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(See the Legal Provisions document at https://trustee.ietf.org/license-info for more information.) -- The document date (October 14, 2007) is 5333 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) -- Looks like a reference, but probably isn't: '12' on line 330 ** Obsolete normative reference: RFC 4346 (ref. 'TLS') (Obsoleted by RFC 5246) ** Obsolete normative reference: RFC 4366 (ref. 'TLS-EXT') (Obsoleted by RFC 5246, RFC 6066) -- Obsolete informational reference (is this intentional?): RFC 3588 (ref. 'Diameter') (Obsoleted by RFC 6733) == Outdated reference: draft-ietf-emu-eap-gpsk has been published as RFC 5433 == Outdated reference: draft-ietf-eap-keying has been published as RFC 5247 == Outdated reference: A later version (-01) exists of draft-rescorla-tls-extractor-00 -- Obsolete informational reference (is this intentional?): RFC 4306 (Obsoleted by RFC 5996) Summary: 3 errors (**), 0 flaws (~~), 4 warnings (==), 10 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 TLS Working Group Y. Nir 3 Internet-Draft Y. Sheffer 4 Intended status: Standards Track Check Point 5 Expires: April 16, 2008 H. Tschofenig 6 NSN 7 P. Gutmann 8 University of Auckland 9 October 14, 2007 11 TLS using EAP Authentication 12 draft-nir-tls-eap-02.txt 14 Status of this Memo 16 By submitting this Internet-Draft, each author represents that any 17 applicable patent or other IPR claims of which he or she is aware 18 have been or will be disclosed, and any of which he or she becomes 19 aware will be disclosed, in accordance with Section 6 of BCP 79. 21 Internet-Drafts are working documents of the Internet Engineering 22 Task Force (IETF), its areas, and its working groups. Note that 23 other groups may also distribute working documents as Internet- 24 Drafts. 26 Internet-Drafts are draft documents valid for a maximum of six months 27 and may be updated, replaced, or obsoleted by other documents at any 28 time. It is inappropriate to use Internet-Drafts as reference 29 material or to cite them other than as "work in progress." 31 The list of current Internet-Drafts can be accessed at 32 http://www.ietf.org/ietf/1id-abstracts.txt. 34 The list of Internet-Draft Shadow Directories can be accessed at 35 http://www.ietf.org/shadow.html. 37 This Internet-Draft will expire on April 16, 2008. 39 Copyright Notice 41 Copyright (C) The IETF Trust (2007). 43 Abstract 45 This document describes an extension to the TLS protocol to allow TLS 46 clients to authenticate with legacy credentials using the Extensible 47 Authentication Protocol (EAP). 49 This work follows the example of IKEv2, where EAP has been added to 50 the IKEv2 protocol to allow clients to use different credentials such 51 as passwords, token cards, and shared secrets. 53 When TLS is used with EAP, additional records are sent after the 54 ChangeCipherSpec protocol message and before the Finished message, 55 effectively creating an extended handshake before the application 56 layer data can be sent. Each EapMsg handshake record contains 57 exactly one EAP message. Using EAP for client authentication allows 58 TLS to be used with various AAA back-end servers, such as RADIUS or 59 Diameter. 61 TLS with EAP may be used for securing a data connection such as HTTP 62 or POP3. We believe it has three main benefits: 63 o The ability of EAP to work with backend servers can remove that 64 burden from the application layer. 65 o Moving the user authentication into the TLS handshake protects the 66 presumably less secure application layer from attacks by 67 unauthenticated parties. 68 o Using mutual authentication methods within EAP can help thwart 69 certain classes of phishing attacks. 71 Table of Contents 73 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 74 1.1. EAP Applicability . . . . . . . . . . . . . . . . . . . . 5 75 1.2. Comparison with Design Alternatives . . . . . . . . . . . 5 76 1.3. Conventions Used in This Document . . . . . . . . . . . . 5 77 2. Operating Environment . . . . . . . . . . . . . . . . . . . . 6 78 3. Protocol Overview . . . . . . . . . . . . . . . . . . . . . . 7 79 3.1. The tee_supported Extension . . . . . . . . . . . . . . . 8 80 3.2. The InterimAuth Handshake Message . . . . . . . . . . . . 8 81 3.3. The EapMsg Handshake Message . . . . . . . . . . . . . . . 8 82 3.4. Calculating the Finished message . . . . . . . . . . . . . 9 83 4. Security Considerations . . . . . . . . . . . . . . . . . . . 