ABFAB                                                           R. Smith
Internet-Draft                                        Cardiff University
Intended status: Informational                              July 4, 2014 6, 2015
Expires: January 5, 2015 7, 2016

 Application Bridging for Federated Access Beyond web (ABFAB) Usability
                   and User Interface Considerations


   The real world use of ABFAB-based technologies requires that any
   identity that is to be used for authentication has to authenticate be configured
   on the ABFAB-
   enabled ABFAB-enabled client device.  Achieving this requires software
   on that device (either built into the operating system or a
   standalone utility) that will interact with the user, managing their
   identity information and identity-to-service mappings.  All designers
   of software to fulfil this role will face the same set of challenges.
   This document aims to document these challenges with the aim of
   producing well-thought out UIs with some degree of consistency
   between implementations.

Status of This Memo

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   This Internet-Draft will expire on January 5, 2015. 7, 2016.

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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . .   3 .  4
   2.  Conventions  . . . . . . . . . . . . . . . . . . . . . . . . .   3  4
   3.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .   3  4
   4.  Context  . . . . . . . . . . . . . . . . . . . . . . . . . . .   4  5
   5.  Considerations around Terminology  . . . . . . . . . . . . . .   5  6
     5.1.  Identity . . . . . . . . . . . . . . . . . . . . . . . .   5 .  6
     5.2.  Services . . . . . . . . . . . . . . . . . . . . . . . . .  6
     5.3.  Identity to Service Mapping  . . . . . . . . . . . . . . .   6  7
   6.  Considerations around Management of Identities . . . . . . .   6 .  7
     6.1.  Information associated with each Identity  . . . . . . . .   6  7
     6.2.  Storage of Identity Information  . . . . . . . . . . . . .  8
     6.3.  Adding/Association of an Identity  . . . . . . . . . . . .  8
       6.3.1.  Manual Addition  . . . . . . . . . . . . . . . . . . .   8  9
       6.3.2.  Manually Triggered Automated Addition  . . . . . . . .   9 10
       6.3.3.  Fully Automated Addition . . . . . . . . . . . . . .  10 . 11
     6.4.  Modifying Identity Information . . . . . . . . . . . . .  10 . 11
       6.4.1.  Manual Modification  . . . . . . . . . . . . . . . . . 11
       6.4.2.  Automated Modification . . . . . . . . . . . . . . . . 11
     6.5.  Verifying an identity  . . . . . . . . . . . . . . . . . .  11 12
     6.6.  Removing an Identity . . . . . . . . . . . . . . . . . .  11 . 12
       6.6.1.  Manual Removal . . . . . . . . . . . . . . . . . . . . 12
       6.6.2.  Automated Removal  . . . . . . . . . . . . . . . . . . 12
     6.7.  Storing an Identity with or without credentials  . . . . . 12
   7.  Considerations around Management of Service to Identity
       Mappings . . . . . . . . . . . . . . . . . . . . . . . . . .  12 . 13
     7.1.  Associating a Service with an Identity . . . . . . . . . . 13
       7.1.1.  User-driven Manual Association . . . . . . . . . . . . 13
       7.1.2.  Automated Rules-based Association  . . . . . . . . . .  13 14
     7.2.  Disassociating a Service with an Identity  . . . . . . . .  13 14
     7.3.  Listing Services and Identities  . . . . . . . . . . . . . 14
     7.4.  Showing the Service that is requesting Authentication  . . 14
     7.5.  Showing the Identity currently in use  . . . . . . . . . .  14 15
     7.6.  Multiple Identities for a Particular Service . . . . . .  14 . 15
     7.7.  Not using ABFAB for a Particular Service . . . . . . . . . 15
   8.  Handling of Errors . . . . . . . . . . . . . . . . . . . . .  15
     8.1.  Identity Association/Verification Errors  . . . . . . . . 15
     8.2.  Service Errors  . . . . . . . . . . . . . . . . . .
   9.  Handling of Successes  . . .  15
     8.3.  Other Errors. . . . . . . . . . . . . . . . . . 16
     9.1.  Reporting Authentication Success on First Use of
           Identity . . . . .  15
   9.  Handling of Successes . . . . . . . . . . . . . . . . . . . .  15
     9.1.  Reporting Authentication Success on First Use of Identity  15 16
     9.2.  Reporting Authentication Success . . . . . . . . . . . .  16 . 17

