< draft-ietf-abfab-arch-06.txt   draft-ietf-abfab-arch-07.txt >
ABFAB J. Howlett ABFAB J. Howlett
Internet-Draft JANET(UK) Internet-Draft JANET(UK)
Intended status: Informational S. Hartman Intended status: Informational S. Hartman
Expires: October 20, 2013 Painless Security Expires: January 31, 2014 Painless Security
H. Tschofenig H. Tschofenig
Nokia Siemens Networks Nokia Siemens Networks
E. Lear E. Lear
Cisco Systems GmbH Cisco Systems GmbH
J. Schaad J. Schaad
Soaring Hawk Consulting Soaring Hawk Consulting
April 18, 2013 July 30, 2013
Application Bridging for Federated Access Beyond Web (ABFAB) Application Bridging for Federated Access Beyond Web (ABFAB)
Architecture Architecture
draft-ietf-abfab-arch-06.txt draft-ietf-abfab-arch-07.txt
Abstract Abstract
Over the last decade a substantial amount of work has occurred in the Over the last decade a substantial amount of work has occurred in the
space of federated access management. Most of this effort has space of federated access management. Most of this effort has
focused on two use cases: network access and web-based access. focused on two use cases: network access and web-based access.
However, the solutions to these use cases that have been proposed and However, the solutions to these use cases that have been proposed and
deployed tend to have few common building blocks in common. deployed tend to have few common building blocks in common.
This memo describes an architecture that makes use of extensions to This memo describes an architecture that makes use of extensions to
the commonly used security mechanisms for both federated and non- the commonly used security mechanisms for both federated and non-
federated access management, including the Remote Authentication Dial federated access management, including the Remote Authentication Dial
In User Service (RADIUS) and the Diameter protocol, the Generic In User Service (RADIUS) and the Diameter protocol, the Generic
Security Service (GSS), the GS2 family, the Extensible Authentication Security Service (GSS), the Extensible Authentication Protocol (EAP)
Protocol (EAP) and the Security Assertion Markup Language (SAML). and the Security Assertion Markup Language (SAML). The architecture
The architecture addresses the problem of federated access management addresses the problem of federated access management to primarily
to primarily non-web-based services, in a manner that will scale to non-web-based services, in a manner that will scale to large numbers
large numbers of identity providers, relying parties, and of identity providers, relying parties, and federations.
federations.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on October 20, 2013. This Internet-Draft will expire on January 31, 2014.
Copyright Notice Copyright Notice
Copyright (c) 2013 IETF Trust and the persons identified as the Copyright (c) 2013 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
skipping to change at page 2, line 31 skipping to change at page 2, line 34
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 5 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 5
1.1.1. Channel Binding . . . . . . . . . . . . . . . . . . . 6 1.1.1. Channel Binding . . . . . . . . . . . . . . . . . . . 6
1.2. An Overview of Federation . . . . . . . . . . . . . . . . 7 1.2. An Overview of Federation . . . . . . . . . . . . . . . . 7
1.3. Challenges for Contemporary Federation . . . . . . . . . 10 1.3. Challenges for Contemporary Federation . . . . . . . . . 10
1.4. An Overview of ABFAB-based Federation . . . . . . . . . . 10 1.4. An Overview of ABFAB-based Federation . . . . . . . . . . 11
1.5. Design Goals . . . . . . . . . . . . . . . . . . . . . . 13 1.5. Design Goals . . . . . . . . . . . . . . . . . . . . . . 14
2. Architecture . . . . . . . . . . . . . . . . . . . . . . . . 14 2. Architecture . . . . . . . . . . . . . . . . . . . . . . . . 14
2.1. Relying Party to Identity Provider . . . . . . . . . . . 15 2.1. Relying Party to Identity Provider . . . . . . . . . . . 16
2.1.1. AAA, RADIUS and Diameter . . . . . . . . . . . . . . 16 2.1.1. AAA, RADIUS and Diameter . . . . . . . . . . . . . . 17
2.1.2. Discovery and Rules Determination . . . . . . . . . . 18 2.1.2. Discovery and Rules Determination . . . . . . . . . . 18
2.1.3. Routing and Technical Trust . . . . . . . . . . . . . 19 2.1.3. Routing and Technical Trust . . . . . . . . . . . . . 19
2.1.4. AAA Security . . . . . . . . . . . . . . . . . . . . 20 2.1.4. AAA Security . . . . . . . . . . . . . . . . . . . . 20
2.1.5. SAML Assertions . . . . . . . . . . . . . . . . . . . 21 2.1.5. SAML Assertions . . . . . . . . . . . . . . . . . . . 21
2.2. Client To Identity Provider . . . . . . . . . . . . . . . 23 2.2. Client To Identity Provider . . . . . . . . . . . . . . . 23
2.2.1. Extensible Authentication Protocol (EAP) . . . . . . 23 2.2.1. Extensible Authentication Protocol (EAP) . . . . . . 23
2.2.2. EAP Channel Binding . . . . . . . . . . . . . . . . . 25 2.2.2. EAP Channel Binding . . . . . . . . . . . . . . . . . 25
2.3. Client to Relying Party . . . . . . . . . . . . . . . . . 25 2.3. Client to Relying Party . . . . . . . . . . . . . . . . . 25
2.3.1. GSS-API . . . . . . . . . . . . . . . . . . . . . . . 26 2.3.1. GSS-API . . . . . . . . . . . . . . . . . . . . . . . 26
2.3.2. Protocol Transport . . . . . . . . . . . . . . . . . 27 2.3.2. Protocol Transport . . . . . . . . . . . . . . . . . 27
2.3.3. Reauthentication . . . . . . . . . . . . . . . . . . 28 2.3.3. Reauthentication . . . . . . . . . . . . . . . . . . 27
3. Application Security Services . . . . . . . . . . . . . . . . 28 3. Application Security Services . . . . . . . . . . . . . . . . 28
3.1. Authentication . . . . . . . . . . . . . . . . . . . . . 28 3.1. Authentication . . . . . . . . . . . . . . . . . . . . . 28
3.2. GSS-API Channel Binding . . . . . . . . . . . . . . . . . 29 3.2. GSS-API Channel Binding . . . . . . . . . . . . . . . . . 29
3.3. Host-Based Service Names . . . . . . . . . . . . . . . . 30 3.3. Host-Based Service Names . . . . . . . . . . . . . . . . 30
3.4. Additional GSS-API Services . . . . . . . . . . . . . . . 32 3.4. Additional GSS-API Services . . . . . . . . . . . . . . . 32
4. Privacy Considerations . . . . . . . . . . . . . . . . . . . 32 4. Privacy Considerations . . . . . . . . . . . . . . . . . . . 32
4.1. Entities and their roles . . . . . . . . . . . . . . . . 33 4.1. Entities and their roles . . . . . . . . . . . . . . . . 33
4.2. Privacy Aspects of ABFAB Communication Flows . . . . . . 34 4.2. Privacy Aspects of ABFAB Communication Flows . . . . . . 34
4.2.1. Client to RP . . . . . . . . . . . . . . . . . . . . 34 4.2.1. Client to RP . . . . . . . . . . . . . . . . . . . . 34
4.2.2. Client to IdP (via Federation Substrate) . . . . . . 35 4.2.2. Client to IdP (via Federation Substrate) . . . . . . 35
4.2.3. IdP to RP (via Federation Substrate) . . . . . . . . 36 4.2.3. IdP to RP (via Federation Substrate) . . . . . . . . 36
4.3. Relationship between User and Entities . . . . . . . . . 36 4.3. Relationship between User and Entities . . . . . . . . . 37
4.4. Accounting Information . . . . . . . . . . . . . . . . . 37 4.4. Accounting Information . . . . . . . . . . . . . . . . . 37
4.5. Collection and retention of data and identifiers . . . . 37 4.5. Collection and retention of data and identifiers . . . . 37
4.6. User Participation . . . . . . . . . . . . . . . . . . . 38 4.6. User Participation . . . . . . . . . . . . . . . . . . . 38
5. Deployment Considerations . . . . . . . . . . . . . . . . . . 38 5. Security Considerations . . . . . . . . . . . . . . . . . . . 38
5.1. EAP Channel Binding . . . . . . . . . . . . . . . . . . . 38 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 39
