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ABFAB                                                        Y. Wei, Ed.
Internet-Draft                                           ZTE Corporation
Intended status: Informational                            March 12, 2012
Expires: September 13, 2012


                      Federated Cross-Layer Access
                        draft-wei-abfab-fcla-02

Abstract

   Network stratum and application stratum form a federation to
   faciliate user's access.  Network operator acts as Identity Provider
   (IdP), and application reuses underlying network's security
   capabilities to simlify application's access.  This document is to
   introduce such federated cross-layer access use case and message
   flows.

Status of this Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on September 13, 2012.

Copyright Notice

   Copyright (c) 2012 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as



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   described in the Simplified BSD License.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Related Work . . . . . . . . . . . . . . . . . . . . . . . . .  3
   3.  Use Case . . . . . . . . . . . . . . . . . . . . . . . . . . .  4
   4.  Message Flow . . . . . . . . . . . . . . . . . . . . . . . . .  5
     4.1.  Fast Re-authentication . . . . . . . . . . . . . . . . . .  5
     4.2.  Secure Data Sharing  . . . . . . . . . . . . . . . . . . .  7
   5.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 10
   6.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 10
   7.  Security Considerations  . . . . . . . . . . . . . . . . . . . 10
   8.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 10
     8.1.  Normative References . . . . . . . . . . . . . . . . . . . 10
     8.2.  Informative References . . . . . . . . . . . . . . . . . . 10
   Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 12

































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1.  Introduction

   Currently it is agreed that digital identity is a crucial element in
   a service enviroment.  Typically telecom operators provide access
   customers with identity which is associated with some form of trusted
   element on the network (e.g.  SIM/UICC).  Meanwhile the identity
   required by Web or non-Web services for users on is usually
   associated with username.

   Ordinarly telecom operators have tens of millons of users and can
   provide trusted identity and higher security.  However the categories
   of service provided by telecom operators are relatively few.  On the
   contrary most service providers on the Internet have limited amount
   of users and can not assure the security of user identity, but they
   can provide abundant kinds of service.  Furthermore, user is
   reluntant to register too many accounts because it is inconvenient to
   remember dozens of passwords .  These facts creates some driving
   forces that telecom is interworking with Internet.  The stakeholders
   can benifit from these combination.  For telecom operators, they can
   provide identity service, trusted security service, mobile payment
   service and sharing some user profiles according user's preferences.
   Telecom operators is not just providing pipeine for communication,
   but also become a part of service value chain.  For service
   providers, they can focus on core business and reuse capabilities
   provided by telecom operators without worring about sources of users.
   For end users, they can enjoy seamless service experiences and
   improve security and privacy.

   This document considers a use case which telecom operator acts as
   Identity provider (IdP) and federates with non-Web applications, e.g.
   Email, Messaging.  This use case combines network stratum access and
   application stratum access, which is named as federated cross-layer
   access.  The detailed message flows for this use case are given.


2.  Related Work

   GSMA Association IDM project address operators' requirements for
   emerging mobile application (such as, Single Sign-on, mobile payments
   and other UICC enabled applications).  Several use cases are also
   identified[GSMA_IDM].  Liberty Alliance Telecommunications SIG
   investigates digital identity grown in both telecom and Internet,
   develops several use cases and proposes correspoding solutions for
   interworking these two different domains [TelecoSiG].

   GBA (Generic Bootsrapping Authentication) mechanism for boostrapping
   authentication and key agreement for application is denfined in
   [TS33.220].  The interworking between GBA and Identity Federation



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   Framework (ID-FE) is documented in [TR33.980].  Another interworking
   case between GBA and OpenID is specified in [TR33.924].

   Currently some use cases [I-D.ietf-abfab-usecases], architecture
   [I-D.ietf-abfab-arch] and mechanisms are developed in IETF abfab
   working group.


3.  Use Case

   Editor's Note: The section is for readable and completeness for this
   memo.  The formal use case is referred to [I-D.ietf-abfab-usecases].

   Telecom operators have a communication network infrastructures to
   provider users with a wealthy of access methods.  Telecom operators
   have a huge number of registered users, and they can provide trusted
   identity and higher security.  Therefore they have a natural
   advantage to act as an Identity Provider (IdP) to serve for service
   providers.  On the contrary most service providers on the Internet
   have limited amount of users and can not assure the security of user
   identity, but they can provide abundant kinds of service.
   Furthermore, user is reluctant to register too many accounts because
   it is inconvenient to remember dozens of passwords.

   Telecom network supports Web or non-Web application.  In some cases
   user prefers to choose non-Web application, e.g.  Messaging service,
   VoIP, EMail service, etc.  Based on the result of network stratum
   authentication and authorization, User equipment (UE) can access
   applications without doing another authentication and authorization
   procedure.  In this way, the system can implement federated cross-
   layer access.  Firstly mutual authentication is performed between UE
   and Network, secondly UE accesses Application based on the result of
   network stratum's authentication.  In this case, a federation is
   formed between Network and Application.

