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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 ACME Working Group Y. Sheffer 3 Internet-Draft Intuit 4 Intended status: Standards Track D. Lopez 5 Expires: April 15, 2020 O. Gonzalez de Dios 6 A. Pastor Perales 7 Telefonica I+D 8 T. Fossati 9 ARM 10 October 13, 2019 12 Support for Short-Term, Automatically-Renewed (STAR) Certificates in 13 Automated Certificate Management Environment (ACME) 14 draft-ietf-acme-star-10 16 Abstract 18 Public-key certificates need to be revoked when they are compromised, 19 that is, when the associated private key is exposed to an 20 unauthorized entity. However the revocation process is often 21 unreliable. An alternative to revocation is issuing a sequence of 22 certificates, each with a short validity period, and terminating this 23 sequence upon compromise. This memo proposes an ACME extension to 24 enable the issuance of short-term and automatically renewed (STAR) 25 X.509 certificates. 27 [RFC Editor: please remove before publication] 29 While the draft is being developed, the editor's version can be found 30 at https://github.com/yaronf/I-D/tree/master/STAR. 32 Status of This Memo 34 This Internet-Draft is submitted in full conformance with the 35 provisions of BCP 78 and BCP 79. 37 Internet-Drafts are working documents of the Internet Engineering 38 Task Force (IETF). Note that other groups may also distribute 39 working documents as Internet-Drafts. The list of current Internet- 40 Drafts is at https://datatracker.ietf.org/drafts/current/. 42 Internet-Drafts are draft documents valid for a maximum of six months 43 and may be updated, replaced, or obsoleted by other documents at any 44 time. It is inappropriate to use Internet-Drafts as reference 45 material or to cite them other than as "work in progress." 47 This Internet-Draft will expire on April 15, 2020. 49 Copyright Notice 51 Copyright (c) 2019 IETF Trust and the persons identified as the 52 document authors. All rights reserved. 54 This document is subject to BCP 78 and the IETF Trust's Legal 55 Provisions Relating to IETF Documents 56 (https://trustee.ietf.org/license-info) in effect on the date of 57 publication of this document. Please review these documents 58 carefully, as they describe your rights and restrictions with respect 59 to this document. Code Components extracted from this document must 60 include Simplified BSD License text as described in Section 4.e of 61 the Trust Legal Provisions and are provided without warranty as 62 described in the Simplified BSD License. 64 Table of Contents 66 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 67 1.1. Name Delegation Use Case . . . . . . . . . . . . . . . . 4 68 1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4 69 1.3. Conventions used in this document . . . . . . . . . . . . 4 70 2. Protocol Flow . . . . . . . . . . . . . . . . . . . . . . . . 5 71 2.1. Bootstrap . . . . . . . . . . . . . . . . . . . . . . . . 5 72 2.2. Refresh . . . . . . . . . . . . . . . . . . . . . . . . . 5 73 2.3. Termination . . . . . . . . . . . . . . . . . . . . . . . 6 74 3. Protocol Details . . . . . . . . . . . . . . . . . . . . . . 7 75 3.1. ACME Extensions . . . . . . . . . . . . . . . . . . . . . 7 76 3.1.1. Extending the Order Resource . . . . . . . . . . . . 7 77 3.1.2. Canceling an Auto-renewal Order . . . . . . . . . . . 8 78 3.2. Capability Discovery . . . . . . . . . . . . . . . . . . 10 79 3.3. Fetching the Certificates . . . . . . . . . . . . . . . . 11 80 3.4. Negotiating an unauthenticated GET . . . . . . . . . . . 13 81 3.5. Computing notBefore and notAfter of STAR Certificates . . 14 82 3.5.1. Example . . . . . . . . . . . . . . . . . . . . . . . 15 83 4. Operational Considerations . . . . . . . . . . . . . . . . . 15 84 4.1. The Meaning of "Short Term" and the Impact of Skewed 85 Clocks . . . . . . . . . . . . . . . . . . . . . . . . . 15 86 4.2. Impact on Certificate Transparency (CT) Logs . . . . . . 16 87 4.3. HTTP Caching and Dependability . . . . . . . . . . . . . 16 88 5. Implementation Status . . . . . . . . . . . . . . . . . . . . 17 89 5.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . 17 90 5.1.1. ACME Server with STAR extension . . . . . . . . . . . 18 91 5.1.2. STAR Proxy . . . . . . . . . . . . . . . . . . . . . 18 92 5.2. Level of Maturity . . . . . . . . . . . . . . . . . . . . 18 93 5.3. Coverage . . . . . . . . . . . . . . . . . . . . . . . . 18 94 5.4. Version Compatibility . . . . . . . . . . . . . . . . . . 19 95 5.5. Licensing . . . . . . . . . . . . . . . . . . . . . . . . 19 96 5.6. Implementation experience . . . . . . . . . . . . . . . . 19 97 5.7. Contact Information . . . . . . . . . . . . . . . . . . . 19 98 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19 99 6.1. New Registries . . . . . . . . . . . . . . . . . . . . . 19 100 6.2. New Error Types . . . . . . . . . . . . . . . . . . . . . 20 101 6.3. New fields in Order Objects . . . . . . . . . . . . . . . 20 102 6.4. Fields in the "auto-renewal" Object within an Order 103 Object . . . . . . . . . . . . . . . . . . . . . . . . . 21 104 6.5. New fields in the "meta" Object within a Directory Object 21 105 6.6. Fields in the "auto-renewal" Object within a Directory 106 Metadata Object . . . . . . . . . . . . . . . . . . . . . 22 107 6.7. Cert-Not-Before and Cert-Not-After HTTP Headers . . . . . 22 108 7. Security Considerations . . . . . . . . . . . . . . . . . . . 22 109 7.1. No revocation . . . . . . . . . . . . . . . . . . . . . . 22 110 7.2. Denial of Service Considerations . . . . . . . . . . . . 23 111 7.3. Privacy Considerations . . . . . . . . . . . . . . . . . 24 112 8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 24 113 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 24 114 9.1. Normative References . . . . . . . . . . . . . . . . . . 24 115 9.2. Informative References . . . . . . . . . . . . . . . . . 25 116 Appendix A. Document History . . . . . . . . . . . . . . . . . . 27 117 A.1. draft-ietf-acme-star-10 . . . . . . . . . . . . . . . . . 27 118 A.2. draft-ietf-acme-star-09 . . . . . . . . . . . . . . . . . 27 119 A.3. draft-ietf-acme-star-08 . . . . . . . . . . . . . . . . . 27 120 A.4. draft-ietf-acme-star-07 . . . . . . . . . . . . . . . . . 27 121 A.5. draft-ietf-acme-star-06 . . . . . . . . . . . . . . . . . 27 122 A.6. draft-ietf-acme-star-05 . . . . . . . . . . . . . . . . . 27 123 A.7. draft-ietf-acme-star-04 . . . . . . . . . . . . . . . . . 28 124 A.8. draft-ietf-acme-star-03 . . . . . . . . . . . . . . . . . 28 125 A.9. draft-ietf-acme-star-02 . . . . . . . . . . . . . . . . . 28 126 A.10. draft-ietf-acme-star-01 . . . . . . . . . . . . . . . . . 28 127 A.11. draft-ietf-acme-star-00 . . . . . . . . . . . . . . . . . 28 128 A.12. draft-sheffer-acme-star-02 . . . . . . . . . . . . . . . 