5.2. AAA Proxy Behavior . . . . . . . . . . . . . . . . . . . 38 7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 39
6. Security Considerations . . . . . . . . . . . . . . . . . . . 38 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 40
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 40 8.1. Normative References . . . . . . . . . . . . . . . . . . 40
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 40 8.2. Informative References . . . . . . . . . . . . . . . . . 41
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 40
9.1. Normative References . . . . . . . . . . . . . . . . . . 40
9.2. Informative References . . . . . . . . . . . . . . . . . 41
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 43 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 43
1. Introduction 1. Introduction
The Internet uses numerous security mechanisms to manage access to The Internet uses numerous security mechanisms to manage access to
various resources. These mechanisms have been generalized and scaled various resources. These mechanisms have been generalized and scaled
over the last decade through mechanisms such as Simple Authentication over the last decade through mechanisms such as Simple Authentication
and Security Layer (SASL) with the Generic Security Server and Security Layer (SASL) with the Generic Security Server
Application Program Interface (GSS-API) (known as the GS2 family) Application Program Interface (GSS-API) (known as the GS2 family)
[RFC5801], Security Assertion Markup Language (SAML) [RFC5801], Security Assertion Markup Language (SAML)
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Federated access management has evolved over the last decade through Federated access management has evolved over the last decade through
specifications like SAML [OASIS.saml-core-2.0-os], OpenID [1], OAuth specifications like SAML [OASIS.saml-core-2.0-os], OpenID [1], OAuth
[RFC5849], [I-D.ietf-oauth-v2] and WS-Trust [WS-TRUST]. The benefits [RFC5849], [I-D.ietf-oauth-v2] and WS-Trust [WS-TRUST]. The benefits
of federated access management include: of federated access management include:
Single or Simplified sign-on: Single or Simplified sign-on:
An Internet service can delegate access management, and the An Internet service can delegate access management, and the
associated responsibilities such as identity management and associated responsibilities such as identity management and
credentialing, to an organization that already has a long-term credentialing, to an organization that already has a long-term
relationship with the Client. This is often attractive for relationship with the Client. This is often attractive as Relying
Relying Parties who frequently do not want these responsibilities. Parties frequently do not want these responsibilities. The Client
The Client also requires fewer credentials, which is also also requires fewer credentials, which is also desirable.
desirable.
Data Minimization and User Participation: Data Minimization and User Participation:
Often a Relying Party does not need to know the identity of a Often a Relying Party does not need to know the identity of a
Client to reach an access management decision. It is frequently Client to reach an access management decision. It is frequently
only necessary for the Relying Party know specific attributes only necessary for the Relying Party know specific attributes
about the subject, for example, that the Subject is affiliated about the client, for example, that the client is affiliated with
with a particular organization or has a certain role or a particular organization or has a certain role or entitlement.
entitlement. Sometimes the RP only needs to know a pseudonym of Sometimes the RP only needs to know a pseudonym of the client.
the Subject.
Prior to the release of attributes to the RP from the IdP, the IdP Prior to the release of attributes to the RP from the IdP, the IdP
will check configuration and policy to determine if the attributes will check configuration and policy to determine if the attributes
are to be released. There is currently no direct client are to be released. There is currently no direct client
participation in this decision. participation in this decision.
Provisioning: Provisioning:
Sometimes a Relying Party needs, or would like, to know more about Sometimes a Relying Party needs, or would like, to know more about
a client than an affiliation or a pseudonym. For example, a a client than an affiliation or a pseudonym. For example, a
Relying Party may want the Client's email address or name. Some Relying Party may want the Client's email address or name. Some
federated access management technologies provide the ability for federated access management technologies provide the ability for
the IdP to supply this information, either on request by the RP or the IdP to supply this information, either on request by the RP or
unsolicited. unsolicited.
This memo describes the Application Bridging for Federated Access This memo describes the Application Bridging for Federated Access
Beyond the Web (ABFAB) architecture. This architecture makes use of Beyond the Web (ABFAB) architecture. This architecture makes use of
extensions to the commonly used security mechanisms for both extensions to the commonly used security mechanisms for both
federated and non-federated access management, including the RADIUS federated and non-federated access management, including the RADIUS
and the Diameter protocols, the Generic Security Service (GSS), the and the Diameter protocols, the Generic Security Service (GSS), the
GS2 family, the Extensible Authentication Protocol (EAP) and SAML. Extensible Authentication Protocol (EAP) and SAML. The architecture
The architecture addresses the problem of federated access management addresses the problem of federated access management primarily for
primarily for non-web-based services. It does so in a manner that non-web-based services. It does so in a manner that will scale to
will scale to large numbers of identity providers, relying parties, large numbers of identity providers, relying parties, and
and federations. federations.
1.1. Terminology 1.1. Terminology
This document uses identity management and privacy terminology from This document uses identity management and privacy terminology from
[I-D.iab-privacy-considerations]. In particular, this document uses [I-D.iab-privacy-considerations]. In particular, this document uses
the terms identity provider, relying party, identifier, pseudonymity, the terms identity provider, relying party, identifier, pseudonymity,
unlinkability, and anonymity. unlinkability, and anonymity.
In this architecture the IdP consists of the following components: an In this architecture the IdP consists of the following components: an
EAP server, a RADIUS or a Diameter server, and optionally a SAML EAP server, a RADIUS or a Diameter server, and optionally a SAML
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One of the problems people will find with reading this document is One of the problems people will find with reading this document is
that the terminology sometimes appears to be inconsistent. This is that the terminology sometimes appears to be inconsistent. This is
due the fact that the terms used by the different standards we are due the fact that the terms used by the different standards we are
referencing are not consistent. In general the document uses either referencing are not consistent. In general the document uses either
a the ABFAB term or the term associated with the standard under a the ABFAB term or the term associated with the standard under
discussion as appropriate. For reference we include this table which discussion as appropriate. For reference we include this table which
maps the different terms into a single table. maps the different terms into a single table.
