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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) ** Obsolete normative reference: RFC 6485 (Obsoleted by RFC 7935) ** Obsolete normative reference: RFC 6490 (Obsoleted by RFC 7730) Summary: 3 errors (**), 0 flaws (~~), 2 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group R. Gagliano 3 Internet-Draft Cisco Systems 4 Intended status: Standards Track S. Kent 5 Expires: July 11, 2013 BBN Technologies 6 S. Turner 7 IECA, Inc. 8 January 7, 2013 10 Algorithm Agility Procedure for RPKI. 11 draft-ietf-sidr-algorithm-agility-10 13 Abstract 15 This document specifies the process that Certification Authorities 16 (CAs) and Relying Parties (RPs) participating in the Resource Public 17 Key Infrastructure (RPKI) will need to follow to transition to a new 18 (and probably cryptographically stronger) algorithm set. The process 19 is expected to be completed in a time scale of several years. 20 Consequently, no emergency transition is specified. The transition 21 procedure defined in this document supports only a top-down migration 22 (parent migrates before children). 24 Status of this Memo 26 This Internet-Draft is submitted in full conformance with the 27 provisions of BCP 78 and BCP 79. 29 Internet-Drafts are working documents of the Internet Engineering 30 Task Force (IETF). Note that other groups may also distribute 31 working documents as Internet-Drafts. The list of current Internet- 32 Drafts is at http://datatracker.ietf.org/drafts/current/. 34 Internet-Drafts are draft documents valid for a maximum of six months 35 and may be updated, replaced, or obsoleted by other documents at any 36 time. It is inappropriate to use Internet-Drafts as reference 37 material or to cite them other than as "work in progress." 39 This Internet-Draft will expire on July 11, 2013. 41 Copyright Notice 43 Copyright (c) 2013 IETF Trust and the persons identified as the 44 document authors. All rights reserved. 46 This document is subject to BCP 78 and the IETF Trust's Legal 47 Provisions Relating to IETF Documents 48 (http://trustee.ietf.org/license-info) in effect on the date of 49 publication of this document. Please review these documents 50 carefully, as they describe your rights and restrictions with respect 51 to this document. Code Components extracted from this document must 52 include Simplified BSD License text as described in Section 4.e of 53 the Trust Legal Provisions and are provided without warranty as 54 described in the Simplified BSD License. 56 Table of Contents 58 1. Requirements notation . . . . . . . . . . . . . . . . . . . . 3 59 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 60 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 6 61 4. Key Rollover steps for algorithm migration . . . . . . . . . . 8 62 4.1. Milestones definition . . . . . . . . . . . . . . . . . . 8 63 4.2. Process overview . . . . . . . . . . . . . . . . . . . . . 8 64 4.3. Phase 0 . . . . . . . . . . . . . . . . . . . . . . . . . 10 65 4.3.1. Milestone 1 . . . . . . . . . . . . . . . . . . . . . 11 66 4.4. Phase 1 . . . . . . . . . . . . . . . . . . . . . . . . . 12 67 4.5. Phase 2 . . . . . . . . . . . . . . . . . . . . . . . . . 13 68 4.6. Phase 3 . . . . . . . . . . . . . . . . . . . . . . . . . 14 69 4.7. Phase 4 . . . . . . . . . . . . . . . . . . . . . . . . . 15 70 4.8. Return to Phase 0 . . . . . . . . . . . . . . . . . . . . 16 71 5. Multi Algorithm support in the RPKI provisioning protocol . . 17 72 6. Validation of multiple instance of signed products . . . . . . 18 73 7. Revocation . . . . . . . . . . . . . . . . . . . . . . . . . . 19 74 8. Key rollover . . . . . . . . . . . . . . . . . . . . . . . . . 20 75 9. Repository structure . . . . . . . . . . . . . . . . . . . . . 21 76 10. Deprecating an Algorithm Suite . . . . . . . . . . . . . . . . 22 77 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 24 78 12. Security Considerations . . . . . . . . . . . . . . . . . . . 25 79 13. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 26 80 14. Normative References . . . . . . . . . . . . . . . . . . . . . 27 81 Appendix A. Change Log . . . . . . . . . . . . . . . . . . . . . 28 82 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 31 84 1. Requirements notation 86 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 87 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", "NOT RECOMMENDED" and 88 "OPTIONAL" in this document are to be interpreted as described in 89 [RFC2119]. 91 2. Introduction 93 The RPKI must accommodate transitions between the public keys used by 94 CAs. Transitions of this sort are usually termed "key rollover". 95 Planned key rollover will occur at regular intervals throughout the 96 life of the RPKI, as each CA changes its public keys, in a non- 97 coordinated fashion. (By non-coordinated we mean that the time at 98 which each CA elects to change its keys is locally determined, not 99 coordinated across the RPKI.) Moreover, because a key change might 100 be necessitated by suspected private key compromise, one can never 101 assume coordination of these events among all of the CAs in the RPKI. 102 In an emergency key rollover, the old certificate is revoked and a 103 new certificate with a new key is issued. The mechanisms to perform 104 a key rollover in RPKI (either planned or in an emergency), while 105 maintaining the same algorithm suite, are covered in [RFC6489]. 