One document matched: draft-ietf-abfab-arch-00.xml
<?xml version="1.0" encoding="US-ASCII"?>
<?xml-stylesheet type='text/xsl' href='rfc2629.xslt' ?>
<?rfc toc="yes" ?>
<?rfc symrefs="yes" ?>
<?rfc sortrefs="no"?>
<?rfc iprnotified="no" ?>
<?rfc strict="no" ?>
<?rfc compact="no" ?>
<?rfc subcompact="no" ?>
<!DOCTYPE rfc SYSTEM "rfc2629.dtd" [
<!ENTITY RFC1964 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.1964.xml">
<!ENTITY RFC2865 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.2865.xml">
<!ENTITY RFC2203 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.2203.xml">
<!ENTITY RFC3588 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.3588.xml">
<!ENTITY RFC3588 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.3588.xml">
<!ENTITY RFC2743 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.2743.xml">
<!ENTITY RFC3748 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.3748.xml">
<!ENTITY RFC4462 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.4462.xml">
<!ENTITY RFC4422 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.4422.xml">
<!ENTITY RFC4282 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.4282.xml">
<!ENTITY RFC5056 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.5056.xml">
<!ENTITY RFC3645 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.3645.xml">
<!ENTITY RFC4072 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.4072.xml">
<!ENTITY RFC5801 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.5801.xml">
<!ENTITY RFC5849 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.5849.xml">
<!ENTITY RFC2904 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.2904.xml">
<!ENTITY RFC3579 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.3579.xml">
<!ENTITY RFC4017 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.4017.xml">
<!ENTITY RFC5106 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.5106.xml">
<!ENTITY RFC2138 SYSTEM "http://xml.resource.org/public/rfc/bibxml/reference.RFC.2138.xml">
<!ENTITY I-D.nir-tls-eap SYSTEM "http://xml.resource.org/public/rfc/bibxml3/reference.I-D.nir-tls-eap.xml">
<!ENTITY I-D.ietf-oauth-v2 SYSTEM "http://xml.resource.org/public/rfc/bibxml3/reference.I-D.ietf-oauth-v2.xml">
<!ENTITY I-D.morris-privacy-considerations SYSTEM "http://xml.resource.org/public/rfc/bibxml3/reference.I-D.morris-privacy-considerations.xml">
<!ENTITY I-D.ietf-abfab-gss-eap SYSTEM "http://xml.resource.org/public/rfc/bibxml3/reference.I-D.ietf-abfab-gss-eap.xml">
<!ENTITY I-D.hansen-privacy-terminology SYSTEM "http://xml.resource.org/public/rfc/bibxml3/reference.I-D.hansen-privacy-terminology.xml">
<!ENTITY SAML20 SYSTEM "http://xml.resource.org/public/rfc/bibxml2/reference.OASIS.saml-core-2.0-os.xml">
]>
<rfc category="info" docName="draft-ietf-abfab-arch-00.txt" ipr="trust200902">
<front>
<title abbrev="ABFAB Architecture">Application Bridging for Federated Access Beyond Web (ABFAB) Architecture</title>
<author initials="J." surname="Howlett" fullname="Josh Howlett">
<organization>JANET(UK)</organization>
<address>
<postal>
<street>Lumen House, Library Avenue, Harwell</street>
<city>Oxford</city>
<code>OX11 0SG</code>
<country>UK</country>
</postal>
<phone>+44 1235 822363</phone>
<email>Josh.Howlett@ja.net</email>
</address>
</author>
<author initials="S." surname="Hartman" fullname="Sam Hartman">
<organization>Painless Security</organization>
<address>
<postal>
<street> </street>
<city> </city>
<code> </code>
<country> </country>
</postal>
<phone> </phone>
<email>hartmans-ietf@mit.edu</email>
</address>
</author>
<author initials="H." surname="Tschofenig" fullname="Hannes Tschofenig">
<organization>Nokia Siemens Networks</organization>
<address>
<postal>
<street>Linnoitustie 6</street>
<city>Espoo</city>
<code>02600</code>
<country>Finland</country>
</postal>
<phone>+358 (50) 4871445</phone>
<email>Hannes.Tschofenig@gmx.net</email>
<uri>http://www.tschofenig.priv.at</uri>
</address>
</author>
<author fullname="Eliot Lear" initials="E." surname="Lear">
<organization>Cisco Systems GmbH</organization>
<address>
<postal>
<street>Richtistrasse 7</street>
<city>Wallisellen</city>
<code>CH-8304</code>
<region>ZH</region>
<country>Switzerland</country>
</postal>
<phone>+41 44 878 9200</phone>
<email>lear@cisco.com</email>
</address>
</author>
<date year="2011"/>
<area>Internet</area>
<workgroup>ABFAB</workgroup>
<keyword>Internet-Draft</keyword>
<keyword>Federated Authentication</keyword>
<keyword>AAA</keyword>
<keyword>RADIUS</keyword>
<keyword>Diameter</keyword>
<keyword>GSS-API</keyword>
<keyword>EAP</keyword>
<keyword>SASL</keyword>
<abstract>
<t>
Over the last decade a substantial amount of work has occurred in
the space of federated access management. Most of
this effort has focused on two use-cases: network and
web-based access. However, the solutions to these use-cases that
have been proposed and deployed tend to have few common building blocks in common.
</t>
<t>
This memo describes an architecture that makes use of
extensions to the commonly used security mechanisms for both federated and
non-federated access management, including
RADIUS, Diameter, GSS, GS2, EAP and SAML. The architecture addresses
the problem of federated access management to primarily non-web-based
services, in a manner that will scale to large numbers of identity providers, relying parties, and
federations.
</t>
</abstract>
</front>
<middle>
<!-- ////////////////////////////////////////////////////////////////////////////////// -->
<section anchor="introduction" title="Introduction">
<t>
The Internet uses numerous security mechanisms to manage
access to various resources. These mechanisms have been generalized
and scaled over the last decade through mechanisms such as
<xref target="RFC5801">SASL/GS2</xref>, <xref target="OASIS.saml-core-2.0-os">Security Assertion Markup Language (SAML)</xref>,
RADIUS <xref target="RFC2865"/>, and Diameter <xref target="RFC3588"/>.
