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OpenPolicyAgent and pathType enforcing

Ingress API allows users to specify different pathType on Ingress object.

While pathType Exact and Prefix should allow only a small set of characters, pathType ImplementationSpecific allows any characters, as it may contain regexes, variables and other features that may be specific of the Ingress Controller being used.

This means that the Ingress Admins (the persona who deployed the Ingress Controller) should trust the users allowed to use pathType: ImplementationSpecific, as this may allow arbitrary configuration, and this configuration may end on the proxy (aka Nginx) configuration.


The example in this repo uses Gatekeeper to block the usage of pathType: ImplementationSpecific, allowing just a specific list of namespaces to use it.

It is recommended that the admin modifies this rules to enforce a specific set of characters when the usage of ImplementationSpecific is allowed, or in ways that best suits their needs.

First, the ConstraintTemplate from template.yaml will define a rule that validates if the Ingress object is being created on an excempted namespace, and case not, will validate its pathType.

Then, the rule K8sBlockIngressPathType contained in rule.yaml will define the parameters: what kind of object should be verified (Ingress), what are the excempted namespaces, and what kinds of pathType are blocked.