   For federated cross-layer access, Network can assure the Application
   of the authenticity of user's identity, share some of use profile
   with Application.  These can bring some benifits to stakeholders:

   o  For telecom operators, it becomes part of the business value chain
      as an Identity Provider.
   o  For service provider, it can focus on core competitive services
      without worrying about the number of registered users by reusing
      underlying security mechanisms during network stratum access.
   o  For end users, seamless sevice is provided, security and privacy
      are improved.





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4.  Message Flow

   Take mobile network for example, UE has pre-shared key (PSK) with
   HSS.  UE is mutully authenticated with network during attach
   procedure.  After authentication, a master session key (MSK) is
   created on both UE and AAA.  EAP [RFC3748] can enable the above
   procedure.


                                          +-------------+
                                          + Application |
                                        / +------+------+
                                      /          |
                                    /            |
                                  /              |
                                /                |
                              /            +-----+----+
                         +---+--+          |          |
                         |  UE  +----------+  Network |
                         +------+          |          |
                                           +----------+

                  Figure 1: Federated Cross-Layer Access

   Figure 1 shows the relation among UE, network and application.
   Firstly mutual authentication is performed between UE and Network,
   secondly UE accesses Application using Single Sign-ON (SSO) based on
   network stratum's authentication.  In this case, a federation is
   formed between Network and Application.  The brief steps are as
   follows:

   1.  When UE attach the Network, mutual authentication is performed
       master session key is created between them.
   2.  UE visits non-Web Application, e.g Messageing service, VoIP
       service, or Email service.
   3.  Application has no information about the UE.  The Application
       contacts Network to validate the authentication result in the
       network stratum.  Application can find Network according the
       configuration or dynamical discovery protocol.
   4.  Network responds to Application with authentication result.
   5.  UE is authorized to access the Application.

4.1.  Fast Re-authentication

   The message flows below make use of the security capabilities
   provided by network and some building blocks, such as GSS-EAP
   [I-D.ietf-abfab-gss-eap], AAA-SAML etc.




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   As descirbed in the specification of GSS-EAP[I-D.ietf-abfab-gss-eap],
   UE maps onto GSS-API initiator, RP acts as GSS-API acceptor or EAP
   path-through authenticator, IdP maps onto EAP server.  For the EAP is
   widely been used, this memo assumes the network access authentication
   is based on EAP.  When UE visits application, it will improve the
   efficiency of authentication if the previous authentication result is
   reused.  This procedure is called fast re-authentication, which is
   similar to the definition in EAP-AKA[RFC4187].

     +------+         +--------+        +------+         +------+
     |  UE  |         |   ASN  |        |  IdP |         |  RP  |
     +---+--+         +----+---+        +---+--+         +---+--+
       +-+-----------------+----------------+-+              |
       |   1. Network Access Authentication   |              |
       +-+-----------------+----------------+-+              |
         | 2. Access Application            |                |
         +-------------------------------------------------->|
         |                 |      3.GSS/EAP Req/Identity     |
         |<--------------------------------------------------+
         | 4.GSS/EAP Res/Fast Re-auth Identity               |
         +-------------------------------------------------->|
         |                 |                | 5. AAA/EAP Msg |
         |                 |                |<---------------+
         |                 |                | 6. AAA/EAP Msg |
         |                 |                +--------------->|
         |      7.GSS/EAP Req/Fast Re-auth  |                |
         |<--------------------------------------------------|
   +-----+--------+        |                |                |
   |8.Auth Msg &  |        |                |                |
   | Derive Key   |        |                |                |
   +-----+--------+        |                |                |
         |      9.GSS/EAP Res/Fast Re-auth  |                |
         +-------------------------------------------------->|
         |                 |                |10.AAA/SAML Req |
         |                 |                |<---------------|
         |                 |        +---------------+        |
         |                 |        |11.Auth & Deriv|        |
         |                 |        |Key & Con SAML |        |
         |                 |        +---------------+        |
         |                 |                |12.AAA/SAML Res |
         |                 |                +--------------->|
         |                 |                |        +-------+-------+
         |                 |                |        |13.Validate the|
         |                 |                |        |SAML Assertion |
         |      14.Establish Secure Channel |        +-------+-------+
         |<------------------------------------------------->|
         |                 |                |                |




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                     Figure 2: Fast Re-authentication

