Merge pull request #40698 from luxas/kubeadm_fix_authz_default

Automatic merge from submit-queue (batch tested with PRs 40707, 40698)

kubeadm: Default to control plane v1.6.0-alpha.1 and using RBAC

Also use constants for authz modes

**What this PR does / why we need it**:

Defaults to v1.6.0-alpha.1 (will be cut later today) because the certificates API group has been upgraded to beta, so `kubeadm join` at HEAD doesn't work on a `v1.5` cluster anyway.

By defaulting to v1.6.0-alpha.1, we can focus totally on v1.6 for kubeadm at HEAD, we don't support other versions in the upcoming v1.6 kubeadm release because of the alpha -> beta upgrades.

**Which issue this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close that issue when PR gets merged)*: fixes #

**Special notes for your reviewer**:

**Release note**:

```release-note
NONE
```

@mikedanese @pires

cmd/kubeadm/app/apis/kubeadm/v1alpha1/defaults.go

@@ -21,13 +21,12 @@ import "k8s.io/apimachinery/pkg/runtime"
 const (
 	DefaultServiceDNSDomain  = "cluster.local"
 	DefaultServicesSubnet    = "10.96.0.0/12"
-	DefaultKubernetesVersion = "stable"
+	DefaultKubernetesVersion = "latest"
 	// This is only for clusters without internet, were the latest stable version can't be determined
-	DefaultKubernetesFallbackVersion = "v1.5.2"
+	DefaultKubernetesFallbackVersion = "v1.6.0-alpha.1"
 	DefaultAPIBindPort               = 6443
 	DefaultDiscoveryBindPort         = 9898
-	// TODO: Default this to RBAC when DefaultKubernetesFallbackVersion is v1.6-something
-	DefaultAuthorizationMode = "AlwaysAllow"
+	DefaultAuthorizationMode         = "RBAC"
 )
 
 func addDefaultingFuncs(scheme *runtime.Scheme) error {

cmd/kubeadm/app/cmd/defaults.go

@@ -23,14 +23,14 @@ import (
 	netutil "k8s.io/apimachinery/pkg/util/net"
 	kubeadmapi "k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm"
 	kubeadmapiext "k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm/v1alpha1"
+	kubeadmconstants "k8s.io/kubernetes/cmd/kubeadm/app/constants"
 	kubeadmutil "k8s.io/kubernetes/cmd/kubeadm/app/util"
 
 	"github.com/blang/semver"
 )
 
 var (
-	// Maximum version when using AllowAll as the default authz mode. Everything above this will use RBAC by default.
-	allowAllMaxVersion = semver.MustParse("1.6.0-alpha.0")
+	minK8sVersion = semver.MustParse(kubeadmconstants.MinimumControlPlaneVersion)
 )
 
 func setInitDynamicDefaults(cfg *kubeadmapi.MasterConfiguration) error {
@@ -53,16 +53,18 @@ func setInitDynamicDefaults(cfg *kubeadmapi.MasterConfiguration) error {
 		}
 	}
 	cfg.KubernetesVersion = ver
-	fmt.Println("[init] Using Kubernetes version:", ver)
 
 	// Omit the "v" in the beginning, otherwise semver will fail
-	// If the version is newer than the specified version, RBAC v1beta1 support is enabled in the apiserver so we can default to RBAC
 	k8sVersion, err := semver.Parse(cfg.KubernetesVersion[1:])
-	if k8sVersion.GT(allowAllMaxVersion) {
-		cfg.AuthorizationMode = "RBAC"
+	if err != nil {
+		return fmt.Errorf("couldn't parse kubernetes version %q: %v", cfg.KubernetesVersion, err)
+	}
+	if k8sVersion.LT(minK8sVersion) {
+		return fmt.Errorf("this version of kubeadm only supports deploying clusters with the control plane version >= v1.6.0-alpha.1. Current version: %s", cfg.KubernetesVersion)
 	}
 
-	fmt.Println("[init] Using Authorization mode:", cfg.AuthorizationMode)
+	fmt.Printf("[init] Using Kubernetes version: %s\n", cfg.KubernetesVersion)
+	fmt.Printf("[init] Using Authorization mode: %s\n", cfg.AuthorizationMode)
 
 	// Warn about the limitations with the current cloudprovider solution.
 	if cfg.CloudProvider != "" {

cmd/kubeadm/app/cmd/init.go

@@ -30,6 +30,7 @@ import (
 	kubeadmapiext "k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm/v1alpha1"
 	"k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm/validation"
 	"k8s.io/kubernetes/cmd/kubeadm/app/cmd/flags"
+	kubeadmconstants "k8s.io/kubernetes/cmd/kubeadm/app/constants"
 	"k8s.io/kubernetes/cmd/kubeadm/app/discovery"
 	kubemaster "k8s.io/kubernetes/cmd/kubeadm/app/master"
 	"k8s.io/kubernetes/cmd/kubeadm/app/phases/apiconfig"
@@ -219,7 +220,7 @@ func (i *Init) Run(out io.Writer) error {
 		return err
 	}
 
