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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group J. Laganier 3 Internet-Draft Luminate Wireless, Inc. 4 Obsoletes: 5205 (if approved) January 31, 2016 5 Intended status: Standards Track 6 Expires: August 3, 2016 8 Host Identity Protocol (HIP) Domain Name System (DNS) Extension 9 draft-ietf-hip-rfc5205-bis-09 11 Abstract 13 This document specifies a new resource record (RR) for the Domain 14 Name System (DNS), and how to use it with the Host Identity Protocol 15 (HIP). This RR allows a HIP node to store in the DNS its Host 16 Identity (HI, the public component of the node public-private key 17 pair), Host Identity Tag (HIT, a truncated hash of its public key), 18 and the Domain Names of its rendezvous servers (RVSs). This document 19 obsoletes RFC5205. 21 Status of This Memo 23 This Internet-Draft is submitted in full conformance with the 24 provisions of BCP 78 and BCP 79. 26 Internet-Drafts are working documents of the Internet Engineering 27 Task Force (IETF). Note that other groups may also distribute 28 working documents as Internet-Drafts. The list of current Internet- 29 Drafts is at http://datatracker.ietf.org/drafts/current/. 31 Internet-Drafts are draft documents valid for a maximum of six months 32 and may be updated, replaced, or obsoleted by other documents at any 33 time. It is inappropriate to use Internet-Drafts as reference 34 material or to cite them other than as "work in progress." 36 This Internet-Draft will expire on August 3, 2016. 38 Copyright Notice 40 Copyright (c) 2016 IETF Trust and the persons identified as the 41 document authors. All rights reserved. 43 This document is subject to BCP 78 and the IETF Trust's Legal 44 Provisions Relating to IETF Documents 45 (http://trustee.ietf.org/license-info) in effect on the date of 46 publication of this document. Please review these documents 47 carefully, as they describe your rights and restrictions with respect 48 to this document. Code Components extracted from this document must 49 include Simplified BSD License text as described in Section 4.e of 50 the Trust Legal Provisions and are provided without warranty as 51 described in the Simplified BSD License. 53 Table of Contents 55 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 56 2. Conventions Used in This Document . . . . . . . . . . . . . . 3 57 3. Usage Scenarios . . . . . . . . . . . . . . . . . . . . . . . 3 58 3.1. Simple Static Single Homed End-Host . . . . . . . . . . . 5 59 3.2. Mobile end-host . . . . . . . . . . . . . . . . . . . . . 6 60 4. Overview of Using the DNS with HIP . . . . . . . . . . . . . 8 61 4.1. Storing HI, HIT, and RVS in the DNS . . . . . . . . . . . 8 62 4.2. Initiating Connections Based on DNS Names . . . . . . . . 8 63 5. HIP RR Storage Format . . . . . . . . . . . . . . . . . . . . 9 64 5.1. HIT Length Format . . . . . . . . . . . . . . . . . . . . 10 65 5.2. PK Algorithm Format . . . . . . . . . . . . . . . . . . . 10 66 5.3. PK Length Format . . . . . . . . . . . . . . . . . . . . 10 67 5.4. HIT Format . . . . . . . . . . . . . . . . . . . . . . . 10 68 5.5. Public Key Format . . . . . . . . . . . . . . . . . . . . 10 69 5.6. Rendezvous Servers Format . . . . . . . . . . . . . . . . 10 70 6. HIP RR Presentation Format . . . . . . . . . . . . . . . . . 11 71 7. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 12 72 8. Security Considerations . . . . . . . . . . . . . . . . . . . 12 73 8.1. Attacker Tampering with an Insecure HIP RR . . . . . . . 13 74 8.2. Hash and HITs Collisions . . . . . . . . . . . . . . . . 13 75 8.3. DNSSEC . . . . . . . . . . . . . . . . . . . . . . . . . 14 76 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14 77 10. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 14 78 11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 14 79 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 14 80 12.1. Normative references . . . . . . . . . . . . . . . . . . 