28 129 A.13. draft-sheffer-acme-star-01 . . . . . . . . . . . . . . . 29 130 A.14. draft-sheffer-acme-star-00 . . . . . . . . . . . . . . . 29 131 A.15. draft-sheffer-acme-star-lurk-00 . . . . . . . . . . . . . 29 132 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 29 134 1. Introduction 136 The ACME protocol [RFC8555] automates the process of issuing a 137 certificate to a named entity (an Identifier Owner or IdO). 138 Typically, but not always, the identifier is a domain name. 140 If the IdO wishes to obtain a string of short-term certificates 141 originating from the same private key (see [Topalovic] about why 142 using short-lived certificates might be preferable to explicit 143 revocation), she must go through the whole ACME protocol each time a 144 new short-term certificate is needed - e.g., every 2-3 days. If done 145 this way, the process would involve frequent interactions between the 146 registration function of the ACME Certification Authority (CA) and 147 the identity provider infrastructure (e.g.: DNS, web servers), 148 therefore making the issuance of short-term certificates exceedingly 149 dependent on the reliability of both. 151 This document presents an extension of the ACME protocol that 152 optimizes this process by making short-term certificates first class 153 objects in the ACME ecosystem. Once the Order for a string of short- 154 term certificates is accepted, the CA is responsible for publishing 155 the next certificate at an agreed upon URL before the previous one 156 expires. The IdO can terminate the automatic renewal before the 157 negotiated deadline, if needed - e.g., on key compromise. 159 For a more generic treatment of STAR certificates, readers are 160 referred to [I-D.nir-saag-star]. 162 1.1. Name Delegation Use Case 164 The proposed mechanism can be used as a building block of an 165 efficient name-delegation protocol, for example one that exists 166 between a CDN or a cloud provider and its customers 167 [I-D.ietf-acme-star-delegation]. At any time, the service customer 168 (i.e., the IdO) can terminate the delegation by simply instructing 169 the CA to stop the automatic renewal and letting the currently active 170 certificate expire shortly thereafter. 172 Note that in the name delegation use case the delegated entity needs 173 to access the auto-renewed certificate without being in possession of 174 the ACME account key that was used for initiating the STAR issuance. 175 This leads to the optional use of unauthenticated GET in this 176 protocol (Section 3.4). 178 1.2. Terminology 180 IdO Identifier Owner, the owner of an identifier, e.g.: a domain 181 name, a telephone number. 182 STAR Short-Term and Automatically Renewed X.509 certificates. 184 1.3. Conventions used in this document 186 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 187 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 188 "OPTIONAL" in this document are to be interpreted as described in 189 BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all 190 capitals, as shown here. 192 2. Protocol Flow 194 The following subsections describe the three main phases of the 195 protocol: 197 o Bootstrap: the IdO asks an ACME CA to create a short-term and 198 automatically-renewed (STAR) certificate (Section 2.1); 199 o Auto-renewal: the ACME CA periodically re-issues the short-term 200 certificate and posts it to the star-certificate URL 201 (Section 2.2); 202 o Termination: the IdO requests the ACME CA to discontinue the 203 automatic renewal of the certificate (Section 2.3). 205 2.1. Bootstrap 207 The IdO, in its role as an ACME client, requests the CA to issue a 208 STAR certificate, i.e., one that: 210 o Has a short validity, e.g., 24 to 72 hours. Note that the exact 211 definition of "short" depends on the use case; 212 o Is automatically renewed by the CA for a certain period of time; 213 o Is downloadable from a (highly available) location. 215 Other than that, the ACME protocol flows as usual between IdO and CA. 216 In particular, IdO is responsible for satisfying the requested ACME 217 challenges until the CA is willing to issue the requested 218 certificate. Per normal ACME processing, the IdO is given back an 219 Order resource associated with the STAR certificate to be used in 220 subsequent interaction with the CA (e.g., if the certificate needs to 221 be terminated.) 223 The bootstrap phase ends when the ACME CA updates the Order resource 224 to include the URL for the issued STAR certificate. 226 2.2. Refresh 228 The CA issues the initial certificate after the authorization 229 completes successfully. It then automatically re-issues the 230 certificate using the same CSR (and therefore the same identifier and 231 public key) before the previous one expires, and publishes it to the 232 URL that was returned to the IdO at the end of the bootstrap phase. 233 The certificate user, which could be either the IdO itself or a 234 delegated third party, as described in 235 [I-D.ietf-acme-star-delegation], obtains the certificate 236 (Section 3.3) and uses it. 238 The refresh process (Figure 1) goes on until either: 240 o IdO explicitly terminates the automatic renewal (Section 2.3); or 241 o Automatic renewal expires. 243 Certificate ACME/STAR 244 User Server 245 | Retrieve cert | [...] 246 |---------------------->| | 247 | +------. / 248 | | | / 249 | | Automatic renewal : 250 | | | \ 251 | |<-----' \ 252 | Retrieve cert | | 253 |---------------------->| short validity period 254 | | | 255 | +------. / 256 | | | / 257 | | Automatic renewal : 258 | | | \ 259 | |<-----' \ 260 | Retrieve cert | | 261 |---------------------->| short validity period 262 | | | 263 | +------. / 264 | | | / 265 | | Automatic renewal : 266 | | | \ 267 | |<-----' \ 268 | | | 269 | [...] | [...] 271 Figure 1: Auto renewal 273 2.3. Termination 275 The IdO may request early termination of the STAR certificate by 276 sending a cancellation request to the Order resource, as described in 277 Section 3.1.2. After the CA receives and verifies the request, it 278 shall: 280 o Cancel the automatic renewal process for the STAR certificate; 281 o Change the certificate publication resource to return an error 282 indicating the termination of the issuance; 283 o Change the status of the Order to "canceled". 285 Note that it is not necessary to explicitly revoke the short-term 286 certificate. 288 Certificate ACME/STAR 289 User IdO Server 290 | | | 291 | | Cancel Order | 292 | +---------------------->| 293 | | +-------. 294 | | | | 295 | | | End auto renewal 296 | | | Remove cert link 297 | | | etc. 298 | | | | 299 | | Done |<------' 300 | |<----------------------+ 301 | | | 302 | | 303 | Retrieve cert | 304 +---------------------------------------------->| 305 | Error: autoRenewalCanceled | 306 |<----------------------------------------------+ 307 | | 309 Figure 2: Termination 311 3. Protocol Details 313 This section describes the protocol details, namely the extensions to 314 the ACME protocol required to issue STAR certificates. 