10 84 4.1. InterimAuth vs. Finished . . . . . . . . . . . . . . . . . 10 85 4.2. Identity Protection . . . . . . . . . . . . . . . . . . . 10 86 4.3. Mutual Authentication . . . . . . . . . . . . . . . . . . 11 87 5. Performance Considerations . . . . . . . . . . . . . . . . . . 12 88 6. Operational Considerations . . . . . . . . . . . . . . . . . . 13 89 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14 90 8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 15 91 9. Open Issues . . . . . . . . . . . . . . . . . . . . . . . . . 16 92 10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 17 93 10.1. Normative References . . . . . . . . . . . . . . . . . . . 17 94 10.2. Informative References . . . . . . . . . . . . . . . . . . 17 95 Appendix A. Change History . . . . . . . . . . . . . . . . . . . 19 96 A.1. Changes from Previous Versions . . . . . . . . . . . . . . 19 97 A.1.1. Changes in version -02 . . . . . . . . . . . . . . . . 19 98 A.1.2. Changes in version -01 . . . . . . . . . . . . . . . . 19 99 A.1.3. Changes from the protocol model draft . . . . . . . . 19 100 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 20 101 Intellectual Property and Copyright Statements . . . . . . . . . . 21 103 1. Introduction 105 This document describes a new extension to [TLS] that allows a TLS 106 client to authenticate using [EAP] instead of performing the 107 authentication at the application layer. The extension follows 108 [TLS-EXT]. For the remainder of this document we will refer to this 109 extension as TEE (TLS with EAP Extension). 111 TEE extends the TLS handshake beyond the regular setup, to allow the 112 EAP protocol to run between the TLS server (called an "authenticator" 113 in EAP) and the TLS client (called a "supplicant"). This allows the 114 TLS architecture to handle client authentication before exposing the 115 server application software to an unauthenticated client. In doing 116 this, we follow the approach taken for IKEv2 in [RFC4306]. However, 117 similar to regular TLS, we protect the user identity by only sending 118 the client identity after the server has authenticated. In this our 119 solution differs from that of IKEv2. 121 Today, most applications that rely on symmetric credentials use TLS 122 to authenticate the server only. After that, the application takes 123 over, and presents a login screen where the user is expected to 124 present their credentials. 126 This creates several problems. It allows a client to access the 127 application before authentication, thus creating a potential for 128 anonymous attacks on non-hardened applications. Additionally, web 129 pages are not particularly well suited for long shared secrets and 130 for interfacing with certain devices such as USB tokens. 132 TEE allows full mutual authentication to occur for all these 133 applications within the TLS exchange. The application receives 134 control only when the user is identified and authenticated. The 135 authentication can be built into the server infrastructure by 136 connecting to a AAA server. The client side can be integrated into 137 client software such as web browsers and mail clients. An EAP 138 infrastructure is already built into major operating systems 139 providing a user interface for each authentication method within EAP. 141 We intend TEE to be used for various protocols that use TLS such as 142 HTTPS, in cases where certificate based client authentication is not 143 practical. This includes web-based mail services, online banking, 144 premium content websites and mail clients. 146 Another class of applications that may see benefit from TEE are TLS 147 based VPN clients used as part of so-called "SSL VPN" products. No 148 such client protocols so far has been standardized. 150 1.1. EAP Applicability 152 Section 1.3 of [EAP] states that EAP is only applicable for network 153 access authentication, rather than for "bulk data transfer". It then 154 goes on to explain why the transport properties of EAP indeed make it 155 unsuitable for bulk data transfer, e.g., for large file transport. 156 Our proposed use of EAP falls squarely within the applicability as 157 defined, since we make no further use of EAP beyond access 158 authentication. 160 1.2. Comparison with Design Alternatives 162 It has been suggested to implement EAP authentication as part of the 163 protected application, rather than as part of the TLS handshake. A 164 BCP document could be used to describe a secure way of doing this. 165 The drawbacks we see in such an approach are listed below: 166 o EAP does not have a pre-defined transport method. Application 167 designers would need to specify an EAP transport for each 168 application. Making this a part of TLS has the benefit of a 169 single specification for all protected applications. 