14 81 12.2. Informative references . . . . . . . . . . . . . . . . . 16 82 Appendix A. Changes from RFC 5205 . . . . . . . . . . . . . . . 17 83 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 17 85 1. Introduction 87 This document specifies a new resource record (RR) for the Domain 88 Name System (DNS) [RFC1034], and how to use it with the Host Identity 89 Protocol (HIP) [RFC7401]. This RR allows a HIP node to store in the 90 DNS its Host Identity (HI, the public component of the node public- 91 private key pair), Host Identity Tag (HIT, a truncated hash of its 92 HI), and the Domain Names of its rendezvous servers (RVSs) 93 [I-D.ietf-hip-rfc5204-bis]. 95 Currently, most of the Internet applications that need to communicate 96 with a remote host first translate a domain name (often obtained via 97 user input) into one or more IP addresses. This step occurs prior to 98 communication with the remote host, and relies on a DNS lookup. 100 With HIP, IP addresses are intended to be used mostly for on-the-wire 101 communication between end hosts, while most Upper Layer Protocols 102 (ULP) and applications use HIs or HITs instead (ICMP might be an 103 example of an ULP not using them). Consequently, we need a means to 104 translate a domain name into an HI. Using the DNS for this 105 translation is pretty straightforward: We define a new HIP resource 106 record. Upon query by an application or ULP for a name to IP address 107 lookup, the resolver would then additionally perform a name to HI 108 lookup, and use it to construct the resulting HI to IP address 109 mapping (which is internal to the HIP layer). The HIP layer uses the 110 HI to IP address mapping to translate HIs and HITs into IP addresses 111 and vice versa. 113 The HIP specification [RFC7401] specifies the HIP base exchange 114 between a HIP Initiator and a HIP Responder based on a four-way 115 handshake involving a total of four HIP packets (I1, R1, I2, and R2). 116 Since the HIP packets contain both the Initiator and the Responder 117 HIT, the initiator needs to have knowledge of the Responder's HI and 118 HIT prior to initiating the base exchange by sending an I1 packet.. 120 The HIP Rendezvous Extension [I-D.ietf-hip-rfc5204-bis] allows a HIP 121 node to be reached via the IP address(es) of a third party, the 122 node's rendezvous server (RVS). An Initiator willing to establish a 123 HIP association with a Responder served by an RVS would typically 124 initiate a HIP base exchange by sending the I1 packet initiating the 125 exchange towards the RVS IP address rather than towards the Responder 126 IP address. Consequently, we need a means to find the name of a 127 rendezvous server for a given host name. 129 This document introduces the new HIP DNS resource record to store the 130 Rendezvous Server (RVS), Host Identity (HI), and Host Identity Tag 131 (HIT) information. 133 2. Conventions Used in This Document 135 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 136 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 137 document are to be interpreted as described in RFC 2119 [RFC2119]. 139 3. Usage Scenarios 141 In this section, we briefly introduce a number of usage scenarios 142 where the DNS is useful with the Host Identity Protocol. 144 With HIP, most applications and ULPs are unaware of the IP addresses 145 used to carry packets on the wire. Consequently, a HIP node could 146 take advantage of having multiple IP addresses for fail-over, 147 redundancy, mobility, or renumbering, in a manner that is transparent 148 to most ULPs and applications (because they are bound to HIs; hence, 149 they are agnostic to these IP address changes). 151 In these situations, for a node to be reachable by reference to its 152 Fully Qualified Domain Name (FQDN), the following information should 153 be stored in the DNS: 155 o A set of IP address(es) via A [RFC1035] and AAAA [RFC3596] RR sets 156 (RRSets [RFC2181]). 158 o A Host Identity (HI), Host Identity Tag (HIT), and possibly a set 159 of rendezvous servers (RVS) through HIP RRs. 161 The HIP RR is class independent. 