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(See the Legal Provisions document at https://trustee.ietf.org/license-info for more information.) -- The document date (July 8, 2008) is 5065 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 323 ** 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 'Diameter') (Obsoleted by RFC 6733) == Outdated reference: draft-ietf-emu-eap-gpsk has been published as RFC 5433 == Outdated reference: draft-ietf-eap-keying has been published as RFC 5247 -- Obsolete informational reference (is this intentional?): RFC 4306 (Obsoleted by RFC 5996) Summary: 3 errors (**), 0 flaws (~~), 3 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: January 9, 2009 H. Tschofenig 6 NSN 7 P. Gutmann 8 University of Auckland 9 July 8, 2008 11 TLS using EAP Authentication 12 draft-nir-tls-eap-04.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 January 9, 2009. 39 Abstract 41 This document describes an extension to the TLS protocol to allow TLS 42 clients to authenticate with legacy credentials using the Extensible 43 Authentication Protocol (EAP). 45 This work follows the example of IKEv2, where EAP has been added to 46 the IKEv2 protocol to allow clients to use different credentials such 47 as passwords, token cards, and shared secrets. 49 When TLS is used with EAP, additional records are sent after the 50 ChangeCipherSpec protocol message and before the Finished message, 51 effectively creating an extended handshake before the application 52 layer data can be sent. Each EapMsg handshake record contains 53 exactly one EAP message. Using EAP for client authentication allows 54 TLS to be used with various AAA back-end servers such as RADIUS or 55 Diameter. 57 TLS with EAP may be used for securing a data connection such as HTTP 58 or POP3. We believe it has three main benefits: 59 o The ability of EAP to work with backend servers can remove that 60 burden from the application layer. 61 o Moving the user authentication into the TLS handshake protects the 62 presumably less secure application layer from attacks by 63 unauthenticated parties. 64 o Using mutual authentication methods within EAP can help thwart 65 certain classes of phishing attacks. 67 Table of Contents 69 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 70 1.1. EAP Applicability . . . . . . . . . . . . . . . . . . . . 5 71 1.2. Comparison with Design Alternatives . . . . . . . . . . . 5 72 1.3. Conventions Used in This Document . . . . . . . . . . . . 5 73 2. Operating Environment . . . . . . . . . . . . . . . . . . . . 6 74 3. Protocol Overview . . . . . . . . . . . . . . . . . . . . . . 7 75 3.1. The tee_supported Extension . . . . . . . . . . . . . . . 8 76 3.2. The InterimAuth Handshake Message . . . . . . . . . . . . 8 77 3.3. The EapMsg Handshake Message . . . . . . . . . . . . . . . 8 78 3.4. Calculating the Finished message . . . . . . . . . . . . . 9 79 4. Security Considerations . . . . . . . . . . . . . . . . . . . 10 80 4.1. InterimAuth vs. Finished . . . . . . . . . . . . . . . . . 10 81 4.2. Identity Protection . . . . . . . . . . . . . . . . . . . 10 82 4.3. Mutual Authentication . . . . . . . . . . . . . . . . . . 11 83 5. Performance Considerations . . . . . . . . . . . . . . . . . . 12 84 6. Operational Considerations . . . . . . . . . . . . . . . . . . 13 85 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14 86 8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 15 87 9. Changes from Previous Versions . . . . . . . . . . . . . . . . 16 88 9.1. Changes in version -02 . . . . . . . . . . . . . . . . . . 16 89 9.2. Changes in version -01 . . . . . . . . . . . . . . . . . . 16 90 9.3. Changes from the protocol model draft . . . . . . . . . . 16 91 10. Open Issues . . . . . . . . . . . . . . . . . . . . . . . . . 17 92 11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 18 93 11.1. Normative References . . . . . . . . . . . . . . . . . . . 18 94 11.2. Informative References . . . . . . . . . . . . . . . . . . 18 95 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 20 96 Intellectual Property and Copyright Statements . . . . . . . . . . 