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Applications in any namespace

Warning

Please read this documentation carefully before you enable this feature. Misconfiguration could lead to potential security issues.

Introduction

As of version 2.5, Argo CD supports managing Application resources in namespaces other than the control plane's namespace (which is usually argocd), but this feature has to be explicitly enabled and configured appropriately.

Argo CD administrators can define a certain set of namespaces where Application resources may be created, updated and reconciled in. However, applications in these additional namespaces will only be allowed to use certain AppProjects, as configured by the Argo CD administrators. This allows ordinary Argo CD users (e.g. application teams) to use patterns like declarative management of Application resources, implementing app-of-apps and others without the risk of a privilege escalation through usage of other AppProjects that would exceed the permissions granted to the application teams.

Some manual steps will need to be performed by the Argo CD administrator in order to enable this feature.

One additional advantage of adopting applications in any namespace is to allow end-users to configure notifications for their Argo CD application in the namespace where Argo CD application is running in. See notifications namespace based configuration page for more information.

Prerequisites

Cluster-scoped Argo CD installation

This feature can only be enabled and used when your Argo CD is installed as a cluster-wide instance, so it has permissions to list and manipulate resources on a cluster scope. It will not work with an Argo CD installed in namespace-scoped mode.

Switch resource tracking method

Also, while technically not necessary, it is strongly suggested that you switch the application tracking method from the default label setting to either annotation or annotation+label. The reasoning for this is, that application names will be a composite of the namespace's name and the name of the Application, and this can easily exceed the 63 characters length limit imposed on label values. Annotations have a notably greater length limit.

To enable annotation based resource tracking, refer to the documentation about resource tracking methods

Implementation details

Overview

In order for an application to be managed and reconciled outside the Argo CD's control plane namespace, two prerequisites must match:

  1. The Application's namespace must be explicitly enabled using the --application-namespaces parameter for the argocd-application-controller and argocd-server workloads. This parameter controls the list of namespaces that Argo CD will be allowed to source Application resources from globally. Any namespace not configured here cannot be used from any AppProject.
  2. The AppProject referenced by the .spec.project field of the Application must have the namespace listed in its .spec.sourceNamespaces field. This setting will determine whether an Application may use a certain AppProject. If an Application specifies an AppProject that is not allowed, Argo CD refuses to process this Application. As stated above, any namespace configured in the .spec.sourceNamespaces field must also be enabled globally.

Applications in different namespaces can be created and managed just like any other Application in the argocd namespace previously, either declaratively or through the Argo CD API (e.g. using the CLI, the web UI, the REST API, etc).

Reconfigure Argo CD to allow certain namespaces

Change workload startup parameters

In order to enable this feature, the Argo CD administrator must reconfigure the argocd-server and argocd-application-controller workloads to add the --application-namespaces parameter to the container's startup command.

The --application-namespaces parameter takes a comma-separated list of namespaces where Applications are to be allowed in. Each entry of the list supports shell-style wildcards such as *, so for example the entry app-team-* would match app-team-one and app-team-two. To enable all namespaces on the cluster where Argo CD is running on, you can just specify *, i.e. --application-namespaces=*.

The startup parameters for both, the argocd-server and the argocd-application-controller can also be conveniently set up and kept in sync by specifying the application.namespaces settings in the argocd-cmd-params-cm ConfigMap instead of changing the manifests for the respective workloads. For example:

data:
  application.namespaces: app-team-one, app-team-two

would allow the app-team-one and app-team-two namespaces for managing Application resources. After a change to the argocd-cmd-params-cm namespace, the appropriate workloads need to be restarted:

kubectl rollout restart -n argocd deployment argocd-server
kubectl rollout restart -n argocd statefulset argocd-application-controller

Adapt Kubernetes RBAC

We decided to not extend the Kubernetes RBAC for the argocd-server workload by default for the time being. If you want Applications in other namespaces to be managed by the Argo CD API (i.e. the CLI and UI), you need to extend the Kubernetes permissions for the argocd-server ServiceAccount.

We supply a ClusterRole and ClusterRoleBinding suitable for this purpose in the examples/k8s-rbac/argocd-server-applications directory. For a default Argo CD installation (i.e. installed to the argocd namespace), you can just apply them as-is:

kubectl apply -k examples/k8s-rbac/argocd-server-applications/

argocd-notifications-controller-rbac-clusterrole.yaml and argocd-notifications-controller-rbac-clusterrolebinding.yaml are used to support notifications controller to notify apps in all namespaces.

Note

At some later point in time, we may make this cluster role part of the default installation manifests.

Allowing additional namespaces in an AppProject

Any user with Kubernetes access to the Argo CD control plane's namespace (argocd), especially those with permissions to create or update Applications in a declarative way, is to be considered an Argo CD admin.

