idnits 2.17.1 draft-ietf-acme-star-02.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- No issues found here. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year -- The document date (November 29, 2017) is 2338 days in the past. Is this intentional? Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Outdated reference: A later version (-18) exists of draft-ietf-acme-acme-08 ** Obsolete normative reference: RFC 7231 (Obsoleted by RFC 9110) ** Obsolete normative reference: RFC 7807 (Obsoleted by RFC 9457) == Outdated reference: A later version (-01) exists of draft-nir-saag-star-00 == Outdated reference: A later version (-02) exists of draft-sheffer-acme-star-request-01 Summary: 2 errors (**), 0 flaws (~~), 4 warnings (==), 1 comment (--). 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: June 2, 2018 O. Gonzalez de Dios 6 A. Pastor Perales 7 Telefonica I+D 8 T. Fossati 9 Nokia 10 November 29, 2017 12 Support for Short-Term, Automatically-Renewed (STAR) Certificates in 13 Automated Certificate Management Environment (ACME) 14 draft-ietf-acme-star-02 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 attacker. 20 However the revocation process is often unreliable. An alternative 21 to revocation is issuing a sequence of certificates, each with a 22 short validity period, and terminating this sequence upon compromise. 23 This memo proposes an ACME extension to enable the issuance of short- 24 term and automatically renewed (STAR) certificates. 26 [RFC Editor: please remove before publication] 28 While the draft is being developed, the editor's version can be found 29 at https://github.com/yaronf/I-D/tree/master/STAR. 31 Status of This Memo 33 This Internet-Draft is submitted in full conformance with the 34 provisions of BCP 78 and BCP 79. 36 Internet-Drafts are working documents of the Internet Engineering 37 Task Force (IETF). Note that other groups may also distribute 38 working documents as Internet-Drafts. The list of current Internet- 39 Drafts is at http://datatracker.ietf.org/drafts/current/. 41 Internet-Drafts are draft documents valid for a maximum of six months 42 and may be updated, replaced, or obsoleted by other documents at any 43 time. It is inappropriate to use Internet-Drafts as reference 44 material or to cite them other than as "work in progress." 46 This Internet-Draft will expire on June 2, 2018. 48 Copyright Notice 50 Copyright (c) 2017 IETF Trust and the persons identified as the 51 document authors. All rights reserved. 53 This document is subject to BCP 78 and the IETF Trust's Legal 54 Provisions Relating to IETF Documents 55 (http://trustee.ietf.org/license-info) in effect on the date of 56 publication of this document. Please review these documents 57 carefully, as they describe your rights and restrictions with respect 58 to this document. Code Components extracted from this document must 59 include Simplified BSD License text as described in Section 4.e of 60 the Trust Legal Provisions and are provided without warranty as 61 described in the Simplified BSD License. 63 Table of Contents 65 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 66 1.1. Name Delegation Use Case . . . . . . . . . . . . . . . . 4 67 1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4 68 1.3. Conventions used in this document . . . . . . . . . . . . 4 69 2. Protocol Flow . . . . . . . . . . . . . . . . . . . . . . . . 4 70 2.1. Bootstrap . . . . . . . . . . . . . . . . . . . . . . . . 5 71 2.2. Refresh . . . . . . . . . . . . . . . . . . . . . . . . . 5 72 2.3. Termination . . . . . . . . . . . . . . . . . . . . . . . 6 73 3. Protocol Details . . . . . . . . . . . . . . . . . . . . . . 7 74 3.1. ACME Extensions . . . . . . . . . . . . . . . . . . . . . 7 75 3.1.1. Extending the Order Resource . . . . . . . . . . . . 7 76 3.1.2. Canceling a Recurrent Order . . . . . . . . . . . . . 8 77 3.2. Capability Discovery . . . . . . . . . . . . . . . . . . 9 78 3.3. Fetching the Certificates . . . . . . . . . . . . . . . . 10 79 4. Operational Considerations . . . . . . . . . . . . . . . . . 11 80 4.1. Define "short" . . . . . . . . . . . . . . . . . . . . . 11 81 4.2. Clock Skew . . . . . . . . . . . . . . . . . . . . . . . 