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RFC 7832 - Application Bridging for Federated Access Beyond Web

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Internet Engineering Task Force (IETF)                     R. Smith, Ed.
Request for Comments: 7832                                          Jisc
Category: Informational                                         May 2016
ISSN: 2070-1721

 Application Bridging for Federated Access Beyond Web (ABFAB) Use Cases


   Federated identity is typically associated with web-based services at
   present, but there is growing interest in its application in non-web-
   based contexts.  The goal of this memo is to document a selection of
   the wide variety of these contexts whose user experience could be
   improved through the use of technologies based on the Application
   Bridging for Federated Access Beyond web (ABFAB) architecture and

Status of This Memo

   This document is not an Internet Standards Track specification; it is
   published for informational purposes.

   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).  Not all documents
   approved by the IESG are a candidate for any level of Internet
   Standard; see Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at

Copyright Notice

   Copyright (c) 2016 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
   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.

Table of Contents

   1. Introduction ....................................................2
   2. Context of Use Cases ............................................3
   3. Use Cases .......................................................3
      3.1. Cloud Services .............................................3
           3.1.1. Cloud-Based Application Services ....................4
           3.1.2. Cloud-Based Infrastructure Services .................5
      3.2. High-Performance Computing .................................6
      3.3. Grid Infrastructure ........................................6
      3.4. Databases and Directories ..................................7
      3.5. Media Streaming ............................................8
      3.6. Printing ...................................................9
      3.7. Accessing Applications from Devices on a Telecoms
           Infrastructure .............................................9
      3.8. Enhanced Security Services for S/MIME .....................10
      3.9. Smart Objects .............................................11
   4. Security Considerations ........................................11
   5. References .....................................................12
      5.1. Normative References ......................................12
      5.2. Informative References ....................................12
   Acknowledgments ...................................................13
   Contributors ......................................................13
   Author's Address ..................................................13

1.  Introduction

   Federated identity facilitates the controlled sharing of information
   about people (a.k.a. "principals"), commonly across organizational
   boundaries.  This avoids redundant registration of principals who
   operate in and across multiple domains, both reducing the
   administrative overhead for the organizations involved and improving
   the usability of systems for the principal.  Simultaneously, it can
   also help address privacy-related concerns, along with the regulatory
   and statutory requirements of some jurisdictions.

   The information that is passed between organizations may include
   authentication state and identity information that can be used for
   many purposes, including making access management decisions.  A
   number of mechanisms support the transmission of this information for
   web-based scenarios in particular (e.g., the Security Assertion
   Markup Language (SAML) [OASIS.saml-profiles-2.0-os]), but there is
   significant interest in the more general application of federated
   identity to include non-web use cases.  This document enumerates some
   of these use cases, describing how technologies based on the ABFAB
   architecture [RFC7831] and specifications could be used.

2.  Context of Use Cases

   The use cases described in this document are a result of work led by
   Jisc, the operator of the United Kingdom's education and research
   network, responding to requirements from its community.  These use
   cases have also been augmented by various inputs from the IETF

   The ABFAB architecture and specifications enables authentication and
   authorization to occur across organizational boundaries.  For many
   applications, principals need not have pre-instantiated accounts that
   their federated identity maps to before their first visit to that
   application; the application can perform this process on the fly.  In
   cases where such accounts are required for particular applications,
   the pre-provisioning process is out of scope; the ABFAB technology
   assumes that any such requirements have already been fulfilled.
   Standards-based work of note that would assist with this
   pre-provisioning of accounts includes the standards and
   specifications produced by the IETF SCIM working group.

3.  Use Cases

   This section describes some of the various potential use cases where
   technologies based on the ABFAB architecture and specifications could
   help improve the user experience; each includes a brief description
   of how current technologies attempt to solve the use cases and how
   this could be improved upon by ABFAB implementations.

