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Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) -- Looks like a reference, but probably isn't: '1' on line 470 ** Obsolete normative reference: RFC 5201 (Obsoleted by RFC 7401) ** Obsolete normative reference: RFC 5204 (Obsoleted by RFC 8004) -- Obsolete informational reference (is this intentional?): RFC 4423 (Obsoleted by RFC 9063) -- Obsolete informational reference (is this intentional?): RFC 5205 (Obsoleted by RFC 8005) -- Obsolete informational reference (is this intentional?): RFC 5206 (Obsoleted by RFC 8046) Summary: 2 errors (**), 0 flaws (~~), 1 warning (==), 6 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group J. Laganier 3 Internet-Draft QUALCOMM Inc. 4 Obsoletes: 5205 (if approved) August 20, 2010 5 Intended status: Standards Track 6 Expires: February 21, 2011 8 Host Identity Protocol (HIP) Domain Name System (DNS) Extension 9 draft-ietf-hip-rfc5205-bis-00 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 February 21, 2011. 37 Copyright Notice 39 Copyright (c) 2010 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 82 1. Introduction 84 This document specifies a new resource record (RR) for the Domain 85 Name System (DNS) [RFC1034], and how to use it with the Host Identity 86 Protocol (HIP) [RFC5201]. This RR allows a HIP node to store in the 87 DNS its Host Identity (HI, the public component of the node public- 88 private key pair), Host Identity Tag (HIT, a truncated hash of its 89 HI), and the Domain Names of its rendezvous servers (RVSs) [RFC5204]. 91 Currently, most of the Internet applications that need to communicate 92 with a remote host first translate a domain name (often obtained via 93 user input) into one or more IP address(es). This step occurs prior 94 to communication with the remote host, and relies on a DNS lookup. 96 With HIP, IP addresses are intended to be used mostly for on-the-wire 97 communication between end hosts, while most Upper Layer Protocols 98 (ULP) and applications use HIs or HITs instead (ICMP might be an 99 example of an ULP not using them). Consequently, we need a means to 100 translate a domain name into an HI. Using the DNS for this 101 translation is pretty straightforward: We define a new HIP resource 102 record. Upon query by an application or ULP for a name to IP address 103 lookup, the resolver would then additionally perform a name to HI 104 lookup, and use it to construct the resulting HI to IP address 105 mapping (which is internal to the HIP layer). The HIP layer uses the 106 HI to IP address mapping to translate HIs and HITs into IP addresses 107 and vice versa. 109 The HIP Rendezvous Extension [RFC5204] allows a HIP node to be 110 reached via the IP address(es) of a third party, the node's 111 rendezvous server (RVS). An Initiator willing to establish a HIP 112 association with a Responder served by an RVS would typically 113 initiate a HIP exchange by sending an I1 towards the RVS IP address 114 rather than towards the Responder IP address. Consequently, we need 115 a means to find the name of a rendezvous server for a given host 116 name. 118 This document introduces the new HIP DNS resource record to store the 119 Rendezvous Server (RVS), Host Identity (HI), and Host Identity Tag 120 (HIT) information. 122 2. Conventions Used in This Document 124 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 125 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 126 document are to be interpreted as described in RFC 2119 [RFC2119]. 128 3. Usage Scenarios 130 In this section, we briefly introduce a number of usage scenarios 131 where the DNS is useful with the Host Identity Protocol. 