21 98 1. Introduction 100 This document describes a new extension to [TLS]. This extension 101 allows a TLS client to authenticate using [EAP] instead of performing 102 the authentication at the application level. The extension follows 103 [TLS-EXT]. For the remainder of this document we will refer to this 104 extension as TEE (TLS with EAP Extension). 106 TEE extends the TLS handshake beyond the regular setup, to allow the 107 EAP protocol to run between the TLS server (called an "authenticator" 108 in EAP) and the TLS client (called a "supplicant"). This allows the 109 TLS architecture to handle client authentication before exposing the 110 server application software to an unauthenticated client. In doing 111 this, we follow the approach taken for IKEv2 in [RFC4306]. However, 112 similar to regular TLS, we protect the user identity by only sending 113 the client identity after the server has authenticated. In this our 114 solution differs from that of IKEv2. 116 Currently used applications that rely on non-certificate user 117 credentials use TLS to authenticate the server only. After that, the 118 application takes over, and presents a login screen where the user is 119 expected to present their credentials. 121 This creates several problems. It allows a client to access the 122 application before authentication, thus creating a potential for 123 anonymous attacks on non-hardened applications. Additionally, web 124 pages are not particularly well suited for long shared secrets and 125 for interfacing with certain devices such as USB tokens. 127 TEE allows full mutual authentication to occur for all these 128 applications within the TLS exchange. The application receives 129 control only when the user is identified and authenticated. The 130 authentication can be built into the server infrastructure by 131 connecting to an AAA server. The client side can be integrated into 132 client software such as web browsers and mail clients. An EAP 133 infrastructure is already built into some operating systems providing 134 a user interface for each authentication method within EAP. 136 We intend TEE to be used for various protocols that use TLS such as 137 HTTPS, in cases where certificate based client authentication is not 138 practical. This includes web-based mail services, online banking, 139 premium content websites and mail clients. 141 Another class of applications that may see benefit from TEE are TLS 142 based VPN clients used as part of so-called "SSL VPN" products. No 143 such client protocols have so far been standardized. 145 1.1. EAP Applicability 147 Section 1.3 of [EAP] states that EAP is only applicable for network 148 access authentication, rather than for "bulk data transfer". It then 149 goes on to explain why the transport properties of EAP indeed make it 150 unsuitable for bulk data transfer, e.g. for large file transport. 151 Our proposed use of EAP falls squarely within the applicability as 152 defined, since we make no further use of EAP beyond access 153 authentication. 155 1.2. Comparison with Design Alternatives 157 It has been suggested to implement EAP authentication as part of the 158 protected application, rather than as part of the TLS handshake. A 159 BCP document could be used to describe a secure way of doing this. 160 The drawbacks we see in such an approach are listed below: 161 o EAP does not have a pre-defined transport method. Application 162 designers would need to specify an EAP transport for each 163 application. Making this a part of TLS has the benefit of a 164 single specification for all protected applications. 165 o The integration of EAP and TLS is security-sensitive and should be 166 standardized and interoperable. We do not believe that it should 167 be left to application designers to do this in a secure manner. 168 Specifically on the server-side, integration with AAA servers adds 169 complexity and is more naturally part of the underlying 170 infrastrcture. 