170 o The integration of EAP and TLS is security-sensitive and should be 171 standardized and interoperable. We do not believe that it should 172 be left to application designers to do this in a secure manner. 173 Specifically on the server-side, integration with AAA servers adds 174 complexity and is more naturally part of the underlying 175 infrastrcture. 176 o Our current proposal provides channel binding between TLS and EAP, 177 to counter the MITM attacks described in [MITM]. A draft for 178 allowing applications the access to keying material produced by 179 TLS is available with [I-D.rescorla-tls-extractor]. This type of 180 interworking between the TLS stack and the application layer is 181 necessary when EAP is run outside the TLS handshake and then the 182 two exchanges need to be linked together. Since the key extractor 183 functionality is not yet available in TLS stacks it is difficult 184 for application designers to bind the user authentication to the 185 protected channel provided by TLS. 187 1.3. Conventions Used in This Document 189 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 190 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 191 document are to be interpreted as described in [RFC2119]. 193 2. Operating Environment 195 TEE will work between a client application and a server application, 196 performing either client authentication or mutual authentication 197 within the TLS exchange. 199 Client Server 200 +-------------------------+ +------------------------+ 201 | |GUI| | Client | |TLS+-+-----+-+TLS| |Server | | 202 | +-^-+ |Software| +-^-+ | +-+-^-+ |Application | | 203 | | +--------+ | | | | |Software | | 204 | | | | | | +------------+ | 205 | +-v----------------v-+ | | | | 206 | | EAP | | +---|--------------------+ 207 | | Infrastructure | | | 208 | +--------------------+ | | +--------+ 209 +-------------------------+ | | AAA | 210 | | Server | 211 +----- | 212 +--------+ 214 The above diagram shows the typical deployment. The client has 215 software that either includes a UI for some EAP methods, or else is 216 able to invoke some operating system EAP infrastructure that takes 217 care of the user interaction. The server is configured with the 218 address and protocol of the AAA server. Typically the AAA server 219 communicates using the RADIUS protocol with EAP ([RADIUS] and 220 [RAD-EAP]), or the Diameter protocol ([Diameter] and [Dia-EAP]). 222 As stated in the introduction, we expect TEE to be used in both 223 browsers and applications. Further uses may be authentication and 224 key generation for other protocols, and tunneling clients, which so 225 far have not been standardized. 227 3. Protocol Overview 229 The TEE extension defines the following: 230 o A new extension type called tee_supported, used to indicate that 231 the communicating application (either client or server) supports 232 this extension. 233 o A new message type for the handshake protocol, called InterimAuth, 234 which is used to sign previous messages. 235 o A new message type for the handshake protocol, called EapMsg, 236 which is used to carry a single EAP message. 238 The diagram below outlines the protocol structure. For illustration 239 purposes only, we use the GPSK EAP method [EAP-GPSK]. 241 Client Server 242 ------ ------ 244 ClientHello(*) --------> 245 ServerHello(*) 246 (Certificate) 247 ServerKeyExchange 248 EapMsg(Identity-Request) 249 <-------- ServerHelloDone 250 ClientKeyExchange 251 (CertificateVerify) 252 ChangeCipherSpec 253 InterimAuth 254 EapMsg(Identity-Reply) --------> 255 ChangeCipherSpec 256 InterimAuth 257 EapMsg(GPSK-Request) 258 <-------- 259 EapMsg(GPSK-Reply) --------> 260 EapMsg(GPSK-Request) 261 <-------- 262 EapMsg(GPSK-Reply) --------> 263 EapMsg(Success) 264 <-------- Finished 265 Finished --------> 267 (*) The ClientHello and ServerHello include the tee_supported 268 extension to indicate support for TEE 270 The client indicates in the first message its support for TEE. The 271 server sends an EAP identity request in the reply. The client sends 272 the identity reply after the handshake completion. The EAP request- 273 response sequence continues until the client is either authenticated 274 or rejected. 