Authentication Step-Up Protocol and Metadata Version 1.0

Authentication Step-Up Protocol and Metadata Version 1.0

Working Draft 09.2

14 September 2016

Technical Committee:

OASIS Electronic Identity Credential Trust Elevation Methods (Trust Elevation) TC

Chairs:

Abbie Barbir (), Aetna

Don Thibeau (), Open Identity Exchange

Editors:

Andrew Hughes (), Individual

Peter Alterman (), SAFE-BioPharma Assn.

Shaheen Abdul Jabbar (), JPMorgan Chase Bank, N.A.

Abbie Barbir (), Aetna

Mary Ruddy (), Identity Commons

Additional artifacts:

• None

Related work:

This specification replaces or supersedes:

• None

This specification is related to the other work products of the Trust Elevation TC:

• Analysis of Methods of Trust Elevation Version 1.0.Edited by Peter Alterman, Shaheen Abdul Jaabar, JaapKuipers, Thomas Hardjono, and Mary Ruddy. 7 April 2013. OASIS Committee Note Draft 06.
• Survey of Methods of Trust Elevation Version 1.0. Edited by Peter Alterman, Shaheen Abdul Jabbar, JaapKuipers, Thomas Hardjono and Mary Ruddy. 24 September 2012. Working Draft 1.3.
• Electronic Identity Credential Trust Elevation Framework Version 1.0. Edited by Peter Alterman, Shaheen Abdul Jabbar, Abbie Barbir, Mary Ruddy, and Steve Olshansky. 22 May 2014. OASIS Committee Specification 01. Latest version:

Declared XML namespaces:

• None

Abstract:

Electronic Identity Credential Trust Elevation Methods are used to increase assurance in entity identification using authentication events and related entity information for the purpose of risk mitigation when making access control policy decisions.

The goals of this Fourth Deliverable are:

• To propose simple Trust Elevation architectural patterns demonstrating the use of Trust Elevation in modern Access Control architectures.
• To describe a common metadata set, mechanisms and protocol elements for Trust Elevation information exchanges.
• To promote the use of Trust Elevation elements to facilitate standardization among the many technologies and approaches currently in use for credential & authentication risk mitigation.

Status:

This Working Draft (WD) has been produced by one or more TC Members; it has not yet been voted on by the TC or approved as a Committee Draft (Committee Specification Draft or a Committee Note Draft). The OASIS document Approval Process begins officially with a TC vote to approve a WD as a Committee Draft. A TC may approve a Working Draft, revise it, and re-approve it any number of times as a Committee Draft.

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Table of Contents

1Introduction

1.1 Terminology

1.2 Normative References

1.3 Non-Normative References

2Landscape and Context

2.1 Goals of the Fourth Deliverable

3Conceptual Models

3.1 Trust Elevation Core Model

3.2 Trust Elevation Concepts

3.3 Use of Authorization Architectures and Models

4Architecture & Design

4.1 Trust Elevation System Context

4.2 Assumptions for Trust Elevation Systems

4.3 Architecture & Design Factors

4.4 Trust Elevation Architecture Components

4.5 Other Architecture Components

5Implementation Considerations

5.1 Orchestration

5.2 Enumeration of Authentication Methods

5.3 User Enrolment

6Trust Elevation Sequence (Example)

6.1 Use Case: Online banking transactions

7Metadata and Assertions

7.1 Component-Component Communications

7.2 PDP to TE Method Determiner Request

7.3 TE Method Determiner to PDP Response

8Conformance

Appendix A.Acknowledgments

Appendix B.State Models for Assurance Level Evaluation

8.1 Evaluation of Assurance Requirements at Transaction Time

Appendix C.Revision History

trust-el-protocol-v1.0-wd092Working Draft 09.212 September 2016

Standards Track DraftCopyright © OASIS Open 2016. All Rights Reserved.Page 1 of 31

1Introduction

1.1Terminology

The key words “MUST”, “MUST NOT”, “REQUIRED”, “SHALL”, “SHALL NOT”, “SHOULD”, “SHOULD NOT”, “RECOMMENDED”, “MAY”, and “OPTIONAL” in this document are to be interpreted as described in [RFC2119].

