RBAC vs ReBAC: Comparing Role-Based & Relationship-Based Access Control
The Authz Dilemma: Why Roles Aren’t Always Enough
Ever felt like your auth logic is just one giant “if” statement that’s about to explode?
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The Authz Dilemma: Why Roles Aren’t Always Enough
Ever felt like your auth logic is just one giant “if” statement that’s about to explode? We’ve all been there, trying to hack together permissions that actually make sense for the business.
Most of us start with simple rbac because, honestly, it’s easy to grok. You got an admin, an editor, and a viewer. But then the product team wants “nested folders” or “team-based sharing” in a healthcare app, and suddenly you’re drowning in role explosion.
The authn vs authz split: authentication is just checking the id badge at the door, but authorization (authz) is deciding if that person can actually touch the server rack.
Hierarchy headaches: In a b2b finance tool, a manager needs access to everything their team owns. Mapping that with static roles is a nightmare.
Fine-grained needs: Modern apps need to know how a user is related to a resource, not just what their job title is.
According to Permit.io, while rbac is simple to build, it’s “ineffective when managing access to hierarchical structures” where resources are nested.
So, if your roles feel like they’re bursting at the seams, it might be time to look at relationships. Before we get into the fancy stuff, lets do a deep dive into the standard model most of us use every day.
Understanding RBAC: The Industry Standard
Before we jump into the alternatives, we gotta understand the “old reliable” first. Most enterprise sso setups use rbac because mapping a person to a job title is just how most businesses think. (What is Enterprise Identity — And Why Most Companies Get SSO …) If you’re building a simple retail portal or a basic finance app, you probably don’t need to over-engineer things.
In a standard enterprise setup, you’re basically just bundling permissions into buckets.
The Admin: Can do everything—delete users, change api keys, the whole nine yards.
The Editor: Can mess with content in a healthcare portal but can’t touch billing.
The Viewer: Just there to look at the pretty charts.
It’s usually static. You define these roles once in your policy, and they don’t change much. According to Aserto, rbac is best when you have a “relatively static mapping” between users and resources. It’s easy to audit because you just look at a spreadsheet and see who has the “Manager” tag.
But here is where it gets messy. Imagine you’re running a b2b saas. Suddenly, a customer wants “Regional Manager” who can only see data for the “North Division.” Then they want a “Contractor” who only sees one specific folder.
If you keep using rbac for this, you end up with 500 roles like North_Division_Manager_Level_2. This is what the industry calls “role explosion.” It’s a nightmare for devops because the policy files become huge and impossible to manage. (Why is DevOps still such a fragmented, exhausting (and ofc costly …) As noted by Permit.io, this is exactly why rbac fails when things get hierarchical.
Next up, we’ll look at how rebac actually solves this by looking at how things are related instead of just what someone’s title is.
Relationship-Based Access Control (ReBAC) Explained
So, if rbac is the “blunt instrument” of the auth world, rebac is the scalpel. It stops looking at what a user is (like an admin) and starts looking at how they’re connected to the data they want to touch.
In a rebac model, you define access through resource-to-resource connections. This is huge for anything with a hierarchy, like a file system or a project management tool. Instead of manually assigning roles to every sub-item, permissions just… flow down.
The Parent-Child model: If you own a “Folder,” you automatically own the “Files” inside it. You don’t need a separate policy for each document; the relationship handles the heavy lifting.
Graph-based authz: This is the tech behind things like Google Zanzibar. It treats your entire permissions set as a giant web of nodes and edges.
Derived permissions: You can say “if someone is a member of the ‘Engineering Team’, and that team owns this ‘Repo’, then the user can write code.”
For those of us building multi-tenant saas, rebac is a lifesaver. You can handle complex org charts without your database melting. This prevents “role explosion” because you aren’t creating a new role for every single weird edge case.
In a healthcare app, for example, a doctor might need access to a patient’s records only if they are the “assigned_physician.” You don’t give them a “Patient_X_Viewer” role—that’s insane. You just create a relationship link between the doctor’s uuid and the patient’s record id.
It’s definitely more complex to build than a simple rbac check, but it’s how you actually scale a product without the auth logic becoming a complete disaster.
