Add client certificate authentication support to core Authenticator

This is required to make the websocket tunnel server functional on
etcd-only nodes, and will save some code on the RKE2 side once pulled
through.

Signed-off-by: Brad Davidson <brad.davidson@rancher.com>
(cherry picked from commit af0b496ef3)

pkg/authenticator/authenticator.go

@@ -0,0 +1,56 @@
+package authenticator
+
+import (
+	"strings"
+
+	"github.com/rancher/k3s/pkg/authenticator/basicauth"
+	"github.com/rancher/k3s/pkg/authenticator/passwordfile"
+	"k8s.io/apiserver/pkg/authentication/authenticator"
+	"k8s.io/apiserver/pkg/authentication/group"
+	"k8s.io/apiserver/pkg/authentication/request/union"
+	"k8s.io/apiserver/pkg/authentication/request/x509"
+	"k8s.io/apiserver/pkg/server/dynamiccertificates"
+)
+
+func FromArgs(args []string) (authenticator.Request, error) {
+	var authenticators []authenticator.Request
+	basicFile := getArg("--basic-auth-file", args)
+	if basicFile != "" {
+		basicAuthenticator, err := passwordfile.NewCSV(basicFile)
+		if err != nil {
+			return nil, err
+		}
+		authenticators = append(authenticators, basicauth.New(basicAuthenticator))
+	}
+
+	clientCA := getArg("--client-ca-file", args)
+	if clientCA != "" {
+		ca, err := dynamiccertificates.NewDynamicCAContentFromFile("client-ca", clientCA)
+		if err != nil {
+			return nil, err
+		}
+		authenticators = append(authenticators, x509.NewDynamic(ca.VerifyOptions, x509.CommonNameUserConversion))
+	}
+
+	return Combine(authenticators...), nil
+}
+
+func getArg(key string, args []string) string {
+	for _, arg := range args {
+		if !strings.HasPrefix(arg, key) {
+			continue
+		}
+		return strings.SplitN(arg, "=", 2)[1]
+	}
+	return ""
+}
+
+func Combine(auths ...authenticator.Request) authenticator.Request {
+	var authenticators []authenticator.Request
+	for _, auth := range auths {
+		if auth != nil {
+			authenticators = append(authenticators, auth)
+		}
+	}
+	return group.NewAuthenticatedGroupAdder(union.New(authenticators...))
+}

pkg/authenticator/basicauth/basicauth.go

@@ -20,17 +20,16 @@ import (
 	"errors"
 	"net/http"
 
-	localAuthenticator "github.com/rancher/k3s/pkg/authenticator"
 	"k8s.io/apiserver/pkg/authentication/authenticator"
 )
 
 // Authenticator authenticates requests using basic auth
 type Authenticator struct {
-	auth localAuthenticator.Password
+	auth Password
 }
 
 // New returns a request authenticator that validates credentials using the provided password authenticator
-func New(auth localAuthenticator.Password) *Authenticator {
+func New(auth Password) *Authenticator {
 	return &Authenticator{auth}
 }
 

pkg/authenticator/basicauth/interfaces.go

@@ -11,7 +11,7 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-package authenticator
+package basicauth
 
 import (
 	"context"

pkg/daemons/control/auth.go

@@ -1,30 +0,0 @@
-package control
-
-import (
-	"github.com/rancher/k3s/pkg/authenticator/basicauth"
-	"github.com/rancher/k3s/pkg/authenticator/passwordfile"
-	"k8s.io/apiserver/pkg/authentication/authenticator"
-	"k8s.io/apiserver/pkg/authentication/group"
-	"k8s.io/apiserver/pkg/authentication/request/union"
-)
-
-func basicAuthenticator(basicAuthFile string) (authenticator.Request, error) {
-	if basicAuthFile == "" {
-		return nil, nil
-	}
-	basicAuthenticator, err := passwordfile.NewCSV(basicAuthFile)
-	if err != nil {
-		return nil, err
-	}
-	return basicauth.New(basicAuthenticator), nil
-}
-
-func combineAuthenticators(auths ...authenticator.Request) authenticator.Request {
-	var authenticators []authenticator.Request
-	for _, auth := range auths {
-		if auth != nil {
-			authenticators = append(authenticators, auth)
-		}
-	}
-	return group.NewAuthenticatedGroupAdder(union.New(authenticators...))
-}

pkg/daemons/control/server.go

@@ -12,6 +12,7 @@ import (
 	"time"
 
 	"github.com/pkg/errors"
+	"github.com/rancher/k3s/pkg/authenticator"
 	"github.com/rancher/k3s/pkg/cluster"
 	"github.com/rancher/k3s/pkg/daemons/config"
 	"github.com/rancher/k3s/pkg/daemons/control/deps"
@@ -50,11 +51,15 @@ func Server(ctx context.Context, cfg *config.Control) error {
 	cfg.Runtime.Tunnel = setupTunnel()
 	proxyutil.DisableProxyHostnameCheck = true
 
-	basicAuth, err := basicAuthenticator(cfg.Runtime.PasswdFile)
+	authArgs := []string{
+		"--basic-auth-file=" + cfg.Runtime.PasswdFile,
+		"--client-ca-file=" + cfg.Runtime.ClientCA,
+	}
+	auth, err := authenticator.FromArgs(authArgs)
 	if err != nil {
 		return err
 	}
-	cfg.Runtime.Authenticator = basicAuth
+	cfg.Runtime.Authenticator = auth
 
 	if !cfg.DisableAPIServer {
 		go waitForAPIServerHandlers(ctx, cfg.Runtime)
@@ -377,7 +382,7 @@ func waitForAPIServerHandlers(ctx context.Context, runtime *config.ControlRuntim
 	if err != nil {
 		logrus.Fatalf("Failed to get request handlers from apiserver: %v", err)
 	}
-	runtime.Authenticator = combineAuthenticators(runtime.Authenticator, auth)
+	runtime.Authenticator = authenticator.Combine(runtime.Authenticator, auth)
 	runtime.APIServer = handler
 }
 

pkg/daemons/control/tunnel.go

@@ -9,13 +9,20 @@ import (
 
 	"github.com/rancher/remotedialer"
 	"github.com/rancher/wrangler/pkg/kv"
+	"github.com/sirupsen/logrus"
 	utilnet "k8s.io/apimachinery/pkg/util/net"
 	"k8s.io/apiserver/pkg/endpoints/request"
 	"k8s.io/kubernetes/cmd/kube-apiserver/app"
 )
 
+func loggingErrorWriter(rw http.ResponseWriter, req *http.Request, code int, err error) {
+	logrus.Debugf("remoteDialer error: %d %v", code, err)
+	rw.WriteHeader(code)
+	rw.Write([]byte(err.Error()))
+}
+
 func setupTunnel() http.Handler {
-	tunnelServer := remotedialer.New(authorizer, remotedialer.DefaultErrorWriter)
+	tunnelServer := remotedialer.New(authorizer, loggingErrorWriter)
 	setupProxyDialer(tunnelServer)
 	return tunnelServer
 }