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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) July 22, 2014 5 Intended status: Standards Track 6 Expires: January 23, 2015 8 Host Identity Protocol (HIP) Domain Name System (DNS) Extension 9 draft-ietf-hip-rfc5205-bis-05 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 January 23, 2015. 38 Copyright Notice 40 Copyright (c) 2014 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 Singly Homed End-Host . . . . . . . . . . . 5 59 3.2. Mobile end-host . . . . . . . . . . . . . . . . . . . . . 6 60 4. Overview of Using the DNS with HIP . . . . . . . . . . . . . 7 61 4.1. Storing HI, HIT, and RVS in the DNS . . . . . . . . . . . 7 62 4.2. Initiating Connections Based on DNS Names . . . . . . . . 8 63 5. HIP RR Storage Format . . . . . . . . . . . . . . . . . . . . 8 64 5.1. HIT Length Format . . . . . . . . . . . . . . . . . . . . 9 65 5.2. PK Algorithm Format . . . . . . . . . . . . . . . . . . . 9 66 5.3. PK Length Format . . . . . . . . . . . . . . . . . . . . 9 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 . . . . . . . . . . . . . . . . . 10 71 7. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 11 72 8. Security Considerations . . . . . . . . . . . . . . . . . . . 12 73 8.1. Attacker Tampering with an Insecure HIP RR . . . . . . . 12 74 8.2. Hash and HITs Collisions . . . . . . . . . . . . . . . . 13 75 8.3. DNSSEC . . . . . . . . . . . . . . . . . . . . . . . . . 13 76 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13 77 10. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 14 78 11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 14 79 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 14 80 12.1. Normative references . . . . . . . . . . . . . . . . . . 14 81 12.2. Informative references . . . . . . . . . . . . . . . . . 15 82 Appendix A. Changes from RFC 5205 . . . . . . . . . . . . . . . 16 84 1. Introduction 86 This document specifies a new resource record (RR) for the Domain 87 Name System (DNS) [RFC1034], and how to use it with the Host Identity 88 Protocol (HIP) [I-D.ietf-hip-rfc5201-bis]. This RR allows a HIP node 89 to store in the DNS its Host Identity (HI, the public component of 90 the node public-private key pair), Host Identity Tag (HIT, a 91 truncated hash of its HI), and the Domain Names of its rendezvous 92 servers (RVSs) [I-D.ietf-hip-rfc5204-bis]. 94 Currently, most of the Internet applications that need to communicate 95 with a remote host first translate a domain name (often obtained via 96 user input) into one or more IP address(es). This step occurs prior 97 to communication with the remote host, and relies on a DNS lookup. 99 With HIP, IP addresses are intended to be used mostly for on-the-wire 100 communication between end hosts, while most Upper Layer Protocols 101 (ULP) and applications use HIs or HITs instead (ICMP might be an 102 example of an ULP not using them). Consequently, we need a means to 103 translate a domain name into an HI. Using the DNS for this 104 translation is pretty straightforward: We define a new HIP resource 105 record. Upon query by an application or ULP for a name to IP address 106 lookup, the resolver would then additionally perform a name to HI 107 lookup, and use it to construct the resulting HI to IP address 108 mapping (which is internal to the HIP layer). The HIP layer uses the 109 HI to IP address mapping to translate HIs and HITs into IP addresses 110 and vice versa. 112 The HIP Rendezvous Extension [I-D.ietf-hip-rfc5204-bis] allows a HIP 113 node to be reached via the IP address(es) of a third party, the 114 node's rendezvous server (RVS). An Initiator willing to establish a 115 HIP association with a Responder served by an RVS would typically 116 initiate a HIP exchange by sending an I1 towards the RVS IP address 117 rather than towards the Responder IP address. Consequently, we need 118 a means to find the name of a rendezvous server for a given host 119 name. 121 This document introduces the new HIP DNS resource record to store the 122 Rendezvous Server (RVS), Host Identity (HI), and Host Identity Tag 123 (HIT) information. 