276 3.1. The tee_supported Extension 278 The tee_supported extension is a ClientHello and ServerHello 279 extension as defined in Section 2.3 of [TLS-EXT]. The extension_type 280 field is TBA by IANA. The extension_data is zero-length. 282 3.2. The InterimAuth Handshake Message 284 The InterimAuth message is identical in syntax to the Finished 285 message described in Section 7.4.9 of [TLS]. It is calculated in 286 exactly the same way. 288 The semantics, however, are somewhat different. The "Finished" 289 message indicates that application data may now be sent. The 290 "InterimAuth" message does not indicate this. Instead, further 291 handshake messages are needed. 293 The HandshakeType value for the InterimAuth handshake message is TBA 294 by IANA. 296 3.3. The EapMsg Handshake Message 298 The EapMsg handshake message carries exactly one EAP message as 299 defined in [EAP]. 301 The HandshakeType value for the EapMsg handshake message is TBA by 302 IANA. 304 The EapMsg message is used to tunnel EAP messages between the 305 authentication server, which may be co-located with the TLS server, 306 or else may be a separate AAA server, and the supplicant, which is 307 co-located with the TLS client. TLS on either side receives the EAP 308 data from the EAP infrastructure, and treats it as opaque. TLS does 309 not make any changes to the EAP payload or make any decisions based 310 on the contents of an EapMsg handshake message. 312 Note that it is expected that the EAP server notifies the TLS server 313 about authentication success or failure, and TLS does not inspect the 314 eap_payload within the EapMsg to detect success or failure. 316 struct { 317 opaque eap_payload[4..65535]; 318 } EapMsg; 320 eap_payload is defined in section 4 of RFC 3748. It includes 321 the Code, Identifier, Length and Data fields of the EAP 322 packet. 324 3.4. Calculating the Finished message 326 If the EAP method is key-generating (see [I-D.ietf-eap-keying]), the 327 Finished message is calculated as follows: 329 struct { 330 opaque verify_data[12]; 331 } Finished; 333 verify_data 334 PRF(MSK, finished_label, MD5(handshake_messages) + 335 SHA-1(handshake_messages)) [0..11]; 337 The finished_label and the PRF are as defined in Section 7.4.9 of 338 [TLS]. 340 The handshake_messages field, unlike regular TLS, does not sign all 341 the data in the handshake. Instead it signs all the data that has 342 not been signed by the previous InterimAuth message. The 343 handshake_messages field includes all of the octets beginning with 344 and including the InterimAuth message, up to but not including this 345 Finished message. This is the concatenation of all the Handshake 346 structures exchanged thus far, and not yet signed, as defined in 347 Section 7.4 of [TLS]and in this document. 349 The Master Session Key (MSK) is derived by the AAA server and by the 350 client if the EAP method is key-generating. On the server-side, it 351 is typically received from the AAA server over the RADIUS or Diameter 352 protocol. On the client-side, it is passed to TLS by some other 353 method. 355 If the EAP method is not key-generating, then the master_secret is 356 used to sign the messages instead of the MSK. For a discussion on 357 the use of such methods, see Section 4.1. 359 4. Security Considerations 361 4.1. InterimAuth vs. Finished 363 In regular TLS, the Finished message provides two functions: it signs 364 all preceding messages, and it signals that application data can now 365 be sent. In TEE, it only signs those messages that have not yet been 366 signed. 368 Some EAP methods, such as EAP-TLS, EAP-IKEv2 and EAP-SIM generate 369 keys in addition to authenticating clients. Such methods are said to 370 be resistant to man-in-the-middle (MITM) attacks as discussed in 371 [MITM]. Such methods are called key-generating methods. 373 To realize the benefit of such methods, we need to verify the key 374 that was generated within the EAP method. This is referred to as the 375 MSK in EAP. In TEE, the InterimAuth message signs all previous 376 messages with the master_secret, just like the Finished message in 377 regular TLS. The Finished message signs the rest of the messages 378 using the MSK if such exists. If not, then the messages are signed 379 with the master_secret as in regular TLS. 381 The need for signing twice arises from the fact that we need to use 382 both the master_secret and the MSK. It was possible to use just one 383 Finished record and blend the MSK into the master_secret. However, 384 this would needlessly complicate the protocol and make security 385 analysis more difficult. Instead, we have decided to follow the 386 example of IKEv2, where two AUTH payloads are exchanged. 