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Kent 7 BBN 8 March 21, 2016 10 A Profile for BGPsec Router Certificates, 11 Certificate Revocation Lists, and Certification Requests 12 draft-ietf-sidr-bgpsec-pki-profiles-16 14 Abstract 16 This document defines a standard profile for X.509 certificates used 17 to enable validation of Autonomous System (AS) paths in the Border 18 Gateway Protocol (BGP), as part of an extension to that protocol 19 known as BGPsec. BGP is the standard for inter-domain routing in the 20 Internet; it is the "glue" that holds the Internet together. BGPsec 21 is being developed as one component of a solution that addresses the 22 requirement to provide security for BGP. The goal of BGPsec is to 23 provide full AS path validation based on the use of strong 24 cryptographic primitives. The end-entity (EE) certificates specified 25 by this profile are issued (to routers within an Autonomous System). 26 Each of these certificates is issued under a Resource Public Key 27 Infrastructure (RPKI) Certification Authority (CA) certificate. 28 These CA certificates and EE certificates both contain the AS 29 Identifier Delegation extension. An EE certificate of this type 30 asserts that the router(s) holding the corresponding private key are 31 authorized to emit secure route advertisements on behalf of the 32 AS(es) specified in the certificate. This document also profiles the 33 format of certification requests, and specifies Relying Party (RP) 34 certificate path validation procedures for these EE certificates. 35 This document extends the RPKI; therefore, this documents updates the 36 RPKI Resource Certificates Profile (RFC 6487). 38 Status of this Memo 40 This Internet-Draft is submitted in full conformance with the 41 provisions of BCP 78 and BCP 79. 43 Internet-Drafts are working documents of the Internet Engineering 44 Task Force (IETF). Note that other groups may also distribute 45 working documents as Internet-Drafts. The list of current Internet- 46 Drafts is at http://datatracker.ietf.org/drafts/current/. 48 Internet-Drafts are draft documents valid for a maximum of six months 49 and may be updated, replaced, or obsoleted by other documents at any 50 time. It is inappropriate to use Internet-Drafts as reference 51 material or to cite them other than as "work in progress." 53 Copyright Notice 55 Copyright (c) 2016 IETF Trust and the persons identified as the 56 document authors. All rights reserved. 58 This document is subject to BCP 78 and the IETF Trust's Legal 59 Provisions Relating to IETF Documents 60 (http://trustee.ietf.org/license-info) in effect on the date of 61 publication of this document. Please review these documents 62 carefully, as they describe your rights and restrictions with respect 63 to this document. Code Components extracted from this document must 64 include Simplified BSD License text as described in Section 4.e of 65 the Trust Legal Provisions and are provided without warranty as 66 described in the Simplified BSD License. 68 Table of Contents 70 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 71 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 72 2. Describing Resources in Certificates . . . . . . . . . . . . . 3 73 3. Updates to [RFC6487] . . . . . . . . . . . . . . . . . . . . . 5 74 3.1 BGPsec Router Certificate Fields . . . . . . . . . . . . . 5 75 3.1.1.1. Subject . . . . . . . . . . . . . . . . . . . . . 5 76 3.1.2. Subject Public Key Info . . . . . . . . . . . . . . . 5 77 3.1.3. BGPsec Router Certificate Version 3 Extension Fields . 6 78 3.1.3.1. Basic Constraints . . . . . . . . . . . . . . . . 6 79 3.1.3.2. Extended Key Usage . . . . . . . . . . . . . . . . 6 80 3.1.3.3. Subject Information Access . . . . . . . . . . . . 6 81 3.1.3.4. IP Resources . . . . . . . . . . . . . . . . . . . 6 82 3.1.3.5. AS Resources . . . . . . . . . . . . . . . . . . . 6 83 3.2. BGPsec Router Certificate Request Profile . . . . . . . . 7 84 3.3. BGPsec Router Certificate Validation . . . . . . . . . . . 7 85 4. Design Notes . . . . . . . . . . . . . . . . . . . . . . . . . 8 86 5. Security Considerations . . . . . . . . . . . . . . . . . . . 8 87 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 88 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 9 89 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9 90 8.1. Normative References . . . . . . . . . . . . . . . . . . . 9 91 8.2. Informative References . . . . . . . . . . . . . . . . . . 