   10. Other Considerations . . . . . . . . . . . . . . . . . . . .  16 . 17
     10.1. Identity Selector Taking Focus . . . . . . . . . . . . .  16 . 17
     10.2. Import/Export of Credentials . . . . . . . . . . . . . .  16 . 17
   11. Contributors . . . . . . . . . . . . . . . . . . . . . . . .  16 . 17
   12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . .  16 . 17
   13. Security Considerations  . . . . . . . . . . . . . . . . . . . 17
   14. Privacy Considerations  . . . . . . . . . . . . . . . . . . .  17
   15. IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  17
   16. 18
   15. Normative References . . . . . . . . . . . . . . . . . . . .  17 . 18
   Appendix A.  Change Log  . . . . . . . . . . . . . . . . . . . . .  18 19
   Appendix B.  Open Issues . . . . . . . . . . . . . . . . . . . .  19 . 20

1.  Introduction

   The use of ABFAB-based technologies requires that any identity that
   is to be used for authentication has to authenticate be configured on the client
   device.  Achieving this requires software on that device (either
   built into the operating system or a standalone utility) that will
   interact with the user, and manage the user's identities and
   credential-to-service mappings.  Anyone designing that software will
   face the same set of challenges.

   This document does not intend to supplant evidence-based UI design
   guidelines; implementers of identity selectors are strongly
   encouraged to understand the latest in HCI and UX thought and
   practice.  Instead, it aims to document the common challenges faced
   by implementers with the aim of providing a common starting point for
   implementers in the hope that this aids in producing well-thought out
   UIs with some degree of consistency.

2.  Conventions

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in [RFC2119].

3.  Terminology

   Various items of terminology used in the document are heavily
   overloaded and could thus in that they mean a variety of different things to
   different people.  In an attempt to minimise this problem, this
   section gives a brief description of the main items of terminology
   used in order to aid a consistent understanding of this document.

   o  NAI: Network Access Identifier - a standard way of identifying a
      user and assisting in the routing of an authentication request
      (see [RFC4282]).

   o  Identity: In this context, an identity is a credential given to a
      user by a particular organisation with which they have an
      association.  A user may have multiple identities - potentially
      multiple identities per organisation, and also across multiple
      organisations.  Each identity will consist of an NAI, alongside
      other information that supports authentication.  Note that in
      other contexts the usual use of "identity" would match our use of
      "user", whereas the usual use of "identifier" matches our use of

   o  Service: The thing that the user is attempting to authenticate to
      via ABFAB technology.  See [I-D.ietf-abfab-usecases] for some
      example ABFAB use cases.  Also known as the Relying Party.

   o  Identity Selector: A piece of software that enables the process by
      which the GSS-API acquires the identity to use with a particular
      service.  An Identity Selector typically would allow the user to
      configure a set of identities along with service to identity

   o  Trust anchor: An authoritative source of verification of a
      particular ABFAB service or Identity Provider, used to allow
      authentication of a server using X.509 [RFC5280].  Typically a
      commercial CA to allow authentication via chain of trust, or a
      preconfigured non-commercial certificate (e.g. self-signed).

4.  Context

   When using the ABFAB architecture (see [I-D.ietf-abfab-arch]) to
   perform federated authentication to some service, a user will need to
   provide identity information that they wish to use to authenticate to
   that particular service.  This will happen through a process of the
   application calling the GSS-API, which will in turn gather the user's
   credentials through some process.  We will call this process the
   "identity selector" in this document (though note that this is not a
   recommendation on terminology for the process).

   The simplest way to achieve the desired effect would be a process
   that simply takes the credentials from the currently logged in user
   (e.g. the Windows Domain Credentials) and uses those for all services
   that request authenticate through ABFAB.  This approach gives
   ultimate simplicity in terms of UI (it wouldn't have one) but the
   least flexibility (the user has to use a single identity for
   everything).  If there is ever to be a requirement for a user to use
   a different set of credentials for a service, then something more
   complex will be needed.