163 When a HIP node wants to initiate communication with another HIP 164 node, it first needs to perform a HIP base exchange to set up a HIP 165 association towards its peer. Although such an exchange can be 166 initiated opportunistically, i.e., without prior knowledge of the 167 Responder's HI, by doing so both nodes knowingly risk man-in-the- 168 middle attacks on the HIP exchange. To prevent these attacks, it is 169 recommended that the Initiator first obtains the HI of the Responder, 170 and then initiates the exchange. This can be done, for example, 171 through manual configuration or DNS lookups. Hence, a new HIP RR is 172 introduced. 174 When a HIP node is frequently changing its IP address(es), the 175 natural DNS latency for propagating changes may prevent it from 176 publishing its new IP address(es) in the DNS. For solving this 177 problem, the HIP Architecture [RFC4423] introduces rendezvous servers 178 (RVSs) [I-D.ietf-hip-rfc5204-bis]. A HIP host uses a rendezvous 179 server as a rendezvous point to maintain reachability with possible 180 HIP Initiators while moving [RFC5206]. Such a HIP node would publish 181 in the DNS its RVS domain name(s) in a HIP RR, while keeping its RVS 182 up-to-date with its current set of IP addresses. 184 When a HIP node wants to initiate a HIP exchange with a Responder, it 185 will perform a number of DNS lookups. Depending on the type of 186 implementation, the order in which those lookups will be issued may 187 vary. For instance, implementations using HIT in Application 188 Programming Interfaces (APIs) may typically first query for HIP 189 resource records at the Responder FQDN, while those using an IP 190 address in APIs may typically first query for A and/or AAAA resource 191 records. 193 In the following, we assume that the Initiator first queries for HIP 194 resource records at the Responder FQDN. 196 If the query for the HIP type was responded to with a DNS answer with 197 RCODE=3 (Name Error), then the Responder's information is not present 198 in the DNS and further queries for the same owner name SHOULD NOT be 199 made. 201 In case the query for the HIP records returned a DNS answer with 202 RCODE=0 (No Error) and an empty answer section, it means that no HIP 203 information is available at the responder name. In such a case, if 204 the Initiator has been configured with a policy to fallback to 205 opportunistic HIP (initiating without knowing the Responder's HI) or 206 plain IP, it would send out more queries for A and AAAA types at the 207 Responder's FQDN. 209 Depending on the combinations of answers, the situations described in 210 Section 3.1 and Section 3.2 can occur. 212 Note that storing HIP RR information in the DNS at an FQDN that is 213 assigned to a non-HIP node might have ill effects on its reachability 214 by HIP nodes. 216 3.1. Simple Static Single Homed End-Host 218 In addition to its IP address(es) (IP-R), a HIP node (R) with a 219 single static network attachment that wishes to be reachable by 220 reference to its FQDN (www.example.com) to act as a Responder would 221 store in the DNS a HIP resource record containing its Host Identity 222 (HI-R) and Host Identity Tag (HIT-R). 224 An Initiator willing to associate with a node would typically issue 225 the following queries: 227 o Query #1: QNAME=www.example.com, QTYPE=HIP 229 (QCLASS=IN is assumed and omitted from the examples) 231 Which returns a DNS packet with RCODE=0 and one or more HIP RRs with 232 the HIT and HI (e.g., HIT-R and HI-R) of the Responder in the answer 233 section, but no RVS. 235 o Query #2: QNAME=www.example.com, QTYPE=A 237 o Query #3: QNAME=www.example.com, QTYPE=AAAA 238 Which would return DNS packets with RCODE=0 and respectively one or 239 more A or AAAA RRs containing IP address(es) of the Responder (e.g., 240 IP-R) in their answer sections. 