Internet Engineering Task Force M. Badra LIMOS Laboratory Expires: July 2007 January 23, 2007 EAP Peer Credential Protection Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on July 2, 2007. Copyright Notice Copyright (C) The Internet Society (2007). All Rights Reserved. Abstract Actual EAP methods provide authentication services based on the use of certificates, secret keys or passwords. These methods, excepting the tunneling ones, exchange peer identity in clear text. Moreover, some of these methods do not enable the ability to exchange channel binding information. They do not, however, define a common encoding of the credential protection or of the channel binding or of. This document defines AVPs to securely exchange data related to the peer identity, when an EAP method deriving keys is deployed. Badra Expires July 2007 [Page 1] Internet-draft EAP Peer Credential Protection January 2007 1 Introduction It is required that EAP methods deriving keys provides for mutual authentication between the EAP peer and the EAP server. Peer authentication requires exchanging data related to their identity. Even though EAP tunneled authentication protocols protect such data, existing widely deployed EAP methods such as EAP-TLS are not able to protect data related to the peer identity. Actual EAP methods provide authentication services based on the use of certificates, secret keys or passwords. Except EAP tunneled authentication protocols, these methods exchange peer identity in clear text. According to RFC 3748, EAP methods SHOULD have the ability to derive exportable keying material. This document defines a set of AVPs transporting identity related data, and securely exchanges them using the derived key. Attribute-value pairs (AVPs) provide a way to exchange arbitrary information between peer and EAP server within a secure channel. This document defines two AVPs (AVP Code TBS): AVP Identity- Protection-Certificate and AVP Identity-Protection-Sharedkey to carry data related to the peer identity. It is defined as following: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | AVP Code (TBS) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | AVP Length | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Data... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The Data field of each AVP in the format is described in Section 2. 1.2 Requirements language The key words "MUST", "MUST NOT" and "MAY" in this document are to be interpreted as described in RFC-2119. 2 EAP methods with authentication based on certificates For EAP methods requiring authentication based on certificates (e.g. EAP-TLS) initially establishes a server authentication and then exchanges an AVP of type Identity-Protection-Certificate carrying data related to the peer identity, as long as an evidence proving Badra Expires July 2007 [Page 2] Internet-draft EAP Peer Credential Protection January 2007 the identity of the peer that holds the certificate and the corresponding private key. The evidence used here is the same defined by the security protocol itself (e.g. IKE2, TLS, etc.). 2.1 AVP Data field: case EAP-TLS In the case of EAP-TLS, the peer sends the AVP Identity-Protection- Certificate once the TLS Handshake is complete. The AVP data content is the same of the TLS certificate verify message that defined in RFC 2246. The AVP MUST be sent immediately after exchanging the TLS finished messages. The server that sends the TLS certificate request message MAY deny the peer access in the case where the peer does not transmit an AVP carrying a valid certificate. The following sequence illustrates the operation of the EAP-TLS protocol with AVP Identity-Protection-Certificate. Peer Authenticator | | | PPP EAP-Request/ | | EAP-Type=EAP-TLS | | (TLS Start) | |<-----------------------------------------------------| | | | PPP EAP-Response/ | | EAP-Type=EAP-TLS | | (TLS client_hello) | |----------------------------------------------------->| | | | PPP EAP-Request/ | | EAP-Type=EAP-TLS | | (TLS server_hello | | TLS certificate, | | [TLS server_key_exchange,] | | [TLS certificate_request,] | | TLS server_hello_done) | |<-----------------------------------------------------| | | | PPP EAP-Response/ | | EAP-Type=EAP-TLS | | (TLS client_key_exchange, | | TLS change_cipher_spec, | | TLS finished) | |----------------------------------------------------->| Badra Expires July 2007 [Page 3] Internet-draft EAP Peer Credential Protection January 2007 | | | PPP EAP-Request/ | | EAP-Type=EAP-TLS | | (TLS change_cipher_spec, | | TLS finished) | |<-----------------------------------------------------| | | | PPP EAP-Response/ | | EAP-Type=EAP-TLS | | (AVP | | [TLS certificate, | | TLS certificate_verify]) | |----------------------------------------------------->| | | | PPP