11 82 4.3. Certificate Transparency (CT) Logs . . . . . . . . . . . 11 83 5. Implementation Status . . . . . . . . . . . . . . . . . . . . 11 84 5.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . 12 85 5.1.1. ACME Server with STAR extension . . . . . . . . . . . 12 86 5.1.2. STAR Proxy . . . . . . . . . . . . . . . . . . . . . 12 87 5.2. Level of Maturity . . . . . . . . . . . . . . . . . . . . 13 88 5.3. Coverage . . . . . . . . . . . . . . . . . . . . . . . . 13 89 5.4. Version Compatibility . . . . . . . . . . . . . . . . . . 13 90 5.5. Licensing . . . . . . . . . . . . . . . . . . . . . . . . 13 91 5.6. Implementation experience . . . . . . . . . . . . . . . . 13 92 5.7. Contact Information . . . . . . . . . . . . . . . . . . . 14 93 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14 94 6.1. New ACME Error Types . . . . . . . . . . . . . . . . . . 14 95 6.2. New ACME Order Object Fields . . . . . . . . . . . . . . 14 96 6.3. Not-Before and Not-After HTTP Headers . . . . . . . . . . 15 97 7. Security Considerations . . . . . . . . . . . . . . . . . . . 15 98 7.1. Denial of Service Considerations . . . . . . . . . . . . 15 99 7.2. Additional Considerations TBD . . . . . . . . . . . . . . 16 100 8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 16 101 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 16 102 9.1. Normative References . . . . . . . . . . . . . . . . . . 16 103 9.2. Informative References . . . . . . . . . . . . . . . . . 16 104 Appendix A. Document History . . . . . . . . . . . . . . . . . . 18 105 A.1. draft-ietf-acme-star-02 . . . . . . . . . . . . . . . . . 18 106 A.2. draft-ietf-acme-star-01 . . . . . . . . . . . . . . . . . 18 107 A.3. draft-ietf-acme-star-00 . . . . . . . . . . . . . . . . . 18 108 A.4. draft-sheffer-acme-star-02 . . . . . . . . . . . . . . . 18 109 A.5. draft-sheffer-acme-star-01 . . . . . . . . . . . . . . . 18 110 A.6. draft-sheffer-acme-star-00 . . . . . . . . . . . . . . . 18 111 A.7. draft-sheffer-acme-star-lurk-00 . . . . . . . . . . . . . 19 112 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 19 114 1. Introduction 116 The ACME protocol [I-D.ietf-acme-acme] automates the process of 117 issuing a certificate to a named entity (an Identity Owner or IdO). 118 Typically, but not always, the identity is a domain name and we may 119 refer to the entity as a Domain Name Owner (DNO). 121 If the IdO wishes to obtain a string of short-term certificates 122 originating from the same private key (see [Topalovic] about why 123 using short-lived certificates might be preferable to explicit 124 revocation), she must go through the whole ACME protocol each time a 125 new short-term certificate is needed - e.g., every 2-3 days. If done 126 this way, the process would involve frequent interactions between the 127 registration function of the ACME Certification Authority (CA) and 128 the identity provider infrastructure (e.g.: DNS, web servers), 129 therefore making the issuance of short-term certificates exceedingly 130 dependent on the reliability of both. 132 This document presents an extension of the ACME protocol that 133 optimizes this process by making short-term certificates first class 134 objects in the ACME ecosystem. Once the order for a string of short- 135 term certificates is accepted, the CA is responsible for publishing 136 the next certificate at an agreed upon URL before the previous one 137 expires. The IdO can terminate the automatic renewal before the 138 natural deadline, if needed - e.g., on key compromise. 140 For a more generic treatment of STAR certificates, readers are 141 referred to [I-D.nir-saag-star]. 143 1.1. Name Delegation Use Case 145 The proposed mechanism can be used as a building block of an 146 efficient name-delegation protocol, for example one that exists 147 between a CDN or a cloud provider and its customers 148 [I-D.sheffer-acme-star-request]. At any time, the service customer 149 (i.e., the IdO) can terminate the delegation by simply instructing 150 the CA to stop the automatic renewal and letting the currently active 151 certificate expire shortly thereafter. 153 1.2. Terminology 155 IdO Identifier Owner, the owner of an identifier, e.g.: a domain 156 name, a telephone number. 