107 This document describes the mechanism to perform a key rollover in 108 RPKI due to the migration to a new signature algorithm suite. A 109 signature algorithm suite encompasses both a signature algorithm 110 (with a specified key size range) and a one-way hash algorithm. It 111 is anticipated that the RPKI will require the adoption of updated key 112 sizes and/or different algorithm suites over time. This document 113 treats the adoption of a new hash algorithm while retaining the 114 current signature algorithm as equivalent to an algorithm migration, 115 and requires the CA to change its key. Migration to a new algorithm 116 suite will be required in order to maintain an acceptable level of 117 cryptographic security and protect the integrity of certificates, 118 CRLs and signed objects in the RPKI. All of the data structures in 119 the RPKI explicitly identify the signature and hash algorithms being 120 used. However, experience has demonstrated that the ability to 121 represent algorithm IDs is not sufficient to enable migration to new 122 algorithm suites (algorithm agility). One also must ensure that 123 protocols, infrastructure elements, and operational procedures also 124 accommodate the migration from one algorithm suite to another. 125 Algorithm migration is expected to be very infrequent and it will 126 require support of a "current" and "next" suite for a prolonged 127 interval, probably several years. 129 This document defines how entities in the RPKI execute (planned) CA 130 key rollover when the algorithm suite changes. The description 131 covers actions by CAs, repository operators, and RPs. It describes 132 the behavior required of both CAs and RPs to make such key changes 133 work in the RPKI context, including how the RPKI repository system is 134 used to support key rollover. 136 This document does not specify any algorithm suite per se. The RPKI 137 Certificate Policy (CP) [RFC6484] mandates the use of the algorithms 138 defined in [RFC6485] by CAs and RPs. When an algorithm transition is 139 initiated, [RFC6485] MUST be updated (as defined in Section 4.1 of 140 this document) redefining the required algorithm(s) for compliant 141 RPKI CAs and RPs under the CP. The CP will not change as a side 142 effect of algorithm transition (and thus the policy OID in RPKI 143 certificates will not change.) 145 For each algorithm transition, an additional document (the algorithm 146 transition timetable) MUST be published (as an IETF BCP) to define 147 the dates for each milestone defined in this document. It will 148 define dates for the phase transitions, consistent with the 149 descriptions provided in Section 4. It also will describe how the 150 RPKI community will measure the readiness of CAs and RPs to 151 transition to each phase. CAs publish certificates, CRLs, and other 152 signed objects under the new algorithm suite as the transition 153 progresses. This provides visibility into the deployment of the new 154 algorithm suite, enabling the community to evaluate deployment 155 progress. The transition procedure allows CAs to remove old 156 certificates, CRLs, and signed products, after the twilight date. 157 This provides an ability to observe and measure the withdrawal of the 158 old algorithm suite. Thus the phases defined in this document enable 159 the community to evaluate the progress of the transition. The 160 timetable document will also describe procedures to amend the 161 timetable if problems arise in implementing later phases of the 162 transition. It is RECOMMENDED that the timetable document be 163 developed by representatives of the RPKI community, e.g., IANA, 164 Internet Registries, and network operators. 166 3. Terminology 168 This document assumes that the reader is familiar with the terms and 169 concepts described in "Internet X.509 Public Key Infrastructure 170 Certificate and Certificate Revocation List (CRL) Profile" [RFC5280], 171 "X.509 Extensions for IP Addresses and AS Identifiers" [RFC3779], and 172 "A Profile for Resource Certificate Repository Structure" [RFC6481]. 173 Additional terms and conventions used in examples are provided below. 175 Algorithm migration: A planned transition from one signature and 176 hash algorithm to a new signature and hash algorithm. 178 Algorithm Suite A: The "current" algorithm suite used for hashing 179 and signing, in examples in this document 181 Algorithm Suite B: The "next" algorithm suite used for hashing and 182 signing, used in examples in this document 184 CA X: The CA that issued CA Y's certificate (i.e., CA Y's 185 parent), used in examples in this document. 187 CA Y: The non-leaf CA used in examples this document 189 CA Z: A CA that is a "child" of CA Y, used in examples this 190 document 192 Non-Leaf CA: A CA that issues certificates to other CAs is a non- 193 leaf CA. 195 Leaf CA: A leaf CA is a CA that issues only EE certs. 197 PoP (proof of possession): Execution of a protocol that demonstrates 198 to an issuer that a subject requesting a certificate 199 possesses the private key corresponding to the public key 200 in the certificate request submitted by the subject. 202 Signed Product Set (or Set or Product Set): A collection of 203 certificates, signed objects, a CRL and a manifest that 204 are associated by virtue of being verifiable under the 205 same parent CA certificate 207 Correspond: Two certificates, issued under different Algorithm Suites 208 correspond to one another if they are issued to the same 209 entity by the same CA and bind identical Internet Number 210 Resources (INRs) to that entity. Two CRLs correspond if 211 they are issued by the same CA and enumerate 212 corresponding certificates. Two signed objects (other 213 than manifests) correspond if they are verified using 214 corresponding EE certificates and they contain the same 215 encapsulated Context Info field. Two manifests 216 correspond if they encompass corresponding certificates, 217 ROAs, CRLs, and (other) signed objects (the term 218 "equivalent" is used synonymously when referring to such 219 RPKI signed products.) 