Kubernetes is a popular container orchestration tool that allows you to deploy and manage containerized applications at scale. However, like any other technology, Kubernetes has its own security concerns that need to be addressed to ensure that your cluster is secure. One of the most critical security concerns in Kubernetes is misconfigured RBAC (Role-Based Access Control). RBAC is used to define and manage user access and permissions within the cluster. It defines roles, role bindings, and service accounts to control who can perform certain actions within the cluster. To avoid common Kubernetes security misconfigurations, it is essential to follow RBAC best practices. This includes:
Let’s look at the most common Misconfigured permissions. This arise when the roles and role bindings are not configured correctly, allowing users or services to have more privileges than they should.
Let’s say a developer creates a new service account called myapp-sa
for an application that they are deploying in the Kubernetes cluster. They set the service account’s permissions to include access to sensitive resources, such as secrets or other Kubernetes objects. However, they forget to create a role binding that associates the service account with a role that grants only the necessary permissions. As a result, the service account is granted more permissions than it should have.
yamlCopy code | |
# serviceaccount.yaml | |
apiVersion: v1 | |
kind: ServiceAccount | |
metadata: | |
name: myapp-sa | |
--- | |
# role.yaml | |
kind: Role | |
apiVersion: rbac.authorization.k8s.io/v1 | |
metadata: | |
name: myapp-role | |
rules: | |
- apiGroups: [""] # "" indicates the core API group | |
resources: ["pods", "secrets"] # give access to pods and secrets | |
verbs: ["get", "watch", "list", "create", "update", "delete"] # give full access | |
--- | |
# misconfigured-role-binding.yaml | |
kind: RoleBinding | |
apiVersion: rbac.authorization.k8s.io/v1 | |
metadata: | |
name: myapp-role-binding | |
roleRef: | |
apiGroup: rbac.authorization.k8s.io | |
kind: Role | |
name: myapp-role # reference the role created earlier | |
subjects: | |
- kind: ServiceAccount | |
name: myapp-sa # reference the service account created earlier | |
In this example, the myapp-sa
service account is created with full access to pods and secrets. However, the myapp-role-binding
role binding is misconfigured because it references the myapp-role
role, which grants full access to the resources. As a result, the myapp-sa
service account is granted more permissions than it should have, potentially exposing sensitive data to unauthorized access. To avoid this misconfiguration, the myapp-role
should be updated to grant only the necessary permissions, and the myapp-role-binding
should be updated to reference the updated role. For example, if the application only requires read-only access to pods and secrets, the myapp-role
can be updated to only grant get
and list
permissions.
yamlCopy code | |
# role.yaml | |
kind: Role | |
apiVersion: rbac.authorization.k8s.io/v1 | |
metadata: | |
name: myapp-role | |
rules: | |
- apiGroups: [""] | |
resources: ["pods", "secrets"] | |
verbs: ["get", "list"] | |
With this update, the myapp-sa
service account is granted only the necessary read-only permissions.
Tu further validate the permission you can run :
kubectl auth can-i <verb> <resource> –as=system:serviceaccount:<namespace>:<serviceaccountname> [-n <namespace>]
By following Kubernetes best practices and regularly reviewing RBAC configurations, you can minimize the risk of misconfigurations and ensure that your cluster is secure. Additionally, using tools such as Kube-bench and kubeaudit can help identify misconfigurations and vulnerabilities in Kubernetes clusters.