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Please use uppercase 'NOT' together with RFC 2119 keywords (if that is what you mean). Found 'MUST not' in this paragraph: For deploying RFA authentication method, generated fingerprints MUST not be truncated to make those short as to preserve the relevant properties of the hash function against brute-force search attacks. -- The document date (May 27, 2014) is 3621 days in the past. Is this intentional? 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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Working Group U. Chunduri 3 Internet-Draft A. Tian 4 Intended status: Informational A. Keranen 5 Expires: November 28, 2014 Ericsson 6 T. Kivinen 7 INSIDE Secure 8 May 27, 2014 10 KARP KMP: Simplified Peer Authentication 11 draft-chunduri-karp-kmp-router-fingerprints-05 13 Abstract 15 This document describes the usage of Router Fingerprint 16 Authentication (RFA) with public keys as a potential peer 17 authentication method with KARP pair wise and group Key Management 18 Protocols (KMPs). The advantage of RFA is, it neither requires out- 19 of-band, mutually agreeable symmetric keys nor a full PKI based 20 system (trust anchor or CA certificates) for mutual authentication of 21 peers with KARP KMP deployments. Usage of Router Fingerprints give a 22 significant operational improvement from symmetric key based systems 23 and yet provide a secure authentication technique. 25 Status of This Memo 27 This Internet-Draft is submitted in full conformance with the 28 provisions of BCP 78 and BCP 79. 30 Internet-Drafts are working documents of the Internet Engineering 31 Task Force (IETF). Note that other groups may also distribute 32 working documents as Internet-Drafts. The list of current Internet- 33 Drafts is at http://datatracker.ietf.org/drafts/current/. 35 Internet-Drafts are draft documents valid for a maximum of six months 36 and may be updated, replaced, or obsoleted by other documents at any 37 time. It is inappropriate to use Internet-Drafts as reference 38 material or to cite them other than as "work in progress." 40 This Internet-Draft will expire on November 28, 2014. 42 Copyright Notice 44 Copyright (c) 2014 IETF Trust and the persons identified as the 45 document authors. All rights reserved. 47 This document is subject to BCP 78 and the IETF Trust's Legal 48 Provisions Relating to IETF Documents 49 (http://trustee.ietf.org/license-info) in effect on the date of 50 publication of this document. Please review these documents 51 carefully, as they describe your rights and restrictions with respect 52 to this document. Code Components extracted from this document must 53 include Simplified BSD License text as described in Section 4.e of 54 the Trust Legal Provisions and are provided without warranty as 55 described in the Simplified BSD License. 57 Table of Contents 59 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 60 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3 61 1.2. Acronyms . . . . . . . . . . . . . . . . . . . . . . . . 3 62 2. Router Fingerprint . . . . . . . . . . . . . . . . . . . . . 4 63 3. Usage of Router Fingerprints with KARP KMP . . . . . . . . . 5 64 4. Publishing Router Fingerprints . . . . . . . . . . . . . . . 5 65 5. Scope of Fingerprints usage with RPs . . . . . . . . . . . . 6 66 6. Fingerprint Revocation . . . . . . . . . . . . . . . . . . . 6 67 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 68 8. Security Considerations . . . . . . . . . . . . . . . . . . . 6 69 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 7 70 10. Appendix A . . . . . . . . . . . . . . . . . . . . . . . . . 7 71 10.1. Applicable Authentications methods . . . . . . . . . . . 7 72 10.1.1. Symmetric key based authentication . . . . . . . . . 7 73 10.1.2. Asymmetric key based authentication . . . . . . . . 8 74 10.1.3. EAP based authentication . . . . . . . . . . . . . . 8 75 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 9 76 11.1. Normative References . . . . . . . . . . . . . . . . . . 9 77 11.2. Informative References . . . . . . . . . . . . . . . . . 