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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 Juniper Networks 4 Obsoletes: 5205 (if approved) March 14, 2011 5 Intended status: Standards Track 6 Expires: September 15, 2011 8 Host Identity Protocol (HIP) Domain Name System (DNS) Extension 9 draft-ietf-hip-rfc5205-bis-01 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). 20 Status of This Memo 22 This Internet-Draft is submitted in full conformance with the 23 provisions of BCP 78 and BCP 79. 25 Internet-Drafts are working documents of the Internet Engineering 26 Task Force (IETF). Note that other groups may also distribute 27 working documents as Internet-Drafts. The list of current Internet- 28 Drafts is at http://datatracker.ietf.org/drafts/current/. 30 Internet-Drafts are draft documents valid for a maximum of six months 31 and may be updated, replaced, or obsoleted by other documents at any 32 time. It is inappropriate to use Internet-Drafts as reference 33 material or to cite them other than as "work in progress." 35 This Internet-Draft will expire on September 15, 2011. 37 Copyright Notice 39 Copyright (c) 2011 IETF Trust and the persons identified as the 40 document authors. All rights reserved. 42 This document is subject to BCP 78 and the IETF Trust's Legal 43 Provisions Relating to IETF Documents 44 (http://trustee.ietf.org/license-info) in effect on the date of 45 publication of this document. Please review these documents 46 carefully, as they describe your rights and restrictions with respect 47 to this document. Code Components extracted from this document must 48 include Simplified BSD License text as described in Section 4.e of 49 the Trust Legal Provisions and are provided without warranty as 50 described in the Simplified BSD License. 52 Table of Contents 54 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 55 2. Conventions Used in This Document . . . . . . . . . . . . . . 3 56 3. Usage Scenarios . . . . . . . . . . . . . . . . . . . . . . . 4 57 3.1. Simple Static Singly Homed End-Host . . . . . . . . . . . 5 58 3.2. Mobile end-host . . . . . . . . . . . . . . . . . . . . . 6 59 4. Overview of Using the DNS with HIP . . . . . . . . . . . . . . 8 60 4.1. Storing HI, HIT, and RVS in the DNS . . . . . . . . . . . 8 61 4.2. Initiating Connections Based on DNS Names . . . . . . . . 8 62 5. HIP RR Storage Format . . . . . . . . . . . . . . . . . . . . 9 63 5.1. HIT Length Format . . . . . . . . . . . . . . . . . . . . 9 64 5.2. PK Algorithm Format . . . . . . . . . . . . . . . . . . . 9 65 5.3. PK Length Format . . . . . . . . . . . . . . . . . . . . . 10 66 5.4. HIT Format . . . . . . . . . . . . . . . . . . . . . . . . 10 67 5.5. Public Key Format . . . . . . . . . . . . . . . . . . . . 10 68 5.6. Rendezvous Servers Format . . . . . . . . . . . . . . . . 10 69 6. HIP RR Presentation Format . . . . . . . . . . . . . . . . . . 10 70 7. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 71 8. Security Considerations . . . . . . . . . . . . . . . . . . . 12 72 8.1. Attacker Tampering with an Insecure HIP RR . . . . . . . . 12 73 8.2. Hash and HITs Collisions . . . . . . . . . . . . . . . . . 13 74 8.3. DNSSEC . . . . . . . . . . . . . . . . . . . . . . . . . . 13 75 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13 76 10. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 14 77 11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 14 78 12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 14 79 12.1. Normative references . . . . . . . . . . . . . . . . . . . 14 80 12.2. Informative references . . . . . . . . . . . . . . . . . . 15 81 Appendix A. Changes from RFC 5205 . . . . . . . . . . . . . . . . 16 83 1. Introduction 85 This document specifies a new resource record (RR) for the Domain 86 Name System (DNS) [RFC1034], and how to use it with the Host Identity 87 Protocol (HIP) [I-D.ietf-hip-rfc5201-bis]. This RR allows a HIP node 88 to store in the DNS its Host Identity (HI, the public component of 89 the node public-private key pair), Host Identity Tag (HIT, a 90 truncated hash of its HI), and the Domain Names of its rendezvous 91 servers (RVSs) [I-D.ietf-hip-rfc5204-bis]. 