125 2. Conventions Used in This Document 127 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 128 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 129 document are to be interpreted as described in RFC 2119 [RFC2119]. 131 3. Usage Scenarios 133 In this section, we briefly introduce a number of usage scenarios 134 where the DNS is useful with the Host Identity Protocol. 136 With HIP, most applications and ULPs are unaware of the IP addresses 137 used to carry packets on the wire. Consequently, a HIP node could 138 take advantage of having multiple IP addresses for fail-over, 139 redundancy, mobility, or renumbering, in a manner that is transparent 140 to most ULPs and applications (because they are bound to HIs; hence, 141 they are agnostic to these IP address changes). 143 In these situations, for a node to be reachable by reference to its 144 Fully Qualified Domain Name (FQDN), the following information should 145 be stored in the DNS: 147 o A set of IP address(es) via A [RFC1035] and AAAA [RFC3596] RR sets 148 (RRSets [RFC2181]). 150 o A Host Identity (HI), Host Identity Tag (HIT), and possibly a set 151 of rendezvous servers (RVS) through HIP RRs. 153 The HIP RR is class independent. 155 When a HIP node wants to initiate communication with another HIP 156 node, it first needs to perform a HIP base exchange to set up a HIP 157 association towards its peer. Although such an exchange can be 158 initiated opportunistically, i.e., without prior knowledge of the 159 Responder's HI, by doing so both nodes knowingly risk man-in-the- 160 middle attacks on the HIP exchange. To prevent these attacks, it is 161 recommended that the Initiator first obtain the HI of the Responder, 162 and then initiate the exchange. This can be done, for example, 163 through manual configuration or DNS lookups. Hence, a new HIP RR is 164 introduced. 166 When a HIP node is frequently changing its IP address(es), the 167 natural DNS latency for propagating changes may prevent it from 168 publishing its new IP address(es) in the DNS. For solving this 169 problem, the HIP Architecture [RFC4423] introduces rendezvous servers 170 (RVSs) [I-D.ietf-hip-rfc5204-bis]. A HIP host uses a rendezvous 171 server as a rendezvous point to maintain reachability with possible 172 HIP initiators while moving [RFC5206]. Such a HIP node would publish 173 in the DNS its RVS domain name(s) in a HIP RR, while keeping its RVS 174 up-to-date with its current set of IP addresses. 176 When a HIP node wants to initiate a HIP exchange with a Responder, it 177 will perform a number of DNS lookups. Depending on the type of 178 implementation, the order in which those lookups will be issued may 179 vary. For instance, implementations using HIT in APIs may typically 180 first query for HIP resource records at the Responder FQDN, while 181 those using an IP address in APIs may typically first query for A 182 and/or AAAA resource records. 184 In the following, we assume that the Initiator first queries for HIP 185 resource records at the Responder FQDN. 187 If the query for the HIP type was responded to with a DNS answer with 188 RCODE=3 (Name Error), then the Responder's information is not present 189 in the DNS and further queries for the same owner name SHOULD NOT be 190 made. 192 In case the query for the HIP records returned a DNS answer with 193 RCODE=0 (No Error) and an empty answer section, it means that no HIP 194 information is available at the responder name. In such a case, if 195 the Initiator has been configured with a policy to fallback to 196 opportunistic HIP (initiating without knowing the Responder's HI) or 197 plain IP, it would send out more queries for A and AAAA types at the 198 Responder's FQDN. 200 Depending on the combinations of answers, the situations described in 201 Section 3.1 and Section 3.2 can occur. 