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IHE ITI White Paper on Authorization

Volume 1 Rough Cut

Outline

Jörg Caumanns, Raik Kuhlisch, Oliver Pfaff, Olaf Rode, Christof Strack, Heiko Lemke

Berlin, 22.12.08

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Editing Team

Authors: Raik Kuhlisch, Jörg Caumanns // Fraunhofer ISSTOliver Pfaff, Markus Franke // Siemens IT Solutions

// and Services Christof Strack, Heiko Lemke // SUN Microsystems

Supervisior: Rob Horn // Agfa Healthcare

Editorial Team: John Moehrke // GE HealthcareLynn Felhofer

Manuel Metz // GIP-DMP

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Schedule

06. Jan Internal Face-to-Face Meeting (ISST, Siemens)

07. Jan Internal Online Meeting (ISST, Siemens, SUN)

08. Jan Preparation of Slides/Paper for the Editorial Team

09. Jan Online Meeting with Editorial Team (19.00 MEZ)

14. Jan Update of Initial Paper for Internal Discussion

16. Jan Internal Online Meeting (ISST, Siemens, SUN, ELGA)

19. Jan Deadline for Internal Comments

20. Jan Preparation of the Initial Paper for the Editorial Team

21. Jan Online Meeting with Editorial Team (16.00 MEZ)

24. Jan Update of Initial Paper and Preparation of ITI Technical Committee

26.-29. Jan Face-to-Face Meeting with ITI Technical Committee

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Storyline of the White Paper

• There is no “one-fits-all” solution for authorization• policies, verifiable attributes, and attribute sources vary• granularity of protected items varies• deployment varies

• Therefore the WP provides a generic toolkit of deployable actors and a methodology to tailor this toolkit to a specific healthcare network’s needs and to identify the required transactions.

• The toolkits reflects the maximal set of attributes and policy sources in a maximally distributed scenario. The methodology helps system architects in selecting the required components and in designing the optimized flow of control.

• For each component and transaction appropriate standards are named. If possible they are mapped onto existing IHE ITI actors and transactions.

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Outline

1. Access Control: Motivation and State-of-the-Art

2. Specific Requirements of Federated Healthcare Networks

3. Generic Access Control Model for Federated Healthcare Networks

4. Methodology for Tailoring the Generic Model

5. Sample Adaptations of the Generic Model

6. Standards for Implementing the Actors and Transactions of the Generic Model

7. Appendix: Glossary of Terms

8. Appendix: Standards and Vocabularies for Attribute Names and Values

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Chapter 1: Access Control – Motivation and State of the Art

Motivation• Privacy and Data Security• Needs-to-Know Principle

State of the Art• Paradigms: DAC, MAC, RBAC, ...• Policy Based Access Control (PEP, PDP, ...)• Standards (SAML, WS*, XACML, XSPA, ...)

Challenge• Solution is driven by the characteristics of the policies: Which

information is needed for policy selection/evaluation and how can this information be obtained in an efficient manner?

• Multiple policy sources and specific workflow aspects add another layer of complexity

• But: Things must be kept simple to be safe and efficient

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Chapter 1: Access Control – Motivation and State of the Art

Generic Model for Access Control (based on XSPA)• Access Control System within each domain• Attribute Management (Directories and Services)

Domain 1: Context Domains• Issuer of a request affecting a protected resource• Management of context attributes• control of the assertion/message flow

Domain 2: Subject Domain (in XSPA part of the issuing domain)• Subject authentication• Management of subject attributes

Domain 3: Resource Domain• management of protected resources (e. g. data base)• management of resource attributes• management of resource security policies• policy enforcement and policy decision

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Generic Model (distributed XSPA)

ACSSTS

Context Domain

ACSSTS

Subject Domain

ACSSTS

Resource Domain

context attributes subject attributes

resource attributes

role activation Identity Prv.

