OpenShift Role-Based Access Control Background

Almost every interaction with an OpenShift environment that you can think of requires going through the master’s API. All API interactions are both authenticated (AuthN - who are you?) and authorized (AuthZ - are you allowed to do what you are asking?).

Just like a user has permissions (AuthZ), sometimes we may wish for non-users to be able to perform actions against the API. These "non-users" are referred to as service accounts.

OpenShift automatically creates a few special service accounts in every project. The default service account has its credentials automatically injected into every pod that is launched. By changing the permissions for that service account, we can do interesting things.

Exercise: Grant Service Account View Permissions

The parksmap application wants to talk to the OpenShift API to learn about other Pods, Services, and resources within the Project. You’ll learn why soon!

oc policy add-role-to-user view -z default

The oc policy command above is giving a defined role (view) to a user. But we are using a special flag, -z. What does this flag do? From the -h output:

-z, --serviceaccount=[]: service account in the current namespace to use as a user

The -z syntax is a special one that saves us from having to type out the entire string, which, in this case, is system:serviceaccount:project-ksoong:default. It’s a nifty shortcut.

Note
The -z flag will only work for service accounts in the current namespace. Beware of this if you attempt to use it in the future.

Now that the default Service Account has view access, it can query the API to see what resources are within the Project. This also has the added benefit of supressing the error message! Although, in reality, we fixed the application.

Exercise: Grant User View Permissions

f you create a project, you are that project’s administrator. This means that you can grant access to other users, too. If you like, give your neighbor view access to your explore project using the following command:

oc policy add-role-to-user view userXY

Have them go to the project view by clicking the Projects button and verify that they can see your project and its resources. This type of arrangement (view but not edit) might be ideal for a developer getting visibility into a production application’s project.

Exercise: Redeploy Application

One more step is required. We need to re-deploy the application because it’s given up trying to query the API.

This time we’ll use the web console. Find your project-userXY project, and then click "Applications" and then "Deployments". You’ll see your only application, parksmap, listed. Click that.

The deployment screen tells you a lot about how the application will be deployed. At the top right, there is a button labeled "Deploy". This button will cause a new deployment (which you know creates a new ReplicationController, right?).

new-parksmap-deploy

You’ll see that a new deployment is immediately started. Return to the overview page and watch it happen. You might not be fast enough! If you look at the logs for the application now, you should see no errors. That’s great.

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