Kubernetes Access via Public Clients: Mastering OIDC with PKCE
Kubernetes access management is critical for maintaining security and efficiency in your clusters. By integrating with an identity provider using a public client, you can enhance your authentication process without the need for a client secret. This setup is particularly useful in scenarios where you want to avoid exposing sensitive information while still ensuring secure access to your Kubernetes resources.
The mechanism involves three key components: kubectl, your identity provider (like Keycloak), and kube-apiserver. Kubectl initiates the login process using the kubelogin exec plugin, which retrieves a token from the identity provider. This token contains essential user information, such as username and group membership. Kube-apiserver then validates this token and uses Role-Based Access Control (RBAC) to determine what actions the user can perform. For configuration, you'll need to set parameters like --oidc-issuer-url and --oidc-client-id to point to your identity provider and identify your client.
In production, be aware of common pitfalls. If you're using a self-hosted Keycloak instance, ensure its certificate is signed by a publicly trusted CA. If not, you'll need to specify the CA certificate using the --oidc-ca-file flag. This detail is crucial for avoiding authentication issues. Keep your Kubernetes version in mind, as this integration is continually evolving, and staying updated can save you from potential headaches.
Key takeaways
- →Configure kubectl with the kubelogin exec plugin to streamline authentication.
- →Use PKCE to enhance security by preventing interception of authorization codes.
- →Validate user identity with RBAC based on the claims in the ID token.
- →Specify the OIDC issuer URL and client ID for proper integration.
- →Add the CA certificate flag if using a self-signed Keycloak certificate.
Why it matters
Implementing public clients with PKCE in Kubernetes significantly reduces the risk of credential exposure, enhancing overall cluster security. This method allows for seamless integration with identity providers while maintaining strict access controls.
Code examples
1apiVersion: rbac.authorization.k8s.io/v1
2 kind: ClusterRoleBinding
3 metadata:
4 name: platform-viewers
5 subjects:
6 - kind: Group
7 name: platform-viewer
8 apiGroup: rbac.authorization.k8s.io
9 roleRef:
10 kind: ClusterRole
11 name: view
12 apiGroup: rbac.authorization.k8s.io1users:
2 - name: oidc
3 user:
4 exec:
5 apiVersion: client.authentication.k8s.io/v1
6 command: kubectl
7 args:
8 - oidc-login
9 - get-token
10 - --oidc-issuer-url=https://<your-keycloak-host>/realms/<realm>
11 - --oidc-client-id=kubernetes$ kubectl auth whoami
ATTRIBUTE VALUE
Username jane.doe@example.com
Groups [platform-viewer system:authenticated]When NOT to use this
The official docs don't call out specific anti-patterns here. Use your judgment based on your scale and requirements.
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