Conditions vs. Relationships: Choosing Between ABAC and ReBAC

Ensuring secure access to sensitive information is a critical endeavor. We all know that our applications require strong authorization to function securely, but how to model and implement it is a much less straightforward question.

Two advanced models that have gained prominence for their fine-grained control capabilities are Attribute-Based Access Control (ABAC) and Relationship-Based Access Control (ReBAC).

ABAC and ReBAC represent significant advancements in access control, each offering unique approaches to managing permissions.

In short, ABAC focuses on using various attributes to define who can access what, while ReBAC leverages the relationships between entities to determine access rights. Both models address the limitations of traditional access control systems, providing more nuanced and flexible solutions.

This article is based on one of our latest livestreams which featured David Brossard (CTO @ Axiomatics), Alexandre Babeanu (CTO @3Edges), and our very own Gabriel Manor (Director of DevRel @Permit.io). The discussion explored advanced authorization models, the differences between ABAC and ReBAC, and the intricacies of fine-grained authorization.

You can watch the full live stream here:

⁠In this article, we will examine the details of ABAC and ReBAC, uncover each model's strengths and considerations, and offer insights into making an informed choice that aligns with your development goals.

Let’s get into it!

Evolution of Access Control Models: ACLs to Fine-Grained Authorization

Fine-grained authorization is not a new idea, but it has gained substantial attention in recent years. Initially, Access Control Lists (ACLs) were used to specify individual user permissions, which allowed for precise control but was challenging to manage at scale.

This was because increasing distribution and ever-growing amounts of data made ACLs almost impossible to distribute, maintain, or compute. While it might be possible to find a model that can centralize and distribute them properly, maintaining it in a modern application becomes impossible.

To address this, Role-Based Access Control (RBAC) was introduced, simplifying management by associating permissions with roles rather than individual users. However, RBAC often resulted in coarse-grained control, losing the specificity required in many scenarios.

The limitations of RBAC paved the way for more sophisticated models like ABAC and ReBAC. These models enable fine-grained authorization by considering additional dimensions, such as user attributes and relationships between entities.

The Role of ABAC and ReBAC in Modern Access Control

Fine-grained authorization has become increasingly important in applications today, particularly with the rise of cloud computing, microservices, and the need for secure data sharing across diverse platforms. ABAC and ReBAC offer solutions to these challenges by allowing access decisions to be based on multiple attributes or relationships, providing a higher degree of precision and control.

As we delve deeper into the specifics of ABAC and ReBAC, understanding their underlying principles and how they evolved from earlier models will provide a foundation for appreciating their strengths and weaknesses.

ABAC Vs. ReBAC: Pros and Cons

When choosing between Attribute-Based Access Control (ABAC) and Relationship-Based Access Control (ReBAC), it is essential to understand their core differences, benefits, and potential drawbacks:

1. Granularity and Flexibility

ABAC: Granularity Through Attributes and Conditions
ABAC relies on attributes associated with users, resources, actions, and contexts. It allows for highly granular control by defining policies that consider various attributes. For instance, access can be granted based on resource types, time/location of access, or other relevant attributes. This model excels in scenarios where conditions and attributes are well-defined and stable. Take a banking application with a policy like: “A user can only send a transfer of over £1000 if they have had their account for more than 1 year." The sum of the transfer and the length of time the user's account has been active require considering attributes as part of the authorization policy.

ReBAC: Granularity Through Relationships and Graph Structures
ReBAC, on the other hand, focuses on the relationships between entities. It leverages graph structures to model these relationships, making it inherently suitable for complex, interconnected, and hierarchical systems. Access decisions are made based on the traversal of these relationships, enabling fine-grained control in scenarios where interactions between entities are dynamic and multifaceted. ReBAC is particularly advantageous for applications involving a hierarchical network of users or resources, organizational hierarchies, or collaborative environments where relationships play a crucial role.

2. Ease of Implementation

ABAC: Policy as Code, Familiarity for Developers
ABAC policies are often implemented as code, which can be more accessible for developers familiar with coding practices. Tools and languages such as OPA’s Rego or AWS’ Cedar provide frameworks for defining and enforcing ABAC policies. This approach allows developers to leverage their existing skills and integrate ABAC into the development lifecycle. However, the complexity of managing numerous attributes and policies can become a challenge, especially in large-scale deployments.

ReBAC: Visual Representation, Existing Graph Tools
ReBAC benefits from its visual nature, as graph structures are intuitive and easier to understand. Existing graph tools like SpiceDB and Neo4j provide robust platforms for implementing ReBAC. These tools allow for straightforward visualization and manipulation of relationships, making it easier to design and manage access control policies. The primary challenge lies in understanding graph theory and the potential complexity of modeling relationships accurately.

