How RBAC Works: The Fundamentals of Role-Based Access Control

Role-Based Access Control (RBAC) is an access management model in which users do not receive permissions directly. Instead, permissions are granted to roles — predefined collections of privileges that reflect job responsibilities — and users are then assigned to those roles.

This abstraction lets organizations manage access by function (e.g., "data analyst") rather than by individual, making permissioning scalable, auditable, and aligned with organizational structure.

A helpful analogy is a corporate badge system: you don’t customize door access for every employee. Instead, someone in HR gets the “HR badge,” which grants access to rooms and systems relevant to their role.

 

 

Concept	Description
Object	Resource being protected (e.g., a table or schema)
Action	Operation performed on the object (e.g., SELECT)
Privilege	Specific permission = (Object, Action)
Role	Named collection of privileges
User Identity	Authenticated subject requesting access
Session	User’s runtime context with active roles
Role Assignment	Maps users to roles
Grant/Revoke	Commands to manage access relationships

StarRocks, a high-performance analytical database, implements RBAC to manage access control. Roles can be defined with specific permissions, and users can be assigned to these roles. For example:

This setup allows for efficient and secure management of user permissions, ensuring that users only have the access necessary to perform their job functions.

StarRocks provides several predefined roles that can be used to meet common administrative needs, such as:

To adhere to the principle of least privilege, roles can be assigned as default roles, which are not activated upon login unless explicitly set by the user. For example, a user with role_query and role_delete roles might have only role_query activated by default to prevent accidental data deletion. Users can manually activate other roles as needed within their session.

Let’s walk through each model in detail, complete with definitions, structure, practical examples, and use cases.

RBAC0: Core RBAC

 

Definition

The most fundamental RBAC model. RBAC0 defines the basic entities and relationships:

• Users (U): Authenticated individuals.

• Roles (R): Named collections of permissions.

• Permissions (P): Allowed actions on objects (e.g., SELECT on table_sales).

• Sessions (S): Execution contexts in which a user activates one or more roles.

Users are assigned roles. Roles are assigned permissions. When a user starts a session, they activate a subset of their assigned roles.

Formal Relationships

• UA ⊆ U × R → user-to-role assignment

• PA ⊆ P × R → permission-to-role assignment

• Sessions: s ∈ S, with mappings user(s): U and roles(s) ⊆ R

Example

Imagine an analytics system with three roles:

• read_only: SELECT permission on analytics views

• editor: SELECT, INSERT, UPDATE on staging tables

• admin: full access (CREATE, ALTER, DROP) on all schemas

A user named Alice is assigned read_only and editor. During most sessions, she activates only read_only, but during ETL work, she manually activates editor.

Use Case

• Small teams or early-stage systems with well-understood roles.

• Explicit permissions but no complex organizational hierarchy.

• Startup engineering teams, internal dashboards, or sandbox environments.

Limitations

• No support for role inheritance or organizational policy enforcement.

• Redundancy: Shared permissions must be redefined in every role.

RBAC1: Hierarchical RBAC

 

Definition

Extends RBAC0 by allowing roles to inherit from one another, forming a role hierarchy. This supports real-world organizational structures and minimizes redundancy.

• Roles form a partial order: if role_A ≥ role_B, then role_A inherits all permissions of role_B.

• Inheritance can be single-parent (tree) or multi-parent (DAG).

Example

In a retail system:

• cashier: can SELECT and INSERT transactions.

• supervisor: inherits from cashier, adds UPDATE and DELETE.

• manager: inherits from supervisor, adds access to inventory and HR systems.

Assigning a user the manager role implicitly gives them all permissions of cashier and supervisor.

Use Case

• Enterprise environments with defined reporting structures.

• Reducing duplication: shared access is assigned at the lowest appropriate role.

• Examples: support_agent < support_lead < support_admin

Advantages

• Promotes modularity and reuse.

• Easier to maintain: Modify permissions in one base role, and all inheriting roles benefit.

Limitations

• Still lacks policy enforcement (no separation of duties).

• Needs careful design to avoid unintended permission inheritance.

RBAC2: Constrained RBAC

 

Definition

Extends RBAC0 by introducing constraints—rules that restrict how users, roles, and permissions can be assigned or activated. These constraints enforce security policies such as Separation of Duties (SoD).