</t>
<t>
A Relying Party (RP) is the entity that manages access to some
resource. The actor that is requesting access to that resource
is often described as the Subject. Many security
mechanisms are manifested as an exchange of information between
these actors. The RP is therefore able to decide whether
the Subject is authorised, or not.
</t>
<t>
Some security mechanisms allow the RP to delegate aspects
of the access management decision to an actor called the
Identity Provider (IdP).
This delegation requires technical signalling, trust and a common understanding of
semantics between the RP and IdP. These aspects are generally managed within a
relationship known as a 'federation'. This style of access management is accordingly
described as 'federated access management'.
</t>
<t>
Federated access management has evolved over
the last decade through such standards as SAML <xref target="OASIS.saml-core-2.0-os"/>,
<eref target="http://www.openid.net">OpenID</eref>, and OAuth <xref target="RFC5849"/>, <xref target="I-D.ietf-oauth-v2"/>. The benefits of federated access management include:
<list style="hanging">
<t hangText="Single or Simplified sign-on:">
<vspace blankLines="1"/> An Internet service can delegate access management,
and the associated responsibilities such as identity management and credentialing,
to an organisation that already has a long-term relationship with the Subject.
This is often attractive for Relying Parties who frequently do not want these responsibilities.
The Subject may also therefore require fewer credentials, which is often desirable.
</t>
<t hangText="Privacy:"><vspace blankLines="1"/>
Often a Relying Party does not need to know the identity of a Subject to
reach an access management decision. It is frequently only necessary for the
Relying Party to establish, for example, that the Subject is affiliated with
a particular organisation or has a certain role or entitlement. Sometimes the
RP does require an identifier for the Subject (for example, so that it can recognise
the Subject subsequently); in this case, it is common practise for the IdP to only
release a pseudonym that is specific to that particular Relying Party.
Federated access management therefore provides various strategies for protecting
the Subject's privacy. Other privacy aspects typically of concern are the policy for releasing
personal data about the Subjectfrom the IdP to the RP, the purpose of the usage, the retention period
of the data, and many more.
</t>
<t hangText="Provisioning"><vspace blankLines="1"/>
Sometimes a Relying Party needs, or would like, to know more about
a subject that an affiliation or pseudonym. For example, a Relying Party may want
the Subject's email address or name. Some federated access management technologies
provide the ability for the IdP to provision this information, either on request by
by the RP or unsolicited.
</t>
</list>
</t>
<!-- ////////////////////////////////////////////////////////////////////////////////// -->
<section anchor="terminology" title="Terminology">
<t>This document uses identity management and privacy
terminology from
<xref target="I-D.hansen-privacy-terminology"/>.
In particular, this document uses the terms pseudonymity, unlinkability, anonymity, and identity management.</t>
<t>We make one note about the IdP: in this architecture, the IdP
consists of the following components: an EAP server, a radius
server, and optionally a SAML Assertion service. The IdP is
also responsible for authentication, even though it may rely
upon other components within a domain for such an operation.
The reader is advised that for succinctness, in most cases the
term IdP is used, except where additional clarity seems
appropriate.
</t>
</section>
<section title="An Overview of Federation">
<t>
In the previous section we introduced the following actors:
</t>
<t>
<list style="symbols">
<t>the Subject,</t>
<t>the Identity Provider, and </t>
<t>the Relying Party.</t>
</list>
</t>
<t>
These entities and their relationships are illustrated graphically in <xref
target="framework"/>.
</t>
<t>
<figure title="General federation framework model" anchor="framework">
<artwork><![CDATA[
,----------\ ,---------\
| Identity | Federation | Relying |
| Provider + <-------------------> + Party |
`----------' '---------'
<
\
\ Identity
\ management
\
\
\
\ +------------+
\ | |
v| Subject |
| |
+------------+
]]></artwork>
</figure>
</t>
<t>
A federation typically this relationship encompasses
operational specifications and legal rules:
</t>
<t>
<list style="hanging">
<t hangText="Operational Specifications:"> <vspace blankLines="1"/>
This includes the technical specifications (e.g. protocols used to communicate between the three parties),
process standards, policies, identity proofing, credential and authentication algorithm requirements, performance requirements, assessment and audit criteria, etc. The goal of these specifications to make the system work and to accomplish interoperability.</t>
<t hangText="Legal Rules:"> <vspace blankLines="1"/>
The legal rules take existing laws into consideration and provide contractual obligations to provide further clarification and define responsibilities. These legal rules regulate the operational specifications, make operational specifications legally binding to the participants, define and govern the rights and responsibilities of the participants.
These legal rules may, for example, describe liability for losses, termination rights, enforcement mechanisms, measures of damage, dispute resolution, warranties, etc.</t>
</list>
</t>
<t>
The nature of federation dictates that there is some
form of relationship between the identity provider and the relying party.
This is particularly important when the relying party wants to use
information obtained from the identity provider for access management
decisions and when the identity provider does not want to release
information to every relying party (or only under certain conditions).
</t>
<t>
While it is possible to have a bilateral agreement between every
IdP and every RP; on an Internet scale this setup requires the introduction of the
multi-lateral federation concept, as the management of such pair-wise
relationships would otherwise prove burdensome.
</t>
<t>
While many of the non-technical aspects of federation, such as business practices and legal arrangements, are outside the
scope of the IETF they still impact the architectural setup on how to ensure the dynamic establishment of trust.
</t>
<t>
Some deployments are sometimes required to deploy complex technical
infrastructure, including message routing intermediaries, to offer the
required technical functionality, while in other deployments those are missing.
</t>
<t>
<xref target="framework"/> also shows the relationship between
the IdP and the Subject. Often a real world entity is associated with the Subject; for example, a person
or some software.
</t>
<t>
The IdP will typically have a long-term relationship with the Subject. This relationship
would typically involve the IdP positively identifying and credentialling the Subject
(for example, at time of enrollment in the context of employment within an organisation).
The relationship will often be instantiated within an agreement between the IdP and the
Subject (for example, within an employment contract or terms of use that stipulates the
appropriate use of credentials and so forth).
</t>
<t>
While federation is often discussed within the context of relatively formal relationships,
such as between an enterprise and an employee or a government and a citizen, federation does
not in any way require this; nor, indeed, does it require any particular level of formality.
It is, for example, entirely compatible with a relationship between the IdP and Subject
that is only as weak as completing a web form and confirming the verification email.