3.1.  Cloud Services

   Cloud computing is emerging as a common way of provisioning
   infrastructure services in an on-demand manner.  These services are
   typically offered as one of three models:

   o  General infrastructure services such as computing power, networks,
      storage, and utilities ("Infrastructure as a Service", or IaaS);

   o  Software stacks or platforms such as database servers, web
      servers, and application runtime environments ("Platform as a
      Service", or PaaS);

   o  Common application software such as email, shared storage,
      business applications such as Customer Relationship Management
      (CRM), or scientific applications ("Software as a Service",
      or SaaS).

   In many cases, the provisioned cloud infrastructures and applications
   need to be integrated with existing infrastructure of the
   organization, and it is of course desirable if this could be achieved
   in a way that allows business or scientific workflows to act across
   infrastructure -- both across the cloud and in the local
   infrastructure -- in as seamless a manner as possible.

   There are two main areas where federated access fits in cloud

   o  Using federation to help mediate access to cloud-based application
      services (e.g., cloud-provided email or CRM systems);

   o  Using federation to help mediate access to the management of
      cloud-based infrastructure services.

3.1.1.  Cloud-Based Application Services

   Many organizations are seeking to deliver services to their users
   through the use of providers based in the "cloud".  This is typically
   motivated by a desire to avoid management and operation of commodity
   services that, through economies of scale and so forth, can often be
   delivered more efficiently by such providers.

   Many providers already provide web-based access using conventional
   federated authentication mechanisms -- for example, outsourced email
   provision where federated access is enabled using "webmail"
   applications where access is mediated through the use of SAML
   [OASIS.saml-profiles-2.0-os].  This use of federated authentication
   enables organizations that consume cloud services to more efficiently
   orchestrate the delivery of these services to their users and also
   enables single sign-on to the services for these users.

   Frequently, however, users will prefer to use desktop applications
   that do not use web (i.e., based on HTTP) protocols.  For example, a
   desktop email client may use a variety of non-web protocols,
   including SMTP [RFC5321], IMAP [RFC3501], and the Post Office
   Protocol (POP) [RFC1939].  Some cloud providers support access to
   their services using non-web protocols; however, the authentication
   mechanisms used by these protocols will typically require that the
   provider has access to the user's credentials -- i.e., non-federated.
   Consequently, the provider will require that users' credentials are
   regularly synchronized from the user organization to the provider,
   with the obvious overhead this imparts on the organization along with
   the obvious implications for security and privacy, or else be
   provisioned directly by the provider to the user.

   The latter approach of directly provisioning accounts may be
   acceptable in the case where an organization has relationships with
   only a small number of providers, but this approach may become
   untenable if an organization obtains services from many providers.
   Consequently, any organization with a requirement to use non-web
   protocols would prefer to make use of the credentials that they have
   already provisioned their users with, and to utilize federated
   authentication with non-web protocols to obtain access to cloud-based

   ABFAB could help in this context, as its specifications would enable
   federated authentication for a variety of non-web protocols, thus
   gaining the benefits of federated authentication without any of the
   drawbacks that are currently experienced.

3.1.2.  Cloud-Based Infrastructure Services

   Typical IaaS or PaaS cloud use cases deal with provisioning on-demand
   cloud-based infrastructure services that may include infrastructure
   components such as computing and storage resources, network
   infrastructure, and other utilities.  Cloud-based virtualized
   applications should ideally operate in the same way as regular
   non-virtualized applications whilst allowing management of the
   virtual computing resources (scaling, migration, reconfiguration)
   without changing the management applications.

   In many cases, moving applications or platforms to the cloud may
   require their redesigning/refactoring to support dynamic deployment
   and configuration, including their security services, and
   authentication and authorization services.  These will typically
   today be extensively based on manual setup and configuration of such
   components and features as trusted certificates and trust anchors,
   authorities and trusted services (both their location and
   certificates), attribute namespaces, and policies.