93 Currently, most of the Internet applications that need to communicate 94 with a remote host first translate a domain name (often obtained via 95 user input) into one or more IP address(es). This step occurs prior 96 to communication with the remote host, and relies on a DNS lookup. 98 With HIP, IP addresses are intended to be used mostly for on-the-wire 99 communication between end hosts, while most Upper Layer Protocols 100 (ULP) and applications use HIs or HITs instead (ICMP might be an 101 example of an ULP not using them). Consequently, we need a means to 102 translate a domain name into an HI. Using the DNS for this 103 translation is pretty straightforward: We define a new HIP resource 104 record. Upon query by an application or ULP for a name to IP address 105 lookup, the resolver would then additionally perform a name to HI 106 lookup, and use it to construct the resulting HI to IP address 107 mapping (which is internal to the HIP layer). The HIP layer uses the 108 HI to IP address mapping to translate HIs and HITs into IP addresses 109 and vice versa. 111 The HIP Rendezvous Extension [I-D.ietf-hip-rfc5204-bis] allows a HIP 112 node to be reached via the IP address(es) of a third party, the 113 node's rendezvous server (RVS). An Initiator willing to establish a 114 HIP association with a Responder served by an RVS would typically 115 initiate a HIP exchange by sending an I1 towards the RVS IP address 116 rather than towards the Responder IP address. Consequently, we need 117 a means to find the name of a rendezvous server for a given host 118 name. 120 This document introduces the new HIP DNS resource record to store the 121 Rendezvous Server (RVS), Host Identity (HI), and Host Identity Tag 122 (HIT) information. 124 2. Conventions Used in This Document 126 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 127 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 128 document are to be interpreted as described in RFC 2119 [RFC2119]. 130 3. Usage Scenarios 132 In this section, we briefly introduce a number of usage scenarios 133 where the DNS is useful with the Host Identity Protocol. 135 With HIP, most applications and ULPs are unaware of the IP addresses 136 used to carry packets on the wire. Consequently, a HIP node could 137 take advantage of having multiple IP addresses for fail-over, 138 redundancy, mobility, or renumbering, in a manner that is transparent 139 to most ULPs and applications (because they are bound to HIs; hence, 140 they are agnostic to these IP address changes). 142 In these situations, for a node to be reachable by reference to its 143 Fully Qualified Domain Name (FQDN), the following information should 144 be stored in the DNS: 146 o A set of IP address(es) via A [RFC1035] and AAAA [RFC3596] RR sets 147 (RRSets [RFC2181]). 149 o A Host Identity (HI), Host Identity Tag (HIT), and possibly a set 150 of rendezvous servers (RVS) through HIP RRs. 152 When a HIP node wants to initiate communication with another HIP 153 node, it first needs to perform a HIP base exchange to set up a HIP 154 association towards its peer. Although such an exchange can be 155 initiated opportunistically, i.e., without prior knowledge of the 156 Responder's HI, by doing so both nodes knowingly risk man-in-the- 157 middle attacks on the HIP exchange. To prevent these attacks, it is 158 recommended that the Initiator first obtain the HI of the Responder, 159 and then initiate the exchange. This can be done, for example, 160 through manual configuration or DNS lookups. Hence, a new HIP RR is 161 introduced. 163 When a HIP node is frequently changing its IP address(es), the 164 natural DNS latency for propagating changes may prevent it from 165 publishing its new IP address(es) in the DNS. For solving this 166 problem, the HIP Architecture [RFC4423] introduces rendezvous servers 167 (RVSs) [I-D.ietf-hip-rfc5204-bis]. A HIP host uses a rendezvous 168 server as a rendezvous point to maintain reachability with possible 169 HIP initiators while moving [RFC5206]. Such a HIP node would publish 170 in the DNS its RVS domain name(s) in a HIP RR, while keeping its RVS 171 up-to-date with its current set of IP addresses. 