133 With HIP, most applications and ULPs are unaware of the IP addresses 134 used to carry packets on the wire. Consequently, a HIP node could 135 take advantage of having multiple IP addresses for fail-over, 136 redundancy, mobility, or renumbering, in a manner that is transparent 137 to most ULPs and applications (because they are bound to HIs; hence, 138 they are agnostic to these IP address changes). 140 In these situations, for a node to be reachable by reference to its 141 Fully Qualified Domain Name (FQDN), the following information should 142 be stored in the DNS: 144 o A set of IP address(es) via A [RFC1035] and AAAA [RFC3596] RR sets 145 (RRSets [RFC2181]). 147 o A Host Identity (HI), Host Identity Tag (HIT), and possibly a set 148 of rendezvous servers (RVS) through HIP RRs. 150 When a HIP node wants to initiate communication with another HIP 151 node, it first needs to perform a HIP base exchange to set up a HIP 152 association towards its peer. Although such an exchange can be 153 initiated opportunistically, i.e., without prior knowledge of the 154 Responder's HI, by doing so both nodes knowingly risk man-in-the- 155 middle attacks on the HIP exchange. To prevent these attacks, it is 156 recommended that the Initiator first obtain the HI of the Responder, 157 and then initiate the exchange. This can be done, for example, 158 through manual configuration or DNS lookups. Hence, a new HIP RR is 159 introduced. 161 When a HIP node is frequently changing its IP address(es), the 162 natural DNS latency for propagating changes may prevent it from 163 publishing its new IP address(es) in the DNS. For solving this 164 problem, the HIP Architecture [RFC4423] introduces rendezvous servers 165 (RVSs) [RFC5204]. A HIP host uses a rendezvous server as a 166 rendezvous point to maintain reachability with possible HIP 167 initiators while moving [RFC5206]. Such a HIP node would publish in 168 the DNS its RVS domain name(s) in a HIP RR, while keeping its RVS up- 169 to-date with its current set of IP addresses. 171 When a HIP node wants to initiate a HIP exchange with a Responder, it 172 will perform a number of DNS lookups. Depending on the type of 173 implementation, the order in which those lookups will be issued may 174 vary. For instance, implementations using HIT in APIs may typically 175 first query for HIP resource records at the Responder FQDN, while 176 those using an IP address in APIs may typically first query for A 177 and/or AAAA resource records. 179 In the following, we assume that the Initiator first queries for HIP 180 resource records at the Responder FQDN. 182 If the query for the HIP type was responded to with a DNS answer with 183 RCODE=3 (Name Error), then the Responder's information is not present 184 in the DNS and further queries for the same owner name SHOULD NOT be 185 made. 187 In case the query for the HIP records returned a DNS answer with 188 RCODE=0 (No Error) and an empty answer section, it means that no HIP 189 information is available at the responder name. In such a case, if 190 the Initiator has been configured with a policy to fallback to 191 opportunistic HIP (initiating without knowing the Responder's HI) or 192 plain IP, it would send out more queries for A and AAAA types at the 193 Responder's FQDN. 195 Depending on the combinations of answers, the situations described in 196 Section 3.1 and Section 3.2 can occur. 198 Note that storing HIP RR information in the DNS at an FQDN that is 199 assigned to a non-HIP node might have ill effects on its reachability 200 by HIP nodes. 202 3.1. Simple Static Singly Homed End-Host 204 A HIP node (R) with a single static network attachment, wishing to be 205 reachable by reference to its FQDN (www.example.com), would store in 206 the DNS, in addition to its IP address(es) (IP-R), its Host Identity 207 (HI-R) and Host Identity Tag (HIT-R) in a HIP resource record. 