9 78 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11 80 1. Introduction 82 Usage of IKEv2[RFC5996] as the KMP for with specific extensions for 83 pair wise routing protocols (RPs) is described in [mahesh-karp-rkmp]. 84 Also IKEv2 based KMP for group keying RPs is described in [hartman- 85 karp-mrkmp]. With proliferation of authentication methods supported 86 by IKEv2, this draft explores a simple and secure peer authentication 87 method, which can be potentially used for all KARP KMP deployments. 89 Currently operators don't often change the manual keys deployed for 90 protecting RP messages because of various reasons as noted in 91 Section 2.3 of KARP threat document [RFC6862]. One of the KARP WG 92 goals is to define methods to support key changes for all RPs which 93 use either Manual Key Management (MKM) or KMP without much 94 operational overhead. 96 Apart from Peer's identity verification, authentication and parameter 97 negotiation, deployment of KMP can be more useful, when it comes to 98 rekey the keys used by RPs. Rekeying can be achieved without the 99 operator's intervention and as per the provisioned rekey policy. But 100 for operators, usage of IKEv2 KMP opens up numerous possibilities for 101 peer authentication and manual symmetric keys are not only used for 102 bootstrapping KMP, but used for peer authentication. Various other 103 peer authentication mechanisms with advantages/drawbacks of each 104 mechanism are described in the Section 10.1 of this document. 106 If symmetric pre-shared keys are used by IKEv2 KMP to authenticate 107 the peer before generating the shared key(s); apart from other issues 108 with symmetric keys, the problem still remain the same when it comes 109 to changing these keys. 111 To reduce operational costs for changing keys at peering points with 112 relatively large number of RP peers, this document describes the use 113 of one of the available IKEv2 KMP peer authentication methods with 114 raw public keys. The hash of these encoded public keys is called as 115 Router Fingerprints and the authentication method is called Router 116 Fingerprint Authentication (RFA) in rest of the document. The RFA 117 method in conjunction with KARP KMPs require, neither out-of-band 118 symmetric keys nor a fully functional PKI based system with trust 119 anchor certificates as explained further in Section 2. 121 Section 2 describes the Router Fingerprints in the context of various 122 KMPs and specifically for IKEv2 KMP. Generation and usage of the 123 Router Fingerprints is described in Section 3 and Section 4 describes 124 a reliable method for publishing the Router Fingerprints. 126 1.1. Requirements Language 128 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 129 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 130 document are to be interpreted as described in RFC 2119 [RFC2119]. 132 1.2. Acronyms 134 CRL - Certificate Revocation List. 136 EBGP - External BGP (BGP connection between external peers). 138 EE - End Entity. 140 IBGP - Internal BGP (BGP connection between internal peers). 142 KMP - Key Management Protocol (auto key management). 144 MKM - Manual Key management Protocols. 146 PAD - Peer Authorization Database. 148 RFA - Router Fingerprint Authentication. 150 RP - Routing Protocol. 152 2. Router Fingerprint 154 Router Fingerprint is a sequence of bytes used to authenticate the 155 public key before using the same public key to authenticate the peer 156 in the context of KARP KMP. 158 Various forms of fingerprint mechanisms based on the public keys are 159 already in use as defined in [RFC4252] and [RFC4253]. Fingerprints 160 are also used primarily for root key authentication in X.509 based 161 PKI [RFC5280]. This documents only highlights the usage of raw 162 public key based authentication mechanism already defined in 163 [RFC5996] for KARP deployments. 