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TRBAC: A Temporal Role-Based Access Control Model Elisa Bertino CERIAS and CS Department Purdue University What is TRBAC? RBAC Model [Sandhu 98] Temporal constraints on role activations/deactivations What is TRBAC?

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Trbac a temporal role based access control model l.jpg

TRBAC: A Temporal Role-Based Access Control Model

Elisa Bertino

CERIAS and CS Department

Purdue University


What is trbac l.jpg
What is TRBAC?

RBAC Model [Sandhu 98]

Temporal constraints on role

activations/deactivations


What is trbac3 l.jpg
What is TRBAC?

  • An active role is a role that a user can activate during a session (that is,the user can acquire the role’s)

  • A role can be active in certain time periods and non active in other:

    • Role activation: non active active

    • Role deactivation: active non active


Why trbac l.jpg
Why TRBAC?

  • Often roles are characterized by a temporal dimension :

    • Job functions may have limited or periodic time duration

    • There may be activation dependencies among roles


Trbac main features l.jpg

ROLE TRIGGERS

TRBAC: Main Features

  • Periodic activations/deactivations of roles

  • Temporal dependencies among role activations/deactivations


Trbac main features6 l.jpg
TRBAC: Main Features

  • Role triggers may cause either:

    • Immediate activations/deactivations, or

    • Deferred activations/deactivations

  • Run-time requests to dynamically change the status of a role


Trbac main features7 l.jpg
TRBAC: Main Features

  • Priorities for:

    • Periodic activations/deactivations

    • Role triggers

    • Runt-time requests

  • Priorities are used for conflict resolution


Trbac periodic events l.jpg
TRBAC: Periodic Events

Definition: (Periodic Event)

A periodic event is a tuple (I,P,p:E) where I is a time interval, P is a periodic expression, p:E is a prioritized event expression, EÎ {activate R, deactivate R}, RÎ Roles

([7/1/00,12/31/00], night-time, VH: activate, doctor-on-night-duty)

([7/1/00,12/31/00], day-time, VH: deactivate, doctor-on-night-duty)


Trbac role triggers l.jpg
TRBAC: Role Triggers

Definition: (Role Trigger)

Role triggers are of the form:

E1,…En,C1,…Ck p:E after Dt

where Ei’s are event expressions, EiÎ {activate R, deactivate R}, Cj’s are role status expressions, CjÎ {active R, not active R}, RÎ Roles, p:E is a prioritized event expression and Dt is a temporal displacement


Role triggers example l.jpg
Role Triggers: Example

activate doctor-on-night-duty VH: activate nurse-on-nigth-duty

activate nurse-on-day-duty H: activate nurse-on-training after 2 Hours


Role activation base l.jpg

([1/1/00,12/31/00], night-time, VH:activate doctor-on-night-duty)

([1/1/00,12/31/00], day-time, VH:deactivate doctor-on-night-duty)

([1/1/00,12/31/00], day-time, VH:activate doctor-on-day-duty)

([1/1/00,12/31/00], night-time, VH:deactivate doctor-on-day-duty)

activate doctor-on-night-duty H: activate nurse-on-nigth-duty

deactivate doctor-on-night-duty H: deactivate nurse-on-nigth-duty

activate doctor-on-day-duty H: activate nurse-on-day-duty

deactivate doctor-on-day-duty H: deactivate nurse-on-day-duty

activate nurse-on-day-duty H: activate nurse-on-training after 2 Hours

deactivate nurse-on-day-duty VH: deactivate nurse-on-training

Role Activation Base

RAB = Periodic Events + Role Triggers


Trbac runtime request expressions l.jpg
TRBAC: Runtime Request Expressions doctor-on-night-duty)

Definition: (Runtime Request Expression)

A runtime request expression has the form:

p:E after Dt

where p:E is a prioritized event expression and Dt is a temporal displacement

deactivate nurse-on-training after 2 Hours

activate emergency-doctor


Trbac formal aspects l.jpg
TRBAC: Formal Aspects doctor-on-night-duty)

  • The Execution Model of a RAB specifies, for each istant t, the set of events that should occur at time t according to:

    • periodic events & triggers in the RAB

    • runtime request expressions

    • priorities


Trbac formal aspects14 l.jpg

activate R deactivate S doctor-on-night-duty)

activate S deactivate R

Requests: activate R, activate S

TRBAC: Formal Aspects

  • Some specifications may yield no execution model, while some ambiguos specifications may admit two or more models


Trbac formal aspects15 l.jpg
TRBAC: Formal Aspects doctor-on-night-duty)

  • Safeness condition that guarantees that a given RAB has exactly one model

  • It exploits the notion of dependency graph

    • No cycles involving conflicting events

  • Safeness check is polynomial in the RAB dimension


Trbac architectural aspects l.jpg
TRBAC: Architectural Aspects doctor-on-night-duty)