3. Complexity and Scalability

Managing Large Numbers of Roles and Attributes in ABAC
One of ABAC's primary challenges is the potential for policy complexity. As the number of attributes and conditions increases, managing and maintaining these policies can become really difficult. Attribute-based policies may also lead to "attribute explosion" (just like RBAC’s role explosion), where the sheer number of attributes and their combinations can overwhelm the system. Effective policy management and governance practices are essential to mitigate this complexity.

Managing Complex Relationships in ReBAC
ReBAC excels in managing complex relationships, but it requires a solid understanding of graph theory and the specific tools used. The scalability of ReBAC depends on the efficiency of the graph database and the algorithms used for traversal and access decision-making. While ReBAC can handle intricate relationship models, ensuring performance and scalability in large, dynamic environments can be challenging.

ABAC vs. ReBAC: Decision-Making Factors

Choosing between Attribute-Based Access Control (ABAC) and Relationship-Based Access Control (ReBAC) involves carefully considering various factors that align with your development needs and capabilities. This section outlines key decision-making criteria and provides a framework to help developers select the right model.

Key Factors to Consider

1. Nature of the Use Case

• User-Centric vs. Relational Needs
  : Determine whether your primary need is to control access based on user attributes (ABAC) or the relationships between entities (ReBAC).
  
  • ABAC is ideal for scenarios where user roles, permissions, and attributes are clearly defined and relatively static. It works well in environments like healthcare and finance, where access decisions often hinge on specific attributes such as job roles, clearance levels, and departmental affiliations.
  • ReBAC excels in environments where the relationships between entities are dynamic and central to the application. Social networks, collaborative platforms, and organizational structures with complex hierarchies are prime examples where ReBAC's flexibility and relationship-focused approach provide significant benefits.

2. Existing Infrastructure and Tools

• Assess the current technological infrastructure and toolsets within your development environment.
  
  • ABAC: Developers already using policy-as-code frameworks and familiar with coding practices may find ABAC easier to implement. Established tools like OPA provide great support for defining and managing ABAC policies.
  • ReBAC: Those with experience in graph databases and graph theory might prefer ReBAC. Existing graph tools like Neo4j and ready-made Zanzibar graphs such as OpenFGA and SpiceDB offer powerful capabilities for implementing and scaling ReBAC solutions.

3. Regulatory and Compliance Requirements

• Evaluate your industry’s specific compliance requirements and how each model can facilitate adherence to these standards.
  
  • ABAC: Offers detailed audit logs and compliance reporting based on attribute conditions.
  • ReBAC: Provides visibility into relationship-based access decisions, which can also aid in compliance, especially in environments where relationships and interactions are heavily scrutinized.

4. Developer and Business User Expertise

• Consider the expertise and skills of your development and business teams.
  
  • ABAC: Requires coding expertise and robust policy management practices. It’s easier for developers who are familiar with defining and managing complex policies through code.
  • ReBAC: Demands an understanding of graph structures and the ability to model relationships effectively. It may require additional training or hiring of skilled personnel.

5. Scalability and Performance

• Analyze the potential for growth and the performance demands of your system.
  
  • ABAC: Managing numerous attributes and policies can become complex, potentially impacting performance. Effective policy management and governance practices are essential.
  • ReBAC: Ensuring performance and scalability in large, dynamic environments can be challenging. The efficiency of the graph database and traversal algorithms are crucial factors to consider.

ABAC vs. ReBAC: The bottom line

The choice between ABAC and ReBAC is not simply a matter of preference but one of strategic alignment with your development needs and capabilities. Both models have their unique advantages and are capable of providing fine-grained access control to enhance security and compliance.

That being said, it's important to note that authorization models are more thinking tools than concrete guidelines, and most applications end up mixing between them. The most important thing is how you design them so that they're flexible and scalable and continue to evolve along with your application's needs.

Setting up and managing complex authorization frameworks like RBAC, ABAC, or ReBAC can pose a challenge for developers and other stakeholders, potentially leading to bottlenecks. As application requirements change, transitioning away from basic authorization methods can cause delays that might take months to resolve. Furthermore, the work doesn't end at implementation. Creating additional roles, attributes, and policies involves complex R&D work and steep learning curves.

But there is no reason to limit yourself to limit yourself to a single model. Implementing and managing your RBAC, ABAC, or ReBAC policies using an authorization service like Permit.io allows for a flexible transition between authorization models and provides a simple API and no-code UI that makes permission management accessible to all stakeholders.

Permit’s UI enables developers to define the required roles, attributes, and role derivation logic, generate code, and push updates or changes to applications in real time. This ensures that everyone is included in the permission management process, preventing developers from becoming bottlenecks.

By providing a flexible and scalable solution, Permit allows your authorization framework to evolve with your application’s needs, ensuring robust security and efficient permission management over time.

Conclusion

We hope you can make an informed decision that will safeguard your application by thoroughly evaluating your requirements and considering the insights provided in this article. No matter which model you choose and how you decide to implement it, the key is to ensure that it is implemented thoughtfully, managed effectively, and continuously refined to meet evolving challenges.

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