10 92 Appendix A. ASN.1 Module . . . . . . . . . . . . . . . . . . . . 11 93 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 11 95 1. Introduction 97 This document defines a profile for X.509 end-entity (EE) 98 certificates [RFC5280] for use in the context of certification of 99 Autonomous System (AS) paths in the Border Gateway Protocol Security 100 protocol (BGPsec). Such certificates are termed "BGPsec Router 101 Certificates". The holder of the private key associated with a 102 BGPsec Router Certificate is authorized to send secure route 103 advertisements (BGPsec UPDATEs) on behalf of the AS(es) named in the 104 certificate. A router holding the private key is authorized to send 105 route advertisements (to its peers) that contain one or more of the 106 specified AS number as the last item in the AS PATH attribute. A key 107 property provided by BGPsec is that every AS along the AS PATH can 108 verify that the other ASes along the path have authorized the 109 advertisement of the given route (to the next AS along the AS PATH). 111 This document is a profile of [RFC6487], which is a profile of 112 [RFC5280]; thus this document updates [RFC6487]. It establishes 113 requirements imposed on a Resource Certificate that is used as a 114 BGPsec Router Certificate, i.e., it defines constraints for 115 certificate fields and extensions for the certificate to be valid in 116 this context. This document also profiles the certification requests 117 used to acquire BGPsec Router Certificates. Finally, this document 118 specifies the Relying Party (RP) certificate path validation 119 procedures for these certificates. 121 1.1. Terminology 123 It is assumed that the reader is familiar with the terms and concepts 124 described in "A Profile for X.509 PKIX Resource Certificates" 125 [RFC6487], "BGPsec Protocol Specification" [ID.sidr-bgpsec-protocol], 126 "A Border Gateway Protocol 4 (BGP-4)" [RFC4271], "BGP Security 127 Vulnerabilities Analysis" [RFC4272], "Considerations in Validating 128 the Path in BGP" [RFC5123], and "Capability Advertisement with BGP-4" 129 [RFC5492]. 131 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 132 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 133 "OPTIONAL" in this document are to be interpreted as described in 134 [RFC2119]. 136 2. Describing Resources in Certificates 138 Figure 1 depicts some of the entities in the RPKI and some of the 139 products generated by RPKI entities. IANA issues a Certification 140 Authority (CA) certificate to each Regional Internet Registry (RIR). 141 The RIR, in turn, issues a CA certificate to an Internet Service 142 Providers (ISP). The ISP in turn issues EE Certificates to itself to 143 enable verification of signatures on RPKI signed objects. The CA also 144 generate. The CA also generates Certificate Revocation Lists (CRLs). 145 These CA and EE certificates are referred to as "Resource 146 Certificates", and are profiled in [RFC6487]. The [RFC6480] 147 envisioned using Resource Certificates to enable verification of 148 Manifests [RFC6486] and Route Origin Authorizations (ROAs) [RFC6482]. 149 ROAs and Manifests include the Resource Certificates used to verify 150 them. 152 +---------+ +------+ 153 | CA Cert |---| IANA | 154 +---------+ +------+ 155 \ 156 +---------+ +-----+ 157 | CA Cert |---| RIR | 158 +---------+ +-----+ 159 \ 160 +---------+ +-----+ 161 | CA Cert |---| ISP | 162 +---------+ +-----+ 163 / | | | 164 +-----+ / | | | +-----+ 165 | CRL |--+ | | +---| ROA | 166 +-----+ | | +-----+ 167 | | +----------+ 168 +----+ | +---| Manifest | 169 +-| EE |---+ +----------+ 170 | +----+ 171 +-----+ 172 Figure 1 174 This document defines another type of Resource Certificate, which is 175 referred to as a "BGPsec Router Certificate". The purpose of this 176 certificate is explained in Section 1 and falls within the scope of 177 appropriate uses defined within [RFC6484]. The issuance of BGPsec 178 Router Certificates has minimal impact on RPKI CAs because the RPKI 179 CA certificate and CRL profile remain unchanged (i.e., they are as 180 specified in [RFC6487]). Further, the algorithms used to generate 181 RPKI CA certificates that issue the BGPsec Router Certificates and 182 the CRLs necessary to check the validity of the BGPsec Router 183 Certificates remain unchanged (i.e., they are as specified in 184 [ID.sidr-rfc6485bis]). The only impact is that RPKI CAs will need to 185 be able to process a profiled certificate request (see Section 5) 186 signed with algorithms found in [ID.sidr-bgpsec-algs]. The use of 187 BGPsec Router Certificates in no way affects RPKI RPs that process 188 Manifests and ROAs because the public key found in the BGPsec Router 189 Certificate is used only to verify the signature on the BGPsec 190 certificate request (only CAs process these) and the signature on a 191 BGPsec Update Message [ID.sidr-bgpsec-protocol] (only BGPsec routers 192 process these). 