221 ROA: Route Origination Autorization, as defined in [RFC6482]. 223 4. Key Rollover steps for algorithm migration 225 The "current" RPKI algorithm suite (Suite A) is defined in the RPKI 226 CP document, by reference to [RFC6485]. When a migration of the RPKI 227 algorithm suite is needed, the first step MUST be an update of 228 [RFC6485] to define the new algorithm suite. The algorithm 229 transition timeline document MUST also be published (as a BCP), to 230 inform the community of the dates selected for milestones in the 231 transition process, as described in Section 4.1. 233 4.1. Milestones definition 235 CA Ready Algorithm B Date: After this date, all (non-leaf) CAs MUST 236 be ready to process a request from a child CA to issue a 237 certificate under the Algorithm Suite B. All CAs 238 publishing an [RFC6490] Trust Anchor Locator (TAL) for 239 Algorithm Suite A, MUST also publish the correspondent 240 TAL for Algorithm Suite B. 242 CA Go Algorithm B Date: After this date, all CAs MUST have reissued 243 all of their signed product sets under the Algorithm 244 Suite B. 246 RP Ready Algorithm B Date: After this date, all RPs MUST be prepared 247 to process signed material issued under the Algorithm 248 Suite B. 250 Twilight Date: After this date, a CA MAY cease issuing signed 251 products under the Algorithm Suite A. Also, after this 252 date, a RP MAY cease to validate signed materials issued 253 under the Algorithm Suite A. 255 End Of Life (EOL) Date: After this date, the Algorithm Suite A MUST 256 be deprecated using the process in Section 10 and all 257 Algorithm Suite A TALs MUST be removed from their 258 publication points. 260 4.2. Process overview 262 The migration process described in this document involves a series of 263 steps that MUST be executed in chronological order by CAs and RPs. 264 The only milestone at which both CAs and RPs take action at the same 265 time is the EOL Date. Due to the decentralized nature of the RPKI 266 infrastructure, it is expected that an algorithm transition will span 267 several years. 269 In order to facilitate the transition, CAs will start issuing 270 certificates using the Algorithm B in a hierarchical top-down 271 fashion. In our example, CA Y will issue certificates using the 272 Algorithm Suite B only after CA X has started to do so (CA Y Ready 273 Algorithm B Date > CA X Ready Algorithm B Date). This ordered 274 transition avoids issuance of "mixed" suite CA certificates, e.g., a 275 CA certificate signed using Suite A, containing a key from Suite B. 276 In the RPKI, a CA MUST NOT sign a CA certificate carrying a subject 277 key that corresponds to an algorithm suite that differs from the one 278 used to sign the certificate. (X.509 accommodates such mixed 279 algorithm certificates, but this process avoids using that 280 capability.) A not top-down transition approach would require use of 281 such mixed mode certificates, and would lead to exponential growth of 282 the RPKI repository. Also, because the RPKI CP mandates Proof of 283 Possession (PoP) for certificate requests, it is not possible for a 284 CA to request a certificate for Algorithm Suite B, until its parent 285 CA supports that Suite. (See Section 5 for more details.) 287 The algorithm agility model described here does not prohibit a CA 288 from issuing an EE certificate with a subject public key from a 289 different algorithm suite, if that certificate is not used to verify 290 repository objects. This exception to the mixed algorithm suite 291 certificate rule is allowed because an EE certificate that is not 292 used to verify repository objects does not interfere with the ability 293 of RPs to download and verify repository content. As noted above, 294 every CA in the RPKI is required to perform a PoP check for the 295 subject public key when issuing a certificate. In general a subject 296 cannot assume that a CA is capable of supporting a different 297 algorithm. However, if the subject is closely affiliated with the 298 CA, it is reasonable to assume that there are ways for the subject to 299 know whether the CA can support a request to issue an EE certificate 300 containing a specific, different public key algorithm. This document 301 does not specify how a subject can determine whether a CA is capable 302 of issuing a mixed suite EE certificate, because it anticipates that 303 such certificates will be issued only in contexts where the subject 304 and CA are sufficiently closely affiliated (for example, an ISP 305 issuing certificates to devices that it manages). 307 The following figure gives an overview of the process: 309 Process for RPKI CAs: 311 Phase 0 Phase 1 Phase 2 Phase 4 Phase 0 312 -----------x---------x-------------------x--------x----------- 313 ^ ^ ^ ^ ^ 314 | | | | | 315 (1) (2) (3) (5) (6) 317 Process for RPKI RPs: 319 Phase 0 Phase 3 Phase 4 Phase 0 320 -------------------------------x---------x--------x----- 321 ^ ^ ^ ^ 322 | | | | 323 (1) (4) (5) (6) 325 (1) RPKI algorithm document is updated and the algorithm transition timeline document is issued 326 (2) CA Ready Algorithm B Date 327 (3) CA Go Algorithm B Date 328 (4) RP Ready Algorithm B Date 329 (5) Twilight Date 330 (6) End Of Live (EOL) Date 332 Each of these milestones is discussed in the next section when 333 describing each phase of the transition process. 