203 Note that storing HIP RR information in the DNS at an FQDN that is 204 assigned to a non-HIP node might have ill effects on its reachability 205 by HIP nodes. 207 3.1. Simple Static Singly Homed End-Host 209 A HIP node (R) with a single static network attachment, wishing to be 210 reachable by reference to its FQDN (www.example.com), would store in 211 the DNS, in addition to its IP address(es) (IP-R), its Host Identity 212 (HI-R) and Host Identity Tag (HIT-R) in a HIP resource record. 214 An Initiator willing to associate with a node would typically issue 215 the following queries: 217 o QNAME=www.example.com, QTYPE=HIP 219 o (QCLASS=IN is assumed and omitted from the examples) 221 Which returns a DNS packet with RCODE=0 and one or more HIP RRs with 222 the HIT and HI (e.g., HIT-R and HI-R) of the Responder in the answer 223 section, but no RVS. 225 o QNAME=www.example.com, QTYPE=A QNAME=www.example.com, QTYPE=AAAA 227 Which returns DNS packets with RCODE=0 and one or more A or AAAA RRs 228 containing IP address(es) of the Responder (e.g., IP-R) in the answer 229 section. 231 Caption: In the remainder of this document, for the sake of keeping 232 diagrams simple and concise, several DNS queries and answers 233 are represented as one single transaction, while in fact 234 there are several queries and answers flowing back and 235 forth, as described in the textual examples. 237 [HIP? A? ] 238 [www.example.com] +-----+ 239 +-------------------------------->| | 240 | | DNS | 241 | +-------------------------------| | 242 | | [HIP? A? ] +-----+ 243 | | [www.example.com] 244 | | [HIP HIT-R HI-R ] 245 | | [A IP-R ] 246 | v 247 +-----+ +-----+ 248 | |--------------I1------------->| | 249 | I |<-------------R1--------------| R | 250 | |--------------I2------------->| | 251 | |<-------------R2--------------| | 252 +-----+ +-----+ 254 Static Singly Homed Host 256 The Initiator would then send an I1 to the Responder's IP addresses 257 (IP-R). 259 3.2. Mobile end-host 261 A mobile HIP node (R) wishing to be reachable by reference to its 262 FQDN (www.example.com) would store in the DNS, possibly in addition 263 to its IP address(es) (IP-R), its HI (HI-R), HIT (HIT-R), and the 264 domain name(s) of its rendezvous server(s) (e.g., rvs.example.com) in 265 HIP resource record(s). The mobile HIP node also needs to notify its 266 rendezvous servers of any change in its set of IP address(es). 268 An Initiator willing to associate with such a mobile node would 269 typically issue the following queries: 271 o QNAME=www.example.com, QTYPE=HIP 273 Which returns a DNS packet with RCODE=0 and one or more HIP RRs with 274 the HIT, HI, and RVS domain name(s) (e.g., HIT-R, HI-R, and 275 rvs.example.com) of the Responder in the answer section. 277 o QNAME=rvs.example.com, QTYPE=A QNAME=www.example.com, QTYPE=AAAA 278 Which returns DNS packets with RCODE=0 and one or more A or AAAA RRs 279 containing IP address(es) of the Responder's RVS (e.g., IP-RVS) in 280 the answer section. 282 [HIP? ] 283 [www.example.com] 285 [A? ] 286 [rvs.example.com] +-----+ 287 +----------------------------------------->| | 288 | | DNS | 289 | +----------------------------------------| | 290 | | [HIP? ] +-----+ 291 | | [www.example.com ] 292 | | [HIP HIT-R HI-R rvs.example.com] 293 | | 294 | | [A? ] 295 | | [rvs.example.com] 296 | | [A IP-RVS ] 297 | | 298 | | +-----+ 299 | | +------I1----->| RVS |-----I1------+ 300 | | | +-----+ | 301 | | | | 302 | | | | 303 | v | v 304 +-----+ +-----+ 305 | |<---------------R1------------| | 306 | I |----------------I2----------->| R | 307 | |<---------------R2------------| | 308 +-----+ +-----+ 310 Mobile End-Host 312 The Initiator would then send an I1 to the RVS IP address (IP-RVS). 313 Following, the RVS will relay the I1 up to the mobile node's IP 314 address (IP-R), which will complete the HIP exchange. 