Within workspaces, KCP implements the same RBAC-based authorization mechanism as Kubernetes. Other authorization schemes (i.e. ABAC) are not supported. Generally, the same (cluster) role and (cluster) role binding principles apply exactly as in Kubernetes.
In addition, additional RBAC semantics is implemented cross-workspaces, namely the following:
- Top-Level Organization access: the user must have this as pre-requisite to access any other workspace, or is even member and by that can create workspaces inside the organization workspace.
- Workspace Content access: the user needs access to a workspace or is even admin.
- for some resources, additional permission checks are performed, not represented by local or Kubernetes standard RBAC rules. E.g.
- workspace creation checks for organization membership (see above).
- workspace creation checks for
useverb on the
- API binding via APIBinding objects requires verb
bindaccess to the corresponding
- System Workspaces access: system workspaces are prefixed with
system:and are not accessible by users.
The details are outlined below.
The following authorizers are configured in kcp:
|Top-Level organization authorizer||checks that the user is allowed to access the organization|
|Workspace content authorizer||determines additional groups a user gets inside of a workspace|
|Maximal permission policy authorizer||validates the maximal permission policy RBAC policy in the API exporter workspace|
|Local Policy authorizer||validates the RBAC policy in the workspace that is accessed|
|Kubernetes Bootstrap Policy authorizer||validates the RBAC Kubernetes standard policy|
They are related in the following way:
- top-level organization authorizer must allow
- workspace content authorizer must allow, and adds additional (virtual per-request) groups to the request user influencing the follow authorizers.
- maximal permission policy authorizer must allow
- one of the local authorizer or bootstrap policy authorizer must allow.
┌──────────────┐ │ │ ┌────►│ Local Policy ├──┐ ┌──────────────┐ ┌──────────────┐ ┌───────────────────┐ │ │ authorizer │ │ request │ Workspace │ │ Required │ │ Max. Permission │ │ │ │ │ ─────────►│ Content ├────►│ Groups ├────┤ Policy authorizer ├───┤ └──────────────┘ │ │ Authorizer │ │ Authorizer │ │ │ │ ▼ └──────────────┘ └──────────────┘ └───────────────────┘ │ OR───► │ ┌──────────────┐ ▲ │ │ Bootstrap │ │ └────►│ Policy ├──┘ │ authorizer │ │ │ └──────────────┘
Workspace Content authorizer
The workspace content authorizer checks whether the user is granted access to the workspace.
Access is granted access through
verb=access non-resource permission to
/ inside of the workspace.
system:kcp:workspace:access is pre-defined which makes it easy
to give a user access through a ClusterRoleBinding inside of the workspace.
For example, to give a user
user1 access, create the following ClusterRoleBinding:
To give a user
user1 admin access, create the following ClusterRoleBinding:
A service-account defined in a workspace implicitly is granted access to it.
A service-account defined in a differant workspace is NOT given access to it.
Required Groups Authorizer
authorization.kcp.io/required-groups annotation can be added to a LogicalCluster
to specify additional groups that are required to access a workspace for a user to be member of.
The syntax is a disjunction (separator
,) of conjunctions (separator
<group1>;<group2>,<group3> means that a user must be member of
<group2>, OR of
The annotation is copied onto sub-workspaces during scheduling.
By default, workspaces are only accessible to a user if they are in
Ready phase. Workspaces that are initializing
can be access only by users that are granted
admin verb on the
workspaces/content resource in the
Service accounts declared within a workspace don't have access to initializing workspaces.
Maximal permission policy authorizer
If the requested resource type is part of an API binding, then this authorizer verifies that the request is not exceeding the maximum permission policy of the related API export. Currently, the "local policy" maximum permission policy type is supported.
The local maximum permission policy delegates the decision to the RBAC of the related API export.
To distinguish between local RBAC role bindings in that workspace and those for this these maximum permission policy,
every name and group is prefixed with
Given an API binding for type
foo declared in workspace
consumer that refers to an API export declared in workspace
and a user
user-1 having the group
group-1 requesting a
foo in the
default namespace in the
this authorizer verifies that
user-1 is allowed to execute this request by delegating to
provider's RBAC using prefixed attributes.
Here, this authorizer prepends the
apis.kcp.io:binding: prefix to the username and all groups the user belongs to.
Using prefixed attributes prevents RBAC collisions i.e. if
user-1 is granted to execute requests within the
provider workspace directly.
For the given example RBAC request looks as follows:
The following role and role binding declared within the
provider workspace will grant access to the request:
apiVersion: rbac.authorization.k8s.io/v1 kind: Role metadata: name: foo-creator clusterName: provider rules: - apiGroups: - foo.api resources: - foos verbs: - create --- apiVersion: rbac.authorization.k8s.io/v1 kind: RoleBinding metadata: name: user-1-foo-creator namespace: default clusterName: provider subjects: - kind: User name: apis.kcp.io:binding:user-1 roleRef: apiGroup: rbac.authorization.k8s.io kind: Role name: foo-creator
The same authorization scheme is enforced when executing the request of a claimed resource via the virtual API Export API server, i.e. a claimed resource is bound to the same maximal permission policy. Only the actual owner of that resources can go beyond that policy.
Kubernetes Bootstrap Policy authorizer
The bootstrap policy authorizer works just like the local authorizer but references RBAC rules
defined in the
system:admin system workspace.
Local Policy authorizer
Once the top-level organization authorizer and the workspace content authorizer granted access to a workspace, RBAC rules contained in the workspace derived from the request context are evaluated.
This authorizer ensures that RBAC rules contained within a workspace are being applied and work just like in a regular Kubernetes cluster.
Groups added by the workspace content authorizer can be used for role bindings in that workspace.
It is possible to bind to roles and cluster roles in the bootstrap policy from a local policy
Kubernetes service accounts are granted access to the workspaces they are defined in and that are ready.
E.g. a service account "default" in
root:org:ws:ws is granted access to
root:org:ws:ws, and through the
workspace content authorizer it gains the
system:kcp:clusterworkspace:access group membership.