171 o Our current proposal provides channel binding between TLS and EAP, 172 to counter the MITM attacks described in [MITM]. TLS does not 173 provide any standard way of extracting cryptographic material from 174 the TLS state, and in most implementations, the TLS state is not 175 exposed to the protected application. Because of this, it is 176 difficult for application designers to bind the user 177 authentication to the protected channel provided by TLS. 179 1.3. Conventions Used in This Document 181 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 182 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 183 document are to be interpreted as described in [RFC2119]. 185 2. Operating Environment 187 TEE will work between a client application and a server application, 188 performing either client authentication or mutual authentication 189 within the TLS exchange. 191 Client Server 192 +-------------------------+ +------------------------+ 193 | |GUI| | Client | |TLS+-+-----+-+TLS| |Server | | 194 | +-^-+ |Software| +-^-+ | +-+-^-+ |Application | | 195 | | +--------+ | | | | |Software | | 196 | | | | | | +------------+ | 197 | +-v----------------v-+ | | | | 198 | | EAP | | +---|--------------------+ 199 | | Infrastructure | | | 200 | +--------------------+ | | +--------+ 201 +-------------------------+ | | AAA | 202 | | Server | 203 +----- | 204 +--------+ 206 The above diagram shows the typical deployment. The client has 207 software that either includes a UI for some EAP methods, or else is 208 able to invoke some operating system EAP infrastructure that takes 209 care of the user interaction. The server is configured with the 210 address and protocol of the AAA server. Typically the AAA server 211 communicates using the RADIUS protocol with EAP ([RADIUS] and 212 [RAD-EAP]), or the Diameter protocol ([Diameter] and [Dia-EAP]). 214 As stated in the introduction, we expect TEE to be used in both 215 browsers and applications. Further uses may be authentication and 216 key generation for other protocols, and tunneling clients, which so 217 far have not been standardized. 219 3. Protocol Overview 221 The TEE extension defines the following: 222 o A new extension type called tee_supported, used to indicate that 223 the communicating application (either client or server) supports 224 this extension. 225 o A new message type for the handshake protocol, called InterimAuth, 226 which is used to sign previous messages. 227 o A new message type for the handshake protocol, called EapMsg, 228 which is used to carry a single EAP message. 230 The diagram below outlines the protocol structure. For illustration 231 purposes only, we use the GPSK EAP method [EAP-GPSK]. 233 Client Server 234 ------ ------ 236 ClientHello(*) --------> 237 ServerHello(*) 238 (Certificate) 239 ServerKeyExchange 240 EapMsg(Identity-Request) 241 <-------- ServerHelloDone 242 ClientKeyExchange 243 (CertificateVerify) 244 ChangeCipherSpec 245 InterimAuth 246 EapMsg(Identity-Reply) --------> 247 ChangeCipherSpec 248 InterimAuth 249 EapMsg(GPSK-Request) 250 <-------- 251 EapMsg(GPSK-Reply) --------> 252 EapMsg(GPSK-Request) 253 <-------- 254 EapMsg(GPSK-Reply) --------> 255 EapMsg(Success) 256 <-------- Finished 257 Finished --------> 259 (*) The ClientHello and ServerHello include the tee_supported 260 extension to indicate support for TEE 262 The client indicates in the first message its support for TEE. The 263 server sends an EAP identity request in the reply. The client sends 264 the identity reply after the handshake completion. The EAP request- 265 response sequence continues until the client is either authenticated 266 or rejected. 268 3.1. The tee_supported Extension 270 The tee_supported extension is a ClientHello and ServerHello 271 extension as defined in section 2.3 of [TLS-EXT]. The extension_type 272 field is TBA by IANA. The extension_data is zero-length. 274 3.2. The InterimAuth Handshake Message 276 The InterimAuth message is identical in syntax to the Finished 277 message described in section 7.4.9 of [TLS]. It is calculated in 278 exactly the same way. 280 The semantics, however, are somewhat different. The "Finished" 281 message indicates that application data may now be sent. The 282 "InterimAuth" message does not indicate this. Instead, further 283 handshake messages are needed. 285 The HandshakeType value for the InterimAuth handshake message is TBA 286 by IANA. 288 3.3. The EapMsg Handshake Message 290 The EapMsg handshake message carries exactly one EAP message as 291 defined in [EAP]. 