   Where there is a requirement for multiple credentials to be
   supported, there are at least two methods that could be employed to
   configure identities and associated information:

   o  They could be configured manually by the user in a configuration
      file that could be edited by hand or some such simple process, and
      read by the GSS-API mechanism.  While this could work very well
      functionally, in practice only a small subset of users would be
      happy with - and able to - configure their identities in such a

   o  They could be configured through some interactive process.  For
      ease of use this should have a simple UI, although to support some
      use cases a headless mode (i.e. a way of interacting with the
      identity selector when there is no GUI present) may need to be

   When designing an identity selector with a UI (or indeed, with a
   headless mode), any implementer will share a common set of usability
   considerations inherent to the context.  This document aims to
   explore these considerations, and provide advice and guidance on
   addressing them where possible.

5.  Considerations around Terminology

   Anyone designing an identity selector will have to grapple with
   choosing terminology that the average user has some chance of
   understanding.  This terminology can split into a few main functional
   areas, as discussed next.

5.1.  Identity

   The first area where terminology is needed is around the identity/
   identities of the user.  Users are typically used to seeing a variety
   of terms for aspects of their identity in the federated sense, and an
   even larger variety in the wider internet sense.  For example, in the
   federated sense some of these terms include "username", "login",
   "network account", "institutional account", "home organisation
   account", "credentials", and a myriad of other such terms.  However,
   NAI - the technically correct name for their identity in an ABFAB
   sense - is highly unlikely to be one of these terms that users are
   used to seeing.  Further, given that the NAI superficially looks like
   an email address, there is a definite potential for confusion.

   Implementers of an identity selector will need to carefully consider
   their intended audience for both their level of technical capability
   and the existing terminology that they may have been exposed to.

   Beyond terminology, careful thought needs to be given to the paradigm
   to use when presenting identity to users, as identities and services
   are abstract concepts that some users may not find is easily
   understandable.  Implementers may wish to keep such abstract
   concepts, or may wish to examine attempts to map to real world
   paradigms, e.g. the idea of using "Identity Cards" that are held in
   the user's "Wallet", as used by Microsoft Cardspace.

5.2.  Services

   Terminology around services is likely to be less of a problem than
   identity, but it will actually depend on what the service is.  For
   example, each service could be simply described as "server",
   "system", etc.  But for simplicity just the word "service" will
   probably usually suffice.

5.3.  Identity to Service Mapping

   Depending on your perspective either each identity may be mapped to
   multiple services, or each service has multiple identities mapped to
   it.  Thus any UI could present either perspective, or both.

6.  Considerations around Management of Identities

   One of the core features of an identity selector is the management of
   a user's identities.  This section first looks at what information
   associated with an identity will need to managed, and then looks in
   detail at various usability considerations of this area.

6.1.  Information associated with each Identity

   The bare minimum set of information that MUST be stored about each
   identity to allow ABFAB authentication to take place is a single

   o  NAI: The user's Network Access Identifier (see [RFC4282]) for this
      particular credential.  For example, "joe@example.com".  Note that
      the identity selector MUST NOT store different identities that use
      the same NAI.  This is required as the NAI is the unique key that
      is used by the identity selector when interacting with the GSS-API
      mechanism for various reasons, for example, to allow the GSS-API
      mechanism to report back error or success statuses.

   Next up is a small set of information that SHOULD be stored about
   each identity to allow the user to effectively select a particular

   o  Trust anchor: For the identity selector to be able to verify that
      the server it is going to talk to and attempt to authenticate
      against is the server that it is expecting, and that it is not
      being spoofed in some way.  This is likely to be an X.509
      certificate [RFC5280], or a tuple of (trusted root certificate,
      servername in Subject or subjectAltName).  Storing a credential
      without a relevant trust anchor allows for the possibility of a
      malicious attacker intercepting traffic and masquerading as the
      server in question.

   o  Credential: Whatever is used by the user to authenticate
      themselves with a particular NAI.  What exactly this will be will
      be dependent on the EAP method being used, but is likely to be
      something like a password or a certificate.  Note that this is a
      SHOULD, rather than a MUST, because there are use cases where a
      user may specifically opt for this not to be "remembered".