</t>
<t>
However, the nature and quality of the relationship between the Subject and the IdP is
an important contributor to the level of trust that an RP may attribute to an
assertion describing a Subject made by an IdP. This is sometimes described
as the Level of Assurance.
</t>
<t>
Similarly it is also important to note that, in the general case, there
is no requirement of a long-term relationship betweem the RP and the Subject. This is a property
of federation that yields many of its benefits. However, federation does not
preclude the possibility relationship between the RP and the Subject,
should needs dictate.
</t>
<t>
Finally, it is important to reiterate that in some
scenarios there might indeed be a human behind the device denoted as Subject and in other
cases there is no human involved in the actual protocol execution.
</t>
</section>
<section title="Challenges to Contemporary Federation">
<!-- <t>
JH: Much more content needed!
</t>
--> <t>
As the number of such federated services has proliferated, however,
the role of the individual has become ambiguous in certain
circumstances. For example, a school might provide online access to
grades to a parent who is also a teacher. She must
clearly distinguish her role upon access. After all, she is
probably not allowed to edit her own child's grades.
</t>
<t>
Similarly, as the number of federations proliferates, it becomes
increasingly difficult to discover which identity provider a user is
associated with. This is true for both the web and non-web case,
but particularly acute for the latter ans many non-web
authentication systems are not semantically rich enough on their own
to allow for such ambiguities. For instance, in the case of an
email provider, the use of SMTP and IMAP protocols does not on its
own provide for a way to select a federation. However, the building
blocks do exist to add this functionality.
</t>
</section>
<section title="An Overview of ABFAB-based Federation">
<t>
The previous section described the general model of federation,
and its the application of federated access management. This section provides
a brief overview of ABFAB in the context of this model.
</t>
<t>
The steps taken generally in an ABFAB federated authentication/authorization
exchange are as follows:
</t>
<t>
<list style="numbers">
<t>Principal provides NAI to Application: Somehow the client is
configured with at least the realm portion of
an NAI, which represents the IdP to be discovered.</t>
<t>
Authentication mechanism selection: this is the step necessary to
indicate that the GSS-EAP SASL/GS2 mechanism will be used for
authentication/authorization.
</t>
<t>
Client Application provides NAI to RP: At the conclusion of mechanism
selection the NAI must be provided to the RP for discovery.
</t>
<t>
Discovery of federated IdP:
This is discussed in detail below. Either the RP is configured with
authorized IdPs, or it makes use of a federation proxy.
</t>
<t>
Request from Relying Party to IdP: Once the RP knows who the IdP is,
it or its agent will forward RADIUS
request that encapsulates a GSS/EAP access request to an IdP. This
may or may not contain a SAML request as a series of attributes.. At
this stage, the RP will likely have no idea who the principal is.
The RP claims its identity to the IdP in AAA attributes, and
it makes whatever SAML Attribute Requests through a
AAA attribute. XXX- Check order of SAML attribute request.
</t>
<t>
IdP informs the principal of which EAP method to use: The available
and appropriate methods are discussed below in this memo.
</t>
<t>
A bunch of EAP messages happen between the endpoints: Messages are
exchanged between the principal and the IdP until a
result is determined. The number and content of those messages will
depend on the EAP method. If the IdP is unable to authenticate the
principal, the process concludes here. As part of this process, the
principal will, under protection of EAP, assert the identity of the
RP to which it intends to authenticate.
</t>
<t>
Successful Authentication: At the very least the IdP (its
EAP server) and EAP peer / subject have authenticated one another.
As a result
of this step, the subject and the IdP hold two cryptographic
keys- a Master Session Key (MSK), and an Extended MSK (EMSK). If the
asserted identity of the RP by the principal matches the identity the
RP itself asserted, there is some confidence that the RP is now
authenticated to the IdP.
</t>
<t>
Local IdP Policy Check: At this stage, the IdP checks local policy to
determine whether the RP and subject are authorized
for a given transaction/service, and if so, what if any,
attributes will be released to the RP. Additional
policy checks will likely have been made earlier just through the
process of discovery.
</t>
<t>
Response from the IdP to the Relying Party: Once the IdP has made a
determination of whether and how to
authenticate or authorize the principal to the RP, it
returns either a negative AAA result to the RP, or it
returns a positive result to the RP, along with an optional
set of AAA attributes associated with the principal that
could include one or more SAML assertions. In addition, an
EAP MSK is returned to the subject.
</t>
<t>RP Processes Results. When the RP receives the result
from the IdP, it should have enough information to either
grant or refuse a resource access request. It may have
information that leads it to make additional attribute
queries. It may have information that associates the
principal with specific authorization identies. It will
apply these results in an application-specific way.</t>
<t>
RP returns results to principal: Once the RP has a response it must inform
the client application of
the result. If all has gone well, all are authenticated, and the
application proceeds with appropriate authorization levels.
</t>
</list>
</t>
<t>
An example communication flow is given below:
</t>
<t>
<figure>
<artwork><![CDATA[
Relying Party Client App IdP
| (1) | Client App gets NAI (somehow)
| | |
|<-----(2)----->| | Mechanism Selection
| | |
|<-----(3)-----<| | NAI transmitted to RP
| | |
|<=====(4)====================>| Discovery
| | |
|>=====(5)====================>| Access request from RP to IdP
| | |
| |< - - (6) - -<| EAP method to Principal
| | |
| |< - - (7) - ->| EAP Exchange to authenticate
| | | Principal
| | |
| | (8 & 9) Local Policy Check
| | |
|<====(10)====================<| IdP Assertion to RP
| | |
| | | (11) RP Processes results.
| | |
|>----(12)----->| | Results to client app.
----- = Between Client App and RP
===== = Between RP and IdP
- - - = Between Client App and IdP
]]>
</artwork>
</figure>
</t>
</section>
<section title="Design Goals">
<t>Our key design goals are as follows:</t>
<t>
<list style="symbols">
<t>Each party of a transaction will be authenticated, and the
principal will be authorized for access to a specific resource .</t>
<t>Means of authentication is decoupled so as to allow for multiple
authentication methods.</t>
<t>Hence, the architecture requires no sharing of long term private
keys.</t>
<t>The system will scale to large numbers of identity providers,
relying parties, and users.</t>
<t>The system will be designed primarily for non-Web-based
authentication.</t>
<t>The system will build upon existing standards, components, and
operational practices.
