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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(See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Outdated reference: A later version (-10) exists of draft-ietf-sidr-pfx-validate-01 ** Obsolete normative reference: RFC 2385 (Obsoleted by RFC 5925) ** Downref: Normative reference to an Informational RFC: RFC 4808 ** Obsolete normative reference: RFC 5226 (Obsoleted by RFC 8126) ** Obsolete normative reference: RFC 5246 (Obsoleted by RFC 8446) == Outdated reference: A later version (-09) exists of draft-ietf-sidr-repos-struct-08 Summary: 5 errors (**), 0 flaws (~~), 3 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group R. Bush 3 Internet-Draft Internet Initiative Japan 4 Intended status: Standards Track R. Austein 5 Expires: December 31, 2011 ISC 6 June 29, 2011 8 The RPKI/Router Protocol 9 draft-ietf-sidr-rpki-rtr-13 11 Abstract 13 In order to formally validate the origin ASs of BGP announcements, 14 routers need a simple but reliable mechanism to receive RPKI 15 [I-D.ietf-sidr-arch] prefix origin data from a trusted cache. This 16 document describes a protocol to deliver validated prefix origin data 17 to routers. 19 Requirements Language 21 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 22 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 23 document are to be interpreted as described in [RFC2119]. 25 Status of this Memo 27 This Internet-Draft is submitted in full conformance with the 28 provisions of BCP 78 and BCP 79. 30 Internet-Drafts are working documents of the Internet Engineering 31 Task Force (IETF). Note that other groups may also distribute 32 working documents as Internet-Drafts. The list of current Internet- 33 Drafts is at http://datatracker.ietf.org/drafts/current/. 35 Internet-Drafts are draft documents valid for a maximum of six months 36 and may be updated, replaced, or obsoleted by other documents at any 37 time. It is inappropriate to use Internet-Drafts as reference 38 material or to cite them other than as "work in progress." 40 This Internet-Draft will expire on December 31, 2011. 42 Copyright Notice 44 Copyright (c) 2011 IETF Trust and the persons identified as the 45 document authors. All rights reserved. 47 This document is subject to BCP 78 and the IETF Trust's Legal 48 Provisions Relating to IETF Documents 49 (http://trustee.ietf.org/license-info) in effect on the date of 50 publication of this document. Please review these documents 51 carefully, as they describe your rights and restrictions with respect 52 to this document. Code Components extracted from this document must 53 include Simplified BSD License text as described in Section 4.e of 54 the Trust Legal Provisions and are provided without warranty as 55 described in the Simplified BSD License. 57 Table of Contents 59 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 60 2. Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 61 3. Deployment Structure . . . . . . . . . . . . . . . . . . . . . 4 62 4. Operational Overview . . . . . . . . . . . . . . . . . . . . . 4 63 5. Protocol Data Units (PDUs) . . . . . . . . . . . . . . . . . . 5 64 5.1. Serial Notify . . . . . . . . . . . . . . . . . . . . . . 6 65 5.2. Serial Query . . . . . . . . . . . . . . . . . . . . . . . 6 66 5.3. Reset Query . . . . . . . . . . . . . . . . . . . . . . . 7 67 5.4. Cache Response . . . . . . . . . . . . . . . . . . . . . . 7 68 5.5. IPv4 Prefix . . . . . . . . . . . . . . . . . . . . . . . 8 69 5.6. IPv6 Prefix . . . . . . . . . . . . . . . . . . . . . . . 9 70 5.7. End of Data . . . . . . . . . . . . . . . . . . . . . . . 9 71 5.8. Cache Reset . . . . . . . . . . . . . . . . . . . . . . . 10 72 5.9. Error Report . . . . . . . . . . . . . . . . . . . . . . . 10 73 5.10. Fields of a PDU . . . . . . . . . . . . . . . . . . . . . 11 74 6. Protocol Sequences . . . . . . . . . . . . . . . . . . . . . . 12 75 6.1. Start or Restart . . . . . . . . . . . . . . . . . . . . . 13 76 6.2. Typical Exchange . . . . . . . . . . . . . . . . . . . . . 14 77 6.3. No Incremental Update Available . . . . . . . . . . . . . 14 78 6.4. Cache has No Data Available . . . . . . . . . . . . . . . 15 79 7. Transport . . . . . . . . . . . . . . . . . . . . . . . . . . 15 80 7.1. SSH Transport . . . . . . . . . . . . . . . . . . . . . . 16 81 7.2. TLS Transport . . . . . . . . . . . . . . . . . . . . . . 17 82 7.3. TCP MD5 Transport . . . . . . . . . . . . . . . . . . . . 17 83 7.4. TCP-AO Transport . . . . . . . . . . . . . . . . . . . . . 17 84 8. Router-Cache Set-Up . . . . . . . . . . . . . . . . . . . . . 18 85 9. Deployment Scenarios . . . . . . . . . . . . . . . . . . . . . 19 86 10. Error Codes . . . . . . . . . . . . . . . . . . . . . . . . . 20 87 11. Security Considerations . . . . . . . . . . . . . . . . . . . 20 88 12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 22 89 13. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 22 90 14. References . . . . . . . . . . . . . . . . . . . . . . . . . . 23 91 14.1. Normative References . . . . . . . . . . . . . . . . . . . 23 92 14.2. Informative References . . . . . . . . . . . . . . . . . . 24 93 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 24 95 1. Introduction 97 In order to formally validate the origin ASs of BGP announcements, 98 routers need a simple but reliable mechanism to receive RPKI 99 [I-D.ietf-sidr-arch] formally validated prefix origin data from a 100 trusted cache. This document describes a protocol to deliver 101 validated prefix origin data to routers. 