877 allow controller to use token (#885)

* adding readme

* Support setting env variable for bearer token

* Revert "adding readme"

This reverts commit 6ed2ef2.

* formatting

* Delete glide.yaml

Now Gopkg.toml is used instead

* Remove description for CRDs (#887)

* Remove description for CRDs

* Update docs

* Adapt kafka manifest

* Renaming GetOverriddenClientConfig to GetInClusterConfig, removing redundant error handler for getting config

* adding readme

* Support setting env variable for bearer token

* Revert "adding readme"

This reverts commit 6ed2ef2.

* formatting

* Renaming GetOverriddenClientConfig to GetInClusterConfig, removing redundant error handler for getting config

* Adding docs for KUBELESS_TOKEN_FILE_PATH

* Fix format

cmd/function-controller/function-controller.go

@@ -31,7 +31,6 @@ import (
 	"github.com/kubeless/kubeless/pkg/version"
 	"github.com/sirupsen/logrus"
 	"github.com/spf13/cobra"
-	"k8s.io/client-go/rest"
 )
 
 const (
@@ -53,7 +52,7 @@ var rootCmd = &cobra.Command{
 			FunctionClient: kubelessClient,
 		}
 
-		restCfg, err := rest.InClusterConfig()
+		restCfg, err := utils.GetInClusterConfig()
 		if err != nil {
 			logrus.Fatalf("Cannot get REST client: %v", err)
 		}

docs/function-controller-configuration.md

@@ -228,4 +228,35 @@ It is possible to configure the different images that Kubeless uses for deploy a
   - (Optional) Image Pull Secrets: Secret required to pull the image in case the repository is private.
  - The image used to populate the base image with the function. This is called `provision-image`. This image should have at least `unzip` and `curl`. It is also possible to specify `provision-image-secret` to specify a secret to pull that image from a private registry. 
  - The image used to build function images. This is called `builder-image`. This image is optional since its usage can be disabled with the property `enable-build-step`. A Dockerfile to build this image can be found [here](https://github.com/kubeless/kubeless/tree/master/docker/function-image-builder). It is also possible to specify `builder-image-secret` to specify a secret to pull that image from a private registry.
-
+
+## Authenticate Kubeless Function Controller using OAuth Bearer Token
+
+In some non-RBAC k8s deployments using webhook authorization, service accounts may have insufficient privileges to perform all k8s operations that the Kubeless Function Controller requires for interacting with the cluster. It's possible to override the default behavior of the Kubeless Function Controller using a k8s serviceaccount for authentication with the cluster and instead use a provided OAuth Bearer token for all k8s operations. 
+
+This can be done by creating a k8s secret and mounting that secret as a volume on controller pods, then setting the environmental variable `KUBELESS_TOKEN_FILE_PATH` to the filepath of that secret. Be sure to set this environmental variable on the controller template spec or to every pod created in the deployment.
+
+For example, if the bearer token is mounted at /mnt/secrets/bearer-token, this k8s spec can use it:
+
+```yaml
+# Kubeless core controller
+---
+apiVersion: apps/v1beta1
+kind: Deployment
+metadata:
+  name: kubeless-controller-manager
+  namespace: kubeless
+  labels:
+    kubeless: controller
+spec:
+  template:
+    metadata:
+      labels:
+        kubeless: controller
+    spec:
+      containers:
+      - env:
+        - name: KUBELESS_TOKEN_FILE_PATH
+          value: /mnt/secrets/bearer-token
+  ... # The rest of the Deployment has been omitted
+```
+

pkg/utils/k8sutil.go

@@ -56,7 +56,7 @@ const (
 
 // GetClient returns a k8s clientset to the request from inside of cluster
 func GetClient() kubernetes.Interface {
-	config, err := rest.InClusterConfig()
+	config, err := GetInClusterConfig()
 	if err != nil {
 		logrus.Fatalf("Can not get kubernetes config: %v", err)
 	}
@@ -123,7 +123,8 @@ func GetAPIExtensionsClientOutOfCluster() clientsetAPIExtensions.Interface {
 
 // GetAPIExtensionsClientInCluster returns a k8s clientset to access APIExtensions from inside of cluster
 func GetAPIExtensionsClientInCluster() clientsetAPIExtensions.Interface {
-	config, err := rest.InClusterConfig()
+	config, err := GetInClusterConfig()
+
 	if err != nil {
 		logrus.Fatalf("Can not get kubernetes config: %v", err)
 	}
@@ -136,10 +137,11 @@ func GetAPIExtensionsClientInCluster() clientsetAPIExtensions.Interface {
 
 // GetFunctionClientInCluster returns function clientset to the request from inside of cluster
 func GetFunctionClientInCluster() (versioned.Interface, error) {
-	config, err := rest.InClusterConfig()
+	config, err := GetInClusterConfig()
 	if err != nil {
 		return nil, err
 	}
+
 	kubelessClient, err := versioned.NewForConfig(config)
 	if err != nil {
 		return nil, err

pkg/utils/kubelessutil.go

@@ -31,6 +31,7 @@ import (
 	kubelessApi "github.com/kubeless/kubeless/pkg/apis/kubeless/v1beta1"
 	"github.com/kubeless/kubeless/pkg/langruntime"
 	"github.com/sirupsen/logrus"
+	"io/ioutil"
 	batchv1 "k8s.io/api/batch/v1"
 	"k8s.io/api/core/v1"
 	"k8s.io/api/extensions/v1beta1"
@@ -40,6 +41,7 @@ import (
 	"k8s.io/apimachinery/pkg/types"
 	"k8s.io/apimachinery/pkg/util/intstr"
 	"k8s.io/client-go/kubernetes"
+	"k8s.io/client-go/rest"
 )
 
 // GetFunctionPort returns the port for a function service
@@ -760,6 +762,23 @@ func GetOwnerReference(kind, apiVersion, name string, uid types.UID) ([]metav1.O
 	}, nil
 }
 
+// GetInClusterConfig returns necessary Config object to authenticate k8s clients if env variable is set
+func GetInClusterConfig() (*rest.Config, error) {
+	config, err := rest.InClusterConfig()
+
+	tokenFile := os.Getenv("KUBELESS_TOKEN_FILE_PATH")
+	if len(tokenFile) == 0 {
+		return config, err
+	}
+	tokenBytes, err := ioutil.ReadFile(tokenFile)
+	if err != nil {
+		return nil, fmt.Errorf("unable to read file containing oauth token: %s", err)
+	}
+	config.BearerToken = string(tokenBytes)
+
+	return config, nil
+}
+
 func getConfigLocation(apiExtensionsClientset clientsetAPIExtensions.Interface) (ConfigLocation, error) {
 	configLocation := ConfigLocation{}
 	controllerNamespace := os.Getenv("KUBELESS_NAMESPACE")