316 4. Overview of Using the DNS with HIP 318 4.1. Storing HI, HIT, and RVS in the DNS 320 For any HIP node, its Host Identity (HI), the associated Host 321 Identity Tag (HIT), and the FQDN of its possible RVSs can be stored 322 in a DNS HIP RR. Any conforming implementation may store a Host 323 Identity (HI) and its associated Host Identity Tag (HIT) in a DNS HIP 324 RDATA format. HI and HIT are defined in Section 3 of the HIP 325 specification [I-D.ietf-hip-rfc5201-bis]. 327 Upon return of a HIP RR, a host MUST always calculate the HI- 328 derivative HIT to be used in the HIP exchange, as specified in 329 Section 3 of the HIP specification [I-D.ietf-hip-rfc5201-bis], while 330 the HIT possibly embedded along SHOULD only be used as an 331 optimization (e.g., table lookup). 333 The HIP resource record may also contain one or more domain name(s) 334 of rendezvous server(s) towards which HIP I1 packets might be sent to 335 trigger the establishment of an association with the entity named by 336 this resource record [I-D.ietf-hip-rfc5204-bis]. 338 The rendezvous server field of the HIP resource record stored at a 339 given owner name MAY include the owner name itself. A semantically 340 equivalent situation occurs if no rendezvous server is present in the 341 HIP resource record stored at that owner name. Such situations occur 342 in two cases: 344 o The host is mobile, and the A and/or AAAA resource record(s) 345 stored at its host name contain the IP address(es) of its 346 rendezvous server rather than its own one. 348 o The host is stationary, and can be reached directly at the IP 349 address(es) contained in the A and/or AAAA resource record(s) 350 stored at its host name. This is a degenerated case of rendezvous 351 service where the host somewhat acts as a rendezvous server for 352 itself. 354 An RVS receiving such an I1 would then relay it to the appropriate 355 Responder (the owner of the I1 receiver HIT). The Responder will 356 then complete the exchange with the Initiator, typically without 357 ongoing help from the RVS. 359 4.2. Initiating Connections Based on DNS Names 361 On a HIP node, a Host Identity Protocol exchange SHOULD be initiated 362 whenever a ULP attempts to communicate with an entity and the DNS 363 lookup returns HIP resource records. 365 5. HIP RR Storage Format 367 The RDATA for a HIP RR consists of a public key algorithm type, the 368 HIT length, a HIT, a public key, and optionally one or more 369 rendezvous server(s). 371 0 1 2 3 372 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 1 373 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 374 | HIT length | PK algorithm | PK length | 375 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 376 | | 377 ~ HIT ~ 378 | | 379 + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 380 | | | 381 +-+-+-+-+-+-+-+-+-+-+-+ + 382 | Public Key | 383 ~ ~ 384 | | 385 + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 386 | | | 387 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + 388 | | 389 ~ Rendezvous Servers ~ 390 | | 391 + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 392 | | 393 +-+-+-+-+-+-+-+ 395 The HIT length, PK algorithm, PK length, HIT, and Public Key fields 396 are REQUIRED. The Rendezvous Servers field is OPTIONAL. 398 5.1. HIT Length Format 400 The HIT length indicates the length in bytes of the HIT field. This 401 is an 8-bit unsigned integer. 403 5.2. PK Algorithm Format 405 The PK algorithm field indicates the public key cryptographic 406 algorithm and the implied public key field format. This is an 8-bit 407 unsigned integer. This document reuses the values defined for the 408 'algorithm type' of the IPSECKEY RR [RFC4025]. 410 Presently defined values are listed in Section 9 for reference. 412 5.3. PK Length Format 414 The PK length indicates the length in bytes of the Public key field. 415 This is a 16-bit unsigned integer in network byte order. 417 5.4. HIT Format 419 The HIT is stored as a binary value in network byte order. 