316 3.1. ACME Extensions 318 This protocol extends the ACME protocol, to allow for automatically 319 renewed Orders. 321 3.1.1. Extending the Order Resource 323 The Order resource is extended with a new "auto-renewal" object that 324 MUST be present for STAR certificates. The "auto-renewal" object has 325 the following structure: 327 o start-date (optional, string): the earliest date of validity of 328 the first certificate issued, in [RFC3339] format. When omitted, 329 the start date is as soon as authorization is complete. 330 o end-date (required, string): the latest date of validity of the 331 last certificate issued, in [RFC3339] format. 332 o lifetime (required, integer): the maximum validity period of each 333 STAR certificate, an integer that denotes a number of seconds. 334 This is a nominal value which does not include any extra validity 335 time due to server or client adjustment (see below). 337 o lifetime-adjust (optional, integer): amount of "left pad" added to 338 each STAR certificate, an integer that denotes a number of 339 seconds. The default is 0. If present, the value of the 340 notBefore field that would otherwise appear in the STAR 341 certificates is pre-dated by the specified number of seconds. See 342 also Section 4.1 for why a client might want to use this control 343 and Section 3.5 for how the effective certificate lifetime is 344 computed. The value reflected by the server, together with the 345 value of the lifetime attribute, can be used by the client as a 346 hint to configure its polling timer. 347 o allow-certificate-get (optional, boolean): see Section 3.4. 349 These attributes are included in a POST message when creating the 350 Order, as part of the "payload" encoded object. They are returned 351 when the Order has been created, and the ACME server MAY adjust them 352 at will, according to its local policy (see also Section 3.2). 354 The optional notBefore and notAfter fields defined in Section 7.1.3 355 of [RFC8555] MUST NOT be present in a STAR Order. If they are 356 included, the server MUST return an error with status code 400 "Bad 357 Request" and type "malformedRequest". 359 Section 7.1.6 of [RFC8555] defines the following values for the Order 360 resource's status: "pending", "ready", "processing", "valid", and 361 "invalid". In the case of auto-renewal Orders, the status MUST be 362 "valid" as long as STAR certificates are being issued. We add a new 363 status value: "canceled", see Section 3.1.2. 365 A STAR certificate is by definition a dynamic resource, i.e., it 366 refers to an entity that varies over time. Instead of overloading 367 the semantics of the "certificate" attribute, this document defines a 368 new attribute "star-certificate" to be used instead of "certificate". 370 o star-certificate (optional, string): A URL for the (rolling) STAR 371 certificate that has been issued in response to this Order. 373 3.1.2. Canceling an Auto-renewal Order 375 An important property of the auto-renewal Order is that it can be 376 canceled by the IdO, with no need for certificate revocation. To 377 cancel the Order, the ACME client sends a POST to the Order URL as 378 shown in Figure 3. 380 POST /acme/order/ogfr8EcolOT HTTP/1.1 381 Host: example.org 382 Content-Type: application/jose+json 384 { 385 "protected": base64url({ 386 "alg": "ES256", 387 "kid": "https://example.com/acme/acct/gw06UNhKfOve", 388 "nonce": "Alc00Ap6Rt7GMkEl3L1JX5", 389 "url": "https://example.com/acme/order/ogfr8EcolOT" 390 }), 391 "payload": base64url({ 392 "status": "canceled" 393 }), 394 "signature": "g454e3hdBlkT4AEw...nKePnUyZTjGtXZ6H" 395 } 397 Figure 3: Canceling an Auto-renewal Order 399 After a successful cancellation, the server MUST NOT issue any 400 additional certificates for this Order. 402 When the Order is canceled, the server: 404 o MUST update the status of the Order resource to "canceled" and 405 MUST set an appropriate "expires" date; 406 o MUST respond with 403 (Forbidden) to any requests to the star- 407 certificate endpoint. The response SHOULD provide additional 408 information using a problem document [RFC7807] with type 409 "urn:ietf:params:acme:error:autoRenewalCanceled". 411 Issuing a cancellation for an Order that is not in "valid" state is 412 not allowed. A client MUST NOT send such a request, and a server 413 MUST return an error response with status code 400 (Bad Request) and 414 type "urn:ietf:params:acme:error:autoRenewalCancellationInvalid". 416 The state machine described in Section 7.1.6 of [RFC8555] is extended 417 as illustrated in Figure 4 (State Transitions for Order Objects). 419 pending --------------+ 420 | | 421 | All authz | 422 | "valid" | 423 V | 424 ready ---------------+ 425 | | 426 | Receive | 427 | finalize | 428 | request | 429 V | 430 processing ------------+ 431 | | 432 | First | 433 | certificate | Error or 434 | issued | Authorization failure 435 V V 436 valid invalid 437 | 438 | STAR 439 | Certificate 440 | canceled 441 V 442 canceled 444 Figure 4 446 Explicit certificate revocation using the revokeCert interface 447 (Section 7.6 of [RFC8555]) is not supported for STAR certificates. A 448 server receiving a revocation request for a STAR certificate MUST 449 return an error response with status code 403 (Forbidden) and type 450 "urn:ietf:params:acme:error:autoRenewalRevocationNotSupported". 452 3.2. Capability Discovery 454 In order to support the discovery of STAR capabilities, the "meta" 455 field inside the directory object defined in Section 9.7.6 of 456 [RFC8555] is extended with a new "auto-renewal" object. The "auto- 457 renewal" object MUST be present if the server supports STAR. Its 458 structure is as follows: 460 o min-lifetime (required, integer): minimum acceptable value for 461 auto-renewal lifetime, in seconds. 462 o max-duration (required, integer): maximum delta between the auto- 463 renewal end-date and start-date, in seconds. 464 o allow-certificate-get (optional, boolean): see Section 3.4. 466 An example directory object advertising STAR support with one day 467 min-lifetime and one year max-duration, and supporting certificate 468 fetching with an HTTP GET is shown in Figure 5. 