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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group G. Huston 3 Internet-Draft APNIC 4 Obsoletes: 7730 (if approved) S. Weiler 5 Intended status: Standards Track W3C/MIT 6 Expires: November 1, 2019 G. Michaelson 7 APNIC 8 S. Kent 9 Unaffiliated 10 T. Bruijnzeels 11 NLnet Labs 12 April 30, 2019 14 Resource Public Key Infrastructure (RPKI) Trust Anchor Locator 15 draft-ietf-sidrops-https-tal-08 17 Abstract 19 This document defines a Trust Anchor Locator (TAL) for the Resource 20 Public Key Infrastructure (RPKI). TALs allow Relying Parties in the 21 RPKI to download the current Trust Anchor (TA) CA certificate from 22 one or more locations, and verify that the key of this self-signed 23 certificate matches the key on the TAL. Thus, Relying Parties can be 24 configured with TA keys, but allow these TAs to change the content of 25 their CA certificate. In particular it allows TAs to change the set 26 of IP Address Delegations and/or Autonomous System Identifier 27 Delegations included in the RFC3779 extension of their certificate. 29 This document obsoletes the previous definition of Trust Anchor 30 Locators in RFC 7730 by adding support for RFC3986 Uniform Resource 31 Identifiers (URIs) that use HTTPS as the scheme. 33 Status of This Memo 35 This Internet-Draft is submitted in full conformance with the 36 provisions of BCP 78 and BCP 79. 38 Internet-Drafts are working documents of the Internet Engineering 39 Task Force (IETF). Note that other groups may also distribute 40 working documents as Internet-Drafts. The list of current Internet- 41 Drafts is at https://datatracker.ietf.org/drafts/current/. 43 Internet-Drafts are draft documents valid for a maximum of six months 44 and may be updated, replaced, or obsoleted by other documents at any 45 time. It is inappropriate to use Internet-Drafts as reference 46 material or to cite them other than as "work in progress." 48 This Internet-Draft will expire on November 1, 2019. 50 Copyright Notice 52 Copyright (c) 2019 IETF Trust and the persons identified as the 53 document authors. All rights reserved. 55 This document is subject to BCP 78 and the IETF Trust's Legal 56 Provisions Relating to IETF Documents 57 (https://trustee.ietf.org/license-info) in effect on the date of 58 publication of this document. Please review these documents 59 carefully, as they describe your rights and restrictions with respect 60 to this document. Code Components extracted from this document must 61 include Simplified BSD License text as described in Section 4.e of 62 the Trust Legal Provisions and are provided without warranty as 63 described in the Simplified BSD License. 65 Table of Contents 67 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 68 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 69 1.2. Changes from RFC7730 . . . . . . . . . . . . . . . . . . 3 70 2. Trust Anchor Locator . . . . . . . . . . . . . . . . . . . . 3 71 2.1. Trust Anchor Locator Motivation . . . . . . . . . . . . . 3 72 2.2. Trust Anchor Locator File Format . . . . . . . . . . . . 4 73 2.3. TAL and Trust Anchor Certificate Considerations . . . . . 4 74 2.4. Example . . . . . . . . . . . . . . . . . . . . . . . . . 6 75 3. Relying Party Use . . . . . . . . . . . . . . . . . . . . . . 6 76 4. URI Scheme Considerations . . . . . . . . . . . . . . . . . . 7 77 5. Security Considerations . . . . . . . . . . . . . . . . . . . 8 78 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8 79 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 8 80 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 9 81 8.1. Normative References . . . . . . . . . . . . . . . . . . 9 82 8.2. Informative References . . . . . . . . . . . . . . . . . 