   Finally, there is a set of optional information that MAY be stored
   about each identity that represent useful information for the user to
   have and could make an identity selector more usable.  Note that this
   list is neither intended to be exhaustive or even particularly
   correct; any implementer is free to use whatever make sense in their
   implementation and conforms to good HCI/UX guidelines.  Instead, it
   is simply a suggested starting point.

   o  Friendly name for identity: To allow the user to differentiate
      between the set of identities represented in the Identity
      Selector.  This should be editable by the user.  The only
      restriction on this name is that it MUST be unique within that
      particular user's set of identities.  For example: "My
      University", "Google Account", "Work Login", etc.

   o  Friendly icon for identity: To allow the user to differentiate
      between the set of identities they have they should be able to set
      an icon for that particular identity.

   o  Password changing URL: The URL the user should visit should they
      need to change their password for this particular identity.  For
      example, "http://www.example.com/passwordreset".

   o  Helpdesk URL: The URL the user should visit to get contact details
      for the helpdesk of the organisation that issued this particular
      identity for when the user encounters issues and needs help.  For
      example, https://www.example.com/helpdesk.

6.2.  Storage of Identity Information

   Since some of the information that makes up the identity is sensitive
   in nature (e.g. containing passwords), then this information SHOULD
   be stored and accessed securely.  This might involve ensuring the
   credential information is held in encrypted form on device and
   accessed using a passphrase.  For deeper integration into the system,
   this could be done by using existing secure storage on the system
   such as Keychain on a Mac or the GNOME keyring on a GNOME based Linux

6.3.  Adding/Association of an Identity

   Users will have one or more identities given to them by organisations
   that they have a relationship with.  One of the core tasks of an
   identity selector will be to learn about these identities in order to
   use them when it comes to authenticating to services on behalf of the
   user.  Adding these identities could be done in one of three ways:
   manual addition, automated addition that is manually triggered, or
   automated addition that is automatically triggered.  Each of these
   are discussed in more detail next.

   Note that the term "association" or "addition" of an identity is used
   rather than "provisioning" of an identity, because while we actually
   are provisioning identities into the UI, provisioning is an
   overloaded term in the identity and access management space and could
   easily be confused with identity provisioning in the sense of the
   creation of the identity by the home organisation's identity
   management procedures.

6.3.1.  Manual Addition

   Allowing users to manually add an identity is technically the easiest
   method to get this information, but it is a method that has the
   greatest usability drawbacks - including some that create potential
   security issues.  Most of the information required is relatively
   technical and finding some way of explaining what each field is to an
   non-technical audience is challenging (to say the least).  This
   especially is the case for trust anchor information.  Thus this
   method should be considered as a power-user option only, or as a
   fall-back should the other methods not be applicable.  Implementers
   may well decide not to offer the manual option due to these

   When this method is used, careful consideration should be given to
   the UI presented to the user.  The UI will have to ask for all of the
   information detailed in Section 6.1.

   There are two points at which a user could manually add an identity:

   o  Asynchronously: the user could be allowed to, at any time, trigger
      a workflow of manually adding an identity.  This represents the
      most flexible way of adding an identity since a user can perform
      this at any time.  It does, however, also have inherent issues
      when it comes to verifying the newly added identity - see
      Section 6.5.

   o  Just In Time: when connecting to a service which has no mapping to
      an existing identity, the user could be given an option to add a
      new one, as well as associating with an existing one.  This seems
      to present a better user experience when it comes to verifying the
      newly added identity (see Section 6.5), however, it represents a
      less direct method of adding an identity.  Users who have not yet
      added the appropriate identity to their identity selector may find
      it difficult to understand that they must try to access a
      particular service in order to add an identity.

   Of course, implementers could support both styles of identity
   addition to gain the benefits of both and give flexibility to the

   Finally, the area of verification of trust anchors is very important.
   An Identity Selector that allows for manual addition of identity
   information SHOULD try to ensure that trust anchor information is
   gathered and checked in a secure a manner as possible - where users
   have to enter and confirm all trust anchor information, or be
   required to explicitly agree to an insecure configuration if this is
   not done properly.

6.3.2.  Manually Triggered Automated Addition

   One way to bypass the need for manual addition of a user's identity -
   and all of the usability and security issues inherent with that
   approach - is to provide some sort of manually triggered, but
   automated, addition process.

   One approach to accomplishing this, for example, could be for an
   organisation to have a section on their website where their users
   could visit, enter the user part of their NAI, and be given piece of
   data that contains much or all of the relevant identity information
   for importing into the identity selector.