157 DNO Domain Name Owner, a type of IdO whose identifier is a domain 158 name. 159 STAR Short-Term, Automatically Renewed X.509 certificates. 160 NDC Name Delegation Client, an entity to which the identifier owned 161 by the IdO is delegated for a limited time. Examples include a 162 CDN edge cache, a cloud provider's load balancer or Web 163 Application Firewall (WAF). 165 1.3. Conventions used in this document 167 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 168 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 169 "OPTIONAL" in this document are to be interpreted as described in 170 [RFC2119]. 172 2. Protocol Flow 174 The following subsections describe the three main phases of the 175 protocol: 177 o Bootstrap: the IdO asks an ACME CA to create a short-term and 178 automatically-renewed (STAR) certificate (Section 2.1); 179 o Auto-renewal: the ACME CA periodically re-issues the short-term 180 certificate and posts it to a public URL (Section 2.2); 181 o Termination: the IdO requests the ACME CA to discontinue the 182 automatic renewal of the certificate (Section 2.3). 184 This diagram presents the entities that are (or may be) involved in 185 the protocol and their interactions during the different phases. 187 Refresh 188 . . . . . . . . . . . . . . . . . . . . 189 . ' ` v 190 .-----. Bootstrap / Terminate .---------. 191 | IdO |------------------------------------->| ACME CA | 192 `-----' `---------' 193 ^ .- - -. ^ 194 ` . . . . . . . . : NDC : . . . . . . . . . ' 195 Request `- - -' Refresh 196 Delegation 198 Note that there might be a distinct NDC entity (e.g., a CDN edge 199 cache) that uses a separate channel to request the IdO to set up a 200 name delegation. The protocol described in 201 [I-D.sheffer-acme-star-request] may be used for this purpose. 203 2.1. Bootstrap 205 The IdO, in its role as an ACME client, requests the CA to issue a 206 STAR certificate, i.e., one that: 208 o Has a short validity, e.g., 24 to 72 hours. Note that the exact 209 definition of "short" depends on the use case; 210 o Is automatically renewed by the CA for a certain period of time; 211 o Is downloadable from a (highly available) public link without 212 requiring any special authorization. 214 Other than that, the ACME protocol flows as usual between IdO and CA. 215 In particular, IdO is responsible for satisfying the requested ACME 216 challenges until the CA is willing to issue the requested 217 certificate. Per normal ACME processing, the IdO is given back an 218 order URL for the issued STAR certificate to be used in subsequent 219 interaction with the CA (e.g., if the certificate needs to be 220 terminated.) 222 The bootstrap phase ends when the IdO obtains a confirmation from the 223 ACME CA that includes a certificate endpoint. 225 2.2. Refresh 227 The CA automatically re-issues the certificate using the same CSR 228 (and therefore the same identifier and public key) before it expires 229 and publishes it to the URL that was returned to the IdO at the end 230 of the bootstrap phase. The certificate user, which could be either 231 the IdO itself or a delegated third party, as described in 232 [I-D.sheffer-acme-star-request], obtains the certificate and uses it. 234 The refresh process (Figure 1) goes on until either: 236 o IdO explicitly terminates the automatic renewal (Section 2.3); or 237 o Automatic renewal expires. 239 Certificate ACME/STAR 240 User Server 241 | Retrieve cert | [...] 242 |---------------------->| | 243 | +------. / 244 | | | / 245 | | Automatic renewal : 246 | | | \ 247 | |<-----' \ 248 | Retrieve cert | | 249 |---------------------->| 72 hours 250 | | | 251 | +------. / 252 | | | / 253 | | Automatic renewal : 254 | | | \ 255 | |<-----' \ 256 | Retrieve cert | | 257 |---------------------->| 72 hours 258 | | | 259 | +------. / 260 | | | / 261 | | Automatic renewal : 262 | | | \ 263 | |<-----' \ 264 | | | 265 | [...] | [...] 