOT be used by the 679 host. See Section 4.4 for more discussion on handling such 680 misconfigurations. 682 If the request for PvD Additional Information fails due to a TLS 683 certificate validation error, an HTTP error, or because the retrieved 684 file does not contain valid PvD JSON, hosts MUST close any connection 685 used to fetch the PvD Additional Information, and MUST NOT request 686 the information for that PvD ID again for the duration of the local 687 network attachment. If a host detects 10 or more such failures to 688 fetch PvD Additional Information, the local network is assumed to be 689 misconfigured or under attack, and the host MUST NOT make any further 690 requests for any PvD Additional Information, belonging to any PvD ID, 691 for the duration of the local network attachment. For more 692 discussion, see Section 6. 694 4.2. Operational Consideration to Providing the PvD Additional 695 Information 697 Whenever the H-flag is set in the PvD Option, a valid PvD Additional 698 Information object MUST be made available to all hosts receiving the 699 RA by the network operator. In particular, when a captive portal is 700 present, hosts MUST still be allowed to perform DNS, certficate 701 validation, and HTTP over TLS operations related to the retrieval of 702 the object, even before logging into the captive portal. 704 Routers SHOULD increment the PVD Option Sequence Number by one 705 whenever a new PvD Additional Information object is available and 706 should be retrieved by hosts. If the value exceeds what can be 707 stored in the Sequence Number field, it MUST wrap back to zero. 709 The server providing the JSON files SHOULD also check whether the 710 client address is contained by the prefixes listed in the additional 711 information, and SHOULD return a 403 response code if there is no 712 match. 714 4.3. PvD Additional Information Format 716 The PvD Additional Information is a JSON object. 718 The following table presents the mandatory keys which MUST be 719 included in the object: 721 +------------+-----------------+-----------+------------------------+ 722 | JSON key | Description | Type | Example | 723 +------------+-----------------+-----------+------------------------+ 724 | identifier | PvD ID FQDN | String | "pvd.example.com." | 725 | | | | | 726 | expires | Date after | [RFC3339] | "2020-05-23T06:00:00Z" | 727 | | which this | Date | | 728 | | object is no | | | 729 | | longer valid | | | 730 | | | | | 731 | prefixes | Array of IPv6 | Array of | ["2001:db8:1::/48", | 732 | | prefixes valid | strings | "2001:db8:4::/48"] | 733 | | for this PvD | | | 734 +------------+-----------------+-----------+------------------------+ 736 A retrieved object which does not include all three of these keys at 737 the root of the JSON object MUST be ignored. All three keys need to 738 be validated, otherwise the object MUST be ignored. The value stored 739 for "identifier" MUST be matched against the PvD ID FQDN presented in 740 the PvD RA option using the comparison mechanism described in 741 Section 3.4. The value stored for "expires" MUST be a valid date in 742 the future. If the PIO of the received RA is not covered by at least 743 one of the "prefixes" key, the retrieved object SHOULD be ignored. 745 The following table presents some optional keys which MAY be included 746 in the object. 748 +------------+-----------------------+---------+--------------------+ 749 | JSON key | Description | Type | Example | 750 +------------+-----------------------+---------+--------------------+ 751 | dnsZones | DNS zones searchable | Array | ["example.com", | 752 | | and accessible | of | "sub.example.com"] | 753 | | | strings | | 754 | | | | | 755 | noInternet | No Internet, set to | Boolean | true | 756 | | "true" when the PvD | | | 757 | | is restricted. | | | 758 +------------+-----------------------+---------+--------------------+ 760 It is worth noting that the JSON format allows for extensions. 761 Whenever an unknown key is encountered, it MUST be ignored along with 762 its associated elements. 