</t>
</list>
</t>
<t>Designing new three party authentication and authorization
protocols is hard and frought with risk of cryptographic
flaws. Achieving widespead deployment is even more
difficult. A lot of attention on federated access has been devoted to the Web. This document instead
focuses on a non-Web-based environment and focuses on those protocols where HTTP is not
used. Despite the increased excitement for layering every protocol on top of HTTP there are
still a number of protocols available that do not use HTTP-based transports. Many of these
protocols are lacking a native authentication and authorization framework of the style shown in
<xref target="framework"/>.</t>
</section>
<section title="Use of AAA">
<t>Interestingly, for network access authentication the usage of the AAA framework with RADIUS
<xref target="RFC2865"/> and Diameter <xref target="RFC3588"/> was quite successful from a
deployment point of view. To map the terminology used in <xref target="framework"/> to the
AAA framework the IdP corresponds to the AAA server, the RP
corresponds to the AAA client, and the technical building blocks of a federation are AAA proxies, relays
and redirect agents
(particularly if they are operated by third parties, 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 authentication offered by link layer protocols that forward authentication protocol
exchanges back-and-forth. An example of a large scale
RADIUS-based federation
is <eref target="http://www.eduroam.org">EDUROAM</eref>.</t>
<t>Is it possible to design a system that builds on top of successful protocols to offer
non-Web-based protocols with a solid starting point for authentication and authorization in
a distributed system? </t>
</section>
<!-- ////////////////////////////////////////////////////////////////////////////////// -->
</section>
<section title="Architecture">
<t><xref target="introduction"/> already introduced the federated access architecture, with the illustration
of the different actors that need to interact, but it did not expand on the specifics of providing support for non-Web based applications. This section details this aspect and motivates
design decisions. The main theme of the work described in this document is focused on re-using existing building blocks that have been deployed already and to re-arrange them in a novel way.</t>
<t>
Although this architecture assumes updates to both the relying party as well as to the end host for application integration, those changes
are kept at a minimum. A mechanism that can
demonstrate deployment benefits (based on ease of update of existing
software, low implementation effort, etc.)is preferred and there may be a need
to specify multiple mechanisms to support the range of different
deployment scenarios.
</t>
<t>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 application protocols the usage of the GSS-API was chosen. Encapsulating EAP into the GSS-API also allows EAP to be used in SASL. A description of the technical specification can be found in <xref target="I-D.ietf-abfab-gss-eap"/>. Other alternatives exist as well and may be considered later, such as "TLS using EAP Authentication" <xref target="I-D.nir-tls-eap"/>.</t>
<t>There are several architectural layers in the system; this section discusses the individual layers.</t>
<section title="Federation Substrate">
<t>The federation substrate is responsible for the connunication between the relying party and the identity provider. This layer is responsible for the inter-domain communication and for the technical mechanisms necessary to establish inter-domain trust.</t>
<t>A key design goal is the re-use of an existing infrastructure,
we build upon the AAA framework as utilized by RADIUS
<xref target="RFC2138"/> and Diameter
<xref target="RFC3588"/>. Since this document does not aim to
re-describe the AAA framework the interested reader is referred
to <xref target="RFC2904"/>. Building on the AAA infrastructure,
and RADIUS and Diameter as protocols, modifications to that
infrastructure is to be avoided. Also, modifications to AAA
servers should be kept at a minimum.</t>
<t>The astute reader will notice that RADIUS and Diameter have
substantially similar characteristics. Why not pick one? A key
difference is that today RADIUS is largely transported upon UDP, and
its use is largely, though not exclusively, intra-domain. Diameter
itself was designed to scale to broader uses. We leave as a
deployment decision, which protocol will be appropriate.
</t>
<t>Through the integrity protection mechanisms in the AAA framework, the relying party can establish technical trust that messages are being sent by the appropriate relying party. Any given interaction will be associated with one federation at the policy level. The legal or business relationship defines what statements the identity provider is trusted to make and how these statements are interpreted by the relying party. The AAA framework also permits the relying party or elements between the relying party and identity provider to make statements about the relying party. </t>
<t>The AAA framework provides transport for attributes. Statements made about the subject by the identity provider, statements made about the relying party and other information is transported as attributes.</t>
<section title="Discovery, Rules Determination, and Technical Trust">
<t>One demand that the AAA substrate must make of the upper
layers is that they must properly identify the end points of the
communication. That is- it must be possible for the AAA
client at
the RP to determine where to send each RADIUS or Diameter message.
Without this requirement, it would be the RP's responsibility to determine the identity
of the principal on its own, without the assistance of an IdP. This
architecture makes use of the Network Access Identifier (NAI), where
the IdP is indicated in the realm component <xref target="RFC4282"
/>. The NAI is represented and consumed by the GSS-API
layer as GSS_C_NT_USER_NAME as specified in <xref target="RFC2743"
/>. The GSS-API EAp mechanism includes the NAI in the EAP Response/Identity message.