173 When a HIP node wants to initiate a HIP exchange with a Responder, it 174 will perform a number of DNS lookups. Depending on the type of 175 implementation, the order in which those lookups will be issued may 176 vary. For instance, implementations using HIT in APIs may typically 177 first query for HIP resource records at the Responder FQDN, while 178 those using an IP address in APIs may typically first query for A 179 and/or AAAA resource records. 181 In the following, we assume that the Initiator first queries for HIP 182 resource records at the Responder FQDN. 184 If the query for the HIP type was responded to with a DNS answer with 185 RCODE=3 (Name Error), then the Responder's information is not present 186 in the DNS and further queries for the same owner name SHOULD NOT be 187 made. 189 In case the query for the HIP records returned a DNS answer with 190 RCODE=0 (No Error) and an empty answer section, it means that no HIP 191 information is available at the responder name. In such a case, if 192 the Initiator has been configured with a policy to fallback to 193 opportunistic HIP (initiating without knowing the Responder's HI) or 194 plain IP, it would send out more queries for A and AAAA types at the 195 Responder's FQDN. 197 Depending on the combinations of answers, the situations described in 198 Section 3.1 and Section 3.2 can occur. 200 Note that storing HIP RR information in the DNS at an FQDN that is 201 assigned to a non-HIP node might have ill effects on its reachability 202 by HIP nodes. 204 3.1. Simple Static Singly Homed End-Host 206 A HIP node (R) with a single static network attachment, wishing to be 207 reachable by reference to its FQDN (www.example.com), would store in 208 the DNS, in addition to its IP address(es) (IP-R), its Host Identity 209 (HI-R) and Host Identity Tag (HIT-R) in a HIP resource record. 211 An Initiator willing to associate with a node would typically issue 212 the following queries: 214 o QNAME=www.example.com, QTYPE=HIP 216 o (QCLASS=IN is assumed and omitted from the examples) 218 Which returns a DNS packet with RCODE=0 and one or more HIP RRs with 219 the HIT and HI (e.g., HIT-R and HI-R) of the Responder in the answer 220 section, but no RVS. 222 o QNAME=www.example.com, QTYPE=A QNAME=www.example.com, QTYPE=AAAA 224 Which returns DNS packets with RCODE=0 and one or more A or AAAA RRs 225 containing IP address(es) of the Responder (e.g., IP-R) in the answer 226 section. 228 Caption: In the remainder of this document, for the sake of keeping 229 diagrams simple and concise, several DNS queries and answers 230 are represented as one single transaction, while in fact 231 there are several queries and answers flowing back and 232 forth, as described in the textual examples. 234 [HIP? A? ] 235 [www.example.com] +-----+ 236 +-------------------------------->| | 237 | | DNS | 238 | +-------------------------------| | 239 | | [HIP? A? ] +-----+ 240 | | [www.example.com] 241 | | [HIP HIT-R HI-R ] 242 | | [A IP-R ] 243 | v 244 +-----+ +-----+ 245 | |--------------I1------------->| | 246 | I |<-------------R1--------------| R | 247 | |--------------I2------------->| | 248 | |<-------------R2--------------| | 249 +-----+ +-----+ 251 Static Singly Homed Host 253 The Initiator would then send an I1 to the Responder's IP addresses 254 (IP-R). 256 3.2. Mobile end-host 258 A mobile HIP node (R) wishing to be reachable by reference to its 259 FQDN (www.example.com) would store in the DNS, possibly in addition 260 to its IP address(es) (IP-R), its HI (HI-R), HIT (HIT-R), and the 261 domain name(s) of its rendezvous server(s) (e.g., rvs.example.com) in 262 HIP resource record(s). The mobile HIP node also needs to notify its 263 rendezvous servers of any change in its set of IP address(es). 265 An Initiator willing to associate with such a mobile node would 266 typically issue the following queries: 268 o QNAME=www.example.com, QTYPE=HIP 269 Which returns a DNS packet with RCODE=0 and one or more HIP RRs with 270 the HIT, HI, and RVS domain name(s) (e.g., HIT-R, HI-R, and 271 rvs.example.com) of the Responder in the answer section. 