[release-4.19] OCPBUGS-60168: CVO protects /metrics with authorization

pkg/cvo/metrics.go

@@ -12,14 +12,19 @@ import (
 	"net/http"
 	"os"
 	"path/filepath"
+	"strings"
 	"time"
 
 	"github.com/prometheus/client_golang/prometheus"
 	"github.com/prometheus/client_golang/prometheus/promhttp"
+	authenticationv1 "k8s.io/api/authentication/v1"
 	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/labels"
 	"k8s.io/apimachinery/pkg/util/sets"
+	authenticationclientsetv1 "k8s.io/client-go/kubernetes/typed/authentication/v1"
+	"k8s.io/client-go/rest"
 	"k8s.io/client-go/tools/cache"
 	"k8s.io/klog/v2"
 
@@ -127,15 +132,75 @@ type asyncResult struct {
 	error error
 }
 
-func createHttpServer() *http.Server {
+func createHttpServer(ctx context.Context, client *authenticationclientsetv1.AuthenticationV1Client) *http.Server {
+	auth := authHandler{downstream: promhttp.Handler(), ctx: ctx, client: client.TokenReviews()}
 	handler := http.NewServeMux()
-	handler.Handle("/metrics", promhttp.Handler())
+	handler.Handle("/metrics", &auth)
 	server := &http.Server{
 		Handler: handler,
 	}
 	return server
 }
 
+type tokenReviewInterface interface {
+	Create(ctx context.Context, tokenReview *authenticationv1.TokenReview, opts metav1.CreateOptions) (*authenticationv1.TokenReview, error)
+}
+
+type authHandler struct {
+	downstream http.Handler
+	ctx        context.Context
+	client     tokenReviewInterface
+}
+
+func (a *authHandler) authorize(token string) (bool, error) {
+	tr := &authenticationv1.TokenReview{
+		Spec: authenticationv1.TokenReviewSpec{
+			Token: token,
+		},
+	}
+	result, err := a.client.Create(a.ctx, tr, metav1.CreateOptions{})
+	if err != nil {
+		return false, fmt.Errorf("failed to check token: %w", err)
+	}
+	isAuthenticated := result.Status.Authenticated
+	isPrometheus := result.Status.User.Username == "system:serviceaccount:openshift-monitoring:prometheus-k8s"
+	if !isAuthenticated {
+		klog.V(4).Info("The token cannot be authenticated.")
+	} else if !isPrometheus {
+		klog.V(4).Infof("Access the metrics from the unexpected user %s is denied.", result.Status.User.Username)
+	}
+	return isAuthenticated && isPrometheus, nil
+}
+
+func (a *authHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	authHeader := r.Header.Get("Authorization")
+	if authHeader == "" {
+		http.Error(w, "failed to get the Authorization header", http.StatusUnauthorized)
+		return
+	}
+	token := strings.TrimPrefix(authHeader, "Bearer ")
+	if token == "" {
+		http.Error(w, "empty Bearer token", http.StatusUnauthorized)
+		return
+	}
+	if token == authHeader {
+		http.Error(w, "failed to get the Bearer token", http.StatusUnauthorized)
+		return
+	}
+
+	authorized, err := a.authorize(token)
+	if err != nil {
+		klog.Warningf("Failed to authorize token: %v", err)
+		http.Error(w, "failed to authorize due to an internal error", http.StatusInternalServerError)
+		return
+	}
+	if !authorized {
+		http.Error(w, "failed to authorize", http.StatusUnauthorized)
+		return
+	}
+	a.downstream.ServeHTTP(w, r)
+}
+
 func shutdownHttpServer(parentCtx context.Context, svr *http.Server) {
 	ctx, cancel := context.WithTimeout(parentCtx, 5*time.Second)
 	defer cancel()
@@ -181,7 +246,7 @@ func handleServerResult(result asyncResult, lastLoopError error) error {
 // Also detects changes to metrics certificate files upon which
 // the metrics HTTP server is shutdown and recreated with a new
 // TLS configuration.
-func RunMetrics(runContext context.Context, shutdownContext context.Context, listenAddress, certFile, keyFile string) error {
+func RunMetrics(runContext context.Context, shutdownContext context.Context, listenAddress, certFile, keyFile string, restConfig *rest.Config) error {
 	var tlsConfig *tls.Config
 	if listenAddress != "" {
 		var err error
@@ -192,7 +257,13 @@ func RunMetrics(runContext context.Context, shutdownContext context.Context, lis
 	} else {
 		return errors.New("TLS configuration is required to serve metrics")
 	}
-	server := createHttpServer()
+
+	client, err := authenticationclientsetv1.NewForConfig(restConfig)
+	if err != nil {
+		return fmt.Errorf("failed to create config: %w", err)
+	}
+
+	server := createHttpServer(runContext, client)
 
 	resultChannel := make(chan asyncResult, 1)
 	resultChannelCount := 1
@@ -246,7 +317,7 @@ func RunMetrics(runContext context.Context, shutdownContext context.Context, lis
 			case result := <-resultChannel: // crashed before a shutdown was requested or metrics server recreated
 				if restartServer {
 					klog.Info("Creating metrics server with updated TLS configuration.")
-					server = createHttpServer()
+					server = createHttpServer(runContext, client)
 					go startListening(server, tlsConfig, listenAddress, resultChannel)
 					restartServer = false
 					continue

pkg/cvo/metrics_test.go

@@ -1,15 +1,22 @@
 package cvo
 
 import (
+	"context"
 	"errors"
+	"fmt"
+	"io"
+	"net/http"
+	"net/http/httptest"
 	"sort"
 	"strings"
 	"testing"
 	"time"
 