</t>
<t>The RP needs to discover which federation will be used to
contact the IDP. As part of this process, the RP determines
the set of business rules and technical policies governing
the relationship; this is called rules determination. The RP
also needs to establish technical trust in the
communications with the IDP.</t>
<t>Rules determination covers a broad range of decisions
about the exchange. One of these is whether the given RP is
permitted to talk to the IDP using a given federation at
all, so rules determination encompasses the basic
authorization decision. Other factors are included, such as
what policies govern release of information about the
principal to the RP and what policies govern the RP's use of
this information. While rules determination is ultimately a
business function, it has significant impact on the
technical exchanges. The protocols need to communicate the
result of authorization. When multiple sets of rules are
possible, the protocol must disambiguate which set of rules
are in play. Some rules have technical enforcement
mechanisms; for example in some federations intermediates
validate information that is being communicated within the federation.</t>
<t>Several deployment approaches are possible. These can
most easily be classified based on the mechanism for
technical trust that is used. The choice of technical trust
mechanism constrains how rules determination is
implemented. Regardless of what deployment strategy is
chosen, it is important that the technical trust mechanism
constrain the names of both parties to the exchange. The
trust mechanism ought to ensure that the entity acting as
IDP for a given NAI is permitted to be the IDP for that
realm, and that any service name claimed by the RP is
permitted to be claimed by that entity. Here are the categories of technical trust
determination:<list style="hanging">
<t hangText="AAA Proxy:">The simplest model is that an
RP supports a request directly to an AAA proxy. The
hop-by-hop integrity protection of the AAA fabric provides
technical trust. An RP can submit a request directly to a
federation. Alternatively, a federation disambiguation
fabric can be used. Such a fabric takes information about
what federations the RP is part of and what federations the
IDP is part of and routes a message to the appropriate
federation. The routing of messages across the fabric plus
attributes added to requests and responses provides rules
determination. For example, when a disambiguation fabric
routes a message to a given federation, that federation's
rules are chosen. Naming is enforced as messages travel
across the fabric. The entities near the RP confirm its
identity and validate names it claims. The fabric routes the
message towards the appropriate IDP, validating the IDP's
name in the process. The routing can be statically
configured. Alternatively a routing protocol could be
developed to exchange reachability information about given
IDPs and to apply policy across the AAA fabric. Such a
routing protocol could flood naming constraints to the
appropriate points in the fabric.</t>
<t hangText="Trust Broker:">Instead of routing messages
through AAA proxies, some trust broker could establish keys
between entities near the RP and entities near the IDP. The
advantage of this approach is efficiency of message
handling. Fewer entities are needed to be involved for each
message. Security may be improved by sending individual
messages over fewer hops. Rules determination involves
decisions made by trust brokers about what keys to
grant. Also, associated with each credential is context
about rules and about other aspects of technical trust
including names that may be claimed. A routing protocol
similar to the one for AAA proxies is likely to be useful to
trust brokers in flooding rules and naming constraints.</t>
<t hangText="Global Credential:">A global credential
such as a public key and certificate in a public key
infrastructure can be used to establish technical trust. A
directory or distributed database such as the Domain Name
System is needed for an RP to discover what endpoint to
contact for a given NAI. Certificates provide a place to
store information about rules determination and naming
constraints. Provided that no intermediates are required and
that the RP and IDP are sufficient to enforce and determine
rules, rules determination is reasonably simple. However
applying certain rules is likely to be quite complex. For
example if multiple sets of rules are possible between an
IDP and RP, confirming the correct set is used may be
difficult. This is particularly true if intermediates are
involved in making the decision. Also, to the extent that
directory information needs to be trusted, rules
determination may be more complex.</t>
</list>
</t>
<t>Real-world deployments are likely to be mixtures of these
basic approaches. For example, it will be quite common for
an RP to route traffic to a AAA proxy within an
organization. That proxy MAY use any of the three methods to
get closer to the IDP. It is also likely that rather than
being directly reachable, an IDP may have a proxy within its
organization. Federations MAY provide a traditional AAA
proxy interface even if they also provide another mechanism
for increased efficiency or security.</t>
</section>
</section>
<section title="Subject To Identity Provider">
<t>Traditional web federation does not describe how a subject
communicates with an identity provider. As a result, this
communication is not standardized. There are several
disadvantages to this approach. It is difficult to have
subjects that are machines rather than humans that use some
sort of programatic credential. In addition, use of browsers
for authentication restricts the deployment of more secure
forms of authentication beyond plaintext username and password
known by the server. In a number of cases the authentication
interface may be presented before the subject has adequately
validated they are talking to the intended server. By giving
control of the authentication interface to a potential
attacker, then the security of the system may be reduced and
phishing opportunities introduced.</t>
<t>As a result, it is desirable to choose some standardized
approach for communication between the subject's end-host and
the identity provider. There are a number of requirements this
approach must meet.</t>
<t>Experience has taught us one key security and scalability requirement:
it is important that the relying party not get in possession of the
long-term secret of the entity being authenticated by the AAA
server. Aside from a valuable secret being exposed, a
synchronization problem can also often develop.
Since there is
no single authentication mechanism that will be used everywhere there is another associated
requirement: The authentication framework must allow for the flexible integration of
authentication mechanisms. For instance, some identity
providers may require hardware tokens while others may use
passwords. A service provider would want to support both
sorts of federations, and others.</t>
<t>Fortunately, these requirements can be met by utilizing standardized and successfully deployed technology, namely by the Extensible Authentication
Protocol (EAP) framework
<xref target="RFC3748"/>.
<xref
target="abfab-arch"/> illustrates the integration graphically.</t>
<t> EAP is an end-to-end framework; it provides for two-way
communication between a peer (i.e,service client or
principal) through the
authenticator (i.e., service provider) to the back-end (i.e.,
identity provider). Conveniently, this is precisely the
communication path that is needed for federated identity.