10 83 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10 85 1. Introduction 87 This document defines a Trust Anchor Locator (TAL) for the Resource 88 Public Key Infrastructure (RPKI) [RFC6480]. This format may be used 89 to distribute trust anchor material using a mix of out-of-band and 90 online means. Procedures used by Relying Parties (RPs) to verify 91 RPKI signed objects SHOULD support this format to facilitate 92 interoperability between creators of trust anchor material and RPs. 93 This document obsoletes [RFC7730] by adding support for HTTPS URIs 94 [RFC7230] in a TAL. 96 1.1. Terminology 98 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 99 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 100 "OPTIONAL" in this document are to be interpreted as described in BCP 101 14 [RFC2119] [RFC8174] when, and only when, they appear in all 102 capitals, as shown here. 104 1.2. Changes from RFC7730 106 The TAL format defined in this document differs from the definition 107 in [RFC7730] in that: 109 o it allows for the use of the HTTPS scheme in URIs [RFC7230]; and 111 o it allows for the inclusion of an optional comment section. 113 Note that current Relying Parties may not support this new format 114 yet. Therefore it is RECOMMENDED that a Trust Anchor operator 115 maintains a [RFC7730] TAL file for a time as well until they are 116 satisfied that RP tooling has been updated. 118 2. Trust Anchor Locator 120 2.1. Trust Anchor Locator Motivation 122 This document does not propose a new format for trust anchor 123 material. A trust anchor in the RPKI is represented by a self-signed 124 X.509 Certification Authority (CA) certificate, a format commonly 125 used in PKIs and widely supported by RP software. This document 126 specifies a format for data used to retrieve and verify the 127 authenticity of a trust anchor in a very simple fashion. That data 128 is referred to as the TAL. 130 The motivation for defining the TAL is to enable selected data in the 131 trust anchor to change, without needing to redistribute the trust 132 anchor per se. 134 In the RPKI, certificates contain an RFC3779 extension, that can 135 contain a set of IP Address Delegations and/or Autonomous System 136 Identifier Delegations. In this document we refer to these 137 delegations as the Internet Number Resources (INR) contained in an 138 RPKI certificate. 140 The set of INRs associated with an entity acting as a trust anchor is 141 likely to change over time. Thus, if one were to use the common PKI 142 convention of distributing a trust anchor to RPs in a secure fashion, 143 then this procedure would need to be repeated whenever the INR set 144 for the entity acting as a trust anchor changed. By distributing the 145 TAL (in a secure fashion), instead of distributing the trust anchor, 146 this problem is avoided, i.e., the TAL is constant so long as the 147 trust anchor's public key and its location do not change. 149 The TAL is analogous to the TrustAnchorInfo data structure specified 150 in [RFC5914], which is on the Standards Track. That specification 151 could be used to represent the TAL, if one defined an rsync or HTTPS 152 URI extension for that data structure. However, the TAL format was 153 adopted by RPKI implementors prior to the PKIX trust anchor work, and 154 the RPKI implementer community has elected to utilize the TAL format, 155 rather than define the requisite extension. The community also 156 prefers the simplicity of the ASCII encoding of the TAL, versus the 157 binary (ASN.1) encoding for TrustAnchorInfo. 159 2.2. Trust Anchor Locator File Format 161 In this document we define a Trust Anchor URI as a URI that can be 162 used to retrieved a current Trust Anchor certificate. This URI MUST 163 be either an rsync URI [RFC5781], or an HTTPS URI [RFC7230]. 165 The TAL is an ordered sequence of: 167 1. an optional comment section consisting of one or more lines each 168 starting with the '#' character, followed by human readable 169 informational UTF-8 text, conforming to the restrictions defined 170 in section 2 of [RFC5198], and ending with a line break, 172 2. a URI section, that is comprised of one or more ordered lines, 173 each containing a Trust Anchor URI, and ending with a line break, 175 3. a line break, 177 4. a subjectPublicKeyInfo [RFC5280] in DER format [X.509], encoded 178 in Base64 (see Section 4 of [RFC4648]). To avoid long lines, 179 line breaks MAY be inserted into the Base64-encoded string. 181 Note that line breaks in this file can use either "" or "". 