267 Figure 1: Auto renewal 269 2.3. Termination 271 The IdO may request early termination of the STAR certificate by 272 sending a cancellation request to the order resource, as described in 273 Section 3.1.2. After the CA receives and verifies the request, it 274 shall: 276 o Cancel the automatic renewal process for the STAR certificate; 277 o Change the certificate publication resource to return an error 278 indicating the termination of the issuance; 279 o Change the status of the order to "canceled". 281 Note that it is not necessary to explicitly revoke the short-term 282 certificate. 284 Certificate ACME/STAR 285 User IdO Server 286 | | | 287 | | Terminate order | 288 | +---------------------->| 289 | | +-------. 290 | | | | 291 | | | End auto renewal 292 | | | Remove cert link 293 | | | etc. 294 | | | | 295 | | Done |<------' 296 | |<----------------------+ 297 | | | 298 | | 299 | Retrieve cert | 300 +---------------------------------------------->| 301 | Error: terminated | 302 |<----------------------------------------------+ 303 | | 305 Figure 2: Termination 307 3. Protocol Details 309 This section describes the protocol details, namely the extensions to 310 the ACME protocol required to issue STAR certificates. 312 3.1. ACME Extensions 314 This protocol extends the ACME protocol, to allow for recurrent 315 orders. 317 3.1.1. Extending the Order Resource 319 The order resource is extended with the following attributes: 321 { 322 "recurrent": true, 323 "recurrent-start-date": "2016-01-01T00:00:00Z", 324 "recurrent-end-date": "2017-01-01T00:00:00Z", 325 "recurrent-certificate-validity": 604800 326 } 328 o recurrent: MUST be true for STAR certificates. 329 o recurrent-start-date: the earliest date of validity of the first 330 certificate issued, in [RFC3339] format. This attribute is 331 optional. When omitted, the start date is as soon as 332 authorization is complete. 333 o recurrent-end-date: the latest date of validity of the last 334 certificate issued, in [RFC3339] format. 335 o recurrent-certificate-validity: the maximum validity period of 336 each STAR certificate, an integer that denotes a number of 337 seconds. 339 These attributes are included in a POST message when creating the 340 order, as part of the "payload" encoded object. They are returned 341 when the order has been created, and the ACME server MAY adjust them 342 at will, according to its local policy (see also Section 3.2). 344 The optional notBefore and notAfter fields MUST NOT be present in a 345 STAR order. 347 ACME defines the following values for the order resource's status: 348 "invalid", "pending", "processing", "valid". In the case of 349 recurrent orders, the status MUST be "valid" as long as STAR 350 certificates are being issued. We add a new status value: 351 "canceled", see Section 3.1.2. 353 3.1.2. Canceling a Recurrent Order 355 An important property of the recurrent order is that it can be 356 canceled by the IdO, with no need for certificate revocation. To 357 cancel the order, the ACME client sends a POST to the order URL: 359 POST /acme/order/1 HTTP/1.1 360 Host: acme-server.example.org 361 Content-Type: application/jose+json 363 { 364 "protected": base64url({ 365 "alg": "ES256", 366 "kid": "https://example.com/acme/acct/1", 367 "nonce": "5XJ1L3lEkMG7tR6pA00clA", 368 "url": "https://example.com/acme/order/1" 369 }), 370 "payload": base64url({ 371 "status": "canceled" 372 }), 373 "signature": "H6ZXtGjTZyUnPeKn...wEA4TklBdh3e454g" 374 } 376 The server MUST NOT issue any additional certificates for this order, 377 beyond the certificate that is available for collection at the time 378 of deletion. 380 Immediately after the order is canceled, the server: 382 o MUST update the status of the order resource to "canceled" and 383 MUST set an appropriate "expires" date; 384 o MUST respond with 403 (Forbidden) to any requests to the 385 certificate endpoint. The response SHOULD provide additional 386 information using a problem document [RFC7807] with type 387 "urn:ietf:params:acme:error:recurrentOrderCanceled". 389 Issuing a cancellation for an order that is not in "valid" state has 390 undefined semantics. A client MUST NOT send such a request, and a 391 server MUST return an error response with status code 400 (Bad 392 Request) and type 393 "urn:ietf:params:acme:error:recurrentCancellationInvalid". 