Although EAP support is already integrated in AAA systems (see
<xref target="RFC3579"/> and <xref target="RFC4072"/>)
several challenges remain: one is to carry EAP payloads
from the end host to the relying party. Another is to
verify statements the relying party has made to the
subject, confirm these statements are consistent with
statements made to the identity provider and confirm all
the above are consistent with the federation and any
federation-specific policy or configuration. Another
challenge is choosing which identity provider to use for
which service.</t>
</section>
<section title="Application to Service">
<t>One of the remaining layers is responsible for integration
of federated authentication into the application. There are a
number of approaches that applications have adopted for
security. So, there may need to be multiple strategies for
integration of federated authentication into
applications. However, we have started with a strategy that
provides integration to a large number of application
protocols.</t>
<t>Many applications such as SSH <xref target="RFC4462"/>, NFS
<xref target="RFC2203"/>, DNS <xref target="RFC3645"/> and
several non-IETF applications support the Generic Security
Services Application Programming Interface <xref
target="RFC2743"/>. Many applications such as IMAP, SMTP, XMPP
and LDAP support e Simple Authentication and Security Layer
(SASL) <xref target="RFC4422"/> framework. These two
approaches work together nicely: by creating a GSS-API
mechanism, SASL integration is also addressed. In effect,
using a GSS-API mechanism with
SASL simply requires placing some headers on the front of the
mechanism and constraining certain GSS-API options.</t>
<t>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 people are first introduced to GSS-API, they
focus on it as an API. However, from the prospective of
authentication for non-web applications, GSS-API should be
thought of as a protocol not an API. It consists of some
abstract operations such as the initial context exchange,
which includes two sub-operations (gss_init_sec_context and
gss_accept_sec_context). An application defines which abstract
operations it is going to use and where messages produced by
these operations fit into the application architecture. A
GSS-API mechanism will define what actual protocol messages
result from that abstract message for a given abstract
operation. So, since this work is focusing on a particular
GSS-API mechanism, we generally focus on protocol elements
rather than the API view of GSS-API.</t>
<t>The API view has significant value. Since the abstract
operations are well defined, the set of information that a
mechanism gets from the application is well defined. Also, the
set of assumptions the application is permitted to make is
generally well defined. As a result, an application protocol
that supports GSS-API or SASL is very likely to be usable with
a new approach to authentication including this one with no
required modifications. In some cases, support for a new
authentication mechanism has been added using plugin
interfaces to applications without the application being
modified at all. Even when modifications are required, they
can often be limited to supporting a new naming and
authorization model. For example, this work focuses on
privacy; an application that assumes it will always obtain an
identifier for the principal will need to be modified to
support anonymity, unlinkability or pseudonymity.</t>
<t>So, we use GSS-API and SASL because a number of the
application protocols we wish to federate support these
strategies for security integration. What does this mean from
a protocol standpoint and how 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 mechanism that
encapsulates EAP authentication. So, GSS-API (and SASL)
encapsulate EAP between the end-host and the service. The AAA
framework encapsulates EAP between the relying party and the
identity provider. The GSS-API mechanism includes rules about
how principals and services are named as well as per-message
security and other facilities required by the applications we
wish to support.</t>
</section>
<section title="Personalization Layer">
<t>The AAA framework provides a way to transport statements
from the identity provider to the relying party. However, we
also need to say more about the content of these
statements. In simple cases, attributes particular to the AAA
protocol can be defined. However in more complicated
situations it is strongly desirable to re-use an existing
protocol for asking questions and receiving information about
subjects. SAML is used for this. </t>
<t>SAML usage may be as simple as the identity provider
including a SAML Response message in the AAA
response. Alternatively the relying party may generate a SAML
request XXX to whom, how, and at what point? (see above XXX).</t>
</section>
<section title="Tieing Layers Together">
<t>
<figure title="Architecture for Federated Access of non-Web based Applications" anchor="abfab-arch">
<artwork><![CDATA[
+--------------+
| AAA Server |
| (Identity |
| Provider) |
+-^----------^-+
* EAP | RADIUS/
* | Diameter
--v----------v--
/// \\\
// \\ ***
| Federation | back-
| | end
\\ // ***
\\\ ///
--^----------^--
* EAP | RADIUS/
Application * | Diameter
+-------------+ Data +-v----------v--+
| |<---------------->| |
| Client | EAP/EAP Method | Server Side |
| Application |<****************>| Application |
| @ End Host | GSS-API |(Relying Party)|
| |<---------------->| |
| | Application | |
| | Protocol | |
| |<================>| |
+-------------+ +---------------+
*** front-end ***
Legend:
<****>: End-to-end exchange
<---->: Hop-by-hop exchange
<====>: Protocol through which GSS-API/GS2 exchanges are tunnelled
]]></artwork>
</figure>
</t>
</section>
</section>
<!-- ////////////////////////////////////////////////////////////////////////////////// -->
<section title="Application Security Services">
<t>One of the key goals is to integrate federated authentication
into existing application protocols and where possible, existing
implementations of these protocols. Another goal is to perform
this integration while meeting the best security practices of
the technologies used to perform the integration. This section
describes security services and properties required by the EAP
GSS-API mechanism in order to meet these goals. This information
could be viewed as specific to that mechanism. However, other
future application integration strategies are very likely to
need similar services. So, it is likely that these services will
be expanded across application integration strategies if new
application integration strategies are adopted.</t>
<section title="Server (Mutual) Authentication">
<t>GSS-API provides an optional security service called mutual
authentication. This service means that in addition to the
initiator providing (potentially anonymous or pseudonymous)
identity to the acceptor, the acceptor confirms its identity
to the initiator. Especially for the ABFAB context, this
service is confusingly named. We still say that mutual
authentication is provided when the identity of an acceptor is
strongly authenticated to an anonymous initiator.</t>
<t>RFC 2743 does not explicitly talk about what mutual
authentication means. Within the GSS-API community successful mutual
authentication has come to mean:<list style="symbols">
<t>If a target name is supplied by the initiator, then the
initiator trusts that the supplied target name describes the
acceptor. This implies both that appropriate cryptographic
exchanges took place for the initiator to make such a trust
decision, and that after evaluating the results of these
exchanges, the initiator's policy trusts that the target name
is accurate.</t>
<t>The initiator trusts that its idea of the acceptor name
correctly names the entity it is communicating with.</t>
<t>Both the initiator and acceptor have the same key
material for per-message keys and both parties have confirmed
they actually have the key material. In EAP terms, there is a
protected indication of success.</t>
</list></t>
<t>Mutual authentication is an important defense against
certain aspects of phishing. Intuitively, users would like to
assume that if some party asks for their credentials as part
of authentication, successfully gaining access to the resource
means that they are talking to the expected party. Without
mutual authentication, the acceptor could "grant access"
regardless of what credentials are supplied. Mutual
authentication better matches this user intuition.</t>
<t>It is important, therefore, that the GSS-EAP mechanism implement mutual
authentication. That is, an initiator needs to be able to