   It is reasonable to assume that any such automated addition service
   is likely to be organisation specific, so that the Issuing
   Organisation and realm part of the NAI will be constant, as would be
   the trust anchor information.  The user part of their NAI will have
   been input on the web service.  The password could be provided as a
   part of the provided data or the identity selector could prompt the
   user to enter it.

   Additionally, the user SHOULD be given the opportunity to:

   o  Supply or change the default friendly name for that identity - to
      allow the user to customise the identifier they use for that

   o  Indicate whether or not the identity selector should always ask
      before using services with this identity - to customise the way in
      which the identity selector interacts with the user with this
      particular identity;

   o  Reject the addition of the identity completely - to allow the user
      to back out of the association process in an intuitive way.

   In this case, trust anchors could be directly provided through the
   automated addition process to help establish the trust relationship
   in a secure manner.

6.3.3.  Fully Automated Addition

   Many organisations manage the machines of their users using
   enterprise management tools.  Such organisations may wish to be able
   to automatically add a particular user's identity to the identity
   selector on their machine/network account so that the user has to do

   This represents the best usability for the user - who wouldn't
   actually have to do anything.  However, it can only work on machines
   centrally managed by the organisation.

   Additionally, having an identity automatically provided, including
   its password, does have some particular usability issues.  Users are
   used to having to provide their username and password to access
   remote services.  When attempting to access services, authenticating
   to them completely transparently to the user could represent a source
   of confusion.  User training within an organisation to explain that
   automated population of their identity has been enabled is the only
   way to counter this.

6.4.  Modifying Identity Information

   This process is conceptually fairly similar to adding an identity,
   and thus shares many of the usability issues with that process.  Some
   particular things are discussed here.

6.4.1.  Manual Modification

   An identity selector may allow a user to manually modify some or all
   of the information associated with each identity.  The obvious item
   that SHOULD be allowed to be changed by the user is the password
   associated with the identity.

6.4.2.  Automated Modification

   To ease usability, organisations may wish to automatically provide
   updates to identity information.  For example, if the user's password
   changes it could automatically update the password for the identity
   in the user's identity selector, or if the trust anchor information
   changes (e.g. if a certificate is changed) it could be automatically
   pushed out to all users.

6.5.  Verifying an identity

   An inherent by-product of the ABFAB architecture is that an identity
   cannot be verified during the addition process; it can only be
   verified while it is in use with a real service.  This represents a
   definite usability issue no matter which method of identity addition
   is used (see Section 6.3):

   o  If the user has manually added the identity (see Section 6.3) they
      may have gone through the whole manual process with no errors and
      so believe the identity has been set up correctly.  However, when
      they attempt to access a service, they may be given an error
      message, thus causing some amount of confusion.

   o  If the user has had the identity populated into their identity
      selector, then there is a much greater chance of the identity
      information being correct.  However, if any of the information is
      not correct, then there is the potential for confusion as the user
      did not add the information in the first place.

   Also, if the identity information is incorrect the user may not know
   where the error lies, and the error messages provided by the process
   may not be helpful enough to indicate the error and how to fix it
   (see Section 8).

6.6.  Removing an Identity

   This is fairly similar to adding or modifying an identity, and thus
   shares many of the usability issues with those processes.  Some
   particular things are discussed here.

6.6.1.  Manual Removal

   Allowing the user to manually delete an identity is probably the best
   way to achieve the goal.  Any UI should allow for this option.

6.6.2.  Automated Removal

   While automated removal of an identity is a way of achieving the goal
   without having to interact with the user, the consequence is that
   things may disappear from the user's identity selector without them

6.7.  Storing an Identity with or without credentials

   Sometimes, a user may wish to have the identity they wish to use with
   a service stored by the identity selector, but not the credential
   (e.g. password) that goes along with that Identity.  The consequence
   of this is that when a user attempts to authenticate to a service for
   which an identity, but no credential, is stored, then the user would
   need to be prompted to manually enter the credential.

7.  Considerations around Management of Service to Identity Mappings

   A service to identity mapping tells the identity selector which
   identity should be used for a particular service.  There is
   potentially a many-to-many association between identities and
   services since a user may wish to use one of their identities for
   many services, or more than one identity for a single service (e.g.
   if they have multiple roles on that service).