   1.   When UE access network, UE is performed mutual authentication
        with network.  EAP can be utilized to facilitate the
        authentication procedure.  EAP-Identity and EAP-Method will be
        exchanged between UE and network element.  After successful
        authentication, an shared MSK is generated and stored in UE and
        IdP respectively, which can be used to authenticate other
        applications and then establish secure channels.  The network
        access authentication and key agreement is used as underlying
        security mechanism for GSS-API.  The required credential for
        application is retrieved using gss_acquire_cred().
   2.   UE accesses Relying Party (RP).  UE is identified by NAI
        [RFC4282].  GSS-API [RFC4121] is acted as underlying transport
        mechanisms.
   3.   RP responds with EAP Request/Identity message, which is
        contained in GSS-API token as a subtoken.
   4.   UE sends EAP Response/Identity message in GSS-API token, which
        may include fast re-authentication identity.
   5.   When RP receieves the request from UE, RP transfers the EAP
        message to IdP in AAA message.  IdP checks the EAP message and
        agrees on fast re-authentication with UE.
   6.   IdP sends EAP-Request/Re-authentication to RP via AAA message.
   7.   RP strips off the AAA header and transfers the EAP message to UE
        via GSS-API token.
   8.   UE verifies the EAP message, thus authenticate the IdP using the
        credential retrieve from underlying security mechanisms.  UE
        derives session key from previous credential, which will provide
        per-message protection, e.g. integrity protection, encryption.
   9.   UE sends EAP-Response/Fast Re-authentication message to RP using
        GSS-API token.
   10.  RP transfers the EAP message to IdP using AAA message with a
        SAML Request (samlp:AuthenRequest) [I-D.ietf-abfab-aaa-saml]
        [I-D.jones-diameter-abfab].
   11.  When the fast re-authentication is successful, IdP derives the
        same session key and constructs a SAML respone (samlp:
        AuthenResponse).
   12.  IdP sends the SAML response message to RP via AAA message.
   13.  RP validates the assertion in the SAML message.  RP grants or
        denies access to the UE.
   14.  RP establishes secure channel with UE by means of GSS-EAP, thus
        the security services are also provided for message between UE
        and RP using gss_get_mic() and gss_get_warp().

4.2.  Secure Data Sharing

   After successful authentication, in order to provide effective
   services to customers, RP may need to retrieve some information from



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   operator's network, which stores some useful information (user
   profile, contact list, and other resources etc.).

   The following figure illustrate an arhchitecture of secure data
   sharingin for federated cross layer access.  Network layer includes
   ASN, IdP and RS, which provides RP in application layer with secure
   services such as authentication and data sharing.

                                  +---------+
                                 _+   RP    +
                              ,-` +----+----+\
                           ,-`         |      `.
                        ,-`            |        .
                     ,-`               |         \
                  .-`                  |          \
               .'`                     |           \
           _.'`                        |            `.
    +-----+--+                    +----+----+         .
    |        +--------------------+         |          \
    |   UE   |     +------+       |   IdP   |      +----+---+
    |        +-----+ ASN  +-------+         +------+  RS    |
    +--------+     +------+       +---------+      +--------+

               Figure 3: Architecture of Secure Data Sharing

   o  UE - User Equipment, it is identified by NAI and preconfigured
      with security credential.
   o  ASN - Access Serving Node, it is located at the border of network.
      It provides network access and authentication service to UE.
   o  IdP - Identity Provider, it is responsible for management of user
      identity.  It provides authentication service to UE or RP.  It is
      also to retrieve user information from RS and to provide them to
      RP in the condition of user's permission.
   o  RS - Resource Server, it stores user personal information, such as
      name, telephone, hobby, contact list, etc.
   o  RP - Relying Party, it provides user with such services as message
      service, VoIP, EMail service, etc.

   The following figure depicts the procedure for secure data sharing.
   UE and IdP are mutually authenticated.  RP reuses the authentication
   result in network access.  RP may securely acquire user shared data
   with the authorization of the user.









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       +----+       +-----+      +-----+      +------+      +----+
       | UE |       | ASN |      | IdP |      |  RS  |      | RP |
       +-+--+       +--+--+      +--+--+      +---+--+      +--+-+
         |             |            |             |            |
       +---------------------------------------------------------+
       |    1.Federated Cross Layer Access Authentication        |
       +---------------------------------------------------------+
         |             |            |             |            |
         |             |            |    2.User Info Req       |
         |             |            |<-------------------------+
         |             |            |             |            |
         |             |          3.|User Info Req|            |
         |             |            +------------>|            |
         |             |            |             |            |
         |             |          4.|User Info Res|            |
         |             |            |<------------+            |
         |   5.User Info Author Req |             |            |
         |<-------------------------+             |            |
         |             |            |             |            |
         |   6.User Info Author Res |             |            |
         +------------------------->|             |            |
         |             |            |             |            |
         |             |            |  7. User Info Res        |
         |             |            +------------------------->|
         |             |            |             |            |
         |             |            |  8. Notification         |
         |<----------------------------------------------------+
         |             |            |             |            |