764 Private-use or experimental keys MAY be used in the JSON dictionary. 765 In order to avoid such keys colliding with IANA registry keys, 766 implementers or vendors defining private-use or experimental keys 767 MUST create sub-dictionaries. If a set of PvD Additional Information 768 keys are defined by an organization that has a Formal URN Namespace 769 [URN], the URN namespace SHOULD be used as the top-level JSON key for 770 the sub-dictionary. For other private uses, the sub-dictionary key 771 SHOULD follow the format of "vendor-*", where the "*" is replaced by 772 the implementer's or vendor's identifier. For example, keys specific 773 to the FooBar organization could use "vendor-foobar". If a host 774 receives a sub-dictionary with an unknown key, the host MUST ignore 775 the contents of the sub-dictionary. 777 4.3.1. Example 779 The following two examples show how the JSON keys defined in this 780 document can be used: 782 { 783 "identifier": "cafe.example.com.", 784 "expires": "2020-05-23T06:00:00Z", 785 "prefixes": ["2001:db8:1::/48", "2001:db8:4::/48"], 786 } 788 { 789 "identifier": "company.foo.example.com.", 790 "expires": "2020-05-23T06:00:00Z", 791 "prefixes": ["2001:db8:1::/48", "2001:db8:4::/48"], 792 "vendor-foo": 793 { 794 "private-key": "private-value", 795 }, 796 } 798 4.4. Detecting misconfiguration and misuse 800 Hosts MUST validate the TLS server certificate when retrieving PvD 801 Additional Information, as detailed in Section 4.1. 803 Hosts MUST verify that all prefixes in all the RA PIOs are covered by 804 a prefix from the PvD Additional Information. An adversarial router 805 attempting to spoof the definition of an Explicit PvD, without the 806 ability to modify the PvD Additional Information, would need to 807 perform NAT66 in order to circumvent this check. Thus, this check 808 cannot prevent all spoofing, but it can detect misconfiguration or 809 mismatched routers that are not adding a NAT. 811 If NAT66 is being added in order to spoof PvD ownership, the HTTPS 812 server for additional information can detect this misconfiguration. 813 The HTTPS server SHOULD validate the source addresses of incoming 814 connections (see Section 4.1). This check gives reasonable assurance 815 that neither NPTv6 [RFC6296] nor NAT66 were used and restricts the 816 information to the valid network users. If the PvD does not 817 provision IPv4 (it does not include the 'L' bit in the RA), the 818 server cannot validate the source addresses of connections using 819 IPv4. Thus, the PvD ID FQDN for such PvDs SHOULD NOT have a DNS A 820 record. 822 5. Operational Considerations 824 This section describes some example use cases of PvDs. For the sake 825 of simplicity, the RA messages will not be described in the usual 826 ASCII art but rather in an indented list. Values in the PvD Option 827 header that are not included in the example are assumed to be zero or 828 false (such as the H-flag, Sequence Number, and Delay fields). 830 5.1. Exposing Extra RA Options to PvD-Aware Hosts 832 In this example, there is one RA message sent by the router. This 833 message contains some options applicable to all hosts on the network, 834 and also a PvD Option that also contains other options only visible 835 to PvD-aware hosts. 837 o RA Header: router lifetime = 6000 839 o Prefix Information Option: length = 4, prefix = 2001:db8:cafe::/64 841 o PvD Option header: length = 3 + 5 + 4, PvD ID FQDN = example.org., 842 R-flag = 0 (actual length of the header with padding 24 bytes = 3 843 * 8 bytes) 845 * Recursive DNS Server: length = 5, addresses = 846 [2001:db8:cafe::53, 2001:db8:f00d::53] 848 * Prefix Information Option: length = 4, prefix = 849 2001:db8:f00d::/64 851 Note that a PvD-aware host will receive two different prefixes, 852 2001:db8:cafe::/64 and 2001:db8:f00d::/64, both associated with the 853 same PvD (identified by "example.org."). A non-PvD-aware host will 854 only receive one prefix, 2001:db8:cafe::/64. 