Glossary of Cerbos terms

This documentation is for an as-yet unreleased version of Cerbos. Choose 0.36.0 from the version picker at the top right or navigate to https://docs.cerbos.dev for the latest version.
ACTION

Any application-defined operation that could be performed on a RESOURCE. Actions could be coarse-grained like create, update, delete, view or fine-grained like view:public, update:invoice_amt. What actions are possible is determined by the application developers and they can use Cerbos policies to define the rules that must be satisfied in order for a given PRINCIPAL to perform one of those actions on a RESOURCE INSTANCE.

ATTRIBUTE

A piece of information about a PRINCIPAL or a RESOURCE INSTANCE that is useful for making an access decision. Cerbos is stateless and has no access to your application data. In order to make access decisions, Cerbos needs to know relevant information about the users and the objects they are trying to access. This information is sent as attributes in the Cerbos API request. For example, if you want to restrict users from a particular geography to access only objects from that same geography, you might define a Cerbos rule condition like request.resource.attr.geography == request.principal.attr.geography. Then, in the Cerbos API request, you must send the geography attribute (as determined by your application) for both the principal and the resource instance.

CONDITION

Cerbos policy rules can make dynamic, context-aware decisions by evaluating conditional logic against the ATTRIBUTES sent through the API request. See Conditions for details.

DERIVED ROLE

Most applications have a statically defined set of roles such as admin, writer, employee and so on. Cerbos derived roles are a feature in which these static roles can be dynamically augmented with context-awareness. For example, someone with the employee role can be augmented to us_employee by checking whether their location is in the USA. Cerbos policies can then be written to target the us_employee derived role instead of the employee role — which removes repetition of logic across policy files. See Derived roles for details.

PDP

Policy decision point. Essentially, where policies are executed and decisions are made. When you start a Cerbos server through one of the distribution artefacts (binary, container, Helm chart), you start a PDP.

PRINCIPAL

A human or an automated process that wants to perform one or more ACTIONS on one or more RESOURCE INSTANCES. Typically called a "user" in most settings but Cerbos uses the term Principal to avoid any ambiguity about whether the user is human or not. You can create principal policies to create exceptions for particular users.

RESOURCE

A kind or a category of application objects with similar characteristics. The concept is very similar to a class in object-oriented programming. For example, in an inventory system, Invoice is a resource. Your system might have thousands or millions of invoices (RESOURCE INSTANCES: similar to objects in object-oriented programming) but there would only be a single Cerbos resource policy for Invoice which encodes all the access rules.

Sometimes the term resource is used to refer to a RESOURCE INSTANCE when the meaning is obvious from the context (the API request fields are a good example of this).
RESOURCE INSTANCE

A specific item of a RESOURCE kind. If a RESOURCE is a class, a RESOURCE INSTANCE is an object of that class. For example, an invoice that was issued to "Acme Corp." with ID "I23456" is a RESOURCE INSTANCE. When making access decisions using Cerbos, you need to send information about the resource instances to the Cerbos CheckResources API endpoint. The Cerbos PDP would then use the appropriate resource policy (determined by the kind specified in the resource instance) to process the information and make an access decision.