209 An Initiator willing to associate with a node would typically issue 210 the following queries: 212 o QNAME=www.example.com, QTYPE=HIP 214 o (QCLASS=IN is assumed and omitted from the examples) 216 Which returns a DNS packet with RCODE=0 and one or more HIP RRs with 217 the HIT and HI (e.g., HIT-R and HI-R) of the Responder in the answer 218 section, but no RVS. 220 o QNAME=www.example.com, QTYPE=A QNAME=www.example.com, QTYPE=AAAA 222 Which returns DNS packets with RCODE=0 and one or more A or AAAA RRs 223 containing IP address(es) of the Responder (e.g., IP-R) in the answer 224 section. 226 Caption: In the remainder of this document, for the sake of keeping 227 diagrams simple and concise, several DNS queries and answers 228 are represented as one single transaction, while in fact 229 there are several queries and answers flowing back and 230 forth, as described in the textual examples. 232 [HIP? A? ] 233 [www.example.com] +-----+ 234 +-------------------------------->| | 235 | | DNS | 236 | +-------------------------------| | 237 | | [HIP? A? ] +-----+ 238 | | [www.example.com] 239 | | [HIP HIT-R HI-R ] 240 | | [A IP-R ] 241 | v 242 +-----+ +-----+ 243 | |--------------I1------------->| | 244 | I |<-------------R1--------------| R | 245 | |--------------I2------------->| | 246 | |<-------------R2--------------| | 247 +-----+ +-----+ 249 Static Singly Homed Host 251 The Initiator would then send an I1 to the Responder's IP addresses 252 (IP-R). 254 3.2. Mobile end-host 256 A mobile HIP node (R) wishing to be reachable by reference to its 257 FQDN (www.example.com) would store in the DNS, possibly in addition 258 to its IP address(es) (IP-R), its HI (HI-R), HIT (HIT-R), and the 259 domain name(s) of its rendezvous server(s) (e.g., rvs.example.com) in 260 HIP resource record(s). The mobile HIP node also needs to notify its 261 rendezvous servers of any change in its set of IP address(es). 263 An Initiator willing to associate with such a mobile node would 264 typically issue the following queries: 266 o QNAME=www.example.com, QTYPE=HIP 267 Which returns a DNS packet with RCODE=0 and one or more HIP RRs with 268 the HIT, HI, and RVS domain name(s) (e.g., HIT-R, HI-R, and 269 rvs.example.com) of the Responder in the answer section. 271 o QNAME=rvs.example.com, QTYPE=A QNAME=www.example.com, QTYPE=AAAA 273 Which returns DNS packets with RCODE=0 and one or more A or AAAA RRs 274 containing IP address(es) of the Responder's RVS (e.g., IP-RVS) in 275 the answer section. 277 [HIP? ] 278 [www.example.com] 280 [A? ] 281 [rvs.example.com] +-----+ 282 +----------------------------------------->| | 283 | | DNS | 284 | +----------------------------------------| | 285 | | [HIP? ] +-----+ 286 | | [www.example.com ] 287 | | [HIP HIT-R HI-R rvs.example.com] 288 | | 289 | | [A? ] 290 | | [rvs.example.com] 291 | | [A IP-RVS ] 292 | | 293 | | +-----+ 294 | | +------I1----->| RVS |-----I1------+ 295 | | | +-----+ | 296 | | | | 297 | | | | 298 | v | v 299 +-----+ +-----+ 300 | |<---------------R1------------| | 301 | I |----------------I2----------->| R | 302 | |<---------------R2------------| | 303 +-----+ +-----+ 305 Mobile End-Host 307 The Initiator would then send an I1 to the RVS IP address (IP-RVS). 308 Following, the RVS will relay the I1 up to the mobile node's IP 309 address (IP-R), which will complete the HIP exchange. 311 4. Overview of Using the DNS with HIP 313 4.1. Storing HI, HIT, and RVS in the DNS 315 For any HIP node, its Host Identity (HI), the associated Host 316 Identity Tag (HIT), and the FQDN of its possible RVSs can be stored 317 in a DNS HIP RR. Any conforming implementation may store a Host 318 Identity (HI) and its associated Host Identity Tag (HIT) in a DNS HIP 319 RDATA format. HI and HIT are defined in Section 3 of the HIP 320 specification [RFC5201]. 