395 3.2. Capability Discovery 397 In order to support the discovery of STAR capabilities, The directory 398 object of an ACME STAR server MUST contain the following attributes 399 inside the "meta" field: 401 o star-enabled: boolean flag indicating STAR support. An ACME STAR 402 server MUST include this key, and MUST set it to true if the 403 feature is enabled. 404 o star-min-cert-validity: minimum acceptable value for recurrent- 405 certificate-validity, in seconds. 406 o star-max-renewal: maximum delta between recurrent-end-date and 407 recurrent-start-date, in seconds. 409 Example directory object advertising STAR support with one day star- 410 min-cert-validity and one year star-max-renewal: 412 { 413 "new-nonce": "https://example.com/acme/new-nonce", 414 "new-account": "https://example.com/acme/new-account", 415 "new-order": "https://example.com/acme/new-order", 416 "new-authz": "https://example.com/acme/new-authz", 417 "revoke-cert": "https://example.com/acme/revoke-cert", 418 "key-change": "https://example.com/acme/key-change", 419 "meta": { 420 "terms-of-service": "https://example.com/acme/terms/2017-5-30", 421 "website": "https://www.example.com/", 422 "caa-identities": ["example.com"], 423 "star-enabled": true, 424 "star-min-cert-validity": 86400, 425 "star-max-renewal": 31536000 426 } 427 } 429 3.3. Fetching the Certificates 431 The certificate is fetched from the certificate endpoint, as per 432 [I-D.ietf-acme-acme], Section 7.4.2. 434 GET /acme/cert/asdf HTTP/1.1 435 Host: acme-server.example.org 436 Accept: application/pkix-cert 438 HTTP/1.1 200 OK 439 Content-Type: application/pem-certificate-chain 440 Link: ;rel="index" 441 Not-Before: Mon, 1 Feb 2016 00:00:00 GMT 442 Not-After: Mon, 8 Feb 2016 00:00:00 GMT 444 -----BEGIN CERTIFICATE----- 445 [End-entity certificate contents] 446 -----END CERTIFICATE----- 447 -----BEGIN CERTIFICATE----- 448 [Issuer certificate contents] 449 -----END CERTIFICATE----- 450 -----BEGIN CERTIFICATE----- 451 [Other certificate contents] 452 -----END CERTIFICATE----- 454 The Server SHOULD include the "Not-Before" and "Not-After" HTTP 455 headers in the response. When they exist, they MUST be equal to the 456 respective fields inside the end-entity certificate. Their format is 457 "HTTP-date" as defined in Section 7.1.1.2 of [RFC7231]. Their 458 purpose is to enable client implementations that do not parse the 459 certificate. 461 To improve robustness, the next certificate MUST be made available by 462 the ACME CA at the latest halfway through the lifetime of the 463 currently active certificate. It is worth noting that this has an 464 implication in case of cancellation: in fact, from the time the next 465 certificate is made available, the cancellation is not completely 466 effective until the latter also expires. 468 The server MUST NOT issue any additional certificates for this order 469 beyond its recurrent-end-date. 471 Immediately after the order expires, the server MUST respond with 403 472 (Forbidden) to any requests to the certificate endpoint. The 473 response SHOULD provide additional information using a problem 474 document [RFC7807] with type 475 "urn:ietf:params:acme:error:recurrentOrderExpired". 477 4. Operational Considerations 479 4.1. Define "short" 481 TBD 483 o Short is a relative concept: defining a cut-off point in this 484 document would be arbitrary. The lifetime of a STAR certificate 485 is defined by the requirements for revocation on a case by case 486 basis. 488 4.2. Clock Skew 490 TBD 492 o tweaking notBefore (maybe reference [I-D.nir-saag-star]) 493 o Browser use case: to select the lower bound for short-term (5-7 494 days) see Section 7.1 of [Acer]. 496 4.3. Certificate Transparency (CT) Logs 498 TBD 500 o Browser use case only: STAR increase in CT log ingestion rate 501 (quantify). How to deal with it is not part of this document. 503 5. Implementation Status 505 Note to RFC Editor: please remove this section before publication, 506 including the reference to [RFC7942]. 508 This section records the status of known implementations of the 509 protocol defined by this specification at the time of posting of this 510 Internet-Draft, and is based on a proposal described in [RFC7942]. 