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Security11 December 2024·3 min read

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

Almost every incident worth writing about starts with something that was working exactly as designed.

Paycux engineering

Almost every incident worth writing about starts with something that was working exactly as designed. The design was just describing a different world than the one the system ended up in.

This piece walks through how we think about it at Paycux, what we have changed our minds about, and where the sharp edges are.

RBAC vs. ACL: a quick comparison

That brings us to rbac vs. acl: a quick comparison. Rotate on a schedule, not on an incident. A rotation path that has been exercised is a routine change; one that has never been used is an outage waiting for the worst possible moment.

Blast radius is the metric that actually matters. A credential that can read one organization's data is an incident; the same credential scoped to every organization is a company-ending event, and the difference is a design decision made months earlier.

What is RBAC?

What is RBAC? is where this gets concrete. Detection beats prevention when prevention is uncertain. If you cannot stop a class of abuse outright, make sure it produces a signal loud enough that someone sees it the same day.

Detection beats prevention when prevention is uncertain. If you cannot stop a class of abuse outright, make sure it produces a signal loud enough that someone sees it the same day.

  • Scope credentials to the smallest useful blast radius
  • Alert on the abuse you cannot prevent
  • Exercise the rotation path before you need it
  • Log the decision, not just the outcome

What are ACLs?

That brings us to what are acls?. Detection beats prevention when prevention is uncertain. If you cannot stop a class of abuse outright, make sure it produces a signal loud enough that someone sees it the same day.

Detection beats prevention when prevention is uncertain. If you cannot stop a class of abuse outright, make sure it produces a signal loud enough that someone sees it the same day.

Detection beats prevention when prevention is uncertain.

When to use RBAC, ACLs, or both

Consider when to use rbac, acls, or both. Blast radius is the metric that actually matters. A credential that can read one organization's data is an incident; the same credential scoped to every organization is a company-ending event, and the difference is a design decision made months earlier.

Rotate on a schedule, not on an incident. A rotation path that has been exercised is a routine change; one that has never been used is an outage waiting for the worst possible moment.

Are there other options to enable access control?

Are there other options to enable access control? deserves its own treatment. Rotate on a schedule, not on an incident. A rotation path that has been exercised is a routine change; one that has never been used is an outage waiting for the worst possible moment.

Rotate on a schedule, not on an incident. A rotation path that has been exercised is a routine change; one that has never been used is an outage waiting for the worst possible moment.

Where this leaves us

If there is one thing worth taking away, it is that the expensive decisions are the ones made implicitly. Making them on purpose costs an afternoon.

If you are working through the same problem and want to compare notes, the docs cover the mechanics and the console shows the behaviour on your own data.

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