856 5.2. Different RAs for PvD-Aware and Non-PvD-Aware Hosts 858 It is expected that for some years, networks will have a mixed 859 environment of PvD-aware hosts and non-PvD-aware hosts. If there is 860 a need to give specific information to PvD-aware hosts only, then it 861 is RECOMMENDED to send two RA messages, one for each class of hosts. 862 This approach allows for two distinct sets of configuration 863 information to be sent in a way that will not disrupt non-PvD-aware 864 hosts. It also lowers the risk that a single RA message will 865 approach its MTU limit due to duplicated information. 867 If two RA messages are sent for this reason, they MUST be sent from 868 two different link-local source addresses (Section 3.2). For 869 example, here is the RA sent for non-PvD-aware hosts: 871 o RA Header: router lifetime = 6000 (non-PvD-aware hosts will use 872 this router as a default router) 874 o Prefix Information Option: length = 4, prefix = 2001:db8:cafe::/64 876 o Recursive DNS Server Option: length = 3, addresses= 877 [2001:db8:cafe::53] 879 o PvD Option header: length = 3 + 2, PvD ID FQDN = foo.example.org., 880 R-flag = 1 (actual length of the header 24 bytes = 3 * 8 bytes) 882 * RA Header: router lifetime = 0 (PvD-aware hosts will not use 883 this router as a default router), implicit length = 2 885 And here is the RA sent for PvD-aware hosts: 887 o RA Header: router lifetime = 0 (non-PvD-aware hosts will not use 888 this router as a default router) 890 o PvD Option header: length = 3 + 2 + 4 + 3, PvD ID FQDN = 891 bar.example.org., R-flag = 1 (actual length of the header 24 bytes 892 = 3 * 8 bytes) 894 * RA Header: router lifetime = 1600 (PvD-aware hosts will use 895 this router as a default router), implicit length = 2 897 * Prefix Information Option: length = 4, prefix = 898 2001:db8:f00d::/64 900 * Recursive DNS Server Option: length = 3, addresses = 901 [2001:db8:f00d::53] 903 In the above example, non-PvD-aware hosts will only use the first 904 listed RA sent by their default router and using the 905 2001:db8:cafe::/64 prefix. PvD-aware hosts will autonomously 906 configure addresses from both PIOs, but will only use the source 907 address in 2001:db8:f00d::/64 to communicate past the first hop 908 router since only the router sending the second RA will be used as 909 default router; similarly, they will use the DNS server 910 2001:db8:f00d::53 when communicating from this address. 912 5.3. Enabling Multi-homing for PvD-Aware Hosts 914 In this example, the goal is to have one prefix from one RA be usable 915 by both non-PvD-aware and PvD-aware hosts; and to have another prefix 916 usable only by PvD-aware hosts. This allows PvD-aware hosts to be 917 able to effectively multi-home on the network. 919 The first RA is usable by all hosts. The only difference for PvD- 920 aware hosts is that they can explicitly identify the PvD ID 921 associated with the RA. PvD-aware hosts will also use this prefix to 922 communicate with non-PvD-aware hosts on the same network. 924 o RA Header: router lifetime = 6000 (non-PvD-aware hosts will use 925 this router as a default router) 927 o Prefix Information Option: length = 4, prefix = 2001:db8:cafe::/64 929 o Recursive DNS Server Option: length = 3, addresses= 930 [2001:db8:cafe::53] 932 o PvD Option header: length = 3, PvD ID FQDN = foo.example.org., 933 R-flag = 0 (actual length of the header 24 bytes = 3 * 8 bytes) 935 The second RA contains a prefix usable only by PvD-aware hosts. Non- 936 PvD-aware hosts will ignore this RA; hence, the only PvD-aware hosts 937 will be multi-homed. 939 o RA Header: router lifetime = 0 (non-PvD-aware hosts will not use 940 this router as a default router) 942 o PvD Option header: length = 3 + 2 + 4 + 3, PvD ID FQDN = 943 bar.example.org., R-flag = 1 (actual length of the header 24 bytes 944 = 3 * 8 bytes) 946 * RA Header: router lifetime = 1600 (PvD-aware hosts will use 947 this router as a default router), implicit length = 2 949 * Prefix Information Option: length = 4, prefix = 950 2001:db8:f00d::/64 952 * Recursive DNS Server Option: length = 3, addresses = 953 [2001:db8:f00d::53] 955 Note: the above examples assume that the router has received its PvD 956 IDs from upstream routers or via some other configuration mechanism. 