511 The description of implementations in this section is intended to 512 assist the IETF in its decision processes in progressing drafts to 513 RFCs. Please note that the listing of any individual implementation 514 here does not imply endorsement by the IETF. Furthermore, no effort 515 has been spent to verify the information presented here that was 516 supplied by IETF contributors. This is not intended as, and must not 517 be construed to be, a catalog of available implementations or their 518 features. Readers are advised to note that other implementations may 519 exist. 521 According to [RFC7942], "this will allow reviewers and working groups 522 to assign due consideration to documents that have the benefit of 523 running code, which may serve as evidence of valuable experimentation 524 and feedback that have made the implemented protocols more mature. 526 It is up to the individual working groups to use this information as 527 they see fit". 529 5.1. Overview 531 The implementation is constructed around 3 elements: STAR Client for 532 NDC, STAR Proxy for IdO and ACME Server for CA. The communication 533 between them is over an IP network and the HTTPS protocol. 535 The software of the implementation is available at: 536 https://github.com/mami-project/lurk 538 The following subsections offer a basic description, detailed 539 information is available in https://github.com/mami- 540 project/lurk/blob/master/proxySTAR_v2/README.md 542 5.1.1. ACME Server with STAR extension 544 This is a fork of the Let's Encrypt Boulder project that implements 545 an ACME compliant CA. It includes modifications to extend the ACME 546 protocol as it is specified in this draft, to support recurrent 547 orders and cancelling orders. 549 The implementation understands the new "recurrent" attributes as part 550 of the Certificate issuance in the POST request for a new resource. 551 An additional process "renewalManager.go" has been included in 552 parallel that reads the details of each recurrent request, 553 automatically produces a "cron" Linux based task that issues the 554 recurrent certificates, until the lifetime ends or the order is 555 canceled. This process is also in charge of maintaining a fixed URI 556 to enable the NDC to download certificates, unlike Boulder's regular 557 process of producing a unique URI per certificate. 559 5.1.2. STAR Proxy 561 The STAR Proxy has a double role as ACME client and STAR Server. The 562 former is a fork of the EFF Certbot project that implements an ACME 563 compliant client with the STAR extension. The latter is a basic HTTP 564 REST API server. 566 The STAR Proxy understands the basic API request with a server. The 567 current implementation of the API is defined in draft-ietf-acme-star- 568 01. Registration or order cancellation triggers the modified Certbot 569 client that requests, or cancels, the recurrent generation of 570 certificates using the STAR extension over ACME protocol. The URI 571 with the location of the recurrent certificate is delivered to the 572 STAR client as a response. 574 5.2. Level of Maturity 576 This is a prototype. 578 5.3. Coverage 580 A STAR Client is not included in this implementation, but done by 581 direct HTTP request with any open HTTP REST API tool. This is 582 expected to be covered as part of the [I-D.sheffer-acme-star-request] 583 implementation. 585 This implementation completely covers STAR Proxy and ACME Server with 586 STAR extension 588 5.4. Version Compatibility 590 The implementation is compatible with version draft-ietf-acme-star- 591 01. The implementation is based on the Boulder and Certbot code 592 release from 7-Aug-2017. 594 5.5. Licensing 596 This implementation inherits the Boulder license (Mozilla Public 597 License 2.0) and Certbot license (Apache License Version 2.0 ). 599 5.6. Implementation experience 601 To prove the concept all the implementation has been done with a 602 self-signed CA, to avoid impact on real domains. To be able to do it 603 we use the FAKE_DNS property of Boulder and static /etc/hosts entries 604 with domains names. Nonetheless this implementation should run with 605 real domains. 