273 o QNAME=rvs.example.com, QTYPE=A QNAME=www.example.com, QTYPE=AAAA 275 Which returns DNS packets with RCODE=0 and one or more A or AAAA RRs 276 containing IP address(es) of the Responder's RVS (e.g., IP-RVS) in 277 the answer section. 279 [HIP? ] 280 [www.example.com] 282 [A? ] 283 [rvs.example.com] +-----+ 284 +----------------------------------------->| | 285 | | DNS | 286 | +----------------------------------------| | 287 | | [HIP? ] +-----+ 288 | | [www.example.com ] 289 | | [HIP HIT-R HI-R rvs.example.com] 290 | | 291 | | [A? ] 292 | | [rvs.example.com] 293 | | [A IP-RVS ] 294 | | 295 | | +-----+ 296 | | +------I1----->| RVS |-----I1------+ 297 | | | +-----+ | 298 | | | | 299 | | | | 300 | v | v 301 +-----+ +-----+ 302 | |<---------------R1------------| | 303 | I |----------------I2----------->| R | 304 | |<---------------R2------------| | 305 +-----+ +-----+ 307 Mobile End-Host 309 The Initiator would then send an I1 to the RVS IP address (IP-RVS). 310 Following, the RVS will relay the I1 up to the mobile node's IP 311 address (IP-R), which will complete the HIP exchange. 313 4. Overview of Using the DNS with HIP 315 4.1. Storing HI, HIT, and RVS in the DNS 317 For any HIP node, its Host Identity (HI), the associated Host 318 Identity Tag (HIT), and the FQDN of its possible RVSs can be stored 319 in a DNS HIP RR. Any conforming implementation may store a Host 320 Identity (HI) and its associated Host Identity Tag (HIT) in a DNS HIP 321 RDATA format. HI and HIT are defined in Section 3 of the HIP 322 specification [I-D.ietf-hip-rfc5201-bis]. 324 Upon return of a HIP RR, a host MUST always calculate the HI- 325 derivative HIT to be used in the HIP exchange, as specified in 326 Section 3 of the HIP specification [I-D.ietf-hip-rfc5201-bis], while 327 the HIT possibly embedded along SHOULD only be used as an 328 optimization (e.g., table lookup). 330 The HIP resource record may also contain one or more domain name(s) 331 of rendezvous server(s) towards which HIP I1 packets might be sent to 332 trigger the establishment of an association with the entity named by 333 this resource record [I-D.ietf-hip-rfc5204-bis]. 335 The rendezvous server field of the HIP resource record stored at a 336 given owner name MAY include the owner name itself. A semantically 337 equivalent situation occurs if no rendezvous server is present in the 338 HIP resource record stored at that owner name. Such situations occur 339 in two cases: 341 o The host is mobile, and the A and/or AAAA resource record(s) 342 stored at its host name contain the IP address(es) of its 343 rendezvous server rather than its own one. 345 o The host is stationary, and can be reached directly at the IP 346 address(es) contained in the A and/or AAAA resource record(s) 347 stored at its host name. This is a degenerated case of rendezvous 348 service where the host somewhat acts as a rendezvous server for 349 itself. 351 An RVS receiving such an I1 would then relay it to the appropriate 352 Responder (the owner of the I1 receiver HIT). The Responder will 353 then complete the exchange with the Initiator, typically without 354 ongoing help from the RVS. 356 4.2. Initiating Connections Based on DNS Names 358 On a HIP node, a Host Identity Protocol exchange SHOULD be initiated 359 whenever a ULP attempts to communicate with an entity and the DNS 360 lookup returns HIP resource records. 362 5. HIP RR Storage Format 364 The RDATA for a HIP RR consists of a public key algorithm type, the 365 HIT length, a HIT, a public key, and optionally one or more 366 rendezvous server(s). 368 0 1 2 3 369 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 1 370 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 371 | HIT length | PK algorithm | PK length | 372 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 373 | | 374 ~ HIT ~ 375 | | 376 + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 377 | | | 378 +-+-+-+-+-+-+-+-+-+-+-+ + 379 | Public Key | 380 ~ ~ 381 | | 382 + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 383 | | | 384 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + 385 | | 386 ~ Rendezvous Servers ~ 387 | | 388 + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 389 | | 390 +-+-+-+-+-+-+-+ 392 The HIT length, PK algorithm, PK length, HIT, and Public Key fields 393 are REQUIRED. The Rendezvous Servers field is OPTIONAL. 