NIST Standard for Role-Based Access Control Present by Wenyi Ni

The root of RBAC The use of groups in UNIX and other operating systems Privilege grouping in DBMS Separation of duty concepts RBAC embodies these notions in a single access control model.

RBAC includes: Roles and role hierarchies Role activation Constraints on user/role membership and role set activation

RBAC is organized into two part RBAC reference model RBAC Functional Specification

RBAC reference model Define a common vocabulary of terms for in consistently specifying requirements and to set the scope of the RBAC features included in the standard

RBAC Functional Specification Define requirements over administrative operations for the creation and maintenance of RBAC element sets and relations

NIST RBAC model is defined in terms of four model components Core RBAC Hierarchical RBAC Static separation of duty relations Dynamic Separation of duty relations

Core RBAC Define a minimum collection of RBAC elements, element sets, relations in order to completely achieved a role-based access control system It includes: 1.user-role assignment 2.permission-role assignment

Definitions in core RBAC User: defined as a human being. It can be extended to include machine, network,intelligent autonomous agent Role: a job function within the context of an organization with some associated semantics regarding the authority and responsibility

Definition (continued) Permission: an approval to perform an operation on one or more RBAC protected objects Operation: an executable image of a program Session: a mapping between a user and an activated subset of roles that are assigned to the user

Core RBAC model element sets and relations

Hierarchal RBAC It adds relations for supporting role hierarchies Senior roles acquire the permissions of their juniors A role’s set of authorized users and authorized permission Role hierarchy can be 1)tree 2)inverted tree 3)lattice

Role hierarchy Tree

Role hierarchy inverted tree

Role hierarchy lattice

Example: accounting roles

Separation of duty relations It is used to enforce conflict of interest policies that organizations may employ to prevent users from exceeding a reasonable level of authority for their position

Static Separation of Duty Relations Enforce constraints on the assignment of users to roles Place restrictions on sets of roles. If a user is assigned to one role, the user is prohibited from being a member of a second role.

Because of the conflict of role ‘billing’ and ‘Cashier’ , Frank is prohibited to be assigned both of them

Dynamic Separation of Duty Relations Place constraints on the roles that can be activated within or across a users sessions. It supports each user has different levels of permission at different time. It is often referred as timely revocation of trust

Categories of functions in RBAC Used to meet the requirements for each of the components 1.Administrative Functions 2.Supporting System Functions 3.Review Functions

Administrative Functions in core RBAC Create and maintain element sets(users,roles,OPS,OBS) 1.AddUser, DeleteUser 2.AddRole, DeleteRole 3.AssignUser, DeassignUser 4.GrantPermission, revokePermission

Supporting System Function in Core RBAC Session management and make access control decisions 1.CreateSession 2.AddActiveRole, DropActiveRole 3.CheckAccess

Review Function in Core RBAC View the contents of user-to-role and permission-to-role assignment. 1.AssignedRoles 2.RolePermissions 3.UserPermissions 4.SessionPermisssions 5.RoleOperationsOnObjects 6.UserOperationsOnObjects

Administrative Function in Hierarchical RBAC Create and maintain the partial order relation among roles 1.AddInheritance, DeleteInheritance 2.AddAscendant, AddDescendant

Supporting System Functions in Hierarchical RBAC Same function as for Core RBAC, some function need to be redefined because of the role hierarchy. Such as: createSession, addActiveRole.

Review Functions in Hierarchical RBAC All review functions specified for Core RBAC is valid here Add the review functions to inherited roles. 1.AuthorizedUsers 2.AuthorizedRoles

Functions in SSD Administrative: 1CreatSSDSet,DeleteSSDSet 2AddSSDRoleMember, DeleteSSDRolemember 3.SetSSDRoleMember 4.SetSSDCardinality Supporting System: same as those for core RBAC Review: 1.SSDRoleSets 2.SSDRoleSetRoles 3.SSDRoleSetCardinality

Functions in DSD Administrative 1.CreateDSDSet, DeleteDSDSet 2.AddDSDRoleMember,DeleteDSDRoleMember 3.SetDSDCardinality Suport System: 1.CreateSession 2.AddActiveRole 3.DropActiveRole Review: 1.DSDRoleSets 2.DSDRoleSetRoles 3.DSDRoleSetCardinality

Conclusion RBAC is used to simplify security policy administration RBAC is an open-ended technology,which ranges from very simple to fairly sophisticated. RBAC continues to be an evolving technology.

End Reference: http://csrc.nist.gov/rbac/rbacSTD-ACM.pdf