EAP-Success | |<-----------------------------------------------------| 2 EAP methods with authentication based on shared keys Many EAP methods use shared key and passwords to establish a mutual authentication as long as to derive material keys. A set of these methods, such as EAP-AKA and EAP-SIM uses pseudonym approach allowing the peer to use a fresh identity/key if the peers wish to avoid having their identity unprotected. Two cases MAY be takes with pseudonym management: 1- centralised authentication server 2- decentralised authentication server. This document does not consider the decentralised authentication server case, due to existing deployment reasons. The pseudonym management in this document consists of sharing two identities with two shared key; the first is permanent and the second is ephemeral. When an EAP method based on shared key is deployed, the peer will use the ephemeral identity during the authentication phase. If the server does not recognise the peer ephemeral identity, both the peer and the server reuse the permanent identity. At the end of the EAP method exchange, the server will send to the peer an AVP Identity-Protection-Sharedkey carrying a new identity and a new shared key. Thus, EAP methods implementing the AVP defined by this document MUST replace the ephemeral identity with the identity transmitted by the server. Badra Expires July 2007 [Page 4] Internet-draft EAP Peer Credential Protection January 2007 The following exchanges show where the server does not recognises the peer ephemeral identity: Peer Authenticator | | | PPP EAP-Request/ | | EAP-Type=XXX | | (XXX massages) | |<---------------------------------------------------------| | | | PPP EAP-Response/ | | EAP-Type=XXX | | (XXX messages | Ephemeral ID) | |--------------------------------------------------------->| | | | PPP EAP-Request/ | | EAP-Type=XXX | | (XXX massages | | Alert: Unrecognized ID) | |<---------------------------------------------------------| | | | (XXX messages | | Permanent ID) | |--------------------------------------------------------->| | | | .. sequence of EAP-Request/Response with EAP-Type=XXX .. | |<-------------------------------------------------------->| | | | PPP EAP-Request/ | | EAP-Type=XXX | | (XXX massages | | (AVP | | [Ephemeral ID, | | shared key]) | |<---------------------------------------------------------| | | | PPP EAP-Response/ | | EAP-Type=XXX | |--------------------------------------------------------->| | | | PPP EAP-Success | |<---------------------------------------------------------| Badra Expires July 2007 [Page 5] Internet-draft EAP Peer Credential Protection January 2007 The following exchanges show where the server recognises the peer ephemeral identity: Peer Authenticator | | | PPP EAP-Request/ | | EAP-Type=XXX | | (XXX massages) | |<---------------------------------------------------------| | | | PPP EAP-Response/ | | EAP-Type=XXX | | (XXX messages | Ephemeral ID) | |--------------------------------------------------------->| | | | .. sequence of EAP-Request/Response with EAP-Type=XXX .. | |<-------------------------------------------------------->| | | | PPP EAP-Request/ | | EAP-Type=XXX | | (XXX massages | | (AVP | | [Ephemeral ID, | | shared key]) | |<---------------------------------------------------------| | | | PPP EAP-Response/ | | EAP-Type=XXX | |--------------------------------------------------------->| | | | PPP EAP-Success | |<---------------------------------------------------------| 7 Security Considerations The security considerations described throughout [TLS] and [EAPTLS] apply here as well. References [TLS] Dierks, T. and C. Allen "The TLS Protocol Version 1.0", RFC 2246, January 1999. [EAP] Aboba, B., et. al., "PPP Extensible Authentication Protocol EAP)", RFC 3748, June 2004. [EAPTLS] Aboba, B., and D., Simon, "PPP EAP TLS Authentication Protocol", RFC 2716, October 1999. Badra Expires July 2007 [Page 6] Internet-draft EAP Peer Credential Protection January 2007 Author's Addresses Mohamad Badra LIMOS Laboratory - UMR (6158), CNRS France Email: badra@isima.fr Intellectual Property Statement The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; nor does it represent that it has made any independent effort to identify any such rights. 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Disclaimer of Validity This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Copyright Statement Copyright (C) The Internet Society (2007). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. Acknowledgment Badra Expires July 2007 [Page 7] Internet-draft EAP Peer Credential Protection January 2007 Funding for the RFC Editor function is currently provided by the Internet Society. Badra Expires July 2007 [Page 8]