   ABFAB could help in this context as a way of moving from the model of
   manually configured authentication and authorization towards a more
   easily managed system involving federated trust and identity, and
   ABFAB will be applicable for a wide range of existing features (e.g.,
   connecting to a newly provisioned Virtual Machine through
   ABFAB-enabled Secure Shell (SSH) [RFC4251] instead of having to
   manually manage an administrative login to that machine).

3.2.  High-Performance Computing

   High-Performance Computing (HPC) is a discipline that uses
   supercomputers and computer clusters to solve complex computation
   problems; it is most commonly associated with scientific research or
   computational science.

   Access to HPC resources, often mediated through technologies such as
   SSH, is typically managed through the use of user digital
   certificates [RFC5280] or through manually provisioned credentials
   and accounts.  This requires HPC operators to issue certificates or
   accounts to users using a registration process that often duplicates
   identity management processes that already exist within most user
   organizations.  The HPC community would like to utilize federated
   identity to perform both the user registration and authentication
   functions required to use HPC resources, and so reduce costs by
   avoiding this duplication of effort.

   The HPC community also have the following additional requirements:

   o  Improve business continuity: In the event of operational issues at
      an HPC system at one organization (for example, a power failure),
      users and jobs could be transparently moved to other HPC systems
      without the overhead of having to manage user credentials for
      multiple organizations;

   o  Establish "HPC as a service": Many organizations who have invested
      in HPC systems want to make their systems easily available to
      external customers.  Federated authentication facilitates this by
      enabling these customers to use their existing identity
      management, user credentialing, and support processes;

   o  Improve the user experience: Authentication to HPC systems is
      normally performed using user digital certificates, which some
      users find difficult to use.  Federated authentication can provide
      a better user experience by allowing the use of other types of
      credentials, without requiring technical modifications to the HPC
      system to support these.

   ABFAB could help in this context, as it could enable federated
   authentication for many of the protocols and technologies currently
   in use by HPC providers, such as SSH.

3.3.  Grid Infrastructure

   Grids are large-scale distributed infrastructures, consisting of many
   loosely coupled, independently managed, and geographically
   distributed resources managed by organizationally independent

   providers.  Users of grids utilize these resources using grid
   middleware that allows them to submit and control computing jobs,
   manipulate datasets, communicate with other users, etc.  These users
   are organized into Virtual Organizations (VOs); each VO represents a
   group of people working collaboratively on a common project.  VOs
   facilitate both the management of their users and the meditation of
   agreements between their users and resource providers.

   Authentication and authorization within most grids are performed
   using a Public Key Infrastructure, requiring each user to have an
   X.509 public-key certificate [RFC5280].  Authentication is performed
   through ownership of a particular certificate, while authorization
   decisions are made based on the user's identity (derived from their
   X.509 certificate), membership of a particular VO, or additional
   information assigned to a user by a VO.  While efficient and
   scalable, this approach has been found wanting in terms of usability
   -- many users find certificates difficult to manage, for various

   One approach to ameliorating this issue, adopted to some extent by
   some grid communities already, is to abstract away direct access to
   certificates from users, instead using alternative authentication
   mechanisms and then converting the credential provided by these into
   standard grid certificates.  Some implementations of this idea use
   existing federated authentication techniques.  However, current
   implementations of this approach suffer from a number of problems,
   not the least of which is the inability to use the federated
   credentials used to authenticate to a credential-conversion portal to
   also directly authenticate to non-web resources such as SSH daemons.

   The ability to use federated authentication directly through ABFAB,
   without the use of a credential-conversion service, would allow users
   to authenticate to a grid and its associated services, allowing them
   to directly launch and control computing jobs, all without having to
   manage, or even see, an X.509 public-key certificate at any point in
   the process.  Authorization within the grid would still be performed
   using VO membership as asserted by the user's Identity Provider (IdP)
   through the federated transport.

3.4.  Databases and Directories

   Databases (e.g., MySQL, PostgreSQL, Oracle) and directory
   technologies (e.g., OpenLDAP (http://www.openldap.org/), Microsoft
   Active Directory, Novell eDirectory) are very commonly used within
   many organizations for a variety of purposes.  Such purposes can
   include core administrative functions, such as hosting identity
   information for its users, as well as business functions (e.g.,
   student records systems at educational organizations).

