Securing Kubernetes with RBAC: A Quick Guide
Published: 2023-12-26 02:07:08

Role-Based Access Control (RBAC) serves as a fundamental pillar in safeguarding and regulating access within the bustling Kubernetes ecosystem, where services, pods, and nodes act as diverse entities. Similar to a city's need for a comprehensive system to manage access to buildings and resources, Kubernetes relies on RBAC to control access to its myriad resources.

In a distributed and segmented operational landscape, RBAC provides granular control over user permissions, preventing chaos in a multi-tenant environment. Without RBAC, managing permissions would be equivalent to leaving the doors of a secure facility unlocked, risking unauthorized access.

At its core, Kubernetes RBAC revolves around defining roles with specific permissions, assigning these roles to users or groups, and tailoring access rights precisely to the cluster's needs. This approach ensures both security and operational efficiency within the Kubernetes environment.

## 1. Roles and ClusterRoles:

- Roles operate at the namespace level, defining a set of permissions for resources within a specific namespace. ClusterRoles, on the other hand, operate at the cluster level, providing permissions across all namespaces.
- Roles are used to grant access within a limited scope, allowing fine-grained control over resources like pods, services, and deployments. ClusterRoles are suitable for granting broad access to cluster-wide resources like nodes, persistent volumes, and other non-namespaced objects.

#### i. Role Example In Kubernetes:

A Role in the “ns-sample-system” namespace granting read access to pods:

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

#### ii. ClusterRole Example In Kubernetes:

A ClusterRole, which is granting read access to secrets across all namespaces:

```sh
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRole
metadata:
  name: secret-reader
rules:
- apiGroups: [""]
  resources: ["secrets"]
  verbs: ["get", "watch", "list"]
```

## 2. Understanding Verbs Used in RBAC:

Kubernetes actions are defined in the form of Verbs like below:

- Get: Allows reading a specific resource.
- List: Permits listing all instances of a resource.
- Watch: Enables watching changes to a particular resource.
- Create: Grants the ability to create new instances of a resource.
- Update: Provides permission to modify existing resources.
- Patch: Similar to update, but for making partial changes.
- Delete: Allows the removal of specific resources.
- Exec: Permits executing commands in a container.
- Bind: Enables linking a role to specific subjects.

## 3. ServiceAccounts in Kubernetes:
ServiceAccounts are like worker robots in Kubernetes, playing a crucial role in making things happen automatically. Unlike accounts for people, these are for applications and pods. Just picture them as robot users doing specific jobs in the Kubernetes world. These jobs can be anything from running a pod to handling workloads or talking to the Kubernetes API. Essentially, ServiceAccounts act as the automated helpers that keep the Kubernetes cluster running smoothly by taking care of various tasks without needing human intervention.

#### i. Integrating ServiceAccounts with RBAC:
Connecting ServiceAccounts with RBAC lets Kubernetes administrators give special jobs to automated processes. This makes sure that the access control system is both careful and secure. It doesn't just regulate people using the system but also makes sure that automated processes follow the same strict security rules. Below example illustrate the example of applying RBAC on the `deployment-service-account`.

**Role For Deployment Service Account:**
```sh
kind: Role
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  namespace: deployment
  name: deployment-manager
rules:
- apiGroups: ["apps", ""]
  resources: ["deployments", "pods"]
  verbs: ["create", "update", "delete"]
```

**Binding Role With Service Account:**
```sh
kind: RoleBinding
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  name: deployment-manager-binding
  namespace: deployment
subjects:
- kind: ServiceAccount
  name: deployment-service-account
  namespace: deployment
roleRef:
  kind: Role
  name: deployment-manager
  apiGroup: rbac.authorization.k8s.io
```


## 4. RBAC Best Practices:

Implementing RBAC effectively involves understanding and applying best practices listed below:

#### i. Adhere to Least Privilege:
Grant users and service accounts the minimum permissions required to perform their tasks. This principle limits potential security risks by restricting unnecessary access.

#### ii. Regular Auditing and Review:
Conduct frequent audits of RBAC configurations to identify and rectify any discrepancies or outdated access permissions. This proactive approach helps maintain the security posture of the Kubernetes environment.

#### iii. Namespace-specific Considerations:
Understand the nuances of role bindings within namespaces. Tailor permissions to the specific requirements of each namespace, ensuring that access is finely tuned to the needs of distinct projects or teams.

#### iv. Document RBAC Policies:
Maintain comprehensive documentation of RBAC policies, clearly outlining roles, permissions, and the reasoning behind specific access decisions. This documentation aids in knowledge sharing and ensures a transparent understanding of the access control framework.

#### v. Regularly Update RBAC Policies:
Keep RBAC policies up-to-date with the evolving needs of the organization. Regularly revisit and adjust permissions to align with changes in project structures, teams, and operational requirements.

## 5. Conclusion: Keep Kubernetes Safe with RBAC:

In the end, using RBAC in Kubernetes is like having a smart plan to keep everything safe. It's the superhero that makes sure only the right things can do their jobs, stopping any chaos or trouble. RBAC's special powers let it control who can do what, making the whole system work smoothly and securely. So, if you want a safe and organized Kubernetes world, remember to let RBAC be your superhero!