Types of Constraints

1. Static Separation of Duties (SSD):

   • Users cannot be assigned to conflicting roles.

   • Example: A user cannot be both invoice_creator and invoice_approver.

2. Dynamic Separation of Duties (DSD):

   • Users may be assigned conflicting roles, but only one can be active per session.

   • Example: A user can hold both deployment_engineer and review_engineer roles but cannot activate both at once.

3. Cardinality Constraints:

   • Limit how many users can hold a specific role.

   • Example: Only 1 chief_security_officer.

4. Prerequisite Roles:

   • A user must hold one role to qualify for another.

   • Example: Must hold senior_analyst before being granted data_validator.

Example

In a bank:

• loan_officer: Can initiate loan applications.

• auditor: Can review applications.

• Constraint: A user cannot have both roles simultaneously (SSD), to prevent fraud.

Use Case

• Regulated industries: Finance, healthcare, government.

• Ensuring compliance with internal control frameworks (e.g., SOX, HIPAA).

• Scenarios requiring explicit conflict prevention.

Advantages

• Implements business rules within the access control layer.

• Helps mitigate internal threats and conflict of interest.

Limitations

• Constraints can introduce complex administrative overhead.

• May require additional tooling or policy management systems.

RBAC3: Symmetric RBAC (Combined Model)

 

Definition

RBAC3 combines the features of RBAC1 and RBAC2 — it supports both role hierarchies and constraints. It is the most complete and expressive model.

This model allows you to:

• Structure roles hierarchically for inheritance and reuse.

• Enforce organizational policies via constraints.

Example

In a multinational corporation:

• employee < team_lead < regional_manager < vp_operations

• A user may hold both procurement_officer and compliance_checker, but a DSD constraint prevents activating both roles in a session.

• SSD constraint: No user can be both budget_approver and expense_submitter.

Use Case

• Complex, large-scale organizations with layered management and strong compliance requirements.

• Federated access environments (e.g., multi-region or multi-tenant data platforms).

• Examples: global banks, health institutions, defense contractors.

Advantages

• Full expressiveness: everything from RBAC0 to RBAC2, plus structured delegation.

• Allows scalable governance in dynamic environments.

Limitations

• More challenging to implement and maintain.

• Requires disciplined design and potentially policy-as-code integration.

Comparison Summary

RBAC0 is sufficient for basic systems where roles are few and straightforward. RBAC1 scales those systems by mimicking organizational hierarchy. RBAC2 adds essential security governance. RBAC3 gives you the full toolkit: structured roles + enforceable policies — ideal for environments where access control is both critical and complex.

RBAC systems operate on three foundational rules that govern how roles and permissions interact with users and system operations. These are not optional best practices — they’re core principles that define the logic of any RBAC-compliant implementation.

1. Role Assignment Rule

Rule:
A user (subject) can perform a system operation only if the user has been assigned a role.

Explanation:
This rule enforces indirect permissioning — access is never granted to users directly but only via roles. It ensures that access is mediated and structured through organizational constructs (roles), rather than being hard-coded or ad hoc.

Implication:

• Users must first be granted at least one role before they can do anything beyond authentication.

• Reduces management complexity by abstracting permission logic into role definitions.

Example:
Alice cannot SELECT from sales_data unless she has a role (e.g., analyst) that includes that privilege. She cannot activate the role if it hasn't been assigned to her.

2. Role Authorization Rule

Rule:
A user’s active role must be authorized for that user.

Explanation:
Even if a user is assigned a role, they must explicitly activate it within a session to use its privileges. This rule ensures users can only activate roles they are authorized for, not any arbitrary role in the system.

Implication:

• Adds a layer of control during session startup or role switching.

• Allows for role scoping, where users can be assigned multiple roles but only activate a safe subset by default.

Example:
Bob has both readonly_user and admin_editor roles, but only readonly_user is authorized as a default role. He must explicitly issue a command (e.g., SET ROLE admin_editor) to activate the more powerful one — assuming he’s permitted to.

3. Permission Authorization Rule

Rule:
A user can execute an operation only if that operation is permitted by one of the user’s active roles.

Explanation:
This is the actual enforcement point. When a user issues a command, the system checks whether the action-object pair (e.g., DELETE on transactions) is included in the set of privileges granted to any of the active roles.

