Kubernetes RBAC: Best Practices and Step-by-Step Guide for Secure Access Management

Summary

Table of Contents

What Is Kubernetes RBAC?

Kubernetes RBAC (Role-Based Access Control) is a security mechanism that determines who has permission to perform specific actions within a Kubernetes cluster. It ensures users, applications, or services only have the access they need and nothing more, which helps keep your cluster safe and well-organized.

For example, you can create roles matching your organization’s different responsibilities. A QA Engineer role might allow users to view test results and logs but prevent them from modifying resources. Meanwhile, a Database Admin role could grant permissions to manage database pods but not access application configurations. This ensures that each user has the necessary permissions to perform their tasks effectively. Now that we have Kubernetes RBAC explained, let’s move on to how it works!!

Before diving deeper, it’s important to understand the fundamental concepts of Kubernetes. As discussed in our previous post Why Use Kubernetes, Kubernetes simplifies container orchestration and offers automation at scale. Understanding how RBAC fits into Kubernetes security features will give you a stronger grasp of its capabilities.

Authentication and Authorization in Kubernetes RBAC

Let us understand this with the diagram given above; what happens here is

STEP 1: Authentication

When a human user or a Kubernetes service account (pod) requests the Kubernetes API server, the system first verifies who you are.
This step checks:

• Are you logged in?
• Are your credentials (like tokens, certificates, or passwords) valid?

Why is this important?

Kubernetes needs to ensure the request is coming from someone it recognizes.

STEP 2: Authorization

After verifying your identity, Kubernetes checks whether you are allowed to perform the requested action. This is done through RBAC policies (Role-Based Access Control).
For example:

• Does this user have permission to create a pod?
• Is this account allowed to read data from the cluster?

Why is this important?

Being authenticated doesn’t necessarily mean you have permission to perform all actions. Authorization enforces security rules.

STEP 3: Admission Control

After authentication and authorization, Admission Control steps in. This checks if the request complies with policies or rules.
For example:

• Is the pod using the right resources (like CPU limits)?
• Are there any restrictions defined by admission controllers?

Why is this important?

Admission controllers ensure requests meet specific conditions or policies set by the cluster administrators. These admission controllers can play a significant role in your overall cluster security, especially when paired with optimization techniques that help reduce unnecessary resource consumption, much like the kubernetes cost optimization discussed in Kubernetes environments.

STEP 4: Perform the Action

Once the request has passed Authentication, Authorization, and Admission Control, Kubernetes will execute the action.
For example:

• Create a pod
• Read data
• Update or delete resources

Why is this important?

This step ensures the request is finally completed after all the checks are passed.

Understanding Kubernetes RBAC Components

As you know, Kubernetes allows you to manage and control who has access to the resources within your cluster. This is done through RBAC (Role-Based Access Control), which defines and enforces rules on what actions users and services can perform. RBAC ensures that only authorized users or applications can access specific Kubernetes resources, providing security and proper access management.

RBAC in Kubernetes establishes four key components:
Role
ClusterRole
RoleBinding
ClusterRoleBinding
All of these work together to manage access control and permissions within the cluster. These objects work together to assign permissions to users or service accounts. Let’s break them down:

1. Role

A Role is a set of permissions that defines which actions (like get, create, delete) can be performed on specific Kubernetes resources (such as Pods, Deployments, and Namespaces) within a single namespace. Roles are limited to a specific namespace, meaning they only apply to resources within that namespace.

• Example: A Role can grant a developer permission to view Pods but not to delete them, but only within the “development” namespace.

2. ClusterRole

A ClusterRole is similar to a Role but applies to all namespaces or resources that are not part of any namespace (like Nodes). ClusterRoles define permissions for cluster-wide resources.

• Example: A ClusterRole could allow an admin to view all Pods across all namespaces or to access Nodes outside any namespace.

ClusterRoles are helpful when managing access to resources at the cluster level or across all namespaces.

3. RoleBinding

A RoleBinding associates a Role with a user or service account (referred to as Subjects) within a specific namespace, allowing you to assign the permissions outlined in the Role to designated users or applications within that namespace.

• Example: A RoleBinding can permit a developer to read Pods within the “development” namespace based on the PodReader Role.

RoleBindings ensures that roles are applied to the right users or services within a specific namespace.

4. ClusterRoleBinding

A ClusterRoleBinding operates like a RoleBinding, but it links a ClusterRole to users or service accounts at the cluster-wide level. You can assign a ClusterRole to users or services across the Kubernetes cluster.

• Example: A ClusterAdmin ClusterRole (which grants complete control over the cluster) can be assigned to an admin using a ClusterRoleBinding, giving them access to all namespaces and cluster-wide resources.

ClusterRoleBindings help grant permissions at the global, cluster-wide level.

Users vs. Service Accounts

Before diving into setting up RBAC, it’s essential to understand the difference between Users and Service Accounts in Kubernetes:

• Users: Users represent people who authenticate to the Kubernetes cluster. They usually authenticate using an external identity provider (like Google Accounts, private keys, or usernames/passwords). Kubernetes doesn’t handle user management directly, so users cannot be created with kubectl. You must manage them externally, like through an identity provider.
• Service Accounts: Service Accounts are specialized accounts that Kubernetes uses to manage applications or processes within the cluster. Unlike users, Service Accounts are managed by Kubernetes and can be created and assigned roles directly via the API. Service Accounts are typically used to automate processes, like managing applications or handling system tasks.

Let’s now see a full tutorial on Kubernetes RBAC.

