Process Model for Access Control

Wael HassanUniversity of Ottawa

Luigi Logrippo, Université du Québec en Outaouais

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Goal

Create a Privacy Model that reduces attacks by following privacy specifications while detecting conflict

Why?

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Security and Privacy Breaches

Process

• 60% of security attacks are internal• Attacks come from legitimate users

Reason

users bypass the process

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Plan

• Basics• Existing Models• Privacy

– Issues and requirements– Concept of process based privacy

• Evaluation– Support of existing concepts– Advantages over existing models

• Verification• Conclusion

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Back to Basics

Subject: wael Students

Verb: can access can access

Object: computer their office

What is the structure of a secure access control instruction?

Single Group

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Security

• Basic:- – Identity Access Right

• An identity justifies an access-right– Example: given I am a wael, I can access my lab

• Extended:-– Identity1, Identity2 Forwarding Right (object)

• A right is owned and can be forwarded (delegated)– Example: given I am an assistant in the admissions department,

» I own the right to access personal student file,» I can allow Jasmine access to my file

• Combined:-– Identity1, Identity2 Concurrent Access(object)

• Two subjects may be allowed to have concurrent access to an object

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Privacy

• Basic:-– Purpose Access-Right (Identity)

• A purpose justifies access-right • Example: To update student profile,

– Jo-Anne needs to have access to accepted student application data

• Extended:- – Step Forwarding Right (Identity1, Identity2)

• A step which can be owned by a person in a process suggests a right, and that right may be forwarded (delegated) iff the recipient has access to the process/step.

– Example: given that Jo-Anne participates in the admissions procedure, » She is assigned access to activity open personal student file,» She can allow Jasmine (another officer) access to the same file as long as

she has the authority and she is assigned to the process

• Combined:-– Process1, Process2 Concurrent Access(object)

• Two subjects participating in two processes may or not have concurrent access to certain objects.

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Existing Models

There are 3 existing security models that we inherit

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Bell-Lapadula

Intended for military applications,

Flow Based

1. Security Clearances

2. Security Requirement

A can access y iff – clearance of A > requirement of y

A can forward access to y for B iff – clearance of B > requirement of y

A

X

By Level

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Chinese Wall

Originally intended for banking applications• Creates separation of concerns groups• Group A & Group B cannot share access to an object

set {x,y,z}

A BX

Y

z

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RBAC

Role based Access Control• Principle

– Group people in order to reduce management overhead

• Application– Corporate

• Uses corporate hierarchy to suggest groups

• Example:• Director, Executive Assistant

• All Directors have access to client accounts

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Issues with current systems

When applied to privacy

• They only answer – Does a person A have access to object X

• They don’t – Capture context and purpose of an operation

• They grant– Access once and for all times, irrelevant of the job function

Therefore, they do not satisfy privacy principles of

collection, retention, distribution

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What is needed

• Privacy requires the ability to say– Does

• a person A have access to resource X for purpose P

– Is • a person A trying to gain access to a resource x

as a part of a process

– Is • a person A trying to gain access in the proper

sequence of operation

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Process Based Governance

Governance of organizations by

specifying control of access

(to information)

by applying policies

to processes

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Process Based Control

• A business process is a unit that can be composed of steps and/or processes.

• Steps in a process are sequenced

Process

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In a business process environment it should be • Easy to tie purposes to actions• Possible to apply invariants for a complete structure• Easy to trace policy modifications

Business Process

Loan Processing

Receive Loan Verify Credit Reject Loan

Verify Credit

Receive Card Application Call CreditCheck Process Answer

Provide FeedbackCreate

CardMail Response

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Process Approach Supports

• Flow of information (Bell Lapadula)

• Separation of concerns (Chinese Wall)

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Information flow

• A part of standard procedures is delegating work to others.– Example: delegate meeting announcement to

secretary

• Using process model– Action delegate meeting, allowed in a process – Action meeting cancellation cannot be

delegated

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Separation of Concerns

• In the banking industry, different groups may not share access to particular resources.

• Using process model we can set rules to separate groups– Example:

• No data that admission and scholarship share

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Advantages

• Captures context

• Simplifies management (privacy)

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Captures Context

• As a part of credit application process (x,y,z,t), an employee A receives access to credit information in step z.– A can download all credit information of all customers on file

• When using a process model, – access is granted or revoked based on the sequence of

operations. – Therefore, under the process model, an employee A will only

have access If steps x & y have been performed– Access will be revoked after operation t is completed

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Simplifies Management

• Privacy is dependent on the application and not on the identity

• An identity can have a role which is involved in several functions. Its privileges are dependent on process.

• Grouping policies per process reduces time and management policies that are based on roles.

• Example:– Old

• If rank is General, then grant access• If rank is secretary and name is Lise then grant access

– New:• Secretary allow-access step 3• General allow-access process change-direction

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Implementation and Validation

• A validation environment is provided by the language Alloy

• A formal language based on set theory and first order predicate calculus – Model analyser– Consistency checker– Being developed at MIT

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AlloySignatures or elements are the basic constructs of an Alloy model; they are a cluster of relationships grouped in a class like structure.

1. Sig [abstract] enterprise {2. root : CEO3. }{4. [lone] root5. }

1. abstract sig process {2. parent : lone process, 3. composedOf : set steps4. }

Process

abstract sig policy { attachedTo : lone process, permitted: role -> process, denied : role -> process

Policy

Enterprise

}no permitted & denied role.permitted in attachedTo role.denied in attachedTo }

Facts & Rules

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Alloy Separation of Concerns

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Architecture

UML Model

Verification

Alloy Meta Model

Alloy Policy Specification

TranslationManual Translation

Manual

ManualVerification

XACML

ebXML

ManualVerification

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Pragmatic Goals

• GUIs to formulate validated policies• Able to answer questions:

– Given an enterpise model and a set of policies• Who can/cannot and under what circumstances• Given circumstances, who can/cannot?• Is there inconsistency or incompleteness?

• Automatic translation between – GUI representation– XACML representation– Formal representation (Alloy or other)

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Conclusion

Privacy requires a native model; The transposition of existing security models

does not address the right requirements.

We propose a process based model that attaches policies to processes which are

composed of activities,

We use Alloy as model analyzer to verify properties.

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Thanks from

Wael Hassan, Luigi Logrippowael@ieee.org, luigi@uqo.ca