   This potentially complex many-to-many association between identities
   and services is not easily comprehended by the user, and allowing the
   user to both manipulate it and control can be challenging.  These
   obstacles are especially common when errors occur after an
   association has been made.  In this scenario it is important that an
   identity can be disassociated with a service.

   To further complicate the picture, users may wish for:

   1.  The identity to service mapping to be stored along with the
       credential, i.e. the user should always be authenticated to a
       particular service with a particular identity with no prompting.

   2.  The identity to service mapping to be stored but not the
       credential, i.e. the user should not be prompted to choose the
       identity for a particular service, but should be prompted to
       enter their credential for that identity.

   3.  The identity to service mapping to not be stored, i.e. the user
       should be asked which identity to use every time they
       authenticate to a particular service.

7.1.  Associating a Service with an Identity

   There needs to be a way for the user to create the service to
   identity association.  It is advisable that this link be made only
   after the identity in question has authenticated with the service
   without any error.

   There are a few ways this association could happen.

7.1.1.  User-driven Manual Association

   There are two ways in which manual association of an identity to a
   service could happen:

   1.  The user could manually associate a particular service with a
       particular identity using the identity selector before they first
       attempt to use the service.  In order to do so, however, the user
       would need to know all the required technical details of that
       service beforehand, such as its GSS Acceptor Name.

   2.  On encountering a service new to the identity selector, the
       identity selector could pop up a dialogue box to the user asking
       if they would like to use an existing identity for this service
       (and might also allow them to create a new identity and use

7.1.2.  Automated Rules-based Association

   It would be beneficial from a usability perspective to minimise - or
   avoid entirely - situations where the user has to pick an identity
   for a particular service.  This could be accomplished by having rules
   to describe services and their mapping to identities.  Such a rule
   could match, for example, a particular identity for all IMAP servers,
   or a particular identity for all services in a given service realm.
   These rules could be configured as a part of the automated identity
   addition process described in Section 6.3.2 or Section 6.3.3

7.2.  Disassociating a Service with an Identity

   A user MUST be able to disassociate an identity with a service - that
   is, to be able to remove the mapping without having to remove the

   There should also be provision for the automated disassociation of an
   identity with a service for appropriate types of authentication

7.3.  Listing Services and Identities

   A service listing should be considered in the identity selector which
   is both searchable and editable by the user.

7.4.  Showing the Service that is requesting Authentication

   When a user is attempting to authenticate to a service for the first
   time, there should be some indication given to the user as to which
   service is requesting authentication.  In many cases, the service may
   be obvious (where the user has started the process of attempting to
   authenticate to a particular service), but in other cases this may
   not be obvious (e.g. if an authentication attempt is triggered by a
   timer or a specific event), and for this scenario some indication as
   to the requesting service is necessary.

7.5.  Showing the Identity currently in use

   It would be beneficial if, when using a service, the identity
   currently in use could be made visible to the user while they are
   using a specific service.  This allows the user to identify which
   identity is used with a particular service at a particular time (the
   user may have more than one identity that they could use with a
   particular service) - so that they can then disassociate the pairing.

   Implementing such a feature may be hard, however, due to the layered
   nature of the ABFAB transaction - the identity selector will
   certainly know when successful (or failed) authentications to a
   particular service have happened, but after that it typically plays
   no further part in the use of the service.  Therefore, knowing that a
   particular service is still using a particular identity in order to
   indicate this to the user would be challenging.

7.6.  Multiple Identities for a Particular Service

   An Identity Selector should be able to deal with the case where a
   user has multiple identities associated with a single service.  For
   example, upon receiving a request for authentication to a service
   that multiple identities are configured for, ask the user which of
   the identities should be used in this instance.

7.7.  Not using ABFAB for a Particular Service

   There may be cases where a user does not wish to use ABFAB based
   authentication at all to a particular service, even though it is
   ABFAB enabled.  To support this, the identity selector would have to
   allow the user to choose not to use ABFAB when they attempt to
   authenticate to a service.  It would be desirable if the user could
   also flag that this should be remembered.

8.  Handling of Errors


   Errors during the ABFAB authentication process can happen at any of
   the many layers - they could be GSS-API errors, EAP errors, RADIUS/
   RadSec errors, SAML errors, application errors, etc.  ABFAB based
   technologies are limited in error handling by the limitations in the
   protocols used.