957 Another document could define ways for the router to generate its own 958 PvD IDs to allow the above scenario in the absence of PvD ID 959 provisioning. 961 5.4. Providing Additional Information to PvD-Aware Hosts 963 In this example, the router indicates that it provides additional 964 information using the H-flag. The Sequence Number on the PvD Option 965 is set to 7 in this example. 967 o RA Header: router lifetime = 6000 969 o Prefix Information Option: length = 4, prefix = 2001:db8:cafe::/64 971 o Recursive DNS Server Option: length = 3, addresses= 972 [2001:db8:cafe::53] 974 o PvD Option header: length = 3, PvD ID FQDN = cafe.example.com., 975 Sequence Number = 7, R-flag = 0, H-flag = 1 (actual length of the 976 header with padding 24 bytes = 3 * 8 bytes) 978 A PvD-aware host will fetch https://cafe.example.com/.well-known/pvd 979 to get the additonal information. The following example shows a GET 980 request that the host sends, in HTTP/2 syntax [RFC7540]: 982 :method = GET 983 :scheme = https 984 :authority = cafe.example.com 985 :path = /.well-known/pvd 986 accept = application/pvd+json 988 The HTTP server will respond with the JSON additional information: 990 :status = 200 991 content-type = application/pvd+json 992 content-length = 116 994 { 995 "identifier": "cafe.example.com.", 996 "expires": "2020-05-23T06:00:00Z", 997 "prefixes": ["2001:db8:cafe::/48"], 998 } 1000 At this point, the host has the additional information, and knows the 1001 expiry time. When either the expiry time passes, or a new Sequence 1002 Number is provided in an RA, the host will re-fetch the additional 1003 information. 1005 For example, if the router sends a new RA with the Sequence Number 1006 set to 8, the host will re-fetch the additional information: 1008 o PvD Option header: length = 3 + 5 + 4 , PvD ID FQDN = 1009 cafe.example.com., Sequence Number = 8, R-flag = 0, H-flag = 1 1010 (actual length of the header with padding 24 bytes = 3 * 8 bytes) 1012 However, if the router sends a new RA, but the Sequence Number has 1013 not changed, the host would not re-fetch the additional information 1014 (until and unless the expiry time of the additional information has 1015 passed). 1017 6. Security Considerations 1019 Since the PvD ID RA option can contain an RA header and other RA 1020 options, any security considerations that apply for specific RA 1021 options continue to apply when used within a PvD ID option. 1023 Although some solutions such as IPsec or SeND [RFC3971] can be used 1024 in order to secure the IPv6 Neighbor Discovery Protocol, in practice 1025 actual deployments largely rely on link layer or physical layer 1026 security mechanisms (e.g., 802.1x [IEEE8021X]) in conjunction with RA 1027 Guard [RFC6105]. 1029 If multiple RAs are sent for a single PvD to avoid fragmentation, 1030 dropping packets can lead to processing only part of a PvD ID option, 1031 which could lead to hosts receiving only part of the contained 1032 options. As discussed in Section 3.2, routers MUST include the PvD 1033 ID option in all fragments generated. 1035 This specification does not improve the Neighbor Discovery Protocol 1036 security model, but simply validates that the owner of the PvD FQDN 1037 authorizes its use with the prefix advertised by the router. In 1038 combination with implicit trust in the local router (if present), 1039 this gives the host some level of assurance that the PvD is 1040 authorized for use in this environment. However, when the local 1041 router cannot be trusted, no such guarantee is available. 1043 It must be noted that Section 4.4 of this document only provides 1044 reasonable assurance against misconfiguration but does not prevent a 1045 hostile network access provider from advertising incorrect 1046 information that could lead applications or hosts to select a hostile 1047 PvD. However, a host that correctly implements the multiple PvD 1048 architecture ([RFC7556]) using the mechanism described in this 1049 document will be less susceptible to some attacks than a host that 1050 does not by being able to check for the various misconfigurations or 1051 inconsistencies described in this document. 