194 This document enumerates only the differences between this profile 195 and the profile in [RFC6487]. Note that BGPsec Router Certificates 196 are EE certificates and as such there is no impact on process 197 described in [RFC6916]. 199 3. Updates to [RFC6487] 201 3.1 BGPsec Router Certificate Fields 203 A BGPsec Router Certificate is a valid X.509 public key certificate, 204 consistent with the PKIX profile [RFC5280], containing the fields 205 listed in this section. This profile is also based on [RFC6487] and 206 only the differences between this profile and the profile in 207 [RFC6487] are specified below. 209 3.1.1.1. Subject 211 This field identifies the router to which the certificate has been 212 issued. Consistent with [RFC6487], only two attributes are allowed 213 in the Subject field: common name and serial number. Moreover, the 214 only common name encoding options that are supported are 215 printableString and UTF8String. For BGPsec Router Certificates, it 216 is RECOMMENDED that the common name attribute contain the literal 217 string "ROUTER-" followed by the 32-bit AS Number [RFC3779] encoded 218 as eight hexadecimal digits and that the serial number attribute 219 contain the 32-bit BGP Identifier [RFC4271] (i.e., the router ID) 220 encoded as eight hexadecimal digits. If there is more than one AS 221 number, the choice of which to include in the common name is at the 222 discretion of the Issuer. If the same certificate is issued to more 223 than one router (hence the private key is shared among these 224 routers), the choice of the router ID used in this name is at the 225 discretion of the Issuer. Note that router IDs are not guaranteed to 226 be unique across the Internet, and thus the Subject name in a BGPsec 227 Router Certificate issued using this convention also is not 228 guaranteed to be unique across different issuers. However, each 229 certificate issued by an individual CA MUST contain a Subject name 230 that is unique within that context. 232 3.1.2. Subject Public Key Info 234 Refer to section 3.1 of [ID.sidr-bgpsec-algs]. 236 3.1.3. BGPsec Router Certificate Version 3 Extension Fields 238 3.1.3.1. Basic Constraints 240 BGPsec speakers are EEs; therefore, the Basic Constraints extension 241 must not be present, as per [RFC6487]. 243 3.1.3.2. Extended Key Usage 245 BGPsec Router Certificates MUST include the Extended Key Usage (EKU) 246 extension. As specified in [RFC6487] this extension MUST be marked 247 as non-critical. This document defines one EKU for BGPsec Router 248 Certificates: 250 id-kp OBJECT IDENTIFIER ::= 251 { iso(1) identified-organization(3) dod(6) internet(1) 252 security(5) mechanisms(5) pkix(7) kp(3) } 254 id-kp-bgpsec-router OBJECT IDENTIFIER ::= { id-kp 30 } 256 A BGPsec router MUST require the extended key usage extension to be 257 present in a BGPsec Router Certificate it receives. If multiple 258 KeyPurposeId values are included, the BGPsec routers need not 259 recognize all of them, as long as the required KeyPurposeId value is 260 present. BGPsec routers MUST reject certificates that do not contain 261 the BGPsec Router EKU even if they include the anyExtendedKeyUsage 262 OID defined in [RFC5280]. 264 3.1.3.3. Subject Information Access 266 This extension is not used in BGPsec Router Certificates. It MUST be 267 omitted. 269 3.1.3.4. IP Resources 271 This extension is not used in BGPsec Router Certificates. It MUST be 272 omitted. 274 3.1.3.5. AS Resources 276 Each BGPsec Router Certificate MUST include the AS Resource 277 Identifier Delegation extension, as specified in section 4.8.11 of 278 [RFC6487]. The AS Resource Identifier Delegation extension MUST 279 include one or more AS numbers, and the "inherit" element MUST NOT be 280 specified. 282 3.2. BGPsec Router Certificate Request Profile 284 Refer to section 6 of [RFC6487]. The only differences between this 285 profile and the profile in [RFC6487] are: 287 o The Basic Constraints extension: 289 If included, the CA MUST NOT honor the cA boolean if set to TRUE. 291 o The Extended Key Usage extension: 293 If included, id-kp-bgpsec-router MUST be present (see Section 294 3.1). If included, the CA MUST honor the request for id-kp- 295 bgpsec-router. 