RBAC Management

Overview

Role-based access control (RBAC) regulates access to a computer or network resources based on the roles of individual users within your organization.

RBAC authorization uses the rbac.authorization.k8s.io API group to drive authorization decisions, allowing you to configure policies through the Kubernetes API dynamically.

API objects

The RBAC API declares four Kubernetes objects: Role, ClusterRole, RoleBinding and ClusterRoleBinding. You can describe objects, or amend them, using tools such as kubectl, just like any other Kubernetes object.

Role & ClusterRole

An RBAC Role or ClusterRole contains rules that represent a set of permissions. Permissions are purely additive (there are no "deny" rules).

A Role always sets permissions within a particular namespace; when you create a Role, you have to specify the namespace it belongs in.

ClusterRole, by contrast, is a non-namespaced resource. The resources have different names (Role and ClusterRole) because a Kubernetes object always has to be either namespaced or not namespaced; it can't be both.

ClusterRoles have several uses. You can use a ClusterRole to:

1. define permissions on namespaced resources and be granted access within individual namespace(s)

2. define permissions on namespaced resources and be granted access across all namespaces

3. define permissions on cluster-scoped resources

If you want to define a role within a namespace, use a Role; if you want to define a role cluster-wide, use a ClusterRole.

ClusterRole In DIGIT

A ClusterRole can be used to grant the same permissions as a Role. Because ClusterRoles are cluster-scoped, you can also use them to grant access to:

• cluster-scoped resources (like nodes)

• non-resource endpoints (like /healthz)

• namespaced resources (like Pods), across all namespaces

  For example: you can use a ClusterRole to allow a particular user to run kubectl get pods --all-namespaces

Here is the Digit ClusterRole that can be used to grant read access and restricted admin access

apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRole
metadata:
  name: digit-user
rules:
- apiGroups:
  - "extensions"
  resources:
  - deployments
  verbs:
  - patch
- apiGroups:
  - ""
  resources:
  - pods/portforward
  - pods/proxy 
  verbs:
  - create  
  - delete
---  
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRole
metadata:
  name: digit-admin
rules:
- apiGroups:
  - ""
  resources:
  - pods/portforward
  - pods/proxy 
  - pods/exec 
  verbs:
  - create  
  - delete
- apiGroups:
  - "batch"
  resources:
  - jobs 
  verbs:
  - create  
  - update
  - patch
  - list
- apiGroups: 
  - "apps"
  - "extensions"  
  resources: 
  - deployments
  verbs: 
  - patch 
  - get 
  - list
  - update    

RoleBinding & ClusterRoleBinding

A role binding grants the permissions defined in a role to a user or set of users. It holds a list of subjects (users, groups, or service accounts), and a reference to the role being granted. A RoleBinding grants permissions within a specific namespace whereas a ClusterRoleBinding grants that access cluster-wide.

A RoleBinding may reference any Role in the same namespace. Alternatively, a RoleBinding can reference a ClusterRole and bind that ClusterRole to the namespace of the RoleBinding. If you want to bind a ClusterRole to all the namespaces in your cluster, you use a ClusterRoleBinding.

RoleBinding In DIGIT

Here is the Digit rolebinading that we are using to grant access to group

{{- with index .Values "cluster-configs" "rbac" }}
{{- range $idx, $v := . }}                 // These iteration values are defined in the environment file
{{- range $nsidx, $nsval := .namespaces }}  // These iteration values are defined in the environment file 
apiVersion: rbac.authorization.k8s.io/v1
kind: RoleBinding
metadata:
  name: digit-{{ $v.role }}
  namespace: {{ $nsval }}
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: digit-{{ $v.role }}
subjects:
- apiGroup: rbac.authorization.k8s.io
  kind: Group
  name: digit-user        
---
{{- end }}
{{- end }}
{{- end }}

A RoleBinding can also reference a ClusterRole to grant the permissions defined in that ClusterRole to resources inside the RoleBinding's namespace. This kind of reference lets you define a set of common roles across your cluster, and then reuse them within multiple namespaces.

For instance, even though the following RoleBinding refers to a ClusterRole, "dave" (the subject, case sensitive) will only be able to read Secrets in the "development" namespace, because the RoleBinding's namespace (in its metadata) is "development".

Define the RBAC config in the Environment file

You must add a namespace to a role section to grant access to a group of a namespace.

cluster-configs:
  rbac:
    - role: user
      namespaces: [egov] // digit-user ClusterRole would be granted to the playground and egov namespace. 
    - role: admin
      namespaces: [playground,egov]  // digit-admin ClusterRole would be granted to the playground and egov namespace.