supervisor-oidc: hoist OIDC discovery handler for testing

Signed-off-by: Andrew Keesler <akeesler@vmware.com>

cmd/pinniped-supervisor/main.go

@@ -25,6 +25,9 @@ import (
 	"go.pinniped.dev/internal/controller/supervisorconfig"
 	"go.pinniped.dev/internal/controllerlib"
 	"go.pinniped.dev/internal/downward"
+	"go.pinniped.dev/internal/oidc"
+	"go.pinniped.dev/internal/oidc/discovery"
+	"go.pinniped.dev/internal/oidc/issuerprovider"
 )
 
 const (
@@ -32,11 +35,11 @@ const (
 	defaultResyncInterval = 3 * time.Minute
 )
 
-type helloWorld struct{}
-
-func (w *helloWorld) start(ctx context.Context, l net.Listener) error {
+func start(ctx context.Context, l net.Listener, discoveryHandler http.Handler) {
+	mux := http.NewServeMux()
+	mux.Handle(oidc.WellKnownURLPath, discoveryHandler)
 	server := http.Server{
-		Handler: w,
+		Handler: mux,
 	}
 
 	errCh := make(chan error)
@@ -55,14 +58,6 @@ func (w *helloWorld) start(ctx context.Context, l net.Listener) error {
 			}
 		}
 	}()
-
-	return nil
-}
-
-func (w *helloWorld) ServeHTTP(rsp http.ResponseWriter, req *http.Request) {
-	// TODO this is just a placeholder to allow manually testing that this is reachable; we don't want a hello world endpoint
-	defer req.Body.Close()
-	_, _ = fmt.Fprintf(rsp, "Hello, world!")
 }
 
 func waitForSignal() os.Signal {
@@ -73,6 +68,7 @@ func waitForSignal() os.Signal {
 
 func startControllers(
 	ctx context.Context,
+	issuerProvider *issuerprovider.Provider,
 	kubeClient kubernetes.Interface,
 	kubeInformers kubeinformers.SharedInformerFactory,
 	serverInstallationNamespace string,
@@ -85,6 +81,7 @@ func startControllers(
 			supervisorconfig.NewDynamicConfigWatcherController(
 				serverInstallationNamespace,
 				staticConfig.NamesConfig.DynamicConfigMap,
+				issuerProvider,
 				kubeClient,
 				kubeInformers.Core().V1().ConfigMaps(),
 				controllerlib.WithInformer,
@@ -127,7 +124,8 @@ func run(serverInstallationNamespace string, staticConfig StaticConfig) error {
 		kubeinformers.WithNamespace(serverInstallationNamespace),
 	)
 
-	startControllers(ctx, kubeClient, kubeInformers, serverInstallationNamespace, staticConfig)
+	issuerProvider := issuerprovider.New()
+	startControllers(ctx, issuerProvider, kubeClient, kubeInformers, serverInstallationNamespace, staticConfig)
 
 	//nolint: gosec // Intentionally binding to all network interfaces.
 	l, err := net.Listen("tcp", ":80")
@@ -136,11 +134,7 @@ func run(serverInstallationNamespace string, staticConfig StaticConfig) error {
 	}
 	defer l.Close()
 
-	helloHandler := &helloWorld{}
-	err = helloHandler.start(ctx, l)
-	if err != nil {
-		return fmt.Errorf("cannot start webhook: %w", err)
-	}
+	start(ctx, l, discovery.New(issuerProvider))
 	klog.InfoS("supervisor is ready", "address", l.Addr().String())
 
 	gotSignal := waitForSignal()

internal/controller/supervisorconfig/dynamic_config_watcher.go

@@ -4,6 +4,9 @@
 package supervisorconfig
 
 import (
+	"fmt"
+
+	k8serrors "k8s.io/apimachinery/pkg/api/errors"
 	corev1informers "k8s.io/client-go/informers/core/v1"
 	"k8s.io/client-go/kubernetes"
 	"k8s.io/klog/v2"
@@ -12,14 +15,30 @@ import (
 	"go.pinniped.dev/internal/controllerlib"
 )
 