165 To generate a fingerprint: 167 1. A router needs to generate an asymmetric Private/Public key pair. 168 Asymmetric crypto algorithms based on RSA [RFC3447] or for 169 shorter and still secure keys Elliptic Curve Cryptography (ECC) 170 [RFC4492] can be used for generating the Private/Public key pair. 172 2. Once the Asymmetric key pair is generated, the public key can be 173 encoded with any additional data (specific to the router or 174 routing instance) and can be in the form of more easily 175 administrable X.509 PKI Certificate profile and to be specific as 176 specified in the SubjectPublicKeyInfo structure in Section 4.1 of 177 [RFC5280]. This does not force use of X.509 or full compliance 178 with [RFC5280] since formatting any public key as a 179 SubjectPublicKeyInfo is relatively straightforward and well 180 supported by libraries. 182 3. The result should be hashed with a cryptographic hash function, 183 preferably SHA-256 or hash functions with similar strength (see 184 more discussion on choosing preferred hash function in 185 Section 8). 187 The fingerprint generated is not a secret and can be distributed 188 publicly. This is further discussed in Section 4. 190 3. Usage of Router Fingerprints with KARP KMP 192 To use Router Fingerprints authentication with KARP KMP, a Private/ 193 Public key-pair MUST be generated by the router as specified in 194 Section 2. To deploy RFA method more widely - 196 1. type of public keys supported should be generic; for e.g., 197 support for raw Elliptic Curve public keys and 199 2. more generic encoding formats should be supported for carrying 200 the raw public keys other than currently defined PKCS #1. 202 [I-D.kivinen-ipsecme-oob-pubkey] enhances support for other types of 203 public keys and also defines new encoding format to carry the public 204 key fingerprint in the CERT payload. For RPs to use Router 205 Fingerprint Authentication in the context of IKEv2 MUST follow the 206 encoding format as specified in [I-D.kivinen-ipsecme-oob-pubkey]. 208 For RFA, the public key received is in the form of 209 SubjectPublicKeyInfo structure of X.509 PKI profile and the Peer 210 Authorization Database (PAD) entry [RFC4301] MUST contain the 211 published fingerprint of the peer. 213 4. Publishing Router Fingerprints 215 The router fingerprint generated is not a secret and can be exchanged 216 out-of-band or can be distributed publicly. Please refer to 217 Section 5 for the generic usage and scope of the RFA in routing 218 environments. In the case of inter-domain routing using EBGP 219 [RFC4271], if the routers are outside of the SIDR [I-D.ietf-sidr- 220 bgpsec-overview] environment, fingerprint can also be exchanged out- 221 of-band through Service Level Agreements (SLAs) at the RP peering 222 points. 224 [RFC6920] defines a "Named Information" identifier, which provides a 225 set of standard ways to use hash function outputs in names. As there 226 are many ways to publish fingerprints in an unambiguous manner (e.g., 227 as defined in Section 5 of [RFC4572]); on the WG consensus, KARP 228 deployments MUST use the method described in [RFC6920] for 229 interoperability. A KARP KMP deployment using router fingerprints 230 need to resort to out-of-band public key validation procedure to 231 verify authenticity of the keys being used. The router fingerprints 232 MUST be part of the KMP PAD to validate the public key received in 233 the KMP messages. 235 5. Scope of Fingerprints usage with RPs 237 The fingerprint method described in this document in general is more 238 suitable for intra domain deployments. This includes KMP usage for 239 e.g., for IBGP [RFC4271] and LDP [RFC5036] peers, where KARP KMP can 240 be deployed without having to configure either manual pre-shared keys 241 to bootstrap KMP or full PKI with trust anchor certificates. Also 242 KMPs for group keying RPs can use this method for authenticating the 243 peers in the group. This method also can be potentially used between 244 EBGP [RFC4271] speakers outside of the SIDR ([I-D.ietf-sidr-bgpsec- 245 overview]) deployment scope, where full PKI infrastructure is not 246 available to deploy with KARP KMP and at the same time, still 247 operators want to avoid provisioning manual keys. 249 6. Fingerprint Revocation 251 The idea of RFA in the context of KARP KMP is to deploy a better 252 authentication method than the mutually shared symmetric keys between 253 two routers. This SHOULD be used especially where number of peers 254 using this method is relatively smaller and operationally manageable. 