This page provides an overview for the role-based access control (RBAC) system provided by Kubernetes, and how you can use Kubernetes RBAC in Google Kubernetes Engine.
Kubernetes includes a built-in role-based access control (RBAC) mechanism that allows you to configure fine-grained and specific sets of permissions that define how a given Google Cloud user, or group of users, can interact with any Kubernetes object in your cluster, or in a specific Namespace of your cluster.
Kubernetes RBAC is enabled by default.
Before you begin
To prepare for this task, perform the following steps:
- Ensure that you have enabled the Google Kubernetes Engine API. Enable Google Kubernetes Engine API
- Ensure that you have installed the Cloud SDK.
- Set your default project ID:
gcloud config set project [PROJECT_ID]
- If you are working with zonal clusters, set your default compute zone:
gcloud config set compute/zone [COMPUTE_ZONE]
- If you are working with regional clusters, set your default compute region:
gcloud config set compute/region [COMPUTE_REGION]
gcloudto the latest version:
gcloud components update
Interaction with Identity and Access Management
You can use both Cloud Identity and Access Management and Kubernetes RBAC to control access to your GKE cluster:
Cloud IAM is not specific to Kubernetes; it provides identity management for multiple Google Cloud products, and operates primarily at the level of the Google Cloud project.
Kubernetes RBAC is a core component of Kubernetes and allows you to create and grant roles (sets of permissions) for any object or type of object within the cluster.
In GKE, Cloud IAM and Kubernetes RBAC are integrated to authorize users to perform actions if they have sufficient permissions according to either tool. This is an important part of bootstrapping a GKE cluster, since by default Google Cloud users do not have any Kubernetes RBAC RoleBindings.
In order to authorize users using Google Cloud accounts, the client must
be correctly configured to authenticate using those accounts first. For example,
if you are using
kubectl, you must
kubectl command to authenticate to Google Cloud
before running any commands that require authorization.
Prerequisites for using Kubernetes RBAC on GKE cluster v1.11.x and older
In GKE clusters using GKE v1.11.x and older, there is a limitation that Cloud IAM cannot grant the ability to create a Kubernetes RBAC Role or ClusterRole. However, the Kubernetes Engine Admin Cloud IAM role does grant users with the ability to create a Kubernetes RBAC RoleBinding or ClusterRoleBinding for any user, including themselves, which can be used to bind Google Cloud users to predefined RBAC Roles.
In particular, the
cluster-admin predefined RBAC role grants users full
permissions in the cluster. Therefore, to bootstrap a user to allow them to
create RBAC Roles and ClusterRoles, issue the following command, replacing
with the target user's
Google Cloud login email address.
kubectl create clusterrolebinding cluster-admin-binding \ --clusterrole cluster-admin \ --user
Google Groups for GKE
Previously, you could only grant roles to Google Cloud user accounts or Cloud IAM service accounts. Google Groups for GKE (Beta) allows you to grant roles to the members of a G Suite Google Group. With this mechanism, the users and groups themselves are maintained by your G Suite administrators, completely outside of Kubernetes or Cloud Console, so your cluster administrators do not need detailed information about your users. Another benefit is integration with your existing user account management practices, such as revoking access when someone leaves your organization.
Configure Google Groups for use with RBAC
Configuring your cluster to use this feature, as well as the syntax for referencing a G Suite Google Group in Kubernetes RBAC is discussed later in this topic. First, you need to set up your Google Groups following the steps below:
- Create a G Suite Google Group in your domain, named
gke-security-groups@[yourdomain.com]. The group must be named exactly
- Create groups, if they do not already exist, that represent groups of users or groups who should have different permissions on your clusters.
- Add these groups (not users) to the membership of
To check whether a given user has permission to create, modify, or view a
resource in the cluster based on group membership, GKE checks
both whether the user is a member of a group with access, and whether that group
is a member of your domain's
Information about G Suite Google Group membership is cached for a short time. It may take a few minutes for changes in group memberships to propagate to all of your clusters.
Configuring your cluster to use Google Groups for GKE
After your G Suite Google Groups administrator
sets up your groups, create a new cluster using the
gcloud command, and add the following option, substituting your own
following is an example cluster-creation command:
gcloud beta container clusters create my-cluster \ --security-group="gke-security-groups@[yourdomain.com]"
Now you are ready to create Roles, ClusterRoles, RoleBindings, and ClusterRoleBindings that reference your G Suite Google Groups.
Defining and assigning permissions
You define your RBAC permissions by creating the following kinds of Kubernetes objects:
- ClusterRole or Role: defines a set of resource types and operations that can be assigned to a user or group of users in a cluster (ClusterRole), or a Namespace (Role), but does not specify the user or group of users.
