bind.go

/*
Copyright 2022 The Kube Bind 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 plugin

import (
	"bytes"
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"net/url"
	"os"
	"os/exec"
	"strings"
	"time"

	"github.com/spf13/cobra"
	"github.com/spf13/pflag"

	corev1 "k8s.io/api/core/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/runtime/schema"
	"k8s.io/apimachinery/pkg/util/rand"
	"k8s.io/apimachinery/pkg/util/sets"
	"k8s.io/cli-runtime/pkg/genericclioptions"
	kubeclient "k8s.io/client-go/kubernetes"
	"k8s.io/component-base/logs"
	logsv1 "k8s.io/component-base/logs/api/v1"

	"github.com/kube-bind/kube-bind/contrib/example-backend/http"
	kubebindv1alpha1 "github.com/kube-bind/kube-bind/pkg/apis/kubebind/v1alpha1"
	"github.com/kube-bind/kube-bind/pkg/kubectl/base"
	"github.com/kube-bind/kube-bind/pkg/kubectl/bind/authenticator"
)

// BindOptions contains the options for creating an APIBinding.
type BindOptions struct {
	*base.Options
	Logs *logs.Options

	Print  *genericclioptions.PrintFlags
	DryRun bool

	// url is the argument accepted by the command. It contains the
	// reference to where an APIService exists.
	URL string

	// skipKonnector skips the deployment of the konnector.
	SkipKonnector bool

	// Runner is runs the command. It can be replaced in tests.
	Runner func(cmd *exec.Cmd) error

	flags *pflag.FlagSet
}

// NewBindOptions returns new BindOptions.
func NewBindOptions(streams genericclioptions.IOStreams) *BindOptions {
	opts := &BindOptions{
		Options: base.NewOptions(streams),
		Logs:    logs.NewOptions(),
		Print:   genericclioptions.NewPrintFlags("kubectl-bind"),

		Runner: func(cmd *exec.Cmd) error {
			return cmd.Run()
		},
	}

	return opts
}

// AddCmdFlags binds fields to cmd's flagset.
func (b *BindOptions) AddCmdFlags(cmd *cobra.Command) {
	b.flags = cmd.Flags()

	b.Options.BindFlags(cmd)
	logsv1.AddFlags(b.Logs, cmd.Flags())
	b.Print.AddFlags(cmd)

	cmd.Flags().BoolVar(&b.SkipKonnector, "skip-konnector", b.SkipKonnector, "Skip the deployment of the konnector")
	cmd.Flags().BoolVarP(&b.DryRun, "dry-run", "d", b.DryRun, "If true, only print the requests that would be sent to the service provider after authentication, without actually binding.")
}

// Complete ensures all fields are initialized.
func (b *BindOptions) Complete(args []string) error {
	if err := b.Options.Complete(); err != nil {
		return err
	}

	if len(args) > 0 {
		b.URL = args[0]
	}
	return nil
}

// Validate validates the BindOptions are complete and usable.
func (b *BindOptions) Validate() error {
	if b.URL == "" {
		return errors.New("url is required as an argument") // should not happen because we validate that before
	}

	if _, err := url.Parse(b.URL); err != nil {
		return fmt.Errorf("invalid url %q: %w", b.URL, err)
	}

	if allowed := sets.NewString(b.Print.AllowedFormats()...); *b.Print.OutputFormat != "" && !allowed.Has(*b.Print.OutputFormat) {
		return fmt.Errorf("invalid output format %q (allowed: %s)", *b.Print.OutputFormat, strings.Join(allowed.List(), ", "))
	}
	if b.DryRun && *b.Print.OutputFormat == "" {
		return errors.New("output format is required when dry-run is enabled")
	}

	return b.Options.Validate()
}

// Run starts the binding process.
func (b *BindOptions) Run(ctx context.Context, urlCh chan<- string) error {
	config, err := b.ClientConfig.ClientConfig()
	if err != nil {
		return err
	}
	kubeClient, err := kubeclient.NewForConfig(config)
	if err != nil {
		return err
	}

	var gvk schema.GroupVersionKind
	var response runtime.Object
	auth, err := authenticator.NewDefaultAuthenticator(10*time.Minute, func(ctx context.Context, what schema.GroupVersionKind, obj runtime.Object) error {
		response = obj
		gvk = what
		return nil
	})
	if err != nil {
		return err
	}

	exportURL, err := url.Parse(b.URL)
	if err != nil {
		return err // should never happen because we test this in Validate()
	}

	provider, err := getProvider(exportURL.String())
	if err != nil {
		return fmt.Errorf("failed to fetch authentication url %q: %v", exportURL, err)
	}

	if provider.APIVersion != kubebindv1alpha1.GroupVersion {
		return fmt.Errorf("unsupported binding provider version: %q", provider.APIVersion)
	}

	sessionID := rand.String(rand.IntnRange(20, 30))

	if err := b.authenticate(provider, auth.Endpoint(ctx), sessionID, urlCh); err != nil {
		return err
	}

	if err := auth.Execute(ctx); err != nil {
		return err
	} else if response == nil {
		return fmt.Errorf("authentication timeout")
	}

	fmt.Fprintf(b.IOStreams.ErrOut, "Successfully authenticated to %s\n", exportURL.String()) // nolint: errcheck