1.2Normative References

[trust-el-analysis-v1.0]

Analysis of Methods of Trust Elevation Version 1.0.Edited by Peter Alterman, Shaheen Abdul Jaabar, JaapKuipers, Thomas Hardjono, and Mary Ruddy. 7 April 2013. OASIS Committee Note Draft 06.

[trust-el-survey-v1.0]

Survey of Methods of Trust Elevation Version 1.0. Edited by Peter Alterman, Shaheen Abdul Jabbar, JaapKuipers, Thomas Hardjono and Mary Ruddy. 24 September 2012. Working Draft 1.3.

[trust-el-framework-v1.0]

Electronic Identity Credential Trust Elevation Framework Version 1.0. Edited by Peter Alterman, Shaheen Abdul Jabbar, Abbie Barbir, Mary Ruddy, and Steve Olshansky. 22 May 2014. OASIS Committee Specification 01. Latest version:

[NIST800-63-2] NIST Special Publication 800-63-2,Electronic Authentication Guideline, August 2013.

[NIST800-162]NIST Special Publication 800-162,Guide to Attribute Based Access Control (ABAC) Definition and Considerations, January 2014.

[RFC2119]Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, <

[UMA]Hardjono, T., Maler, E., Machulak, M., Catalano, D. User-Managed Access (UMA) Profile of OAuth 2.0, April 2015.

[X.1252]Recommendation ITU-T X.1252 (2010). Baseline identity management terms and definitions.

[XACML3]OASIS Standard, eXtensible Access Control Markup Language (XACML) Version 3.0, 22 January 2013.

All text is normative except for labeled examples and notes.

1.3Non-Normative References

[ISO ISMS]ISO/IEC 27000:2014 Information technology -- Security techniques -- Information security management systems -- Overview and vocabulary, 2014.

[NIST800-37-1]NIST Special Publication 800-37 r1, Guide for Applying the Risk Management Framework to Federal Information Systems: A Security Life Cycle Approach, June 2014.

[IDMgmt]Backend Attribute Exchange (BAE) v2.0 Overview

[OAuth2]Hardt, D., Ed., "The OAuth 2.0 Authorization Framework", RFC 6749, DOI 10.17487/RFC6749, October 2012, <

[OMB M-04-04]Joshua B. Bolten, U.S. Government Office of Management and Budget,
E- Authentication Guidance for Federal Agencies, December 2003.

[OpenID.Core]Sakimura, N., Bradley, J., Jones, M., de Medeiros, B., and C. Mortimore, “OpenID Connect Core 1.0,” August 2015.

[SAML2]OASIS Standard, Security Assertion Markup Language (SAML) Version 2.0, 2 December 2009.

[SAMLAC]OASIS Standard, Authentication Context for the OASIS Security Assertion Markup Language (SAML) Version 2.0, 15 March 2005.

[X.1254]Recommendation ITU-T X.1254 (09/2012). ITU Telecommunication Standardization Sector (ITU-T) Entity authentication assurance framework.

[X.1255]Recommendation ITU-T X.1255 (09/2013). Framework for discovery of identity management information.

2Landscape and Context

This document, the fourth deliverable of the OASIS Trust Elevation Technical Committee, builds on the work of the first three. To recap: the first deliverable, Survey of Methods of Trust Elevation Version 1.0[trust-el-survey-v1.0], consists of a broad overview of current and near-future online trust elevation techniques used for (or capable of) elevating a relying party’s assurance that the user requesting access to its resources is actually the person he or she claims to be. The second deliverable, Analysis of Methods of Trust Elevation Version 1.0[trust-el-analysis-v1.0], evaluated how each of the identified trust elevation mechanisms operated and what threats they mitigated that added to the relying party’s confidence in the identity asserted. A discussion of the methodology used to analyze the identified mechanisms has been included in that deliverable. The third deliverable, Electronic Identity Credential Trust Elevation Framework Version 1.0[trust-el-framework-v1.0], is an abstraction intended to help to develop applications conforming to an accepted way of elevating trust of a digital identity.