388 It should be noted that using non-key-generating methods may expose 389 the client to a MITM attack if the same method and credentials are 390 used in some other situation, in which the EAP is done outside of a 391 protected tunnel with an authenticated server. Unless it can be 392 determined that the EAP method is never used in such a situation, 393 non-key-generating methods SHOULD NOT be used. This issue is 394 discussed extensively in [Compound-Authentication]. 396 4.2. Identity Protection 398 Unlike [TLS-PSK], TEE provides active user identity confidentiality 399 for the client. The client's identity is hidden from an active and a 400 passive eavesdropper using the server-side authenticated TLS channel 401 (followed by encryption of the EAP-based handshake messages). Active 402 attacks are discussed in Section 4.3. 404 We could save one round-trip by having the client send its identity 405 within the Client Hello message. This is similar to TLS-PSK. 406 However, we believe that identity protection is a worthy enough goal, 407 so as to justify the extra round-trip. 409 4.3. Mutual Authentication 411 In order to achieve our security goals, we need to have both the 412 server and the client authenticate. Client authentication is 413 obviously done using the EAP method. The server authentication can 414 be done in either of two ways: 415 1. The client can verify the server certificate. This may work well 416 depending on the scenario, but implies that the client or its 417 user can recognize the right DN or alternate name, and 418 distinguish it from plausible alternatives. The introduction to 419 [I.D.Webauth-phishing] shows that at least in HTTPS, this is not 420 always the case. 421 2. The client can use a mutually authenticated (MA) EAP method such 422 as GPSK. In this case, server certificate verification does not 423 matter, and the TLS handshake may as well be anonymous. Note 424 that in this case, the client identity is sent to the server 425 before server authentication. 427 To summarize: 428 o Clients MUST NOT propose anonymous ciphersuites, unless they 429 support MA EAP methods. 430 o Clients MUST NOT accept non-MA methods if the ciphersuite is 431 anonymous. 432 o Clients MUST NOT accept non-MA methods if they are not able to 433 verify the server credentials. Note that this document does not 434 define what verification involves. If the server DN is known and 435 stored on the client, verifying certificate signature and checking 436 revocation may be enough. For web browsers, the case is not as 437 clear cut, and MA methods SHOULD be used. 439 5. Performance Considerations 441 Regular TLS adds two round-trips to a TCP connection. However, 442 because of the stream nature of TCP, the client does not really need 443 to wait for the server's Finished message, and can begin sending 444 application data immediately after its own Finished message. In 445 practice, many clients do so, and TLS only adds one round-trip of 446 delay. 448 TEE adds as many round-trips as the EAP method requires. For 449 example, EAP-MD5 requires 1 round-trip, while EAP-GPSK requires 2 450 round-trips. Additionally, the client MUST wait for the EAP-Success 451 message before sending its own Finished message, so we need at least 452 3 round-trips for the entire handshake. The best a client can do is 453 two round-trips plus however many round-trips the EAP method 454 requires. 456 It should be noted, though, that these extra round-trips save 457 processing time at the application level. Two extra round-trips take 458 a lot less time than presenting a log-in web page and processing the 459 user's input. 461 It should also be noted, that TEE reverses the order of the Finished 462 messages. In regular TLS the client sends the Finished message 463 first. In TEE it is the server that sends the Finished message 464 first. This should not affect performance, and it is clear that the 465 client may send application data immediately after the Finished 466 message. 468 6. Operational Considerations 470 Section 4.3 defines a dependency between the TLS state and the EAP 471 state in that it mandates that certain EAP methods should not be used 472 with certain TLS ciphersuites. To avoid such dependencies, there are 473 two approaches that implementations can take. They can either not 474 use any anonymous ciphersuites, or else they can use only MA EAP 475 methods. 