103 Section 3 describes the deployment structure and Section 4 then 104 presents an operational overview. The binary payloads of the 105 protocol are formally described in Section 5, and the expected PDU 106 sequences are described in Section 6. The transport protocol options 107 are described in Section 7. Section 8 details how routers and caches 108 are configured to connect and authenticate. Section 9 describes 109 likely deployment scenarios. The traditional security and IANA 110 considerations end the document. 112 The protocol is extensible to support new PDUs with new semantics 113 when and as needed, as indicated by deployment experience. PDUs are 114 versioned should deployment experience call for change. 116 2. Glossary 118 The following terms are used with special meaning: 120 Global RPKI: The authoritative data of the RPKI are published in a 121 distributed set of servers at the IANA, RIRs, NIRs, and ISPs, see 122 [I-D.ietf-sidr-repos-struct]. 124 Cache: A coalesced copy of the RPKI which is periodically fetched/ 125 refreshed directly or indirectly from the global RPKI using the 126 [RFC5781] protocol/tools. Relying party update software such as 127 rcynic is used to gather and validate the distributed data of the 128 RPKI into a cache. Trusting this cache further is a matter 129 between the provider of the cache and a relying party. 131 Serial Number: A 32-bit monotonically increasing ordinal which wraps 132 from 2^32-1 to 0. It denotes the logical version of a cache. A 133 cache increments the value by one when it successfully updates its 134 data from a parent cache or from primary RPKI data. As a cache is 135 receiving, new incoming data and implicit deletes are marked with 136 the new serial but MUST NOT be sent until the fetch is complete. 137 A serial number is not commensurate between caches, nor need it be 138 maintained across resets of the cache server. See [RFC1982] on 139 DNS Serial Number Arithmetic for too much detail on serial number 140 arithmetic. 142 Nonce: When a cache server is started, it generates a nonce to 143 identify the instance of the cache and to bind it to the sequence 144 of Serial Numbers that cache instance will generate. This allows 145 the router to restart a failed session knowing that the Serial 146 Number it is using is commensurate with that of the cache. 148 3. Deployment Structure 150 Deployment of the RPKI to reach routers has a three level structure 151 as follows: 153 Global RPKI: The authoritative data of the RPKI are published in a 154 distributed set of servers, RPKI publication repositories, e.g. 155 the IANA, RIRs, NIRs, and ISPs, see [I-D.ietf-sidr-repos-struct]. 157 Local Caches: A local set of one or more collected and verified 158 caches. A relying party, e.g. router or other client, MUST have a 159 trust relationship with, and a trusted transport channel to, any 160 authoritative cache(s) it uses. 162 Routers: A router fetches data from a local cache using the protocol 163 described in this document. It is said to be a client of the 164 cache. There MAY be mechanisms for the router to assure itself of 165 the authenticity of the cache and to authenticate itself to the 166 cache. 168 4. Operational Overview 170 A router establishes and keeps open a connection to one or more 171 caches with which it has client/server relationships. It is 172 configured with a semi-ordered list of caches, and establishes a 173 connection to the most preferred cache, or set of caches, which 174 accept the connections. 176 The router MUST choose the most preferred, by configuration, cache or 177 set of caches so that the operator may control load on their caches 178 and the Global RPKI. 180 Periodically, the router sends to the cache the serial number of the 181 highest numbered data it has received from that cache, i.e. the 182 router's current serial number. When a router establishes a new 183 connection to a cache, or wishes to reset a current relationship, it 184 sends a Reset Query. 186 The Cache responds with all data records which have serial numbers 187 greater than that in the router's query. This may be the null set, 188 in which case the End of Data PDU is still sent. Note that 'greater' 189 must take wrap-around into account, see [RFC1982]. 191 When the router has received all data records from the cache, it sets 192 its current serial number to that of the serial number in the End of 193 Data PDU. 195 When the cache updates its database, it sends a Notify message to 196 every currently connected router. This is a hint that now would be a 197 good time for the router to poll for an update, but is only a hint. 198 The protocol requires the router to poll for updates periodically in 199 any case. 201 Strictly speaking, a router could track a cache simply by asking for 202 a complete data set every time it updates, but this would be very 203 inefficient. The serial number based incremental update mechanism 204 allows an efficient transfer of just the data records which have 205 changed since last update. As with any update protocol based on 206 incremental transfers, the router must be prepared to fall back to a 207 full transfer if for any reason the cache is unable to provide the 208 necessary incremental data. Unlike some incremental transfer 209 protocols, this protocol requires the router to make an explicit 210 request to start the fallback process; this is deliberate, as the 211 cache has no way of knowing whether the router has also established 212 sessions with other caches that may be able to provide better 213 service. 215 As a cache server must evaluate certificates and ROAs which are time 216 dependent, servers' clocks MUST be correct to a tolerance of 217 approximately an hour. 219 5. Protocol Data Units (PDUs) 221 The exchanges between the cache and the router are sequences of 222 exchanges of the following PDUs according to the rules described in 223 Section 6. 