   For example, all GSS-API calls need to be are necessarily instantiated from
   within the calling application.  For this reason reason, when an error
   occurs the user needs to be sent error is passed back to the application in order for it to
   deal with it.  To retry, the application needs to re-initiate the
   GSS-API call.  This can get
   tedious and cause  Unless the user application has been written to opt deal with
   this properly, this process can be very tedious for a user and cause
   them opt out of what they are trying to accomplish.  In addition to this
   this, the error messages themselves may not be useful enough for the
   user to decipher what has gone wrong.

   It is important

   Absent an improvement to try and avoid the error cases all together while using
   GSS-API as handling of these protocols,
   implementors of an ABFAB Identity Selector will need to work around
   these limitations.  Possible error messages conditions need to be considered,
   and error handling can really affect
   usability.  Another solution would decisions about what errors should be presented to alter the application user, and
   how, need to
   handle be made.

   To give an idea of the range of errors as it is instantiating that might be seen, consider
   the GSS-API communication.

   TODO: Lots more to discuss here...

8.1. following non-exhaustive set of potential errors.

   Identity Association/Verification Errors

   TODO: Errors:

   o  The credentials presented to the IdP were not able to be verified
      - e.g. wrong password, bad trust anchors, etc.  TODO.

8.2. username/password.

   o  The Trust Anchor for the IdP was invalid.

   Service Errors

   TODO: e.g. identity is correct Errors:

   o  The Identity might have been successfully authenticated by the
      IdP, but no authorisation.  TODO.

8.3. the user might not have authorisation to use the service
      they are attempting to use.

   Other Errors.

   TODO: e.g. network Errors:

   o  The IdP didn't respond to the Service.

   o  The IdP didn't respond to the Client.

   o  Network errors.

   o  Timing errors.  TODO.

9.  Handling of Successes

   It is of course hoped that the identity selector will have to
   occasionally handle successes as well as errors.  This section has
   some brief discussion about some areas you might want to think about.

9.1.  Reporting Authentication Success on First Use of Identity

   The first time an identity is used with a service, it would be good
   practice to visually indicate in some way that the process has been
   successful, in order that the user understands what is happening and
   is then prepared for future authentication attempts.

9.2.  Reporting Authentication Success

   On an on-going basis you may or may not wish to indicate visually to
   the user a successful authentication to a service.  This relates to
   Section 7.5.

10.  Other Considerations

   This section briefly discusses other considerations that you might
   want to think about that don't fit in any of the other categories.

10.1.  Identity Selector Taking Focus

   When an ABFAB authentication request is triggered, and where it needs
   input from the user, the Identity Selector should take focus in some
   way so that it is clear to the user that they need to do something to

10.2.  Import/Export of Credentials

   For various reasons, an identity selector implementation might want
   to include functionality that allows for the export/import of
   identities and service to identity mappings.  This could be for
   backup purposes, to allow a degree of mobility between identity
   selector instances, etc.

   If providing this functionality, it would be advisable that the
   credential store that is the result of the export should be secure -
   encrypted and password protected - given the nature of the

11.  Contributors

   The following individuals made important contributions to the text of
   this document: Sam Hartman (Painless Security LLC), and Maria Turk
   (Codethink Ltd).

12.  Acknowledgements

   Thanks to Jim Schaad, Stefan Winter, David Chadwick, Kevin Wasserman,
   Mark Donally, and Dave Crocker. Crocker, for feedback and suggestions.

13.  Security Considerations

   TODO: Bad trust anchors,

   Most security considerations are ones relevant to the use of GSS-EAP
   and are detailed in [I-D.ietf-abfab-arch].  There are, however, a few
   specific sets of security considerations related to the UI

   First, as discussed earlier, the Identity Selector should use a Trust
   Anchor to authenticate the IdP before it sends the users credentials
   to it.  Having no trust anchors, phishing.