Implication:

• Reinforces the least privilege principle: only active roles influence access.

• Even if a user has powerful roles, those powers don’t exist in a session unless activated.

Example:
Carol is assigned the role data_admin, which includes DROP TABLE privilege. But if she only activates her read_only role during a session, she cannot drop tables — even though she has the broader permission in theory.

Summary Table

Together, these rules ensure that RBAC systems are layered, auditable, and deterministic — with access governed by organizational structure, not individual exceptions.

RBAC offers elegant abstractions, but designing and maintaining a real-world RBAC system is challenging — especially at scale or in dynamic, cross-functional environments.

Here’s why:

1. Role Explosion

 

Description:

As business needs grow, so does the number of roles. Every slight variation in permission (e.g., read access to one table but write access to another) can justify a new role. This leads to:

• Dozens or hundreds of similar-but-different roles

• Inconsistent naming conventions

• Duplicate privileges across roles

Consequence:

• Admins lose track of which role does what.

• Harder to audit, refactor, or deprecate roles.

• New users are harder to onboard correctly.

Example:

A SaaS platform starts with analyst, engineer, and admin roles. Over time, exceptions lead to roles like analyst_us_east, analyst_eu_gdpr, analyst_gdpr_temp, etc.

2. Difficulty in Role Definition

 

Description:

Defining meaningful, non-overlapping roles requires a deep understanding of organizational workflows and access patterns. It’s not enough to ask, “What do engineers need?” — you must understand how their needs differ, across teams and contexts.

Common Pitfalls:

• Roles too broad → everyone gets more access than needed.

• Roles too narrow → users need multiple roles to function, defeating clarity.

• Roles defined by convenience, not by principle.

Example:

A data_scientist role might sound clear until you realize some only explore data, while others need to deploy pipelines — which involve entirely different privileges.

3. Maintenance Burden

 

Description:

RBAC systems are not static. As users change jobs, teams evolve, projects end, and data models change, role definitions must evolve too.

Maintenance tasks:

• Revoking old role assignments

• Refactoring overly broad roles

• Updating role privileges after schema changes

• Auditing unused roles

Risk:

Failure to maintain RBAC leads to privilege creep — where users accumulate permissions they no longer need, violating the principle of least privilege.

4. Onboarding and Offboarding Complexity

 

Description:

Proper role assignment is crucial when new users join — and equally important when users leave or change departments.

Common Errors:

• Overprovisioning access "just to get started"

• Forgetting to revoke roles during offboarding

• Copy-pasting another user’s roles without evaluating need

Example:

A departing engineer moves to marketing. If their old engineering roles aren’t removed, they may retain deploy or schema-altering capabilities.

5. Scalability Challenges

 

Description:

As the number of users, roles, and privileges grows into the thousands or more, performance and usability suffer:

• Role lookups slow down

• Audits become harder

• Visualization of permissions becomes infeasible without tooling

Solution:

• Implement policy automation

• Enforce naming standards and inheritance trees

• Use analytics to detect role usage anomalies

6. Business vs. Technical Misalignment

 

Description:

RBAC must reflect business functions, but is often designed by technical staff. If roles don’t map cleanly to real-world responsibilities, they either:

• Fail to enforce correct boundaries

• Or become a bottleneck due to excessive restriction

Example:

Marketing team needs access to campaign_metrics, but DBAs create a readonly_all_tables role. Now marketing can see sensitive internal logs too — a mismatch.

Summary: Why RBAC Is Hard

Allow access if user.department = 'engineering' and resource.sensitivity = 'low'

Aspect	RBAC	ABAC
Granularity	Medium (role-level)	High (condition-based)
Scalability	High	Medium (depends on policy engine)
Auditing	Easier (role logs)	Harder (policy traces)
Best For	Role-centric organizations	Attribute-rich, dynamic environments

Aspect	IBAC	RBAC
User-Specific Control	Very High	Medium
Scalability	Poor	High
Policy Reuse	None	Strong (via roles)
Best For	Small setups or edge cases	Growing orgs or formal structures

Model	Best When You Need...
RBAC	Clear role mapping, scalable governance, auditability
ABAC	Dynamic, context-aware decisions; fine-grained control
IBAC	Simplicity for few users; unique access patterns
LDAP	Centralized identity source; user directory integration