395 5.1. HIT Length Format 397 The HIT length indicates the length in bytes of the HIT field. This 398 is an 8-bit unsigned integer. 400 5.2. PK Algorithm Format 402 The PK algorithm field indicates the public key cryptographic 403 algorithm and the implied public key field format. This is an 8-bit 404 unsigned integer. This document reuses the values defined for the 405 'algorithm type' of the IPSECKEY RR [RFC4025]. 407 Presently defined values are listed in Section 9 for reference. 409 5.3. PK Length Format 411 The PK length indicates the length in bytes of the Public key field. 412 This is a 16-bit unsigned integer in network byte order. 414 5.4. HIT Format 416 The HIT is stored as a binary value in network byte order. 418 5.5. Public Key Format 420 Both of the public key types defined in this document (RSA and DSA) 421 reuse the public key formats defined for the IPSECKEY RR [RFC4025]. 423 The DSA key format is defined in RFC 2536 [RFC2536]. 425 The RSA key format is defined in RFC 3110 [RFC3110] and the RSA key 426 size limit (4096 bits) is relaxed in the IPSECKEY RR [RFC4025] 427 specification. 429 5.6. Rendezvous Servers Format 431 The Rendezvous Servers field indicates one or more variable length 432 wire-encoded domain names of rendezvous server(s), as described in 433 Section 3.3 of RFC 1035 [RFC1035]. The wire-encoded format is self- 434 describing, so the length is implicit. The domain names MUST NOT be 435 compressed. The rendezvous server(s) are listed in order of 436 preference (i.e., first rendezvous server(s) are preferred), defining 437 an implicit order amongst rendezvous servers of a single RR. When 438 multiple HIP RRs are present at the same owner name, this implicit 439 order of rendezvous servers within an RR MUST NOT be used to infer a 440 preference order between rendezvous servers stored in different RRs. 442 6. HIP RR Presentation Format 444 This section specifies the representation of the HIP RR in a zone 445 master file. 447 The HIT length field is not represented, as it is implicitly known 448 thanks to the HIT field representation. 450 The PK algorithm field is represented as unsigned integers. 452 The HIT field is represented as the Base16 encoding [RFC4648] (a.k.a. 453 hex or hexadecimal) of the HIT. The encoding MUST NOT contain 454 whitespaces to distinguish it from the public key field. 456 The Public Key field is represented as the Base64 encoding [RFC4648] 457 of the public key. The encoding MUST NOT contain whitespace(s) to 458 distinguish it from the Rendezvous Servers field. 460 The PK length field is not represented, as it is implicitly known 461 thanks to the Public key field representation containing no 462 whitespaces. 464 The Rendezvous Servers field is represented by one or more domain 465 name(s) separated by whitespace(s). 467 The complete representation of the HPIHI record is: 469 IN HIP ( pk-algorithm 470 base16-encoded-hit 471 base64-encoded-public-key 472 rendezvous-server[1] 473 ... 474 rendezvous-server[n] ) 476 When no RVSs are present, the representation of the HPIHI record is: 478 IN HIP ( pk-algorithm 479 base16-encoded-hit 480 base64-encoded-public-key ) 482 7. Examples 484 In the examples below, the public key field containing no whitespace 485 is wrapped since it does not fit in a single line of this document. 487 Example of a node with HI and HIT but no RVS: 489 www.example.com. IN HIP ( 2 200100107B1A74DF365639CC39F1D578 490 AwEAAbdxyhNuSutc5EMzxTs9LBPCIkOFH8cIvM4p 491 9+LrV4e19WzK00+CI6zBCQTdtWsuxKbWIy87UOoJTwkUs7lBu+Upr1gsNrut79ryra+bSRGQ 492 b1slImA8YVJyuIDsj7kwzG7jnERNqnWxZ48AWkskmdHaVDP4BcelrTI3rMXdXF5D ) 494 Example of a node with a HI, HIT, and one RVS: 496 www.example.com. IN HIP ( 2 200100107B1A74DF365639CC39F1D578 497 AwEAAbdxyhNuSutc5EMzxTs9LBPCIkOFH8cIvM4p 498 9+LrV4e19WzK00+CI6zBCQTdtWsuxKbWIy87UOoJTwkUs7lBu+Upr1gsNrut79ryra+bSRGQ 499 b1slImA8YVJyuIDsj7kwzG7jnERNqnWxZ48AWkskmdHaVDP4BcelrTI3rMXdXF5D 500 rvs.example.com. ) 502 Example of a node with a HI, HIT, and two RVSs: 504 www.example.com. IN HIP ( 2 200100107B1A74DF365639CC39F1D578 505 AwEAAbdxyhNuSutc5EMzxTs9LBPCIkOFH8cIvM4p 506 9+LrV4e19WzK00+CI6zBCQTdtWsuxKbWIy87UOoJTwkUs7lBu+Upr1gsNrut79ryra+bSRGQ 507 b1slImA8YVJyuIDsj7kwzG7jnERNqnWxZ48AWkskmdHaVDP4BcelrTI3rMXdXF5D 508 rvs1.example.com. 509 rvs2.example.com. ) 511 8. Security Considerations 513 This section contains a description of the known threats involved 514 with the usage of the HIP DNS Extension. 