   Access to such database and directory systems is usually provided for
   internal users only; however, users external to the organizations
   sometimes require access to these systems directly -- for example,
   external examiners in educational organizations requiring access to
   student records systems, members of cross-organizational project
   teams who store information in a particular organization's systems,
   and external auditors.

   Credentials for users either internal or external to the organization
   that allow access to these databases and directories are usually
   provisioned manually within an organization, either using identity
   management technologies or through more manual processes.  For the
   internal users, this situation is fine -- this is one of the
   mainstays of identity management.  However, for external users who
   require access, this represents more of a problem for organizational
   processes.  The organization has to either (1) add these external
   users to its internal identity management systems or (2) provision
   these credentials directly within the database/directory systems and
   continue to manage them, including appropriate access controls
   associated with each credential, for the lifetime of that credential.

   Federated authentication to databases or directories, via ABFAB
   technologies, would improve upon this situation, as it would remove
   the need to provision and de-provision credentials to access these
   systems.  Organizations may still wish to manually manage access
   control of federated identities; however, even this could be provided
   through federated means, if the trust relationship between
   organizations was strong enough for the organization providing the
   service to rely upon it for this purpose.

3.5.  Media Streaming

   Media streaming services (audio or audio/video) are often provided
   publicly to anonymous users, but authentication is important for a
   protected subset of streams where rights management and access
   control must be applied.

   Streams can be delivered via protocols that already include
   authentication, such as the Real Time Streaming Protocol (RTSP)
   [RFC2326] or RTP [RFC3550], or can be published in an encrypted form
   with keys only being distributed to trusted users.  Federated
   authentication is applicable to both of these cases.

   Alternative mechanisms to managing access exist -- for example, an
   approach where a unique stream URI is minted for each user.  However,
   this relies on preserving the secrecy of the stream URI and also
   requires a communication channel between the web page used for
   authentication and the streaming service itself.  Federated

   authentication would be a better fit for this kind of access control.
   Thus, ABFAB technologies that allow federated authentication directly
   within (inherently non-web) media streaming protocols would represent
   an enhancement to this area.

3.6.  Printing

   A visitor from one organization to the premises of another often
   requires the use of print services.  Their home organization may of
   course offer printing, but the output could be a long way away, so
   the home service is not useful.  The user will typically want to
   print from within a desktop or mobile application.

   Where this service is currently offered, it would usually be achieved
   through the use of "open" printers (i.e., printers that allow
   anonymous print requests), where printer availability is advertised
   through the use of Bonjour or other similar protocols.  If the
   organization requires authenticated print requests (usually for
   accounting purposes), the visitor would usually have to be given
   credentials that allow this, often supplemented with pay-as-you-go
   style payment systems.

   Adding federated authentication to the Internet Printing Protocol
   (IPP) [RFC2911] (and other relevant protocols) would enable this kind
   of remote printing service without the administrative overhead of
   credentialing these visitors (who, of course, may well be one-time
   visitors to the organization).  This would be immediately applicable
   to higher education, where this use case is increasingly important
   thanks to the success of federated network authentication systems
   such as eduroam (https://www.eduroam.org), but could also be used in
   other contexts such as commercial print kiosks, or in large
   heterogeneous organizations.

3.7.  Accessing Applications from Devices on a Telecoms Infrastructure

   Telecom operators typically have the following properties:

   o  A large collection of registered users, many of whom may have
      identities registered to a fairly high level of assurance (often
      for payment purposes).  However, not all users will have this
      property -- for example, non-contract customers on mobile telecoms
      infrastructures in countries with low levels of identity
      registration requirements.

   o  An existing network infrastructure capable of authenticating a
      device (e.g., a cellphone or an Asymmetric Digital Subscriber Line
      (ADSL) router) and, by inference, its owner.

   o  A large collection of applications (both web-based and
      non-web-based) that its users wish to access using their devices.
      These applications could be hosted by the telecom operator
      directly, or they could be any application or system on the
      internet -- for example, network messaging services, VoIP,
      or email.