+--------------+--------------+-----------------+-------------------+ +--------------+--------------+-----------------+-------------------+
| Protocol | Subject | Relying Party | Identity Provider | | Protocol | Client | Relying Party | Identity Provider |
+--------------+--------------+-----------------+-------------------+ +--------------+--------------+-----------------+-------------------+
| ABFAB | Client | Relying Party | Identity Provider | | ABFAB | Client | Relying Party | Identity Provider |
| | | (RP) | (IdP) | | | | (RP) | (IdP) |
| | | | | | | | | |
| | Initiator | Acceptor | | | | Initiator | Acceptor | |
| | | | | | | | | |
| | | Server | | | | | Server | |
| | | | | | | | | |
| SAML | Subject | Service | Issuer | | SAML | Subject | Service | Issuer |
| | | Provider | | | | | Provider | |
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| GSS-API | Initiator | Acceptor | | | GSS-API | Initiator | Acceptor | |
| | | | | | | | | |
| EAP | EAP peer | | EAP server | | EAP | EAP peer | | EAP server |
| | | | | | | | | |
| AAA | | AAA Client | AAA server | | AAA | | AAA Client | AAA server |
| | | | | | | | | |
| RADIUS | user | NAS | RADIUS server | | RADIUS | user | NAS | RADIUS server |
| | | | | | | | | |
| | | RADIUS client | | | | | RADIUS client | |
+--------------+--------------+-----------------+-------------------+ +--------------+--------------+-----------------+-------------------+
Note that in some cases a cell has been left empty; in these cases Note that in some cases a cell has been left empty; in these cases
there is no direct name that represents this concept. there is no name that represents the entity.
1.1.1. Channel Binding 1.1.1. Channel Binding
This document uses the term channel binding with two different This document uses the term channel binding with two different
meanings. meanings.
EAP channel binding is used to provide GSS-API naming semantics. EAP channel binding is used to provide GSS-API naming semantics.
Channel binding sends a set of attributes from the peer to the EAP Channel binding sends a set of attributes from the peer to the EAP
server either as part of the EAP conversation or as part of a secure server either as part of the EAP conversation or as part of a secure
association protocol. In addition, attributes are sent in the association protocol. In addition, attributes are sent in the
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without qualification refers to EAP channel binding. without qualification refers to EAP channel binding.
GSS-API channel binding provides protection against man-in-the-middle GSS-API channel binding provides protection against man-in-the-middle
attacks when GSS-API is used for authentication inside of some attacks when GSS-API is used for authentication inside of some
tunnel; it is similar to a facility called cryptographic binding in tunnel; it is similar to a facility called cryptographic binding in
EAP. The binding works by each side deriving a cryptographic value EAP. The binding works by each side deriving a cryptographic value
from the tunnel itself and then using that cryptographic value to from the tunnel itself and then using that cryptographic value to
prove to the other side that it knows the value. prove to the other side that it knows the value.
See [RFC5056] for a discussion of the differences between these two See [RFC5056] for a discussion of the differences between these two
facilities. facilities. However, the difference can be summarized as GSS-API
channel binding says that there is nobody between the client and the
authenticator while EAP channel binding allows the client to have
knowledge about attributes of the authenticator (such as it's name).
Typically when considering channel binding, people think of channel Typically when considering channel binding, people think of channel
binding in combination with mutual authentication. This is binding in combination with mutual authentication. This is
sufficiently common that without additional qualification channel sufficiently common that without additional qualification channel
binding should be assumed to imply mutual authentication. Without binding should be assumed to imply mutual authentication. Without
mutual authentication, only one party knows that the endpoints are mutual authentication, only one party knows that the endpoints are
correct. That's sometimes useful. Consider for example a user who correct. That's sometimes useful. Consider for example a user who
wishes to access a protected resource from a shared whiteboard in a wishes to access a protected resource from a shared whiteboard in a
conference room. The whiteboard is the initiator; it does not need conference room. The whiteboard is the initiator; it does not need
to actually authenticate that it is talking to the correct resource to actually authenticate that it is talking to the correct resource
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There is a direct relationship between the Client and the Identity There is a direct relationship between the Client and the Identity
Provider by which the entities trust and can securely authenticate Provider by which the entities trust and can securely authenticate
each other. each other.
A federation agreement typically encompasses operational A federation agreement typically encompasses operational
specifications and legal rules: specifications and legal rules:
Operational Specifications: Operational Specifications:
These include the technical specifications (e.g. protocols used These include the technical specifications (e.g. protocols used to
to communicate between the three parties), process standards, communicate between the three parties), process standards,
policies, identity proofing, credential and authentication policies, identity proofing, credential and authentication
algorithm requirements, performance requirements, assessment and algorithm requirements, performance requirements, assessment and
audit criteria, etc. The goal of operational specifications is to audit criteria, etc. The goal of operational specifications is to
provide enough definition that the system works and provide enough definition that the system works and
interoperability is possible. interoperability is possible.
Legal Rules: Legal Rules:
The legal rules take the legal framework into consideration and The legal rules take the legal framework into consideration and
provide contractual obligations for each entity. The rules define provide contractual obligations for each entity. The rules define
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The IdP will typically have a long-term relationship with the Client. The IdP will typically have a long-term relationship with the Client.
This relationship typically involves the IdP positively identifying This relationship typically involves the IdP positively identifying
and credentialing the Client (for example, at time of employment and credentialing the Client (for example, at time of employment
within an organization). When dealing with individuals, this process within an organization). When dealing with individuals, this process
is called identity proofing [NIST-SP.800-63]. The relationship will is called identity proofing [NIST-SP.800-63]. The relationship will
often be instantiated within an agreement between the IdP and the often be instantiated within an agreement between the IdP and the
Client (for example, within an employment contract or terms of use Client (for example, within an employment contract or terms of use
that stipulates the appropriate use of credentials and so forth). that stipulates the appropriate use of credentials and so forth).
The nature and quality of the relationship between the Subject and The nature and quality of the relationship between the Client and the
the IdP is an important contributor to the level of trust that an RP IdP is an important contributor to the level of trust that an RP may
may attribute to an assertion describing a Client made by an IdP. attribute to an assertion describing a Client made by an IdP. This
This is sometimes described as the Level of Assurance is sometimes described as the Level of Assurance [NIST-SP.800-63].
[NIST-SP.800-63].
Federation does not require an a priori relationship or a long-term Federation does not require an a priori relationship or a long-term
relationship between the RP and the Client; it is this property of relationship between the RP and the Client; it is this property of
federation that yields many of its benefits. However, federation federation that yields many of its benefits. However, federation
does not preclude the possibility of a pre-existing relationship does not preclude the possibility of a pre-existing relationship
between the RP and the Client, nor that they may use the introduction between the RP and the Client, nor that they may use the introduction
to create a new long-term relationship independent of the federation. to create a new long-term relationship independent of the federation.