242 Caption: In the remainder of this document, for the sake of keeping 243 diagrams simple and concise, several DNS queries and answers 244 are represented as one single transaction, while in fact 245 there are several queries and answers flowing back and 246 forth, as described in the textual examples. 248 [HIP? A? ] 249 [www.example.com] +-----+ 250 +-------------------------------->| | 251 | | DNS | 252 | +-------------------------------| | 253 | | [HIP? A? ] +-----+ 254 | | [www.example.com] 255 | | [HIP HIT-R HI-R ] 256 | | [A IP-R ] 257 | v 258 +-----+ +-----+ 259 | |--------------I1------------->| | 260 | I |<-------------R1--------------| R | 261 | |--------------I2------------->| | 262 | |<-------------R2--------------| | 263 +-----+ +-----+ 265 Static Singly Homed Host 267 The Initiator would then send an I1 to the Responder's IP addresses 268 (IP-R). 270 3.2. Mobile end-host 272 A mobile HIP node (R) wishing to be reachable by reference to its 273 FQDN (www.example.com) would store in the DNS, possibly in addition 274 to its IP address(es) (IP-R), its HI (HI-R), HIT (HIT-R), and the 275 domain name(s) of its rendezvous server(s) (e.g., rvs.example.com) in 276 HIP resource record(s). The mobile HIP node also needs to notify its 277 rendezvous servers of any change in its set of IP address(es). 279 An Initiator willing to associate with such a mobile node would 280 typically issue the following queries: 282 o Query #1: QNAME=www.example.com, QTYPE=HIP 283 Which returns a DNS packet with RCODE=0 and one or more HIP RRs with 284 the HIT, HI, and RVS domain name(s) (e.g., HIT-R, HI-R, and 285 rvs.example.com) of the Responder in the answer section. 287 o Query #2: QNAME=rvs.example.com, QTYPE=A 289 o Query #3: QNAME=rvs.example.com, QTYPE=AAAA 291 Which return DNS packets with RCODE=0 and respectively one or more A 292 or AAAA RRs containing IP address(es) of the Responder's RVS (e.g., 293 IP-RVS) in their answer sections. 295 [HIP? ] 296 [www.example.com] 298 [A? ] 299 [rvs.example.com] +-----+ 300 +----------------------------------------->| | 301 | | DNS | 302 | +----------------------------------------| | 303 | | [HIP? ] +-----+ 304 | | [www.example.com ] 305 | | [HIP HIT-R HI-R rvs.example.com] 306 | | 307 | | [A? ] 308 | | [rvs.example.com] 309 | | [A IP-RVS ] 310 | | 311 | | +-----+ 312 | | +------I1----->| RVS |-----I1------+ 313 | | | +-----+ | 314 | | | | 315 | | | | 316 | v | v 317 +-----+ +-----+ 318 | |<---------------R1------------| | 319 | I |----------------I2----------->| R | 320 | |<---------------R2------------| | 321 +-----+ +-----+ 323 Mobile End-Host 325 The Initiator would then send an I1 to the RVS IP address (IP-RVS). 326 Following, the RVS will relay the I1 up to the mobile node's IP 327 address (IP-R), which will complete the HIP exchange. 329 4. Overview of Using the DNS with HIP 331 4.1. Storing HI, HIT, and RVS in the DNS 333 For any HIP node, its Host Identity (HI), the associated Host 334 Identity Tag (HIT), and the FQDN of its possible RVSs can be stored 335 in a DNS HIP RR. Any conforming implementation may store a Host 336 Identity (HI) and its associated Host Identity Tag (HIT) in a DNS HIP 337 RDATA format. HI and HIT are defined in Section 3 of the HIP 338 specification [RFC7401]. 340 Upon return of a HIP RR, a host MUST always calculate the HI- 341 derivative HIT to be used in the HIP exchange, as specified in 342 Section 3 of the HIP specification [RFC7401], while the HIT possibly 343 embedded along SHOULD only be used as an optimization (e.g., table 344 lookup). 346 The HIP resource record may also contain one or more domain name(s) 347 of rendezvous server(s) towards which HIP I1 packets might be sent to 348 trigger the establishment of an association with the entity named by 349 this resource record [I-D.ietf-hip-rfc5204-bis]. 