   At present, authentication to these applications will be typically
   configured manually by the user on the device (or on a different
   device connected to that device) by inputting their (usually
   pre-provisioned out of band) credentials for that application -- one
   per application.

   The use of ABFAB technologies in this case, via a mechanism dubbed
   "federated cross-layer access" (see [FCLA]) would greatly enhance the
   user experience of using these applications through devices.
   Federated cross-layer access would make use of the initial mutual
   authentication between device and network, to allow subsequent
   authentication and authorization to happen in a seamless manner for
   the user of that device authenticating to applications.

3.8.  Enhanced Security Services for S/MIME

   There are many situations where organizations want to protect
   information with robust access control, either for implementation of
   intellectual property right protections, for enforcement of
   contractual confidentiality agreements, or because of legal
   regulations.  The Enhanced Security Services (ESS) for S/MIME defines
   an access control mechanism that is enforced by the recipient's
   client after decryption of the message (see [MSG-AC-REQ]).  The data
   model used makes use of Policy Decision Points (PDPs), which make the
   policy decisions; Policy Enforcement Points (PEPs), which make
   decision requests to the PDP; and Policy Information Points (PIPs),
   which issue attributes about subjects.  The decisions themselves are
   based on the policies and on the subject attributes.

   The use of ABFAB technologies in this case would enable both the
   front-end and back-end attribute exchange required to provide subject
   attributes.  When the PEP contacts the PDP, it would initiate an
   ABFAB authentication in order to authenticate to the PDP and allow it
   to obtain these required subject attributes.  Once authenticated, the
   PDP would return a token to the subject PEP that could then be used
   for subsequent authentications to the PDP.

3.9.  Smart Objects

   Many smart device deployments involve multiple organizations that do
   not directly share security infrastructure.  For example, in smart
   power deployments, devices (e.g., appliances) and infrastructure
   (e.g., electric car chargers) will wish to connect to an energy
   management system.  The energy management system is provided by a
   utility company in some deployments.  The utility company may wish to
   grant access only to authorized devices; for example, a consortium of
   utility companies and device manufacturers may certify devices to
   connect to power networks.

   In another example, consumer devices may be used to access cloud
   services.  For example, a camera could be bound to a photo processing
   site.  Authentication and authorization for uploading pictures or
   ordering prints are required.  Sensors could be used to provide data
   to services run by organizations other than the sensor manufacturer.
   Authorization and authentication can become very tricky when sensors
   have no user interface.  Cellular devices may want to access services
   provided by a third party, regardless of whether the cellular network
   or Wi-Fi is used.  This becomes difficult when authorization and
   billing are coordinated by the cellular provider.

   The use of ABFAB technologies in this case would provide
   authentication between one entity, such as a smart device, and its
   IdP.  Only two parties are involved in this exchange; this means that
   the smart device need not participate in any complicated public-key
   infrastructure even if it is authenticating against many cloud
   services.  Instead, the device can delegate the process of
   authenticating the service, and even deciding whether the device
   should be permitted to access the service, to the IdP.  This has
   several advantages.  A wide variety of revenue-sharing models are
   enabled.  Because device authentication is only with a single IdP,
   phishing of device credentials can be avoided.  Authorization and
   decisions about what personal information to release are made by the
   IdP.  The device owner can use a rich interface such as a website to
   configure authorization and privacy policy even if the device has no
   user interface.  This model works well with pre-provisioning of
   device credentials.

4.  Security Considerations

   This document contains only use cases and defines no protocol
   operations for ABFAB.  Security considerations for the ABFAB
   architecture are documented in [RFC7831], and security considerations
   for ABFAB technologies and protocols that are discussed in these use
   cases are documented in the corresponding protocol specifications.