225 5.1. Serial Notify 227 The cache notifies the router that the cache has new data. 229 The Cache Nonce reassures the router that the serial numbers are 230 commensurate, i.e. the cache session has not been changed. 232 0 8 16 24 31 233 .-------------------------------------------. 234 | Protocol | PDU | | 235 | Version | Type | Cache Nonce | 236 | 0 | 0 | | 237 +-------------------------------------------+ 238 | | 239 | Length=12 | 240 | | 241 +-------------------------------------------+ 242 | | 243 | Serial Number | 244 | | 245 `-------------------------------------------' 247 5.2. Serial Query 249 Serial Query: The router sends Serial Query to ask the cache for all 250 payload PDUs which have serial numbers higher than the serial number 251 in the Serial Query. 253 The cache replies to this query with a Cache Response PDU 254 (Section 5.4) if the cache has a record of the changes since the 255 serial number specified by the router. If there have been no changes 256 since the router last queried, the cache responds with an End Of Data 257 PDU. If the cache does not have the data needed to update the 258 router, perhaps because its records do not go back to the Serial 259 Number in the Serial Query, then it responds with a Cache Reset PDU 260 (Section 5.8). 262 The Cache Nonce tells the cache what instance the router expects to 263 ensure that the serial numbers are commensurate, i.e. the cache 264 session has not been changed. 266 0 8 16 24 31 267 .-------------------------------------------. 268 | Protocol | PDU | | 269 | Version | Type | Cache Nonce | 270 | 0 | 1 | | 271 +-------------------------------------------+ 272 | | 273 | Length=12 | 274 | | 275 +-------------------------------------------+ 276 | | 277 | Serial Number | 278 | | 279 `-------------------------------------------' 281 5.3. Reset Query 283 Reset Query: The router tells the cache that it wants to receive the 284 total active, current, non-withdrawn, database. The cache responds 285 with a Cache Response PDU (Section 5.4). 287 0 8 16 24 31 288 .-------------------------------------------. 289 | Protocol | PDU | | 290 | Version | Type | reserved = zero | 291 | 0 | 2 | | 292 +-------------------------------------------+ 293 | | 294 | Length=8 | 295 | | 296 `-------------------------------------------' 298 5.4. Cache Response 300 Cache Response: The cache responds with zero or more payload PDUs. 301 When replying to a Serial Query request (Section 5.2), the cache 302 sends the set of all data records it has with serial numbers greater 303 than that sent by the client router. When replying to a Reset Query, 304 the cache sends the set of all data records it has; in this case the 305 withdraw/announce field in the payload PDUs MUST have the value 1 306 (announce). 308 In response to a Reset Query, the new value of Cache Nonce tells the 309 router the instance of the cache session for future confirmation. In 310 response to a Serial Query, the Cache Nonce being the same reassures 311 the router that the serial numbers are commensurate, i.e. the cache 312 session has not changed. 314 0 8 16 24 31 315 .-------------------------------------------. 316 | Protocol | PDU | | 317 | Version | Type | Cache Nonce | 318 | 0 | 3 | | 319 +-------------------------------------------+ 320 | | 321 | Length=8 | 322 | | 323 `-------------------------------------------' 325 5.5. IPv4 Prefix 327 0 8 16 24 31 328 .-------------------------------------------. 329 | Protocol | PDU | | 330 | Version | Type | reserved = zero | 331 | 0 | 4 | | 332 +-------------------------------------------+ 333 | | 334 | Length=20 | 335 | | 336 +-------------------------------------------+ 337 | | Prefix | Max | | 338 | Flags | Length | Length | zero | 339 | | 0..32 | 0..32 | | 340 +-------------------------------------------+ 341 | | 342 | IPv4 Prefix | 343 | | 344 +-------------------------------------------+ 345 | | 346 | Autonomous System Number | 347 | | 348 `-------------------------------------------' 350 The lowest order bit of the Flags field is 1 for an announcement and 351 0 for a withdrawal. 353 In the RPKI, nothing prevents a signing certificate from issuing two 354 identical ROAs, and nothing prohibits the existence of two identical 355 route: or route6: objects in the IRR. In this case there would be no 356 semantic difference between the objects, merely a process redundancy. 358 In the RPKI, there is also an actual need for what might appear to a 359 router as identical IPvX PDUs. This can occur when an upstream 360 certificate is being reissued or there is an address ownership 361 transfer up the validation chain. The ROA would be identical in the 362 router sense, i.e. have the same {prefix, len, max-len, asn}, but a 363 different validation path in the RPKI. This is important to the 364 RPKI, but not to the router. 366 The cache server is responsible for assuring that it has told the 367 router client to have one and only one IPvX PDU for a unique {prefix, 368 len, max-len, asn} at any one point in time. Should the router 369 client receive an IPvX PDU with a {prefix, len, max-len, asn} 370 identical to one it already has active, it SHOULD raise a Duplicate 371 Announcement Received error. 373 5.6. IPv6 Prefix 375 0 8 16 24 31 376 .-------------------------------------------. 