+const (
+	issuerConfigMapKey = "issuer"
+)
+
+// IssuerSetter can be notified of a valid issuer with its SetIssuer function. If there is no
+// longer any valid issuer, then nil can be passed to this interface.
+//
+// Implementations of this type should be thread-safe to support calls from multiple goroutines.
+type IssuerSetter interface {
+	SetIssuer(issuer *string)
+}
+
 type dynamicConfigWatcherController struct {
-	k8sClient         kubernetes.Interface
-	configMapInformer corev1informers.ConfigMapInformer
+	configMapName      string
+	configMapNamespace string
+	issuerSetter       IssuerSetter
+	k8sClient          kubernetes.Interface
+	configMapInformer  corev1informers.ConfigMapInformer
 }
 
 func NewDynamicConfigWatcherController(
 	serverInstallationNamespace string,
 	configMapName string,
+	issuerObserver IssuerSetter,
 	k8sClient kubernetes.Interface,
 	configMapInformer corev1informers.ConfigMapInformer,
 	withInformer pinnipedcontroller.WithInformerOptionFunc,
@@ -28,8 +47,11 @@ func NewDynamicConfigWatcherController(
 		controllerlib.Config{
 			Name: "DynamicConfigWatcherController",
 			Syncer: &dynamicConfigWatcherController{
-				k8sClient:         k8sClient,
-				configMapInformer: configMapInformer,
+				configMapNamespace: serverInstallationNamespace,
+				configMapName:      configMapName,
+				issuerSetter:       issuerObserver,
+				k8sClient:          k8sClient,
+				configMapInformer:  configMapInformer,
 			},
 		},
 		withInformer(
@@ -44,9 +66,47 @@ func NewDynamicConfigWatcherController(
 func (c *dynamicConfigWatcherController) Sync(ctx controllerlib.Context) error {
 	// TODO Watch the configmap to find the issuer name, ingress url, etc.
 	// TODO Update some kind of in-memory representation of the configuration so the discovery endpoint can use it.
-	// TODO The discovery endpoint would return an error until all missing configuration options are filled in.
+	// TODO The discovery endpoint would return an error until all missing configuration options are
+	// filled in.
 
-	klog.InfoS("DynamicConfigWatcherController sync finished")
+	configMap, err := c.configMapInformer.
+		Lister().
+		ConfigMaps(c.configMapNamespace).
+		Get(c.configMapName)
+	notFound := k8serrors.IsNotFound(err)
+	if err != nil && !notFound {
+		return fmt.Errorf("failed to get %s/%s secret: %w", c.configMapNamespace, c.configMapName, err)
+	}
+
+	if notFound {
+		klog.InfoS(
+			"dynamicConfigWatcherController Sync found no configmap",
+			"configmap",
+			klog.KRef(c.configMapNamespace, c.configMapName),
+		)
+		c.issuerSetter.SetIssuer(nil)
+		return nil
+	}
+
+	issuer, ok := configMap.Data[issuerConfigMapKey]
+	if !ok {
+		klog.InfoS(
+			"dynamicConfigWatcherController Sync found no issuer",
+			"configmap",
+			klog.KObj(configMap),
+		)
+		c.issuerSetter.SetIssuer(nil)
+		return nil
+	}
+
+	klog.InfoS(
+		"dynamicConfigWatcherController Sync issuer",
+		"configmap",
+		klog.KObj(configMap),
+		"issuer",
+		issuer,
+	)
+	c.issuerSetter.SetIssuer(&issuer)
 
 	return nil
 }

internal/oidc/discovery/discovery.go

@@ -0,0 +1,66 @@
+// Copyright 2020 the Pinniped contributors. All Rights Reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+// Package discovery provides a handler for the OIDC discovery endpoint.
+package discovery
+
+import (
+	"encoding/json"
+	"fmt"
+	"net/http"
+)
+
+// Metadata holds all fields (that we care about) from the OpenID Provider Metadata section in the
+// OpenID Connect Discovery specification:
+// https://openid.net/specs/openid-connect-discovery-1_0.html#rfc.section.3.
+type Metadata struct {
+	Issuer string `json:"issuer"`
+
+	AuthorizationEndpoint string `json:"authorization_endpoint"`
+	TokenEndpoint         string `json:"token_endpoint"`
+	JWKSURL               string `json:"jwks_url"`
+
+	ResponseTypesSupported           []string `json:"response_types_supported"`
+	SubjectTypesSupported            []string `json:"subject_types_supported"`
+	IDTokenSigningAlgValuesSupported []string `json:"id_token_signing_alg_values_supported"`
+}
+
+// IssuerGetter holds onto an issuer which can be retrieved via its GetIssuer function. If there is
+// no valid issuer, then nil will be returned.
+//
+// Implementations of this type should be thread-safe to support calls from multiple goroutines.
+type IssuerGetter interface {
+	GetIssuer() *string
+}
+
+// New returns an http.Handler that will use information from the provided IssuerGetter to serve an
+// OIDC discovery endpoint.
+func New(ig IssuerGetter) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", "application/json")
+
+		if r.Method != http.MethodGet {
+			http.Error(w, `{"error": "Method not allowed (try GET)"}`, http.StatusMethodNotAllowed)
+			return
+		}
+
+		issuer := ig.GetIssuer()
+		if issuer == nil {
+			http.Error(w, `{"error": "OIDC discovery not available (unknown issuer)"}`, http.StatusServiceUnavailable)
+			return
+		}
+
+		oidcConfig := Metadata{
+			Issuer:                           *issuer,
+			AuthorizationEndpoint:            fmt.Sprintf("%s/oauth2/v0/auth", *issuer),
+			TokenEndpoint:                    fmt.Sprintf("%s/oauth2/v0/token", *issuer),
+			JWKSURL:                          fmt.Sprintf("%s/oauth2/v0/keys", *issuer),
+			ResponseTypesSupported:           []string{},
+			SubjectTypesSupported:            []string{},
+			IDTokenSigningAlgValuesSupported: []string{},
+		}
+		if err := json.NewEncoder(w).Encode(&oidcConfig); err != nil {
+			http.Error(w, err.Error(), http.StatusInternalServerError)
+		}
+	})
+}

