ABFAB J. Howlett
Internet-Draft Janet
Intended status: Informational M. Wasserman
Expires: September 14, 2012 Painless Security
March 13, 2012
Trust Router Problem Statement
draft-howlett-abfab-trust-router-ps-01.txt
Abstract
This document is a problem statement for a Trust Router Protocol. A
Trust Router Protocol is needed to support large, multihop ABFAB
federations, without the need for credentials to be configured for
every pair of Identity Providers and Relying Parties.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on September 14, 2012.
Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Howlett & Wasserman Expires September 14, 2012 [Page 1]
Internet-Draft Trust Router Problem Statement March 2012
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. High-Level Problems . . . . . . . . . . . . . . . . . . . . . . 4
2.1. Connecting your Partners . . . . . . . . . . . . . . . . . 4
2.2. Identifying your Partners . . . . . . . . . . . . . . . . . 4
2.3. Knowing your Partners . . . . . . . . . . . . . . . . . . . 4
2.4. Policing and Managing Policy . . . . . . . . . . . . . . . 5
3. Specific Problems . . . . . . . . . . . . . . . . . . . . . . . 5
3.1. Many IdPs, Many RPs . . . . . . . . . . . . . . . . . . . . 5
3.2. Frequent Changes in Membership . . . . . . . . . . . . . . 5
3.3. Minimal Costs for Adding a New Partner . . . . . . . . . . 5
3.4. Costs Incurred by the Party that Benefits . . . . . . . . . 5
3.5. Deployment Challenges with Public Key Infrastructure . . . 6
4. Security Considerations . . . . . . . . . . . . . . . . . . . . 6
5. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 6
6. Informative References . . . . . . . . . . . . . . . . . . . . 6
Howlett & Wasserman Expires September 14, 2012 [Page 2]
Internet-Draft Trust Router Problem Statement March 2012
1. Introduction
The ABFAB architecture [I-D.lear-abfab-arch] describes an access
management model that enables the application of federated identity
within a broad range of use cases. This is achieved by building on
proven technologies and widely deployed infrastructures. Some of
these use cases are described in [I-D.ietf-abfab-usecases].
In the canonical case, an ABFAB transaction only implies two
organizations: an Identity Provider (IdP) and a Relying Party (RP).
In this simplest case of a bilateral connection, the amount of
configuration needed by both partners is very small; probably just an
AAA credential and the peer system's host name for the other party.
However, in practice an organization may have more than one partner.
In the case where bilateral connections are used, the amount of
configuration at each partner increases in proportion to the number
of connections. As the number of partners increases, the amount of
configuration churn may become too onerous to manage. Also, the
operational costs of managing that configuration information is
borne, to an unreasonable degree, by the RPs. When a new IdP is
added to a partnership, it is necessary for all of the RPs to update
their configuration information before the new IdP's users will have
full access to the services accessible to the partnership.
This document is a problem statement for a Trust Router Protocol. A
Trust Router Protocol is needed to eliminate the need the need for a
bilateral exchange of credentials between each IdP and RP.
A Trust Router Protocol allows a new partner to be added to an ABFAB
partnership by peering with any member of the Trust Router network,
instead of requiring configuration changes by every partner who may
wish to connect with the new partner. A Trust Router protocol
addresses the problems described in this document by distributing
information about existing trust relationships within the
partnership, thus avoiding the operational costs and limitations of
using a Public Key Infrastructure (PKI).
This document is broken into two sections: High-Level Problems and
Specific Problems. The High-Level Problems section describes the
problems that the Trust Router Protocol has been designed to address
at a conceptual level, and the Specific Problems section discusses a
more concrete set of problems that the Trust Router Protocol is
intended to address.
Howlett & Wasserman Expires September 14, 2012 [Page 3]
Internet-Draft Trust Router Problem Statement March 2012
2. High-Level Problems
2.1. Connecting your Partners
Organizations want to be able to connect to an arbitrary number of
partners without being overwhelmed by configuration management of
many bilateral connections.
2.2. Identifying your Partners
It is not generally sufficient to simply configure a partner. In
most cases, it is also necessary for organizations to have confidence
that the configuration that they have for their partner(s) actually
corresponds to their partner(s) and is not, for example, an attacker
claiming to be their partner. Unfortunately identifying partners and
binding them cryptographically to the corresponding configuration can
be very expensive.
Organizations want to minimise the cost of validating their partners'
identities, and of proving their own identity to their partners.
2.3. Knowing your Partners
Organizations and their partners generally interact within the
context of a particular context. The context can be established in a
number of ways; for example:
o A pair of organization may have a formal business relationship
that unambiguously establishes the nature of the relationship
between the partners (for example, in the case of a supplier's
relationship with a customer). In this case, the customer's
ABFAB-based interactions with the supplier are governed by this
business relationship.
o A group of organization may also share a formal business
relationship (for example, a number of suppliers within a
manufacturer's supply chain). In this case, the business
relationship might govern the ABFAB-based interactions between the
suppliers, and the suppliers and the manufacturer.
o A group of organizations may not share a formal business
relationship but instead share common best practices. In this
case, the best practices might govern the ABFAB-based interactions
between these organizations.
