How to fix the 'unauthorized' error when applying a Kubernetes resource?

Introduction

Kubernetes is a powerful container orchestration platform, but managing access control can be a challenge. In this tutorial, we'll explore how to diagnose and resolve the 'unauthorized' error when applying Kubernetes resources. By understanding Kubernetes RBAC and following best practices, you'll be able to ensure your applications and users have the necessary permissions to interact with your cluster.

Skills Graph

Understanding Kubernetes RBAC

Kubernetes uses a Role-Based Access Control (RBAC) system to manage and control access to resources within the cluster. RBAC allows you to define who can perform what actions on which resources.

Kubernetes RBAC Concepts

• Subjects: The entities (users, groups, or service accounts) that can perform actions on resources.
• Roles: A collection of permissions that define the actions that can be performed on resources.
• ClusterRoles: Roles that apply to resources across the entire cluster.
• RoleBindings: Bindings that associate subjects with roles within a namespace.
• ClusterRoleBindings: Bindings that associate subjects with cluster-wide roles.

RBAC Configuration

RBAC is configured using Kubernetes resources, such as Role, ClusterRole, RoleBinding, and ClusterRoleBinding. Here's an example of a simple Role and RoleBinding:

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

---

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

This configuration grants the "example-user" the ability to get, watch, and list pods in the "default" namespace.

Diagnosing 'Unauthorized' Errors

When applying a Kubernetes resource, you may encounter an "unauthorized" error, which indicates that the current user or service account does not have the necessary permissions to perform the requested action. Diagnosing the root cause of this error is crucial for resolving the issue.

Identifying the Error

When you encounter an "unauthorized" error, you'll typically see a response similar to the following:

Error from server (Forbidden): error when creating "example-resource.yaml": pods "example-pod" is forbidden: user "example-user" cannot create resource "pods" in API group "" in the namespace "default"

This error message provides valuable information, including the resource being created, the user or service account that triggered the error, and the specific permission that was denied.

Investigating the RBAC Configuration

To diagnose the "unauthorized" error, you need to investigate the RBAC configuration in your Kubernetes cluster. You can use the following commands to gather information:

## List all roles and cluster roles in the cluster
kubectl get roles,clusterroles -A

## List all role bindings and cluster role bindings in the cluster
kubectl get rolebindings,clusterrolebindings -A

## Describe a specific role or cluster role
kubectl describe role <role-name> -n <namespace>
kubectl describe clusterrole <cluster-role-name>

## Describe a specific role binding or cluster role binding
kubectl describe rolebinding <role-binding-name> -n <namespace>
kubectl describe clusterrolebinding <cluster-role-binding-name>

These commands will help you understand the current RBAC configuration and identify any missing or incorrect permissions that may be causing the "unauthorized" error.

Resolving 'Unauthorized' Errors

After identifying the root cause of the "unauthorized" error, you can take the following steps to resolve the issue.

Grant the Necessary Permissions

Based on the information gathered from the RBAC investigation, you can grant the necessary permissions to the user or service account that triggered the error. You can do this by creating or updating a Role or ClusterRole and associating it with the subject using a RoleBinding or ClusterRoleBinding.

Here's an example of how to create a Role and RoleBinding to grant a user the ability to create pods in the "default" namespace:

## Role
apiVersion: rbac.authorization.k8s.io/v1
kind: Role
metadata:
  namespace: default
  name: pod-creator
rules:
- apiGroups: [""]
  resources: ["pods"]
  verbs: ["create"]

---

## RoleBinding
apiVersion: rbac.authorization.k8s.io/v1
kind: RoleBinding
metadata:
  name: create-pods
  namespace: default
subjects:
- kind: User
  name: example-user
roleRef:
  kind: Role
  name: pod-creator
  apiGroup: rbac.authorization.k8s.io

After applying this configuration, the "example-user" will be able to create pods in the "default" namespace.

Verify the Permissions

After granting the necessary permissions, you can verify the changes by attempting to apply the Kubernetes resource again. If the "unauthorized" error persists, you may need to double-check your RBAC configuration or investigate further.

You can also use the kubectl auth can-i command to check the permissions of a user or service account:

## Check if the "example-user" can create pods in the "default" namespace
kubectl auth can-i create pods -n default --as example-user

This command will return "yes" if the user has the necessary permissions, or "no" if the permissions are still missing.

By following these steps, you should be able to resolve the "unauthorized" error and successfully apply the Kubernetes resource.

Summary

In this Kubernetes tutorial, we've learned how to identify and fix the 'unauthorized' error when applying resources. By understanding Kubernetes RBAC, diagnosing the root cause, and properly configuring permissions, you can ensure your applications and users have the necessary access to interact with your Kubernetes cluster. Apply these techniques to maintain a secure and well-managed Kubernetes environment.