477 Where certificate validation is problematic, such as in browser-based 478 HTTPS, we recommend the latter approach. 480 In cases where the use of EAP within TLS is not known before opening 481 the connection, it is necessary to consider the implications of 482 requiring the user to type in credentials after the connection has 483 already started. TCP sessions may time out, because of security 484 considerations, and this may lead to session setup failure. 486 7. IANA Considerations 488 IANA is asked to assign an extension type value from the 489 "ExtensionType Values" registry for the tee_supported extension. 491 IANA is asked to assign two handshake message types from the "TLS 492 HandshakeType Registry", one for "EapMsg" and one for "InterimAuth". 494 8. Acknowledgments 496 The authors would like to thank Josh Howlett for his comments. 498 The TLS Inner Application Extension work ([TLS/IA]) has inspired the 499 authors to create this simplified work. TLS/IA provides a somewhat 500 different approach to integrating non-certificate credentials into 501 the TLS protocol, in addition to several other features available 502 from the RADIUS namespace. 504 The authors would also like to thank the various contributors to 505 [RFC4306] whose work inspired this one. 507 9. Open Issues 509 Some have suggested that since the protocol is identical to regular 510 TLS up to the InterimAuth message, we should call that the Finished 511 message, and call the last message in the extended handshake 512 something like "EapFinished". This has the advantage that the 513 construction of Finished is already well defined and will not change. 514 However, the Finished message has a specific meaning as indicated by 515 its name. It means that the handshake is over and that application 516 data can now be sent. This is not true of what is in this draft 517 called InterimAuth. We would like the opinions of reviewers about 518 this issue. 520 The MSK from the EAP exchange is only used to sign the Finished 521 message. It is not used again in the data encryption. In this we 522 followed the example of IKEv2. The reason is that TLS already has 523 perfectly good ways of exchanging keys, and we do not need this 524 capability from EAP methods. Also, using the MSK in keys would 525 require an additional ChangeCipherSpec and would complicate the 526 protocol. We would like the opinions of reviewers about this issue. 528 Another response we got was that we should have a MUST requirement 529 that only mutually authenticated and key generating methods be used 530 in TEE. This would simplify the security considerations section. 531 While we agree that this is a good idea, most EAP methods in common 532 use are not compliant. Additionally, such requirements assume that 533 EAP packets are visible to a passive attacker. As EAP is used in 534 protected tunnels such as in L2TP, in IKEv2 and here, this assumption 535 may not be required. If we consider the server authenticated by its 536 certificate, it may be acceptable to use a non-MA method. 538 It has been suggested that identity protection is not important 539 enough to add a roundtrip, and so we should have the client send the 540 username in the ClientHello. We are not sure about how others feel 541 about this, and would like to solicit the reviewers opinion. Note 542 that if this is done, the client sends the user name before ever 543 receiving any indication that the server actually supports TEE. This 544 might be acceptable in an email client, where the server is 545 preconfigured, but it may be unacceptable in other uses, such as web 546 browsers. 548 10. References 550 10.1. Normative References 552 [EAP] Aboba, B., Blunk, L., Vollbrecht, J., Carlson, J., and H. 553 Levkowetz, "Extensible Authentication Protocol (EAP)", 554 RFC 3748, June 2004. 556 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 557 Requirement Levels", BCP 14, RFC 2119, March 1997. 559 [TLS] Dierks, T. and E. Rescorla, "The Transport Layer Security 560 (TLS) Protocol Version 1.1", RFC 4346, April 2006. 562 [TLS-EXT] Blake-Wilson, S., Nystrom, M., Hopwood, D., Mikkelsen, J., 563 and T. Wright, "Transport Layer Security (TLS) 564 Extensions", RFC 4366, April 2006. 566 10.2. Informative References 568 [Compound-Authentication] 569 Puthenkulam, J., Lortz, V., Palekar, A., and D. Simon, 570 "The Compound Authentication Binding Problem", 571 draft-puthenkulam-eap-binding-04 (work in progress), 572 October 2003. 