377 | Protocol | PDU | | 378 | Version | Type | reserved = zero | 379 | 0 | 6 | | 380 +-------------------------------------------+ 381 | | 382 | Length=32 | 383 | | 384 +-------------------------------------------+ 385 | | Prefix | Max | | 386 | Flags | Length | Length | zero | 387 | | 0..128 | 0..128 | | 388 +-------------------------------------------+ 389 | | 390 +--- ---+ 391 | | 392 +--- IPv6 Prefix ---+ 393 | | 394 +--- ---+ 395 | | 396 +-------------------------------------------+ 397 | | 398 | Autonomous System Number | 399 | | 400 `-------------------------------------------' 402 5.7. End of Data 404 End of Data: Cache tells router it has no more data for the request. 406 The Cache Nonce MUST be the same as that of the corresponding Cache 407 Response which began the, possibly null, sequence of data PDUs. 409 0 8 16 24 31 410 .-------------------------------------------. 411 | Protocol | PDU | | 412 | Version | Type | Cache Nonce | 413 | 0 | 7 | | 414 +-------------------------------------------+ 415 | | 416 | Length=12 | 417 | | 418 +-------------------------------------------+ 419 | | 420 | Serial Number | 421 | | 422 `-------------------------------------------' 424 5.8. Cache Reset 426 The cache may respond to a Serial Query informing the router that the 427 cache cannot provide an incremental update starting from the serial 428 number specified by the router. The router must decide whether to 429 issue a Reset Query or switch to a different cache. 431 0 8 16 24 31 432 .-------------------------------------------. 433 | Protocol | PDU | | 434 | Version | Type | reserved = zero | 435 | 0 | 8 | | 436 +-------------------------------------------+ 437 | | 438 | Length=8 | 439 | | 440 `-------------------------------------------' 442 5.9. Error Report 444 This PDU is used by either party to report an error to the other. 446 The Error Code is described in Section 10. 448 If the error is not associated with any particular PDU, the Erroneous 449 PDU field MUST be empty and the Length of Encapsulated PDU field MUST 450 be zero. 452 An Error Report PDU MUST NOT be sent for an Error Report PDU. 454 If the error is associated with a PDU of excessive, or possibly 455 corrupt, length, the Erroneous PDU field MAY be truncated. 457 The diagnostic text is optional, if not present the Length of Error 458 Text field SHOULD be zero. If error text is present, it SHOULD be a 459 string in US-ASCII, for maximum portability; if non-US-ASCII 460 characters are absolutely required, the error text MUST use UTF-8 461 encoding. 463 0 8 16 24 31 464 .-------------------------------------------. 465 | Protocol | PDU | | 466 | Version | Type | Error Code | 467 | 0 | 10 | | 468 +-------------------------------------------+ 469 | | 470 | Length | 471 | | 472 +-------------------------------------------+ 473 | | 474 | Length of Encapsulated PDU | 475 | | 476 +-------------------------------------------+ 477 | | 478 ~ Copy of Erroneous PDU ~ 479 | | 480 +-------------------------------------------+ 481 | | 482 | Length of Error Text | 483 | | 484 +-------------------------------------------+ 485 | | 486 | Arbitrary Text | 487 | of | 488 ~ Error Diagnostic Message ~ 489 | | 490 `-------------------------------------------' 492 5.10. Fields of a PDU 494 PDUs contain the following data elements: 496 Protocol Version: An ordinal, currently 0, denoting the version of 497 this protocol. 499 Serial Number: The serial number of the RPKI Cache when this ROA was 500 received from the cache's up-stream cache server or gathered from 501 the global RPKI. A cache increments its serial number when 502 completing an rigorously validated update from a parent cache, for 503 example via rcynic. See [RFC1982] on DNS Serial Number Arithmetic 504 for too much detail on serial number arithmetic. 506 Cache Nonce: When a cache server is started, it generates a nonce to 507 identify the instance of the cache and to bind it to the sequence 508 of Serial Numbers that cache instance will generate. This allows 509 the router to restart a failed session knowing that the Serial 510 Number it is using is commensurate with that of the cache. If, at 511 any time, either the router or the cache finds the value of the 512 nonces they hold disagree, they MUST completely drop the session 513 and the router MUST flush all data learned from that cache. 515 The nonce might be a pseudo-random, a monotonically increasing 516 value if the cache has reliable storage, etc. An implementation 517 which uses a fine granularity of time for the Serial Number might 518 never change the Cache Nonce. 520 Length: A 32 bit ordinal which has as its value the count of the 521 bytes in the entire PDU, including the eight bytes of header which 522 end with the length field. 524 Flags: The lowest order bit of the Flags field is 1 for an 525 announcement and 0 for a withdrawal, whether this PDU announces a 526 new right to announce the prefix or withdraws a previously 527 announced right. A withdraw effectively deletes one previously 528 announced IPvX Prefix PDU with the exact same Prefix, Length, Max- 529 Len, and ASN. 531 Prefix Length: An ordinal denoting the shortest prefix allowed for 532 the prefix. 534 Max Length: An ordinal denoting the longest prefix allowed by the 535 prefix. This MUST NOT be less than the Prefix Length element. 537 Prefix: The IPv4 or IPv6 prefix of the ROA. 539 Autonomous System Number: ASN allowed to announce this prefix, a 32 540 bit ordinal. 542 Zero: Fields shown as zero or reserved MUST be zero. The value of 543 such a field MUST be ignored on receipt. 545 6. Protocol Sequences 547 The sequences of PDU transmissions fall into three conversations as 548 follows: 550 6.1. Start or Restart 552 Cache Router 553 ~ ~ 554 | <----- Reset Query -------- | R requests data (or Serial Query) 555 | | 556 | ----- Cache Response -----> | C confirms request 557 | ------- IPvX Prefix ------> | C sends zero or more 558 | ------- IPvX Prefix ------> | IPv4 and IPv6 Prefix 559 | ------- IPvX Prefix ------> | Payload PDUs 560 | ------ End of Data ------> | C sends End of Data 561 | | and sends new serial 562 ~ ~ 564 When a transport session is first established, the router MAY send a 565 Reset Query and the cache responds with a data sequence of all data 566 it contains. 