  • At each time it is necessary to know which are the active roles, on the basis of the RAB and runtime requests

  • A request by a user to activate a role is authorized if:

    • The user has the authorization to play that role

    • The role is active at the time of the request


A possible architecture l.jpg

Active Roles doctor-on-night-duty)

Events

Action

Handler

Trigger

support

Actions

PE

Handler

A table which contains the

roles that can be activated

DA

Handler

RTR

Handler

It is in charge of firing triggers according to their priorities. If the action(s) caused by the trigger(s) are instantaneous, it returns them to the Action Handler. If the actions have to be deferred, it inserts them into Deferred_Actions

A global event base which records

The activations/deactivations of roles

Triggers

It is in charge of updating table Active_Roles according to the requests of the other modules. It uses table Actions to solve potential conflicts

A table which contains the actions to be potentially executed on Active_Roles

Deferred

Actions

Safeness

Checker

It is activated each time a runtime request is issued. If the request is for an immediate action, it returns the action to the Action_Handler, if it is for a deferred action, it inserts the action into Deferred_Actions

It is in charge of managing periodic events and inserting/deleting the corresponding actions into/from table Deferred_Actions

It is in charge of executing deferred actions on the basis of the content of table Deferred_Actions

Periodic events

A table which contains the

specified triggers

runtime requests

triggers

It is activated each time a trigger is inserted/modified to verify whether safeness is preserved

A table which contains an entry for each deferred action

A Possible Architecture


Generalized trbac gtrbac l.jpg
Generalized TRBAC (GTRBAC) doctor-on-night-duty)

  • Motivations:

    • TRBAC does not distinguish between a role being enabled and a role being active

    • A role is enabled if the temporal conditions associated with it are satisfied

    • A role is active if a user has logged in the role

    • Only enabled roles can be activated

    • Because of such limitations, TRBAC cannot support some forms of constraints, such as the maximum number of activations of a role by a user in a given time interval


Gtrbac l.jpg
GTRBAC doctor-on-night-duty)

  • GTRBAC extends TRBAC by introducing temporal conditions on:

    • User-role assignments

    • Role-permission assignments

  • A large number of constraints can thus be supported


Gtrbac examples of constraints l.jpg
GTRBAC – Examples of Constraints doctor-on-night-duty)

  • Constraints on the number of concurrent activations

    • “there can be at most 10 users activating the role DayDoctor at a time”

  • Constraints on the number of total activations in a given period

    • “the role HeadNurse can be activated at most 2 times per day”


X gtrbac motivations l.jpg
X-GTRBAC - Motivations doctor-on-night-duty)

  • Role Based Access Control Model

    • Many benefits over traditional access control models when applied to emerging applications

  • XML is a uniform platform for information interchange

    Our Goal

    XML + RBAC extension

    To provide access control framework for Web-Services environments


X gtrbac why xml l.jpg
X-GTRBAC - why XML? doctor-on-night-duty)

XML - main benefits:

  • Uniform, vendor-neutral representation of enterprise data

  • Mechanism for interchange of information across heterogeneous systems

  • Extensible syntax and semantics

  • Widespread support from main platforms and tool vendors


X rbac language l.jpg
X-RBAC Language doctor-on-night-duty)

  • Modeling RBAC Elements

  • Users

XML User Sheet (XUS)

- credential types

XML CredType Definition

  • Roles

XML Role Sheet (XRS)

- separation of duty

XMLSoD Definition

- temporal constraints

XML TempConst Definition

- triggers

XML Trigger Definition

  • Permissions

XML Permission Sheet (XPS)


X rbac language24 l.jpg
X-RBAC Language doctor-on-night-duty)

  • Policy Administration

  • User-to-Role Assignment

XUS

XRS

XURAS

XML User-to-Role Assignment Sheet

(XURAS)


X rbac language25 l.jpg
X-RBAC Language doctor-on-night-duty)

  • Policy Administration

  • Permission-to-Role Assignment

XPS

XRS

XPRAS

XML Permission-to-Role Assignment Sheet

(XPRAS)


Xus grammar l.jpg
XUS Grammar doctor-on-night-duty)

</XUS>

<!-- User Definitions >

</XUS>

<!-- User Definitions >::=

<Users> {<!-- User Definition>}+

</Users>

<!-- User Definition> ::=

<Useruser_id = (id)>

<UserName> (name) </UserName>

{<!--CredType>}+

<MaxRoles>(number)</MaxRoles>

</User>

<!—CredType > ::=

<CredTypecred_type_id =(id)>

<type_name> (name)</type_name>

<!-- Credential Expression>

</CredType>

<!-- Credential Expression> ::=

<CredExpr>

{<(attribute name)> (attribute value)

</(attribute name)>}+

</CredExpr>


An xml instance of xus l.jpg
An XML instance of XUS doctor-on-night-duty)

<XUS>

<Useruser_id=“j1">

<UserName >John</ UserName >

<CredTypecred_type_id ="C100">

< type_name >Nurse</type_name>

<CredExpr>

<age> 30 </age>

<field> opthalmology </field>

<level> 5 </level>

<status> single </status>

</CredExpr>

</CredType>

< MaxRoles>2</MaxRoles>

</User>

<User> … </User>

….