335 Two situations have been identified that motivate pausing or rolling 336 back the transition process. The first situation arises if the RPKI 337 community is not ready to make the transition. For example, many CAs 338 might not be prepared to issue signed products under Suite B, or many 339 RPs might not be ready to process Suite B products. Under these 340 circumstances, the timetable MUST be reissued, postponing the date 341 for the phase in question, and pushing back the dates for later 342 phases. The other situation arises if, during the transition, 343 serious concerns arise about the security of the Suite B algorithms. 344 Such concerns would motivate terminating the transition and rolling 345 back signed products, i.e., reverting to Suite A. In this case the 346 timetable MUST be republished, and the RPKI algorithm document MUST 347 be superseded. The phase descriptions below allude to these two 348 situations, as appropriate. 350 4.3. Phase 0 352 Phase 0 is the steady state phase of the process; throughout this 353 phase, Algorithm Suite A is the only supported algorithm suite in 354 RPKI. This is also the steady state for the RPKI. 356 The following figure illustrates the format used to describe signed 357 objects in the repository. It reflects the algorithm suites in use, 358 and shows the relationship between three CAs (X, Y, and Z) that form 359 a chain. 361 During Phase 0, CAs X, Y and Z are required to generate signed 362 product sets using only the Algorithm Suite A. Also, RPs are required 363 to validate signed product sets issued using only Algorithm Suite A. 365 CA X-Certificate-Algorithm-Suite-A (Cert-XA) 366 | 367 |-> CA-Y-Certificate-Algorithm-Suite-A (Cert-YA) 368 |-> CA-Z-Certificate-Algorithm-Suite-A (Cert-ZA) 369 |-> CA-Z-CRL-Algorithm-Suite-A (CRL-ZA) 370 |-> CA-Z-Signed-Objects-Algorithm-Suite-A 371 |-> CA-Y-CRL-Algorithm-Suite-A (CRL-YA) 372 |-> CA-Y-Signed-Objects-Algorithm-Suite-A 373 |-> CA-X-CRL-Algorithm-Suite-A (CRL-XA) 374 |-> CA-X-Signed-Objects-Algorithm-Suite-A 376 Note: Cert-XA represent the certificate for CA X, that is signed 377 using the algorithm suite A. 379 4.3.1. Milestone 1 381 The first milestone initiates the migration process. It updates 382 [RFC6485] with the following definitions for the RPKI: 384 o Algorithm Suite A 386 o Algorithm Suite B 388 Additionally, the new algorithm transition timeline document MUST be 389 published with the following information: 391 o CA Ready Algorithm B Date 393 o CA Go Algorithm B Date 395 o RP Ready Algorithm B Date 397 o Twilight Date 399 o EOL Date 401 o Readiness metrics for CAs and RPs in each phase 403 Each date specified here is assumed at one minute after midnight, 404 UTC. No finer granularity time specification is required or 405 supported. 407 4.4. Phase 1 409 Phase 1 starts at the CA Ready Algorithm B Date. During Phase 1, all 410 (non-leaf) CAs MUST be ready to process a request from a child CA to 411 issue or revoke a certificate using the Algorithm Suite B. If it is 412 determined that a substantial number of CAs are not ready, the 413 algorithm transition timeline document MUST be reissued, as noted in 414 Section 4.2. However, CAs that are capable of issuing Suite B 415 certificates may continue to do so, if requested by their child CAs. 416 Since this phase does not require any RPs to process signed objects 417 under Suite B, and since Suite B product sets SHOULD be stored at 418 independent publication points, there is no adverse impact on RPs. 419 If the Suite B algorithm is deemed unsuitable, the algorithm 420 transition timeline and the algorithm specification documents MUST be 421 replaced, the Algorithm Suite B MUST be deprecated using the process 422 described in Section 10. 424 As the transition will happen using a (hierarchic) top-down model, a 425 child CA will be able to issue certificates using the Algorithm Suite 426 B only after its parent CA has issued its own. The RPKI provisioning 427 protocol can identify if a parent CA is capable of issuing 428 certificates using the Algorithm Suite B, and can identify the 429 corresponding algorithm suite in each Certificate Signing Request 430 (see Section 5). During much of this phase the Suite B product tree 431 will be incomplete, i.e., not all CAs will have issued products under 432 Suite B. Thus for production purposes, RPs MUST fetch and validate 433 only Suite A products. Suite B products should be fetched and 434 processed only for testing purposes. 436 The following figure shows the status of repository entries for the 437 three example CAs during this Phase. Two distinct certificate chains 438 are maintained and CA Z has not yet requested any material using the 439 Algorithm Suite B. 441 CA X-Certificate-Algorithm-Suite-A (Cert-XA) 442 | 443 |-> CA-Y-Certificate-Algorithm-Suite-A (Cert-YA) 444 |-> CA-Z-Certificate-Algorithm-Suite-A (Cert-ZA) 445 |-> CA-Z-CRL-Algorithm-Suite-A (CRL-ZA) 446 |-> CA-Z-Signed-Objects-Algorithm-Suite-A 447 |-> CA-Y-CRL-Algorithm-Suite-A (CRL-YA) 448 |-> CA-Y-Signed-Objects-Algorithm-Suite-A 449 |-> CA-X-CRL-Algorithm-Suite-A (CRL-XA) 450 |-> CA-X-Signed-Objects-Algorithm-Suite-A 452 CA X-Certificate-Algorithm-Suite-B (Cert-XB) 453 | 454 |-> CA-Y-Certificate-Algorithm-Suite-B (Cert-YB) 455 |-> CA-Y-CRL-Algorithm-Suite-B (CRL-YB) 456 |-> CA-Y-Signed-Objects-Algorithm-Suite-B 457 |-> CA-X-CRL-Algorithm-Suite-B (CRL-XB) 458 |-> CA-X-Signed-Objects-Algorithm-Suite-B 460 4.5. Phase 2 462 Phase 2 starts at the CA Go Algorithm B Date. At the start of this 463 phase, each signed product set MUST be available using both Algorithm 464 Suite A and Algorithm Suite B. Thus, prior to the start of this 465 phase, every CA MUST ensure that there is a Suite B product 466 corresponding to each Suite A product that the CA has issued. 