RBAC in Kubernetes.

Role-Based Access Control (RBAC) is a key security feature in Kubernetes that allows administrators to dynamically configure policies to control who can access specific Kubernetes resources and what actions they can perform. Here's an in-depth explanation:

Key Concepts of RBAC

1. Role:

   • A Role contains a set of permissions, which are rules defining what actions can be performed on which resources.

   • Roles are namespaced. They apply only to resources within a specific namespace.

2. ClusterRole:

   • Similar to a Role, but ClusterRoles are not namespaced. They can be used to grant permissions cluster-wide or across all namespaces.

3. RoleBinding:

   • A RoleBinding grants the permissions defined in a Role to a user, group, or service account within a specific namespace.

   • It links a Role to one or more subjects (users, groups, or service accounts).

4. ClusterRoleBinding:

   • Similar to RoleBinding, but ClusterRoleBinding grants permissions to users, groups, or service accounts across the entire cluster.

How RBAC Works

1. Defining a Role or ClusterRole:

   • You create a Role or ClusterRole to specify the permissions.

   • Example:

       kind: Role
       apiVersion: rbac.authorization.k8s.io/v1
       metadata:
         namespace: default
         name: pod-reader
       rules:
       - apiGroups: [""]
         resources: ["pods"]
         verbs: ["get", "watch", "list"]
     

2. Binding the Role/ClusterRole to Subjects:

   • Use RoleBinding or ClusterRoleBinding to associate the Role or ClusterRole with specific users, groups, or service accounts.

   • Example:

       kind: RoleBinding
       apiVersion: rbac.authorization.k8s.io/v1
       metadata:
         name: read-pods
         namespace: default
       subjects:
       - kind: User
         name: jane
         apiGroup: rbac.authorization.k8s.io
       roleRef:
         kind: Role
         name: pod-reader
         apiGroup: rbac.authorization.k8s.io
     

Detailed Steps for RBAC Setup

1. Create a Role/ClusterRole:

   • Define what actions are permitted on which resources.

2. Create a RoleBinding/ClusterRoleBinding:

   • Link the Role/ClusterRole to a subject (user, group, or service account).

3. Test the RBAC Configuration:

   • Verify the permissions using kubectl auth can-i command.

   • Example: kubectl auth can-i get pods --namespace=default

Use Cases of RBAC

• Namespace Isolation: Assign specific permissions to users within a namespace without affecting other namespaces.

• Cluster Administration: Use ClusterRoles and ClusterRoleBindings for cluster-wide administrative tasks.

• Service Account Permissions: Limit the access of service accounts to only the necessary resources and actions.

• RBAC is a powerful mechanism in Kubernetes that provides fine-grained access control, enhancing security and ensuring proper governance in a Kubernetes environment.