470 { 471 "new-nonce": "https://example.com/acme/new-nonce", 472 "new-account": "https://example.com/acme/new-account", 473 "new-order": "https://example.com/acme/new-order", 474 "new-authz": "https://example.com/acme/new-authz", 475 "revoke-cert": "https://example.com/acme/revoke-cert", 476 "key-change": "https://example.com/acme/key-change", 477 "meta": { 478 "terms-of-service": "https://example.com/acme/terms/2017-5-30", 479 "website": "https://www.example.com/", 480 "caa-identities": ["example.com"], 481 "auto-renewal": { 482 "min-lifetime": 86400, 483 "max-duration": 31536000, 484 "allow-certificate-get": true 485 } 486 } 487 } 489 Figure 5: Directory object with STAR support 491 3.3. Fetching the Certificates 493 The certificate is fetched from the star-certificate endpoint with 494 POST-as-GET as per [RFC8555] Section 7.4.2, unless client and server 495 have successfully negotiated the "unauthenticated GET" option 496 described in Section 3.4. In such case, the client can simply issue 497 a GET to the star-certificate resource without authenticating itself 498 to the server as illustrated in Figure 6. 500 GET /acme/cert/mAt3xBGaobw HTTP/1.1 501 Host: example.org 502 Accept: application/pem-certificate-chain 504 HTTP/1.1 200 OK 505 Content-Type: application/pem-certificate-chain 506 Link: ;rel="index" 507 Cert-Not-Before: Thu, 3 Oct 2019 00:00:00 GMT 508 Cert-Not-After: Thu, 10 Oct 2019 00:00:00 GMT 510 -----BEGIN CERTIFICATE----- 511 [End-entity certificate contents] 512 -----END CERTIFICATE----- 513 -----BEGIN CERTIFICATE----- 514 [Issuer certificate contents] 515 -----END CERTIFICATE----- 516 -----BEGIN CERTIFICATE----- 517 [Other certificate contents] 518 -----END CERTIFICATE----- 520 Figure 6: Fetching a STAR certificate with unauthenticated GET 522 The Server SHOULD include the "Cert-Not-Before" and "Cert-Not-After" 523 HTTP header fields in the response. When they exist, they MUST be 524 equal to the respective fields inside the end-entity certificate. 525 Their format is "HTTP-date" as defined in Section 7.1.1.2 of 526 [RFC7231]. Their purpose is to enable client implementations that do 527 not parse the certificate. 529 Following are further clarifications regarding usage of these header 530 fields, as per [RFC7231] Sec. 8.3.1. All apply to both headers. 532 o This header field is a single value, not a list. 533 o The header field is used only in responses to GET, HEAD and POST- 534 as-GET requests, and only for MIME types that denote public key 535 certificates. 536 o Header field semantics are independent of context. 537 o The header field is not hop-by-hop. 538 o Intermediaries MAY insert or delete the value; 539 o If an intermediary inserts the value, it MUST ensure that the 540 newly added value matches the corresponding value in the 541 certificate. 542 o The header field is not appropriate for a Vary field. 543 o The header field is allowed within message trailers. 544 o The header field is not appropriate within redirects. 545 o The header field does not introduce additional security 546 considerations. It discloses in a simpler form information that 547 is already available inside the certificate. 549 To improve robustness, the next certificate MUST be made available by 550 the ACME CA at the URL pointed by "star-certificate" at the latest 551 halfway through the lifetime of the currently active certificate. It 552 is worth noting that this has an implication in case of cancellation: 553 in fact, from the time the next certificate is made available, the 554 cancellation is not completely effective until the "next" certificate 555 also expires. To avoid the client accidentally entering a broken 556 state, the notBefore of the "next" certificate MUST be set so that 557 the certificate is already valid when it is published at the "star- 558 certificate" URL. Note that the server might need to increase the 559 auto-renewal lifetime-adjust value to satisfy the latter requirement. 560 For a detailed description of the renewal scheduling logic, see 561 Section 3.5. For further rationale on the need for adjusting the 562 certificate validity, see Section 4.1. 564 The server MUST NOT issue any certificates for this Order with 565 notAfter after the auto-renewal end-date. 567 For expired Orders, the server MUST respond with 403 (Forbidden) to 568 any requests to the star-certificate endpoint. The response SHOULD 569 provide additional information using a problem document [RFC7807] 570 with type "urn:ietf:params:acme:error:autoRenewalExpired". Note that 571 the Order resource's state remains "valid", as per the base protocol. 573 3.4. Negotiating an unauthenticated GET 575 In order to enable the name delegation workflow defined in 576 [I-D.ietf-acme-star-delegation] as well as to increase the 577 reliability of the STAR ecosystem (see Section 4.3 for details), this 578 document defines a mechanism that allows a server to advertise 579 support for accessing star-certificate resources via unauthenticated 580 GET (in addition to POST-as-GET), and a client to enable this service 581 with per-Order granularity. 583 Specifically, a server states its availability to grant 584 unauthenticated access to a client's Order star-certificate by 585 setting the allow-certificate-get attribute to true in the auto- 586 renewal object of the meta field inside the Directory object: 588 o allow-certificate-get (optional, boolean): If this field is 589 present and set to true, the server allows GET (and HEAD) requests 590 to star-certificate URLs. 592 A client states its desire to access the issued star-certificate via 593 unauthenticated GET by adding an allow-certificate-get attribute to 594 the auto-renewal object of the payload of its newOrder request and 595 setting it to true. 597 o allow-certificate-get (optional, boolean): If this field is 598 present and set to true, the client requests the server to allow 599 unauthenticated GET (and HEAD) to the star-certificate associated 600 with this Order. 602 If the server accepts the request, it MUST reflect the attribute 603 setting in the resulting Order object. 605 Note that even when the use of unauthenticated GET has been agreed, 606 the server MUST also allow POST-as-GET requests to the star- 607 certificate resource. 609 3.5. Computing notBefore and notAfter of STAR Certificates 611 We define "nominal renewal date" as the point in time when a new 612 short-term certificate for a given STAR Order is due. Its cadence is 613 a multiple of the Order's auto-renewal lifetime that starts with the 614 issuance of the first short-term certificate and is upper-bounded by 615 the Order's auto-renewal end-date (Figure 7). 617 T - STAR Order's auto-renewal lifetime 618 end - STAR Order's auto-renewal end-date 619 nrd[i] - nominal renewal date of the i-th STAR certificate 621 .- T -. .- T -. .- T -. .__. 