255 Any changes in the router fingerprints SHOULD be administered 256 manually by the operator. For e.g., to revoke the compromised key 257 operator simply need to remove the fingerprint from the PAD, which do 258 require and update to the PAD of all possible nodes in the network 259 where this node was talking to. Quite often those configurations are 260 already pushed to routers by some kind of management tool, so it is 261 completely possible to do this quite easily. 263 When there are a large number of peers, the need for router 264 fingerprint changes may increase. This may be for reasons of key 265 compromises or other potential changes to the routers. In such 266 environments, operators SHOULD look to full PKI with trust anchor 267 certificates and CRL profiles as specified in the [RFC5280]. In this 268 context, RFA mechanism should be only seen as substantial improvement 269 from mutually shared manual keying authentication methods. 271 7. IANA Considerations 273 This document defines no new namespaces. 275 8. Security Considerations 277 If collision attacks are perceived as a threat, the hash function to 278 generate the fingerprints MUST also possess the property of 279 collision-resistance. To mitigate preimage attacks, the 280 cryptographic hash function used for a fingerprint MUST possess the 281 property of second preimage resistance. 283 For deploying RFA authentication method, generated fingerprints MUST 284 not be truncated to make those short as to preserve the relevant 285 properties of the hash function against brute-force search attacks. 287 Considering the above facts, it's recommended to use SHA-256 or 288 similar hash functions with good security properties to generate the 289 fingerprints. 291 9. Acknowledgements 293 The authors would like to thank Jari Arkko for initial and valuable 294 discussions on operationally simplified authentication methods in 295 general and RFA mechanism as described in this document in 296 particular. Authors would like to acknowledge Joel Halpern for 297 supporting this work and providing continuous feedback on the draft, 298 including the usefulness of this approach in routing environments. 300 10. Appendix A 302 10.1. Applicable Authentications methods 304 One advantage that IKEv2 provides is the largest selection of key 305 management and parameter coordination authentication methods suitable 306 for various environments. The goal of this section is to look at 307 various KMP authentication options available and recommend suitable 308 options for use in negotiating keys and other parameters for routing 309 protocol protection. 311 As some of the authentication mechanisms are optional in IKEv2, one 312 mandatory authentication mechanism from the list below needs to be 313 selected for routing environments to ensure inter-operability and 314 quicker adoption. This section attempts to summarize the available 315 options and constraints surrounding the options. 317 10.1.1. Symmetric key based authentication 319 IKEv2 [RFC5996] allows for authentication of the IKEv2 peers using a 320 symmetric pre-shared key. For symmetric pre-shared key peer 321 authentication, deployments need to consider the following as per 322 [RFC5996]: 324 1. Deriving a shared secret from a password, name, or other low- 325 entropy source is not secure. These sources are subject to 326 dictionary and social-engineering attacks, among others. 328 2. The pre-shared key should not be derived solely from a user- 329 chosen password without incorporating another source of 330 randomness. 332 3. If password-based authentication is used for bootstrapping the 333 IKE_SA, then one of the EAP methods as described in 334 Section 10.1.3 needs to be used. 336 One of the IPsecME WG charter goals is to provide IKEv2 [RFC5996] a 337 secure password authentication mechanism which is protected against 338 off-line dictionary attacks, without requiring the use of 339 certificates or Extensible Authentication Protocol (EAP), even when 340 using the low-entropy shared secrets. There are couple of documents 341 which try to address this issue and the work is still in progress. 