322 Upon return of a HIP RR, a host MUST always calculate the HI- 323 derivative HIT to be used in the HIP exchange, as specified in 324 Section 3 of the HIP specification [RFC5201], while the HIT possibly 325 embedded along SHOULD only be used as an optimization (e.g., table 326 lookup). 328 The HIP resource record may also contain one or more domain name(s) 329 of rendezvous server(s) towards which HIP I1 packets might be sent to 330 trigger the establishment of an association with the entity named by 331 this resource record [RFC5204]. 333 The rendezvous server field of the HIP resource record stored at a 334 given owner name MAY include the owner name itself. A semantically 335 equivalent situation occurs if no rendezvous server is present in the 336 HIP resource record stored at that owner name. Such situations occur 337 in two cases: 339 o The host is mobile, and the A and/or AAAA resource record(s) 340 stored at its host name contain the IP address(es) of its 341 rendezvous server rather than its own one. 343 o The host is stationary, and can be reached directly at the IP 344 address(es) contained in the A and/or AAAA resource record(s) 345 stored at its host name. This is a degenerated case of rendezvous 346 service where the host somewhat acts as a rendezvous server for 347 itself. 349 An RVS receiving such an I1 would then relay it to the appropriate 350 Responder (the owner of the I1 receiver HIT). The Responder will 351 then complete the exchange with the Initiator, typically without 352 ongoing help from the RVS. 354 4.2. Initiating Connections Based on DNS Names 356 On a HIP node, a Host Identity Protocol exchange SHOULD be initiated 357 whenever a ULP attempts to communicate with an entity and the DNS 358 lookup returns HIP resource records. 360 5. HIP RR Storage Format 362 The RDATA for a HIP RR consists of a public key algorithm type, the 363 HIT length, a HIT, a public key, and optionally one or more 364 rendezvous server(s). 366 0 1 2 3 367 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 1 368 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 369 | HIT length | PK algorithm | PK length | 370 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 371 | | 372 ~ HIT ~ 373 | | 374 + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 375 | | | 376 +-+-+-+-+-+-+-+-+-+-+-+ + 377 | Public Key | 378 ~ ~ 379 | | 380 + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 381 | | | 382 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + 383 | | 384 ~ Rendezvous Servers ~ 385 | | 386 + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 387 | | 388 +-+-+-+-+-+-+-+ 390 The HIT length, PK algorithm, PK length, HIT, and Public Key fields 391 are REQUIRED. The Rendezvous Servers field is OPTIONAL. 393 5.1. HIT Length Format 395 The HIT length indicates the length in bytes of the HIT field. This 396 is an 8-bit unsigned integer. 398 5.2. PK Algorithm Format 400 The PK algorithm field indicates the public key cryptographic 401 algorithm and the implied public key field format. This is an 8-bit 402 unsigned integer. This document reuses the values defined for the 403 'algorithm type' of the IPSECKEY RR [RFC4025]. 405 Presently defined values are listed in Section 9 for reference. 407 5.3. PK Length Format 409 The PK length indicates the length in bytes of the Public key field. 410 This is a 16-bit unsigned integer in network byte order. 412 5.4. HIT Format 414 The HIT is stored as a binary value in network byte order. 416 5.5. Public Key Format 418 Both of the public key types defined in this document (RSA and DSA) 419 reuse the public key formats defined for the IPSECKEY RR [RFC4025]. 