622 / \ / \ / \ / end 623 -----------o---------o---------o---------o----X-------> t 624 nrd[0] nrd[1] nrd[2] nrd[3] 626 Figure 7: Nominal Renewal Date 628 The rules to determine the notBefore and notAfter values of the i-th 629 STAR certificate are as follows: 631 notAfter = min(nrd[i] + T, end) 632 notBefore = nrd[i] - max(adjust_client, adjust_server) 634 Where "adjust_client" is the min between the auto-renewal lifetime- 635 adjust value ("la"), optionally supplied by the client, and the auto- 636 renewal lifetime of each short-term certificate ("T"); 637 "adjust_server" is the amount of padding added by the ACME server to 638 make sure that all certificates being published are valid at the time 639 of publication. The server padding is a fraction f of T (i.e., f * T 640 with .5 <= f < 1, see Section 3.3): 642 adjust_client = min(T, la) 643 adjust_server = f * T 645 Note that the ACME server MUST NOT set the notBefore of the first 646 STAR certificate to a date prior to the auto-renewal start-date. 648 3.5.1. Example 650 Given a server that intends to publish the next STAR certificate 651 halfway through the lifetime of the previous one, and a STAR Order 652 with the following attributes: 654 "auto-renewal": { 655 "start-date": "2019-01-10T00:00:00Z", 656 "end-date": "2019-01-20T00:00:00Z", 657 "lifetime": 345600, // 4 days 658 "lifetime-adjust": 259200 // 3 days 659 } 661 The amount of time that needs to be subtracted from each nominal 662 renewal date is 3 days - i.e., max(min(345600, 259200), 345600 * .5). 664 The notBefore and notAfter of each short-term certificate are: 666 +----------------------+----------------------+ 667 | notBefore | notAfter | 668 +----------------------+----------------------+ 669 | 2019-01-10T00:00:00Z | 2019-01-14T00:00:00Z | 670 | 2019-01-11T00:00:00Z | 2019-01-18T00:00:00Z | 671 | 2019-01-15T00:00:00Z | 2019-01-20T00:00:00Z | 672 +----------------------+----------------------+ 674 The value of the notBefore is also the time at which the client 675 should expect the new certificate to be available from the star- 676 certificate endpoint. 678 4. Operational Considerations 680 4.1. The Meaning of "Short Term" and the Impact of Skewed Clocks 682 "Short Term" is a relative concept, therefore trying to define a cut- 683 off point that works in all cases would be a useless exercise. In 684 practice, the expected lifetime of a STAR certificate will be counted 685 in minutes, hours or days, depending on different factors: the 686 underlying requirements for revocation, how much clock 687 synchronization is expected among relying parties and the issuing CA, 688 etc. 690 Nevertheless, this section attempts to provide reasonable suggestions 691 for the Web use case, informed by current operational and research 692 experience. 694 Acer et al. [Acer] find that one of the main causes of "HTTPS error" 695 warnings in browsers is misconfigured client clocks. In particular, 696 they observe that roughly 95% of the "severe" clock skews - the 6.7% 697 of clock-related breakage reports which account for clients that are 698 more than 24 hours behind - happen to be within 6-7 days. 700 In order to avoid these spurious warnings about a not (yet) valid 701 server certificate, site owners could use the auto-renewal lifetime- 702 adjust attribute to control the effective lifetime of their Web 703 facing certificates. The exact number depends on the percentage of 704 the "clock-skewed" population that the site owner expects to protect 705 - 5 days cover 97.3%, 7 days cover 99.6% - as well as the nominal 706 auto-renewal lifetime of the STAR Order. Note that exact choice is 707 also likely to depend on the kinds of client that is prevalent for a 708 given site or app - for example, Android and Mac OS clients are known 709 to behave better than Windows clients. These considerations are 710 clearly out of scope of the present document. 712 In terms of security, STAR certificates and certificates with OCSP 713 must-staple [RFC7633] can be considered roughly equivalent if the 714 STAR certificate's and the OCSP response's lifetimes are the same. 715 Given OCSP responses can be cached on average for 4 days [Stark], it 716 is RECOMMENDED that a STAR certificate that is used on the Web has an 717 "effective" lifetime (excluding any adjustment to account for clock 718 skews) no longer than 4 days. 720 4.2. Impact on Certificate Transparency (CT) Logs 722 Even in the highly unlikely case STAR becomes the only certificate 723 issuance model, discussion with the IETF TRANS Working Group and 724 Certificate Transparency (CT) logs implementers suggests that 725 existing CT Log Server implementations are capable of sustaining the 726 resulting 100-fold increase in ingestion rate. Additionally, such a 727 future, higher load could be managed with a variety of techniques 728 (e.g., sharding by modulo of certificate hash, using "smart" load- 729 balancing CT proxies, etc.). With regards to the increase in the log 730 size, current CT log growth is already being managed with schemes 731 like Chrome's Log Policy [OBrien] which allow Operators to define 732 their log life-cycle; and allowing the CAs, User Agents, Monitors, 733 and any other interested entities to build-in support for that life- 734 cycle ahead of time. 736 4.3. HTTP Caching and Dependability 738 When using authenticated POST-as-GET, the HTTPS endpoint from where 739 the STAR certificate is fetched can't be easily replicated by an on- 740 path HTTP cache. Reducing the caching properties of the protocol 741 makes STAR clients increasingly dependent on the ACME server 742 availability. This might be problematic given the relatively high 743 rate of client-server interactions in a STAR ecosystem and especially 744 when multiple endpoints (e.g., a high number of CDN edge nodes) end 745 up requesting the same certificate. Clients and servers should 746 consider using the mechanism described in Section 3.4 to mitigate the 747 risk. 749 When using unauthenticated GET to fetch the STAR certificate, the 750 server SHALL use the appropriate cache directives to set the 751 freshness lifetime of the response (Section 5.2 of [RFC7234]) such 752 that on-path caches will consider it stale before or at the time its 753 effective lifetime is due to expire. 755 5. Implementation Status 757 Note to RFC Editor: please remove this section before publication, 758 including the reference to [RFC7942] and 759 [I-D.sheffer-acme-star-request]. 761 This section records the status of known implementations of the 762 protocol defined by this specification at the time of posting of this 763 Internet-Draft, and is based on a proposal described in [RFC7942]. 764 The description of implementations in this section is intended to 765 assist the IETF in its decision processes in progressing drafts to 766 RFCs. Please note that the listing of any individual implementation 767 here does not imply endorsement by the IETF. Furthermore, no effort 768 has been spent to verify the information presented here that was 769 supplied by IETF contributors. This is not intended as, and must not 770 be construed to be, a catalog of available implementations or their 771 features. Readers are advised to note that other implementations may 772 exist. 