Given the potential diversity of contexts, organizations need to know
which context is in force for a particular ABFAB-based transaction
and apply policy that controls which entities within an organization
Howlett & Wasserman Expires September 14, 2012 [Page 4]
Internet-Draft Trust Router Problem Statement March 2012
are permitted to operate within particular business contexts.
2.4. Policing and Managing Policy
Organizations want to have effective tools for policing and managing
policies controlling ABFAB-based transactions with their partners.
3. Specific Problems
3.1. Many IdPs, Many RPs
It is fairly easy to see how ABFAB, without Trust Routers, could be
deployed in a small federation with stable membership, or even in a
large federation with a single RP that provides services to all of
the other members, such as an industry consortium.
However, there are operational problems that arise when ABFAB is used
in a federation with a large number of RPs providing services to an
even larger number of IdPs. In these cases, it can be challenging to
manage the credentials that need to be exchanged, and manually
configured, between each RP/IdP pair.
3.2. Frequent Changes in Membership
It must be possible to support changes in membership (adding new
partners, or removing former partners) with minimal operational
effort, and without requiring manual configuration changes that could
result in new partners having delayed or incomplete access to
services, or former partners retaining some access to services beyond
the end of their membership.
3.3. Minimal Costs for Adding a New Partner
There is a need to support large federations in a cost-effective
manner. This includes minimizing the operational costs of adding a
new member (either an IdP or RP) to an existing partnership. Without
Trust Router, the operational costs of adding a new member to an
existing partnership might be quite high -- requiring credential
exchange between a large number of parties, and requiring manual
configuration changes on a large number of different systems.
3.4. Costs Incurred by the Party that Benefits
Without Trust Routers, a high portion of the operational cost related
to adding and removing partners is born by the RPs, who need to
maintain bilateral credentials for each IdP whose users can access
the services provided by the RP. This is fine in a case where a
single RP provides services to a group of IdPs that pay for
Howlett & Wasserman Expires September 14, 2012 [Page 5]
Internet-Draft Trust Router Problem Statement March 2012
membership in the group or pay for access to the services, but in a
less-centralized partnership the costs of exchanging credentials with
each IdP could serve as a disincentive for organizations to provide
services to the partnership and/or result in cases where an RP is
unwilling or unable to incur the costs of providing access to new
members. Therefore, it is important that we devise a mechanism where
the operational costs are distributed to the organizations that are
receiving benefit from incurring the costs.
3.5. Deployment Challenges with Public Key Infrastructure
Deployment problems with Public Key Infrastructure (PKI) make it
unsuitable for use by many ABFAB federations. The costs are
prohibitive for the use of ABFAB federations in many educational
environments, the policies of PKI Certificate Authorities are not
well-aligned with the policies of many membership organizations.
Also, the support costs associated with having every every IdP
generate keys and provide a public key (but not their private key) to
each RP in a partnership may be prohivitive.
4. Security Considerations
The topics discussed in this document are likely to be of interest to
the IETF Security Area, and the Internet security community, in
general. However, this is a problem statement document, not a
protocol definition, and therefore it does not define anything with
its own Security Considerations. The Security Considerations for the
protocols discussed in this document are (or will be) provided in the
documents defining those protocols.
5. Acknowledgments
This document was written using the xml2rfc tool described in RFC
2629 [RFC2629].
The following people have provided useful feedback on the contents of
this document: Sam Hartman.
6. Informative References
[I-D.lear-abfab-arch] Howlett, J., Hartman, S., Tschofenig,
H., and E. Lear, "Application Bridging
for Federated Access Beyond Web (ABFAB)
Architecture", draft-lear-abfab-arch-02
(work in progress), March 2011.
[I-D.ietf-abfab-usecases] Smith, R., "Application Bridging for
Federated Access Beyond web (ABFAB) Use
Howlett & Wasserman Expires September 14, 2012 [Page 6]
Internet-Draft Trust Router Problem Statement March 2012
Cases", draft-ietf-abfab-usecases-01
(work in progress), July 2011.
[I-D.mrw-abfab-multihop-fed] Wasserman, M., Tschofenig, H., and S.
Hartman, "Multihop Federations for
Application Bridging for Federation
Beyond the Web (ABFAB)",
draft-mrw-abfab-multihop-fed-01 (work
in progress), July 2011.
[RFC2629] Rose, M., "Writing I-Ds and RFCs using
XML", RFC 2629, June 1999.
Authors' Addresses
Josh Howlett
Janet
EMail: josh.howlett@ja.net
Margaret Wasserman
Painless Security
356 Abbott Street
North Andover, MA 01845
USA
Phone: +1 781 405 7464
EMail: mrw@painless-security.com
URI: http://www.painless-security.com
Howlett & Wasserman Expires September 14, 2012 [Page 7]
