cmd/*: fail on unrecognized flags/arguments for component CLI

In case a malformed flag is passed to k8s components
such as "–foo", where "–" is not an ASCII dash character,
the components currently silently ignore the flag
and treat it as a positional argument.

Make k8s components/commands exit with an error if a positional argument
that is not empty is found. Include a custom error message for all
components except kubeadm, as cobra.NoArgs is used in a lot of
places already (can be fixed in a followup).

The kubelet already handles this properly - e.g.:
'unknown command: "–foo"'

This change affects:
- cloud-controller-manager
- kube-apiserver
- kube-controller-manager
- kube-proxy
- kubeadm {alpha|config|token|version}
- kubemark

Signed-off-by: Monis Khan <mok@vmware.com>
Signed-off-by: Lubomir I. Ivanov <lubomirivanov@vmware.com>

cmd/cloud-controller-manager/app/controllermanager.go

@@ -80,6 +80,14 @@ the cloud specific control loops shipped with Kubernetes.`,
 			}
 
 		},
+		Args: func(cmd *cobra.Command, args []string) error {
+			for _, arg := range args {
+				if len(arg) > 0 {
+					return fmt.Errorf("%q does not take any arguments, got %q", cmd.CommandPath(), args)
+				}
+			}
+			return nil
+		},
 	}
 
 	fs := cmd.Flags()

cmd/kube-apiserver/app/server.go

@@ -117,6 +117,14 @@ cluster's shared state through which all other components interact.`,
 
 			return Run(completedOptions, genericapiserver.SetupSignalHandler())
 		},
+		Args: func(cmd *cobra.Command, args []string) error {
+			for _, arg := range args {
+				if len(arg) > 0 {
+					return fmt.Errorf("%q does not take any arguments, got %q", cmd.CommandPath(), args)
+				}
+			}
+			return nil
+		},
 	}
 
 	fs := cmd.Flags()

cmd/kube-controller-manager/app/controllermanager.go

@@ -119,6 +119,14 @@ controller, and serviceaccounts controller.`,
 				os.Exit(1)
 			}
 		},
+		Args: func(cmd *cobra.Command, args []string) error {
+			for _, arg := range args {
+				if len(arg) > 0 {
+					return fmt.Errorf("%q does not take any arguments, got %q", cmd.CommandPath(), args)
+				}
+			}
+			return nil
+		},
 	}
 
 	fs := cmd.Flags()

cmd/kube-proxy/app/server.go

@@ -294,10 +294,7 @@ func (o *Options) processHostnameOverrideFlag() error {
 }
 
 // Validate validates all the required options.
-func (o *Options) Validate(args []string) error {
+func (o *Options) Validate() error {
-	if len(args) != 0 {
-		return errors.New("no arguments are supported")
-	}
 	if errs := validation.Validate(o.config); len(errs) != 0 {
 		return errs.ToAggregate()
 	}
@@ -490,7 +487,7 @@ with the apiserver API to configure the proxy.`,
 			if err := opts.Complete(); err != nil {
 				klog.Fatalf("failed complete: %v", err)
 			}
-			if err := opts.Validate(args); err != nil {
+			if err := opts.Validate(); err != nil {
 				klog.Fatalf("failed validate: %v", err)
 			}
 
@@ -498,6 +495,14 @@ with the apiserver API to configure the proxy.`,
 				klog.Exit(err)
 			}
 		},
+		Args: func(cmd *cobra.Command, args []string) error {
+			for _, arg := range args {
+				if len(arg) > 0 {
+					return fmt.Errorf("%q does not take any arguments, got %q", cmd.CommandPath(), args)
+				}
+			}
+			return nil
+		},
 	}
 
 	var err error

cmd/kube-scheduler/app/server.go

@@ -27,7 +27,7 @@ import (
 
 	"github.com/spf13/cobra"
 