1053 Since expiration times provided in PvD Additional Information use 1054 absolute time, these values can be skewed for hosts without an 1055 accurate time base, or due to clock skew. Such time values MUST NOT 1056 be used for security-sensitive functionality or decisions. 1058 An attacker generating RAs on a local network can use the H-flag and 1059 the PvD ID to cause hosts on the network to make requests for PvD 1060 Additional Information from servers. This can become a denial-of- 1061 service attack, in which an attacker can amplify its attack by 1062 triggering TLS connections to arbitrary servers in response to 1063 sending UDP packets containing RA messages. To mitigate this attack, 1064 hosts MUST: 1066 o limit the rate at which they fetch a particular PvD's Additional 1067 Information; 1069 o limit the rate at which they fetch any PvD Additional Information 1070 on a given local network; 1072 o stop making requests for a PvD ID that does not respond with valid 1073 JSON; 1075 o stop making requests for all PvD IDs once a certain number of 1076 failures is reached on a particular network. 1078 Details are provided in Section 4.1. This attack can be targeted at 1079 generic web servers, in which case the host behavior of stopping 1080 requesting for any server that doesn't behave like a PvD Additional 1081 Information server is critical. Limiting requests for a specific PvD 1082 ID might not be sufficient if the attacker changes the PvD ID values 1083 quickly, so hosts also need to stop requesting if they detect 1084 consistent failure when on a network that is under attack. For cases 1085 in which an attacker is pointing hosts at a valid PvD Additional 1086 Information server (but one that is not actually associated with the 1087 local network), the server SHOULD reject any requests that do not 1088 originate from the expected IPv6 prefix as described in Section 4.2. 1090 7. Privacy Considerations 1092 Retrieval of the PvD Additional Information over HTTPS requires early 1093 communications between the connecting host and a server which may be 1094 located further than the first hop router. Although this server is 1095 likely to be located within the same administrative domain as the 1096 default router, this property can't be ensured. To minimize the 1097 leakage of identity information while retrieving the PvD Additional 1098 Information, hosts SHOULD make use of an IPv6 temporary address and 1099 SHOULD NOT include any privacy-sensitive data, such as a User-Agent 1100 header field or an HTTP cookie. 1102 Hosts might not always fetch PvD Additional Information, depending on 1103 whether or not they expect to use the information. However, if a 1104 host whitelisted only certain PvD IDs for which to fetch Additional 1105 Information, an attacker could send various PvD IDs in RAs to detect 1106 which PvD IDs are whitelisted by the client. To avoid this, hosts 1107 SHOULD either fetch Additional Information for all eligible PvD IDs 1108 on a given local network, or fetch the information for none of them. 1110 From a user privacy perspective, retrieving the PvD Additional 1111 Information is not different from establishing a first connection to 1112 a remote server, or even performing a single DNS lookup. For 1113 example, most operating systems already perform early queries to 1114 static web sites, such as http://captive.example.com/hotspot- 1115 detect.html, in order to detect the presence of a captive portal. 1117 The DNS queries associated with the PvD Additional Information MUST 1118 use the DNS servers indicated by the associated PvD, as described in 1119 Section 4.1. This ensures the name of the PvD Additional Information 1120 server is not unintentionally sent on another network, thus leaking 1121 identifying information about the networks with which the client is 1122 associated. 