421 5.5. Public Key Format 423 Two of the public key types defined in this document (RSA and DSA) 424 reuse the public key formats defined for the IPSECKEY RR [RFC4025]. 426 The DSA key format is defined in RFC 2536 [RFC2536]. 428 The RSA key format is defined in RFC 3110 [RFC3110] and the RSA key 429 size limit (4096 bits) is relaxed in the IPSECKEY RR [RFC4025] 430 specification. 432 In addition, this document similarly defines the public key format of 433 type ECDSA as the algorithm-specific portion of the DNSKEY RR RDATA 434 for ECDSA [RFC6605], i.e, all of the DNSKEY RR DATA after the first 435 four octets, corresponding to the same portion of the DNSKEY RR that 436 must be specified by documents that define a DNSSEC algorithm. 438 5.6. Rendezvous Servers Format 440 The Rendezvous Servers field indicates one or more variable length 441 wire-encoded domain names of rendezvous server(s), as described in 442 Section 3.3 of RFC 1035 [RFC1035]. The wire-encoded format is self- 443 describing, so the length is implicit. The domain names MUST NOT be 444 compressed. The rendezvous server(s) are listed in order of 445 preference (i.e., first rendezvous server(s) are preferred), defining 446 an implicit order amongst rendezvous servers of a single RR. When 447 multiple HIP RRs are present at the same owner name, this implicit 448 order of rendezvous servers within an RR MUST NOT be used to infer a 449 preference order between rendezvous servers stored in different RRs. 451 6. HIP RR Presentation Format 453 This section specifies the representation of the HIP RR in a zone 454 master file. 456 The HIT length field is not represented, as it is implicitly known 457 thanks to the HIT field representation. 459 The PK algorithm field is represented as unsigned integers. 461 The HIT field is represented as the Base16 encoding [RFC4648] (a.k.a. 462 hex or hexadecimal) of the HIT. The encoding MUST NOT contain 463 whitespaces to distinguish it from the public key field. 465 The Public Key field is represented as the Base64 encoding [RFC4648] 466 of the public key. The encoding MUST NOT contain whitespace(s) to 467 distinguish it from the Rendezvous Servers field. 469 The PK length field is not represented, as it is implicitly known 470 thanks to the Public key field representation containing no 471 whitespaces. 473 The Rendezvous Servers field is represented by one or more domain 474 name(s) separated by whitespace(s). 476 The complete representation of the HPIHI record is: 478 IN HIP ( pk-algorithm 479 base16-encoded-hit 480 base64-encoded-public-key 481 rendezvous-server[1] 482 ... 483 rendezvous-server[n] ) 485 When no RVSs are present, the representation of the HPIHI record is: 487 IN HIP ( pk-algorithm 488 base16-encoded-hit 489 base64-encoded-public-key ) 491 7. Examples 493 In the examples below, the public key field containing no whitespace 494 is wrapped since it does not fit in a single line of this document. 496 Example of a node with HI and HIT but no RVS: 498 www.example.com. IN HIP ( 2 200100107B1A74DF365639CC39F1D578 499 AwEAAbdxyhNuSutc5EMzxTs9LBPCIkOFH8cI 500 vM4p9+LrV4e19WzK00+CI6zBCQTdtWsuxKbWIy87UOoJTwkUs7lBu+Upr1gsNrut79ry 501 ra+bSRGQb1slImA8YVJyuIDsj7kwzG7jnERNqnWxZ48AWkskmdHaVDP4BcelrTI3rMXd 502 XF5D ) 504 Example of a node with a HI, HIT, and one RVS: 506 www.example.com. IN HIP ( 2 200100107B1A74DF365639CC39F1D578 507 AwEAAbdxyhNuSutc5EMzxTs9LBPCIkOFH8cI 508 vM4p9+LrV4e19WzK00+CI6zBCQTdtWsuxKbWIy87UOoJTwkUs7lBu+Upr1gsNrut79ry 509 ra+bSRGQb1slImA8YVJyuIDsj7kwzG7jnERNqnWxZ48AWkskmdHaVDP4BcelrTI3rMXd 510 XF5D 511 rvs.example.com. ) 513 Example of a node with a HI, HIT, and two RVSs: 515 www.example.com. IN HIP ( 2 200100107B1A74DF365639CC39F1D578 516 AwEAAbdxyhNuSutc5EMzxTs9LBPCIkOFH8cI 517 vM4p9+LrV4e19WzK00+CI6zBCQTdtWsuxKbWIy87UOoJTwkUs7lBu+Upr1gsNrut79ry 518 ra+bSRGQb1slImA8YVJyuIDsj7kwzG7jnERNqnWxZ48AWkskmdHaVDP4BcelrTI3rMXd 519 XF5D 520 rvs1.example.com. 521 rvs2.example.com. ) 523 8. Security Considerations 525 This section contains a description of the known threats involved 526 with the usage of the HIP DNS Extension. 