Finally, it is important to reiterate that in some scenarios there Finally, it is important to reiterate that in some scenarios there
might indeed be an Individual behind the Client and in other cases might indeed be an Individual behind the Client and in other cases
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to allow for such ambiguities. For instance, in the case of an email to allow for such ambiguities. For instance, in the case of an email
provider, the use of SMTP and IMAP protocols do not have the ability provider, the use of SMTP and IMAP protocols do not have the ability
for the server to get additional information, beyond the clients NAI, for the server to get additional information, beyond the clients NAI,
in order to provide additional input to decide between multiple in order to provide additional input to decide between multiple
federations it may be associated with. However, the building blocks federations it may be associated with. However, the building blocks
do exist to add this functionality. do exist to add this functionality.
1.4. An Overview of ABFAB-based Federation 1.4. An Overview of ABFAB-based Federation
The previous section described the general model of federation, and The previous section described the general model of federation, and
the application of federated access management. This section the application of access management within the federation. This
provides a brief overview of ABFAB in the context of this model. section provides a brief overview of ABFAB in the context of this
model.
In this example, a client is attempting to connect to a server in In this example, a client is attempting to connect to a server in
order to either get access to some data or perform some type of order to either get access to some data or perform some type of
transaction. In order for the client to mutually authenticate with transaction. In order for the client to mutually authenticate with
the server, the following steps are taken in an ABFAB federated the server, the following steps are taken in an ABFAB federated
architecture: architecture:
1. Client Configuration: The Client Application is configured with 1. Client Configuration: The Client Application is configured with
an NAI assigned by the IdP. It is also configured with any an NAI assigned by the IdP. It is also configured with any
keys, certificates, passwords or other secret and public keys, certificates, passwords or other secret and public
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protocol, the client sends a channel bindings EAP message to the protocol, the client sends a channel bindings EAP message to the
IdP (Section 2.2.2). In the channel binding message the client IdP (Section 2.2.2). In the channel binding message the client
identifies, among other things, the RP to which it is attempting identifies, among other things, the RP to which it is attempting
to authenticate. The IdP checks the channel binding data from to authenticate. The IdP checks the channel binding data from
the client with that provided by the RP via the AAA protocol. the client with that provided by the RP via the AAA protocol.
If the bindings do not match the IdP sends an EAP failure If the bindings do not match the IdP sends an EAP failure
message to the RP. message to the RP.
8. Successful EAP Authentication: At this point, the IdP (EAP 8. Successful EAP Authentication: At this point, the IdP (EAP
server) and client (EAP peer) have mutually authenticated each server) and client (EAP peer) have mutually authenticated each
other. As a result, the subject and the IdP hold two other. As a result, the client and the IdP hold two
cryptographic keys: a Master Session Key (MSK), and an Extended cryptographic keys: a Master Session Key (MSK), and an Extended
MSK (EMSK). At this point the client has a level of assurance MSK (EMSK). At this point the client has a level of assurance
about the identity of the RP based on the name checking the IdP about the identity of the RP based on the name checking the IdP
has done using the RP naming information from the AAA framework has done using the RP naming information from the AAA framework
and from the client (by the channel binding data). and from the client (by the channel binding data).
9. Local IdP Policy Check: At this stage, the IdP checks local 9. Local IdP Policy Check: At this stage, the IdP checks local
policy to determine whether the RP and client are authorized for policy to determine whether the RP and client are authorized for
a given transaction/service, and if so, what if any, attributes a given transaction/service, and if so, what if any, attributes
will be released to the RP. If the IdP gets a policy failure, will be released to the RP. If the IdP gets a policy failure,
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did not expand on the specifics of providing support for non-Web did not expand on the specifics of providing support for non-Web
based applications. This section details this aspect and motivates based applications. This section details this aspect and motivates
design decisions. The main theme of the work described in this design decisions. The main theme of the work described in this
document is focused on re-using existing building blocks that have document is focused on re-using existing building blocks that have
been deployed already and to re-arrange them in a novel way. been deployed already and to re-arrange them in a novel way.
Although this architecture assumes updates to the relying party, the Although this architecture assumes updates to the relying party, the
client application, and the Identity Provider, those changes are kept client application, and the Identity Provider, those changes are kept
at a minimum. A mechanism that can demonstrate deployment benefits at a minimum. A mechanism that can demonstrate deployment benefits
(based on ease of update of existing software, low implementation (based on ease of update of existing software, low implementation
effort, etc.) is preferred and there may be a need to specify effort, etc.) is preferred and there may be a need to specify
multiple mechanisms to support the range of different deployment multiple mechanisms to support the range of different deployment
scenarios. scenarios.
There are a number of ways for encapsulating EAP into an application There are a number of ways for encapsulating EAP into an application
protocol. For ease of integration with a wide range of non-Web based protocol. For ease of integration with a wide range of non-Web based
application protocols the usage of the GSS-API was chosen. A application protocols the usage of the GSS-API was chosen. A
description of the technical specification can be found in description of the technical specification can be found in
[I-D.ietf-abfab-gss-eap]. [I-D.ietf-abfab-gss-eap].
The architecture consists of several building blocks, which is shown The architecture consists of several building blocks, which is shown
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2.1.1. AAA, RADIUS and Diameter 2.1.1. AAA, RADIUS and Diameter
Interestingly, for network access authentication the usage of the AAA Interestingly, for network access authentication the usage of the AAA
framework with RADIUS [RFC2865] and Diameter [RFC3588] was quite framework with RADIUS [RFC2865] and Diameter [RFC3588] was quite
successful from a deployment point of view. To map to the successful from a deployment point of view. To map to the
terminology used in Figure 1 to the AAA framework the IdP corresponds terminology used in Figure 1 to the AAA framework the IdP corresponds
to the AAA server, the RP corresponds to the AAA client, and the to the AAA server, the RP corresponds to the AAA client, and the
technical building blocks of a federation are AAA proxies, relays and technical building blocks of a federation are AAA proxies, relays and
redirect agents (particularly if they are operated by third parties, redirect agents (particularly if they are operated by third parties,
such as AAA brokers and clearing houses). The front-end, i.e. the such as AAA brokers and clearing houses). The front-end, i.e. the
end host to AAA client communication, is in case of network access end host to AAA client communication, is in case of network access
authentication offered by link layer protocols that forward authentication offered by link layer protocols that forward
authentication protocol exchanges back-and-forth. An example of a authentication protocol exchanges back-and-forth. An example of a
large scale RADIUS-based federation is EDUROAM [2]. large scale RADIUS-based federation is EDUROAM [2].
By using the AAA framework, ABFAB gets a lot of mileage as many of By using the AAA framework, ABFAB gets a lot of mileage as many of
the federation agreements already exist and merely need to be the federation agreements already exist and merely need to be
expanded to cover the ABFAB additions. The AAA framework has already expanded to cover the ABFAB additions. The AAA framework has already
addressed some of the problems outlined above. For example, addressed some of the problems outlined above. For example,
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identity provider can establish technical trust that messages are identity provider can establish technical trust that messages are
being sent by the appropriate relying party. Any given interaction being sent by the appropriate relying party. Any given interaction
will be associated with one federation at the policy level. The will be associated with one federation at the policy level. The
legal or business relationship defines what statements the identity legal or business relationship defines what statements the identity
provider is trusted to make and how these statements are interpreted provider is trusted to make and how these statements are interpreted
by the relying party. The AAA framework also permits the relying by the relying party. The AAA framework also permits the relying
party or elements between the relying party and identity provider to party or elements between the relying party and identity provider to
make statements about the relying party. make statements about the relying party.