1124 There may be some cases where hosts, for privacy reasons, should 1125 refrain from accessing servers that are located outside a certain 1126 network boundary. In practice, this could be implemented as a 1127 whitelist of 'trusted' FQDNs and/or IP prefixes that the host is 1128 allowed to communicate with. In such scenarios, the host SHOULD 1129 check that the provided PvD ID, as well as the IP address that it 1130 resolves into, are part of the allowed whitelist. 1132 Network operators SHOULD restrict access to PvD Additional 1133 Information to only expose it to hosts that are connected to the 1134 local network, especially if the Additional Information would provide 1135 information about local network configuration to attackers. This can 1136 be implemented by whitelisting access from the addresses and prefixes 1137 that the router provides for the PvD, which will match the prefixes 1138 contained in the PvD Additional Information. This technique is 1139 described in Section 4.2. 1141 8. IANA Considerations 1143 Upon publication of this document, IANA is asked to remove the 1144 'reclaimable' tag off the value 21 for the PvD Option (from the IPv6 1145 Neighbor Discovery Option Formats registry). 1147 8.1. New entry in the Well-Known URIs Registry 1149 IANA is asked to add a new entry in the Well-Known URIs registry 1150 [RFC8615] with the following information: 1152 URI suffix: 'pvd' 1154 Change controller: IETF 1156 Specification document: this document 1158 Status: permanent 1160 Related information: N/A 1162 8.2. Additional Information PvD Keys Registry 1164 IANA is asked to create and maintain a new registry called 1165 "Additional Information PvD Keys", which will reserve JSON keys for 1166 use in PvD additional information. The initial contents of this 1167 registry are given in Section 4.3, including both the table of 1168 mandatory keys and the table of optional keys. 1170 The status of a key as mandatory or optional is intentionally not 1171 denoted in the table to allow for flexibility in future use cases. 1172 Any new assignments of keys will be considered as optional for the 1173 purpose of the mechanism described in this document. 1175 New assignments for Additional Information PvD Keys Registry will be 1176 administered by IANA through Expert Review [RFC8126]. Experts are 1177 requested to ensure that defined keys do not overlap in names or 1178 semantics, and represent non-vendor-specific use cases. Vendor- 1179 specific keys SHOULD use sub-dictionaries, as described in 1180 Section 4.3. 1182 IANA is asked to place this registry in a new page, entitled 1183 "Provisioning Domains (PvDs)". 1185 8.3. PvD Option Flags Registry 1187 IANA is also asked to create and maintain a new registry entitled 1188 "PvD Option Flags" reserving bit positions from 0 to 12 to be used in 1189 the PvD Option bitmask. Bit position 0, 1 and 2 are assigned by this 1190 document (as specified in Figure 1). Future assignments require 1191 Standards Action [RFC8126]. 1193 Since these flags apply to an IPv6 Router Advertisement Option, IANA 1194 is asked to place this registry under the existing "Internet Control 1195 Message Protocol version 6 (ICMPv6) Parameters" page, as well as 1196 providing a link on the new "Provisioning Domains (PvDs)" page. 1198 8.4. PvD JSON Media Type Registration 1200 This document registers the media type for PvD JSON text, 1201 "application/pvd+json". 1203 Type Name: application 1205 Subtype Name: pvd+json 1207 Required parameters: N/A 1209 Optional parameters: N/A 1211 Encoding considerations: Encoding considerations are identical to 1212 those specified for the "application/json" media type. 1214 Security considerations: See Section 6. 1216 Interoperability considerations: This document specifies the format 1217 of conforming messages and the interpretation thereof. 1219 Published specification: This document 1221 Applications that use this media type: This media type is intended to 1222 be used by networks advertising additional Provisioning Domain 1223 information, and clients looking up such information. 