ReBAC vs RBAC: What's the difference and which should you choose?

Imagine you're building the next Dropbox or Figma. Your users need to share files and collaborate, but you also need to ensure people can only access what they're supposed to.

Two common approaches for access control are Role-Based Access Control (RBAC) and its more modern cousin, Relationship-Based Access Control (ReBAC).

Traditional RBAC works like job titles: you're either an "admin," "editor," or "viewer." It's simple but rigid.

ReBAC, on the other hand, works more like a social network, understanding connections like "member of this project" or "owner of this document." In this article, we'll compare these approaches.

Understanding RBAC

RBAC associates permissions with roles, which are then assigned to users. Instead of managing individual permissions, administrators assign users to predefined roles that carry specific access rights.

Real-World Example: AWS IAM

AWS Identity and Access Management (IAM) provides a clear example of RBAC in practice. Consider these common scenarios:

AWS Administrator role

{
   "Version": "2012-10-17",
   "Statement": [
       {
           "Effect": "Allow",
           "Action": "*", 
           "Resource": "*"
       }
   ]
}

AWS Read-only role

{ 
    "Version": "2012-10-17", 
    "Statement": [ 
        { 
            "Effect": "Allow", 
            "Action": [ "s3:Get*", "s3:List*" ], 
            "Resource": "*" 
        } 
    ]
}

In this example, rather than assigning individual permissions to each DevOps engineer or developer, AWS lets you create roles like "Administrator" or "Read-only".

When new team members join, they're simply assigned to the appropriate role. If a developer needs temporary admin access, they can be granted that role temporarily without modifying individual permissions.

Key Benefits of RBAC:

• Simplified Management: When employees change positions, they simply receive new role assignments
• Efficient Scaling: Adding new employees requires only role assignment, not individual permission configuration
• Enhanced Security: Predefined roles reduce permission assignment errors
• Audit Friendly: Evaluating permissions by role simplifies compliance checks

RBAC Limitations:

• Static Nature: Struggles with dynamic or overlapping responsibilities
• Over-Provisioning Risk: Complex scenarios may lead to granting excessive permissions
• Limited Context: Cannot consider factors like location or time in access decisions
• Exception Handling: Difficulty managing temporary or special access needs

Understanding ReBAC

Relationship-Based Access Control (ReBAC) represents a more flexible approach to access management. As its name suggests, ReBAC determines access by evaluating the relationships between entities in your system - users, resources, teams, and more. A popular example of a ReBAC system is Google Zanzibar.

‍This relationship-based approach is more flexible because it mirrors how permissions work in real-world organizations: access is often determined by how people and resources are connected, not just by job titles.For example, in a document management system:

• A team leader gets access to all documents owned by their team members
• Project collaborators automatically gain access to project resources
• Department managers see all reports within their department's hierarchy

These dynamic relationships are difficult to model with traditional roles but come naturally with ReBAC.

Example: Project Management System

User (Alice) -> OWNS -> Project Folder
Project Folder -> HAS_MEMBER -> Marketing Team
Marketing Team -> INCLUDES -> Bob

Therefore: Bob has access to Project Folder

Key Benefits of ReBAC:

• Dynamic Access: Automatically adjusts as relationships change
• Contextual Control: Considers real-world connections and hierarchies
• Natural Modeling: Reflects actual organizational structures
• Flexible Permissions: Supports both direct and indirect relationships

ReBAC Challenges:

• Performance Impact: Relationship evaluation can be resource-intensive
• Implementation Complexity: Requires careful relationship modeling
• Maintenance Overhead: More complex to maintain as relationships grow

Choosing Between RBAC and ReBAC

Use RBAC When:

• Your organization has well-defined, stable roles
• Access patterns are primarily based on job functions
• You need straightforward audit trails
• Performance is a critical concern

Use ReBAC When:

• Access depends on dynamic relationships
• You need contextual access decisions
• Your system models social or organizational graphs
• Flexibility is more important than simplicity

Consider Both When:

• You have both static and dynamic access needs
• Different parts of your system require different approaches
• You're building a system that will scale in complexity over time

Implementation Considerations

When implementing either model:

1. Start with clear access requirements
2. Map out your organization's structure and workflows
3. Consider future scaling needs
4. Plan for performance and maintenance requirements
5. Document your access control policies

Remember that these models aren't mutually exclusive - many systems successfully combine RBAC's simplicity for basic access control with ReBAC's flexibility for more complex scenarios.

Conclusion

While RBAC offers simplicity and efficiency for organizations with clear role definitions, ReBAC provides the flexibility needed for dynamic, relationship-driven environments. Consider your specific needs, organizational structure, and growth plans when choosing between them – or implement both for comprehensive access control.

Getting Started

Implementing ReBAC or RBAC doesn't mean starting from scratch. Several platforms provide robust access control solutions. For example, WorkOS Fine Grained Authorization (FGA) offers a production-ready ReBAC implementation that can handle complex authorization needs while maintaining performance. Sign up for WorkOS today and start selling to enterprise customers tomorrow.