kubernetes/pkg/kubeapiserver/options/authorization.go

/*
Copyright 2016 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 options

import (
	"fmt"
	"strings"
	"time"

	"github.com/spf13/pflag"

	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/apimachinery/pkg/util/sets"
	"k8s.io/apimachinery/pkg/util/wait"
	authzconfig "k8s.io/apiserver/pkg/apis/apiserver"
	genericoptions "k8s.io/apiserver/pkg/server/options"
	versionedinformers "k8s.io/client-go/informers"

	"k8s.io/kubernetes/pkg/kubeapiserver/authorizer"
	authzmodes "k8s.io/kubernetes/pkg/kubeapiserver/authorizer/modes"
)

const (
	defaultWebhookName = "default"
)

// BuiltInAuthorizationOptions contains all build-in authorization options for API Server
type BuiltInAuthorizationOptions struct {
	Modes                       []string
	PolicyFile                  string
	WebhookConfigFile           string
	WebhookVersion              string
	WebhookCacheAuthorizedTTL   time.Duration
	WebhookCacheUnauthorizedTTL time.Duration
	// WebhookRetryBackoff specifies the backoff parameters for the authorization webhook retry logic.
	// This allows us to configure the sleep time at each iteration and the maximum number of retries allowed
	// before we fail the webhook call in order to limit the fan out that ensues when the system is degraded.
	WebhookRetryBackoff *wait.Backoff
}

// NewBuiltInAuthorizationOptions create a BuiltInAuthorizationOptions with default value
func NewBuiltInAuthorizationOptions() *BuiltInAuthorizationOptions {
	return &BuiltInAuthorizationOptions{
		Modes:                       []string{authzmodes.ModeAlwaysAllow},
		WebhookVersion:              "v1beta1",
		WebhookCacheAuthorizedTTL:   5 * time.Minute,
		WebhookCacheUnauthorizedTTL: 30 * time.Second,
		WebhookRetryBackoff:         genericoptions.DefaultAuthWebhookRetryBackoff(),
	}
}

// Validate checks invalid config combination
func (o *BuiltInAuthorizationOptions) Validate() []error {
	if o == nil {
		return nil
	}
	var allErrors []error
	if len(o.Modes) == 0 {
		allErrors = append(allErrors, fmt.Errorf("at least one authorization-mode must be passed"))
	}

	modes := sets.NewString(o.Modes...)
	for _, mode := range o.Modes {
		if !authzmodes.IsValidAuthorizationMode(mode) {
			allErrors = append(allErrors, fmt.Errorf("authorization-mode %q is not a valid mode", mode))
		}
		if mode == authzmodes.ModeABAC && o.PolicyFile == "" {
			allErrors = append(allErrors, fmt.Errorf("authorization-mode ABAC's authorization policy file not passed"))
		}
		if mode == authzmodes.ModeWebhook && o.WebhookConfigFile == "" {
			allErrors = append(allErrors, fmt.Errorf("authorization-mode Webhook's authorization config file not passed"))
		}
	}

	if o.PolicyFile != "" && !modes.Has(authzmodes.ModeABAC) {
		allErrors = append(allErrors, fmt.Errorf("cannot specify --authorization-policy-file without mode ABAC"))
	}

	if o.WebhookConfigFile != "" && !modes.Has(authzmodes.ModeWebhook) {
		allErrors = append(allErrors, fmt.Errorf("cannot specify --authorization-webhook-config-file without mode Webhook"))
	}

	if len(o.Modes) != modes.Len() {
		allErrors = append(allErrors, fmt.Errorf("authorization-mode %q has mode specified more than once", o.Modes))
	}

	if o.WebhookRetryBackoff != nil && o.WebhookRetryBackoff.Steps <= 0 {
		allErrors = append(allErrors, fmt.Errorf("number of webhook retry attempts must be greater than 0, but is: %d", o.WebhookRetryBackoff.Steps))
	}

	return allErrors
}

// AddFlags returns flags of authorization for a API Server
func (o *BuiltInAuthorizationOptions) AddFlags(fs *pflag.FlagSet) {
	if o == nil {
		return
	}

	fs.StringSliceVar(&o.Modes, "authorization-mode", o.Modes, ""+
		"Ordered list of plug-ins to do authorization on secure port. Comma-delimited list of: "+
		strings.Join(authzmodes.AuthorizationModeChoices, ",")+".")