421 The DSA key format is defined in RFC 2536 [RFC2536]. 423 The RSA key format is defined in RFC 3110 [RFC3110] and the RSA key 424 size limit (4096 bits) is relaxed in the IPSECKEY RR [RFC4025] 425 specification. 427 5.6. Rendezvous Servers Format 429 The Rendezvous Servers field indicates one or more variable length 430 wire-encoded domain names of rendezvous server(s), as described in 431 Section 3.3 of RFC 1035 [RFC1035]. The wire-encoded format is self- 432 describing, so the length is implicit. The domain names MUST NOT be 433 compressed. The rendezvous server(s) are listed in order of 434 preference (i.e., first rendezvous server(s) are preferred), defining 435 an implicit order amongst rendezvous servers of a single RR. When 436 multiple HIP RRs are present at the same owner name, this implicit 437 order of rendezvous servers within an RR MUST NOT be used to infer a 438 preference order between rendezvous servers stored in different RRs. 440 6. HIP RR Presentation Format 442 This section specifies the representation of the HIP RR in a zone 443 master file. 445 The HIT length field is not represented, as it is implicitly known 446 thanks to the HIT field representation. 448 The PK algorithm field is represented as unsigned integers. 450 The HIT field is represented as the Base16 encoding [RFC4648] (a.k.a. 451 hex or hexadecimal) of the HIT. The encoding MUST NOT contain 452 whitespaces to distinguish it from the public key field. 454 The Public Key field is represented as the Base64 encoding [RFC4648] 455 of the public key. The encoding MUST NOT contain whitespace(s) to 456 distinguish it from the Rendezvous Servers field. 458 The PK length field is not represented, as it is implicitly known 459 thanks to the Public key field representation containing no 460 whitespaces. 462 The Rendezvous Servers field is represented by one or more domain 463 name(s) separated by whitespace(s). 465 The complete representation of the HPIHI record is: 467 IN HIP ( pk-algorithm 468 base16-encoded-hit 469 base64-encoded-public-key 470 rendezvous-server[1] 471 ... 472 rendezvous-server[n] ) 474 When no RVSs are present, the representation of the HPIHI record is: 476 IN HIP ( pk-algorithm 477 base16-encoded-hit 478 base64-encoded-public-key ) 480 7. Examples 482 In the examples below, the public key field containing no whitespace 483 is wrapped since it does not fit in a single line of this document. 485 Example of a node with HI and HIT but no RVS: 487 www.example.com. IN HIP ( 2 200100107B1A74DF365639CC39F1D578 488 AwEAAbdxyhNuSutc5EMzxTs9LBPCIkOFH8cIvM4p 489 9+LrV4e19WzK00+CI6zBCQTdtWsuxKbWIy87UOoJTwkUs7lBu+Upr1gsNrut79ryra+bSRGQ 490 b1slImA8YVJyuIDsj7kwzG7jnERNqnWxZ48AWkskmdHaVDP4BcelrTI3rMXdXF5D ) 492 Example of a node with a HI, HIT, and one RVS: 494 www.example.com. IN HIP ( 2 200100107B1A74DF365639CC39F1D578 495 AwEAAbdxyhNuSutc5EMzxTs9LBPCIkOFH8cIvM4p 496 9+LrV4e19WzK00+CI6zBCQTdtWsuxKbWIy87UOoJTwkUs7lBu+Upr1gsNrut79ryra+bSRGQ 497 b1slImA8YVJyuIDsj7kwzG7jnERNqnWxZ48AWkskmdHaVDP4BcelrTI3rMXdXF5D 498 rvs.example.com. ) 500 Example of a node with a HI, HIT, and two RVSs: 502 www.example.com. IN HIP ( 2 200100107B1A74DF365639CC39F1D578 503 AwEAAbdxyhNuSutc5EMzxTs9LBPCIkOFH8cIvM4p 504 9+LrV4e19WzK00+CI6zBCQTdtWsuxKbWIy87UOoJTwkUs7lBu+Upr1gsNrut79ryra+bSRGQ 505 b1slImA8YVJyuIDsj7kwzG7jnERNqnWxZ48AWkskmdHaVDP4BcelrTI3rMXdXF5D 506 rvs1.example.com. 507 rvs2.example.com. ) 509 8. Security Considerations 511 This section contains a description of the known threats involved 512 with the usage of the HIP DNS Extension. 