351 The rendezvous server field of the HIP resource record stored at a 352 given owner name MAY include the owner name itself. A semantically 353 equivalent situation occurs if no rendezvous server is present in the 354 HIP resource record stored at that owner name. Such situations occur 355 in two cases: 357 o The host is mobile, and the A and/or AAAA resource record(s) 358 stored at its host name contain the IP address(es) of its 359 rendezvous server rather than its own one. 361 o The host is stationary, and can be reached directly at the IP 362 address(es) contained in the A and/or AAAA resource record(s) 363 stored at its host name. This is a degenerate case of rendezvous 364 service where the host somewhat acts as a rendezvous server for 365 itself. 367 An RVS receiving such an I1 would then relay it to the appropriate 368 Responder (the owner of the I1 receiver HIT). The Responder will 369 then complete the exchange with the Initiator, typically without 370 ongoing help from the RVS. 372 4.2. Initiating Connections Based on DNS Names 374 On a HIP node, a Host Identity Protocol exchange SHOULD be initiated 375 whenever a ULP attempts to communicate with an entity and the DNS 376 lookup returns HIP resource records. 378 The HIP resource records have a Time To Live (TTL) associated with 379 them. When the number of seconds that passed since the record was 380 retrieved exceeds the record's TTL, the record MUST be considered to 381 be no longer valid and deleted by the entity that retrieved it. If 382 access to the record is necessary to initiate communication with the 383 entity to which the record corresponds, a new query MUST be be made 384 to retrieve a fresh copy of the record. 386 There may be multiple HIP RRs associated with a single name. It is 387 outside the scope of this specification as to how a host chooses from 388 between multiple RRs when more than one is returned. The RVS 389 information may be copied and aligned across multiple RRs, or may be 390 different for each one; a host MUST check that the RVS used is 391 associated with the HI being used, when multiple choices are present. 393 5. HIP RR Storage Format 395 The RDATA for a HIP RR consists of a public key algorithm type, the 396 HIT length, a HIT, a public key (i.e., a HI), and optionally one or 397 more rendezvous server(s). 399 0 1 2 3 400 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 1 401 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 402 | HIT length | PK algorithm | PK length | 403 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 404 | | 405 ~ HIT ~ 406 | | 407 + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 408 | | | 409 +-+-+-+-+-+-+-+-+-+-+-+ + 410 | Public Key | 411 ~ ~ 412 | | 413 + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 414 | | | 415 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + 416 | | 417 ~ Rendezvous Servers ~ 418 | | 419 + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 420 | | 421 +-+-+-+-+-+-+-+ 423 The HIT length, PK algorithm, PK length, HIT, and Public Key fields 424 are REQUIRED. The Rendezvous Servers field is OPTIONAL. 426 5.1. HIT Length Format 428 The HIT length indicates the length in bytes of the HIT field. This 429 is an 8-bit unsigned integer. 431 5.2. PK Algorithm Format 433 The PK algorithm field indicates the public key cryptographic 434 algorithm and the implied public key field format. This is an 8-bit 435 unsigned integer. This document reuses the values defined for the 436 'algorithm type' of the IPSECKEY RR [RFC4025]. 438 Presently defined values are listed in Section 9 for reference. 440 5.3. PK Length Format 442 The PK length indicates the length in bytes of the Public key field. 443 This is a 16-bit unsigned integer in network byte order. 445 5.4. HIT Format 447 The HIT is stored as a binary value in network byte order. 449 5.5. Public Key Format 451 Two of the public key types defined in this document (RSA and DSA) 452 reuse the public key formats defined for the IPSECKEY RR [RFC4025]. 454 The DSA key format is defined in RFC 2536 [RFC2536]. 456 The RSA key format is defined in RFC 3110 [RFC3110] and the RSA key 457 size limit (4096 bits) is relaxed in the IPSECKEY RR [RFC4025] 458 specification. 