293 The HandshakeType value for the EapMsg handshake message is TBA by 294 IANA. 296 The EapMsg message is used to tunnel EAP messages between the 297 authentication server, which may be co-located with the TLS server, 298 or else may be a separate AAA server, and the supplicant, which is 299 co-located with the TLS client. TLS on either side receives the EAP 300 data from the EAP infrastructure, and treats it as opaque. TLS does 301 not make any changes to the EAP payload or make any decisions based 302 on the contents of an EapMsg handshake message. 304 Note that it is expected that the authentication server notifies the 305 TLS server about authentication success or failure, and so TLS need 306 not inspect the eap_payload within the EapMsg to detect success or 307 failure. 309 struct { 310 opaque eap_payload[4..65535]; 311 } EapMsg; 313 eap_payload is defined in section 4 of RFC 3748. It includes 314 the Code, Identifier, Length and Data fields of the EAP 315 packet. 317 3.4. Calculating the Finished message 319 If the EAP method is key-generating (see [I-D.ietf-eap-keying]), the 320 Finished message is calculated as follows: 322 struct { 323 opaque verify_data[12]; 324 } Finished; 326 verify_data 327 PRF(MSK, finished_label, MD5(handshake_messages) + 328 SHA-1(handshake_messages)) [0..11]; 330 The finished_label and the PRF are as defined in section 7.4.9 of 331 [TLS]. 333 The handshake_messages field, unlike regular TLS, does not sign all 334 the data in the handshake. Instead it signs all the data that has 335 not been signed by the previous InterimAuth message. The 336 handshake_messages field includes all of the octets beginning with 337 and including the InterimAuth message, up to but not including this 338 Finished message. This is the concatenation of all the Handshake 339 structures exchanged thus far, and not yet signed, as defined in 340 section 7.4 of [TLS]and in this document. 342 The Master Session Key (MSK) is derived by the AAA server and by the 343 client if the EAP method is key-generating. On the server-side, it 344 is typically received from the AAA server over the RADIUS or Diameter 345 protocol. On the client-side, it is passed to TLS by some other 346 method. 348 If the EAP method is not key-generating, then the master_secret is 349 used to sign the messages instead of the MSK. For a discussion on 350 the use of such methods, see Section 4.1. 352 4. Security Considerations 354 4.1. InterimAuth vs. Finished 356 In regular TLS, the Finished message provides two functions: it signs 357 all preceding messages, and it signals that application data can now 358 be sent. In TEE, it only signs those messages that have not yet been 359 signed. 361 Some EAP methods, such as EAP-TLS, EAP-IKEv2 and EAP-SIM generate 362 keys in addition to authenticating clients. Such methods are said to 363 be resistant to man-in-the-middle (MITM) attacks as discussed in 364 [MITM]. Such methods are called key-generating methods. 366 To realize the benefit of such methods, we need to verify the key 367 that was generated within the EAP method. This is referred to as the 368 MSK in EAP. In TEE, the InterimAuth message signs all previous 369 messages with the master_secret, just like the Finished message in 370 regular TLS. The Finished message signs the rest of the messages 371 using the MSK if such exists. If not, then the messages are signed 372 with the master_secret as in regular TLS. 374 The need for signing twice arises from the fact that we need to use 375 both the master_secret and the MSK. It was possible to use just one 376 Finished record and blend the MSK into the master_secret. However, 377 this would needlessly complicate the protocol and make security 378 analysis more difficult. Instead, we have decided to follow the 379 example of IKEv2, where two AUTH payloads are exchanged. 381 It should be noted that using non-key-generating methods may expose 382 the client to a MITM attack if the same method and credentials are 383 used in some other situation, in which the EAP is done outside of a 384 protected tunnel with an authenticated server. Unless it can be 385 determined that the EAP method is never used in such a situation, 386 non-key-generating methods SHOULD NOT be used. This issue is 387 discussed extensively in [Compound-Authentication]. 