467 Throughout this Phase, each CA MUST maintain this correspondence. 468 During this phase, RPs MUST be prepared to validate sets issued using 469 Algorithm Suite A and MAY be prepared to validate sets issued using 470 the Algorithm Suite B. 472 If it is determined that a substantial number of CAs are not ready, 473 the algorithm transition timeline document MUST be reissued, as noted 474 in Section 4.2. (Since the processing requirement for RPs here is a 475 MAY, if RPs have problems with Suite B products this does not require 476 pushing back the Phase 2 milestone, but it does motivate delaying the 477 start of Phase 3.) CAs that are capable of publishing products under 478 Suite B MAY continue to do so. Phase 2, like Phase 1, does not 479 require any RPs to process signed objects under Suite B. Also, Suite 480 B product SHOULD be stored at independent publication points, so 481 there is no adverse impact on RPs that are not prepared to process 482 suite B products (See Section 9 for additional details.) If the 483 Suite B algorithm is deemed unsuitable, the algorithm transition 484 timeline and the algorithm specification documents MUST be replaced 485 and the Algorithm Suite B MUST be deprecated using the process 486 described in Section 10. 488 It is RECOMMENDED that RPs that can process Algorithm Suite B fetch 489 and validate Suite B products. RPs that are not ready to process 490 Suite B products MUST continue to make use of Suite A products. An 491 RP that elects to validate signed product sets using both Algorithm 492 Suite A or Algorithm Suite B should expect the same results. If 493 there are discrepancies when evaluating corresponding signed product 494 sets, successful validation of either product set is acceptable. A 495 detailed analysis of the validation of multiple instances of signed 496 objects is included in Section 6. 498 The following figure shows the status of the repository entries for 499 the three example CAs throughout this phase, where all signed objects 500 are available using both algorithm suites. 502 CA X-Certificate-Algorithm-Suite-A (Cert-XA) 503 | 504 |-> CA-Y-Certificate-Algorithm-Suite-A (Cert-YA) 505 |-> CA-Z-Certificate-Algorithm-Suite-A (Cert-ZA) 506 |-> CA-Z-CRL-Algorithm-Suite-A (CRL-ZA) 507 |-> CA-Z-Signed-Objects-Algorithm-Suite-A 508 |-> CA-Y-CRL-Algorithm-Suite-A (CRL-YA) 509 |-> CA-Y-Signed-Objects-Algorithm-Suite-A 510 |-> CA-X-CRL-Algorithm-Suite-A (CRL-XA) 511 |-> CA-X-Signed-Objects-Algorithm-Suite-A 513 CA X-Certificate-Algorithm-Suite-B (Cert-XB) 514 | 515 |-> CA-Y-Certificate-Algorithm-Suite-B (Cert-YB) 516 |-> CA-Z-Certificate-Algorithm-Suite-B (Cert-ZB) 517 |-> CA-Z-CRL-Algorithm-Suite-B (CRL-ZB) 518 |-> CA-Z-Signed-Objects-Algorithm-Suite-B 519 |-> CA-Y-CRL-Algorithm-Suite-B (CRL-YB) 520 |-> CA-Y-Signed-Objects-Algorithm-Suite-B 521 |-> CA-X-CRL-Algorithm-Suite-B (CRL-XB) 522 |-> CA-X-Signed-Objects-Algorithm-Suite-B 524 4.6. Phase 3 526 Phase 3 starts at the RP Ready Algorithm B Date. During this phase, 527 all signed product sets are available using both algorithm suites and 528 all RPs MUST be able to validate them. (The correspondence between 529 Suite A and Suite B products was required for Phase 2, and maintained 530 throughout that Phase. The same requirements apply throughout this 531 Phase.) It is RECOMMENDED that, in preparation for Phase 4, RPs 532 retrieve and process Suite B product sets first, and treat them as 533 the preferred product sets for validation throughout this phase. 534 Thus an RP SHOULD try to validate the sets of signed products 535 retrieved from the Algorithm Suite B repository first. 537 If a substantial number of RPs are unable to process product sets 538 signed with Suite B, the algorithm transition timeline document MUST 539 be reissued, pushing back the date for this and later milestones, as 540 discussed in Section 4.2. Since the Suite B products SHOULD be 541 published at distinct publication points, RPs that cannot process 542 Suite B products can be expected to revert to the Suite A products 543 that still exist. If the Suite B algorithm is deemed unsuitable, the 544 algorithm transition timeline and the algorithm specification 545 documents MUST be replaced and the Algorithm Suite B MUST be 546 deprecated using the process described in Section 10. 548 There are no changes to the CA behavior throughout this phase. 550 4.7. Phase 4 552 Phase 4 starts at the Twilight Date. At that date, the Algorithm A 553 is labeled as "old" and the Algorithm B is labeled as "current". 555 During this phase, all signed product sets MUST be issued using 556 Algorithm Suite B and MAY be issued using Algorithm Suite A. All 557 signed products sets issued using Suite B MUST be published at their 558 corresponding publication points. Signed products sets issued using 559 Suite A might not be available at their corresponding publication 560 points. Every RP MUST validate signed product sets using Suite B. 561 RPs MAY validate signed product sets using Suite A. However, RPs 562 SHOULD NOT assume that the collection of Suite A product sets is 563 complete. Thus RPs SHOULD make use of only Suite B products sets. 564 (See Section 6 for further details.) 566 If it is determined that many RPs are not capable of processing the 567 new algorithm suite, the algorithm transition timeline document MUST 568 be reissued pushing back the date for this and the next milestone. 