343 10.1.2. Asymmetric key based authentication 345 Another peer authentication mechanism IKEv2 uses is asymmetric key 346 certificates or public key signatures. This approach relies on a 347 Public Key Infrastructure using X.509 (PKIX) Certificates. If this 348 can be deployed for IKEv2 peer authentication, it will be one of the 349 most secure authentication mechanisms. With this authentication 350 option, there is no need for out-of-band shared keys between peers 351 for mutual authentication. 353 Apart from RSA and DSS digital signatures for public key 354 authentication provided by IKEv2, [RFC4754] introduces Elliptic Curve 355 Digital Signature Algorithm (ECDSA) signatures. ECDSA provides 356 additional benefits including computational efficiency, small 357 signature sizes, and minimal bandwidth compared to other available 358 digital signature methods. 360 10.1.3. EAP based authentication 362 In addition to supporting authentication using shared secrets and 363 public key signatures, IKEv2 also supports authentication based on 364 the Extensible Authentication Protocol (EAP), defined in [RFC3748]. 365 EAP is an authentication framework that supports multiple 366 authentication mechanisms. IKEv2 provides EAP authentication because 367 public key signatures and shared secrets are not flexible enough to 368 meet the requirements of many deployment scenarios. For KARP KMP, 369 EAP-Only Authentication in IKEv2 as specified in [RFC5998] can be 370 explored. 372 By using EAP, IKEv2 KMP can leverage existing authentication 373 infrastructure and credential databases, because EAP allows users to 374 choose a method suitable for existing credentials. Routing protocols 375 today use password-based pre-shared keys to integrity protect the 376 routing protocol messages. The same pre-shared key can be used to 377 bootstrap the KMP and as a potential authentication key in KMP. With 378 appropriate password based EAP methods, stronger keys can be 379 generated without using certificates. 381 For authenticating the nodes running routing protocols, EAP and the 382 IKEv2 endpoints are co-located (so no separate EAP server required). 383 When EAP is deployed, authenticating the IKEv2 responder using both 384 EAP and public key signatures could be redundant. EAP methods that 385 offer mutual authentication and key agreement can be used to provide 386 responder authentication in IKEv2 completely based on EAP. 388 Section 4 of [RFC5998] lists safe EAP methods to support 389 EAP_ONLY_AUTHENTICATION. For routing protocols deployment, because 390 an EAP server is co-located with IKEv2 responder, channel binding 391 capability of the selected EAP method is irrelevant. Various 392 qualified mutual authentication methods are listed in [RFC5998]; of 393 these, a password based methods [RFC4746], [RFC5931], [RFC6124] can 394 offer potential EAP alternative for pre-shared key only 395 authentication. 397 11. References 399 11.1. Normative References 401 [I-D.chunduri-karp-using-ikev2-with-tcp-ao] 402 Chunduri, U., Tian, A., and J. Touch, "A framework for RPs 403 to use IKEv2 KMP", draft-chunduri-karp-using-ikev2-with- 404 tcp-ao-06 (work in progress), February 2014. 406 [I-D.kivinen-ipsecme-oob-pubkey] 407 Kivinen, T., Wouters, P., and H. Tschofenig, "More Raw 408 Public Keys for IKEv2", draft-kivinen-ipsecme-oob- 409 pubkey-07 (work in progress), May 2014. 411 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 412 Requirement Levels", BCP 14, RFC 2119, March 1997. 414 [RFC5996] Kaufman, C., Hoffman, P., Nir, Y., and P. Eronen, 415 "Internet Key Exchange Protocol Version 2 (IKEv2)", RFC 416 5996, September 2010. 418 11.2. Informative References 420 [I-D.hartman-karp-mrkmp] 421 Hartman, S., Zhang, D., and G. Lebovitz, "Multicast Router 422 Key Management Protocol (MaRK)", draft-hartman-karp- 423 mrkmp-05 (work in progress), September 2012. 425 [I-D.ietf-karp-ops-model] 426 Hartman, S. and D. Zhang, "Operations Model for Router 427 Keying", draft-ietf-karp-ops-model-10 (work in progress), 428 January 2014. 