-	if i.cfg.AuthorizationMode == "RBAC" {
+	if i.cfg.AuthorizationMode == kubeadmconstants.AuthzModeRBAC {
 		err = apiconfig.CreateBootstrapRBACClusterRole(client)
 		if err != nil {
 			return err

cmd/kubeadm/app/constants/constants.go

@@ -28,4 +28,15 @@ const (
 	APIServerKubeletClientCertAndKeyBaseName = "apiserver-kubelet-client"
 	APIServerKubeletClientCertName           = "apiserver-kubelet-client.crt"
 	APIServerKubeletClientKeyName            = "apiserver-kubelet-client.key"
+
+	// TODO: These constants should actually come from pkg/kubeapiserver/authorizer, but we can't vendor that package in now
+	// because of all the other sub-packages that would get vendored. To fix this, a pkg/kubeapiserver/authorizer/modes package
+	// or similar should exist that only has these constants; then we can vendor it.
+	AuthzModeAlwaysAllow = "AlwaysAllow"
+	AuthzModeABAC        = "ABAC"
+	AuthzModeRBAC        = "RBAC"
+	AuthzModeWebhook     = "Webhook"
+
+	// Important: a "v"-prefix shouldn't exist here; semver doesn't allow that
+	MinimumControlPlaneVersion = "1.6.0-alpha.1"
 )

cmd/kubeadm/app/master/BUILD

@@ -31,7 +31,6 @@ go_library(
         "//pkg/client/clientset_generated/clientset:go_default_library",
         "//pkg/kubectl/cmd/util:go_default_library",
         "//pkg/registry/core/service/ipallocator:go_default_library",
-        "//vendor:github.com/blang/semver",
         "//vendor:k8s.io/apimachinery/pkg/api/errors",
         "//vendor:k8s.io/apimachinery/pkg/api/resource",
         "//vendor:k8s.io/apimachinery/pkg/apis/meta/v1",

cmd/kubeadm/app/master/manifests.go

@@ -32,8 +32,6 @@ import (
 	"k8s.io/kubernetes/cmd/kubeadm/app/images"
 	api "k8s.io/kubernetes/pkg/api/v1"
 	cmdutil "k8s.io/kubernetes/pkg/kubectl/cmd/util"
-
-	"github.com/blang/semver"
 )
 
 // Static pod definitions in golang form are included below so that `kubeadm init` can get going.
@@ -54,14 +52,6 @@ const (
 	authorizationWebhookConfigFile = "webhook_authz.conf"
 )
 
-var (
-	// Minimum version of kube-apiserver that supports --kubelet-preferred-address-types
-	preferredAddressAPIServerMinVersion = semver.MustParse("1.5.0")
-
-	// Minimum version of kube-apiserver that has to have --anonymous-auth=false set
-	anonAuthDisableAPIServerMinVersion = semver.MustParse("1.5.0")
-)
-
 // WriteStaticPodManifests builds manifest objects based on user provided configuration and then dumps it to disk
 // where kubelet will pick and schedule them.
 func WriteStaticPodManifests(cfg *kubeadmapi.MasterConfiguration) error {
@@ -328,14 +318,15 @@ func getAPIServerCommand(cfg *kubeadmapi.MasterConfiguration, selfHosted bool) [
 		fmt.Sprintf("--secure-port=%d", cfg.API.Port),
 		"--allow-privileged",
 		"--storage-backend=etcd3",
+		"--kubelet-preferred-address-types=InternalIP,ExternalIP,Hostname",
 	)
 
 	if cfg.AuthorizationMode != "" {
 		command = append(command, "--authorization-mode="+cfg.AuthorizationMode)
 		switch cfg.AuthorizationMode {
-		case "ABAC":
+		case kubeadmconstants.AuthzModeABAC:
 			command = append(command, "--authorization-policy-file="+path.Join(kubeadmapi.GlobalEnvParams.KubernetesDir, authorizationPolicyFile))
-		case "Webhook":
+		case kubeadmconstants.AuthzModeWebhook:
 			command = append(command, "--authorization-webhook-config-file="+path.Join(kubeadmapi.GlobalEnvParams.KubernetesDir, authorizationWebhookConfigFile))
 		}
 	}
@@ -349,23 +340,6 @@ func getAPIServerCommand(cfg *kubeadmapi.MasterConfiguration, selfHosted bool) [
 		}
 	}
 