389 4.2. Identity Protection 391 Unlike [TLS-PSK], TEE provides identity protection for the client. 392 The client's identity is hidden from a passive eavesdropper using TLS 393 encryption. Active attacks are discussed in Section 4.3. 395 We could save one round-trip by having the client send its identity 396 within the Client Hello message. This is similar to TLS-PSK. 397 However, we believe that identity protection is a worthy enough goal, 398 so as to justify the extra round-trip. 400 4.3. Mutual Authentication 402 In order to achieve our security goals, we need to have both the 403 server and the client authenticate. Client authentication is 404 obviously done using the EAP method. The server authentication can 405 be done in either of two ways: 406 1. The client can verify the server certificate. This may work well 407 depending on the scenario, but implies that the client or its 408 user can recognize the right DN or alternate name, and 409 distinguish it from plausible alternatives. The introduction to 410 [I.D.Webauth-phishing] shows that at least in HTTPS, this is not 411 always the case. 412 2. The client can use a mutually authenticated (MA) EAP method such 413 as GPSK. In this case, server certificate verification does not 414 matter, and the TLS handshake may as well be anonymous. Note 415 that in this case, the client identity is sent to the server 416 before server authentication. 418 To summarize: 419 o Clients MUST NOT propose anonymous ciphersuites, unless they 420 support MA EAP methods. 421 o Clients MUST NOT accept non-MA methods if the ciphersuite is 422 anonymous. 423 o Clients MUST NOT accept non-MA methods if they are not able to 424 verify the server credentials. Note that this document does not 425 define what verification involves. If the server DN is known and 426 stored on the client, verifying certificate signature and checking 427 revocation may be enough. For web browsers, the case is not as 428 clear cut, and MA methods SHOULD be used. 430 5. Performance Considerations 432 Regular TLS adds two round-trips to a TCP connection. However, 433 because of the stream nature of TCP, the client does not really need 434 to wait for the server's Finished message, and can begin sending 435 application data immediately after its own Finished message. In 436 practice, many clients do so, and TLS only adds one round-trip of 437 delay. 439 TEE adds as many round-trips as the EAP method requires. For 440 example, EAP-MD5 requires 1 round-trip, while EAP-GPSK requires 2 441 round-trips. Additionally, the client MUST wait for the EAP-Success 442 message before sending its own Finished message, so we need at least 443 3 round-trips for the entire handshake. The best a client can do is 444 two round-trips plus however many round-trips the EAP method 445 requires. 447 It should be noted, though, that these extra round-trips save 448 processing time at the application level. Two extra round-trips take 449 a lot less time than presenting a log-in web page and processing the 450 user's input. 452 It should also be noted, that TEE reverses the order of the Finished 453 messages. In regular TLS the client sends the Finished message 454 first. In TEE it is the server that sends the Finished message 455 first. This should not affect performance, and it is clear that the 456 client may send application data immediately after the Finished 457 message. 459 6. Operational Considerations 461 Section 4.3 defines a dependency between the TLS state and the EAP 462 state in that it mandates that certain EAP methods should not be used 463 with certain TLS ciphersuites. To avoid such dependencies, there are 464 two approaches that implementations can take. They can either not 465 use any anonymous ciphersuites, or else they can use only MA EAP 466 methods. 468 Where certificate validation is problematic, such as in browser-based 469 HTTPS, we recommend the latter approach. 