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Internet Engineering Task Force (IETF)                           G. ZornRequest for Comments: 6734                                   Network ZenCategory: Standards Track                                          Q. WuISSN: 2070-1721                                                   Huawei                                                              V. Cakulev                                                          Alcatel Lucent                                                            October 2012Diameter Attribute-Value Pairs for Cryptographic Key TransportAbstract   Some Authentication, Authorization, and Accounting (AAA) applications   require the transport of cryptographic keying material.  This   document specifies a set of Attribute-Value Pairs (AVPs) providing   native Diameter support of cryptographic key delivery.Status of This Memo   This is an Internet Standards Track document.   This document is a product of the Internet Engineering Task Force   (IETF).  It represents the consensus of the IETF community.  It has   received public review and has been approved for publication by the   Internet Engineering Steering Group (IESG).  Further information on   Internet Standards is available inSection 2 of RFC 5741.   Information about the current status of this document, any errata,   and how to provide feedback on it may be obtained athttp://www.rfc-editor.org/info/rfc6734.Copyright Notice   Copyright (c) 2012 IETF Trust and the persons identified as the   document authors.  All rights reserved.   This document is subject toBCP 78 and the IETF Trust's Legal   Provisions Relating to IETF Documents   (http://trustee.ietf.org/license-info) in effect on the date of   publication of this document.  Please review these documents   carefully, as they describe your rights and restrictions with respect   to this document.  Code Components extracted from this document must   include Simplified BSD License text as described in Section 4.e of   the Trust Legal Provisions and are provided without warranty as   described in the Simplified BSD License.Zorn, et al.                 Standards Track                    [Page 1]

RFC 6734               Diameter Key Transport AVPs          October 2012Table of Contents1. Introduction ....................................................22. Terminology .....................................................32.1. Requirements Language ......................................32.2. Technical Terms and Acronyms ...............................33. Attribute-Value Pair Definitions ................................33.1. Key AVP ....................................................33.1.1. Key-Type AVP ........................................43.1.2. Key-Name AVP ........................................43.1.3. Keying-Material AVP .................................43.1.4. Key-Lifetime AVP ....................................43.1.5. Key-SPI .............................................54. Security Considerations .........................................55. IANA Considerations .............................................55.1. AVP Codes ..................................................55.2. AVP Values .................................................56. Acknowledgements ................................................67. References ......................................................67.1. Normative References .......................................67.2. Informative References .....................................61.  Introduction   The Diameter Extensible Authentication Protocol (EAP) application   [RFC4072] defines the EAP-Master-Session-Key and EAP-Key-Name AVPs   for the purpose of transporting cryptographic keying material derived   during the execution of certain Extensible Authentication Protocol   (EAP) [RFC3748] methods (for example, EAP-TLS [RFC5216]).  At most   one instance of either of these AVPs is allowed in any Diameter   message.   However, recent work (see, for example, [RFC5295]) has specified   methods to derive other keys from the keying material created during   EAP method execution that may require transport in addition to the   Master Session Key (MSK).  Also, the EAP Re-authentication Protocol   (ERP) [RFC6696] specifies new keys that may need to be transported   between Diameter nodes.   This document specifies a set of AVPs allowing the transport of   multiple cryptographic keys in a single Diameter message.Zorn, et al.                 Standards Track                    [Page 2]

RFC 6734               Diameter Key Transport AVPs          October 20122.  Terminology2.1.  Requirements Language   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this   document are to be interpreted as described inRFC 2119 [RFC2119].2.2.  Technical Terms and Acronyms   DSRK      Domain-Specific Root Key [RFC5295].   MSK      Master Session Key [RFC3748].   rMSK      re-authentication MSK [RFC6696].  This is a per-authenticator key,      derived from the rRK (below).   rRK      re-authentication Root Key, derived from the Extended Master      Session Key (EMSK) [RFC3748] or DSRK [RFC6696].3.  Attribute-Value Pair Definitions   This section defines new AVPs for the transport of cryptographic keys   in the Diameter EAP application [RFC4072], as well as other Diameter   applications.3.1.  Key AVP   The Key AVP (AVP Code 581) is of type Grouped.  It contains the type   and keying material and, optionally, an indication of the usable   lifetime of the key, the name of the key and a Security Parameter   Index (SPI) with which the key is associated.   Key ::= < AVP Header: 581 >             < Key-Type >             { Keying-Material }             [ Key-Lifetime ]             [ Key-Name ]             [ Key-SPI ]           * [ AVP ]Zorn, et al.                 Standards Track                    [Page 3]