-	"k8s.io/api/core/v1"
+	v1 "k8s.io/api/core/v1"
 	eventsv1beta1 "k8s.io/api/events/v1beta1"
 	utilerrors "k8s.io/apimachinery/pkg/util/errors"
 	"k8s.io/apiserver/pkg/authentication/authenticator"
@@ -83,11 +83,19 @@ kube-scheduler is the reference implementation.
 See [scheduling](https://kubernetes.io/docs/concepts/scheduling/)
 for more information about scheduling and the kube-scheduler component.`,
 		Run: func(cmd *cobra.Command, args []string) {
-			if err := runCommand(cmd, args, opts, registryOptions...); err != nil {
+			if err := runCommand(cmd, opts, registryOptions...); err != nil {
 				fmt.Fprintf(os.Stderr, "%v\n", err)
 				os.Exit(1)
 			}
 		},
+		Args: func(cmd *cobra.Command, args []string) error {
+			for _, arg := range args {
+				if len(arg) > 0 {
+					return fmt.Errorf("%q does not take any arguments, got %q", cmd.CommandPath(), args)
+				}
+			}
+			return nil
+		},
 	}
 	fs := cmd.Flags()
 	namedFlagSets := opts.Flags()
@@ -114,14 +122,14 @@ for more information about scheduling and the kube-scheduler component.`,
 }
 
 // runCommand runs the scheduler.
-func runCommand(cmd *cobra.Command, args []string, opts *options.Options, registryOptions ...Option) error {
+func runCommand(cmd *cobra.Command, opts *options.Options, registryOptions ...Option) error {
 	verflag.PrintAndExitIfRequested()
 	cliflag.PrintFlags(cmd.Flags())
 
 	ctx, cancel := context.WithCancel(context.Background())
 	defer cancel()
 
-	cc, sched, err := Setup(ctx, args, opts, registryOptions...)
+	cc, sched, err := Setup(ctx, opts, registryOptions...)
 	if err != nil {
 		return err
 	}
@@ -298,11 +306,7 @@ func WithPlugin(name string, factory framework.PluginFactory) Option {
 }
 
 // Setup creates a completed config and a scheduler based on the command args and options
-func Setup(ctx context.Context, args []string, opts *options.Options, outOfTreeRegistryOptions ...Option) (*schedulerserverconfig.CompletedConfig, *scheduler.Scheduler, error) {
+func Setup(ctx context.Context, opts *options.Options, outOfTreeRegistryOptions ...Option) (*schedulerserverconfig.CompletedConfig, *scheduler.Scheduler, error) {
-	if len(args) != 0 {
-		fmt.Fprint(os.Stderr, "arguments are not supported\n")
-	}
-
 	if errs := opts.Validate(); len(errs) > 0 {
 		return nil, nil, utilerrors.NewAggregate(errs)
 	}

cmd/kube-scheduler/app/server_test.go

@@ -373,10 +373,9 @@ profiles:
 				t.Fatal(err)
 			}
 
-			var args []string
 			ctx, cancel := context.WithCancel(context.Background())
 			defer cancel()
-			cc, sched, err := Setup(ctx, args, opts)
+			cc, sched, err := Setup(ctx, opts)
 			if err != nil {
 				t.Fatal(err)
 			}

cmd/kube-scheduler/app/testing/testserver.go

@@ -114,7 +114,7 @@ func StartTestServer(t Logger, customFlags []string) (result TestServer, err err
 		t.Logf("kube-scheduler will listen insecurely on port %d...", opts.CombinedInsecureServing.BindPort)
 	}
 
-	cc, sched, err := app.Setup(ctx, []string{}, opts)
+	cc, sched, err := app.Setup(ctx, opts)
 	if err != nil {
 		return result, fmt.Errorf("failed to create config from options: %v", err)
 	}

cmd/kubeadm/app/cmd/alpha/certs.go

@@ -100,6 +100,7 @@ func NewCmdCertificateKey() *cobra.Command {
 			fmt.Println(key)
 			return nil
 		},
+		Args: cobra.NoArgs,
 	}
 }
 