</XUS>


Xrs grammar l.jpg
XRS Grammar doctor-on-night-duty)

<!-- XML Role Sheet> ::=

<XRS [xrs_id = (id) ]>

{<!-- Role Definitions>}+

</XRS>

<!-- Role Definitions> ::=

<Roles>

<Rolerole_id = (id)

<RoleName> (role name)> <RoleName>

[<!--{En|Dis}abling Constraint>]

[<!--[De]Activation Constraint>]

{<SSDRoleSetID> (id) </SSDRoleSetID>}*

{<DSDRoleSetID> (id) </DSDRoleSetID>}*

{<Junior> (name) </Junior>}*

{<Senior> (name) </Senior>}*

[<Cardinality>(number)</Cardinality>]

</Role>

<Role> .. </Role>

..

<Roles>


An xml instance of xrs l.jpg
An XML instance of XRS doctor-on-night-duty)

<XRS>

<Roles >

<Role role_id = "R100">

<RoleName> Nurse </ RoleName >

<Senior> Eye_Doctor </ Senior>

<Cardinality> 8 </ Cardinality >

</Role>

<Role role_id = "R200">

<RoleName> Eye_Doctor </RoleName>

< DSDRoleSetID>DSD1</ DSDRoleSetID >

< Junior>Nurse</ Junior>

<Senior> Eye_Surgeon </Senior>

<Cardinality> 6 </Cardinality>

</Role>

</Roles>

</XRS >


Xps grammar l.jpg
XPS Grammar doctor-on-night-duty)

<!-- XML Permission Sheet> ::=

<XPS [xps_id = (id) ]>

{<!-- Permission Definitions>}+

</XPS>

<!-- Permission Definitions> ::=

<Permissionperm_id = id

[prop= (prop op)] >

<Objecttype=(type name) id=(id)/>

<Operation> (access op) </Operation>

</Permission>


An xml instance of xps l.jpg
An XML instance of XPS doctor-on-night-duty)

<XPS>

<Permission perm_id ="P1">

<Object type = “Schema” id = “XS101” />

<Operation> all</operation>

</Permission >

<Permission perm_id ="P2">

<Object type = “Instance” id = “XI100” />

<Operation> all</operation>

</Permission >

<Permission perm_id ="P3">

<Object type = “Element” id = “XE100” />

<Operation> navigate </operation>

</Permission >

</XPS>


Example of xuras l.jpg
Example of XURAS doctor-on-night-duty)

<XURAS>

<URA_id="URA1">

<RoleName> Eye_Doctor</ RoleName>

<Users>

<User user_id=“s1“ />

<User user_id=“s2“ />

</Users >

<CredConditions>

<CredCondition>

<CredType> Doctor </CredType>

<LogicalExpr op="AND">

<Predicate>

<operator>eq</operator>

<name_param>field</name_param>

<value_param> Eye </value_param>

</Predicate>

<Predicate>

<LogicalExpr op="OR">

<Predicate>

<operator> lt </operator>

<name_param> age </name_param>

<value_param> 60 </value_param>

</Predicate>

<Predicate>

<operator> gt </operator>

<name_param> level </name_param>

<value_param> 7 </value_param>

</Predicate>

</LogicalExpr>

</Predicate>

</LogicalExpr >

</CredCondition>

</CredConditions >

</URA>

</XURAS>


Example of xpras l.jpg
Example of XPRAS doctor-on-night-duty)

<XPRAS>

<PRA pra_id="PRA1">

<RoleName> Nurse </RoleName>

<Permissions>

<perm_id> P3 </perm_id>

</Permissions>

</PRA>

<PRA pra_id="PRA2">

<RoleName> Eye_Doctor </RoleName>

<Permissions>

<perm_id> P1 </perm_id>

<perm_id> P2 </perm_id>

</Permissions>

</PRA>

</XPRAS>


X rbac system architecture l.jpg
X-RBAC System Architecture doctor-on-night-duty)

Document Composition Module

X-RBAC Module

UR ,PR DataSet

{TRIG DataSet}

Policy

Loader

XML

Policy Base

Policy

Validation Module

XML Parser

RBAC

Module

Authorization

XML/SOAP

Access

Request

XML

Sessions

Log

Sessions

DataSet

Legend:

DOM

XML/SOAP

Data Item

Functional

Module

XML Processor

RBAC Processor


On going work l.jpg
On-going Work doctor-on-night-duty)

  • Extension of the constraint language

    • Constraints on the set of roles a user can activate

  • Obbligations & Duties

  • Development of graphical tools for TRBAC administration

  • Testing on an Healthcare information system


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