Role-Based Access Control (RBAC)

The access control is based on the role of the subject in the system and the rules that are defined for that role.

• In organizations, the permissions of the people are defined by their role in the organization;
• The role permissions change less frequently than the permissions of the people;

RBAC Family

There are four models in the RBAC family:

They serve as reference for the implementation of RBAC in the systems.

RBAC0

• A user can have multiple roles and a role can be assigned to multiple users;
• A session is a set of roles that a user has at a given time;
• The permissions are always positive.

Definitions

• U, R, P and S - sets of users, roles, permissions and sessions, respectively;
• UA ⊆ U × R - set of user-role assignments;
• PA ⊆ R × P - set of role-permission assignments;
• user: S -> U - function that returns the user of a session;
• roles: S -> 2^R - function that returns the roles of a session;
• roles(si) ⊆ {r ∈ R | (user(si), r) ∈ UA} - function that returns the roles of a session;

RBAC1

The RBAC1 model is a RBAC0 model with hierarchical roles:

• The user inherits the permissions of the role and the permissions of the parent roles of the role that the user has;

Definitions

• RH ⊆ R × R - set of role hierarchy;
• roles: S -> 2^R - function that returns the roles of a session;
• roles(si) ⊆ {r ∈ R | ( ∃ r’ ≥ r) [(user(si), r’) ∈ UA]} - function that returns the roles of a session;

RBAC2

The RBAC2 model is a RBAC1 model with constraints:

• Constraints are rules that restrict the permissions of the roles;
• Represented by predicates, returning allowed or denied;
• Examples of constraints:
  • Separation of duties;
  • Cardinality constraints;
  • Pre-conditions.

RBAC3

The RBAC3 model combines the RBAC1 and RBAC2 models, so it has hierarchical roles and constraints.