	fs.StringVar(&o.PolicyFile, "authorization-policy-file", o.PolicyFile, ""+
		"File with authorization policy in json line by line format, used with --authorization-mode=ABAC, on the secure port.")

	fs.StringVar(&o.WebhookConfigFile, "authorization-webhook-config-file", o.WebhookConfigFile, ""+
		"File with webhook configuration in kubeconfig format, used with --authorization-mode=Webhook. "+
		"The API server will query the remote service to determine access on the API server's secure port.")

	fs.StringVar(&o.WebhookVersion, "authorization-webhook-version", o.WebhookVersion, ""+
		"The API version of the authorization.k8s.io SubjectAccessReview to send to and expect from the webhook.")

	fs.DurationVar(&o.WebhookCacheAuthorizedTTL, "authorization-webhook-cache-authorized-ttl",
		o.WebhookCacheAuthorizedTTL,
		"The duration to cache 'authorized' responses from the webhook authorizer.")

	fs.DurationVar(&o.WebhookCacheUnauthorizedTTL,
		"authorization-webhook-cache-unauthorized-ttl", o.WebhookCacheUnauthorizedTTL,
		"The duration to cache 'unauthorized' responses from the webhook authorizer.")
}

// ToAuthorizationConfig convert BuiltInAuthorizationOptions to authorizer.Config
func (o *BuiltInAuthorizationOptions) ToAuthorizationConfig(versionedInformerFactory versionedinformers.SharedInformerFactory) (*authorizer.Config, error) {
	if o == nil {
		return nil, nil
	}

	authzConfiguration, err := o.buildAuthorizationConfiguration()
	if err != nil {
		return nil, fmt.Errorf("failed to build authorization config: %s", err)
	}

	return &authorizer.Config{
		PolicyFile:               o.PolicyFile,
		VersionedInformerFactory: versionedInformerFactory,
		WebhookRetryBackoff:      o.WebhookRetryBackoff,

		AuthorizationConfiguration: authzConfiguration,
	}, nil
}

// buildAuthorizationConfiguration converts existing flags to the AuthorizationConfiguration format
func (o *BuiltInAuthorizationOptions) buildAuthorizationConfiguration() (*authzconfig.AuthorizationConfiguration, error) {
	var authorizers []authzconfig.AuthorizerConfiguration

	if len(o.Modes) != sets.NewString(o.Modes...).Len() {
		return nil, fmt.Errorf("modes should not be repeated in --authorization-mode")
	}

	for _, mode := range o.Modes {
		switch mode {
		case authzmodes.ModeWebhook:
			authorizers = append(authorizers, authzconfig.AuthorizerConfiguration{
				Type: authzconfig.TypeWebhook,
				Name: defaultWebhookName,
				Webhook: &authzconfig.WebhookConfiguration{
					AuthorizedTTL:   metav1.Duration{Duration: o.WebhookCacheAuthorizedTTL},
					UnauthorizedTTL: metav1.Duration{Duration: o.WebhookCacheUnauthorizedTTL},
					// Timeout and FailurePolicy are required for the new configuration.
					// Setting these two implicitly to preserve backward compatibility.
					Timeout:                    metav1.Duration{Duration: 30 * time.Second},
					FailurePolicy:              authzconfig.FailurePolicyNoOpinion,
					SubjectAccessReviewVersion: o.WebhookVersion,
					ConnectionInfo: authzconfig.WebhookConnectionInfo{
						Type:           authzconfig.AuthorizationWebhookConnectionInfoTypeKubeConfig,
						KubeConfigFile: &o.WebhookConfigFile,
					},
				},
			})
		default:
			authorizers = append(authorizers, authzconfig.AuthorizerConfiguration{
				Type: authzconfig.AuthorizerType(mode),
				Name: getNameForAuthorizerMode(mode),
			})
		}
	}

	return &authzconfig.AuthorizationConfiguration{Authorizers: authorizers}, nil
}

// getNameForAuthorizerMode returns the name to be set for the mode in AuthorizationConfiguration
// For now, lower cases the mode name
func getNameForAuthorizerMode(mode string) string {
	return strings.ToLower(mode)
}