How to Implement Kubernetes RBAC: Step-by-Step Guide

In this guide, we’ll explore how to configure Role-Based Access Control (RBAC) in Kubernetes. We’ll create a Service Account and then assign it a Role to manage Pods within a specific namespace. This Service Account will only have permissions to list, create, and update Pods in that namespace, but not delete or modify other resources.

Ensure that you have a Kubernetes cluster up and running before you start. If not, follow a guide to install Kubernetes first.

Step 1: Check if RBAC is Enabled

RBAC is typically enabled by default in most Kubernetes distributions, but you should verify it’s available. To do so, run the following command:

If you see the line rbac.authorization.k8s.io/v1, then RBAC is enabled, and you’re good to go.

If RBAC is disabled, you’ll need to launch the Kubernetes API server using the --authorization-mode=RBAC flag. Consult your distribution’s documentation for steps to enable it manually.

Step 2: Create a Service Account

Next, we will create a Service Account that will be utilized in the upcoming steps to assign roles. Execute this command:

Now, create an authorization token for the Service Account:

This token is saved to the $TOKEN environment variable, which you’ll use to configure kubectl.

Step 3: Configure kubectl with Your Service Account

To use the Service Account for authentication, you must add it to your kubectl configuration.

1. Begin by configuring the credentials for the Service Account:

2. Next, create a new context for the Service Account:

3. Check your current context:

4. Switch to your new context:

Now, try to list Pods in the namespace:

You will see a Forbidden error because the Service Account doesn’t have permission yet.

Prior to proceeding, revert to your admin context:

Step 4: Create a Role

Next, we’ll create a Role granting permission to interact with Pods in a specific namespace.

Create a role.yaml file with the following content:

This Role allows the get, list, create, and update actions on Pods in the default namespace.

Now, apply the Role to the cluster:

Step 5: Create a RoleBinding

A RoleBinding links the Role we created to the Service Account, enabling the Service Account to access the permissions specified in the Role.

Create a rolebinding.yaml file with the following content:

Now, apply the RoleBinding to your cluster:

Step 6: Verify Permissions

Now that the Role and RoleBinding are set up let’s check if the Service Account has the correct permissions.

Return to the context of your Service Account:

1.Try to list the Pods:

2. You should see the list of Pods (or an empty list if none exist). This confirms that the Service Account now has permission to list Pods.

Try creating a Pod:

3. Verify that the Pod was created:

4. Try deleting the Pod:

5. You’ll see a Forbidden error because the Role we assigned doesn’t include the delete permission.

You’ve set up RBAC in Kubernetes! Now, your Service Account can only interact with Pods as allowed, ensuring secure access to resources. This was all about the Kubernetes RBAC tutorial explained in detail. Let’s now understand the security threats and solutions surrounding it.”

Real-World Kubernetes RBAC Security Threats and Solutions

1. RBAC Buster Attack

In the “RBAC Buster” attack, hackers take advantage of a misconfigured Kubernetes API server that lets anyone access it without authentication. They use this access to set harmful RBAC policies and run cryptocurrency miners.

Solution: Set up strong authentication for Kubernetes API servers and regularly check for and fix any security issues.

2. Argo CD Vulnerability

A weakness in Argo CD lets unauthenticated users bypass security checks by exploiting a flaw in how JWTs are handled, giving them admin-level access and the ability to carry out malicious actions.

Solution: Protect service accounts, API endpoints, and tools like Argo CD by using strong authentication and authorization controls. Also, keep them updated to fix any known issues.

Kubernetes RBAC Best Practices

The best practices that you should follow to function properly are mentioned below.

1. Always Enable RBAC

RBAC is a must-have feature for securing Kubernetes clusters. It’s crucial to ensure that RBAC (Role-Based Access Control) is enabled in every production environment. This prevents unauthorized access and allows you to manage who can execute particular actions within your cluster.

Never rely on default administrator accounts. Instead, each user, service, or application should have its identity and assigned role. This enables you to assign precise permissions to users while restricting unnecessary access.

2. Keep Roles Specific

In Kubernetes, Roles specify the actions a user can take on specific resources. It’s ideal to define roles with as much specificity as possible.

• Create roles that provide only the essential permissions for a given task. For example, if a user only requires read access to Pods, do not give them permission to create or delete them.

• Instead of assigning a significant role with many permissions, assign users more minor roles with the exact permissions they need. This simplifies management and helps minimize security risks. A smaller attack surface means less chance of someone gaining unnecessary access.

3. Understand Roles vs ClusterRoles

Kubernetes has two types of roles: Roles and cluster roles.

• Roles: These are used for permissions within a specific namespace, like allowing a user to view Pods in one namespace.

• ClusterRoles: These are used for cluster-wide permissions, like granting access to nodes or viewing all Pods across the cluster.

Always use Roles for permissions that apply to specific namespaces. Only use ClusterRoles for permissions that apply to the entire cluster, such as access to nodes. Be careful not to give ClusterRoles to users who only need access within a single namespace, as this can give them too much access.

4. Regularly Review and Remove Unused Roles

Over time, roles, permissions, and users can change. Some roles may no longer be necessary, and unused permissions can create security risks. Perform regular audits of your roles, role bindings, and cluster roles. Eliminate unnecessary or unused components to maintain a cleaner system and ensure users have access only to what is required. Removing unused roles also reduces the chances of over-privileged accounts staying active and accessible.

5. Avoid Using Wildcards in Roles

In Kubernetes, when defining roles, you can use the * wildcard in the resources and verbs fields, which allows broad access. Avoid using the * wildcard, especially in production environments. Using * could give users access to any new resource types added in the future, not just the ones you planned. This could expose sensitive resources that users shouldn’t have access to. Being specific about the permissions and resources each user can access is safer.

Conclusion