516 In a manner similar to the IPSECKEY RR [RFC4025], the HIP DNS 517 Extension allows for the provision of two HIP nodes with the public 518 keying material (HI) of their peer. These HIs will be subsequently 519 used in a key exchange between the peers. Hence, the HIP DNS 520 Extension introduces the same kind of threats that IPSECKEY does, 521 plus threats caused by the possibility given to a HIP node to 522 initiate or accept a HIP exchange using "opportunistic" or 523 "unpublished Initiator HI" modes. 525 A HIP node SHOULD obtain HIP RRs from a trusted party trough a secure 526 channel ensuring data integrity and authenticity of the RRs. DNSSEC 527 [RFC4033] [RFC4034] [RFC4035] provides such a secure channel. 528 However, it should be emphasized that DNSSEC only offers data 529 integrity and authenticity guarantees to the channel between the DNS 530 server publishing a zone and the HIP node. DNSSEC does not ensure 531 that the entity publishing the zone is trusted. Therefore, the RRSIG 532 signature of the HIP RRSet MUST NOT be misinterpreted as a 533 certificate binding the HI and/or the HIT to the owner name. 535 In the absence of a proper secure channel, both parties are 536 vulnerable to MitM and DoS attacks, and unrelated parties might be 537 subject to DoS attacks as well. These threats are described in the 538 following sections. 540 8.1. Attacker Tampering with an Insecure HIP RR 542 The HIP RR contains public keying material in the form of the named 543 peer's public key (the HI) and its secure hash (the HIT). Both of 544 these are not sensitive to attacks where an adversary gains knowledge 545 of them. However, an attacker that is able to mount an active attack 546 on the DNS, i.e., tampers with this HIP RR (e.g., using DNS 547 spoofing), is able to mount Man-in-the-Middle attacks on the 548 cryptographic core of the eventual HIP exchange (Responder's HIP RR 549 rewritten by the attacker). 551 The HIP RR may contain a rendezvous server domain name resolved into 552 a destination IP address where the named peer is reachable by an I1, 553 as per the HIP Rendezvous Extension [I-D.ietf-hip-rfc5204-bis]. 554 Thus, an attacker able to tamper with this RR is able to redirect I1 555 packets sent to the named peer to a chosen IP address for DoS or MitM 556 attacks. Note that this kind of attack is not specific to HIP and 557 exists independently of whether or not HIP and the HIP RR are used. 558 Such an attacker might tamper with A and AAAA RRs as well. 560 An attacker might obviously use these two attacks in conjunction: It 561 will replace the Responder's HI and RVS IP address by its own in a 562 spoofed DNS packet sent to the Initiator HI, then redirect all 563 exchanged packets to him and mount a MitM on HIP. In this case, HIP 564 won't provide confidentiality nor Initiator HI protection from 565 eavesdroppers. 567 8.2. Hash and HITs Collisions 569 As with many cryptographic algorithms, some secure hashes (e.g., 570 SHA1, used by HIP to generate a HIT from an HI) eventually become 571 insecure, because an exploit has been found in which an attacker with 572 reasonable computation power breaks one of the security features of 573 the hash (e.g., its supposed collision resistance). This is why a 574 HIP end-node implementation SHOULD NOT authenticate its HIP peers 575 based solely on a HIT retrieved from the DNS, but SHOULD rather use 576 HI-based authentication. 578 8.3. DNSSEC 580 In the absence of DNSSEC, the HIP RR is subject to the threats 581 described in RFC 3833 [RFC3833]. 583 9. IANA Considerations 585 IANA has allocated one new RR type code (55) for the HIP RR from the 586 standard RR type space. 