Add docs for Multi-Tenancy

docs/multi-tenancy.md

@@ -0,0 +1,111 @@
+# Multi Tenancy
+
+Fleet uses Kubernetes RBAC where possible.
+
+One addition on top of RBAC is the [`GitRepoRestriction`](namespaces#restricting-gitrepos) resource, which can be used to control GitRepo resources in a namespace.
+
+A multi-tenant fleet setup looks like this:
+
+* tenants don't share namespaces, each tenant has one or more namespaces on the
+  upstream cluster, where they can create GitRepo resources
+* tenants can deploy cluster wide resources and are limited to a set of
+  namespaces on downstream clusters
+* clusters are in a separate namespace
+
+## Example Tenant
+
+This would create a user 'fleetuser', who can only manage GitRepo resources in the 'project1' namespace.
+
+    kubectl create serviceaccount fleetuser
+    kubectl create namespace project1
+    kubectl create -n project1 role fleetuser --verb=get --verb=list --verb=create --verb=delete --resource=gitrepos.fleet.cattle.io
+    kubectl create -n project1 rolebinding fleetuser --serviceaccount=default:fleetuser --role=fleetuser
+
+If we want to give access to multiple namespaces, we can use a single cluster role with two role bindings:
+
+    kubectl create clusterrole fleetuser --verb=get --verb=list --verb=create --verb=delete --resource=gitrepos.fleet.cattle.io
+    kubectl create -n project1 rolebinding fleetuser --serviceaccount=default:fleetuser --clusterrole=fleetuser
+    kubectl create -n project2 rolebinding fleetuser --serviceaccount=default:fleetuser --clusterrole=fleetuser
+
+This makes sure, tenants can't interfere with GitRepo resources from other tenants, since they don't have access to their namespaces.
+
+## Allow Access to Clusters
+
+This assumes all GitRepos created by 'fleetuser' have the `team: one` label. Different labels could be used, to select different cluster namespaces.
+
+In each of the user's namespaces, as an admin create a [`BundleNamespaceMapping`](./namespaces#cross-namespace-deployments).
+
+    kind: BundleNamespaceMapping
+    apiVersion: fleet.cattle.io/v1alpha1
+    metadata:
+      name: mapping
+      namespace: project1
+
+    # Bundles to match by label.
+    # The labels are defined in the fleet.yaml # labels field or from the
+    # GitRepo metadata.labels field
+    bundleSelector:
+      matchLabels:
+        team: one
+        # or target one repo
+        #fleet.cattle.io/repo-name: simpleapp
+
+    # Namespaces containing clusters to match by label
+    namespaceSelector:
+      matchLabels:
+        kubernetes.io/metadata.name: fleet-default
+        # or clusters in every namespace with a label
+        #workspace: prod
+
+The [`target` section](./gitrepo-targets) in the GitRepo resource can be used to deploy only to a subset of the matched clusters.
+
+## Restricting Access to Downstream Clusters
+
+Admins can further restrict tenants by creating a `GitRepoRestriction` in each of their namespaces.
+
+    kind: GitRepoRestriction
+    apiVersion: fleet.cattle.io/v1alpha1
+    metadata:
+      name: restriction
+      namespace: project1
+
+    allowedTargetNamespaces:
+      - project1simpleapp
+
+This will deny the creation of cluster wide resources, which may interfere with other tenants and limit th deployment to the 'project1simpleapp' namespace.
+
+## An Example GitRepo Resource
+
+A GitRepo resource create by a tenant, without admin access could look like this:
+
+    kind: GitRepo
+    apiVersion: fleet.cattle.io/v1alpha1
+    metadata:
+      name: simpleapp
+      namespace: project1
+      labels:
+        team: one
+
+    spec:
+      repo: https://github.com/rancher/fleet-examples
+      paths:
+      - bundle-diffs
+
+      targetNamespace: project1simpleapp
+
+      # do not match the upstream/local cluster, won't work
+      targets:
+      - name: dev
+        clusterSelector:
+          matchLabels:
+            env: dev
+
+This includes the `team: one` label and and the required `targetNamespace`.
+
+Together with the previous `BundleNamespaceMapping` it would target all clusters with a `env: dev` label in the 'fleet-default' namespace.
+
+:::note
+
+`BundleNamespaceMappings` do not work with local clusters, so make sure not to target them.
+
+:::

docs/namespaces.md

@@ -103,6 +103,15 @@ spec:
   allowedClientSecretNames: []
   allowedRepoPatterns: []
   allowedServiceAccounts: []
+  allowedTargetNamespaces: []
   defaultClientSecretName: ""
   defaultServiceAccount: ""
 ```
+
+### AllowedTargetNamespaces
+
+This can be used to limit a deployment to a set of namespaces on a downstream cluster.
+If an allowedTargetNamespaces restriction is present, all `GitRepos` must
+specify a `targetNamespace` and the specified namespace must be in the allow
+list.
+This also prevents the creation of cluster wide resources.

sidebars.js

@@ -26,6 +26,7 @@ module.exports = {
           ],
         },
         'namespaces',
+        'multi-tenancy',
       ],
     },
     {