568 Alternatively, if the router has significant unexpired data from a 569 broken session with the same cache, it MAY start with a Serial Query 570 containing the Cache Nonce from the previous session to ensure the 571 serial numbers are commensurate. 573 This Reset Query sequence is also used when the router receives a 574 Cache Reset, chooses a new cache, or fears that it has otherwise lost 575 its way. 577 To limit the length of time a cache must keep the data necessary to 578 generate incremental updates, a router MUST send either a Serial 579 Query or a Reset Query no less frequently than once an hour. This 580 also acts as a keep alive at the application layer. 582 As the cache MAY not keep updates for little more than one hour, the 583 router MUST have a polling interval of no greater than once an hour. 585 6.2. Typical Exchange 587 Cache Router 588 ~ ~ 589 | -------- Notify ----------> | (optional) 590 | | 591 | <----- Serial Query ------- | R requests data 592 | | 593 | ----- Cache Response -----> | C confirms request 594 | ------- IPvX Prefix ------> | C sends zero or more 595 | ------- IPvX Prefix ------> | IPv4 and IPv6 Prefix 596 | ------- IPvX Prefix ------> | Payload PDUs 597 | ------ End of Data ------> | C sends End of Data 598 | | and sends new serial 599 ~ ~ 601 The cache server SHOULD send a notify PDU with its current serial 602 number when the cache's serial changes, with the expectation that the 603 router MAY then issue a serial query earlier than it otherwise might. 604 This is analogous to DNS NOTIFY in [RFC1996]. The cache MUST rate 605 limit Serial Notifies to no more frequently than one per minute. 607 When the transport layer is up and either a timer has gone off in the 608 router, or the cache has sent a Notify, the router queries for new 609 data by sending a Serial Query, and the cache sends all data newer 610 than the serial in the Serial Query. 612 To limit the length of time a cache must keep old withdraws, a router 613 MUST send either a Serial Query or a Reset Query no less frequently 614 than once an hour. 616 6.3. No Incremental Update Available 618 Cache Router 619 ~ ~ 620 | <----- Serial Query ------ | R requests data 621 | ------- Cache Reset ------> | C cannot supply update 622 | | from specified serial 623 | <------ Reset Query ------- | R requests new data 624 | ----- Cache Response -----> | C confirms request 625 | ------- IPvX Prefix ------> | C sends zero or more 626 | ------- IPvX Prefix ------> | IPv4 and IPv6 Prefix 627 | ------- IPvX Prefix ------> | Payload PDUs 628 | ------ End of Data ------> | C sends End of Data 629 | | and sends new serial 630 ~ ~ 632 The cache may respond to a Serial Query with a Cache Reset, informing 633 the router that the cache cannot supply an incremental update from 634 the serial number specified by the router. This might be because the 635 cache has lost state, or because the router has waited too long 636 between polls and the cache has cleaned up old data that it no longer 637 believes it needs, or because the cache has run out of storage space 638 and had to expire some old data early. Regardless of how this state 639 arose, the cache replies with a Cache Reset to tell the router that 640 it cannot honor the request. When a router receives this, the router 641 SHOULD attempt to connect to any more preferred caches in its cache 642 list. If there are no more preferred caches it MUST issue a Reset 643 Query and get an entire new load from the cache. 645 6.4. Cache has No Data Available 647 Cache Router 648 ~ ~ 649 | <----- Serial Query ------ | R requests data 650 | ---- Error Report PDU ----> | C cannot supply update 651 ~ ~ 653 Cache Router 654 ~ ~ 655 | <----- Reset Query ------- | R requests data 656 | ---- Error Report PDU ----> | C cannot supply update 657 ~ ~ 659 The cache may respond to either a Serial Query or a Reset Query 660 informing the router that the cache cannot supply any update at all. 661 The most likely cause is that the cache has lost state, perhaps due 662 to a restart, and has not yet recovered. While it is possible that a 663 cache might go into such a state without dropping any of its active 664 sessions, a router is more likely to see this behavior when it 665 initially connects and issues a Reset Query while the cache is still 666 rebuilding its database. 668 When a router receives this kind of error, the router SHOULD attempt 669 to connect to any other caches in its cache list, in preference 670 order. If no other caches are available, the router MUST issue 671 periodic Reset Queries until it gets a new usable load from the 672 cache. 674 7. Transport 676 The transport layer session between a router and a cache carries the 677 binary Protocol Data Units (PDUs) in a persistent session. 679 To prevent cache spoofing and DoS attacks by illegitimate routers, it 680 is highly desirable that the router and the cache are authenticated 681 to each other. Integrity protection for payloads is also desirable 682 to protect against monkey in the middle attacks. Unfortunately, 683 there is no protocol to do so on all currently used platforms. 684 Therefore, as of this document, there is no mandatory to implement 685 transport which provides authentication and integrity protection. 687 It is expected that, when TCP-AO [RFC5925]is available on all 688 platforms deployed by operators, it will become the mandatory to 689 implement transport. 