183 2.3. TAL and Trust Anchor Certificate Considerations 185 Each Trust Anchor URI in the TAL MUST reference a single object. It 186 MUST NOT reference a directory or any other form of collection of 187 objects. The referenced object MUST be a self-signed CA certificate 188 that conforms to the RPKI certificate profile [RFC6487]. This 189 certificate is the trust anchor in certification path discovery 190 [RFC4158] and validation [RFC5280] [RFC3779]. 192 The validity interval of this trust anchor is chosen such that the 193 "notBefore" time predates the moment that this certificate is 194 published, and the "notAfter" time is after the planned time of re- 195 issuance of this certificate. 197 The INR extension(s) of this trust anchor MUST contain a non-empty 198 set of number resources. It MUST NOT use the "inherit" form of the 199 INR extension(s). The INR set described in this certificate is the 200 set of number resources for which the issuing entity is offering 201 itself as a putative trust anchor in the RPKI [RFC6480]. 203 The public key used to verify the trust anchor MUST be the same as 204 the subjectPublicKeyInfo in the CA certificate and in the TAL. 206 The trust anchor MUST contain a stable key which does not change when 207 the certificate is reissued due to changes in the INR extension(s), 208 when the certificate is renewed prior to expiration. 210 Because the public key in the TAL and the trust anchor MUST be 211 stable, this motivates operation of that CA in an offline mode. In 212 that case a subordinate CA certificate containing the same INRs, or 213 in theory any sub-set of INRs, can be issued for online operations. 214 This allows the entity that issues the trust anchor to keep the 215 corresponding private key of this certificate offline, while issuing 216 all relevant child certificates under the immediate subordinate CA. 217 This measure also allows the Certificate Revocation List (CRL) issued 218 by that entity to be used to revoke the subordinate CA certificate in 219 the event of suspected key compromise of this online operational key 220 pair that is potentially more vulnerable. 222 The trust anchor MUST be published at a stable URI. When the trust 223 anchor is reissued for any reason, the replacement CA certificate 224 MUST be accessible using the same URI. 226 Because the trust anchor is a self-signed certificate, there is no 227 corresponding CRL that can be used to revoke it, nor is there a 228 manifest [RFC6486] that lists this certificate. 230 If an entity wishes to withdraw a self-signed CA certificate as a 231 putative trust anchor, for any reason, including key rollover, the 232 entity MUST remove the object from the location referenced in the 233 TAL. 235 Where the TAL contains two or more Trust Anchor URIs, then the same 236 self-signed CA certificate MUST be found at each referenced location. 237 In order to increase operational resilience, it is RECOMMENDED that 238 the domain name parts of each of these URIs resolve to distinct IP 239 addresses that are used by a diverse set of repository publication 240 points, and these IP addresses be included in distinct Route Origin 241 Authorizations (ROAs) objects signed by different CAs. 243 2.4. Example 245 # This TAL is intended for documentation purposes only. 246 # Do not attempt to use this in a production setting. 247 rsync://rpki.example.org/rpki/hedgehog/root.cer 248 https://rpki.example.org/rpki/hedgehog/root.cer 250 MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAovWQL2lh6knDx 251 GUG5hbtCXvvh4AOzjhDkSHlj22gn/1oiM9IeDATIwP44vhQ6L/xvuk7W6 252 Kfa5ygmqQ+xOZOwTWPcrUbqaQyPNxokuivzyvqVZVDecOEqs78q58mSp9 253 nbtxmLRW7B67SJCBSzfa5XpVyXYEgYAjkk3fpmefU+AcxtxvvHB5OVPIa 254 BfPcs80ICMgHQX+fphvute9XLxjfJKJWkhZqZ0v7pZm2uhkcPx1PMGcrG 255 ee0WSDC3fr3erLueagpiLsFjwwpX6F+Ms8vqz45H+DKmYKvPSstZjCCq9 256 aJ0qANT9OtnfSDOS+aLRPjZryCNyvvBHxZXqj5YCGKtwIDAQAB 258 3. Relying Party Use 260 In order to use the TAL to retrieve and validate a (putative) trust 261 anchor, an RP SHOULD: 263 1. Retrieve the object referenced by (one of) the Trust Anchor 264 URI(s) contained in the TAL. 266 2. Confirm that the retrieved object is a current, self-signed RPKI 267 CA certificate that conforms to the profile as specified in 268 [RFC6487]. 270 3. Confirm that the public key in the TAL matches the public key in 271 the retrieved object. 273 4. Perform other checks, as deemed appropriate (locally), to ensure 274 that the RP is willing to accept the entity publishing this self- 275 signed CA certificate to be a trust anchor. These tests apply to 276 the validity of attestations made in the context of the RPKI 277 relating to all resources described in the INR extension of this 278 certificate. 280 An RP SHOULD perform these functions for each instance of TAL that it 281 is holding for this purpose every time the RP performs a 282 resynchronization across the local repository cache. In any case, an 283 RP also SHOULD perform these functions prior to the expiration of the 284 locally cached copy of the retrieved trust anchor referenced by the 285 TAL. 287 In the case where a TAL contains multiple Trust Anchor URIs, an RP 288 MAY use a locally defined preference rule to select the URI to 289 retrieve the self-signed RPKI CA certificate that is to be used as a 290 trust anchor. Some examples are: 292 o Using the order provided in the TAL 294 o Selecting the Trust Anchor URI randomly from the available list 296 o Creating a prioritized list of URIs based on RP-specific 297 parameters, such as connection establishment delay 299 If the connection to the preferred URI fails, or the retrieved CA 300 certificate public key does not match the TAL public key, the RP 301 SHOULD retrieve the CA certificate from the next URI, according to 302 the local preference ranking of URIs. 304 4. URI Scheme Considerations 306 Please note that the RSYNC protocol provides neither transport 307 security nor any means by which the Relying Party can validate that 308 they are connected to the proper host. There it is RECOMMENDED that 309 HTTPS is used as the preferred scheme. 311 Note that, although a Man in the Middle (MITM) cannot produce a CA 312 certificate that would be considered valid according to the process 313 described in Section 3, this attack can prevent that the Relying 314 Party learns about an updated CA certificate. 316 Relying Parties MUST do TLS certificate and host name validation when 317 they fetch a CA certificate using an HTTPS URI on a TAL. RPs SHOULD 318 log any TLS certificate or host name validation issues found, so that 319 an operator can investigate the cause. 321 It is RECOMMENDED that Relying Parties and Repository Servers follow 322 the Best Current Practices outlined in [RFC7525] on the use of HTTP 323 over TLS (HTTPS) [RFC7230]. Relying Parties SHOULD do TLS 324 certificate and host name validation using subjectAltName dNSName 325 identities as described in [RFC6125]. The rules and guidelines 326 defined in [RFC6125] apply here, with the following considerations: 328 o Relying Parties and Repository Servers SHOULD support the DNS-ID 329 identifier type. The DNS-ID identifier type SHOULD be present in 330 Repository Server certificates. 332 o DNS names in Repository Server certificates SHOULD NOT contain the 333 wildcard character "*". 335 o A Common Name (CN) field may be present in a Repository Server 336 certificate's subject name but SHOULD NOT be used for 337 authentication within the rules described in [RFC6125]. 339 o This protocol does not require the use of SRV-IDs. 341 o This protocol does not require the use of URI-IDs. 343 5. Security Considerations 345 Compromise of a trust anchor private key permits unauthorized parties 346 to masquerade as a trust anchor, with potentially severe 347 consequences. Reliance on an inappropriate or incorrect trust anchor 348 has similar potentially severe consequences. 350 This TAL does not directly provide a list of resources covered by the 351 referenced self-signed CA certificate. Instead, the RP is referred 352 to the trust anchor itself and the INR extension(s) within this 353 certificate. This provides necessary operational flexibility, but it 354 also allows the certificate issuer to claim to be authoritative for 355 any resource. Relying parties should either have great confidence in 356 the issuers of such certificates that they are configuring as trust 357 anchors, or they should issue their own self-signed certificate as a 358 trust anchor and, in doing so, impose constraints on the subordinate 359 certificates. 