774 According to [RFC7942], "this will allow reviewers and working groups 775 to assign due consideration to documents that have the benefit of 776 running code, which may serve as evidence of valuable experimentation 777 and feedback that have made the implemented protocols more mature. 778 It is up to the individual working groups to use this information as 779 they see fit". 781 5.1. Overview 783 The implementation is constructed around 3 elements: STAR Client for 784 the Name Delegation Client (NDC), STAR Proxy for IdO and ACME Server 785 for CA. The communication between them is over an IP network and the 786 HTTPS protocol. 788 The software of the implementation is available at: 789 https://github.com/mami-project/lurk 790 The following subsections offer a basic description, detailed 791 information is available in https://github.com/mami- 792 project/lurk/blob/master/proxySTAR_v2/README.md 794 5.1.1. ACME Server with STAR extension 796 This is a fork of the Let's Encrypt Boulder project that implements 797 an ACME compliant CA. It includes modifications to extend the ACME 798 protocol as it is specified in this draft, to support recurrent 799 Orders and cancelling Orders. 801 The implementation understands the new "recurrent" attributes as part 802 of the Certificate issuance in the POST request for a new resource. 803 An additional process "renewalManager.go" has been included in 804 parallel that reads the details of each recurrent request, 805 automatically produces a "cron" Linux based task that issues the 806 recurrent certificates, until the lifetime ends or the Order is 807 canceled. This process is also in charge of maintaining a fixed URI 808 to enable the NDC to download certificates, unlike Boulder's regular 809 process of producing a unique URI per certificate. 811 5.1.2. STAR Proxy 813 The STAR Proxy has a double role as ACME client and STAR Server. The 814 former is a fork of the EFF Certbot project that implements an ACME 815 compliant client with the STAR extension. The latter is a basic HTTP 816 REST API server. 818 The STAR Proxy understands the basic API request with a server. The 819 current implementation of the API is defined in draft-ietf-acme-star- 820 01. Registration or Order cancellation triggers the modified Certbot 821 client that requests, or cancels, the recurrent generation of 822 certificates using the STAR extension over ACME protocol. The URI 823 with the location of the recurrent certificate is delivered to the 824 STAR client as a response. 826 5.2. Level of Maturity 828 This is a prototype. 830 5.3. Coverage 832 A STAR Client is not included in this implementation, but done by 833 direct HTTP request with any open HTTP REST API tool. This is 834 expected to be covered as part of the [I-D.sheffer-acme-star-request] 835 implementation. 837 This implementation completely covers STAR Proxy and ACME Server with 838 STAR extension. 840 5.4. Version Compatibility 842 The implementation is compatible with version draft-ietf-acme-star- 843 01. The implementation is based on the Boulder and Certbot code 844 release from 7-Aug-2017. 846 5.5. Licensing 848 This implementation inherits the Boulder license (Mozilla Public 849 License 2.0) and Certbot license (Apache License Version 2.0 ). 851 5.6. Implementation experience 853 To prove the concept all the implementation has been done with a 854 self-signed CA, to avoid impact on real domains. To be able to do it 855 we use the FAKE_DNS property of Boulder and static /etc/hosts entries 856 with domains names. Nonetheless this implementation should run with 857 real domains. 859 Most of the implementation has been made to avoid deep changes inside 860 of Boulder or Certbot, for example, the recurrent certificates 861 issuance by the CA is based on an external process that auto- 862 configures the standard Linux "cron" daemon in the ACME CA server. 864 The reference setup recommended is one physical host with 3 virtual 865 machines, one for each of the 3 components (client, proxy and server) 866 and the connectivity based on host bridge. 868 Network security is not enabled (iptables default policies are 869 "accept" and all rules removed) in this implementation to simplify 870 and test the protocol. 872 5.7. Contact Information 874 See author details below. 876 6. IANA Considerations 878 [[RFC Editor: please replace XXXX below by the RFC number.]] 880 6.1. New Registries 882 This document requests that IANA create the following new registries: 884 o ACME Order Auto Renewal Fields (Section 6.4) 885 o ACME Directory Metadata Auto Renewal Fields (Section 6.6) 887 All of these registries are administered under a Specification 888 Required policy [RFC8126]. 890 6.2. New Error Types 892 This document adds the following entries to the ACME Error Type 893 registry: 895 +-----------------------------------+-------------------+-----------+ 896 | Type | Description | Reference | 897 +-----------------------------------+-------------------+-----------+ 898 | autoRenewalCanceled | The short-term | RFC XXXX | 899 | | certificate is no | | 900 | | longer available | | 901 | | because the auto- | | 902 | | renewal Order has | | 903 | | been explicitly | | 904 | | canceled by the | | 905 | | IdO | | 906 | autoRenewalExpired | The short-term | RFC XXXX | 907 | | certificate is no | | 908 | | longer available | | 909 | | because the auto- | | 910 | | renewal Order has | | 911 | | expired | | 912 | autoRenewalCancellationInvalid | A request to | RFC XXXX | 913 | | cancel a auto- | | 914 | | renewal Order | | 915 | | that is not in | | 916 | | state "valid" has | | 917 | | been received | | 918 | autoRenewalRevocationNotSupported | A request to | RFC XXXX | 919 | | revoke a auto- | | 920 | | renewal Order has | | 921 | | been received | | 922 +-----------------------------------+-------------------+-----------+ 924 6.3. New fields in Order Objects 926 This document adds the following entries to the ACME Order Object 927 Fields registry: 929 +------------------+------------+--------------+-----------+ 930 | Field Name | Field Type | Configurable | Reference | 931 +------------------+------------+--------------+-----------+ 932 | auto-renewal | object | true | RFC XXXX | 933 | star-certificate | string | false | RFC XXXX | 934 +------------------+------------+--------------+-----------+ 936 6.4. Fields in the "auto-renewal" Object within an Order Object 938 The "ACME Order Auto Renewal Fields" registry lists field names that 939 are defined for use in the JSON object included in the "auto-renewal" 940 field of an ACME order object. 942 Template: 944 o Field name: The string to be used as a field name in the JSON 945 object 946 o Field type: The type of value to be provided, e.g., string, 947 boolean, array of string 948 o Configurable: Boolean indicating whether the server should accept 949 values provided by the client 950 o Reference: Where this field is defined 952 Initial contents: The fields and descriptions defined in 953 Section 3.1.1. 