@@ -195,6 +196,7 @@ func getRenewSubCommands(out io.Writer, kdir string) []*cobra.Command {
 			}
 			return nil
 		},
+		Args: cobra.NoArgs,
 	}
 	addRenewFlags(allCmd, flags)
 
@@ -378,6 +380,7 @@ func newCmdCertsExpiration(out io.Writer, kdir string) *cobra.Command {
 			w.Flush()
 			return nil
 		},
+		Args: cobra.NoArgs,
 	}
 	addExpirationFlags(cmd, flags)
 

cmd/kubeadm/app/cmd/alpha/kubeconfig.go

@@ -94,6 +94,7 @@ func newCmdUserKubeConfig(out io.Writer) *cobra.Command {
 			// Otherwise, write a kubeconfig file with a generate client cert
 			return kubeconfigphase.WriteKubeConfigWithClientCert(out, internalcfg, clientName, organizations)
 		},
+		Args: cobra.NoArgs,
 	}
 
 	// Add ClusterConfiguration backed flags to the command

cmd/kubeadm/app/cmd/alpha/kubelet.go

@@ -104,6 +104,7 @@ func newCmdKubeletConfigEnableDynamic() *cobra.Command {
 
 			return kubeletphase.EnableDynamicConfigForNode(client, nodeName, kubeletVersion)
 		},
+		Args: cobra.NoArgs,
 	}
 
 	options.AddKubeConfigFlag(cmd.Flags(), &kubeConfigFile)

cmd/kubeadm/app/cmd/alpha/selfhosting.go

@@ -136,6 +136,7 @@ func getSelfhostingSubCommand(in io.Reader) *cobra.Command {
 			waiter := apiclient.NewKubeWaiter(client, 2*time.Minute, os.Stdout)
 			return selfhosting.CreateSelfHostedControlPlane(constants.GetStaticPodDirectory(), constants.KubernetesDir, internalcfg, client, waiter, false, certsInSecrets)
 		},
+		Args: cobra.NoArgs,
 	}
 
 	// Add flags to the command

cmd/kubeadm/app/cmd/config.go

@@ -140,6 +140,7 @@ func newCmdConfigPrintActionDefaults(out io.Writer, action string, configBytesPr
 			}
 			return runConfigPrintActionDefaults(out, groups, configBytesProc)
 		},
+		Args: cobra.NoArgs,
 	}
 	cmd.Flags().StringSliceVar(&kinds, "component-configs", kinds,
 		fmt.Sprintf("A comma-separated list for component config API objects to print the default values for. Available values: %v. If this flag is not set, no component configs will be printed.", getSupportedComponentConfigKinds()))
@@ -295,6 +296,7 @@ func NewCmdConfigMigrate(out io.Writer) *cobra.Command {
 			}
 			return nil
 		},
+		Args: cobra.NoArgs,
 	}
 	cmd.Flags().StringVar(&oldCfgPath, "old-config", "", "Path to the kubeadm config file that is using an old API version and should be converted. This flag is mandatory.")
 	cmd.Flags().StringVar(&newCfgPath, "new-config", "", "Path to the resulting equivalent kubeadm config file using the new API version. Optional, if not specified output will be sent to STDOUT.")
@@ -335,6 +337,7 @@ func NewCmdConfigView(out io.Writer, kubeConfigFile *string) *cobra.Command {
 