This prevented unprivileged Argo CD users from declaratively creating or managing Applications in the past. Those users were constrained to using the API instead, subject to Argo CD RBAC which ensures only Applications in allowed AppProjects were created.

For an Application to be created outside the argocd namespace, the AppProject referred to in the Application's .spec.project field must include the Application's namespace in its .spec.sourceNamespaces field.

For example, consider the two following (incomplete) AppProject specs:

kind: AppProject
apiVersion: argoproj.io/v1alpha1
metadata:
  name: project-one
  namespace: argocd
spec:
  sourceNamespaces:
  - namespace-one

and

kind: AppProject
apiVersion: argoproj.io/v1alpha1
metadata:
  name: project-two
  namespace: argocd
spec:
  sourceNamespaces:
  - namespace-two

In order for an Application to set .spec.project to project-one, it would have to be created in either namespace namespace-one or argocd. Likewise, in order for an Application to set .spec.project to project-two, it would have to be created in either namespace namespace-two or argocd.

If an Application in namespace-two would set their .spec.project to project-one or an Application in namespace-one would set their .spec.project to project-two, Argo CD would consider this as a permission violation and refuse to reconcile the Application.

Also, the Argo CD API will enforce these constraints, regardless of the Argo CD RBAC permissions.

The .spec.sourceNamespaces field of the AppProject is a list that can contain an arbitrary amount of namespaces, and each entry supports shell-style wildcard, so that you can allow namespaces with patterns like team-one-*.

Warning

Do not add user controlled namespaces in the .spec.sourceNamespaces field of any privileged AppProject like the default project. Always make sure that the AppProject follows the principle of granting least required privileges. Never grant access to the argocd namespace within the AppProject.

Note

For backwards compatibility, Applications in the Argo CD control plane's namespace (argocd) are allowed to set their .spec.project field to reference any AppProject, regardless of the restrictions placed by the AppProject's .spec.sourceNamespaces field.

Application names

For the CLI and UI, applications are now referred to and displayed as in the format <namespace>/<name>.

For backwards compatibility, if the namespace of the Application is the control plane's namespace (i.e. argocd), the <namespace> can be omitted from the application name when referring to it. For example, the application names argocd/someapp and someapp are semantically the same and refer to the same application in the CLI and the UI.

Application RBAC

The RBAC syntax for Application objects has been changed from <project>/<application> to <project>/<namespace>/<application> to accommodate the need to restrict access based on the source namespace of the Application to be managed.

For backwards compatibility, Applications in the argocd namespace can still be refered to as <project>/<application> in the RBAC policy rules.

Wildcards do not make any distinction between project and application namespaces yet. For example, the following RBAC rule would match any application belonging to project foo, regardless of the namespace it is created in:

p, somerole, applications, get, foo/*, allow

If you want to restrict access to be granted only to Applications in project foo within namespace bar, the rule would need to be adapted as follows:

p, somerole, applications, get, foo/bar/*, allow

Managing applications in other namespaces

Declaratively

For declarative management of Applications, just create the Application from a YAML or JSON manifest in the desired namespace. Make sure that the .spec.project field refers to an AppProject that allows this namespace. For example, the following (incomplete) Application manifest creates an Application in the namespace some-namespace:

kind: Application
apiVersion: argoproj.io/v1alpha1
metadata:
  name: some-app
  namespace: some-namespace
spec:
  project: some-project
  # ...

The project some-project will then need to specify some-namespace in the list of allowed source namespaces, e.g.

kind: AppProject
apiVersion: argoproj.io/v1alpha1
metadata:
    name: some-project
    namespace: argocd
spec:
    sourceNamespaces:
    - some-namespace

Using the CLI

You can use all existing Argo CD CLI commands for managing applications in other namespaces, exactly as you would use the CLI to manage applications in the control plane's namespace.

For example, to retrieve the Application named foo in the namespace bar, you can use the following CLI command:

argocd app get foo/bar

Likewise, to manage this application, keep referring to it as foo/bar:

# Create an application
argocd app create foo/bar ...
# Sync the application
argocd app sync foo/bar
# Delete the application
argocd app delete foo/bar
# Retrieve application's manifest
argocd app manifests foo/bar

As stated previously, for applications in the Argo CD's control plane namespace, you can omit the namespace from the application name.

Using the UI

Similar to the CLI, you can refer to the application in the UI as foo/bar.

For example, to create an application named bar in the namespace foo in the web UI, set the application name in the creation dialogue's Application Name field to foo/bar. If the namespace is omitted, the control plane's namespace will be used.

Using the REST API

If you are using the REST API, the namespace for Application cannot be specified as the application name, and resources need to be specified using the optional appNamespace query parameter. For example, to work with the Application resource named foo in the namespace bar, the request would look like follows:

GET /api/v1/applications/foo?appNamespace=bar

For other operations such as POST and PUT, the appNamespace parameter must be part of the request's payload.

For Application resources in the control plane namespace, this parameter can be omitted.