- ClusterRoleBinding or RoleBinding: assigns a ClusterRole or Role to a user or group of users. A ClusterRoleBinding works with a ClusterRole, and a RoleBinding works with either a ClusterRole or a Role.
RBAC roles are purely additive--there are no "deny" rules. When structuring your RBAC roles, you should think in terms of "granting" users access to cluster resources.
Defining Permissions using Roles or ClusterRoles
You define permissions within a Role or ClusterRole object. A Role defines access to resources within a single Namespace, while a ClusterRole defines access to resources in the entire cluster.
Roles and ClusterRoles have the same syntax. Each has a
rules section, where
you define the relevant Namespace, resource type, and allowable operations for
the Role. For example, the following Role grants read access (
list) for all Pods in the
kind: Role apiVersion: rbac.authorization.k8s.io/v1 metadata: namespace: accounting name: pod-reader rules: - apiGroups: [""] # "" indicates the core API group resources: ["pods"] verbs: ["get", "watch", "list"]
Because permissions granted by a ClusterRole apply across the entire cluster, you can use ClusterRoles to control access to different kinds of resources than you can with Roles. These include:
- Cluster-scoped resources such as Nodes
- Non-resource Endpoints such as
- Namespaced resources across all Namespaces (for example, all Pods across the entire cluster, regardless of Namespace)
Assigning Roles using RoleBindings or ClusterRoleBindings
After creating a Role or ClusterRole, you assign it to a user or group of users
by creating a RoleBinding or ClusterRoleBinding. Users and groups are called
subjects, and can be any of the following:
|Subject type||Value for
|Google Cloud user account||
||Google Cloud registered email address|
|Kubernetes service account||
||The name of a Kubernetes ServiceAccount object in the cluster|
|Cloud IAM service account||
||Automatically generated Cloud IAM service account email address|
|G Suite Google Group address (Beta) on a verified domain||
||Email address of a Google Group that is itself a member of the Google Group gke-security-groups@[yourdomain.com]|
The following RoleBinding grants the
pod-reader Role to a user, a
Kubernetes service account, a Cloud IAM service account, and a Google
kind: RoleBinding apiVersion: rbac.authorization.k8s.io/v1 metadata: name: pod-reader-binding namespace: accounting subjects: # Google Cloud user account - kind: User name: firstname.lastname@example.org # Kubernetes service account - kind: ServiceAccount name: johndoe # Cloud IAM service account - kind: User name: email@example.com # G Suite Google Group - kind: Group name: firstname.lastname@example.org roleRef: kind: Role name: pod-reader apiGroup: rbac.authorization.k8s.io
API Usage and Examples
For complete information on using the Kubernetes API to create the necessary
ClusterRoleBinding objects for
RBAC, see Using Role-Based Access Control Authorization
in the Kubernetes documentation.
The following sections describe interactions that might not seem obvious when working with Kubernetes RBAC.
Default discovery roles
Clusters are created with a set of
default ClusterRoles and ClusterRoleBindings.
Requests made with valid credentials are placed in the
group, whereas all other requests fall into
Prior to Kubernetes version 1.14, both
system:unauthenticated grant the
ClusterRoles by default.
system:basic-user ClusterRole allows users to make
SelfSubjectAccessReviews to test their permissions in the cluster. The
system:discovery role allows users to read discovery APIs, which can reveal
added to the cluster.
As of Kubernetes 1.14, anonymous users (
system:unauthenticated) will receive
system:basic-info-viewer ClusterRole instead, which grants read-only
To see the API endpoints allowed by the
system:discovery ClusterRole, run the
kubectl get clusterroles system:discovery -o yaml
Forbidden error for service accounts on Google Cloud VM instances
This error can occur when the VM instance does not have the userinfo-email scope. For example, suppose the VM has cloud-platform scope but does not have userinfo-email scope. When the VM gets an access token, Google Cloud associates that token with the cloud-platform scope. When the Kubernetes API server asks Google Cloud for the identity associated with the access token, it receives the service account's unique ID, not the service account's email.
To authenticate successfully, either create a new VM with the userinfo-email scope or create a new role binding that uses the unique ID.
To create a new VM with the userinfo-email scope, run the following command:
gcloud compute instances create [INSTANCE_NAME] \ --service-account [SERVICE_ACCOUNT_EMAIL] \ --scopes userinfo-email
To create a new role binding that uses the service account's unique ID for an existing VM, perform the following steps:
Identify the service account's unique ID:
gcloud iam service-accounts describe [SERVICE_ACCOUNT_EMAIL]
Create a role binding using the unique ID:
kubectl create clusterrolebinding [CLUSTERROLEBINDING_NAME] \ --clusterrole cluster-admin \ --user [UNIQUE_ID]