955 +-----------------------+------------+--------------+-----------+ 956 | Field Name | Field Type | Configurable | Reference | 957 +-----------------------+------------+--------------+-----------+ 958 | start-date | string | true | RFC XXXX | 959 | end-date | string | true | RFC XXXX | 960 | lifetime | integer | true | RFC XXXX | 961 | lifetime-adjust | integer | true | RFC XXXX | 962 | allow-certificate-get | boolean | true | RFC XXXX | 963 +-----------------------+------------+--------------+-----------+ 965 6.5. New fields in the "meta" Object within a Directory Object 967 This document adds the following entry to the ACME Directory Metadata 968 Fields: 970 +--------------+------------+-----------+ 971 | Field Name | Field Type | Reference | 972 +--------------+------------+-----------+ 973 | auto-renewal | object | RFC XXXX | 974 +--------------+------------+-----------+ 976 6.6. Fields in the "auto-renewal" Object within a Directory Metadata 977 Object 979 The "ACME Directory Metadata Auto Renewal Fields" registry lists 980 field names that are defined for use in the JSON object included in 981 the "auto-renewal" field of an ACME directory "meta" object. 983 Template: 985 o Field name: The string to be used as a field name in the JSON 986 object 987 o Field type: The type of value to be provided, e.g., string, 988 boolean, array of string 989 o Reference: Where this field is defined 991 Initial contents: The fields and descriptions defined in Section 3.2. 993 +-----------------------+------------+-----------+ 994 | Field Name | Field Type | Reference | 995 +-----------------------+------------+-----------+ 996 | min-lifetime | integer | RFC XXXX | 997 | max-duration | integer | RFC XXXX | 998 | allow-certificate-get | boolean | RFC XXXX | 999 +-----------------------+------------+-----------+ 1001 6.7. Cert-Not-Before and Cert-Not-After HTTP Headers 1003 The "Message Headers" registry should be updated with the following 1004 additional values: 1006 +-------------------+----------+----------+-----------------------+ 1007 | Header Field Name | Protocol | Status | Reference | 1008 +-------------------+----------+----------+-----------------------+ 1009 | Cert-Not-Before | http | standard | RFC XXXX, Section 3.3 | 1010 | Cert-Not-After | http | standard | RFC XXXX, Section 3.3 | 1011 +-------------------+----------+----------+-----------------------+ 1013 7. Security Considerations 1015 7.1. No revocation 1017 STAR certificates eliminate an important security feature of PKI 1018 which is the ability to revoke certificates. Revocation allows the 1019 administrator to limit the damage done by a rogue node or an 1020 adversary who has control of the private key. With STAR 1021 certificates, expiration replaces revocation so there is potential 1022 for lack of timeliness in the revocation taking effect. To that end, 1023 see also the discussion on clock skew in Section 4.1. 1025 It should be noted that revocation also has timeliness issues, 1026 because both CRLs and OCSP responses have nextUpdate fields that tell 1027 relying parties (RPs) how long they should trust this revocation 1028 data. These fields are typically set to hours, days, or even weeks 1029 in the future. Any revocation that happens before the time in 1030 nextUpdate goes unnoticed by the RP. 1032 One situation where the lack of explicit revocation could create a 1033 security risk to the IdO is when the Order is created with start-date 1034 some appreciable amount of time in the future. Recall that when 1035 authorizations have been fulfilled, the Order moves to the "valid" 1036 state and the star-certificate endpoint is populated with the first 1037 cert (Figure 4). So, if an attacker manages to get hold of the 1038 private key as well as of the first (post-dated) certificate, there 1039 is a time window in the future when they will be able to successfully 1040 impersonate the IdO. Note that cancellation is pointless in this 1041 case. In order to mitigate the described threat, it is RECOMMENDED 1042 that IdO place their Orders at a time that is close to the Order's 1043 start-date. 1045 More discussion of the security of STAR certificates is available in 1046 [Topalovic]. 1048 7.2. Denial of Service Considerations 1050 STAR adds a new attack vector that increases the threat of denial of 1051 service attacks, caused by the change to the CA's behavior. Each 1052 STAR request amplifies the resource demands upon the CA, where one 1053 Order produces not one, but potentially dozens or hundreds of 1054 certificates, depending on the auto-renewal "lifetime" parameter. An 1055 attacker can use this property to aggressively reduce the auto- 1056 renewal "lifetime" (e.g. 1 sec.) jointly with other ACME attack 1057 vectors identified in Sec. 10 of [RFC8555]. Other collateral impact 1058 is related to the certificate endpoint resource where the client can 1059 retrieve the certificates periodically. If this resource is external 1060 to the CA (e.g. a hosted web server), the previous attack will be 1061 reflected to that resource. 1063 Mitigation recommendations from ACME still apply, but some of them 1064 need to be adjusted. For example, applying rate limiting to the 1065 initial request, by the nature of the auto-renewal behavior cannot 1066 solve the above problem. The CA server needs complementary 1067 mitigation and specifically, it SHOULD enforce a minimum value on 1068 auto-renewal "lifetime". Alternatively, the CA can set an internal 1069 certificate generation processes rate limit. Note that this limit 1070 has to take account of already-scheduled renewal issuances as well as 1071 new incoming requests. 1073 7.3. Privacy Considerations 1075 In order to avoid correlation of certificates by account, if 1076 unauthenticated GET is negotiated (Section 3.4) the recommendation in 1077 Section 10.5 of [RFC8555] regarding the choice of URL structure 1078 applies, i.e. servers SHOULD choose URLs of certificate resources in 1079 a non-guessable way, for example using capability URLs 1080 [W3C.WD-capability-urls-20140218]. 1082 8. Acknowledgments 1084 This work is partially supported by the European Commission under 1085 Horizon 2020 grant agreement no. 688421 Measurement and Architecture 1086 for a Middleboxed Internet (MAMI). This support does not imply 1087 endorsement. 1089 Thanks to Ben Kaduk, Richard Barnes, Roman Danyliw, Jon Peterson, 1090 Eric Rescorla, Ryan Sleevi, Sean Turner, Alexey Melnikov, Adam Roach, 1091 Martin Thomson and Mehmet Ersue for helpful comments and discussions 1092 that have shaped this document. 1094 9. References 1096 9.1. Normative References 1098 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1099 Requirement Levels", BCP 14, RFC 2119, 1100 DOI 10.17487/RFC2119, March 1997, 1101 . 