471 In cases where the use of EAP within TLS is not known before opening 472 the connection, it is necessary to consider the implications of 473 requiring the user to type in credentials after the connection has 474 already started. TCP sessions may time out, because of security 475 considerations, and this may lead to session setup failure. 477 7. IANA Considerations 479 IANA is asked to assign an extension type value from the 480 "ExtensionType Values" registry for the tee_supported extension. 482 IANA is asked to assign two handshake message types from the "TLS 483 HandshakeType Registry", one for "EapMsg" and one for "InterimAuth". 485 8. Acknowledgments 487 The authors would like to thank Josh Howlett for his comments. 489 The TLS Inner Application Extension work ([TLS/IA]) has inspired the 490 authors to create this simplified work. TLS/IA provides a somewhat 491 different approach to integrating non-certificate credentials into 492 the TLS protocol, in addition to several other features available 493 from the RADIUS namespace. 495 The authors would also like to thank the various contributors to 496 [RFC4306] whose work inspired this one. 498 9. Changes from Previous Versions 500 9.1. Changes in version -02 502 o Added discussion of alternative designs. 504 9.2. Changes in version -01 506 o Changed the construction of the Finished message 507 o Replaced MS-CHAPv2 with GPSK in examples. 508 o Added open issues section. 509 o Added reference to [Compound-Authentication] 510 o Fixed reference to MITM attack 512 9.3. Changes from the protocol model draft 514 o Added diagram for EapMsg 515 o Added discussion of EAP applicability 516 o Added discussion of mutually-authenticated EAP methods vs other 517 methods in the security considerations. 518 o Added operational considerations. 519 o Other minor nits. 521 10. Open Issues 523 Some have suggested that since the protocol is identical to regular 524 TLS up to the InterimAuth message, we should call that the Finished 525 message, and call the last message in the extended handshake 526 something like "EapFinished". This has the advantage that the 527 construction of Finished is already well defined and will not change. 528 However, the Finished message has a specific meaning as indicated by 529 its name. It means that the handshake is over and that application 530 data can now be sent. This is not true of what is in this draft 531 called InterimAuth. We'd like the opinions of reviewrs about this 532 issue. 534 The MSK from the EAP exchange is only used to sign the Finished 535 message. It is not used again in the data encryption. In this we 536 followed the example of IKEv2. The reason is that TLS already has 537 perfectly good ways of exchanging keys, and we do not need this 538 capability from EAP methods. Also, using the MSK in keys would 539 require an additional ChangeCipherSpec and would complicate the 540 protocol. We'd like the opinions of reviewrs about this issue. 542 Another response we got was that we should have a MUST requirement 543 that only mutually authenticated and key-generating methods be used 544 in TEE. This would simplify the security considerations section. 545 While we agree that this is a good idea, most EAP methods in common 546 use are not compliant. Additionally, such requirements assume that 547 EAP packets are visible to a passive attacker. As EAP is used in 548 protected tunnels such as in L2TP, in IKEv2 and here, this assumption 549 may not be required. If we consider the server authenticated by its 550 certificate, it may be acceptable to use a non-MA method. 552 It has been suggested that identity protection is not important 553 enough to add a roundtrip, and so we should have the client send the 554 username in the ClientHello. We are not sure about how others feel 555 about this, and would like to solicit the reviewers opinion. Note 556 that if this is done, the client sends the user name before ever 557 receiving any indication that the server actually supports TEE. This 558 might be acceptable in an email client, where the server is 559 preconfigured, but it may be unacceptable in other uses, such as web 560 browsers. 562 11. References 564 11.1. Normative References 566 [EAP] Aboba, B., Blunk, L., Vollbrecht, J., Carlson, J., and H. 567 Levkowetz, "Extensible Authentication Protocol (EAP)", 568 RFC 3748, June 2004. 