607 Most of the implementation has been made to avoid deep changes inside 608 of Boulder or Certbot, for example, the recurrent certificates 609 issuance by the CA is based on an external process that auto- 610 configures the standard Linux "cron" daemon in the ACME CA server. 612 The reference setup recommended is one physical host with 3 virtual 613 machines, one for each of the 3 components (client, proxy and server) 614 and the connectivity based on host bridge. 616 Network security is not enabled (iptables default policies are 617 "accept" and all rules removed) in this implementation to simplify 618 and test the protocol. 620 5.7. Contact Information 622 See author details below. 624 6. IANA Considerations 626 [[RFC Editor: please replace XXXX below by the RFC number.]] 628 6.1. New ACME Error Types 630 This document adds the following entries to the ACME Error Type 631 registry: 633 +------------------------------+------------------------+-----------+ 634 | Type | Description | Reference | 635 +------------------------------+------------------------+-----------+ 636 | recurrentOrderCanceled | The short-term | RFC XXXX | 637 | | certificate is no | | 638 | | longer available | | 639 | | because the recurrent | | 640 | | order has been | | 641 | | explicitly canceled by | | 642 | | the IdO | | 643 | recurrentOrderExpired | The short-term | RFC XXXX | 644 | | certificate is no | | 645 | | longer available | | 646 | | because the recurrent | | 647 | | order has expired | | 648 | recurrentCancellationInvalid | A request to cancel a | RFC XXXX | 649 | | recurrent order that | | 650 | | is not in state | | 651 | | "valid" has been | | 652 | | received | | 653 +------------------------------+------------------------+-----------+ 655 6.2. New ACME Order Object Fields 657 This document adds the following entries to the ACME Order Object 658 Fields registry: 660 +-------------------------------+--------+--------------+-----------+ 661 | Field Name | Field | Configurable | Reference | 662 | | Type | | | 663 +-------------------------------+--------+--------------+-----------+ 664 | recurrent | string | true | RFC XXXX | 665 | recurrent-start-date | string | true | RFC XXXX | 666 | recurrent-end-date | string | true | RFC XXXX | 667 | recurrent-certificate- | string | true | RFC XXXX | 668 | validity | | | | 669 +-------------------------------+--------+--------------+-----------+ 671 6.3. Not-Before and Not-After HTTP Headers 673 The "Message Headers" registry should be updated with the following 674 additional values: 676 +-------------------+----------+----------+-----------+ 677 | Header Field Name | Protocol | Status | Reference | 678 +-------------------+----------+----------+-----------+ 679 | Not-Before | http | standard | RFC XXXX | 680 | Not-After | http | standard | RFC XXXX | 681 +-------------------+----------+----------+-----------+ 683 7. Security Considerations 685 7.1. Denial of Service Considerations 687 STAR adds a new attack vector that increases the threat of denial of 688 service attacks, caused by the change to the CA's behavior. Each 689 STAR request amplifies the resource demands upon the CA, where one 690 order produces not one, but potentially dozens or hundreds of 691 certificates, depending on the "recurrent-certificate-validity" 692 parameter. An attacker can use this property to aggressively reduce 693 the "recurrent-certificate-validity" (e.g. 1 sec.) jointly with other 694 ACME attack vectors identified in Sec. 10 of [I-D.ietf-acme-acme]. 695 Other collateral impact is related to the certificate endpoint 696 resource where the client can retrieve the certificates periodically. 697 If this resource is external to the CA (e.g. a hosted web server), 698 the previous attack will be reflected to that resource. 700 Mitigation recommendations from ACME still apply, but some of them 701 need to be adjusted. For example, applying rate limiting to the 702 initial request, by the nature of the recurrent behavior cannot solve 703 the above problem. The CA server needs complementary mitigation and 704 specifically, it SHOULD enforce a minimum value on "recurrent- 705 certificate-validity". Alternatively, the CA can set an internal 706 certificate generation processes rate limit. 