What about ABAC? (Attribute-Based Access Control)
Before we compare everything, we gotta mention abac. This is like the “wild west” of permissions. Instead of roles or relationships, you use attributes—basically any data point you have on hand.
User attributes: “Is this user over 18?” or “Are they in the ‘Sales’ department?”
Resource attributes: “Is this document marked as ‘Top Secret’?”
Environment attributes: “Is the user logging in from the office IP?” or “Is it during business hours?”
Abac is incredibly powerful but it can be a total pain to manage because the rules get real complex real fast. Most people end up using a mix of rbac for the big buckets and abac for the “only on Tuesdays from a laptop” kind of rules. Now, let’s see how these all stack up against each other.
RBAC vs ReBAC: The Direct Comparison
So, you’re standing at the crossroads trying to pick between these two? Honestly, it’s usually not a “one or the other” deal, but you still gotta know where the trade-offs are gonna bite you.
If we’re talking raw speed for a simple check, rbac usually wins. Why? Because checking if a user has a “Manager” string in their metadata is a fast o(1) lookup. But as previously discussed, that simplicity is exactly what leads to role explosion when you try to force it into a complex b2b saas.
Rebac is the king of flexibility, but it’s heavier on the query logic. Since it relies on a graph or recursive relationships, your authz engine has to traverse those links. If you have a file nested ten levels deep in a folder hierarchy, the system has to “walk” that path to confirm access.
RBAC: High performance for flat structures, but a nightmare to manage once you hit 50+ roles.
ReBAC: Scalable for complex org charts, but needs a solid indexing strategy (like reverse indices) to keep latency low.
Auditing: rbac is just a spreadsheet check. rebac is harder to audit because permissions are “discovered” through relationships at runtime.
How to Actually Implement This
Alright, enough talk—how do you actually build this? You don’t want to hardcode “if” statements in your controller. Here is the architectural path:
Pick a Policy Engine: Don’t roll your own. Use something like Open Policy Agent (OPA) or a Zanzibar-inspired service.
Define your Schema: For rbac, it’s just user -> role -> permission. For rebac, you need to define relations like document#viewer: user or folder#parent: folder.
Decouple Authz: Your app should just ask: is(user_123, “read”, “doc_456”)?. The engine handles the logic.
Sync Data: You need a way to push your “relationships” (like who owns what folder) into your authz store so it can make decisions in real-time.
// Example of a ReBAC-style check using a hypothetical client
const canAccess = await authz.check({
subject: `user:${user.id}`,
relation: ‘viewer’,
object: `folder:${folder.id}`
});
if (!canAccess) throw new Error(“Get out of here!”);
Future-Proofing Your Enterprise Identity Strategy
Look, nobody wants to rewrite their whole identity stack every two years because the product team added a “share with external contractor” feature. You need a strategy that doesn’t box you in when the business pivot.
That’s where ssojet comes in handy. It’s basically an identity orchestration platform that sits between your app and the enterprise world. It handles the messy parts of SAML and OIDC, but more importantly, it gives you a unified way to manage these complex permissions across different enterprise tenants.
Model Agility: You can start with simple rbac for your retail dashboard and slide into rebac when those finance clients demand complex folder hierarchies. ssojet helps bridge that gap by mapping enterprise groups to your internal relationship models.
API-First SAML/OIDC: Instead of wrestling with xml or oidc flows for every new customer, you use a unified api that handles the heavy lifting.
Centralized Control: You get to keep user management in one spot while still having the fine-grained control needed for healthcare apps where “assigned_physician” is a relationship, not just a role.
graph LR
App[Your App] –>|Single API| SJ[[SSOJet](https://ssojet.com)]
SJ –>|SAML| Ent1[Okta/Enterprise]
SJ –>|OIDC| Ent2[Azure AD]
SJ –>|Authz| Model{RBAC or ReBAC}
Honestly, the goal is to stop being the bottleneck for sales. By using a service that supports both models, you’re future-proofed against whatever weird org chart your next big customer throws at you.
*** This is a Security Bloggers Network syndicated blog from SSOJet – Enterprise SSO & Identity Solutions authored by SSOJet – Enterprise SSO & Identity Solutions. Read the original post at: https://ssojet.com/blog/rbac-vs-rebac-comparing-role-based-relationship-based-access-control
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