PEP / PDPorg. security policy

request initiator

resource

Attribute Svc.PEP / PDP

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Chapter 2: Specific Requirements of (Federated) Healthcare Networks

Federated Healthcare Environments• Trust Brokerage and Security Token• Federation of the Resource Domain (XCA)• Federated Identities within the Subject Domain (XUA)• Distributed Patient Attributes (XCPI)

Session Control vs. Resource Control• Granularities and flavours of protected resources• The role of the “Purpose” • Instantiation of access rights for organizations

Resource Security through Role Based Access Control• HL7 role engineering• Role activation• HL7/VA access control matrices

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Chapter 2: Specific Requirements of (Federated) Healthcare Networks

The Role of the Patient• Patient Privacy Policies (Consents)• DAC-style vs. RBAC-style PPPs• client-side vs. resource-side enforcement• patient-bound tokens (e. g. EHCs) as access control

measures

Conclusion: Policies and Attributes Needed• patient privacy policy, application policy, resource (data

protection) policy• subject attributes, resource attributes, activity attributes,

context/purpose attributes, patient attributes• Binding of policies and attributes (and attribute sources)

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acute carerecord

Access Control Layering in Healthcare

electronic health record

medicationrecord

e-prescriptionmanagement

application contexts(purpose-driven)

medical resources(data-centric)

session control(DAC-style)

resource control(RBAC-style)

federatedhealthcare infrastructure

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Session Control

• In (distributed) medical treatment scenarios, access to medical data is legitimated by a purpose which is implemented by a medical application

• It is the patient’s right to decide who may act on his data for which purpose. This is reflected by patient-granted admission rights for the corresponding medical services.

• Examples for admission rights:• Person A and Organization B may access my EHR• Any physician to whom I handle over my EHC may

access my medication record

• Admission control is often implemented in a service-specific way; e.g.:• EHC tickets to access a patient’s e-prescriptions• eCR admission codes to access a patient’s case record

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Resource Control

• The objective of resource control is to grant permissions (for operations on object types) to only the persons who need these permissions in order to perform their dedicated functional roles within a medical workflow

• Resource control rights reflect the separation of concerns within an organization and are a measure of data security

• Example for a resource control access right system:• HL7 healthcare scenario roadmap

• Resource access rights can best be expressed using role-based policies. Nevertheless most existing hospital information systems use hard-coded access rules and proprietary permission hierarchies...

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Chapter 3: Generic ACS Model for Federated Healthcare Networks

Extension and Refinement of the Generic Model (Chapter 1)• additional Patient Domain• 2 flavours of the resource domain:

–resource domain–application domain

• each domain controls attributes and policies• each domain may exist with none, one, or multiple

instances

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4-Domain Model (distributed XSPA)

ACSSTS

Context Domain

ACSSTS

Subject Domain

ACSSTS

Patient Domain

ACSSTS

Resource Domain

patient privacy policy (consent)

context attributes subject attributes

resource attributes

role activation

consent activation

Identity Prv.

PEP / PDPorg. security policy

request initiator

resource

Attribute Svc.PEP / PDP

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5-Domain Model (distributed XSPA)

ACSSTS

Context DomainACS

STS

Subject Domain

ACSSTS

Patient Domain

ACSSTS

Resource Domain

patient privacy policy (consent)

context attributes

subject attributes

resource attributes

role activation

consent activation

Identity Prv.

PEP / PDPorg. security policy

request initiator

resource

Attribute Svc.

