Tolerate lack of namespace permissions in RBAC reconciliation

This change updates the RBAC reconciliation logic to not fail if the
user does not have the ability to create namespaces.  Thus if the
namespace already exists, the user only needs to pass the standard
escalation check for RBAC roles and role bindings.

Signed-off-by: Monis Khan <mkhan@redhat.com>

pkg/registry/rbac/reconciliation/BUILD

@@ -26,6 +26,7 @@ go_library(
     srcs = [
         "clusterrole_interfaces.go",
         "clusterrolebinding_interfaces.go",
+        "namespace.go",
         "reconcile_role.go",
         "reconcile_rolebindings.go",
         "role_interfaces.go",
@@ -42,6 +43,7 @@ go_library(
         "//staging/src/k8s.io/apimachinery/pkg/apis/meta/v1:go_default_library",
         "//staging/src/k8s.io/apimachinery/pkg/runtime:go_default_library",
         "//staging/src/k8s.io/apimachinery/pkg/types:go_default_library",
+        "//staging/src/k8s.io/apimachinery/pkg/util/errors:go_default_library",
         "//staging/src/k8s.io/client-go/kubernetes/typed/core/v1:go_default_library",
         "//staging/src/k8s.io/client-go/kubernetes/typed/rbac/v1:go_default_library",
     ],

pkg/registry/rbac/reconciliation/namespace.go

@@ -0,0 +1,44 @@
+/*
+Copyright 2018 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package reconciliation
+
+import (
+	corev1 "k8s.io/api/core/v1"
+	apierrors "k8s.io/apimachinery/pkg/api/errors"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	utilerrors "k8s.io/apimachinery/pkg/util/errors"
+	corev1client "k8s.io/client-go/kubernetes/typed/core/v1"
+)
+
+// tryEnsureNamespace gets or creates the given namespace while ignoring forbidden errors.
+// It is a best effort attempt as the user may not be able to get or create namespaces.
+// This allows us to handle flows where the user can only mutate roles and role bindings.
+func tryEnsureNamespace(client corev1client.NamespaceInterface, namespace string) error {
+	_, getErr := client.Get(namespace, metav1.GetOptions{})
+	if getErr == nil {
+		return nil
+	}
+
+	if fatalGetErr := utilerrors.FilterOut(getErr, apierrors.IsNotFound, apierrors.IsForbidden); fatalGetErr != nil {
+		return fatalGetErr
+	}
+
+	ns := &corev1.Namespace{ObjectMeta: metav1.ObjectMeta{Name: namespace}}
+	_, createErr := client.Create(ns)
+
+	return utilerrors.FilterOut(createErr, apierrors.IsAlreadyExists, apierrors.IsForbidden)
+}

pkg/registry/rbac/reconciliation/role_interfaces.go

@@ -17,9 +17,7 @@ limitations under the License.
 package reconciliation
 
 import (
-	corev1 "k8s.io/api/core/v1"
 	rbacv1 "k8s.io/api/rbac/v1"
-	apierrors "k8s.io/apimachinery/pkg/api/errors"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/apimachinery/pkg/runtime"
 	corev1client "k8s.io/client-go/kubernetes/typed/core/v1"
@@ -90,8 +88,7 @@ func (c RoleModifier) Get(namespace, name string) (RuleOwner, error) {
 }
 
 func (c RoleModifier) Create(in RuleOwner) (RuleOwner, error) {
-	ns := &corev1.Namespace{ObjectMeta: metav1.ObjectMeta{Name: in.GetNamespace()}}
-	if _, err := c.NamespaceClient.Create(ns); err != nil && !apierrors.IsAlreadyExists(err) {
+	if err := tryEnsureNamespace(c.NamespaceClient, in.GetNamespace()); err != nil {
 		return nil, err
 	}
 

pkg/registry/rbac/reconciliation/rolebinding_interfaces.go

@@ -17,9 +17,7 @@ limitations under the License.
 package reconciliation
 
 import (
-	corev1 "k8s.io/api/core/v1"
 	rbacv1 "k8s.io/api/rbac/v1"
-	apierrors "k8s.io/apimachinery/pkg/api/errors"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/apimachinery/pkg/runtime"
 	"k8s.io/apimachinery/pkg/types"
@@ -92,8 +90,7 @@ func (c RoleBindingClientAdapter) Get(namespace, name string) (RoleBinding, erro
 }
 
 func (c RoleBindingClientAdapter) Create(in RoleBinding) (RoleBinding, error) {
-	ns := &corev1.Namespace{ObjectMeta: metav1.ObjectMeta{Name: in.GetNamespace()}}
-	if _, err := c.NamespaceClient.Create(ns); err != nil && !apierrors.IsAlreadyExists(err) {
+	if err := tryEnsureNamespace(c.NamespaceClient, in.GetNamespace()); err != nil {
 		return nil, err
 	}