460 In addition, this document similarly defines the public key format of 461 type ECDSA as the algorithm-specific portion of the DNSKEY RR RDATA 462 for ECDSA [RFC6605], i.e, all of the DNSKEY RR DATA after the first 463 four octets, corresponding to the same portion of the DNSKEY RR that 464 must be specified by documents that define a DNSSEC algorithm. 466 5.6. Rendezvous Servers Format 468 The Rendezvous Servers field indicates one or more variable length 469 wire-encoded domain names of rendezvous server(s), as described in 470 Section 3.3 of RFC 1035 [RFC1035]. The wire-encoded format is self- 471 describing, so the length is implicit. The domain names MUST NOT be 472 compressed. The rendezvous server(s) are listed in order of 473 preference (i.e., first rendezvous server(s) are preferred), defining 474 an implicit order amongst rendezvous servers of a single RR. When 475 multiple HIP RRs are present at the same owner name, this implicit 476 order of rendezvous servers within an RR MUST NOT be used to infer a 477 preference order between rendezvous servers stored in different RRs. 479 6. HIP RR Presentation Format 481 This section specifies the representation of the HIP RR in a zone 482 master file. 484 The HIT length field is not represented, as it is implicitly known 485 thanks to the HIT field representation. 487 The PK algorithm field is represented as unsigned integers. 489 The HIT field is represented as the Base16 encoding [RFC4648] (a.k.a. 490 hex or hexadecimal) of the HIT. The encoding MUST NOT contain 491 whitespaces to distinguish it from the public key field. 493 The Public Key field is represented as the Base64 encoding [RFC4648] 494 of the public key. The encoding MUST NOT contain whitespace(s) to 495 distinguish it from the Rendezvous Servers field. 497 The PK length field is not represented, as it is implicitly known 498 thanks to the Public key field representation containing no 499 whitespaces. 501 The Rendezvous Servers field is represented by one or more domain 502 name(s) separated by whitespace(s). 504 The complete representation of the HIP record is: 506 IN HIP ( pk-algorithm 507 base16-encoded-hit 508 base64-encoded-public-key 509 rendezvous-server[1] 510 ... 511 rendezvous-server[n] ) 513 When no RVSs are present, the representation of the HIP record is: 515 IN HIP ( pk-algorithm 516 base16-encoded-hit 517 base64-encoded-public-key ) 519 7. Examples 521 In the examples below, the public key field containing no whitespace 522 is wrapped since it does not fit in a single line of this document. 524 Example of a node with HI and HIT but no RVS: 526 www.example.com. IN HIP ( 2 200100107B1A74DF365639CC39F1D578 527 AwEAAbdxyhNuSutc5EMzxTs9LBPCIkOFH8cI 528 vM4p9+LrV4e19WzK00+CI6zBCQTdtWsuxKbWIy87UOoJTwkUs7lBu+Upr1gsNrut79ry 529 ra+bSRGQb1slImA8YVJyuIDsj7kwzG7jnERNqnWxZ48AWkskmdHaVDP4BcelrTI3rMXd 530 XF5D ) 532 Example of a node with a HI, HIT, and one RVS: 534 www.example.com. IN HIP ( 2 200100107B1A74DF365639CC39F1D578 535 AwEAAbdxyhNuSutc5EMzxTs9LBPCIkOFH8cI 536 vM4p9+LrV4e19WzK00+CI6zBCQTdtWsuxKbWIy87UOoJTwkUs7lBu+Upr1gsNrut79ry 537 ra+bSRGQb1slImA8YVJyuIDsj7kwzG7jnERNqnWxZ48AWkskmdHaVDP4BcelrTI3rMXd 538 XF5D 539 rvs.example.com. ) 541 Example of a node with a HI, HIT, and two RVSs: 543 www.example.com. IN HIP ( 2 200100107B1A74DF365639CC39F1D578 544 AwEAAbdxyhNuSutc5EMzxTs9LBPCIkOFH8cI 545 vM4p9+LrV4e19WzK00+CI6zBCQTdtWsuxKbWIy87UOoJTwkUs7lBu+Upr1gsNrut79ry 546 ra+bSRGQb1slImA8YVJyuIDsj7kwzG7jnERNqnWxZ48AWkskmdHaVDP4BcelrTI3rMXd 547 XF5D 548 rvs1.example.com. 549 rvs2.example.com. ) 551 8. Security Considerations 553 This section contains a description of the known threats involved 554 with the usage of the HIP DNS Extension. 556 In a manner similar to the IPSECKEY RR [RFC4025], the HIP DNS 557 Extension allows for the provision of two HIP nodes with the public 558 keying material (HI) of their peer. These HIs will be subsequently 559 used in a key exchange between the peers. Hence, the HIP DNS 560 Extension is subject, as the IPSECKEY RR, to threats stemming from 561 attacks against unsecured HIP RRs, as described in the remainder of 562 this section. 