1103 [RFC3339] Klyne, G. and C. Newman, "Date and Time on the Internet: 1104 Timestamps", RFC 3339, DOI 10.17487/RFC3339, July 2002, 1105 . 1107 [RFC7231] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer 1108 Protocol (HTTP/1.1): Semantics and Content", RFC 7231, 1109 DOI 10.17487/RFC7231, June 2014, 1110 . 1112 [RFC7234] Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke, 1113 Ed., "Hypertext Transfer Protocol (HTTP/1.1): Caching", 1114 RFC 7234, DOI 10.17487/RFC7234, June 2014, 1115 . 1117 [RFC7807] Nottingham, M. and E. Wilde, "Problem Details for HTTP 1118 APIs", RFC 7807, DOI 10.17487/RFC7807, March 2016, 1119 . 1121 [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for 1122 Writing an IANA Considerations Section in RFCs", BCP 26, 1123 RFC 8126, DOI 10.17487/RFC8126, June 2017, 1124 . 1126 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 1127 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 1128 May 2017, . 1130 [RFC8555] Barnes, R., Hoffman-Andrews, J., McCarney, D., and J. 1131 Kasten, "Automatic Certificate Management Environment 1132 (ACME)", RFC 8555, DOI 10.17487/RFC8555, March 2019, 1133 . 1135 9.2. Informative References 1137 [Acer] Acer, M., Stark, E., Felt, A., Fahl, S., Bhargava, R., 1138 Dev, B., Braithwaite, M., Sleevi, R., and P. Tabriz, 1139 "Where the Wild Warnings Are: Root Causes of Chrome HTTPS 1140 Certificate Errors", DOI 10.1145/3133956.3134007, 2017, 1141 . 1143 [I-D.ietf-acme-star-delegation] 1144 Sheffer, Y., Lopez, D., Pastor, A., and T. Fossati, "An 1145 ACME Profile for Generating Delegated STAR Certificates", 1146 draft-ietf-acme-star-delegation-01 (work in progress), 1147 August 2019. 1149 [I-D.nir-saag-star] 1150 Nir, Y., Fossati, T., Sheffer, Y., and T. Eckert, 1151 "Considerations For Using Short Term Certificates", draft- 1152 nir-saag-star-01 (work in progress), March 2018. 1154 [I-D.sheffer-acme-star-request] 1155 Sheffer, Y., Lopez, D., Dios, O., Pastor, A., and T. 1156 Fossati, "Generating Certificate Requests for Short-Term, 1157 Automatically-Renewed (STAR) Certificates", draft-sheffer- 1158 acme-star-request-02 (work in progress), June 2018. 1160 [OBrien] O'Brien, D. and R. Sleevi, "Chromium Certificate 1161 Transparency Log Policy", 2017, 1162 . 1164 [RFC7633] Hallam-Baker, P., "X.509v3 Transport Layer Security (TLS) 1165 Feature Extension", RFC 7633, DOI 10.17487/RFC7633, 1166 October 2015, . 1168 [RFC7942] Sheffer, Y. and A. Farrel, "Improving Awareness of Running 1169 Code: The Implementation Status Section", BCP 205, 1170 RFC 7942, DOI 10.17487/RFC7942, July 2016, 1171 . 1173 [Stark] Stark, E., Huang, L., Israni, D., Jackson, C., and D. 1174 Boneh, "The case for prefetching and prevalidating TLS 1175 server certificates", 2012, 1176 . 1179 [Topalovic] 1180 Topalovic, E., Saeta, B., Huang, L., Jackson, C., and D. 1181 Boneh, "Towards Short-Lived Certificates", 2012, 1182 . 1185 [W3C.WD-capability-urls-20140218] 1186 Tennison, J., "Good Practices for Capability URLs", World 1187 Wide Web Consortium WD WD-capability-urls-20140218, 1188 February 2014, 1189 . 1191 Appendix A. Document History 1193 [[Note to RFC Editor: please remove before publication.]] 1195 A.1. draft-ietf-acme-star-10 1197 IESG processing: 1199 o More clarity on IANA registration (Alexey); 1200 o HTTP header requirements adjustments (Adam); 1201 o Misc editorial (Ben) 1203 A.2. draft-ietf-acme-star-09 1205 Richard and Ryan's review resulted in the following updates: 1207 o STAR Order and Directory Meta attributes renamed slightly and 1208 grouped under two brand new "auto-renewal" objects; 1209 o IANA registration updated accordingly (note that two new 1210 registries have been added as a consequence); 1211 o Unbounded pre-dating of certificates removed so that STAR certs 1212 are never issued with their notBefore in the past; 1213 o Changed "recurrent" to "autoRenewal" in error codes; 1214 o Changed "recurrent" to "auto-renewal" in reference to Orders; 1215 o Added operational considerations for HTTP caches. 1217 A.3. draft-ietf-acme-star-08 1219 o Improved text on interaction with CT Logs, responding to Mehmet 1220 Ersue's review. 1222 A.4. draft-ietf-acme-star-07 1224 o Changed the HTTP headers names and clarified the IANA 1225 registration, following feedback from the IANA expert reviewer 1227 A.5. draft-ietf-acme-star-06 1229 o Roman's AD review 1231 A.6. draft-ietf-acme-star-05 1233 o EKR's AD review 1234 o A detailed example of the timing of certificate issuance and 1235 predating 1236 o Added an explicit client-side parameter for predating 1237 o Security considerations around unauthenticated GET 1239 A.7. draft-ietf-acme-star-04 1241 o WG last call comments by Sean Turner 1242 o revokeCert interface handling 1243 o Allow negotiating plain-GET for certs 1244 o In STAR Orders, use star-certificate instead of certificate 1246 A.8. draft-ietf-acme-star-03 1248 o Clock skew considerations 1249 o Recommendations for "short" in the Web use case 1250 o CT log considerations 1252 A.9. draft-ietf-acme-star-02 1254 o Discovery of STAR capabilities via the directory object 1255 o Use the more generic term Identifier Owner (IdO) instead of Domain 1256 Name Owner (DNO) 1257 o More precision about what goes in the order 1258 o Detail server side behavior on cancellation 1260 A.10. draft-ietf-acme-star-01 1262 o Generalized the introduction, separating out the specifics of 1263 CDNs. 1264 o Clean out LURK-specific text. 1265 o Using a POST to ensure cancellation is authenticated. 1266 o First and last date of recurrent cert, as absolute dates. 1267 Validity of certs in seconds. 1268 o Use RFC7807 "Problem Details" in error responses. 1269 o Add IANA considerations. 1270 o Changed the document's title. 1272 A.11. draft-ietf-acme-star-00 1274 o Initial working group version. 1275 o Removed the STAR interface, the protocol between NDC and DNO. 1276 What remains is only the extended ACME protocol. 1278 A.12. draft-sheffer-acme-star-02 1280 o Using a more generic term for the delegation client, NDC. 1281 o Added an additional use case: public cloud services. 1282 o More detail on ACME authorization. 1284 A.13. draft-sheffer-acme-star-01 1286 o A terminology section. 1287 o Some cleanup. 1289 A.14. draft-sheffer-acme-star-00 1291 o Renamed draft to prevent confusion with other work in this space. 1292 o Added an initial STAR protocol: a REST API. 1293 o Discussion of CDNI use cases. 1295 A.15. draft-sheffer-acme-star-lurk-00 1297 o Initial version. 1299 Authors' Addresses 1301 Yaron Sheffer 1302 Intuit 1304 EMail: yaronf.ietf@gmail.com 1306 Diego Lopez 1307 Telefonica I+D 1309 EMail: diego.r.lopez@telefonica.com 1311 Oscar Gonzalez de Dios 1312 Telefonica I+D 1314 EMail: oscar.gonzalezdedios@telefonica.com 1316 Antonio Agustin Pastor Perales 1317 Telefonica I+D 1319 EMail: antonio.pastorperales@telefonica.com 1321 Thomas Fossati 1322 ARM 1324 EMail: thomas.fossati@arm.com