 			return RunConfigView(out, client)
 		},
+		Args: cobra.NoArgs,
 	}
 }
 
@@ -375,6 +378,7 @@ func NewCmdConfigUploadFromFile(out io.Writer, kubeConfigFile *string) *cobra.Co
 			klog.V(1).Infof("[config] uploading configuration")
 			return uploadconfig.UploadConfiguration(internalcfg, client)
 		},
+		Args: cobra.NoArgs,
 	}
 	options.AddConfigFlag(cmd.Flags(), &cfgPath)
 	return cmd
@@ -429,6 +433,7 @@ func NewCmdConfigUploadFromFlags(out io.Writer, kubeConfigFile *string) *cobra.C
 			klog.V(1).Infof("[config] uploading configuration")
 			return uploadconfig.UploadConfiguration(internalcfg, client)
 		},
+		Args: cobra.NoArgs,
 	}
 	AddInitConfigFlags(cmd.PersistentFlags(), initCfg)
 	AddClusterConfigFlags(cmd.PersistentFlags(), clusterCfg, &featureGatesString)
@@ -487,6 +492,7 @@ func NewCmdConfigImagesPull() *cobra.Command {
 			}
 			return PullControlPlaneImages(containerRuntime, &internalcfg.ClusterConfiguration)
 		},
+		Args: cobra.NoArgs,
 	}
 	AddImagesCommonConfigFlags(cmd.PersistentFlags(), externalClusterCfg, &cfgPath, &featureGatesString)
 	cmdutil.AddCRISocketFlag(cmd.PersistentFlags(), &externalInitCfg.NodeRegistration.CRISocket)
@@ -556,6 +562,7 @@ func NewCmdConfigImagesList(out io.Writer, mockK8sVersion *string) *cobra.Comman
 
 			return imagesList.Run(out, printer)
 		},
+		Args: cobra.NoArgs,
 	}
 	outputFlags.AddFlags(cmd)
 	AddImagesCommonConfigFlags(cmd.PersistentFlags(), externalcfg, &cfgPath, &featureGatesString)

cmd/kubeadm/app/cmd/token.go

@@ -173,6 +173,7 @@ func NewCmdToken(out io.Writer, errW io.Writer) *cobra.Command {
 
 			return RunListTokens(out, errW, client, printer)
 		},
+		Args: cobra.NoArgs,
 	}
 
 	outputFlags.AddFlags(listCmd)
@@ -226,6 +227,7 @@ func NewCmdTokenGenerate(out io.Writer) *cobra.Command {
 		RunE: func(cmd *cobra.Command, args []string) error {
 			return RunGenerateToken(out)
 		},
+		Args: cobra.NoArgs,
 	}
 }
 

cmd/kubeadm/app/cmd/version.go

@@ -43,6 +43,7 @@ func NewCmdVersion(out io.Writer) *cobra.Command {
 		RunE: func(cmd *cobra.Command, args []string) error {
 			return RunVersion(out, cmd)
 		},
+		Args: cobra.NoArgs,
 	}
 	cmd.Flags().StringP("output", "o", "", "Output format; available options are 'yaml', 'json' and 'short'")
 	return cmd

cmd/kubeadm/test/cmd/version_test.go

@@ -48,7 +48,11 @@ func TestCmdVersion(t *testing.T) {
 	kubeadmPath := getKubeadmPath()
 	for _, rt := range versionTest {
 		t.Run(rt.name, func(t *testing.T) {
-			stdout, _, _, actual := RunCmd(kubeadmPath, "version", rt.args)
+			args := []string{"version"}
+			if len(rt.args) > 0 {
+				args = append(args, rt.args)
+			}
+			stdout, _, _, actual := RunCmd(kubeadmPath, args...)
 			if (actual == nil) != rt.expected {
 				t.Errorf(
 					"failed CmdVersion running 'kubeadm version %s' with an error: %v\n\texpected: %t\n\t  actual: %t",

cmd/kubemark/hollow-node.go

@@ -148,6 +148,14 @@ func newHollowNodeCommand() *cobra.Command {
 			verflag.PrintAndExitIfRequested()
 			run(s)
 		},
+		Args: func(cmd *cobra.Command, args []string) error {
+			for _, arg := range args {
+				if len(arg) > 0 {
+					return fmt.Errorf("%q does not take any arguments, got %q", cmd.CommandPath(), args)
+				}
+			}
+			return nil
+		},
 	}
 	s.addFlags(cmd.Flags())