As has been the pattern for this TC’s deliverables, this fourth deliverable builds on the work of the first three and specifies design considerations, implementation considerations and metadata for the elevation of trust through increased identification.

2.1Goals of the Fourth Deliverable

Trust Elevation Methods are used to increase assurance in entity identification using authentication events and related entity information for the purpose of risk mitigation when making access control policy decisions.

The goals of this Fourth Deliverable are:

• To propose simple Trust Elevation architectural patterns demonstrating the use of Trust Elevation in modern Access Control architectures.
• To describe a common metadata set, mechanisms and protocol elements for Trust Elevation information exchanges.
• To promote the use of Trust Elevation elements to facilitate standardization amongthe many technologies and approaches currently in use for credential & authentication risk mitigation.

3Conceptual Models

This section is non-normative.

3.1Trust Elevation Core Model

As described in Electronic Identity Credential Trust Elevation Framework Version 1.0, the following depicts the core model for Trust Elevation.

3.2Trust Elevation Concepts

While the flow diagram above is easy to understand, implicit in the core model are several key components and processes, as shown in Section 4.2. The first of these is a component which functions as a policy engine capable of consuming the asserted user data and making a determination as to whether that data satisfies the resource’s policy for authentication risk mitigation. The resource manager must have previously performed a risk assessment and adopted a risk mitigation strategy([NIST RMF] and [ISO ISMS] are examples of methodologies for these antecedent steps).

The second key component is again an antecedent service generated during the risk assessment and mitigation process. It is composed of a capability to recognize which, if any, risks have been adequately mitigated by the initial transaction, which risks remain to be mitigated and preferred methods for satisfying the remaining needs.

The third key component is a component for evaluating the success of the trust elevation transaction. This could be an iteration of the first component, but it has been broken out in the above graphic to clarify the decision flow.

While these components are necessary to implement trust elevation of a presented online identity, they require the resource manager to have engaged in prior planning and assessments in order to generate the information necessary to direct the behavior of the components. In addition to implementing recognized, standards-based risk assessments, the prior work of this Technical Committee provide the necessary guidance for populating the decision-making components of the core model as well as most comparable models.

Trust Elevation methods are used to increase confidence in entity identification using authentication events and related entity information for the purpose of increased risk mitigation when making access control policy decisions.

Levels of Assurance models are structured such that increased risk mitigation results in increased credential or identity assurance level trust. These models require determination of a given transaction’s identity and authentication risk, expressed in terms of level of assurancerequirements. Policies are designed such that credential or identity assurance level must meet or exceed the transaction’s level of assurance requirement.

As described in Electronic Identity Credential Trust Elevation Framework Version 1.0,entity identification confidence may be increased by: mitigating an authentication threat not addressed by the original authentication exchange; improved mitigation of the original authentication threat, or examination of contextual or environmental factors to corroborate the existing identification.

The definition of the composition of a particular assurance level scheme, and related policy evaluation criteria, is the responsibility of the parties involved in the transactions. The scheme should be tailored to the risk tolerance and requirements of the relying party. In other words, it is up to the resource manager to determine when sufficient mitigations of risk have occurred.

3.3Use of Authorization Architectures and Models

Another way to look at Trust Elevation is as a species of transaction or access control authorization. From this perspective, evaluation of the current state versus policy requirements results in decisions to ‘Permit’, ‘Deny’, or ‘Require Elevation’.

The Trust Elevation core model is compatible with other published authorization models, such as: Attribute Based Access Control (ABAC)[NIST800-162], User Managed Access ([UMA]), [OAuth2], [XACML3], and SAML Backend Attribute Exchange.

3.3.1Attribute Based Access Control Model

This section illustrates how Trust Elevation would fit into an Attribute Based Access Control model.

[NIST SP800-162] describes the elements of an Attribute Based Access Control Model.