1225 Fragment identifier considerations: N/A 1227 Additional information: N/A 1229 Person and email address to contact for further information: See 1230 Authors' Addresses section 1232 Intended usage: COMMON 1234 Restrictions on usage: N/A 1236 Author: IETF 1238 Change controller: IETF 1240 9. Acknowledgments 1242 Many thanks to M. Stenberg and S. Barth for their earlier work: 1243 [I-D.stenberg-mif-mpvd-dns], as well as to Basile Bruneau who was 1244 author of an early version of this document. 1246 Thanks also to Marcus Keane, Mikael Abrahamsson, Ray Bellis, Zhen 1247 Cao, Tim Chown, Lorenzo Colitti, Michael Di Bartolomeo, Ian Farrer, 1248 Phillip Hallam-Baker, Bob Hinden, Tatuya Jinmei, Erik Kline, Ted 1249 Lemon, Paul Hoffman, Dave Thaler, Suresh Krishnan, Gorry Fairhurst, 1250 Jen Lenkova, Veronika McKillop, Mark Townsley and James Woodyatt for 1251 useful and interesting discussions and reviews. 1253 Finally, special thanks to Thierry Danis for his valuable inputs and 1254 implementation efforts, Tom Jones for his integration effort into the 1255 NEAT project and Rigil Salim for his implementation work. 1257 10. References 1259 10.1. Normative References 1261 [RFC1035] Mockapetris, P., "Domain names - implementation and 1262 specification", STD 13, RFC 1035, DOI 10.17487/RFC1035, 1263 November 1987, . 1265 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1266 Requirement Levels", BCP 14, RFC 2119, 1267 DOI 10.17487/RFC2119, March 1997, 1268 . 1270 [RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818, 1271 DOI 10.17487/RFC2818, May 2000, 1272 . 1274 [RFC3339] Klyne, G. and C. Newman, "Date and Time on the Internet: 1275 Timestamps", RFC 3339, DOI 10.17487/RFC3339, July 2002, 1276 . 1278 [RFC4191] Draves, R. and D. Thaler, "Default Router Preferences and 1279 More-Specific Routes", RFC 4191, DOI 10.17487/RFC4191, 1280 November 2005, . 1282 [RFC4343] Eastlake 3rd, D., "Domain Name System (DNS) Case 1283 Insensitivity Clarification", RFC 4343, 1284 DOI 10.17487/RFC4343, January 2006, 1285 . 1287 [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, 1288 "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, 1289 DOI 10.17487/RFC4861, September 2007, 1290 . 1292 [RFC4941] Narten, T., Draves, R., and S. Krishnan, "Privacy 1293 Extensions for Stateless Address Autoconfiguration in 1294 IPv6", RFC 4941, DOI 10.17487/RFC4941, September 2007, 1295 . 1297 [RFC6724] Thaler, D., Ed., Draves, R., Matsumoto, A., and T. Chown, 1298 "Default Address Selection for Internet Protocol Version 6 1299 (IPv6)", RFC 6724, DOI 10.17487/RFC6724, September 2012, 1300 . 1302 [RFC6980] Gont, F., "Security Implications of IPv6 Fragmentation 1303 with IPv6 Neighbor Discovery", RFC 6980, 1304 DOI 10.17487/RFC6980, August 2013, 1305 . 1307 [RFC7493] Bray, T., Ed., "The I-JSON Message Format", RFC 7493, 1308 DOI 10.17487/RFC7493, March 2015, 1309 . 1311 [RFC7525] Sheffer, Y., Holz, R., and P. Saint-Andre, 1312 "Recommendations for Secure Use of Transport Layer 1313 Security (TLS) and Datagram Transport Layer Security 1314 (DTLS)", BCP 195, RFC 7525, DOI 10.17487/RFC7525, May 1315 2015, . 1317 [RFC7556] Anipko, D., Ed., "Multiple Provisioning Domain 1318 Architecture", RFC 7556, DOI 10.17487/RFC7556, June 2015, 1319 . 1321 [RFC8028] Baker, F. and B. Carpenter, "First-Hop Router Selection by 1322 Hosts in a Multi-Prefix Network", RFC 8028, 1323 DOI 10.17487/RFC8028, November 2016, 1324 . 1326 [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for 1327 Writing an IANA Considerations Section in RFCs", BCP 26, 1328 RFC 8126, DOI 10.17487/RFC8126, June 2017, 1329 . 1331 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 1332 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 1333 May 2017, . 1335 [RFC8259] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data 1336 Interchange Format", STD 90, RFC 8259, 1337 DOI 10.17487/RFC8259, December 2017, 1338 . 1340 [RFC8615] Nottingham, M., "Well-Known Uniform Resource Identifiers 1341 (URIs)", RFC 8615, DOI 10.17487/RFC8615, May 2019, 1342 . 1344 10.2. Informative References 1346 [I-D.kline-mif-mpvd-api-reqs] 1347 Kline, E., "Multiple Provisioning Domains API 1348 Requirements", draft-kline-mif-mpvd-api-reqs-00 (work in 1349 progress), November 2015. 