-	if len(cfg.KubernetesVersion) != 0 {
-		// If the k8s version is v1.5-something, this argument is set and makes `kubectl logs` and `kubectl exec`
-		// work on bare-metal where hostnames aren't usually resolvable
-		// Omit the "v" in the beginning, otherwise semver will fail
-		k8sVersion, err := semver.Parse(cfg.KubernetesVersion[1:])
-
-		// If the k8s version is greater than this version, it supports telling it which way it should contact kubelets
-		if err == nil && k8sVersion.GTE(preferredAddressAPIServerMinVersion) {
-			command = append(command, "--kubelet-preferred-address-types=InternalIP,ExternalIP,Hostname")
-		}
-
-		// This is a critical "bugfix". Any version above this is vulnerable unless a RBAC/ABAC-authorizer is provided (which kubeadm doesn't for the time being)
-		if err == nil && k8sVersion.GTE(anonAuthDisableAPIServerMinVersion) {
-			command = append(command, "--anonymous-auth=false")
-		}
-	}
-
 	// Check if the user decided to use an external etcd cluster
 	if len(cfg.Etcd.Endpoints) > 0 {
 		command = append(command, fmt.Sprintf("--etcd-servers=%s", strings.Join(cfg.Etcd.Endpoints, ",")))

cmd/kubeadm/app/master/manifests_test.go

@@ -382,6 +382,7 @@ func TestGetAPIServerCommand(t *testing.T) {
 				fmt.Sprintf("--secure-port=%d", 123),
 				"--allow-privileged",
 				"--storage-backend=etcd3",
+				"--kubelet-preferred-address-types=InternalIP,ExternalIP,Hostname",
 				"--etcd-servers=http://127.0.0.1:2379",
 			},
 		},
@@ -405,6 +406,7 @@ func TestGetAPIServerCommand(t *testing.T) {
 				fmt.Sprintf("--secure-port=%d", 123),
 				"--allow-privileged",
 				"--storage-backend=etcd3",
+				"--kubelet-preferred-address-types=InternalIP,ExternalIP,Hostname",
 				"--advertise-address=foo",
 				"--etcd-servers=http://127.0.0.1:2379",
 			},
@@ -430,39 +432,12 @@ func TestGetAPIServerCommand(t *testing.T) {
 				fmt.Sprintf("--secure-port=%d", 123),
 				"--allow-privileged",
 				"--storage-backend=etcd3",
+				"--kubelet-preferred-address-types=InternalIP,ExternalIP,Hostname",
 				"--etcd-servers=http://127.0.0.1:2379",
 				"--etcd-certfile=fiz",
 				"--etcd-keyfile=faz",
 			},
 		},
-		// Make sure --kubelet-preferred-address-types
-		{
-			cfg: &kubeadmapi.MasterConfiguration{
-				API:               kubeadm.API{Port: 123, AdvertiseAddresses: []string{"foo"}},
-				Networking:        kubeadm.Networking{ServiceSubnet: "bar"},
-				KubernetesVersion: "v1.5.3",
-			},
-			expected: []string{
-				"kube-apiserver",
-				"--insecure-bind-address=127.0.0.1",
-				"--admission-control=NamespaceLifecycle,LimitRanger,ServiceAccount,PersistentVolumeLabel,DefaultStorageClass,ResourceQuota",
-				"--service-cluster-ip-range=bar",
-				"--service-account-key-file=" + kubeadmapi.GlobalEnvParams.HostPKIPath + "/apiserver.key",
-				"--client-ca-file=" + kubeadmapi.GlobalEnvParams.HostPKIPath + "/ca.crt",
-				"--tls-cert-file=" + kubeadmapi.GlobalEnvParams.HostPKIPath + "/apiserver.crt",
-				"--tls-private-key-file=" + kubeadmapi.GlobalEnvParams.HostPKIPath + "/apiserver.key",
-				"--kubelet-client-certificate=" + kubeadmapi.GlobalEnvParams.HostPKIPath + "/apiserver-kubelet-client.crt",
-				"--kubelet-client-key=" + kubeadmapi.GlobalEnvParams.HostPKIPath + "/apiserver-kubelet-client.key",
-				"--token-auth-file=" + kubeadmapi.GlobalEnvParams.HostPKIPath + "/tokens.csv",
-				fmt.Sprintf("--secure-port=%d", 123),
-				"--allow-privileged",
-				"--storage-backend=etcd3",
-				"--advertise-address=foo",
-				"--kubelet-preferred-address-types=InternalIP,ExternalIP,Hostname",
-				"--anonymous-auth=false",
-				"--etcd-servers=http://127.0.0.1:2379",
-			},
-		},
 	}
 
 	for _, rt := range tests {