691 Caches and routers MUST implement unprotected transport over TCP 692 using a port, RPKI-Rtr, to be assigned, see Section 12. Operators 693 SHOULD use procedural means, ACLs, ... to reduce the exposure to 694 authentication issues. 696 If available to the operator, caches and routers SHOULD use one of 697 the following more protected protocols. 699 Caches and routers SHOULD use TCP AO transport [RFC5925] over the 700 RPKI-Rtr port. 702 Caches and routers MAY use SSH transport [RFC4252] using using a the 703 normal SSH port. For an example, see Section 7.1. 705 Caches and routers MAY use TCP MD5 transport [RFC2385] using the 706 RPKI-Rtr port. 708 Caches and routers MAY use IPsec transport [RFC4301] using the RPKI- 709 Rtr port. 711 Caches and routers MAY use TLS transport [RFC5246] using using a 712 port, RPKI-Rtr TLS, to be assigned, see Section 12. 714 7.1. SSH Transport 716 To run over SSH, the client router first establishes an SSH transport 717 connection using the SSH transport protocol, and the client and 718 server exchange keys for message integrity and encryption. The 719 client then invokes the "ssh-userauth" service to authenticate the 720 application, as described in the SSH authentication protocol RFC 4252 721 [RFC4252]. Once the application has been successfully authenticated, 722 the client invokes the "ssh-connection" service, also known as the 723 SSH connection protocol. 725 After the ssh-connection service is established, the client opens a 726 channel of type "session", which results in an SSH session. 728 Once the SSH session has been established, the application invokes 729 the application transport as an SSH subsystem called "rpki-rtr". 730 Subsystem support is a feature of SSH version 2 (SSHv2) and is not 731 included in SSHv1. Running this protocol as an SSH subsystem avoids 732 the need for the application to recognize shell prompts or skip over 733 extraneous information, such as a system message that is sent at 734 shell start-up. 736 It is assumed that the router and cache have exchanged keys out of 737 band by some reasonably secured means. 739 Cache servers supporting SSH transport MUST accept RSA and DSA 740 authentication, and SHOULD accept ECDSA authentication. User 741 authentication MUST be supported; host authentication MAY be 742 supported. Implementations MAY support password authentication. 743 Client routers SHOULD verify the public key of the cache, to avoid 744 monkey-in-the-middle attacks. 746 7.2. TLS Transport 748 Client routers using TLS transport MUST use client-side certificates 749 for authentication. While in principle any type of certificate and 750 certificate authority may be used, in general cache operators will 751 generally wish to create their own small-scale CA and issue 752 certificates to each authorized router. This simplifies credential 753 roll-over; any unrevoked, unexpired certificate from the proper CA 754 may be used. If such certificates are used, the CN field [RFC5280] 755 MUST be used to denote the router's identity. 757 Clients SHOULD verify the cache's certificate as well, to avoid 758 monkey-in-the-middle attacks. 760 7.3. TCP MD5 Transport 762 If TCP-MD5 is used, implementations MUST support key lengths of at 763 least 80 printable ASCII bytes, per section 4.5 of [RFC2385]. 764 Implementations MUST also support hexadecimal sequences of at least 765 32 characters, i.e., 128 bits. 767 Key rollover with TCP-MD5 is problematic. Cache servers SHOULD 768 support [RFC4808]. 770 7.4. TCP-AO Transport 772 Implementations MUST support key lengths of at least 80 printable 773 ASCII bytes. Implementations MUST also support hexadecimal sequences 774 of at least 32 characters, i.e., 128 bits. MAC lengths of at least 775 96 bits MUST be supported, per section 5.3 of [RFC5925]. 777 The cryptographic algorithms and associcated parameters described in 778 [RFC5926] MUST be supported. 780 8. Router-Cache Set-Up 782 A cache has the public authentication data for each router it is 783 configured to support. 785 A router may be configured to peer with a selection of caches, and a 786 cache may be configured to support a selection of routers. Each must 787 have the name of, and authentication data for, each peer. In 788 addition, in a router, this list has a non-unique preference value 789 for each server in order of preference. This preference merely 790 denotes proximity, not trust, preferred belief, etc. The client 791 router attempts to establish a session with each potential serving 792 cache in preference order, and then starts to load data from the most 793 preferred cache to which it can connect and authenticate. The 794 router's list of caches has the following elements: 796 Preference: An ordinal denoting the router's preference to connect 797 to that cache, the lower the value the more preferred. 799 Name: The IP Address or fully qualified domain name of the cache. 801 Key: The public ssh key of the cache. 803 MyKey: The private ssh key of this client. 805 Due to the distributed nature of the RPKI, caches simply can not be 806 rigorously synchronous. A client may hold data from multiple caches, 807 but MUST keep the data marked as to source, as later updates MUST 808 affect the correct data. 810 Just as there may be more than one covering ROA from a single cache, 811 there may be multiple covering ROAs from multiple caches. The 812 results are as described in [I-D.ietf-sidr-pfx-validate]. 814 If data from multiple caches are held, implementations MUST NOT 815 distinguish between data sources when performing validation. 817 When a more preferred cache becomes available, if resources allow, it 818 would be prudent for the client to start fetching from that cache. 