PEP / PDP

Application Domain

ACSSTS

application attributes

PEP / PDPapp. security policy

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Chapter 3: Generic ACS Model for Federated Healthcare Networks

Identification and Authentication• Subject Authentication (XUA)• Role Attributes and Role Activation• Patient Identification

Privacy Policy Activation and Session Control • Context Activation• Application Policy Selection• Privacy Policy Selection• Separation of DAC- and RBAC-style rules• Policy Decision and Enforcement (Context Domain)• Policy Decision and Enforcement (App Domain)

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Chapter 3: Generic ACS Model for Federated Healthcare Networks

Resource Control• Resource Policy Selection• Patient Privacy Policy Push vs. Pull• Resource Attribute Retrieval• Policy Decision and Enforcement

Actors and Transactions• Security Token Services, Policy Registries and Policy

Repositories, Attribute Services (Directories), PEP and PDP

• Security Token Retrieval, Policy Retrieval, Attribute Retrieval, Role Activation, Policy Decision and Enforcement

• Management Interfaces

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Chapter 4: Methodology

Policy Determination• Session Control vs. Resource Control• Policy Authorities• Paradigms for Patient Privacy Policy, App Policy, Resource Policy• Policy Assignment (Indexing for Retrieval)

Attribute Identification• Identification of Attribute Stubs• Domain Assignment• Policy Assignment• Specification of Attribute Value Sources

Policy Management• Policy Encoding• Policy Deployment

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Chapter 4: Methodology

Access Control Systems within the Domains• PEP/PDP Placement• Policy Retrieval (Pull/Push)• Attribute Retrieval (Pull/Push) • Authorization Request Interface

Integration of the ACSs into the Application Control Flow• Session Management (if required)• Mapping of Resource Requests onto Authorization

Requests• Security Token Control Flow

Policy Lifecycle Management

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Core Methodology

Configuration

Attribute Stubs

Attribute Value

Source

Subject

¬ Subject (Resource,App)e .g. Org. Type

ID DatatypeInternal(Aut/SSO)

External(Classes)

1. Define Attributes (Desired Values)

No Defaults: AuthZ Model (DAC, MAC,

RBAC, ...),Attr. Types/Sources

Defaults:Syntax of policies

2. Policy building by given syntax Policy

3. Policy DeploymentPolicy Svc

Management

Policy Evaluation

Tooltime

RuntimeACS

PolicyFinder

Query (XACML Policy (Set)ID, Target, ...)

App Request

AuthZ RequestApp Config

e. g. XACMLPDP

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Chapter 5: Sample Adaptations of the Generic Model

XSPA Actor Deployment and Flow of Control

Regional Healthcare Network Based on IHE XDS/XUA

Distributed EHR Based on IHE XDS/XCA/XUA

eCR Security Architecture

BPPC (Context Domain Enforcement vs. Resource Domain Enforcement)

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4-Domain Model (XSPA control flow)

ACSSTS

Context Domain

ACSSTS

Subject Domain

ACSSTS

Patient Domain

ACSSTS

Resource Domain

patient privacy policy (consent)

context attributes subject attributes

resource attributes

role activation

consent activation

Identity Prv.

PEP / PDPorg. security policy

request initiator

resource

Attribute Svc.PEP / PDP 2

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Chapter 6: Standards

Layering Opportunities (Message Header, SOAP Header, SOAP Body)

Security Token Encoding and Exchange• SAML and WS Trust• Subject authentication and subject attribute exchange

based on XUA (Protection Token)• Encoding and exchange of policy references and

policies as security tokens (Supporting Token)

Policy Encoding• XACML

Attribute Management and Attribute Retrieval• PWP, PDQ, ...

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Appendix A: Glossary of Terms

Resource Something of value in a network infrastructure to whichrules or policy criteria are first applied before access is granted [RFC 2753]

Subject Identified and authenticated entity (e. g. a human actor)who wants to access a resource

Policy Set of rules to administer, manage, and control accessto [network] resources [RFC 3060]

Condition Representation of the necessary state and/or prerequi-sites that define whether a policy rule’s actions shouldbe performed [RFC 3198]

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Appendix B: Standards and Vocabularies for Attribute Names and Values

Subject Attributes• Administrative Roles• Functional Roles• Organizational Memberships• Organization Types

Patient Attributes (if anything but the ID is needed at all)

Context Attributes• Purpose• Date and Time

Application Attributes (if anything but the ID is needed at all)

Resource Attributes• Resource Type