297 o The Subject Information Access extension: 299 If included, the CA MUST NOT honor the request to include the 300 extension. 302 o The SubjectPublicKeyInfo and PublicKey fields are specified in 303 [ID.sidr-bgpsec-algs]. 305 o The request is signed with the algorithms specified in [ID.sidr- 306 bgpsec-algs]. 308 3.3. BGPsec Router Certificate Validation 310 The validation procedure used for BGPsec Router Certificates is 311 identical to the validation procedure described in Section 7 of 312 [RFC6487], but using the constraints applied come from this 313 specification. For example, in step 3: "the certificate contains all 314 the field that must be present" - refers to the fields that are 315 required by this specification. 317 The differences are as follows: 319 o BGPsec Router Certificates MUST include the BGPsec Router EKU 320 defined in Section 3.1.3.2. 322 o BGPsec Router Certificates MUST NOT include the SIA extension. 324 o BGPsec Router Certificates MUST NOT include the IP Resource 325 extension. 327 o BGPsec Router Certificates MUST include the AS Resource Identifier 328 Delegation extension. 330 o BGPsec Router Certificate MUST include the "Subject Public Key 331 Info" described in [ID.sidr-bgpsec-algs] as it updates [ID.sidr- 332 rfc6485bis]. 334 NOTE: The cryptographic algorithms used by BGPsec routers are found 335 in [ID.sidr-bgpsec-algs]. Currently, the algorithms specified in 336 [ID.sidr-bgpsec-algs] and [ID.sidr-rfc6485bis] are different. BGPsec 337 RPs will need to support algorithms that are used to validate BGPsec 338 signatures as well as the algorithms that are needed to validate 339 signatures on BGPsec certificates, RPKI CA certificates, and RPKI 340 CRLs. 342 4. Design Notes 344 The BGPsec Router Certificate profile is based on the Resource 345 Certificate profile as specified in [ID.sidr-rfc6485bis]. As a 346 result, many of the design choices herein are a reflection of the 347 design choices that were taken in that prior work. The reader is 348 referred to [RFC6484] for a fuller discussion of those choices. 350 CAs are required by the Certificate Policy (CP) [RFC6484] to issue 351 properly formed BGPsec Router Certificates regardless of what is 352 present in the certification request so there is some flexibility 353 permitted in the certificate requests: 355 o BGPsec Router Certificates are always EE certificates; therefore, 356 requests to issue a CA certificate result in EE certificates; 358 o BGPsec Router Certificates are always EE certificates; therefore, 359 requests for Key Usage extension values keyCertSign and cRLSign 360 result in certificates with neither of these values; 362 o BGPsec Router Certificates always include the BGPsec Rouer EKU 363 value; therefore, request without the value result in certificates 364 with the value; and, 366 o BGPsec Router Certificates never include the Subject Information 367 Access extension; therefore, request with this extension result in 368 certificates without the extension. 370 Note that this behavior is similar to the CA including the AS 371 Resource Identifier Delegation extension in issued BGPsec Router 372 Certificates despite the fact it is not present in the request. 374 5. Security Considerations 376 The Security Considerations of [RFC6487] apply. 378 A BGPsec Router Certificate will fail RPKI validation, as defined in 379 [RFC6487], because the algorithm suite is different. Consequently, a 380 RP needs to identify the EKU to determine the appropriate Validation 381 constraint. 383 A BGPsec Router Certificate is an extension of the RPKI [RFC6480] to 384 encompass routers. It is a building block BGPsec and is used to 385 validate signatures on BGPsec Signature-Segment origination of 386 Signed-Path segments [ID.sidr-bgpsec-protocol]. Thus its essential 387 security function is the secure binding of one or more AS numbers to 388 a public key, consistent with the RPKI allocation/assignment 389 hierarchy. 391 Hash functions [ID.sidr-bgpsec-algs] are used when generating the two 392 key identifiers extension included in BGPsec certificates. However 393 as noted in [RFC6818], collision resistance is not a required 394 property of one-way hash functions when used to generate key 395 identifiers. Regardless, hash collisions are possible and if 396 detected an operator should be alerted. 