820 The client SHOULD attempt to maintain at least one set of data, 821 regardless of whether it has chosen a different cache or established 822 a new connection to the previous cache. 824 A client MAY drop the data from a particular cache when it is fully 825 in synch with one or more other caches. 827 A client SHOULD delete the data from a cache when it has been unable 828 to refresh from that cache for a configurable timer value. The 829 default for that value is twice the polling period for that cache. 831 If a client loses connectivity to a cache it is using, or otherwise 832 decides to switch to a new cache, it SHOULD retain the data from the 833 previous cache until it has a full set of data from one or more other 834 caches. Note that this may already be true at the point of 835 connection loss if the client has connections to more than one cache. 837 9. Deployment Scenarios 839 For illustration, we present three likely deployment scenarios. 841 Small End Site: The small multi-homed end site may wish to outsource 842 the RPKI cache to one or more of their upstream ISPs. They would 843 exchange authentication material with the ISP using some out of 844 band mechanism, and their router(s) would connect to one or more 845 up-streams' caches. The ISPs would likely deploy caches intended 846 for customer use separately from the caches with which their own 847 BGP speakers peer. 849 Large End Site: A larger multi-homed end site might run one or more 850 caches, arranging them in a hierarchy of client caches, each 851 fetching from a serving cache which is closer to the global RPKI. 852 They might configure fall-back peerings to up-stream ISP caches. 854 ISP Backbone: A large ISP would likely have one or more redundant 855 caches in each major PoP, and these caches would fetch from each 856 other in an ISP-dependent topology so as not to place undue load 857 on the global RPKI publication infrastructure. 859 Experience with large DNS cache deployments has shown that complex 860 topologies are ill-advised as it is easy to make errors in the graph, 861 e.g. not maintaining a loop-free condition. 863 Of course, these are illustrations and there are other possible 864 deployment strategies. It is expected that minimizing load on the 865 global RPKI servers will be a major consideration. 867 To keep load on global RPKI services from unnecessary peaks, it is 868 recommended that primary caches which load from the distributed 869 global RPKI not do so all at the same times, e.g. on the hour. 870 Choose a random time, perhaps the ISP's AS number modulo 60 and 871 jitter the inter-fetch timing. 873 10. Error Codes 875 This section contains a preliminary list of error codes. The authors 876 expect additions to this section during development of the initial 877 implementations. Errors which are considered fatal SHOULD cause the 878 session to be dropped. 880 0: Corrupt Data (fatal): The receiver believes the received PDU to 881 be corrupt in a manner not specified by other error codes. 883 1: Internal Error (fatal): The party reporting the error experienced 884 some kind of internal error unrelated to protocol operation (ran 885 out of memory, a coding assertion failed, et cetera). 887 2: No Data Available: The cache believes itself to be in good 888 working order, but is unable to answer either a Serial Query or a 889 Reset Query because it has no useful data available at this time. 890 This is likely to be a temporary error, and most likely indicates 891 that the cache has not yet completed pulling down an initial 892 current data set from the global RPKI system after some kind of 893 event that invalidated whatever data it might have previously held 894 (reboot, network partition, et cetera). 896 3: Invalid Request (fatal): The cache server believes the client's 897 request to be invalid. 899 4: Unsupported Protocol Version (fatal): The Protocol Version is not 900 known by the receiver of the PDU. 902 5: Unsupported PDU Type (fatal): The PDU Type is not known by the 903 receiver of the PDU. 905 6: Withdrawal of Unknown Record (fatal): The received PDU has Flag=0 906 but a record for the Prefix/PrefixLength/MaxLength triple does not 907 exist in the receiver's database. 909 7: Duplicate Announcement Received (fatal): The received PDU has an 910 identical {prefix, len, max-len, asn} tuple as a PDU which is 911 still active in the router. 913 11. Security Considerations 915 As this document describes a security protocol, many aspects of 916 security interest are described in the relevant sections. This 917 section points out issues which may not be obvious in other sections. 919 Cache Validation: In order for a collection of caches as described 920 in Section 9 to guarantee a consistent view, they need to be given 921 consistent trust anchors to use in their internal validation 922 process. Distribution of a consistent trust anchor is assumed to 923 be out of band. 925 Cache Peer Identification: The router initiates an ssh transport 926 session to a cache, which it identifies by either IP address or 927 fully qualified domain name. Be aware that a DNS or address 928 spoofing attack could make the correct cache unreachable. No 929 session would be established, as the authorization keys would not 930 match. 932 Transport Security: The RPKI relies on object, not server or 933 transport, trust. I.e. the IANA root trust anchor is distributed 934 to all caches through some out of band means, and can then be used 935 by each cache to validate certificates and ROAs all the way down 936 the tree. The inter-cache relationships are based on this object 937 security model, hence the inter-cache transport can be lightly 938 protected. 