528 In a manner similar to the IPSECKEY RR [RFC4025], the HIP DNS 529 Extension allows for the provision of two HIP nodes with the public 530 keying material (HI) of their peer. These HIs will be subsequently 531 used in a key exchange between the peers. Hence, the HIP DNS 532 Extension introduces the same kind of threats that IPSECKEY does, 533 plus threats caused by the possibility given to a HIP node to 534 initiate or accept a HIP exchange using "opportunistic" or 535 "unpublished Initiator HI" modes. 537 A HIP node SHOULD obtain HIP RRs from a trusted party trough a secure 538 channel ensuring data integrity and authenticity of the RRs. DNSSEC 539 [RFC4033] [RFC4034] [RFC4035] provides such a secure channel. 540 However, it should be emphasized that DNSSEC only offers data 541 integrity and authenticity guarantees to the channel between the DNS 542 server publishing a zone and the HIP node. DNSSEC does not ensure 543 that the entity publishing the zone is trusted. Therefore, the RRSIG 544 signature of the HIP RRSet MUST NOT be misinterpreted as a 545 certificate binding the HI and/or the HIT to the owner name. 547 In the absence of a proper secure channel, both parties are 548 vulnerable to MitM and DoS attacks, and unrelated parties might be 549 subject to DoS attacks as well. These threats are described in the 550 following sections. 552 8.1. Attacker Tampering with an Insecure HIP RR 554 The HIP RR contains public keying material in the form of the named 555 peer's public key (the HI) and its secure hash (the HIT). Both of 556 these are not sensitive to attacks where an adversary gains knowledge 557 of them. However, an attacker that is able to mount an active attack 558 on the DNS, i.e., tampers with this HIP RR (e.g., using DNS 559 spoofing), is able to mount Man-in-the-Middle attacks on the 560 cryptographic core of the eventual HIP exchange (Responder's HIP RR 561 rewritten by the attacker). 563 The HIP RR may contain a rendezvous server domain name resolved into 564 a destination IP address where the named peer is reachable by an I1, 565 as per the HIP Rendezvous Extension [I-D.ietf-hip-rfc5204-bis]. 566 Thus, an attacker able to tamper with this RR is able to redirect I1 567 packets sent to the named peer to a chosen IP address for DoS or MitM 568 attacks. Note that this kind of attack is not specific to HIP and 569 exists independently of whether or not HIP and the HIP RR are used. 570 Such an attacker might tamper with A and AAAA RRs as well. 572 An attacker might obviously use these two attacks in conjunction: It 573 will replace the Responder's HI and RVS IP address by its own in a 574 spoofed DNS packet sent to the Initiator HI, then redirect all 575 exchanged packets to him and mount a MitM on HIP. In this case, HIP 576 won't provide confidentiality nor Initiator HI protection from 577 eavesdroppers. 579 8.2. Hash and HITs Collisions 581 As with many cryptographic algorithms, some secure hashes (e.g., 582 SHA1, used by HIP to generate a HIT from an HI) eventually become 583 insecure, because an exploit has been found in which an attacker with 584 reasonable computation power breaks one of the security features of 585 the hash (e.g., its supposed collision resistance). This is why a 586 HIP end-node implementation SHOULD NOT authenticate its HIP peers 587 based solely on a HIT retrieved from the DNS, but SHOULD rather use 588 HI-based authentication. 590 8.3. DNSSEC 592 In the absence of DNSSEC, the HIP RR is subject to the threats 593 described in RFC 3833 [RFC3833]. 595 9. IANA Considerations 597 IANA has allocated one new RR type code (55) for the HIP RR from the 598 standard RR type space. 