ApplicationSet Security

ApplicationSet is a powerful tool, and it is crucial to understand its security implications before using it.

Only admins may create/update/delete ApplicationSets

ApplicationSets can create Applications under arbitrary Projects. Argo CD setups often include Projects (such as the default) with high levels of permissions, often including the ability to manage the resources of Argo CD itself (like the RBAC ConfigMap).

ApplicationSets can also quickly create an arbitrary number of Applications and just as quickly delete them.

Finally, ApplicationSets can reveal privileged information. For example, the git generator can read Secrets in the Argo CD namespace and send them to arbitrary URLs (e.g. URL provided for the api field) as auth headers. (This functionality is intended for authorizing requests to SCM providers like GitHub, but it could be abused by a malicious user.)

For these reasons, only admins may be given permission (via Kubernetes RBAC or any other mechanism) to create, update, or delete ApplicationSets.

Admins must apply appropriate controls for ApplicationSets’ sources of truth

Even if non-admins can’t create ApplicationSet resources, they may be able to affect the behavior of ApplicationSets.

For example, if an ApplicationSet uses a git generator, a malicious user with push access to the source git repository could generate an excessively high number of Applications, putting strain on the ApplicationSet and Application controllers. They could also cause the SCM provider’s rate limiting to kick in, degrading ApplicationSet service.

Templated project field

It’s important to pay special attention to ApplicationSets where the project field is templated. A malicious user with write access to the generator’s source of truth (for example, someone with push access to the git repo for a git generator) could create Applications under Projects with insufficient restrictions. A malicious user with the ability to create an Application under an unrestricted Project (like the default Project) could take control of Argo CD itself by, for example, modifying its RBAC ConfigMap.

If the project field is not hard-coded in an ApplicationSet’s template, then admins must control all sources of truth for the ApplicationSet’s generators.