514 In a manner similar to the IPSECKEY RR [RFC4025], the HIP DNS 515 Extension allows for the provision of two HIP nodes with the public 516 keying material (HI) of their peer. These HIs will be subsequently 517 used in a key exchange between the peers. Hence, the HIP DNS 518 Extension introduces the same kind of threats that IPSECKEY does, 519 plus threats caused by the possibility given to a HIP node to 520 initiate or accept a HIP exchange using "opportunistic" or 521 "unpublished Initiator HI" modes. 523 A HIP node SHOULD obtain HIP RRs from a trusted party trough a secure 524 channel ensuring data integrity and authenticity of the RRs. DNSSEC 525 [RFC4033] [RFC4034] [RFC4035] provides such a secure channel. 526 However, it should be emphasized that DNSSEC only offers data 527 integrity and authenticity guarantees to the channel between the DNS 528 server publishing a zone and the HIP node. DNSSEC does not ensure 529 that the entity publishing the zone is trusted. Therefore, the RRSIG 530 signature of the HIP RRSet MUST NOT be misinterpreted as a 531 certificate binding the HI and/or the HIT to the owner name. 533 In the absence of a proper secure channel, both parties are 534 vulnerable to MitM and DoS attacks, and unrelated parties might be 535 subject to DoS attacks as well. These threats are described in the 536 following sections. 538 8.1. Attacker Tampering with an Insecure HIP RR 540 The HIP RR contains public keying material in the form of the named 541 peer's public key (the HI) and its secure hash (the HIT). Both of 542 these are not sensitive to attacks where an adversary gains knowledge 543 of them. However, an attacker that is able to mount an active attack 544 on the DNS, i.e., tampers with this HIP RR (e.g., using DNS 545 spoofing), is able to mount Man-in-the-Middle attacks on the 546 cryptographic core of the eventual HIP exchange (Responder's HIP RR 547 rewritten by the attacker). 549 The HIP RR may contain a rendezvous server domain name resolved into 550 a destination IP address where the named peer is reachable by an I1, 551 as per the HIP Rendezvous Extension [RFC5204]. Thus, an attacker 552 able to tamper with this RR is able to redirect I1 packets sent to 553 the named peer to a chosen IP address for DoS or MitM attacks. Note 554 that this kind of attack is not specific to HIP and exists 555 independently of whether or not HIP and the HIP RR are used. Such an 556 attacker might tamper with A and AAAA RRs as well. 558 An attacker might obviously use these two attacks in conjunction: It 559 will replace the Responder's HI and RVS IP address by its own in a 560 spoofed DNS packet sent to the Initiator HI, then redirect all 561 exchanged packets to him and mount a MitM on HIP. In this case, HIP 562 won't provide confidentiality nor Initiator HI protection from 563 eavesdroppers. 565 8.2. Hash and HITs Collisions 567 As with many cryptographic algorithms, some secure hashes (e.g., 568 SHA1, used by HIP to generate a HIT from an HI) eventually become 569 insecure, because an exploit has been found in which an attacker with 570 reasonable computation power breaks one of the security features of 571 the hash (e.g., its supposed collision resistance). This is why a 572 HIP end-node implementation SHOULD NOT authenticate its HIP peers 573 based solely on a HIT retrieved from the DNS, but SHOULD rather use 574 HI-based authentication. 576 8.3. DNSSEC 578 In the absence of DNSSEC, the HIP RR is subject to the threats 579 described in RFC 3833 [RFC3833]. 581 9. IANA Considerations 583 IANA has allocated one new RR type code (55) for the HIP RR from the 584 standard RR type space. 