574 [Dia-EAP] Eronen, P., Hiller, T., and G. Zorn, "Diameter Extensible 575 Authentication Protocol (EAP) Application", RFC 4072, 576 August 2005. 578 [Diameter] 579 Calhoun, P., Loughney, J., Guttman, E., Zorn, G., and J. 580 Arkko, "Diameter Base Protocol", RFC 3588, September 2003. 582 [EAP-GPSK] 583 Clancy, T. and H. Tschofenig, "EAP Generalized Pre-Shared 584 Key (EAP-GPSK)", draft-ietf-emu-eap-gpsk-05 (work in 585 progress), April 2007. 587 [I-D.ietf-eap-keying] 588 Aboba, B., "Extensible Authentication Protocol (EAP) Key 589 Management Framework", draft-ietf-eap-keying-18 (work in 590 progress), February 2007. 592 [I-D.rescorla-tls-extractor] 593 Rescorla, E., "Keying Material Extractors for Transport 594 Layer Security (TLS)", draft-rescorla-tls-extractor-00 595 (work in progress), January 2007. 597 [I.D.Webauth-phishing] 598 Hartman, S., "Requirements for Web Authentication 599 Resistant to Phishing", draft-hartman-webauth-phishing-03 600 (work in progress), March 2007. 602 [MITM] Asokan, N., Niemi, V., and K. Nyberg, "Man-in-the-Middle 603 in Tunneled Authentication Protocols", IACR ePrint 604 Archive , October 2002. 606 [RAD-EAP] Aboba, B. and P. Calhoun, "RADIUS (Remote Authentication 607 Dial In User Service) Support For Extensible 608 Authentication Protocol (EAP)", RFC 3579, September 2003. 610 [RADIUS] Rigney, C., Willens, S., Rubens, A., and W. Simpson, 611 "Remote Authentication Dial In User Service (RADIUS)", 612 RFC 2865, June 2000. 614 [RFC4306] Kaufman, C., "Internet Key Exchange (IKEv2) Protocol", 615 RFC 4306, December 2005. 617 [TLS-PSK] Eronen, P. and H. Tschofenig, "Pre-Shared Key Ciphersuites 618 for Transport Layer Security (TLS)", RFC 4279, 619 December 2005. 621 [TLS/IA] Funk, P., Blake-Wilson, S., Smith, H., Tschofenig, N., and 622 T. Hardjono, "TLS Inner Application Extension (TLS/IA)", 623 draft-funk-tls-inner-application-extension-03 (work in 624 progress), June 2006. 626 Appendix A. Change History 628 A.1. Changes from Previous Versions 630 A.1.1. Changes in version -02 632 o Added discussion of alternative designs. 634 A.1.2. Changes in version -01 636 o Changed the construction of the Finished message 637 o Replaced MS-CHAPv2 with GPSK in examples. 638 o Added open issues section. 639 o Added reference to [Compound-Authentication] 640 o Fixed reference to MITM attack 642 A.1.3. Changes from the protocol model draft 644 o Added diagram for EapMsg 645 o Added discussion of EAP applicability 646 o Added discussion of mutually-authenticated EAP methods vs other 647 methods in the security considerations. 648 o Added operational considerations. 649 o Other minor nits. 651 Authors' Addresses 653 Yoav Nir 654 Check Point Software Technologies Ltd. 655 5 Hasolelim st. 656 Tel Aviv 67897 657 Israel 659 Email: ynir@checkpoint.com 661 Yaron Sheffer 662 Check Point Software Technologies Ltd. 663 5 Hasolelim st. 664 Tel Aviv 67897 665 Israel 667 Email: yaronf@checkpoint.com 669 Hannes Tschofenig 670 Nokia Siemens Networks 671 Otto-Hahn-Ring 6 672 Munich, Bavaria 81739 673 Germany 675 Email: Hannes.Tschofenig@siemens.com 676 URI: http://www.tschofenig.com 678 Peter Gutmann 679 University of Auckland 680 Department of Computer Science 681 New Zealand 683 Email: pgut001@cs.auckland.ac.nz 685 Full Copyright Statement 687 Copyright (C) The IETF Trust (2007). 689 This document is subject to the rights, licenses and restrictions 690 contained in BCP 78, and except as set forth therein, the authors 691 retain all their rights. 693 This document and the information contained herein are provided on an 694 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS 695 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND 696 THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS 697 OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF 698 THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED 699 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 701 Intellectual Property 703 The IETF takes no position regarding the validity or scope of any 704 Intellectual Property Rights or other rights that might be claimed to 705 pertain to the implementation or use of the technology described in 706 this document or the extent to which any license under such rights 707 might or might not be available; nor does it represent that it has 708 made any independent effort to identify any such rights. 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