 	"github.com/davecgh/go-spew/spew"
+	"github.com/google/go-cmp/cmp"
 	"github.com/prometheus/client_golang/prometheus"
 	dto "github.com/prometheus/client_model/go"
+	authenticationv1 "k8s.io/api/authentication/v1"
 	corev1 "k8s.io/api/core/v1"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/client-go/tools/record"
@@ -1009,3 +1016,154 @@ func metricParts(t *testing.T, metric prometheus.Metric, labels ...string) strin
 	}
 	return strings.Join(parts, " ")
 }
+
+type fakeClient struct {
+}
+
+func (c *fakeClient) Create(_ context.Context, tokenReview *authenticationv1.TokenReview, _ metav1.CreateOptions) (*authenticationv1.TokenReview, error) {
+	if tokenReview != nil {
+		ret := tokenReview.DeepCopy()
+		if tokenReview.Spec.Token == "good" {
+			ret.Status.Authenticated = true
+			ret.Status.User.Username = "system:serviceaccount:openshift-monitoring:prometheus-k8s"
+		}
+		if tokenReview.Spec.Token == "authenticated" {
+			ret.Status.Authenticated = true
+		}
+		if tokenReview.Spec.Token == "error" {
+			return nil, errors.New("fake error")
+		}
+		return ret, nil
+	}
+	return nil, errors.New("nil input")
+}
+
+type okHandler struct {
+}
+
+func (h *okHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	_, _ = fmt.Fprintf(w, "ok")
+}
+
+func Test_authHandler(t *testing.T) {
+	tests := []struct {
+		name               string
+		handler            *authHandler
+		method             string
+		body               io.Reader
+		headerKey          string
+		headerValue        string
+		expectedStatusCode int
+		expectedBody       string
+	}{
+		{
+			name: "good",
+			handler: &authHandler{
+				ctx:        context.TODO(),
+				downstream: &okHandler{},
+				client:     &fakeClient{},
+			},
+			method:             "GET",
+			headerKey:          "Authorization",
+			headerValue:        "Bearer good",
+			expectedStatusCode: http.StatusOK,
+			expectedBody:       "ok",
+		},
+		{
+			name: "empty bearer token",
+			handler: &authHandler{
+				ctx:        context.TODO(),
+				downstream: &okHandler{},
+				client:     &fakeClient{},
+			},
+			method:             "GET",
+			headerKey:          "Authorization",
+			headerValue:        "Bearer ",
+			expectedStatusCode: 401,
+			expectedBody:       "empty Bearer token\n",
+		},
+		{
+			name: "authenticated",
+			handler: &authHandler{
+				ctx:        context.TODO(),
+				downstream: &okHandler{},
+				client:     &fakeClient{},
+			},
+			method:             "GET",
+			headerKey:          "Authorization",
+			headerValue:        "Bearer authenticated",
+			expectedStatusCode: 401,
+			expectedBody:       "failed to authorize\n",
+		},
+		{
+			name: "bad",
+			handler: &authHandler{
+				ctx:        context.TODO(),
+				downstream: &okHandler{},
+				client:     &fakeClient{},
+			},
+			method:             "GET",
+			headerKey:          "Authorization",
+			headerValue:        "Bearer bad",
+			expectedStatusCode: 401,
+			expectedBody:       "failed to authorize\n",
+		},
+		{
+			name: "failed to get the Authorization header",
+			handler: &authHandler{
+				ctx:        context.TODO(),
+				downstream: &okHandler{},
+				client:     &fakeClient{},
+			},
+			method:             "GET",
+			expectedStatusCode: 401,
+			expectedBody:       "failed to get the Authorization header\n",
+		},
+		{
+			name: "failed to get the Bearer token",
+			handler: &authHandler{
+				ctx:        context.TODO(),
+				downstream: &okHandler{},
+				client:     &fakeClient{},
+			},
+			method:             "GET",
+			headerKey:          "Authorization",
+			headerValue:        "xxx bad",
+			expectedStatusCode: 401,
+			expectedBody:       "failed to get the Bearer token\n",
+		},
+		{
+			name: "error",
+			handler: &authHandler{
+				ctx:        context.TODO(),
+				downstream: &okHandler{},
+				client:     &fakeClient{},
+			},
+			method:             "GET",
+			headerKey:          "Authorization",
+			headerValue:        "Bearer error",
+			expectedStatusCode: 500,
+			expectedBody:       "failed to authorize due to an internal error\n",
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			rr := httptest.NewRecorder()
+
+			req, err := http.NewRequest(tt.method, "url-not-important", tt.body)
+			if err != nil {
+				t.Fatal(err)
+			}
+			req.Header.Set(tt.headerKey, tt.headerValue)
+
+			tt.handler.ServeHTTP(rr, req)
+			if diff := cmp.Diff(tt.expectedStatusCode, rr.Code); diff != "" {
+				t.Errorf("%s: status differs from expected:\n%s", tt.name, diff)
+			}
+
+			if diff := cmp.Diff(tt.expectedBody, rr.Body.String()); diff != "" {
+				t.Errorf("%s: body differs from expected:\n%s", tt.name, diff)
+			}
+		})
+	}
+}

pkg/start/start.go

@@ -255,7 +255,7 @@ func (o *Options) run(ctx context.Context, controllerCtx *Context, lock resource
 						resultChannelCount++
 						go func() {
 							defer utilruntime.HandleCrash()
-							err := cvo.RunMetrics(postMainContext, shutdownContext, o.ListenAddr, o.ServingCertFile, o.ServingKeyFile)
+							err := cvo.RunMetrics(postMainContext, shutdownContext, o.ListenAddr, o.ServingCertFile, o.ServingKeyFile, restConfig)
 							resultChannel <- asyncResult{name: "metrics server", error: err}
 						}()
 					}