564 A HIP node SHOULD obtain HIP RRs from a trusted party trough a secure 565 channel ensuring data integrity and authenticity of the RRs. DNSSEC 567 [RFC4033] [RFC4034] [RFC4035] provides such a secure channel. 568 However, it should be emphasized that DNSSEC only offers data 569 integrity and authenticity guarantees to the channel between the DNS 570 server publishing a zone and the HIP node. DNSSEC does not ensure 571 that the entity publishing the zone is trusted. Therefore, the RRSIG 572 signature of the HIP RRSet MUST NOT be misinterpreted as a 573 certificate binding the HI and/or the HIT to the owner name. 575 In the absence of a proper secure channel, both parties are 576 vulnerable to MitM and DoS attacks, and unrelated parties might be 577 subject to DoS attacks as well. These threats are described in the 578 following sections. 580 8.1. Attacker Tampering with an Insecure HIP RR 582 The HIP RR contains public keying material in the form of the named 583 peer's public key (the HI) and its secure hash (the HIT). Both of 584 these are not sensitive to attacks where an adversary gains knowledge 585 of them. However, an attacker that is able to mount an active attack 586 on the DNS, i.e., tampers with this HIP RR (e.g., using DNS 587 spoofing), is able to mount Man-in-the-Middle attacks on the 588 cryptographic core of the eventual HIP exchange (Responder's HIP RR 589 rewritten by the attacker). 591 The HIP RR may contain a rendezvous server domain name resolved into 592 a destination IP address where the named peer is reachable by an I1, 593 as per the HIP Rendezvous Extension [I-D.ietf-hip-rfc5204-bis]. 594 Thus, an attacker able to tamper with this RR is able to redirect I1 595 packets sent to the named peer to a chosen IP address for DoS or MitM 596 attacks. Note that this kind of attack is not specific to HIP and 597 exists independently of whether or not HIP and the HIP RR are used. 598 Such an attacker might tamper with A and AAAA RRs as well. 600 An attacker might obviously use these two attacks in conjunction: It 601 will replace the Responder's HI and RVS IP address by its own in a 602 spoofed DNS packet sent to the Initiator HI, then redirect all 603 exchanged packets to him and mount a MitM on HIP. In this case, HIP 604 won't provide confidentiality nor Initiator HI protection from 605 eavesdroppers. 607 8.2. Hash and HITs Collisions 609 As with many cryptographic algorithms, some secure hashes (e.g., 610 SHA1, used by HIP to generate a HIT from an HI) eventually become 611 insecure, because an exploit has been found in which an attacker with 612 reasonable computation power breaks one of the security features of 613 the hash (e.g., its supposed collision resistance). This is why a 614 HIP end-node implementation SHOULD NOT authenticate its HIP peers 615 based solely on a HIT retrieved from the DNS, but SHOULD rather use 616 HI-based authentication. 618 8.3. DNSSEC 620 In the absence of DNSSEC, the HIP RR is subject to the threats 621 described in RFC 3833 [RFC3833]. 623 9. IANA Considerations 625 IANA is requested to replace references to [RFC5205] by references to 626 this document in the the DNS RR type code registry. 628 IANA is requested to allocate the following algorithm type in the 629 IPSECKEY RR [RFC4025] registry: 631 [IANA-TBD] is ECDSA 633 10. Contributors 635 Pekka Nikander co-authored an earlier, experimental version of this 636 specification [RFC5205]. 638 11. Acknowledgments 640 As usual in the IETF, this document is the result of a collaboration 641 between many people. The authors would like to thank the author 642 (Michael Richardson), contributors, and reviewers of the IPSECKEY RR 643 [RFC4025] specification, after which this document was framed. The 644 authors would also like to thank the following people, who have 645 provided thoughtful and helpful discussions and/or suggestions, that 646 have helped improve this document: Jeff Ahrenholz, Rob Austein, Hannu 647 Flinck, Olafur Gudmundsson, Tom Henderson, Peter Koch, Olaf Kolkman, 648 Miika Komu, Andrew McGregor, Erik Nordmark, and Gabriel Montenegro. 