                Figure 4: Procedure of Secure Data Sharing

   1.  UE performs federated cross layer access with IdP and RP, as
       shown in Figure 2.
   2.  When RP needs to acquire user's infomation for some services, RP
       sends user information request to IdP.
   3.  IdP verifies the request and sends user information request to
       RS.
   4.  RS validates the request and sends user information response to
       IdP according to the user's preferences.
   5.  IdP sends user information authorization request to UE.
   6.  UE chooses the prefered data to be shared and sends the user
       informaiton authorization response to IdP.
   7.  IdP send the authorized user information to SP.
   8.  After ueer data is sucessfully shared, RP sends a notification to
       UE.

   editor's note: The datailed security mechanisms and technical details
   will be considered in next time.



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5.  Acknowledgements

   The author would like to thank Klaas Wierenga, Hannes Tschofenig, Sam
   Hartman, Rhys Smith, Tao Fu, Zhengxue Xia for their valuable
   comments.


6.  IANA Considerations

   TODO


7.  Security Considerations

   TODO


8.  References

8.1.  Normative References

   [RFC3748]  Aboba, B., Blunk, L., Vollbrecht, J., Carlson, J., and H.
              Levkowetz, "Extensible Authentication Protocol (EAP)",
              RFC 3748, June 2004.

   [RFC4121]  Zhu, L., Jaganathan, K., and S. Hartman, "The Kerberos
              Version 5 Generic Security Service Application Program
              Interface (GSS-API) Mechanism: Version 2", RFC 4121,
              July 2005.

   [RFC4282]  Aboba, B., Beadles, M., Arkko, J., and P. Eronen, "The
              Network Access Identifier", RFC 4282, December 2005.

   [RFC4187]  Arkko, J. and H. Haverinen, "Extensible Authentication
              Protocol Method for 3rd Generation Authentication and Key
              Agreement (EAP-AKA)", RFC 4187, January 2006.

8.2.  Informative References

   [I-D.ietf-abfab-arch]
              Howlett, J., Hartman, S., Tschofenig, H., and E. Lear,
              "Application Bridging for Federated Access Beyond Web
              (ABFAB) Architecture", draft-ietf-abfab-arch-01 (work in
              progress), March 2012.

   [I-D.ietf-abfab-usecases]
              Smith, R., "Application Bridging for Federated Access
              Beyond web (ABFAB) Use Cases",



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              draft-ietf-abfab-usecases-02 (work in progress),
              February 2012.

   [I-D.ietf-abfab-aaa-saml]
              Howlett, J. and S. Hartman, "A RADIUS Attribute, Binding
              and Profiles for SAML", draft-ietf-abfab-aaa-saml-02 (work
              in progress), October 2011.

   [I-D.jones-diameter-abfab]
              Jones, M. and H. Tschofenig, "The Diameter 'Application
              Bridging for Federated Access Beyond Web (ABFAB)'
              Application", draft-jones-diameter-abfab-00 (work in
              progress), March 2011.

   [I-D.ietf-abfab-gss-eap]
              Hartman, S. and J. Howlett, "A GSS-API Mechanism for the
              Extensible Authentication Protocol",
              draft-ietf-abfab-gss-eap-05 (work in progress),
              March 2012.

   [GSMA_IDM]
              GSM Association, "White paper on Identity Management
              Requirements, Issues, and Directions for Mobile Industry",
              August 2007, <http://wiki.projectliberty.org/images/d/d8/
              GSMA_IDM_WP-SE47.pdf>.

   [TelecoSiG]
              Liberty Alliance Project, "Bridging IMS and Internet
              Identity", December 2009, <http://www.projectliberty.org/
              liberty/content/download/4315/28869/file/
              WP-BridgingIMS_AndInternetIdentity_V1.0.pdf>.

   [TS33.220]
              3GPP, "Generic Authentication Architecture (GAA); Generic
              Bootstrapping Architecture (GBA)", 3GPP TS 33.220 10.0.0,
              October 2010.

   [TR33.980]
              3GPP, "Liberty Alliance and 3GPP security interworking;
              Interworking of Liberty Alliance Identity Federation
              Framework (ID-FF), Identity Web Services Framework (ID-
              WSF) and Generic Authentication Architecture (GAA)", 3GPP
              TR 33.980 10.0.0, April 2011.

   [TR33.924]
              3GPP, "Identity management and 3GPP security interworking;
              Identity management and Generic Authentication
              Architecture (GAA) interworking", 3GPP TR 33.924 10.1.0,



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              June 2011.


Author's Address

   Yinxing Wei (editor)
   ZTE Corporation
   No 68, Zijinghua Road
   Nanjing, Jiangsu  210012
   China

   Phone: +86 25 52872328
   Email: wei.yinxing@zte.com.cn






































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