request mutual authentication. When mutual authentication is
requested, only EAP methods capabale of providing the
necessary service can be used, and appropriate steps need to
be taken to provide mutual authentication. A broader set of
EAP methods could be supported when a particular application
does not request mutual authentication. It is an open question
whether the mechanism will permit this.</t>
</section>
<section title="GSS-API Channel Binding">
<t><xref target="RFC5056"/> defines a concept of channel
binding to prevent man-in-the-middle attacks. It is common to
provide SASL and GSS-API with another layer to provide
transport security; Transport Layer Security (TLS) is the most
common such layer. TLS provides its own server
authentication. However there are a variety of situations
where this authentication is not checked for policy or
usability reasons. Even when it is checked, if the trust
infrastructure behind the TLS authentication is different from
the trust infrastructure behind the GSS-API mutual
authentication. If the endpoints of the GSS-API authentication
are different than the endpoints of the lower layer, this is a
strong indication of a problem such as a man-in-the-middle
attack. Channel binding provides a facility to determine
whether these endpoints are the same.</t>
<t>The GSS-EAP mechanism needs to support channel
binding. When an application provides channel binding data,
the mechanism needs to confirm this is the same on both sides
consistent with the GSS-API specification. XXXThere is an open
question here as to the details; today RFC 5554 governs. We
could use that and the current draft assumes we will. However
in Beijing we became aware of some changes to these details
that would make life much better for GSS authentication of
HTTP. We should resolve this with kitten and replace this note
with a reference to the spec we're actually following.</t>
<t>Typically when considering channel binding, people think of
channel binding in combination with mutual
authentication. This is sufficiently common that without
additional qualification channel binding should be assumed to
imply mutual authentication. Without mutual authentication, only one party
knows that the endpoints are correct. That's sometimes
useful. Consider for example a user who wishes to access a
protected resource from a shared whiteboard in a conference
room. The whiteboard is the initiator; it does not need to
actually authenticate that it is talking to the correct
resource because the user will be able to recognize whether
the displayed content is correct. If channel binding were used
without mutual authentication, it would in effect be a request
to only disclose the resource in the context of a particular
channel. Such an authentication would be similar in concept to
a holder-of-key SAML assertion. However, also note that while
it is not happening in the protocol, mutual authentication is
happening in the overall system: the user is able to visually
authenticate the content. This is consistent with all uses of
channel binding without protocol level mutual authentication
found so far.</t>
<t>RFC 5056 channel binding (also called GSS-API channel
binding when GSS-API is involved) is not the same thing as EAP
channel binding. EAP channel binding is also used in the ABFAB
context in order to implement acceptor naming and mutual
authentication. Details are discussed in the mechanisms
specification <xref target="I-D.ietf-abfab-gss-eap"/>.</t>
</section>
<section title="Host-Based Service Names">
<t>IETF security mechanisms typically take the name of a
service entered by a user and make some trust decision about
whether the remote party in an interaction is the intended
party. GSS-API has a relatively flexible naming
architecture. However most of the IETF applications that use
GSS-API, including SSH, NFS, IMAP, LDAP and XMPP, have chosen
to use host-based service names when they use GSS-API. In this
model, the initiator names an acceptor based on a service such
as "imap" or "host" (for login services such as SSH) and a
host name.</t>
<t>Using host-based service names leads to a challenging trust
delegation problem. Who is allowed to decide whether a
particular hostname maps to an entity. The public-key
infrastructure (PKI) used by the web has chosen to have a
number of trust anchors (root certificate authorities) each of
wich can map any name to a public key. A number of GSS-API
mechanisms suchs as Kerberos <xref target="RFC1964"/> split
the problem into two parts. A new concept called a realm is
introduced. Then the mechanism decides what realm is
responsible for a given name. That realm is responsible for
deciding if the acceptor entity is allowed to claim the
name. ABFAB needs to adopt this approach.</t>
<t>Host-based service names do not work ideally when different
instances of a service are running on different ports. Also,
these do not work ideally when SRV record or other insecure
referrals are used.</t>
<t>The GSS-EAP mechanism needs to support host-based service
names in order to work with existing IETF protocols.</t>
</section>
<section title="Per-Message Tokens">
<t>GSS-API provides per-message security services that can
provide confidentiality and integrity. Some IETF protocols
such as NFS and SSH take advantage of these services. As a
result GSS-EAP needs to support these services. As with mutual
authentication, per-message services will limit the set of EAP
methods that are available. Any method that produces a Master
Session Key (MSK) should be able to support per-message
security services.</t>
<t>GSS-API provides a pseudo-random function. While the
pseudo-random function does not involve sending data over the
wire, it provides an algorithm that both the initiator and
acceptor can run in order to arrive at the same key
value. This is useful for designs where a successful
authentication is used to key some other function. This is
similar in concept to the TLS extractor. No current IETF
protocols require this. However GSS-EAP supports this service
because it is valuable for the future and easy to do given
per-message services. Non-IETF protocols are expected to take
advantage of this in the near future.</t>
</section>
</section>
<section anchor="attribute-providers" title="Future Work:
Attribute Providers">
<t>
This architecture provides for a federated authentication and
authorization framework between IdPs, RPs, principals, and
subjects. It does not at this time provide for a means to
retrieve attributes from 3rd parties. However, it envisions
such a possibility. We note that in any extension to the
model, an attribute provider must be authorized to release
specific attributes to a specific RP for a specific
principal. In addition, we note that it is an open question
beyond this architecture as to how the RP should know to trust
a particular attribute provider.
</t>
<t>There are a number of possible technical means to provide
attribute provider capabilities. One possible approach is for the
IdP to provide a signed attribute request to RP that it in turn
will provide to the attribute authority. Another approach would be
for the IdP to provide a URI to the RP that contains a token of
some form. The form of communications between the IdP and attribute
provider as well as other considerations are left for the future.
One thing we can say now is that the IdP would merely be asserting
who the attribute authority is, and not the contents of what the
attribute authority would return. (Otherwise, the IdP might as well
make the query to the attribute authority and then resign it.)
</t>
</section>
<section anchor="privacy-cons" title="Privacy Considerations">
<t>Sharing identity information raises privacy violations and as described throughout this document an existing architecture is re-used for a different usage environment. As such, a discussion about the privacy properties has to take these pre-conditions into consideration. We use the approach suggested in <xref target="I-D.morris-privacy-considerations"/> to shed light into what data is collected and used by which entity, what the relationship between these entities and the end user is, what data about the user is likely needed to be collected, and what the identification level of the data is.</t>
<section title="What entities collect and use data?">
<t><xref target="abfab-arch"/> shows the architecture with the involved entities. Message exchanges are exchanged between the client application, via the relying part to the AAA server. There will likely be intermediaries between the relying party and the AAA server, labeled generically as "federation".