The AAA framework provides transport for attributes. Statements made The AAA framework provides transport for attributes. Statements made
about the subject by the identity provider, statements made about the about the client by the identity provider, statements made about the
relying party and other information are transported as attributes. relying party and other information are transported as attributes.
One demand that the AAA substrate makes of the upper layers is that One demand that the AAA substrate makes of the upper layers is that
they must properly identify the end points of the communication. It they must properly identify the end points of the communication. It
must be possible for the AAA client at the RP to determine where to must be possible for the AAA client at the RP to determine where to
send each RADIUS or Diameter message. Without this requirement, it send each RADIUS or Diameter message. Without this requirement, it
would be the RP's responsibility to determine the identity of the would be the RP's responsibility to determine the identity of the
client on its own, without the assistance of an IdP. This client on its own, without the assistance of an IdP. This
architecture makes use of the Network Access Identifier (NAI), where architecture makes use of the Network Access Identifier (NAI), where
the IdP is indicated by the realm component [I-D.ietf-radext-nai]. the IdP is indicated by the realm component [I-D.ietf-radext-nai].
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ABFAB selected EAP for the purposes of mutual authentication and ABFAB selected EAP for the purposes of mutual authentication and
assisted in creating some new EAP channel binding documents for assisted in creating some new EAP channel binding documents for
dealing with determining the identity of the RP. A framework for the dealing with determining the identity of the RP. A framework for the
channel binding mechanism has been defined in RFC 6677 [RFC6677] that channel binding mechanism has been defined in RFC 6677 [RFC6677] that
allows the IdP to check the identity of the RP provided by the AAA allows the IdP to check the identity of the RP provided by the AAA
framework with that provided by the client. framework with that provided by the client.
2.2.1. Extensible Authentication Protocol (EAP) 2.2.1. Extensible Authentication Protocol (EAP)
Traditional web federation does not describe how a subject interacts Traditional web federation does not describe how a client interacts
with an identity provider for authentication. As a result, this with an identity provider for authentication. As a result, this
communication is not standardized. There are several disadvantages communication is not standardized. There are several disadvantages
to this approach. Since the communication is not standardized, it is to this approach. Since the communication is not standardized, it is
difficult for machines to correctly enter their credentials with difficult for machines to correctly enter their credentials with
different authentications, where Individuals can correctly identify different authentications, where Individuals can correctly identify
the entire mechanism on the fly. The use of browsers for the entire mechanism on the fly. The use of browsers for
authentication restricts the deployment of more secure forms of authentication restricts the deployment of more secure forms of
authentication beyond plaintext username and password known by the authentication beyond plaintext username and password known by the
server. In a number of cases the authentication interface may be server. In a number of cases the authentication interface may be
presented before the subject has adequately validated they are presented before the client has adequately validated they are talking
talking to the intended server. By giving control of the to the intended server. By giving control of the authentication
authentication interface to a potential attacker, the security of the interface to a potential attacker, the security of the system may be
system may be reduced and phishing opportunities introduced. reduced and phishing opportunities introduced.
As a result, it is desirable to choose some standardized approach for As a result, it is desirable to choose some standardized approach for
communication between the subject's end-host and the identity communication between the client's end-host and the identity
provider. There are a number of requirements this approach must provider. There are a number of requirements this approach must
meet. meet.
Experience has taught us one key security and scalability Experience has taught us one key security and scalability
requirement: it is important that the relying party not get requirement: it is important that the relying party not get
possession of the long-term secret of the client. Aside from a possession of the long-term secret of the client. Aside from a
valuable secret being exposed, a synchronization problem can develop valuable secret being exposed, a synchronization problem can develop
when the client changes keys with the IdP. when the client changes keys with the IdP.
Since there is no single authentication mechanism that will be used Since there is no single authentication mechanism that will be used
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tokens while others use passwords. A service provider wants to tokens while others use passwords. A service provider wants to
provide support for both authentication methods, and other methods provide support for both authentication methods, and other methods
from IdPs not yet seen. from IdPs not yet seen.
These requirements can be met by utilizing standardized and These requirements can be met by utilizing standardized and
successfully deployed technology, namely by the Extensible successfully deployed technology, namely by the Extensible
Authentication Protocol (EAP) framework [RFC3748]. Figure 2 Authentication Protocol (EAP) framework [RFC3748]. Figure 2
illustrates the integration graphically. illustrates the integration graphically.
EAP is an end-to-end framework; it provides for two-way communication EAP is an end-to-end framework; it provides for two-way communication
between a peer (i.e. client or individual) through the authenticator between a peer (i.e. client or individual) through the authenticator
(i.e., relying party) to the back-end (i.e., identity provider). (i.e., relying party) to the back-end (i.e., identity provider).
Conveniently, this is precisely the communication path that is needed Conveniently, this is precisely the communication path that is needed
for federated identity. Although EAP support is already integrated for federated identity. Although EAP support is already integrated
in AAA systems (see [RFC3579] and [RFC4072]) several challenges in AAA systems (see [RFC3579] and [RFC4072]) several challenges
remain: remain:
o The first is how to carry EAP payloads from the end host to the o The first is how to carry EAP payloads from the end host to the
relying party. relying party.
o Another is to verify statements the relying party has made to the o Another is to verify statements the relying party has made to the
subject, confirm these statements are consistent with statements client, confirm these statements are consistent with statements
made to the identity provider and confirm all the above are made to the identity provider and confirm all the above are
consistent with the federation and any federation-specific policy consistent with the federation and any federation-specific policy
or configuration. or configuration.
o Another challenge is choosing which identity provider to use for o Another challenge is choosing which identity provider to use for
which service. which service.
The EAP method used for ABFAB needs to meet the following The EAP method used for ABFAB needs to meet the following
requirements: requirements:
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Authentication and Security Layer (SASL) [RFC4422] framework. These Authentication and Security Layer (SASL) [RFC4422] framework. These
two approaches work together nicely: by creating a GSS-API mechanism, two approaches work together nicely: by creating a GSS-API mechanism,
SASL integration is also addressed. In effect, using a GSS-API SASL integration is also addressed. In effect, using a GSS-API
mechanism with SASL simply requires placing some headers on the front mechanism with SASL simply requires placing some headers on the front
of the mechanism and constraining certain GSS-API options. of the mechanism and constraining certain GSS-API options.
GSS-API is specified in terms of an abstract set of operations which GSS-API is specified in terms of an abstract set of operations which
can be mapped into a programming language to form an API. When can be mapped into a programming language to form an API. When
people are first introduced to GSS-API, they focus on it as an API. people are first introduced to GSS-API, they focus on it as an API.