	// verify the response
	if gvk.GroupVersion() != kubebindv1alpha1.SchemeGroupVersion || gvk.Kind != "BindingResponse" {
		return fmt.Errorf("unexpected response type %s, only supporting %s", gvk, kubebindv1alpha1.SchemeGroupVersion.WithKind("BindingResponse"))
	}
	bindingResponse, ok := response.(*kubebindv1alpha1.BindingResponse)
	if !ok {
		return fmt.Errorf("unexpected response type %T", response)
	}
	if bindingResponse.Authentication == nil {
		return fmt.Errorf("unexpected response: authentication is nil")
	}
	var authResponse http.CodeGrantCallbackResponse
	if err := json.Unmarshal(bindingResponse.Authentication.Raw, &authResponse); err != nil {
		return fmt.Errorf("unexpected response: failed to unmarshal authentication response: %v", err)
	}
	if authResponse.SessionID != sessionID {
		return fmt.Errorf("unexpected response: sessionID does not match")
	}

	// extract the requests
	var apiRequests []*kubebindv1alpha1.APIServiceBindingRequestResponse
	for i, request := range bindingResponse.Requests {
		var meta metav1.TypeMeta
		if err := json.Unmarshal(request.Raw, &meta); err != nil {
			return fmt.Errorf("unexpected response: failed to unmarshal request #%d: %v", i, err)
		}
		if got, expected := meta.APIVersion, kubebindv1alpha1.SchemeGroupVersion.String(); got != expected {
			return fmt.Errorf("unexpected response: request #%d is not %s, got %s", i, expected, got)
		}
		var apiRequest kubebindv1alpha1.APIServiceBindingRequestResponse
		if err := json.Unmarshal(request.Raw, &apiRequest); err != nil {
			return fmt.Errorf("failed to unmarshal api request #%d: %v", i+1, err)
		}
		apiRequests = append(apiRequests, &apiRequest)
	}

	// create kube-bind namespace
	if _, err := kubeClient.CoreV1().Namespaces().Create(ctx, &corev1.Namespace{
		ObjectMeta: metav1.ObjectMeta{
			Name: "kube-bind",
		},
	}, metav1.CreateOptions{}); err != nil && !apierrors.IsAlreadyExists(err) {
		return err
	} else if err == nil {
		fmt.Fprintf(b.Options.IOStreams.ErrOut, "Created kube-binding namespace.\n") // nolint: errcheck
	}

	// copy kubeconfig into local cluster
	remoteHost, remoteNamespace, err := base.ParseRemoteKubeconfig(bindingResponse.Kubeconfig)
	if err != nil {
		return err
	}
	secretName, err := base.FindRemoteKubeconfig(ctx, kubeClient, remoteNamespace, remoteHost)
	if err != nil {
		return err
	}
	secret, created, err := base.EnsureKubeconfigSecret(ctx, string(bindingResponse.Kubeconfig), secretName, kubeClient)
	if err != nil {
		return err
	}
	if created {
		fmt.Fprintf(b.Options.ErrOut, "Created secret %s/%s for host %s, namespace %s\n", "kube-bind", secret.Name, remoteHost, remoteNamespace)
	} else {
		fmt.Fprintf(b.Options.ErrOut, "Updated secret %s/%s for host %s, namespace %s\n", "kube-bind", secret.Name, remoteHost, remoteNamespace)
	}

	// print the request in dry-run mode
	if b.DryRun {
		printer, err := b.Print.ToPrinter()
		if err != nil {
			return err
		}
		first := true
		for _, request := range apiRequests {
			printer.PrintObj(request, b.IOStreams.Out) // nolint: errcheck

			// TODO: this is a hack to separate the objects. Is there anything better in the printer?
			if !first && *b.Print.OutputFormat == "yaml" {
				fmt.Fprintln(b.IOStreams.Out, "---") // nolint: errcheck
			}

			first = false
		}
	}

	if b.DryRun {
		return nil
	}

	// call sub-command for apiservices
	executable, err := os.Executable()
	if err != nil {
		return err
	}
	for _, request := range apiRequests {
		bs, err := json.Marshal(request)
		if err != nil {
			return err
		}

		args := []string{
			"apiservice",
			"--remote-kubeconfig-namespace", secret.Namespace,
			"--remote-kubeconfig-name", secret.Name,
			"-f", "-",
		}
		b.flags.VisitAll(func(flag *pflag.Flag) {
			if flag.Changed && PassOnFlags.Has(flag.Name) {
				args = append(args, "--"+flag.Name+"="+flag.Value.String())
			}
		})

		// TODO: support passing through the base options

		fmt.Fprintf(b.Options.ErrOut, "Executing: %s %s\n", "kubectl bind", strings.Join(args, " ")) // nolint: errcheck
		command := exec.CommandContext(ctx, executable, append(args, "--no-banner")...)
		command.Stdin = bytes.NewReader(bs)
		command.Stdout = b.Options.Out
		command.Stderr = b.Options.ErrOut
		if err := b.Runner(command); err != nil {
			return err
		}
	}

	return nil
}