using attribute-based access control to enable attribute-based messaging

IllinoisSecurity Lab

Using Attribute-Based Access Control to Enable

Attribute-Based Messaging

Rakesh Bobba, Omid Fatemieh, Fariba Khan, Carl A. Gunter and Himanshu Khurana

University of Illinois at Urbana-Champaign


ACSAC 2006

Introduction to ABM

Attribute-Based Messaging (ABM): Targeting messages based on attributes.

To: faculty going on sabbatical


ACSAC 2006

Introduction to ABM

Examples• Address all faculty going on sabbatical

next term• Notify all female CS graduate students

who passed qualifying exams of a scholarship opportunity

Attribute-Based Messaging (ABM): Targeting messages based on attributes.


ACSAC 2006

Why ABM?

• Attribute-based systems have desirable properties– flexibility, privacy and intuitiveness

• Attribute-Based Messaging (ABM) brings these advantages to e-mail messaging– enhances confidentiality by supporting

targeted messaging• via dynamic and transient groups

– enhances relevance of messages• by reducing unwanted messages


ACSAC 2006

Challenges

• Access Control – access to such a system should be carefully

controlled• potential for spam • privacy of attributes

• Deployability– system should be compatible with existing

infrastructure

• Efficiency– system should have comparable

performance to regular e-mail


ACSAC 2006

Enterprise Architecture

Ensuing Issues •ABM Address Format, Client I/F

•Access Control - policy specification and enforcement

•Attribute Database creation and maintenance

To: M

anagers

Attr.DB

Policy

Decision

E-mailMTA

ABMServer


ACSAC 2006

Enterprise Architecture cont.

• Attribute database– all enterprises have attribute data about

their users– data spread over multiple, possibly

disparate databases– assume that this attribute data is

available to ABM system• “information fabric” , “data services layer”

• ABM address format −logical expressions of attribute value pairs−disjunctive normal form


ACSAC 2006

Access Control

• Access Control Lists (ACLs)– difficult to manage


ACSAC 2006

Access Control

×Access Control Lists (ACLs)× difficult to manage

• Role-Based Access Control (RBAC)– simplified management if roles already exist


ACSAC 2006

Access Control

×Access Control Lists (ACLs)× difficult to manage

× Role-Based Access Control (RBAC)× simplified management if roles already exist

• Attribute-Based Access Control (ABAC)−uses same attributes used to target messages−more flexible policies than with RBAC

• Access policy −XACML is used to specify access policies−Sun’s XACML engine is used for policy decision


ACSAC 2006

Access Control cont.

• Problem– need policy per logical expression– policy explosion

• Solution?– one policy per <attribute,value>


ACSAC 2006

Deployability

• Use existing e-mail infrastructure (SMTP)– address ABM messages to the ABM server

(MUA) and add ABM address as a MIME attachment

• No modification to client– use a web server to aid the sender in

composing the ABM address via a thin client (web browser)

• E-mail like semantics– policy specialization


ACSAC 2006

PDPSun’s XACML

Engine

Sender

AttributeDB

MS SQL ServerPolicyxml

ABM ServerWeb ServerWindows IIS

MTA

PS

1

PS

8

PS2

AR2AR1

AR

3

PS7

AR

4

MS1

MS

2

Putting It All Together

LegendPS: Policy

SpecializationMS: MessagingAR: Address

Resolution


ACSAC 2006

Security Analysis

• Problem– open to replay attacks

• Solution– MTA configured with SMTP

authentication• with additional message specific checks


ACSAC 2006

Experimental Setup

• Measured– latency over regular e-mail

• with and without access control

– latency of Policy Specialization

• Setup– up to 60K users – 100 attributes in the system

• 20% of attributes common to most users• 80% of attributes sparsely distributed


ACSAC 2006

Results


ACSAC 2006

Results Continued…

0

2

4

6

8

10

12

14

143 282 398 568 674

Number of Policies (Number of policies ~= 5 * Number of attributes)

Tim

e (s

ec)

Policy Specialization Latency


ACSAC 2006

Other Considerations

• Policy Administration– one policy per <attribute ,value> not per

address– further be reduced to one policy per

attribute

• Privacy– of sender and receivers– of ABM address

• Usability– user interfaces


ACSAC 2006

Related Work

• Technologies– List Servers– Customer Relationship Management

(CRM)

• Secure role-based messaging• WSEmail


ACSAC 2006

Future Work

• Inter-domain ABM– e.g., address doctors in the tri-state area who

have expertise in a specific kind of surgical procedure

– challenge – “attribute mapping”– application in ‘emergency communications’

• Encrypted ABM


ACSAC 2006

using attribute-based access control to enable attribute-based messaging

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