600 IANA does not need to open a new registry for public key algorithms 601 of the HIP RR because the HIP RR reuses "algorithms types" defined 602 for the IPSECKEY RR [RFC4025]. Presently defined values are: 604 0 is reserved 606 1 is DSA 607 2 is RSA 609 [IANA-TBD] is ECDSA 611 10. Contributors 613 Pekka Nikander (pekka.nikander@nomadiclab.com) co-authored an 614 earlier, experimental version of this specification [RFC5205]. 616 11. Acknowledgments 618 As usual in the IETF, this document is the result of a collaboration 619 between many people. The authors would like to thank the author 620 (Michael Richardson), contributors, and reviewers of the IPSECKEY RR 621 [RFC4025] specification, after which this document was framed. The 622 authors would also like to thank the following people, who have 623 provided thoughtful and helpful discussions and/or suggestions, that 624 have helped improve this document: Jeff Ahrenholz, Rob Austein, Hannu 625 Flinck, Olafur Gudmundsson, Tom Henderson, Peter Koch, Olaf Kolkman, 626 Miika Komu, Andrew McGregor, Erik Nordmark, and Gabriel Montenegro. 627 Some parts of this document stem from the HIP specification 628 [I-D.ietf-hip-rfc5201-bis]. 630 12. References 632 12.1. Normative references 634 [I-D.ietf-hip-rfc5201-bis] 635 Moskowitz, R., Heer, T., Jokela, P., and T. Henderson, 636 "Host Identity Protocol Version 2 (HIPv2)", draft-ietf- 637 hip-rfc5201-bis-14 (work in progress), October 2013. 639 [I-D.ietf-hip-rfc5204-bis] 640 Laganier, J. and L. Eggert, "Host Identity Protocol (HIP) 641 Rendezvous Extension", draft-ietf-hip-rfc5204-bis-04 (work 642 in progress), June 2014. 644 [RFC1034] Mockapetris, P., "Domain names - concepts and facilities", 645 STD 13, RFC 1034, November 1987. 647 [RFC1035] Mockapetris, P., "Domain names - implementation and 648 specification", STD 13, RFC 1035, November 1987. 650 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 651 Requirement Levels", BCP 14, RFC 2119, March 1997. 653 [RFC2181] Elz, R. and R. Bush, "Clarifications to the DNS 654 Specification", RFC 2181, July 1997. 656 [RFC3596] Thomson, S., Huitema, C., Ksinant, V., and M. Souissi, 657 "DNS Extensions to Support IP Version 6", RFC 3596, 658 October 2003. 660 [RFC4025] Richardson, M., "A Method for Storing IPsec Keying 661 Material in DNS", RFC 4025, March 2005. 663 [RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S. 664 Rose, "DNS Security Introduction and Requirements", RFC 665 4033, March 2005. 667 [RFC4034] Arends, R., Austein, R., Larson, M., Massey, D., and S. 668 Rose, "Resource Records for the DNS Security Extensions", 669 RFC 4034, March 2005. 671 [RFC4035] Arends, R., Austein, R., Larson, M., Massey, D., and S. 672 Rose, "Protocol Modifications for the DNS Security 673 Extensions", RFC 4035, March 2005. 675 [RFC4648] Josefsson, S., "The Base16, Base32, and Base64 Data 676 Encodings", RFC 4648, October 2006. 678 [RFC6605] Hoffman, P. and W. Wijngaards, "Elliptic Curve Digital 679 Signature Algorithm (DSA) for DNSSEC", RFC 6605, April 680 2012. 682 12.2. Informative references 684 [RFC2536] Eastlake, D., "DSA KEYs and SIGs in the Domain Name System 685 (DNS)", RFC 2536, March 1999. 687 [RFC3110] Eastlake, D., "RSA/SHA-1 SIGs and RSA KEYs in the Domain 688 Name System (DNS)", RFC 3110, May 2001. 690 [RFC3833] Atkins, D. and R. Austein, "Threat Analysis of the Domain 691 Name System (DNS)", RFC 3833, August 2004. 693 [RFC4423] Moskowitz, R. and P. Nikander, "Host Identity Protocol 694 (HIP) Architecture", RFC 4423, May 2006. 696 [RFC5205] Nikander, P. and J. Laganier, "Host Identity Protocol 697 (HIP) Domain Name System (DNS) Extensions", RFC 5205, 698 April 2008. 700 [RFC5206] Henderson, T., Ed., "End-Host Mobility and Multihoming 701 with the Host Identity Protocol", RFC 5206, April 2008. 703 Appendix A. Changes from RFC 5205 705 o Updated HIP references to revised HIP specifications. 707 o Extended DNS HIP RR to support for Host Identities based on 708 Elliptic Curve Digital Signature Algorithm (ECDSA). 710 Author's Address 712 Julien Laganier 713 Luminate Wireless, Inc. 714 Cupertino, CA 715 USA 717 EMail: julien.ietf@gmail.com