5.  References

5.1.  Normative References

   [RFC7831]  Howlett, J., Hartman, S., Tschofenig, H., and J. Schaad,
              "Application Bridging for Federated Access Beyond Web
              (ABFAB) Architecture", RFC 7831, DOI 10.17487/RFC7831,
              May 2016, <http://www.rfc-editor.org/info/rfc7831>.

5.2.  Informative References

   [FCLA]     Wei, Y., Ed., "Federated Cross-Layer Access", Work in
              Progress, draft-wei-abfab-fcla-02, March 2012.

              Freeman, T., Schaad, J., and P. Patterson, "Requirements
              for Message Access Control", Work in Progress,
              draft-freeman-plasma-requirements-11, March 2015.

              Hughes, J., Cantor, S., Hodges, J., Hirsch, F., Mishra,
              P., Philpott, R., and E. Maler, "Profiles for the OASIS
              Security Assertion Markup Language (SAML) V2.0", OASIS
              Standard OASIS.saml-profiles-2.0-os, March 2005,

   [RFC1939]  Myers, J. and M. Rose, "Post Office Protocol - Version 3",
              STD 53, RFC 1939, DOI 10.17487/RFC1939, May 1996,

   [RFC2326]  Schulzrinne, H., Rao, A., and R. Lanphier, "Real Time
              Streaming Protocol (RTSP)", RFC 2326,
              DOI 10.17487/RFC2326, April 1998,

   [RFC2911]  Hastings, T., Ed., Herriot, R., deBry, R., Isaacson, S.,
              and P. Powell, "Internet Printing Protocol/1.1: Model and
              Semantics", RFC 2911, DOI 10.17487/RFC2911,
              September 2000, <http://www.rfc-editor.org/info/rfc2911>.

              VERSION 4rev1", RFC 3501, DOI 10.17487/RFC3501,
              March 2003, <http://www.rfc-editor.org/info/rfc3501>.

   [RFC3550]  Schulzrinne, H., Casner, S., Frederick, R., and V.
              Jacobson, "RTP: A Transport Protocol for Real-Time
              Applications", STD 64, RFC 3550, DOI 10.17487/RFC3550,
              July 2003, <http://www.rfc-editor.org/info/rfc3550>.

   [RFC4251]  Ylonen, T. and C. Lonvick, Ed., "The Secure Shell (SSH)
              Protocol Architecture", RFC 4251, DOI 10.17487/RFC4251,
              January 2006, <http://www.rfc-editor.org/info/rfc4251>.

   [RFC5280]  Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
              Housley, R., and W. Polk, "Internet X.509 Public Key
              Infrastructure Certificate and Certificate Revocation List
              (CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008,

   [RFC5321]  Klensin, J., "Simple Mail Transfer Protocol", RFC 5321,
              DOI 10.17487/RFC5321, October 2008,


   These use cases have been developed and documented using significant
   input from Jens Jensen (STFC Rutherford Appleton Laboratory), Daniel
   Kouril (CESNET), Michal Prochazka (CESNET), Ian Stewart (University
   of Edinburgh), Stephen Booth (Edinburgh Parallel Computing Centre),
   Eefje van der Harst (SURFnet), Joost van Dijk (SURFnet), Robin
   Breathe (Oxford Brookes University), Yinxing Wei (ZTE Corporation),
   Trevor Freeman (Microsoft Corporation), Sam Hartman (Painless
   Security, LLC), and Yuri Demchenko (University of Amsterdam).


   The following individuals made important contributions to the text of
   this document: Tim Bannister (Manchester University), Simon Cooper
   (Jisc), Josh Howlett (Jisc), and Mark Tysom (Jisc).

Author's Address

   Dr. Rhys Smith (editor)
   Lumen House, Library Avenue, Harwell
   Oxford  OX11 0SG
   United Kingdom

   Phone: +44 1235 822145
   Email: rhys.smith@jisc.ac.uk


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