708 7.2. Additional Considerations TBD 710 8. Acknowledgments 712 This work is partially supported by the European Commission under 713 Horizon 2020 grant agreement no. 688421 Measurement and Architecture 714 for a Middleboxed Internet (MAMI). This support does not imply 715 endorsement. 717 Thanks to Jon Peterson and Martin Thomson for helpful comments and 718 discussions that have shaped this document. 720 9. References 722 9.1. Normative References 724 [I-D.ietf-acme-acme] 725 Barnes, R., Hoffman-Andrews, J., and J. Kasten, "Automatic 726 Certificate Management Environment (ACME)", draft-ietf- 727 acme-acme-08 (work in progress), October 2017. 729 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 730 Requirement Levels", BCP 14, RFC 2119, 731 DOI 10.17487/RFC2119, March 1997, . 734 [RFC3339] Klyne, G. and C. Newman, "Date and Time on the Internet: 735 Timestamps", RFC 3339, DOI 10.17487/RFC3339, July 2002, 736 . 738 [RFC7231] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer 739 Protocol (HTTP/1.1): Semantics and Content", RFC 7231, 740 DOI 10.17487/RFC7231, June 2014, . 743 [RFC7807] Nottingham, M. and E. Wilde, "Problem Details for HTTP 744 APIs", RFC 7807, DOI 10.17487/RFC7807, March 2016, 745 . 747 9.2. Informative References 749 [Acer] Acer, M., Stark, E., Felt, A., Fahl, S., Bhargava, R., 750 Dev, B., Braithwaite, M., Sleevi, R., and P. Tabriz, 751 "Where the Wild Warnings Are: Root Causes of Chrome HTTPS 752 Certificate Errors", DOI 10.1145/3133956.3134007, 2017, 753 . 755 [I-D.nir-saag-star] 756 Nir, Y., Fossati, T., and Y. Sheffer, "Considerations For 757 Using Short Term Certificates", draft-nir-saag-star-00 758 (work in progress), October 2017. 760 [I-D.sheffer-acme-star-request] 761 Sheffer, Y., Lopez, D., Dios, O., Pastor, A., and T. 762 Fossati, "Generating Certificate Requests for Short-Term, 763 Automatically-Renewed (STAR) Certificates", draft-sheffer- 764 acme-star-request-01 (work in progress), June 2017. 766 [RFC7942] Sheffer, Y. and A. Farrel, "Improving Awareness of Running 767 Code: The Implementation Status Section", BCP 205, 768 RFC 7942, DOI 10.17487/RFC7942, July 2016, 769 . 771 [Topalovic] 772 Topalovic, E., Saeta, B., Huang, L., Jackson, C., and D. 773 Boneh, "Towards Short-Lived Certificates", 2012, 774 . 776 Appendix A. Document History 778 [[Note to RFC Editor: please remove before publication.]] 780 A.1. draft-ietf-acme-star-02 782 o Discovery of STAR capabilities via the directory object 783 o Use the more generic term Identifier Owner (IdO) instead of Domain 784 Name Owner (DNO) 785 o More precision about what goes in the order 786 o Detail server side behavior on cancellation 788 A.2. draft-ietf-acme-star-01 790 o Generalized the introduction, separating out the specifics of 791 CDNs. 792 o Clean out LURK-specific text. 793 o Using a POST to ensure cancellation is authenticated. 794 o First and last date of recurrent cert, as absolute dates. 795 Validity of certs in seconds. 796 o Use RFC7807 "Problem Details" in error responses. 797 o Add IANA considerations. 798 o Changed the document's title. 800 A.3. draft-ietf-acme-star-00 802 o Initial working group version. 803 o Removed the STAR interface, the protocol between NDC and DNO. 804 What remains is only the extended ACME protocol. 806 A.4. draft-sheffer-acme-star-02 808 o Using a more generic term for the delegation client, NDC. 809 o Added an additional use case: public cloud services. 810 o More detail on ACME authorization. 812 A.5. draft-sheffer-acme-star-01 814 o A terminology section. 815 o Some cleanup. 817 A.6. draft-sheffer-acme-star-00 819 o Renamed draft to prevent confusion with other work in this space. 820 o Added an initial STAR protocol: a REST API. 821 o Discussion of CDNI use cases. 823 A.7. draft-sheffer-acme-star-lurk-00 825 o Initial version. 827 Authors' Addresses 829 Yaron Sheffer 830 Intuit 832 EMail: yaronf.ietf@gmail.com 834 Diego Lopez 835 Telefonica I+D 837 EMail: diego.r.lopez@telefonica.com 839 Oscar Gonzalez de Dios 840 Telefonica I+D 842 EMail: oscar.gonzalezdedios@telefonica.com 844 Antonio Agustin Pastor Perales 845 Telefonica I+D 847 EMail: antonio.pastorperales@telefonica.com 849 Thomas Fossati 850 Nokia 852 EMail: thomas.fossati@nokia.com