940 But this protocol document assumes that the routers can not do the 941 validation cryptography. Hence the last link, from cache to 942 router, is secured by server authentication and transport level 943 security. This is dangerous, as server authentication and 944 transport have very different threat models than object security. 946 So the strength of the trust relationship and the transport 947 between the router(s) and the cache(s) are critical. You're 948 betting your routing on this. 950 While we can not say the cache must be on the same LAN, if only 951 due to the issue of an enterprise wanting to off-load the cache 952 task to their upstream ISP(s), locality, trust, and control are 953 very critical issues here. The cache(s) really SHOULD be as 954 close, in the sense of controlled and protected (against DDoS, 955 MITM) transport, to the router(s) as possible. It also SHOULD be 956 topologically close so that a minimum of validated routing data 957 are needed to bootstrap a router's access to a cache. 959 The ssh identity of the cache server MUST be verified and 960 authenticated by the router client, and vice versa, before any 961 data are exchanged. 963 12. IANA Considerations 965 This document requests the IANA to assign TCP Port Numbers to the 966 RPKI-Router Protocol for the following, see Section 7: 968 RPKI-Rtr 969 RPKI-Rtr TLS 971 This document requests the IANA to create a registry for PDU types 0 972 to 255. The name of the registry should be rpki-rtr-pdu. The policy 973 for adding to the registry is RFC Required per [RFC5226], either 974 standards track or experimental. The initial entries should be as 975 follows: 977 0 - Serial Notify 978 1 - Serial Query 979 2 - Reset Query 980 3 - Cache Response 981 4 - IPv4 Prefix 982 6 - IPv6 Prefix 983 7 - End of Data 984 8 - Cache Reset 985 10 - Error Report 986 255 - Reserved 988 This document requests the IANA to create a registry for Error Codes 989 0 to 255. The name of the registry should be rpki-rtr-error. The 990 policy for adding to the registry is Expert Review per [RFC5226], 991 where the responsible IESG area director should appoint the Expert 992 Reviewer. The initial entries should be as follows: 994 0 - Corrupt Data 995 1 - Internal Error 996 2 - No Data Available 997 3 - Invalid Request 998 4 - Unsupported Protocol Version 999 5 - Unsupported PDU Type 1000 6 - Withdrawal of Unknown Record 1001 7 - Duplicate Announcement Received 1002 255 - Reserved 1004 This document requests the IANA to add an SSH Connection Protocol 1005 Subsystem Name, as defined in [RFC4250], of 'rpki-rtr'. 1007 13. Acknowledgments 1009 The authors wish to thank Steve Bellovin, Rex Fernando, Russ Housley, 1010 Pradosh Mohapatra, Keyur Patel, Sandy Murphy, Robert Raszuk, John 1011 Scudder, Ruediger Volk, and David Ward. Particular thanks go to 1012 Hannes Gredler for showing us the dangers of unnecessary fields. 1014 14. References 1016 14.1. Normative References 1018 [I-D.ietf-sidr-pfx-validate] 1019 Mohapatra, P., Scudder, J., Ward, D., Bush, R., and R. 1020 Austein, "BGP Prefix Origin Validation", 1021 draft-ietf-sidr-pfx-validate-01 (work in progress), 1022 February 2011. 1024 [RFC1982] Elz, R. and R. Bush, "Serial Number Arithmetic", RFC 1982, 1025 August 1996. 1027 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1028 Requirement Levels", BCP 14, RFC 2119, March 1997. 1030 [RFC2385] Heffernan, A., "Protection of BGP Sessions via the TCP MD5 1031 Signature Option", RFC 2385, August 1998. 1033 [RFC4250] Lehtinen, S. and C. Lonvick, "The Secure Shell (SSH) 1034 Protocol Assigned Numbers", RFC 4250, January 2006. 1036 [RFC4252] Ylonen, T. and C. Lonvick, "The Secure Shell (SSH) 1037 Authentication Protocol", RFC 4252, January 2006. 1039 [RFC4301] Kent, S. and K. Seo, "Security Architecture for the 1040 Internet Protocol", RFC 4301, December 2005. 1042 [RFC4808] Bellovin, S., "Key Change Strategies for TCP-MD5", 1043 RFC 4808, March 2007. 1045 [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an 1046 IANA Considerations Section in RFCs", BCP 26, RFC 5226, 1047 May 2008. 1049 [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security 1050 (TLS) Protocol Version 1.2", RFC 5246, August 2008. 1052 [RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S., 1053 Housley, R., and W. Polk, "Internet X.509 Public Key 1054 Infrastructure Certificate and Certificate Revocation List 1055 (CRL) Profile", RFC 5280, May 2008. 1057 [RFC5925] Touch, J., Mankin, A., and R. Bonica, "The TCP 1058 Authentication Option", RFC 5925, June 2010. 1060 [RFC5926] Lebovitz, G. and E. Rescorla, "Cryptographic Algorithms 1061 for the TCP Authentication Option (TCP-AO)", RFC 5926, 1062 June 2010. 1064 14.2. Informative References 1066 [I-D.ietf-sidr-arch] 1067 Lepinski, M. and S. Kent, "An Infrastructure to Support 1068 Secure Internet Routing", draft-ietf-sidr-arch-13 (work in 1069 progress), May 2011. 1071 [I-D.ietf-sidr-repos-struct] 1072 Huston, G., Loomans, R., and G. Michaelson, "A Profile for 1073 Resource Certificate Repository Structure", 1074 draft-ietf-sidr-repos-struct-08 (work in progress), 1075 June 2011. 1077 [RFC1996] Vixie, P., "A Mechanism for Prompt Notification of Zone 1078 Changes (DNS NOTIFY)", RFC 1996, August 1996. 1080 [RFC5781] Weiler, S., Ward, D., and R. Housley, "The rsync URI 1081 Scheme", RFC 5781, February 2010. 1083 Authors' Addresses 1085 Randy Bush 1086 Internet Initiative Japan 1087 5147 Crystal Springs 1088 Bainbridge Island, Washington 98110 1089 US 1091 Phone: +1 206 780 0431 x1 1092 Email: randy@psg.com 1094 Rob Austein 1095 Internet Systems Consortium 1096 950 Charter Street 1097 Redwood City, CA 94063 1098 USA 1100 Email: sra@isc.org