However, from the prospective of authentication for non-web However, from the prospective of authentication for non-web
applications, GSS-API should be thought of as a protocol not an API. applications, GSS-API should be thought of as a protocol as well as
It consists of some abstract operations such as the initial context an API. When looked at as a protocol, it consists of abstract
exchange, which includes two sub-operations (gss_init_sec_context and operations such as the initial context exchange, which includes two
gss_accept_sec_context). An application defines which abstract sub-operations (gss_init_sec_context and gss_accept_sec_context). An
operations it is going to use and where messages produced by these application defines which abstract operations it is going to use and
operations fit into the application architecture. A GSS-API where messages produced by these operations fit into the application
mechanism will define what actual protocol messages result from that architecture. A GSS-API mechanism will define what actual protocol
abstract message for a given abstract operation. So, since this work messages result from that abstract message for a given abstract
is focusing on a particular GSS-API mechanism, we generally focus on operation. So, since this work is focusing on a particular GSS-API
protocol elements rather than the API view of GSS-API. mechanism, we generally focus on protocol elements rather than the
API view of GSS-API.
The API view has significant value. Since the abstract operations The API view of GSS-API does have significant value as well, since
are well defined, the set of information that a mechanism gets from the abstract operations are well defined, the set of information that
the application is well defined. Also, the set of assumptions the a mechanism gets from the application is well defined. Also, the set
application is permitted to make is generally well defined. As a of assumptions the application is permitted to make is generally well
result, an application protocol that supports GSS-API or SASL is very defined. As a result, an application protocol that supports GSS-API
likely to be usable with a new approach to authentication including or SASL is very likely to be usable with a new approach to
this one with no required modifications. In some cases, support for authentication including this one with no required modifications. In
a new authentication mechanism has been added using plugin interfaces some cases, support for a new authentication mechanism has been added
to applications without the application being modified at all. Even using plugin interfaces to applications without the application being
when modifications are required, they can often be limited to modified at all. Even when modifications are required, they can
supporting a new naming and authorization model. For example, this often be limited to supporting a new naming and authorization model.
work focuses on privacy; an application that assumes it will always For example, this work focuses on privacy; an application that
obtain an identifier for the client will need to be modified to assumes it will always obtain an identifier for the client will need
support anonymity, unlinkability or pseudonymity. to be modified to support anonymity, unlinkability or pseudonymity.
So, we use GSS-API and SASL because a number of the application So, we use GSS-API and SASL because a number of the application
protocols we wish to federate support these strategies for security protocols we wish to federate support these strategies for security
integration. What does this mean from a protocol standpoint and how integration. What does this mean from a protocol standpoint and how
does this relate to other layers? This means we need to design a does this relate to other layers? This means we need to design a
concrete GSS-API mechanism. We have chosen to use a GSS-API concrete GSS-API mechanism. We have chosen to use a GSS-API
mechanism that encapsulates EAP authentication. So, GSS-API (and mechanism that encapsulates EAP authentication. So, GSS-API (and
SASL) encapsulate EAP between the end-host and the service. The AAA SASL) encapsulate EAP between the end-host and the service. The AAA
framework encapsulates EAP between the relying party and the identity framework encapsulates EAP between the relying party and the identity
provider. The GSS-API mechanism includes rules about how initiators provider. The GSS-API mechanism includes rules about how initiators
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realm that provides the service does not need to be validated. realm that provides the service does not need to be validated.
In many cases applications may retrieve information about providers In many cases applications may retrieve information about providers
of services from DNS. When Service Records (SRV) and Naming of services from DNS. When Service Records (SRV) and Naming
Authority Pointer (NAPTR) records are used to help find a host that Authority Pointer (NAPTR) records are used to help find a host that
provides a service, the security requirements on the referrals is provides a service, the security requirements on the referrals is
going to interact with the information used in the service name. If going to interact with the information used in the service name. If
a host name is returned from the DNS referrals, and the host name is a host name is returned from the DNS referrals, and the host name is
to be validated by GS-EAP, then it makes sense that the referrals to be validated by GS-EAP, then it makes sense that the referrals
themselves should be secure. On the other hand, if the host name themselves should be secure. On the other hand, if the host name
returned is not validated, i.e. only the service is passed in, then returned is not validated, i.e. only the service is passed in, then
it is less important that the host name be obtained in a secure it is less important that the host name be obtained in a secure
manner. manner.
Another issue that needs to be addressed for host-based service names Another issue that needs to be addressed for host-based service names
is that they do not work ideally when different instances of a is that they do not work ideally when different instances of a
service are running on different ports. If the services are service are running on different ports. If the services are
equivalent, then it does not matter. However if there are equivalent, then it does not matter. However if there are
substantial differences in the quality of the service that substantial differences in the quality of the service that
information needs to be part of the validation process. If one has information needs to be part of the validation process. If one has
just a host name and not a port in the information being validated, just a host name and not a port in the information being validated,
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Initiator: Client. Initiator: Client.
Observers: Client, RP, AAA Client, AAA Proxy(s), AAA Server, IdP. Observers: Client, RP, AAA Client, AAA Proxy(s), AAA Server, IdP.
Recipient: IdP Recipient: IdP
In the IdP to Relying party (via the Federation Substrate) In the IdP to Relying party (via the Federation Substrate)
communication phase, we have: communication phase, we have:
Initiator: IdP. Initiator: RP.
Observers: IdP, AAA Server, AAA Proxy(s), AAA Client, RP. Observers: IdP, AAA Server, AAA Proxy(s), AAA Client, RP.
Recipient: RP Recipient: IdP
Eavesdroppers and Attackers can reside on any communication link Eavesdroppers and Attackers can reside on any communication link
between entities in Figure 3. between entities in Figure 3.
The Federation Substrate consists of all of the AAA entities. In The Federation Substrate consists of all of the AAA entities. In
some cases the AAA Proxies entities may not exist as the AAA Client some cases the AAA Proxies entities may not exist as the AAA Client
can talk directly to the AAA Server. Specifications such as the can talk directly to the AAA Server. Specifications such as the
Trust Router Protocol and RADIUS dynamic discovery Trust Router Protocol and RADIUS dynamic discovery
[I-D.ietf-radext-dynamic-discovery] can be used to shorten the path [I-D.ietf-radext-dynamic-discovery] can be used to shorten the path
between the AAA client and the AAA server (and thus stop these AAA between the AAA client and the AAA server (and thus stop these AAA
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4.2.1. Client to RP 4.2.1. Client to RP
The flow of data between the client and the RP is divided into two The flow of data between the client and the RP is divided into two
parts. The first part consists of all of the data exchanged as part parts. The first part consists of all of the data exchanged as part
of the ABFAB authentication process. The second part consists of all of the ABFAB authentication process. The second part consists of all
of the data exchanged after the authentication process has been of the data exchanged after the authentication process has been
finished. finished.