As shown in the figure below, the primary components of Authorization Services are the Policy Enforcement Point (PEP) which intercepts resource requests; and, the Policy Decision Point (PDP) which checks supplied attributes versus access control policy. The PDP can obtain additional attributes from environmental conditions, Policy Information Point (PIP) and other sources.Based on the policy evaluation, the PDP instructs the PEP to permit or deny access to the resource.

In the diagram below, when the Authorization Services determine that Trust Elevation is required, the Trust Elevation Services take information from “Authentication Services” and “Risk-Based Engine” to evaluate what Trust Elevation Method should be used to achieve the desired result.

3.3.2User Managed Access Authorization Model

The User-Managed Access protocol (UMA) defines a mechanism for a policy enforcement point – known as the resource server – to delegate authorization of a requesting party to a policy decision point – known as the authorization server – using elements of the OAuth 2.0 authorization framework.

To gain access to a protected resource, an UMA client (web or mobile application operating on behalf of a requesting party) must present a valid access token, called a requesting party token (RPT), to the resource server. The RPT must be valid and associated with sufficient authorization data, issued through a trust elevation process, before the resource server can grant access.

The authorization server, guided by policies set by the owner of the protected resource, elevates trust by testing whether the requesting party meets the policies. As part of this process, it coulddemand that the requesting party (or the client on their behalf) provide claims, such as identity information or even promises to adhere to constraints set by the resource owner, such as an embargo on information release until a certain date.

One policy the authorization server can consider is what mechanism was used to authenticate the person. UMA doesn’t require use of any particular authentication protocol, but works especially well with OpenID Connect.

The OpenID Connect Core specification defines two claims in the ID Token format called acr and amr, which provide details about what type of authentication was performed. Their values can be defined by a domain, a federation, a global registry, or some other trust framework. An UMA authorization server can test a requesting party against policies to evaluate the sufficiency of the authentication mechanism as provided in values of these claims.

In the event that the mechanism was not sufficient, the authorization server can indicate the reason for the authorization failure and what type of credentials would satisfy the policy. At this point, the client can request re-authentication from the OpenID Provider and ultimately re-request the RPT token. This flow would constitute trust elevation by step-up authentication.

3.3.3XACML Authorization Model

The eXtensible Access Control Markup Language (XACML) standard defines a reference architecture for Attribute-Based Access Control (ABAC), a language for expressing access control rules and policies, and a protocol for generating and processing access control requests and returning responses.

Access to resources is mediated by a Policy Enforcement Point (PEP), which relies on decisions from a Policy Decision Point (PDP). When a user attempts to access a protected resource, the PEP assembles a request, which provides attributes about the user, the resource, the environment, and the action requested. The PEP communicates the request to the PDP, which evaluates it according to pre-defined policies.

To perform Trust Elevation, the access control policy can specify how users must be authenticated, including parameters such as authentication method, credentials accepted, and levels of assurance. Trust elevation in this context means enhancing authentication and/or authorization by means of requiring additional attributes.

Consider the following example: a user requests access to a protected resource. The access control policy governing the resource requires multi-factor authentication using a strongly vetted identity credential by means of setting the MustBePresent attribute to TRUE. The PEP controlling access to the resource has only hitherto validated the user identity by means of a lower assurance username/password combination. When the PEP initially formulates the request, it bases the user identity attribute on the previous username/password authentication event. When the PDP receives the request, it evaluates the request according to the appropriate policy, based on the resource. Since MustBePresent = TRUE, the PDP renders an “Indeterminate” decision, with a status code of “urn:oasis:names:tc:xacml:1.0:status:missing-attribute”. Upon receiving this “Indeterminate” with MissingAttribute status decision from the PDP, the PEP may resubmit a request after acquiring the proper attributes. In this case, the proper attributes could only be gathered through a step-up authentication event. This sequence constitutes a sample Trust Elevation event.

Alternatively, security administrators and resource owners may devise a series of Boolean attributes to test for authentication methods used, i.e.: