RBAC vs. ACL: what's the difference and how do they work together?

You've likely heard of RBAC and ACL for managing access, but do you know the key differences and how they work together? 

In this article, we'll discuss RBAC and ACL to understand their differences, their uses, and whether you need one or both.

RBAC vs. ACL: a quick comparison

Role-based access control (RBAC) groups permissions into the roles within a system or organization. You have different job roles like manager, developer, or accountant. Each role is then granted access and permissions based on their responsibilities. Use it if you want to organize broad levels of access by job roles or responsibilities.

An Access Control List (ACL) is a list that specifies which users or system processes are granted access to objects, as well as what operations are allowed on given objects. Use it if you need precise, granular control of permissions down to the individual user or resource level.

Many organizations actually use RBAC and ACLs in complementary ways. RBAC handles the broader roles while ACLs fine-tune access as needed.

What is RBAC?

RBAC is a model where permissions are associated with roles, and users are assigned to roles. So rather than giving individual users certain rights, roles are created that define what a user can or can't do. Users are then assigned one or more roles depending on their job responsibilities.

Here’s how it works. First, admins define roles with specific permissions. These could be roles like "Manager," "Developer," or "HR Specialist." Then, users are assigned to those predefined roles. Their individual access is determined by the roles they belong to.

RBAC provides a centralized way to manage user permissions across systems. It’s easier to manage than ACLs, especially in large organizations with many users and permissions. It also scales well in complex environments by reducing the number of individual permission assignments.

However, it lacks the fine-grained control available with ACLs, as permissions are generalized within roles. To meet specific access requirements, organizations may need to create many roles, leading to role explosion. Over time, managing and maintaining this large number of roles can become as complex as managing individual permissions directly.

Implementing RBAC requires planning out roles, permissions, and processes. Start by analyzing your workforce's roles and responsibilities. Define roles based on job functions, map out appropriate access levels, and assign users accordingly.

RBAC is widely used in organizations to manage access to business applications, databases, and network resources.

What are ACLs?

Access control lists (ACLs) define the permissions or access rights for specific users or groups to access resources like files, directories, or network services.

ACLs work by maintaining a list of access control entries (ACEs) that specify the permissions granted or denied for each user or group. 

For example, an ACE might allow user "Alice" read-only access to a file while denying user "Bob" any access whatsoever. These rules are evaluated whenever a subject (user) tries to perform an operation on an object (resource).

One major advantage of ACLs is their granularity — you can define extremely specific rules tailored to your organization's needs. Do you want to let the marketing team edit a document but prevent them from deleting it? No problem! ACLs let you control access down to the file/folder level for different user populations.

While powerful, ACLs can become incredibly complex and difficult to manage. As an organization expands, the number of users, groups, and resources increases, exponentially growing the number of potential ACEs. Keeping track of permissions across numerous resources and users can become overwhelming. 

Moreover, conflicts between ACEs (e.g., one entry allowing access and another denying it for the same user) can complicate the enforcement of security policies.

Consider a company with 1,000 employees, each requiring access to various files, directories, and network resources. If each resource has a detailed ACL with specific permissions for different users and groups, the number of ACEs can quickly escalate into the tens of thousands. 

Managing such a vast and intricate set of permissions manually can lead to:

• Increased administrative effort: Significant time and resources are required to manage and update the ACLs.
• Higher likelihood of errors: The complexity increases the chances of mistakes, such as granting incorrect permissions or failing to revoke access when needed.
• Difficulty in ensuring compliance: Ensuring that all permissions comply with security policies and regulatory requirements becomes challenging.

That’s why in most cases, ACLs will be used as a supplementary access control method.

ACLs are used extensively in file systems (NTFS, ext3), databases, cloud services like AWS, firewalls, routers, and more to protect resources from unauthorized access.

When to use RBAC, ACLs, or both

Use RBAC:

• When managing access for a large number of users across various departments and roles.
• When you need consistent access permissions across users with similar job functions.

Use ACL:

• When you need very specific and detailed access control at the individual resource level.
• In smaller systems where the complexity of managing ACLs is manageable.
• When permissions need to be customized for individual users or specific scenarios.

Use both RBAC and ACL:

• When you have a mix of broad role-based permissions and the need for fine-grained control over specific resources.
• When implementing a multi-layered security approach where roles define general permissions, and ACLs provide additional control.

Are there other options to enable access control?

While RBAC and ACL are popular access control models, there are other options that enable access control. They include:

• Mandatory Access Control (MAC): With MAC, access rights aren't assigned to specific users or roles. Instead, they're determined by system-level policies based on security labels or classifications. For example, a highly confidential file might be assigned a "top secret" label. The system policies would then restrict access to only users or processes with the proper clearance level. 
• Discretionary Access Control (DAC): DAC is an older access control method that gives complete control to the data owner. The owner decides which users or groups can access specific resources like files or folders. It's flexible but also riskier since permissions can easily get out of sync.
• Attribute-Based Access Control (ABAC): ABAC grants access based on attributes (user attributes, resource attributes, and environmental conditions). Policies are defined using these attributes to determine access rights. ABAC is commonly used in complex and dynamic environments such as healthcare systems, where access needs to be controlled based on a variety of factors (e.g., user role, time of day, location).
• Relationship-Based Access Control (ReBAC): ReBAC defines and enforces access permissions based on the relationships between entities (e.g., users and resources) within a system. It’s commonly used in social networks like Facebook or collaborative platforms like Google Drive.

Next steps

Before deciding on RBAC or ACLs, consider your specific needs, resources, and team size to determine if implementing one method, both, or additional options like ABAC makes the most sense for your company.

Once you’ve settled on an access control method or a combination, use WorkOS FGA to implement them. 

WorkOS FGA is an authorization model built for developers. With it, you can model access control systems like RBAC, ABAC, and ReBAC, or customize and build your own unique model. With easy-to-use APIs and SDKs for most programming languages, getting started is simple.

Start building with WorkOS.