569 The document MUST require CA to not remove Suite A product sets if 570 this phase is delayed. If the Algorithm Suite B is deemed 571 unsuitable, the algorithm transition timeline, the algorithm 572 specification documents MUST be replaced, the Algorithm Suite B MUST 573 be deprecated using the process described in Section 10 and CAs MUST 574 NOT remove Suite A product sets. At this stage, RPs are still 575 capable of processing Suite A signed products, so the RPKI is still 576 viable. 578 The following figure describes a possible status for the repositories 579 of the example CAs. 581 CA X-Certificate-Algorithm-Suite-A (Cert-XA) 582 | 583 |-> CA-Y-Certificate-Algorithm-Suite-A (Cert-YA) 584 |-> CA-Y-CRL-Algorithm-Suite-A (CRL-YA) 585 |-> CA-Y-Signed-Objects-Algorithm-Suite-A 586 |-> CA-X-CRL-Algorithm-Suite-A (CRL-XA) 587 |-> CA-X-Signed-Objects-Algorithm-Suite-A 589 CA X-Certificate-Algorithm-Suite-B (Cert-XB) 590 | 591 |-> CA-Y-Certificate-Algorithm-Suite-B (Cert-YB) 592 |-> CA-Z-Certificate-Algorithm-Suite-B (Cert-ZB) 593 |-> CA-Z-CRL-Algorithm-Suite-A (CRL-ZB) 594 |-> CA-Z-Signed-Objects-Algorithm-Suite-B 595 |-> CA-Y-CRL-Algorithm-Suite-A (CRL-YB) 596 |-> CA-Y-Signed-Objects-Algorithm-Suite-B 597 |-> CA-X-CRL-Algorithm-Suite-A (CRL-XB) 598 |-> CA-X-Signed-Objects-Algorithm-Suite-B 600 4.8. Return to Phase 0 602 The EOL Date triggers the return to Phase 0 (steady state). At this 603 point, the old algorithm suite (Algorithm Suite A) MUST be deprecated 604 using the process described in Section 10. 606 This phase closes the loop as the new algorithm suite (Algorithm 607 Suite B) is the only required algorithm suite in RPKI. From this 608 point forward, this suite is referred to as Algorithm Suite A. 610 If it is determined that many RPs are not capable of processing the 611 new algorithm suite, the algorithm transition timeline document MUST 612 be reissued pushing back the date for this milestone. 614 5. Multi Algorithm support in the RPKI provisioning protocol 616 The migration described in this document is a top-down process, where 617 two synchronization issues need to be solved between child and parent 618 CAs: 620 o A child CA needs to identify which algorithm suites are supported 621 by its parent CA 623 o A child CA needs to signal which algorithm suite should be used by 624 its parent CA to sign a Certificate Signing Request (CSR) 626 The RPKI provisioning protocol [RFC6492] supports multiple algorithms 627 suites by implementing different resource classes for each suite. 628 Several different resource classes also may use the same algorithm 629 suite for different resource sets. 631 A child CA that wants to identify which algorithm suites are 632 supported by its parent CA MUST perform the following tasks: 634 1. Establish a provisioning protocol session with its parent CA 636 2. Perform a "list" command as described in Section 3.3.1 of 637 [RFC6492] 639 3. From the Payload in the "list response" resource class, extract 640 the "issuer's certificate" for each class. The Algorithm Suite 641 for each class will match the Algorithm Suite used to issue the 642 corresponding "issuer's certificate" (as specified in the 643 SubjectPublicKeyInfo field of that certificate) 645 A child CA that wants to specify an Algorithm Suite to its parent CA 646 (e.g., in a certificate request) MUST perform the following tasks: 648 1. Perform the tasks described above to identify the algorithm 649 suites supported by its parent CA, and the resource class 650 corresponding to each suite 652 2. Identify the corresponding resource class in the appropriate 653 provisioning protocol command (e.g. "issue" or "revoke") 655 Upon receipt of a certificate request from a child CA, a parent CA 656 will verify the PoP of the private key. If a child CA requests 657 issuing a certificate using an algorithm suite that does not match a 658 resource class, the PoP validation will fail and the request will not 659 be performed. 661 6. Validation of multiple instance of signed products 663 During Phases 1,2,3 and 4, two algorithm suites will be valid 664 simultaneously in RPKI. In this section, we describe the RP behavior 665 when validating corresponding signed products using different 666 algorithm suites. 668 During Phase 1 two (corresponding) instances MAY be available for 669 each signed product, one signed under Algorithm Suite A and one under 670 Algorithm Suite B. As noted in Section 4.4, in this phase there is a 671 preference for Suite A product sets. All products are available 672 under Suite A, while only some products may be available under Suite 673 B. For production purposes an RP MAY fetch and validate only Suite A 674 products. Suite B products SHOULD be fetched and validated only for 675 test purposes. When product sets exist under both Suites, they 676 should yield equivalent results, which facilitates testing. (It is 677 not possible to directly compare Suite A and Suite B product sets, as 678 certs, CRLs, and manifests will appear syntactically different. 679 However, the output of the process, i.e., the ROA payloads 680 (Autonomous System Number and address prefix data), SHOULD match, 681 modulo timing issues.) 683 During Phases 2 and 3 of this process, two (corresponding) instances 684 of all signed products MUST be available to RPs. As noted in Section 685 4.5, it is RECOMMENDED that Suite B capable RPs fetch and validate 686 Suite B products sets, during Phase 2. If an RP encounters 687 validation problems with the Suite B products, it SHOULD revert to 688 using Suite A products. RPs that are Suite B capable MAY fetch both 689 product sets and compare the results (e.g., ROA outputs) for testing. 