During the initial communications phase, the client sends an NAI (see During the initial communications phase, the client sends an NAI (see
[I-D.ietf-radext-nai]) to the RP. Many EAP methods (but not all) [I-D.ietf-radext-nai]) to the RP. Many EAP methods (but not all)
allow for the client to disclose an NAI to the in a form that allow for the client to disclose an NAI to RP the in a form that
includes only a realm during this communications phase. This is the includes only a realm component during this communications phase.
minimum amount of identity information necessary for ABFAB to work - This is the minimum amount of identity information necessary for
it indicates an IdP that the principal has a relationship with. EAP ABFAB to work - it indicates an IdP that the principal has a
methods that do not allow this will necessarily also reveal an relationship with. EAP methods that do not allow this will
identifier for the principal in the IdP realm (e.g. a username). necessarily also reveal an identifier for the principal in the IdP
realm (e.g. a username).
The data shared during the initial communication phase may be
protected by a channel protocol such as TLS. This will prevent the
leak of information to passive eavesdroppers, however an active
attacker may still be able to setup as a man-in-the-middle. The
client may not be able to validate the certificates (if any) provided
by the service, defering the check of the identity of the RP until
the completion of the ABFAB authentication protocol (i.e., using EAP
channel binding).
The data exchanged after the authentication process can have privacy The data exchanged after the authentication process can have privacy
and authentication using the GSS-API services. If the overall and authentication using the GSS-API services. If the overall
application protocol allows for the process of re-authentication, application protocol allows for the process of re-authentication,
then the same privacy impliciations as discussed in previous then the same privacy impliciations as discussed in previous
paragraph apply. paragraphs apply.
4.2.2. Client to IdP (via Federation Substrate) 4.2.2. Client to IdP (via Federation Substrate)
This phase sees a secure TLS tunnel initiated between the Client and This phase sees a secure TLS tunnel initiated between the Client and
the IdP via the RP and federation substrate. The process is the IdP via the RP and federation substrate. The process is
initiated by the RP using the realm information given to it by the initiated by the RP using the realm information given to it by the
client. Once set up, the tunnel is used to send credentials to IdP client. Once set up, the tunnel is used to send credentials to IdP
to authenticate. to authenticate.
Various operational information is transported between RP and IdP, Various operational information is transported between RP and IdP,
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o The Relying Party knows the IP address of the Client. It is o The Relying Party knows the IP address of the Client. It is
possible that the Relying Party could choose to expose this IP possible that the Relying Party could choose to expose this IP
address by including it in a RADIUS header such as Calling Station address by including it in a RADIUS header such as Calling Station
ID. This is a privacy consideration to take into account of the ID. This is a privacy consideration to take into account of the
application protocol. application protocol.
o The EAP MSK is transported between the IdP and the RP over the AAA o The EAP MSK is transported between the IdP and the RP over the AAA
infrastructure, for example through RADIUS headers. This is a infrastructure, for example through RADIUS headers. This is a
particularly important privacy consideration, as any AAA Proxy particularly important privacy consideration, as any AAA Proxy
that has access to the EAP MSK is able to decrypt and eavesdrop on that has access to the EAP MSK is able to decrypt and eavesdrop on
any traffic encrypted using that EAP MSK (i.e. all communications any traffic encrypted using that EAP MSK (i.e. all communications
between the Client and IdP). between the Client and IdP).
o Related to the above, the AAA server has access to the material o Related to the above, the AAA server has access to the material
necessary to derive the session key, thus the AAA server can necessary to derive the session key, thus the AAA server can
observe any traffic encrypted between the Client and RP. This observe any traffic encrypted between the Client and RP. This
"feature" was" chosen as a simplification and to make performance "feature" was" chosen as a simplification and to make performance
faster; if it was decided that this trade-off was not desireable faster; if it was decided that this trade-off was not desireable
for privacy and security reasons, then extensions to ABFAB that for privacy and security reasons, then extensions to ABFAB that
make use of techniques such as Diffie-Helman key exchange would make use of techniques such as Diffie-Helman key exchange would
mitigate against this. mitigate against this.
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4.5. Collection and retention of data and identifiers 4.5. Collection and retention of data and identifiers
In cases where Relying Parties do not require to identify a In cases where Relying Parties do not require to identify a
particular individual when an individual wishes to make use of their particular individual when an individual wishes to make use of their
service, the ABFAB architecture enable anonymous or pseudonymous service, the ABFAB architecture enable anonymous or pseudonymous
access. Thus data and identifiers other than pseudonyms and access. Thus data and identifiers other than pseudonyms and
unlinkable attribute information need not be stored and retained. unlinkable attribute information need not be stored and retained.
However, in cases where Relying Parties require the ability to However, in cases where Relying Parties require the ability to
identify a particular individual (e.g. so they can link this identify a particular individual (e.g. so they can link this identity
identity information to a particular account in their service, or information to a particular account in their service, or where
where identity information is required for audit purposes), the identity information is required for audit purposes), the service
service will need to collect and store such information, and to will need to collect and store such information, and to retain it for
retain it for as long as they require. Deprovisioning of such as long as they require. Deprovisioning of such accounts and
accounts and information is out of scope for ABFAB, but obviously for information is out of scope for ABFAB, but obviously for privacy
privacy protection any identifiers collected should be deleted when protection any identifiers collected should be deleted when they are
they are no longer needed. no longer needed.
4.6. User Participation 4.6. User Participation
In the ABFAB architecture, by its very nature users are active In the ABFAB architecture, by its very nature users are active
participants in the sharing of their identifiers as they initiate the participants in the sharing of their identifiers as they initiate the
communications exchange every time they wish to access a server. communications exchange every time they wish to access a server.
They are, however, not involved in control of the set of information They are, however, not involved in control of the set of information
related to them that transmitted from the IdP to RP for authorisation related to them that transmitted from the IdP to RP for authorisation
purposes; rather, this is under the control of policy on the IdP. purposes; rather, this is under the control of policy on the IdP.
Due to the nature of the AAA communication flows, with the current Due to the nature of the AAA communication flows, with the current
ABFAB architecture there is no place for a process of gaining user ABFAB architecture there is no place for a process of gaining user
consent for the information to be released from IdP to RP. consent for the information to be released from IdP to RP.
5. Deployment Considerations 5. Security Considerations
5.1. EAP Channel Binding
Discuss the implications of needing EAP channel binding.
5.2. AAA Proxy Behavior
Discuss deployment implications of our proxy requirements.
6. Security Considerations
This document describes the architecture for Application Bridging for This document describes the architecture for Application Bridging for
Federated Access Beyond Web (ABFAB) and security is therefore the Federated Access Beyond Web (ABFAB) and security is therefore the
main focus. This section highlights the main communication channels main focus. This section highlights the main communication channels
and their security properties: and their security properties:
Client-to-RP Channel: Client-to-RP Channel:
The channel binding material is provided by any certificates and The channel binding material is provided by any certificates and
the final message (i.e., a cryptographic token for the channel). the final message (i.e., a cryptographic token for the channel).
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communication to the client over the RP-to-IdP channel is the same communication to the client over the RP-to-IdP channel is the same
one talking to the IdP. This is accomplished via the EAP channel one talking to the IdP. This is accomplished via the EAP channel
binding. binding.