570 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 571 Requirement Levels", BCP 14, RFC 2119, March 1997. 573 [TLS] Dierks, T. and E. Rescorla, "The Transport Layer Security 574 (TLS) Protocol Version 1.1", RFC 4346, April 2006. 576 [TLS-EXT] Blake-Wilson, S., Nystrom, M., Hopwood, D., Mikkelsen, J., 577 and T. Wright, "Transport Layer Security (TLS) 578 Extensions", RFC 4366, April 2006. 580 11.2. Informative References 582 [Compound-Authentication] 583 Puthenkulam, J., Lortz, V., Palekar, A., and D. Simon, 584 "The Compound Authentication Binding Problem", 585 draft-puthenkulam-eap-binding-04 (work in progress), 586 October 2003. 588 [Dia-EAP] Eronen, P., Hiller, T., and G. Zorn, "Diameter Extensible 589 Authentication Protocol (EAP) Application", RFC 4072, 590 August 2005. 592 [Diameter] 593 Calhoun, P., Loughney, J., Guttman, E., Zorn, G., and J. 594 Arkko, "Diameter Base Protocol", RFC 3588, September 2003. 596 [EAP-GPSK] 597 Clancy, T. and H. Tschofenig, "EAP Generalized Pre-Shared 598 Key (EAP-GPSK)", draft-ietf-emu-eap-gpsk-05 (work in 599 progress), April 2007. 601 [I-D.ietf-eap-keying] 602 Aboba, B., "Extensible Authentication Protocol (EAP) Key 603 Management Framework", draft-ietf-eap-keying-18 (work in 604 progress), February 2007. 606 [I.D.Webauth-phishing] 607 Hartman, S., "Requirements for Web Authentication 608 Resistant to Phishing", draft-hartman-webauth-phishing-03 609 (work in progress), March 2007. 611 [MITM] Asokan, N., Niemi, V., and K. Nyberg, "Man-in-the-Middle 612 in Tunneled Authentication Protocols", IACR ePrint 613 Archive , October 2002. 615 [RAD-EAP] Aboba, B. and P. Calhoun, "RADIUS (Remote Authentication 616 Dial In User Service) Support For Extensible 617 Authentication Protocol (EAP)", RFC 3579, September 2003. 619 [RADIUS] Rigney, C., Willens, S., Rubens, A., and W. Simpson, 620 "Remote Authentication Dial In User Service (RADIUS)", 621 RFC 2865, June 2000. 623 [RFC4306] Kaufman, C., "Internet Key Exchange (IKEv2) Protocol", 624 RFC 4306, December 2005. 626 [TLS-PSK] Eronen, P. and H. Tschofenig, "Pre-Shared Key Ciphersuites 627 for Transport Layer Security (TLS)", RFC 4279, 628 December 2005. 630 [TLS/IA] Funk, P., Blake-Wilson, S., Smith, H., Tschofenig, N., and 631 T. Hardjono, "TLS Inner Application Extension (TLS/IA)", 632 draft-funk-tls-inner-application-extension-03 (work in 633 progress), June 2006. 635 Authors' Addresses 637 Yoav Nir 638 Check Point Software Technologies Ltd. 639 5 Hasolelim st. 640 Tel Aviv 67897 641 Israel 643 Email: ynir@checkpoint.com 645 Yaron Sheffer 646 Check Point Software Technologies Ltd. 647 5 Hasolelim st. 648 Tel Aviv 67897 649 Israel 651 Email: yaronf at checkpoint dot com 653 Hannes Tschofenig 654 Nokia Siemens Networks 655 Linnoitustie 6 656 Espoo 02600 657 Finland 659 Phone: +358 (50) 4871445 660 Email: Hannes.Tschofenig@gmx.net 661 URI: http://www.tschofenig.priv.at 663 Peter Gutmann 664 University of Auckland 665 Department of Computer Science 666 New Zealand 668 Email: pgut001@cs.auckland.ac.nz 670 Full Copyright Statement 672 Copyright (C) The IETF Trust (2008). 674 This document is subject to the rights, licenses and restrictions 675 contained in BCP 78, and except as set forth therein, the authors 676 retain all their rights. 678 This document and the information contained herein are provided on an 679 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS 680 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND 681 THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS 682 OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF 683 THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED 684 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 686 Intellectual Property 688 The IETF takes no position regarding the validity or scope of any 689 Intellectual Property Rights or other rights that might be claimed to 690 pertain to the implementation or use of the technology described in 691 this document or the extent to which any license under such rights 692 might or might not be available; nor does it represent that it has 693 made any independent effort to identify any such rights. 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