361 6. IANA Considerations 363 This document has no actions for IANA. 365 7. Acknowledgements 367 This approach to trust anchor material was originally described by 368 Robert Kisteleki. 370 The authors acknowledge the contributions of Rob Austein and Randy 371 Bush, who assisted with drafting this document and with helpful 372 review comments. 374 The authors acknowledge work of Roque Gagliano, Terry Manderson, and 375 Carlos Martinez Cagnazzo in developing the ideas behind the inclusion 376 of multiple URIs in the TAL. 378 The authors acknowledge Job Snijders for suggesting the inclusion of 379 comments at the start of the TAL. 381 8. References 383 8.1. Normative References 385 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 386 Requirement Levels", BCP 14, RFC 2119, 387 DOI 10.17487/RFC2119, March 1997, 388 . 390 [RFC3779] Lynn, C., Kent, S., and K. Seo, "X.509 Extensions for IP 391 Addresses and AS Identifiers", RFC 3779, 392 DOI 10.17487/RFC3779, June 2004, 393 . 395 [RFC4648] Josefsson, S., "The Base16, Base32, and Base64 Data 396 Encodings", RFC 4648, DOI 10.17487/RFC4648, October 2006, 397 . 399 [RFC5198] Klensin, J. and M. Padlipsky, "Unicode Format for Network 400 Interchange", RFC 5198, DOI 10.17487/RFC5198, March 2008, 401 . 403 [RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S., 404 Housley, R., and W. Polk, "Internet X.509 Public Key 405 Infrastructure Certificate and Certificate Revocation List 406 (CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008, 407 . 409 [RFC5781] Weiler, S., Ward, D., and R. Housley, "The rsync URI 410 Scheme", RFC 5781, DOI 10.17487/RFC5781, February 2010, 411 . 413 [RFC6125] Saint-Andre, P. and J. Hodges, "Representation and 414 Verification of Domain-Based Application Service Identity 415 within Internet Public Key Infrastructure Using X.509 416 (PKIX) Certificates in the Context of Transport Layer 417 Security (TLS)", RFC 6125, DOI 10.17487/RFC6125, March 418 2011, . 420 [RFC6480] Lepinski, M. and S. Kent, "An Infrastructure to Support 421 Secure Internet Routing", RFC 6480, DOI 10.17487/RFC6480, 422 February 2012, . 424 [RFC6487] Huston, G., Michaelson, G., and R. Loomans, "A Profile for 425 X.509 PKIX Resource Certificates", RFC 6487, 426 DOI 10.17487/RFC6487, February 2012, 427 . 429 [RFC7230] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer 430 Protocol (HTTP/1.1): Message Syntax and Routing", 431 RFC 7230, DOI 10.17487/RFC7230, June 2014, 432 . 434 [RFC7525] Sheffer, Y., Holz, R., and P. Saint-Andre, 435 "Recommendations for Secure Use of Transport Layer 436 Security (TLS) and Datagram Transport Layer Security 437 (DTLS)", BCP 195, RFC 7525, DOI 10.17487/RFC7525, May 438 2015, . 440 [RFC7730] Huston, G., Weiler, S., Michaelson, G., and S. Kent, 441 "Resource Public Key Infrastructure (RPKI) Trust Anchor 442 Locator", RFC 7730, DOI 10.17487/RFC7730, January 2016, 443 . 445 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 446 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 447 May 2017, . 449 [X.509] ITU-T, "The Directory: Public-key and attribute 450 certificate frameworks", October 2012. 452 8.2. Informative References 454 [RFC4158] Cooper, M., Dzambasow, Y., Hesse, P., Joseph, S., and R. 455 Nicholas, "Internet X.509 Public Key Infrastructure: 456 Certification Path Building", RFC 4158, 457 DOI 10.17487/RFC4158, September 2005, 458 . 460 [RFC5914] Housley, R., Ashmore, S., and C. Wallace, "Trust Anchor 461 Format", RFC 5914, DOI 10.17487/RFC5914, June 2010, 462 . 464 [RFC6486] Austein, R., Huston, G., Kent, S., and M. Lepinski, 465 "Manifests for the Resource Public Key Infrastructure 466 (RPKI)", RFC 6486, DOI 10.17487/RFC6486, February 2012, 467 . 469 Authors' Addresses 471 Geoff Huston 472 APNIC 474 Email: gih@apnic.net 475 URI: https://www.apnic.net 476 Samuel Weiler 477 W3C/MIT 479 Email: weiler@csail.mit.edu 481 George Michaelson 482 APNIC 484 Email: ggm@apnic.net 485 URI: https://www.apnic.net 487 Stephen Kent 488 Unaffiliated 490 Email: kent@alum.mit.edu 492 Tim Bruijnzeels 493 NLnet Labs 495 Email: tim@nlnetlabs.nl 496 URI: https://www.nlnetlabs.nl