691 In Phase 3 all RPs MUST be Suite B capable, and MUST fetch Suite B 692 product sets. If an RP encounters problems with Suite B product 693 sets, it can revert to Suite A products. RPs encountering such 694 problems SHOULD contact the relevant repository maintainers (e.g., 695 using the mechanism defined in [RFC6493] to report problems.) 697 During Phase 4 only Suite B product sets are required to be present 698 for all RPKI entities, as per Section 4.7. Thus RPs SHOULD retrieve 699 and validate only these product sets. Retrieval of Suite A products 700 sets may yield an incomplete set of signed products and is NOT 701 RECOMMENDED. 703 7. Revocation 705 The algorithm migration process mandates the maintenance of two 706 parallel but equivalent certification hierarchies during Phases 2 and 707 3 of the process. During these phases, a CA MUST revoke and request 708 revocation of certificates consistently under both algorithm Suites. 709 When not performing a key rollover operation (as described in Section 710 8), a CA requesting the revocation of its certificate during these 711 two phases MUST perform that request for both algorithm suites (A and 712 B). A non-leaf CA SHOULD NOT verify that its child CAs comply with 713 this requirement. Note that a CA MUST request revocation of its 714 certificate relative to a specific algorithm suite using the 715 mechanism described in Section 5 717 During Phase 1, a CA that revokes a certificate under Suite A SHOULD 718 revoke the corresponding certificate under Suite B, if that 719 certificate exists. During Phase 4, a CA that revokes a certificate 720 under Suite B SHOULD revoke the corresponding certificate under Suite 721 A, if that certificate exists. 723 During Phase 1, a CA may revoke certificates under Suite B without 724 revoking them under Suite A, since the Suite B products are for test 725 purposes. During Phase 4 a CA may revoke certificates issued under 726 Suite A without revoking them under Suite B, since Suite A products 727 are being deprecated. 729 8. Key rollover 731 Key rollover (without algorithm changes) is effected independently 732 for each algorithm suite and MUST follow the process described in 733 [RFC6489]. 735 9. Repository structure 737 The two parallel hierarchies that will exist during the transition 738 process SHOULD have independent publications points. The repository 739 structures for each algorithm suite are described in [RFC6481]. 741 10. Deprecating an Algorithm Suite 743 To deprecate an algorithm suite, the following process MUST be 744 executed by every CA in the RPKI: 746 1. Each CA MUST cease issuing certificates under the suite. This 747 means that any request for a (CA) certificate from a child will 748 be rejected, e.g., sending an error_response message with error 749 code:"request - no such resource class" as defined in [RFC6492]. 751 2. Each CA MUST cease generating signed products, except the CRL and 752 Manifest, under the deprecated Algorithm Suite. 754 3. Each CA MUST revoke the EE certificates for all signed products 755 that it has issued under the deprecated Algorithm Suite. The CA 756 SHOULD delete these products from its publication point, to avoid 757 burdening RPs with downloading and processing these products. 759 4. Each CA MUST revoke all CA certificates that it has issued under 760 the deprecated Algorithm Suite. 762 5. Each CA SHOULD remove all CA certificates that it has issued 763 under the deprecated Algorithm Suite. 765 6. Each CA that publishes a TAL under the deprecated Algorithm Suite 766 MUST removed it from the TAL's publication point. 768 7. Each CA SHOULD continue to maintain the publication point for the 769 deprecated Algorithm Suite, maintained at least until the CRL 770 nextUpdate. This publication point MUST contain only the CRL and 771 a Manifest for that publication point. This behavior provides a 772 window in which RPs may be able to become aware of the revoked 773 status of the signed products that have been deleted. 775 8. Each RP MUST remove any TALs that is has published under the 776 deprecated Algorithm Suite. 778 CAs in the RPKI hierarchy may become aware of the deprecation of the 779 algorithm suite at different times, and may execute the procedure 780 above in an asynchronous fashion relative to one another. Thus, for 781 example, a CA may request revocation of its CA certificate only to 782 learn that the certificate has already been revoked by the issuing 783 CA. The revocation of a CA certificate makes the CRL and manifest 784 issued under it incapable of validation. The asynchronous execution 785 of this procedure likely will result in transient "inconsistencies" 786 among the publication points associated with the deprecated algorithm 787 suite. However, these inconsistencies should yield "fail safe" 788 results, i.e., the objects signed under the deprecated suite should 789 be rejected by RPs. 791 11. IANA Considerations 793 No IANA requirements 795 12. Security Considerations 797 An algorithm transition in RPKI should be a very infrequent event and 798 it requires wide community consensus. The events that may lead to an 799 algorithm transition may be related to a weakness of the 800 cryptographic strength of the algorithm suite in use by RPKI, which 801 is normal to happen over time. The procedure described in this 802 document will take years to complete an algorithm transition. During 803 that time, the RPKI system will be vulnerable to any cryptographic 804 weakness that may have triggered this procedure (i.e. downgrade 805 attack). 