14.  Privacy Considerations

   TODO: See Arch Trust Anchor information at all, or an incorrect
   Trust Anchor, can enable the possibility of someone spoofing the IdP
   and harvesting credentials sent to it.  So, how this Trust Anchor is
   configured and managed can have major security implications:

   o  The most secure way for general discussion.  Particular a Trust Anchor to UI - storing be configured is to have
      it provisioned alongside the other identity information in an
      enterprise provisioning scenario.  This allows for the correct
      Trust Anchor to be configured with no user input required.
      However, thought needs to be given to Trust Anchor expiry and
      consequent requirement for regular reprovisioning of identity

   o  Another way that is potentially secure would be to allow the user
      to discover the Trust Anchor information out of band and manually
      input this information into the Identity Selector.  This is only
      secure, however, for those users who understand what they're doing
      in this scenario; pragmatically, this is unlikely to be the case
      for many users so is not a recommended approach for the average

   o  A pragmatic approach would be leap of faith, whereby no Trust
      Anchor information is initially provisioned, and the first time
      the Identity Selector connects to the IdP it remembers the Trust
      Anchor information for future use.  This doesn't mitigate against
      spoofing of an IdP in the first instance, but would enable
      mitigation against it for all future connections.

   o  Finally, there may be interesting ways to leverage technologies
      such as DANE to store the Trust Anchor for an IdP in DNS.

   Secondly, the storage of the user's credentials on by the Identity
   Selector should be done in a particular device, mobility considerations.

15. secure manner to mitigate against people
   taking unauthorised control of the device being able to gather these
   credentials.  Use of a secure credential storage mechanism, such as
   the GNOME Keyring on Linux, or Keychain on the Mac, are recommended.

14.  IANA Considerations

   This document does not require actions by IANA.


15.  Normative References

   [RFC2119]                  Bradner, S., "Key words for use in RFCs to
                              Indicate Requirement Levels", BCP 14,
                              RFC 2119, March 1997.

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

   [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, May 2008.

   [I-D.ietf-abfab-arch]      Howlett, J., Hartman, S., Tschofenig, H.,
                              Lear, E., and J. Schaad, "Application
                              Bridging for Federated Access Beyond Web
                              (ABFAB) Architecture",
                              draft-ietf-abfab-arch-12 (work in
                              progress), February 2014.

   [I-D.ietf-abfab-usecases]  Smith, R., "Application Bridging for
                              Federated Access Beyond web (ABFAB) Use
                              Cases", draft-ietf-abfab-
              usecases-05 draft-ietf-abfab-usecases-05 (work
                              in progress), September 2012.

Appendix A.  Change Log

   Note to RFC Editor: if this document does not obsolete an existing
   RFC, please remove this appendix before publication as an RFC.

   IETF draft -01 to ietf draft -02

   1.  Tidying up language throughout.

   2.  Finished remaining TODOs - largely in the error handling section.

   3.  Added security considerations section.

   IETF draft -00 to ietf draft -01

   1.  Tidying up language throughout

   2.  Doing some of the TODOs

   3.  Added language that tries to explain that this document is not a
       substitute for good HCI/UX design.

   4.  Changed terminology slightly to avoid confusion between an
       identity selector "mechanism" and a GSS-API mechanism.

   5.  Added a caveat about the potential for the UI to show the
       identity currently in use for a particular service.

   6.  Added a requirement that the identity selector must not store the
       same NAI for multiple identities.

   7.  Stopped talking about "provisioning" after saying that I wouldn't
       talk about "provisioning".

   Draft -04 to ietf draft -00

   1.  Adding brief discussion of identities vs identifiers (Ken).

   2.  Changing assumption about credentials having a password in favour
       of more generic text for other auth types.

   3.  Adding discussion of storage of identity information.

   4.  Added sections on dealing with multiple identities per service,
       remembering credentials, remembering not to use ABFAB.

   5.  Added small section on ID selector needing to take focus in some

   Draft -03 to draft -04

   1.  Addressing various comments from Jim and Stefan.

   Draft -02 to draft -03

   1.  Bumping version to keep it alive.

   Draft -01 to draft -02

   1.  Completed the major consideration sections, lots of rewording

   Draft -00 to draft -01

   1.  None, republishing to refresh the document.  Other than adding
       this comment...

Appendix B.  Open Issues

   Note to RFC Editor: please remove this appendix before publication as
   an RFC.

Author's Address

   Dr. Rhys Smith
   Cardiff University
   39-41 Park Place
   Cardiff  CF10 3BB
   United Kingdom

   Phone: +44 29 2087 0126
   EMail: smith@cardiff.ac.uk