RFC 6734               Diameter Key Transport AVPs          October 20123.1.1.  Key-Type AVP   The Key-Type AVP (AVP Code 582) is of type Enumerated.  This AVP   identifies the type of the key being sent.  The following decimal   values are defined in this document:   DSRK (0)      A Domain-Specific Root Key [RFC5295].   rRK (1)      A re-authentication Root Key [RFC6696].   rMSK (2)      A re-authentication Master Session Key [RFC6696].   If additional values are needed, they are to be assigned by IANA   according to the policy stated inSection 5.2.3.1.2.  Key-Name AVP   The Key-Name AVP (AVP Code 586) is of type OctetString.  It contains   an opaque key identifier.  Exactly how this name is generated and   used depends on the key type and usage in question and is beyond the   scope of this document (see [RFC5247] and [RFC5295] for discussions   of key name generation in the context of EAP).3.1.3.  Keying-Material AVP   The Keying-Material AVP (AVP Code 583) is of type OctetString.  The   exact usage of this keying material depends upon several factors,   including the type of the key and the link layer in use and is beyond   the scope of this document.3.1.4.  Key-Lifetime AVP   The Key-Lifetime AVP (AVP Code 584) is of type Unsigned32 and   represents the period of time (in seconds) for which the contents of   the Keying-Material AVP (Section 3.1.3) is valid.   NOTE:      Applications using this value SHOULD consider the beginning of the      lifetime to be the point in time when the message containing the      keying material is received.  In addition, client implementations      SHOULD check to ensure that the value is reasonable; for example,      the lifetime of a key should not generally be longer than the      session lifetime (seeSection 8.13 of [RFC6733]).Zorn, et al.                 Standards Track                    [Page 4]

RFC 6734               Diameter Key Transport AVPs          October 20123.1.5.  Key-SPI   The Key-SPI AVP (AVP Code 585) is of type Unsigned32 and contains an   SPI value that can be used with other parameters for identifying   associated keying material.4.  Security Considerations   Transporting keys is a security-sensitive action.  Some forms of   keying material are already protected and can be sent safely over the   open Internet.  However, if a Key AVP contains a Keying-Material AVP   that is not already protected, then the Diameter messages containing   that Key AVP MUST only be sent protected via mutually authenticated   TLS or IPsec.   The security considerations applicable to the Diameter base protocol   [RFC6733] are also applicable to this document, as are those inSection 8.4 of RFC 4072 [RFC4072].5.  IANA Considerations   IANA has assigned values as described in the following sections.5.1.  AVP Codes   Codes have been assigned for the following AVPs using the policy   specified in[RFC6733], Section 11.1.1:   o  Key (581,Section 3.1)   o  Key-Type (582,Section 3.1.1)   o  Keying-Material (583,Section 3.1.3)   o  Key-Lifetime (584,Section 3.1.4)   o  Key-SPI (585,Section 3.1.5)   o  Key-Name (586,Section 3.1.2)5.2.  AVP Values   IANA has created a new registry for values assigned to the Key-Type   AVP and populated it with the decimal values defined in this document   (Section 3.1.1).  New values may be assigned for the Key-Type AVP   using the "Specification Required" policy [RFC5226]; once values have   been assigned, they MUST NOT be deleted, replaced, or modified.Zorn, et al.                 Standards Track                    [Page 5]

RFC 6734               Diameter Key Transport AVPs          October 20126.  Acknowledgements   Thanks (in no particular order) to Niclas Comstedt, Semyon   Mizikovsky, Hannes Tschofenig, Joe Salowey, Tom Taylor, Frank Xia,   Lionel Morand, Dan Romascanu, Bernard Aboba, Jouni Korhonen, Stephen   Farrel, Joel Halpern, Phillip Hallam-Baker, Sean Turner, and   Sebastien Decugis for useful comments, suggestions, and review.7.  References7.1.  Normative References   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate              Requirement Levels",BCP 14,RFC 2119, March 1997.   [RFC3748]  Aboba, B., Blunk, L., Vollbrecht, J., Carlson, J., and H.              Levkowetz, "Extensible Authentication Protocol (EAP)",RFC 3748, June 2004.   [RFC4072]  Eronen, P., Hiller, T., and G. Zorn, "Diameter Extensible              Authentication Protocol (EAP) Application",RFC 4072,              August 2005.   [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an              IANA Considerations Section in RFCs",BCP 26,RFC 5226,              May 2008.   [RFC6733]  Fajardo, V., Arkko, J., Loughney, J., and G. Zorn,              "Diameter Base Protocol",RFC 6733, October 2012.7.2.  Informative References   [RFC5216]  Simon, D., Aboba, B., and R. Hurst, "The EAP-TLS              Authentication Protocol",RFC 5216, March 2008.   [RFC5247]  Aboba, B., Simon, D., and P. Eronen, "Extensible              Authentication Protocol (EAP) Key Management Framework",RFC 5247, August 2008.   [RFC5295]  Salowey, J., Dondeti, L., Narayanan, V., and M. Nakhjiri,              "Specification for the Derivation of Root Keys from an              Extended Master Session Key (EMSK)",RFC 5295,              August 2008.   [RFC6696]  Cao, Z., He, B., Shi, Y., Wu, Q., Ed., and G. Zorn, Ed.,              "EAP Extensions for the EAP Re-authentication Protocol              (ERP)",RFC 6696, July 2012.Zorn, et al.                 Standards Track                    [Page 6]

RFC 6734               Diameter Key Transport AVPs          October 2012Authors' Addresses   Glen Zorn   Network Zen   227/358 Thanon Sanphawut   Bang Na, Bangkok  10260   Thailand   Phone: +66 (0) 909-201060   EMail: glenzorn@gmail.com   Qin Wu   Huawei Technologies Co., Ltd.   101 Software Avenue, Yuhua District   Nanjing, Jiangsu  21001   China   Phone: +86-25-56623633   EMail: sunseawq@huawei.com   Violeta Cakulev   Alcatel Lucent   600 Mountain Ave.   3D-517   Murray Hill, NJ  07974   US   Phone: +1 908 582 3207   EMail: violeta.cakulev@alcatel-lucent.comZorn, et al.                 Standards Track                    [Page 7]