Learn more about Kubernetes authorization, including details about creating policies using the supported authorization modules.
In Kubernetes, you must be authenticated (logged in) before your request can be authorized (granted permission to access). For information about authentication, see Accessing Control Overview.
Kubernetes expects attributes that are common to REST API requests. This means that Kubernetes authorization works with existing organization-wide or cloud-provider-wide access control systems which may handle other APIs besides the Kubernetes API.
Kubernetes authorizes API requests using the API server. It evaluates all of the request attributes against all policies and allows or denies the request. All parts of an API request must be allowed by some policy in order to proceed. This means that permissions are denied by default.
(Although Kubernetes uses the API server, access controls and policies that depend on specific fields of specific kinds of objects are handled by Admission Controllers.)
When multiple authorization modules are configured, each is checked in sequence. If any authorizer approves or denies a request, that decision is immediately returned and no other authorizer is consulted. If all modules have no opinion on the request, then the request is denied. A deny returns an HTTP status code 403.
Kubernetes reviews only the following API request attributes:
userstring provided during authentication.
deletecollectionare used for resource requests. To determine the request verb for a resource API endpoint, see Determine the request verb below.
deleteare used for non-resource requests.
deleteverbs, you must provide the resource name.
To determine the request verb for a resource API endpoint, review the HTTP verb used and whether or not the request acts on an individual resource or a collection of resources:
|HTTP verb||request verb|
|GET, HEAD||get (for individual resources), list (for collections)|
|DELETE||delete (for individual resources), deletecollection (for collections)|
Kubernetes sometimes checks authorization for additional permissions using specialized verbs. For example:
podsecuritypoliciesresources in the
clusterrolesresources in the
serviceaccountsin the core API group, and the
rbac.authorization.k8s.ioAPI group to drive authorization decisions, allowing admins to dynamically configure permission policies through the Kubernetes API.
kubectl provides the
auth can-i subcommand for quickly querying the API authorization layer.
The command uses the
SelfSubjectAccessReview API to determine if the current user can perform
a given action, and works regardless of the authorization mode used.
$ kubectl auth can-i create deployments --namespace dev yes $ kubectl auth can-i create deployments --namespace prod no
Administrators can combine this with user impersonation to determine what action other users can perform.
$ kubectl auth can-i list secrets --namespace dev --as dave no
SelfSubjectAccessReview is part of the
authorization.k8s.io API group, which
exposes the API server authorization to external services. Other resources in
this group include:
SubjectAccessReview- Access review for any user, not just the current one. Useful for delegating authorization decisions to the API server. For example, the kubelet and extension API servers use this to determine user access to their own APIs.
SubjectAccessReviewbut restricted to a specific namespace.
SelfSubjectRulesReview- A review which returns the set of actions a user can perform within a namespace. Useful for users to quickly summarize their own access, or for UIs to hide/show actions.
These APIs can be queried by creating normal Kubernetes resources, where the response “status” field of the returned object is the result of the query.
$ kubectl create -f - -o yaml << EOF apiVersion: authorization.k8s.io/v1 kind: SelfSubjectAccessReview spec: resourceAttributes: group: apps resource: deployments verb: create namespace: dev EOF apiVersion: authorization.k8s.io/v1 kind: SelfSubjectAccessReview metadata: creationTimestamp: null spec: resourceAttributes: group: apps resource: deployments namespace: dev verb: create status: allowed: true denied: false
You must include a flag in your policy to indicate which authorization module your policies include:
The following flags can be used:
--authorization-mode=ABACAttribute-Based Access Control (ABAC) mode allows you to configure policies using local files.
--authorization-mode=RBACRole-based access control (RBAC) mode allows you to create and store policies using the Kubernetes API.
--authorization-mode=WebhookWebHook is an HTTP callback mode that allows you to manage authorization using a remote REST endpoint.
--authorization-mode=NodeNode authorization is a special-purpose authorization mode that specifically authorizes API requests made by kubelets.
--authorization-mode=AlwaysDenyThis flag blocks all requests. Use this flag only for testing.
--authorization-mode=AlwaysAllowThis flag allows all requests. Use this flag only if you do not require authorization for your API requests.
You can choose more than one authorization module. Modules are checked in order so an earlier module has higher priority to allow or deny a request.
Users who have the ability to create pods in a namespace can potentially escalate their privileges within that namespace. They can create pods that access their privileges within that namespace. They can create pods that access secrets the user cannot themselves read, or that run under a service account with different/greater permissions.
Caution: System administrators, use care when granting access to pod creation. A user granted permission to create pods (or controllers that create pods) in the namespace can: read all secrets in the namespace; read all config maps in the namespace; and impersonate any service account in the namespace and take any action the account could take. This applies regardless of authorization mode.
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