</t>
<t>In order for the relying party to route messages to the AAA server it is necessary for the client application to provide enough information to enable the identification of the AAA server's domain. While often the username is attached to the domain (in the form of a Network Access Identity (NAI) this is not necessary for the actual protocol operation. The EAP server component within the AAA server needs to authenticate the user and therefore needs to execute the respective authentication protocol. Once the authentication exchange is complete authorization information needs to be conveyed to the relying party to grant the user the necessary application rights. Information about resource consumption may be delivered as part of the accounting exchange during the lifetime of the granted application session.</t>
<t>The authentication exchange may reveal an identifier that can be linked to a user. Additionally, a sequence of authentication protocol exchanges may be linked together. Depending on the chosen authentication protocol information at varying degrees may be revealed to all parties along the communication path. This authorization information exchange may disclose identity information about the user. While accounting information is created by the relying party it is likely to needed by intermediaries in the federation for financial settlement purposes and will be stored for billing, fraud detection, statistical purposes, and for service improvement by the AAA server operator.</t>
</section>
<section title="Relationship between User's and other Entities">
<t>The AAA server is a first-party site the user typically has a relationship with. This relationship will be created at the time when the security credentials are exchange and provisioned. The relying party and potential intermediares in the federation are typically operate under the contract of the first-party site. The user typically does not know about the intermediaries in the federation nor does he have any relationship with them. The protocol interaction triggered by the client application happens with the relying party at the time of application access. The relying party does not have a direct contractual relationship with the user but depending on the application the interaction may expose the brand of the application running by the relying party to the end user via some user interface.</t>
</section>
<section title="What Data about the User is likely Needed to be Collected?">
<t>The data that is likely going to be collected as part of a protocol exchange with application access at the relying party is accounting information and authorization information. This information is likely to be kept beyond the terminated application usage for trouble shooting, statistical purposes, etc. There is also like to be additional data collected to to improve application service usage by the relying party that is not conveyed to the AAA server as part of the accounting stream.
</t>
</section>
<section title="What is the Identification Level of the Data?">
<t>With regard to identification there are several protocol layers that need to be considered separately. First, there is the EAP method exchange, which as an authentication and key exchange protocol has properties related to identification and protocol linkage. Second, there is identification at the EAP layer for routing of messages. Then, in the exchange between the client application and the relying party the identification depends on the underlying application layer protocol the EAP/GSS-API exchange is tunneled over. Finally, there is the backend exchange via the AAA infrastructure, which involves a range of RADIUS and Diameter extensions and yet to be defined extensions, such as encoding authorization information inside SAML assertions.</t>
<t>Since this document does not attempt to define any of these exchanges but rather re-uses existing mechanisms the level of identification heavily depends on the selected mechanisms. The following two examples aim to illustrate the amount of existing work with respect to decrease exposure of personal data.
</t>
<t><list style="numbers">
<t>When designing EAP methods a number of different requirements may need to get considered; some of them are conflicting. RFC 4017 <xref target="RFC4017"/>, for example, tried to list requirements for EAP methods utilized for network access over Wireless LANs. It also recommends the end-user identity hiding requirement, which is privacy-relevant. Some EAP methods, such as EAP-IKEv2 <xref target="RFC5106"/>, also fulfill this requirement.</t>
<t>EAP, as the layer encapsulating EAP method specific information, needs identity information to allow routing requests towards the user's home AAA server. This information is carried within the Network Access Identifier (NAI) and the username part of the NAI (as supported by RFC 4282 <xref target="RFC4282"/>) can be obfuscated.</t>
</list>
</t>
</section>
<section title="Privacy Challenges">
<t>While a lot of standarization work was done to avoid leakage of identity information to intermediaries (such as eavesdroppers on the communication path between the client application and the relying party) in the area of authentication and key exchange protocols. However, from current deployments the weak aspects with respect to security are:
<list style="numbers">
<t>Today business contracts are used to create federations between identity providers and relying parties. These contracts are not only financial agreements but they also define the rules about what information is exchanged between the AAA server and the relying party and the potential involvement of AAA proxies and brokers as intermediaries. While these contracts are openly available for university federations they are not public in case of commercial deployments. Quite naturally, there is a lack of transparency for external parties.</t>
<t>In today's deployments the ability for users to determine the amount of information exchanged with other parties over time, as well as the possibility to control the amount of information exposed via an explict consent is limited. This is partially due the nature of application capabilities at the time of network access authentication. However, with the envisioned extension of the usage, as described in this document, it is desirable to offer these capabilities.</t>
</list>
</t>
</section>
</section>
<!-- ////////////////////////////////////////////////////////////////////////////////// -->
<section title="Deployment Considerations">
<section title="EAP Channel Binding">
<t>Discuss the implications of needing EAP channel
binding.</t>
</section>
<section title="AAA Proxy Behavior">
<t>Discuss deployment implications of our proxy requirements.</t>
</section>
</section>
<section anchor="sec-cons" title="Security Considerations">
<t>This entire document is about security. A future version of the document will highlight some important security concepts.</t>
</section>
<!-- ////////////////////////////////////////////////////////////////////////////////// -->
<section anchor="iana" title="IANA Considerations">
<t>This document does not require actions by IANA.</t>
</section>
<!-- ////////////////////////////////////////////////////////////////////////////////// -->
<section title="Acknowledgments">
<!-- <t>The author would like to thank Sam Hartman for a discussion about all aspects of the
"Federated Authentication Beyond The Web" effort when he was visiting MIT in June 2010.</t>-->
<t>We would like to thank Mayutan Arumaithurai and Klaas Wierenga for their feedback. Additionally, we would like to
thank Eve Maler, Nicolas Williams, Bob Morgan, Scott Cantor, Jim Fenton, and Luke Howard for their feedback on the
federation terminology question.</t>
<t>Furthermore, we would like to thank Klaas Wierenga for his review of the pre-00 draft version.</t>
</section>
<!-- ////////////////////////////////////////////////////////////////////////////////// -->
</middle>
<!-- ////////////////////////////////////////////////////////////////////////////////// -->
<back>
<references title="Normative References">
&RFC2743;
&RFC2865; &RFC3588;
&RFC3748; &RFC3579; &RFC4072; &RFC4282;
&I-D.hansen-privacy-terminology;
&I-D.ietf-abfab-gss-eap;
</references>
<references title="Informative References">
&I-D.nir-tls-eap;
&I-D.ietf-oauth-v2;
&I-D.morris-privacy-considerations;
&RFC4017;
&RFC5106;
&RFC1964;
&RFC2203;
&RFC3645;
&RFC2138;
&RFC4462;
&RFC4422;
&RFC5056;
&RFC5801;
&RFC5849;
&SAML20;
&RFC2904;
</references>
</back>
</rfc>
| PAFTECH AB 2003-2026 | 2026-04-22 22:48:13 |