430 [I-D.ietf-sidr-bgpsec-overview] 431 Lepinski, M. and S. Turner, "An Overview of BGPSEC", 432 draft-ietf-sidr-bgpsec-overview-04 (work in progress), 433 December 2013. 435 [I-D.mahesh-karp-rkmp] 436 Jethanandani, M., Weis, B., Patel, K., Zhang, D., Hartman, 437 S., Chunduri, U., Tian, A., and J. Touch, "Negotiation for 438 Keying Pairwise Routing Protocols in IKEv2", draft-mahesh- 439 karp-rkmp-05 (work in progress), November 2013. 441 [RFC3447] Jonsson, J. and B. Kaliski, "Public-Key Cryptography 442 Standards (PKCS) #1: RSA Cryptography Specifications 443 Version 2.1", RFC 3447, February 2003. 445 [RFC3618] Fenner, B. and D. Meyer, "Multicast Source Discovery 446 Protocol (MSDP)", RFC 3618, October 2003. 448 [RFC3748] Aboba, B., Blunk, L., Vollbrecht, J., Carlson, J., and H. 449 Levkowetz, "Extensible Authentication Protocol (EAP)", RFC 450 3748, June 2004. 452 [RFC4107] Bellovin, S. and R. Housley, "Guidelines for Cryptographic 453 Key Management", BCP 107, RFC 4107, June 2005. 455 [RFC4252] Ylonen, T. and C. Lonvick, "The Secure Shell (SSH) 456 Authentication Protocol", RFC 4252, January 2006. 458 [RFC4253] Ylonen, T. and C. Lonvick, "The Secure Shell (SSH) 459 Transport Layer Protocol", RFC 4253, January 2006. 461 [RFC4271] Rekhter, Y., Li, T., and S. Hares, "A Border Gateway 462 Protocol 4 (BGP-4)", RFC 4271, January 2006. 464 [RFC4301] Kent, S. and K. Seo, "Security Architecture for the 465 Internet Protocol", RFC 4301, December 2005. 467 [RFC4492] Blake-Wilson, S., Bolyard, N., Gupta, V., Hawk, C., and B. 468 Moeller, "Elliptic Curve Cryptography (ECC) Cipher Suites 469 for Transport Layer Security (TLS)", RFC 4492, May 2006. 471 [RFC4572] Lennox, J., "Connection-Oriented Media Transport over the 472 Transport Layer Security (TLS) Protocol in the Session 473 Description Protocol (SDP)", RFC 4572, July 2006. 475 [RFC4746] Clancy, T. and W. Arbaugh, "Extensible Authentication 476 Protocol (EAP) Password Authenticated Exchange", RFC 4746, 477 November 2006. 479 [RFC4754] Fu, D. and J. Solinas, "IKE and IKEv2 Authentication Using 480 the Elliptic Curve Digital Signature Algorithm (ECDSA)", 481 RFC 4754, January 2007. 483 [RFC5036] Andersson, L., Minei, I., and B. Thomas, "LDP 484 Specification", RFC 5036, October 2007. 486 [RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S., 487 Housley, R., and W. Polk, "Internet X.509 Public Key 488 Infrastructure Certificate and Certificate Revocation List 489 (CRL) Profile", RFC 5280, May 2008. 491 [RFC5440] Vasseur, JP. and JL. Le Roux, "Path Computation Element 492 (PCE) Communication Protocol (PCEP)", RFC 5440, March 493 2009. 495 [RFC5931] Harkins, D. and G. Zorn, "Extensible Authentication 496 Protocol (EAP) Authentication Using Only a Password", RFC 497 5931, August 2010. 499 [RFC5998] Eronen, P., Tschofenig, H., and Y. Sheffer, "An Extension 500 for EAP-Only Authentication in IKEv2", RFC 5998, September 501 2010. 503 [RFC6124] Sheffer, Y., Zorn, G., Tschofenig, H., and S. Fluhrer, "An 504 EAP Authentication Method Based on the Encrypted Key 505 Exchange (EKE) Protocol", RFC 6124, February 2011. 507 [RFC6518] Lebovitz, G. and M. Bhatia, "Keying and Authentication for 508 Routing Protocols (KARP) Design Guidelines", RFC 6518, 509 February 2012. 511 [RFC6862] Lebovitz, G., Bhatia, M., and B. Weis, "Keying and 512 Authentication for Routing Protocols (KARP) Overview, 513 Threats, and Requirements", RFC 6862, March 2013. 515 [RFC6920] Farrell, S., Kutscher, D., Dannewitz, C., Ohlman, B., 516 Keranen, A., and P. Hallam-Baker, "Naming Things with 517 Hashes", RFC 6920, April 2013. 519 Authors' Addresses 520 Uma Chunduri 521 Ericsson 522 300 Holger Way 523 San Jose, California 95134 524 USA 526 Phone: +1 (408) 750-5678 527 Email: uma.chunduri@ericsson.com 529 Albert Tian 530 Ericsson 531 300 Holger Way 532 San Jose, California 95134 533 USA 535 Phone: +1 (408) 750-5210 536 Email: albert.tian@ericsson.com 538 Ari Keranen 539 Ericsson 540 Hirsalantie 11 541 Jorvas 02420 542 Finland 544 Email: ari.keranen@ericsson.com 546 Tero Kivinen 547 INSIDE Secure 548 Eerikinkatu 28 549 Helsinki 00180 550 Finland 552 Email: kivinen@iki.fi