398 6. IANA Considerations 400 This document makes use of two object identifiers in the SMI Registry 401 for PKIX. One is for the ASN.1 module in Appendix A and it comes 402 from the SMI Security for PKIX Module Identifier IANA registry (id- 403 mod-bgpsec-eku). The other is for the BGPsec router EKU defined in 404 Section 3.1.3.2 and Appendix A and it comes from the SMI Security for 405 PKIX Extended Key Purpose IANA registry. These OIDs were assigned 406 before management of the PKIX Arc was handed to IANA. No IANA 407 allocations are request of IANA, but please update the references in 408 those registries when this document is published by the RFC editor. 410 7. Acknowledgements 412 We would like to thank Geoff Huston, George Michaelson, and Robert 413 Loomans for their work on [RFC6487], which this work is based on. In 414 addition, the efforts of Steve Kent and Matt Lepinski were 415 instrumental in preparing this work. Additionally, we'd like to 416 thank Rob Austein, Roque Gagliano, Richard Hansen, Geoff Huston, 417 David Mandelberg, Sandra Murphy, and Sam Weiller for their reviews 418 and comments. 420 8. References 422 8.1. Normative References 424 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 425 Requirement Levels", BCP 14, RFC 2119, March 1997. 427 [RFC3779] Lynn, C., Kent, S., and K. Seo, "X.509 Extensions for IP 428 Addresses and AS Identifiers", RFC 3779, June 2004. 430 [RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A Border 431 Gateway Protocol 4 (BGP-4)", RFC 4271, January 2006. 433 [RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S., 434 Housley, R., and W. Polk, "Internet X.509 Public Key 435 Infrastructure Certificate and Certificate Revocation List 436 (CRL) Profile", RFC 5280, May 2008. 438 [RFC6487] Huston, G., Michaelson, G., and R. Loomans, "A Profile for 439 X.509 PKIX Resource Certificates", RFC 6487, February 2012. 441 [RFC6818] Yee, P., "Updates to the Internet X.509 Public Key 442 Infrastructure Certificate and Certificate Revocation List 443 (CRL) Profile", RFC 6818, January 2013. 445 [ID.sidr-rfc6485bis] G. Huston and G. Michaelson, "The Profile for 446 Algorithms and Key Sizes for use in the Resource Public Key 447 Infrastructure", draft-ietf-sidr-rfc6485bis, work-in- 448 progress. 450 [ID.sidr-bgpsec-algs] S. Turner, "BGP Algorithms, Key Formats, & 451 Signature Formats", draft-ietf-sidr-bgpsec-algs, work-in- 452 progress. 454 8.2. Informative References 456 [RFC4272] Murphy, S., "BGP Security Vulnerabilities Analysis", 457 RFC 4272, January 2006. 459 [RFC5123] White, R. and B. Akyol, "Considerations in Validating the 460 Path in BGP", RFC 5123, February 2008. 462 [RFC5492] Scudder, J. and R. Chandra, "Capabilities Advertisement 463 with BGP-4", RFC 5492, February 2009. 465 [RFC6480] Lepinski, M. and S. Kent, "An Infrastructure to Support 466 Secure Internet Routing", RFC 6480, February 2012. 468 [RFC6482] Lepinski, M., Kent, S., and D. Kong, "A Profile for Route 469 Origin Authorizations (ROAs)", RFC 6482, February 2012. 471 [RFC6484] Kent, S., Kong, D., Seo, K., and R. Watro, "Certificate 472 Policy (CP) for the Resource Public Key Infrastructure 473 (RPKI)", BCP 173, RFC 6484, February 2012. 475 [RFC6486] Austein, R., Huston, G., Kent, S., and M. Lepinski, 476 "Manifests for the Resource Public Key Infrastructure 477 (RPKI)", RFC 6486, February 2012. 479 [RFC6916] Gagliano, R., Kent, S., and S. Turner, "Algorithm Agility 480 Procedure for the Resource Public Key Infrastructure 481 (RPKI)", BCP 182, RFC 6916, April 2013. 483 [ID.sidr-bgpsec-protocol] Lepinksi, M., "BGPsec Protocol 484 Specification", draft-ietf-sidr-bgpsec-protocol, work-in- 485 progress. 487 Appendix A. ASN.1 Module 489 BGPSECEKU { iso(1) identified-organization(3) dod(6) internet(1) 490 security(5) mechanisms(5) pkix(7) id-mod(0) id-mod-bgpsec-eku(84) } 492 DEFINITIONS EXPLICIT TAGS ::= 494 BEGIN 496 -- EXPORTS ALL -- 498 -- IMPORTS NOTHING -- 500 -- OID Arc -- 502 id-kp OBJECT IDENTIFIER ::= { 503 iso(1) identified-organization(3) dod(6) internet(1) 504 security(5) mechanisms(5) kp(3) } 506 -- BGPsec Router Extended Key Usage -- 508 id-kp-bgpsec-router OBJECT IDENTIFIER ::= { id-kp 30 } 510 END 512 Authors' Addresses 514 Mark Reynolds 515 Island Peak Software 516 328 Virginia Road 517 Concord, MA 01742 519 Email: mcr@islandpeaksoftware.com 521 Sean Turner 522 IECA, Inc. 524 3057 Nutley Street, Suite 106 525 Fairfax, VA 22031 526 USA 528 EMail: turners@ieca.com 530 Stephen Kent 531 Raytheon BBN Technologies 532 10 Moulton St. 533 Cambridge, MA 02138 535 Email: kent@bbn.com