807 This document does not describe an emergency mechanism for algorithm 808 migration. Due to the distributed nature of RPKI, and the very large 809 number of CAs and RPs, the authors do not believe it is feasible to 810 effect an emergency algorithm migration procedure. 812 If a CA does not complete its migration to the new algorithm suite as 813 described in this document (after the EOL of the "old" algorithm 814 suite), its signed product set will no longer be valid. 815 Consequently, the RPKI may, at the end of Phase 4, have a smaller 816 number of valid signed products than before starting the process. 817 Conversely, a RP that does not follow this process will lose the 818 ability to validate signed products issued under the new algorithm 819 suite. The resulting incomplete view of routing info from the RPKI 820 (as a result of a failure by CAs or RPs to complete the transition) 821 could degrade routing in the public Internet. 823 13. Acknowledgements 825 The authors would like to acknowledge the work of the SIDR working 826 group co-chairs (Sandra Murphy and Chris Morrow) as well as the 827 contributions given by Geoff Huston, Arturo Servin, Brian Weis, Terry 828 Manderson, Brian Dickson and Danny McPherson. 830 14. Normative References 832 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 833 Requirement Levels", BCP 14, RFC 2119, March 1997. 835 [RFC3779] Lynn, C., Kent, S., and K. Seo, "X.509 Extensions for IP 836 Addresses and AS Identifiers", RFC 3779, June 2004. 838 [RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S., 839 Housley, R., and W. Polk, "Internet X.509 Public Key 840 Infrastructure Certificate and Certificate Revocation List 841 (CRL) Profile", RFC 5280, May 2008. 843 [RFC6481] Huston, G., Loomans, R., and G. Michaelson, "A Profile for 844 Resource Certificate Repository Structure", RFC 6481, 845 February 2012. 847 [RFC6482] Lepinski, M., Kent, S., and D. Kong, "A Profile for Route 848 Origin Authorizations (ROAs)", RFC 6482, February 2012. 850 [RFC6484] Kent, S., Kong, D., Seo, K., and R. Watro, "Certificate 851 Policy (CP) for the Resource Public Key Infrastructure 852 (RPKI)", BCP 173, RFC 6484, February 2012. 854 [RFC6485] Huston, G., "The Profile for Algorithms and Key Sizes for 855 Use in the Resource Public Key Infrastructure (RPKI)", 856 RFC 6485, February 2012. 858 [RFC6489] Huston, G., Michaelson, G., and S. Kent, "Certification 859 Authority (CA) Key Rollover in the Resource Public Key 860 Infrastructure (RPKI)", BCP 174, RFC 6489, February 2012. 862 [RFC6490] Huston, G., Weiler, S., Michaelson, G., and S. Kent, 863 "Resource Public Key Infrastructure (RPKI) Trust Anchor 864 Locator", RFC 6490, February 2012. 866 [RFC6492] Huston, G., Loomans, R., Ellacott, B., and R. Austein, "A 867 Protocol for Provisioning Resource Certificates", 868 RFC 6492, February 2012. 870 [RFC6493] Bush, R., "The Resource Public Key Infrastructure (RPKI) 871 Ghostbusters Record", RFC 6493, February 2012. 873 Appendix A. Change Log 875 Note to the RFC Editor: Please remove this section before 876 publication. 878 From 09 to 10 880 1. GenArt Comments: Remove Algorithm C from process and replace a 881 couple of "will" with MUST when referring to issuing a new 882 document. 884 From 08 to 09 886 1. SecDIR comments and nits included 888 From 07 to 08 890 1. Typo in Section 10 892 2. Correct reference for RFC6493 894 From 06 to 07: 896 1. Added definition for "Correspond" 898 2. Added reference of correspondence between suites in phase 2 and 3 900 3. Small nit on the revocation definition. 902 From 05 to 06: 904 1. Added reference to published RFCs 906 2. Removed requirement on dates format 908 3. Changed revocation section to emphasize the differences between 909 phase 1,2,3 and 4. 911 4. Added Section 10: Deprecating an Algorithm Suite 913 5. Typos and editoral changes 915 From 04 to 05: 917 1. WGLC nits 919 From 03 to 04: 921 1. Added text for "roll-over" capability in each phase 923 2. Added the requirement for splitting the milestone 1 in two 924 documents: the update of the alg document and a new document 925 specifying the particular timelines 927 3. WGLC nits 929 From 02 to 03: 931 1. Explicitely named than "mixed" certificates are not allowed for 932 CA certs but may be possible for EE certs that are not used to 933 validate repository objects. 935 From 01 to 02: 937 1. Add reference to Multi-Objects validation 939 2. EOL Date is the only milestone that RP and CA take actions "at 940 the same time". 942 3. Updated references 944 4. Editorial 946 From 00 to 01: 948 1. Include text to clarify former Suites 950 2. Include text that documents that an RP that validates an object 951 signed with either suites in Phase 2 MUST consider it as valid 953 From individual submission to WG item: 955 1. Change form "laisez faire" to "top-down" 957 2. Included Multi Algorithm support in the RPKI provisioning 958 protocol 960 3. Included Validation of multiple instance of signed products 962 4. Included Revocations 964 5. Included Key rollover 966 6. Included Repository structure 967 7. Included Security Considerations 969 8. Included Acknowledgements 971 Authors' Addresses 973 Roque Gagliano 974 Cisco Systems 975 Avenue des Uttins 5 976 Rolle, 1180 977 Switzerland 979 Email: rogaglia@cisco.com 981 Stephen Kent 982 BBN Technologies 983 10 Moulton St. 984 Cambridge, MA 02138 985 USA 987 Email: kent@bbn.com 989 Sean Turner 990 IECA, Inc. 991 3057 Nutley Street, Suite 106 992 Fairfax, VA 22031 993 USA 995 Email: turners@ieca.com