649 Some parts of this document stem from the HIP specification 650 [RFC7401]. Finally, thanks Sheng Jiang for performing the Internet 651 Area Directorate review of this document in the course of the 652 publication process. 654 12. References 656 12.1. Normative references 658 [I-D.ietf-hip-rfc5204-bis] 659 Laganier, J. and L. Eggert, "Host Identity Protocol (HIP) 660 Rendezvous Extension", draft-ietf-hip-rfc5204-bis-07 (work 661 in progress), December 2015. 663 [RFC1034] Mockapetris, P., "Domain names - concepts and facilities", 664 STD 13, RFC 1034, DOI 10.17487/RFC1034, November 1987, 665 . 667 [RFC1035] Mockapetris, P., "Domain names - implementation and 668 specification", STD 13, RFC 1035, DOI 10.17487/RFC1035, 669 November 1987, . 671 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 672 Requirement Levels", BCP 14, RFC 2119, 673 DOI 10.17487/RFC2119, March 1997, 674 . 676 [RFC2181] Elz, R. and R. Bush, "Clarifications to the DNS 677 Specification", RFC 2181, DOI 10.17487/RFC2181, July 1997, 678 . 680 [RFC3596] Thomson, S., Huitema, C., Ksinant, V., and M. Souissi, 681 "DNS Extensions to Support IP Version 6", RFC 3596, 682 DOI 10.17487/RFC3596, October 2003, 683 . 685 [RFC4025] Richardson, M., "A Method for Storing IPsec Keying 686 Material in DNS", RFC 4025, DOI 10.17487/RFC4025, March 687 2005, . 689 [RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S. 690 Rose, "DNS Security Introduction and Requirements", 691 RFC 4033, DOI 10.17487/RFC4033, March 2005, 692 . 694 [RFC4034] Arends, R., Austein, R., Larson, M., Massey, D., and S. 695 Rose, "Resource Records for the DNS Security Extensions", 696 RFC 4034, DOI 10.17487/RFC4034, March 2005, 697 . 699 [RFC4035] Arends, R., Austein, R., Larson, M., Massey, D., and S. 700 Rose, "Protocol Modifications for the DNS Security 701 Extensions", RFC 4035, DOI 10.17487/RFC4035, March 2005, 702 . 704 [RFC4648] Josefsson, S., "The Base16, Base32, and Base64 Data 705 Encodings", RFC 4648, DOI 10.17487/RFC4648, October 2006, 706 . 708 [RFC6605] Hoffman, P. and W. Wijngaards, "Elliptic Curve Digital 709 Signature Algorithm (DSA) for DNSSEC", RFC 6605, 710 DOI 10.17487/RFC6605, April 2012, 711 . 713 [RFC7401] Moskowitz, R., Ed., Heer, T., Jokela, P., and T. 714 Henderson, "Host Identity Protocol Version 2 (HIPv2)", 715 RFC 7401, DOI 10.17487/RFC7401, April 2015, 716 . 718 12.2. Informative references 720 [RFC2536] Eastlake 3rd, D., "DSA KEYs and SIGs in the Domain Name 721 System (DNS)", RFC 2536, DOI 10.17487/RFC2536, March 1999, 722 . 724 [RFC3110] Eastlake 3rd, D., "RSA/SHA-1 SIGs and RSA KEYs in the 725 Domain Name System (DNS)", RFC 3110, DOI 10.17487/RFC3110, 726 May 2001, . 728 [RFC3833] Atkins, D. and R. Austein, "Threat Analysis of the Domain 729 Name System (DNS)", RFC 3833, DOI 10.17487/RFC3833, August 730 2004, . 732 [RFC4423] Moskowitz, R. and P. Nikander, "Host Identity Protocol 733 (HIP) Architecture", RFC 4423, DOI 10.17487/RFC4423, May 734 2006, . 736 [RFC5205] Nikander, P. and J. Laganier, "Host Identity Protocol 737 (HIP) Domain Name System (DNS) Extensions", RFC 5205, 738 DOI 10.17487/RFC5205, April 2008, 739 . 741 [RFC5206] Henderson, T., Ed., "End-Host Mobility and Multihoming 742 with the Host Identity Protocol", RFC 5206, April 2008. 744 Appendix A. Changes from RFC 5205 746 o Updated HIP references to revised HIP specifications. 748 o Extended DNS HIP RR to support for Host Identities based on 749 Elliptic Curve Digital Signature Algorithm (ECDSA). 751 o Clarified that new query must be made when the time that passed 752 since a RR was retrieved exceeds the TTL of the RR. 754 o Added considerations related to multiple HIP RRs being associated 755 with a single name. 757 Author's Address 759 Julien Laganier 760 Luminate Wireless, Inc. 761 Cupertino, CA 762 USA 764 EMail: julien.ietf@gmail.com