internal/oidc/discovery/discovery_test.go

@@ -0,0 +1,90 @@
+// Copyright 2020 the Pinniped contributors. All Rights Reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+package discovery
+
+import (
+	"encoding/json"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+
+	"go.pinniped.dev/internal/oidc/issuerprovider"
+)
+
+func TestDiscovery(t *testing.T) {
+	tests := []struct {
+		name string
+
+		issuer string
+		method string
+
+		wantStatus      int
+		wantContentType string
+		wantBody        interface{}
+	}{
+		{
+			name:       "issuer returns nil issuer",
+			method:     http.MethodGet,
+			wantStatus: http.StatusServiceUnavailable,
+			wantBody: map[string]string{
+				"error": "OIDC discovery not available (unknown issuer)",
+			},
+		},
+		{
+			name:            "issuer returns non-nil issuer",
+			issuer:          "https://some-issuer.com",
+			method:          http.MethodGet,
+			wantStatus:      http.StatusOK,
+			wantContentType: "application/json",
+			wantBody: &Metadata{
+				Issuer:                           "https://some-issuer.com",
+				AuthorizationEndpoint:            "https://some-issuer.com/oauth2/v0/auth",
+				TokenEndpoint:                    "https://some-issuer.com/oauth2/v0/token",
+				JWKSURL:                          "https://some-issuer.com/oauth2/v0/keys",
+				ResponseTypesSupported:           []string{},
+				SubjectTypesSupported:            []string{},
+				IDTokenSigningAlgValuesSupported: []string{},
+			},
+		},
+		{
+			name:       "bad method",
+			issuer:     "https://some-issuer.com",
+			method:     http.MethodPost,
+			wantStatus: http.StatusMethodNotAllowed,
+			wantBody: map[string]string{
+				"error": "Method not allowed (try GET)",
+			},
+		},
+	}
+	for _, test := range tests {
+		test := test
+		t.Run(test.name, func(t *testing.T) {
+			p := issuerprovider.New()
+			if test.issuer != "" {
+				p.SetIssuer(&test.issuer)
+			} else {
+				p.SetIssuer(nil)
+			}
+
+			handler := New(p)
+			req := httptest.NewRequest(test.method, "/this/path/shouldnt/matter", nil)
+			rsp := httptest.NewRecorder()
+			handler.ServeHTTP(rsp, req)
+
+			require.Equal(t, test.wantStatus, rsp.Code)
+
+			if test.wantContentType != "" {
+				require.Equal(t, test.wantContentType, rsp.Header().Get("Content-Type"))
+			}
+
+			if test.wantBody != nil {
+				wantJSON, err := json.Marshal(test.wantBody)
+				require.NoError(t, err)
+				require.JSONEq(t, string(wantJSON), rsp.Body.String())
+			}
+		})
+	}
+}

internal/oidc/issuerprovider/issuerprovider.go

@@ -0,0 +1,32 @@
+// Copyright 2020 the Pinniped contributors. All Rights Reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+// Package issuerprovider provides a thread-safe type that can hold on to an OIDC issuer name.
+package issuerprovider
+
+import "sync"
+
+// Provider is a type that can hold onto an issuer value, which may be nil.
+//
+// It is thread-safe.
+type Provider struct {
+	mu     sync.RWMutex
+	issuer *string
+}
+
+// New returns an empty Provider, i.e., one that holds a nil issuer.
+func New() *Provider {
+	return &Provider{}
+}
+
+func (p *Provider) SetIssuer(issuer *string) {
+	p.mu.Lock()
+	defer p.mu.Unlock()
+	p.issuer = issuer
+}
+
+func (p *Provider) GetIssuer() *string {
+	p.mu.RLock()
+	defer p.mu.RUnlock()
+	return p.issuer
+}

internal/oidc/oidc.go

@@ -0,0 +1,9 @@
+// Copyright 2020 the Pinniped contributors. All Rights Reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+// Package oidc contains common OIDC functionality needed by Pinniped.
+package oidc
+
+const (
+	WellKnownURLPath = "/.well-known/openid-configuration"
+)