Partial list of issues to be addressed in this section: Privacy, Partial list of issues to be addressed in this section: Privacy,
SAML, Trust Anchors, EAP Algorithm Selection, Diameter/RADIUS/AAA SAML, Trust Anchors, EAP Algorithm Selection, Diameter/RADIUS/AAA
Issues, Naming of Entities, Protection of passwords, Channel Binding, Issues, Naming of Entities, Protection of passwords, Channel Binding,
End-point-connections (TLS), Proxy problems End-point-connections (TLS), Proxy problems
When a pseudonym is generated as a unique long term identifier for a When a pseudonym is generated as a unique long term identifier for a
Subject by an IdP, care MUST be taken in the algorithm that it cannot client by an IdP, care MUST be taken in the algorithm that it cannot
easily be reverse engineered by the service provider. If it can be easily be reverse engineered by the service provider. If it can be
reversed then the service provider can consult an oracle to determine reversed then the service provider can consult an oracle to determine
if a given unique long term identifier is associated with a different if a given unique long term identifier is associated with a different
known identifier. known identifier.
7. IANA Considerations 6. IANA Considerations
This document does not require actions by IANA. This document does not require actions by IANA.
8. Acknowledgments 7. Acknowledgments
We would like to thank Mayutan Arumaithurai, Klaas Wierenga and Rhys
We would like to thank Mayutan Arumaithurai and Klaas Wierenga for Smith for their feedback. Additionally, we would like to thank Eve
their feedback. Additionally, we would like to thank Eve Maler, Maler, Nicolas Williams, Bob Morgan, Scott Cantor, Jim Fenton, Paul
Nicolas Williams, Bob Morgan, Scott Cantor, Jim Fenton, Paul Leach, Leach, and Luke Howard for their feedback on the federation
and Luke Howard for their feedback on the federation terminology terminology question.
question.
Furthermore, we would like to thank Klaas Wierenga for his review of Furthermore, we would like to thank Klaas Wierenga for his review of
the pre-00 draft version. the pre-00 draft version.
9. References 8. References
9.1. Normative References 8.1. Normative References
[RFC2743] Linn, J., "Generic Security Service Application Program [RFC2743] Linn, J., "Generic Security Service Application Program
Interface Version 2, Update 1", RFC 2743, January 2000. Interface Version 2, Update 1", RFC 2743, January 2000.
[RFC2865] Rigney, C., Willens, S., Rubens, A., and W. Simpson, [RFC2865] Rigney, C., Willens, S., Rubens, A., and W. Simpson,
"Remote Authentication Dial In User Service (RADIUS)", RFC "Remote Authentication Dial In User Service (RADIUS)", RFC
2865, June 2000. 2865, June 2000.
[RFC3588] Calhoun, P., Loughney, J., Guttman, E., Zorn, G., and J. [RFC3588] Calhoun, P., Loughney, J., Guttman, E., Zorn, G., and J.
Arkko, "Diameter Base Protocol", RFC 3588, September 2003. Arkko, "Diameter Base Protocol", RFC 3588, September 2003.
skipping to change at page 41, line 17 skipping to change at page 41, line 11
progress), February 2013. progress), February 2013.
[I-D.ietf-radext-nai] [I-D.ietf-radext-nai]
DeKok, A., "The Network Access Identifier", draft-ietf- DeKok, A., "The Network Access Identifier", draft-ietf-
radext-nai-02 (work in progress), January 2013. radext-nai-02 (work in progress), January 2013.
[RFC6677] Hartman, S., Clancy, T., and K. Hoeper, "Channel-Binding [RFC6677] Hartman, S., Clancy, T., and K. Hoeper, "Channel-Binding
Support for Extensible Authentication Protocol (EAP) Support for Extensible Authentication Protocol (EAP)
Methods", RFC 6677, July 2012. Methods", RFC 6677, July 2012.
9.2. Informative References 8.2. Informative References
[RFC2903] de Laat, C., Gross, G., Gommans, L., Vollbrecht, J., and [RFC2903] de Laat, C., Gross, G., Gommans, L., Vollbrecht, J., and
D. Spence, "Generic AAA Architecture", RFC 2903, August D. Spence, "Generic AAA Architecture", RFC 2903, August
2000. 2000.
[I-D.nir-tls-eap] [I-D.nir-tls-eap]
Nir, Y., Sheffer, Y., Tschofenig, H., and P. Gutmann, "A Nir, Y., Sheffer, Y., Tschofenig, H., and P. Gutmann, "A
Flexible Authentication Framework for the Transport Layer Flexible Authentication Framework for the Transport Layer
Security (TLS) Protocol using the Extensible Security (TLS) Protocol using the Extensible
Authentication Protocol (EAP)", draft-nir-tls-eap-13 (work Authentication Protocol (EAP)", draft-nir-tls-eap-13 (work
skipping to change at page 42, line 18 skipping to change at page 42, line 13
1964, June 1996. 1964, June 1996.
[RFC2203] Eisler, M., Chiu, A., and L. Ling, "RPCSEC_GSS Protocol [RFC2203] Eisler, M., Chiu, A., and L. Ling, "RPCSEC_GSS Protocol
Specification", RFC 2203, September 1997. Specification", RFC 2203, September 1997.
[RFC3645] Kwan, S., Garg, P., Gilroy, J., Esibov, L., Westhead, J., [RFC3645] Kwan, S., Garg, P., Gilroy, J., Esibov, L., Westhead, J.,
and R. Hall, "Generic Security Service Algorithm for and R. Hall, "Generic Security Service Algorithm for
Secret Key Transaction Authentication for DNS (GSS-TSIG)", Secret Key Transaction Authentication for DNS (GSS-TSIG)",
RFC 3645, October 2003. RFC 3645, October 2003.
[RFC2138] Rigney, C., Rigney, C., Rubens, A.C., Simpson, W.A., and [RFC2138] Rigney, C., Rigney, C., Rubens, A., Simpson, W., and S.
S. Willens, "Remote Authentication Dial In User Service Willens, "Remote Authentication Dial In User Service
(RADIUS)", RFC 2138, April 1997. (RADIUS)", RFC 2138, April 1997.
[RFC4462] Hutzelman, J., Salowey, J., Galbraith, J., and V. Welch, [RFC4462] Hutzelman, J., Salowey, J., Galbraith, J., and V. Welch,
"Generic Security Service Application Program Interface "Generic Security Service Application Program Interface
(GSS-API) Authentication and Key Exchange for the Secure (GSS-API) Authentication and Key Exchange for the Secure
Shell (SSH) Protocol", RFC 4462, May 2006. Shell (SSH) Protocol", RFC 4462, May 2006.
[RFC4422] Melnikov, A. and K. Zeilenga, "Simple Authentication and [RFC4422] Melnikov, A. and K. Zeilenga, "Simple Authentication and
Security Layer (SASL)", RFC 4422, June 2006. Security Layer (SASL)", RFC 4422, June 2006.
 End of changes. 47 change blocks. 
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