586 IANA does not need to open a new registry for public key algorithms 587 of the HIP RR because the HIP RR reuses "algorithms types" defined 588 for the IPSECKEY RR [RFC4025]. Presently defined values are shown 589 here for reference only: 591 0 is reserved 593 1 is DSA 595 2 is RSA 597 In the future, if a new algorithm is to be used for the HIP RR, a new 598 algorithm type and corresponding public key encoding should be 599 defined for the IPSECKEY RR. The HIP RR should reuse both the same 600 algorithm type and the same corresponding public key format as the 601 IPSECKEY RR. 603 10. Contributors 605 Pekka Nikander (pekka.nikander@nomadiclab.com) co-authored an 606 earlier, experimental version of this specification [RFC5205]. 608 11. Acknowledgments 610 As usual in the IETF, this document is the result of a collaboration 611 between many people. The authors would like to thank the author 612 (Michael Richardson), contributors, and reviewers of the IPSECKEY RR 613 [RFC4025] specification, after which this document was framed. The 614 authors would also like to thank the following people, who have 615 provided thoughtful and helpful discussions and/or suggestions, that 616 have helped improve this document: Jeff Ahrenholz, Rob Austein, Hannu 617 Flinck, Olafur Gudmundsson, Tom Henderson, Peter Koch, Olaf Kolkman, 618 Miika Komu, Andrew McGregor, Erik Nordmark, and Gabriel Montenegro. 619 Some parts of this document stem from the HIP specification 620 [RFC5201]. 622 12. References 624 12.1. Normative references 626 [RFC1034] Mockapetris, P., "Domain names - concepts and facilities", 627 STD 13, RFC 1034, November 1987. 629 [RFC1035] Mockapetris, P., "Domain names - implementation and 630 specification", STD 13, RFC 1035, November 1987. 632 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 633 Requirement Levels", BCP 14, RFC 2119, March 1997. 635 [RFC2181] Elz, R. and R. Bush, "Clarifications to the DNS 636 Specification", RFC 2181, July 1997. 638 [RFC3596] Thomson, S., Huitema, C., Ksinant, V., and M. Souissi, 639 "DNS Extensions to Support IP Version 6", RFC 3596, 640 October 2003. 642 [RFC4025] Richardson, M., "A Method for Storing IPsec Keying 643 Material in DNS", RFC 4025, March 2005. 645 [RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S. 646 Rose, "DNS Security Introduction and Requirements", 647 RFC 4033, March 2005. 649 [RFC4034] Arends, R., Austein, R., Larson, M., Massey, D., and S. 650 Rose, "Resource Records for the DNS Security Extensions", 651 RFC 4034, March 2005. 653 [RFC4035] Arends, R., Austein, R., Larson, M., Massey, D., and S. 654 Rose, "Protocol Modifications for the DNS Security 655 Extensions", RFC 4035, March 2005. 657 [RFC4648] Josefsson, S., "The Base16, Base32, and Base64 Data 658 Encodings", RFC 4648, October 2006. 660 [RFC5201] Moskowitz, R., Nikander, P., Jokela, P., Ed., and T. 661 Henderson, "Host Identity Protocol", RFC 5201, April 2008. 663 [RFC5204] Laganier, J. and L. Eggert, "Host Identity Protocol (HIP) 664 Rendezvous Extension", RFC 5204, April 2008. 666 12.2. Informative references 668 [RFC2536] Eastlake, D., "DSA KEYs and SIGs in the Domain Name System 669 (DNS)", RFC 2536, March 1999. 671 [RFC3110] Eastlake, D., "RSA/SHA-1 SIGs and RSA KEYs in the Domain 672 Name System (DNS)", RFC 3110, May 2001. 674 [RFC3833] Atkins, D. and R. Austein, "Threat Analysis of the Domain 675 Name System (DNS)", RFC 3833, August 2004. 677 [RFC4423] Moskowitz, R. and P. Nikander, "Host Identity Protocol 678 (HIP) Architecture", RFC 4423, May 2006. 680 [RFC5205] Nikander, P. and J. Laganier, "Host Identity Protocol 681 (HIP) Domain Name System (DNS) Extensions", RFC 5205, 682 April 2008. 684 [RFC5206] Henderson, T., Ed., "End-Host Mobility and Multihoming 685 with the Host Identity Protocol", RFC 5206, April 2008. 687 Author's Address 689 Julien Laganier 690 QUALCOMM Incorporated 691 5775 Morehouse Drive 692 San Diego, CA 92121 693 USA 695 Phone: +1 858 858 3538 696 EMail: julienl@qualcomm.com