1351 [I-D.stenberg-mif-mpvd-dns] 1352 Stenberg, M. and S. Barth, "Multiple Provisioning Domains 1353 using Domain Name System", draft-stenberg-mif-mpvd-dns-00 1354 (work in progress), October 2015. 1356 [IEEE8021X] 1357 IEEE, "IEEE Standards for Local and Metropolitan Area 1358 Networks, Port-based Network Access Control, IEEE Std". 1360 [RFC2131] Droms, R., "Dynamic Host Configuration Protocol", 1361 RFC 2131, DOI 10.17487/RFC2131, March 1997, 1362 . 1364 [RFC3646] Droms, R., Ed., "DNS Configuration options for Dynamic 1365 Host Configuration Protocol for IPv6 (DHCPv6)", RFC 3646, 1366 DOI 10.17487/RFC3646, December 2003, 1367 . 1369 [RFC3971] Arkko, J., Ed., Kempf, J., Zill, B., and P. Nikander, 1370 "SEcure Neighbor Discovery (SEND)", RFC 3971, 1371 DOI 10.17487/RFC3971, March 2005, 1372 . 1374 [RFC4389] Thaler, D., Talwar, M., and C. Patel, "Neighbor Discovery 1375 Proxies (ND Proxy)", RFC 4389, DOI 10.17487/RFC4389, April 1376 2006, . 1378 [RFC6105] Levy-Abegnoli, E., Van de Velde, G., Popoviciu, C., and J. 1379 Mohacsi, "IPv6 Router Advertisement Guard", RFC 6105, 1380 DOI 10.17487/RFC6105, February 2011, 1381 . 1383 [RFC6125] Saint-Andre, P. and J. Hodges, "Representation and 1384 Verification of Domain-Based Application Service Identity 1385 within Internet Public Key Infrastructure Using X.509 1386 (PKIX) Certificates in the Context of Transport Layer 1387 Security (TLS)", RFC 6125, DOI 10.17487/RFC6125, March 1388 2011, . 1390 [RFC6146] Bagnulo, M., Matthews, P., and I. van Beijnum, "Stateful 1391 NAT64: Network Address and Protocol Translation from IPv6 1392 Clients to IPv4 Servers", RFC 6146, DOI 10.17487/RFC6146, 1393 April 2011, . 1395 [RFC6147] Bagnulo, M., Sullivan, A., Matthews, P., and I. van 1396 Beijnum, "DNS64: DNS Extensions for Network Address 1397 Translation from IPv6 Clients to IPv4 Servers", RFC 6147, 1398 DOI 10.17487/RFC6147, April 2011, 1399 . 1401 [RFC6296] Wasserman, M. and F. Baker, "IPv6-to-IPv6 Network Prefix 1402 Translation", RFC 6296, DOI 10.17487/RFC6296, June 2011, 1403 . 1405 [RFC6960] Santesson, S., Myers, M., Ankney, R., Malpani, A., 1406 Galperin, S., and C. Adams, "X.509 Internet Public Key 1407 Infrastructure Online Certificate Status Protocol - OCSP", 1408 RFC 6960, DOI 10.17487/RFC6960, June 2013, 1409 . 1411 [RFC7049] Bormann, C. and P. Hoffman, "Concise Binary Object 1412 Representation (CBOR)", RFC 7049, DOI 10.17487/RFC7049, 1413 October 2013, . 1415 [RFC7278] Byrne, C., Drown, D., and A. Vizdal, "Extending an IPv6 1416 /64 Prefix from a Third Generation Partnership Project 1417 (3GPP) Mobile Interface to a LAN Link", RFC 7278, 1418 DOI 10.17487/RFC7278, June 2014, 1419 . 1421 [RFC7540] Belshe, M., Peon, R., and M. Thomson, Ed., "Hypertext 1422 Transfer Protocol Version 2 (HTTP/2)", RFC 7540, 1423 DOI 10.17487/RFC7540, May 2015, 1424 . 1426 [RFC8106] Jeong, J., Park, S., Beloeil, L., and S. Madanapalli, 1427 "IPv6 Router Advertisement Options for DNS Configuration", 1428 RFC 8106, DOI 10.17487/RFC8106, March 2017, 1429 . 1431 [RFC8415] Mrugalski, T., Siodelski, M., Volz, B., Yourtchenko, A., 1432 Richardson, M., Jiang, S., Lemon, T., and T. Winters, 1433 "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)", 1434 RFC 8415, DOI 10.17487/RFC8415, November 2018, 1435 . 1437 [URN] IANA, "Uniform Resource Names (URN) Namespaces", 1438 . 1441 Authors' Addresses 1443 Pierre Pfister 1444 Cisco 1445 11 Rue Camille Desmoulins 1446 Issy-les-Moulineaux 92130 1447 France 1449 Email: ppfister@cisco.com 1451 Eric Vyncke 1452 Cisco 1453 De Kleetlaan, 6 1454 Diegem 1831 1455 Belgium 1457 Email: evyncke@cisco.com 1459 Tommy Pauly 1460 Apple Inc. 1461 One Apple Park Way 1462 Cupertino, California 95014 1463 United States of America 1465 Email: tpauly@apple.com 1467 David Schinazi 1468 Google LLC 1469 1600 Amphitheatre Parkway 1470 Mountain View, California 94043 1471 United States of America 1473 Email: dschinazi.ietf@gmail.com 1474 Wenqin Shao 1475 Cisco 1476 11 Rue Camille Desmoulins 1477 Issy-les-Moulineaux 92130 1478 France 1480 Email: wenshao@cisco.com