588 IANA does not need to open a new registry for public key algorithms 589 of the HIP RR because the HIP RR reuses "algorithms types" defined 590 for the IPSECKEY RR [RFC4025]. Presently defined values are shown 591 here for reference only: 593 0 is reserved 595 1 is DSA 597 2 is RSA 599 In the future, if a new algorithm is to be used for the HIP RR, a new 600 algorithm type and corresponding public key encoding should be 601 defined for the IPSECKEY RR. The HIP RR should reuse both the same 602 algorithm type and the same corresponding public key format as the 603 IPSECKEY RR. 605 10. Contributors 607 Pekka Nikander (pekka.nikander@nomadiclab.com) co-authored an 608 earlier, experimental version of this specification [RFC5205]. 610 11. Acknowledgments 612 As usual in the IETF, this document is the result of a collaboration 613 between many people. The authors would like to thank the author 614 (Michael Richardson), contributors, and reviewers of the IPSECKEY RR 615 [RFC4025] specification, after which this document was framed. The 616 authors would also like to thank the following people, who have 617 provided thoughtful and helpful discussions and/or suggestions, that 618 have helped improve this document: Jeff Ahrenholz, Rob Austein, Hannu 619 Flinck, Olafur Gudmundsson, Tom Henderson, Peter Koch, Olaf Kolkman, 620 Miika Komu, Andrew McGregor, Erik Nordmark, and Gabriel Montenegro. 621 Some parts of this document stem from the HIP specification 622 [I-D.ietf-hip-rfc5201-bis]. 624 12. References 626 12.1. Normative references 628 [I-D.ietf-hip-rfc5201-bis] Moskowitz, R., Heer, T., Jokela, P., and 629 T. Henderson, "Host Identity Protocol 630 Version 2 (HIPv2)", 631 draft-ietf-hip-rfc5201-bis-05 (work in 632 progress), March 2011. 634 [I-D.ietf-hip-rfc5204-bis] Laganier, J. and L. Eggert, "Host 635 Identity Protocol (HIP) Rendezvous 636 Extension", draft-ietf-hip-rfc5204-bis-00 637 (work in progress), August 2010. 639 [RFC1034] Mockapetris, P., "Domain names - concepts 640 and facilities", STD 13, RFC 1034, 641 November 1987. 643 [RFC1035] Mockapetris, P., "Domain names - 644 implementation and specification", 645 STD 13, RFC 1035, November 1987. 647 [RFC2119] Bradner, S., "Key words for use in RFCs 648 to Indicate Requirement Levels", BCP 14, 649 RFC 2119, March 1997. 651 [RFC2181] Elz, R. and R. Bush, "Clarifications to 652 the DNS Specification", RFC 2181, 653 July 1997. 655 [RFC3596] Thomson, S., Huitema, C., Ksinant, V., 656 and M. Souissi, "DNS Extensions to 657 Support IP Version 6", RFC 3596, 658 October 2003. 660 [RFC4025] Richardson, M., "A Method for Storing 661 IPsec Keying Material in DNS", RFC 4025, 662 March 2005. 664 [RFC4033] Arends, R., Austein, R., Larson, M., 665 Massey, D., and S. Rose, "DNS Security 666 Introduction and Requirements", RFC 4033, 667 March 2005. 669 [RFC4034] Arends, R., Austein, R., Larson, M., 670 Massey, D., and S. Rose, "Resource 671 Records for the DNS Security Extensions", 672 RFC 4034, March 2005. 674 [RFC4035] Arends, R., Austein, R., Larson, M., 675 Massey, D., and S. Rose, "Protocol 676 Modifications for the DNS Security 677 Extensions", RFC 4035, March 2005. 679 [RFC4648] Josefsson, S., "The Base16, Base32, and 680 Base64 Data Encodings", RFC 4648, 681 October 2006. 683 12.2. Informative references 685 [RFC2536] Eastlake, D., "DSA KEYs and SIGs in the 686 Domain Name System (DNS)", RFC 2536, 687 March 1999. 689 [RFC3110] Eastlake, D., "RSA/SHA-1 SIGs and RSA 690 KEYs in the Domain Name System (DNS)", 691 RFC 3110, May 2001. 693 [RFC3833] Atkins, D. and R. Austein, "Threat 694 Analysis of the Domain Name System 695 (DNS)", RFC 3833, August 2004. 697 [RFC4423] Moskowitz, R. and P. Nikander, "Host 698 Identity Protocol (HIP) Architecture", 699 RFC 4423, May 2006. 701 [RFC5205] Nikander, P. and J. Laganier, "Host 702 Identity Protocol (HIP) Domain Name 703 System (DNS) Extensions", RFC 5205, 704 April 2008. 706 [RFC5206] Henderson, T., Ed., "End-Host Mobility 707 and Multihoming with the Host Identity 708 Protocol", RFC 5206, April 2008. 710 Appendix A. Changes from RFC 5205 712 o Updated HIP references to revised HIP specifications. 714 Author's Address 716 Julien Laganier 717 Juniper Networks 718 1094 North Mathilda Avenue 719 Sunnyvale, CA 94089 720 USA 722 Phone: +1 408 936 0385 723 EMail: julien.ietf@gmail.com