Network component should refresh certificates if they expire

A single process openshift start node has both kubelet and network.
Kubelet rotates its client certs - network does not. Until we split out
network we need to do something minimal to ensure the cert is refreshed.
Use the same code as the kubelet, but when the cert expires check disk
and see if it was refreshed. That should work for bootstrapped
environments because the file is updated.

Author: smarterclayton

pkg/cmd/server/kubernetes/network/network_config.go

@@ -3,16 +3,20 @@ package network
 import (
 	"fmt"
 	"net"
+	"time"
 
 	miekgdns "github.com/miekg/dns"
 
+	utilruntime "k8s.io/apimachinery/pkg/util/runtime"
+	utilwait "k8s.io/apimachinery/pkg/util/wait"
 	kclientset "k8s.io/client-go/kubernetes"
 	"k8s.io/kubernetes/pkg/apis/componentconfig"
 	kclientsetexternal "k8s.io/kubernetes/pkg/client/clientset_generated/clientset"
 	kclientsetinternal "k8s.io/kubernetes/pkg/client/clientset_generated/internalclientset"
 	kinternalinformers "k8s.io/kubernetes/pkg/client/informers/informers_generated/internalversion"
 
 	configapi "github.com/openshift/origin/pkg/cmd/server/api"
+	"github.com/openshift/origin/pkg/cmd/server/kubernetes/network/transport"
 	"github.com/openshift/origin/pkg/dns"
 	"github.com/openshift/origin/pkg/network"
 	networkclient "github.com/openshift/origin/pkg/network/generated/internalclientset"
@@ -48,6 +52,12 @@ func New(options configapi.NodeConfig, clusterDomain string, proxyConfig *compon
 	if err != nil {
 		return nil, err
 	}
+	// if a client cert is specified, when the certificate expires attempt to refresh it from disk
+	if len(kubeConfig.TLSClientConfig.KeyFile) > 0 && len(kubeConfig.TLSClientConfig.CertFile) > 0 {
+		if err := transport.RefreshCertificateAfterExpiry(utilwait.NeverStop, 10*time.Second, kubeConfig); err != nil {
+			utilruntime.HandleError(fmt.Errorf("Unable to enable client certificate rotation for network components: %v", err))
+		}
+	}
 	internalKubeClient, err := kclientsetinternal.NewForConfig(kubeConfig)
 	if err != nil {
 		return nil, err

pkg/cmd/server/kubernetes/network/transport/transport.go

@@ -0,0 +1,209 @@
+/*
+Copyright 2017 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.
+*/
+
+// Extracted from k8s.io/kubernetes/pkg/kubelet/certificate/transport.go, will be removed
+// when openshift-sdn and the network components move out of the Kubelet. Is intended ONLY
+// to provide certificate rollover until 3.8/3.9.
+package transport
+
+import (
+	"context"
+	"crypto/tls"
+	"fmt"
+	"net"
+	"net/http"
+	"sync"
+	"time"
+
+	"github.com/golang/glog"
+
+	utilnet "k8s.io/apimachinery/pkg/util/net"
+	utilruntime "k8s.io/apimachinery/pkg/util/runtime"
+	"k8s.io/apimachinery/pkg/util/wait"
+	restclient "k8s.io/client-go/rest"
+)
+
+// RefreshCertificateAfterExpiry instruments a restconfig with a transport that checks
+// disk to reload expired certificates.
+//
+// The config must not already provide an explicit transport.
+//
+// The returned transport periodically checks the manager to determine if the
+// certificate has changed. If it has, the transport shuts down all existing client
+// connections, forcing the client to re-handshake with the server and use the
+// new certificate.
+//
+// stopCh should be used to indicate when the transport is unused and doesn't need
+// to continue checking the manager.
+func RefreshCertificateAfterExpiry(stopCh <-chan struct{}, period time.Duration, clientConfig *restclient.Config) error {
+	if clientConfig.Transport != nil {
+		return fmt.Errorf("there is already a transport configured")
+	}
+	tlsConfig, err := restclient.TLSConfigFor(clientConfig)
+	if err != nil {
+		return fmt.Errorf("unable to configure TLS for the rest client: %v", err)
+	}
+	if tlsConfig == nil {
+		tlsConfig = &tls.Config{}
+	}
+	manager := &certificateManager{config: *clientConfig, minimumRefresh: period}
+	tlsConfig.Certificates = nil
+	tlsConfig.GetClientCertificate = func(requestInfo *tls.CertificateRequestInfo) (*tls.Certificate, error) {
+		cert := manager.Current()
+		if cert == nil {
+			return &tls.Certificate{Certificate: nil}, nil
+		}
+		return cert, nil
+	}
+
+	// Custom dialer that will track all connections it creates.
+	t := &connTracker{
+		dialer: &net.Dialer{Timeout: 30 * time.Second, KeepAlive: 30 * time.Second},
+		conns:  make(map[*closableConn]struct{}),
+	}
+
+	lastCert := manager.Current()
+	go wait.Until(func() {
+		curr := manager.Current()
+		if curr == nil || lastCert == curr {
+			// Cert hasn't been rotated.
+			return
+		}
+		lastCert = curr
+
+		glog.Infof("certificate rotation detected, shutting down client connections to start using new credentials")
+		// The cert has been rotated. Close all existing connections to force the client
+		// to reperform its TLS handshake with new cert.
+		//
+		// See: https://github.com/kubernetes-incubator/bootkube/pull/663#issuecomment-318506493
+		t.closeAllConns()
+	}, period, stopCh)
+
+	clientConfig.Transport = utilnet.SetTransportDefaults(&http.Transport{
+		Proxy:               http.ProxyFromEnvironment,
+		TLSHandshakeTimeout: 10 * time.Second,
+		TLSClientConfig:     tlsConfig,
+		MaxIdleConnsPerHost: 25,
+		DialContext:         t.DialContext, // Use custom dialer.
+	})
+
+	// Zero out all existing TLS options since our new transport enforces them.
+	clientConfig.CertData = nil
+	clientConfig.KeyData = nil
+	clientConfig.CertFile = ""
+	clientConfig.KeyFile = ""
+	clientConfig.CAData = nil
+	clientConfig.CAFile = ""
+	clientConfig.Insecure = false
+	return nil
+}
+
+// certificateManager reloads the requested certificate from disk when requested.
+type certificateManager struct {
+	config         restclient.Config
+	minimumRefresh time.Duration
+
+	lock      sync.Mutex
+	cert      *tls.Certificate
+	lastCheck time.Time
+}
+
+// Current retrieves the latest certificate from disk if it exists, or nil if
+// no certificate could be found. The last successfully loaded certificate will be
+// returned.
+func (m *certificateManager) Current() *tls.Certificate {
+	m.lock.Lock()
+	defer m.lock.Unlock()
+
+	// check whether the cert has expired and whether we've waited long enough since our last
+	// check to look again
+	cert := m.cert
+	if cert != nil {
+		now := time.Now()
+		if now.After(m.cert.Leaf.NotAfter) {
+			if now.Sub(m.lastCheck) > m.minimumRefresh {
+				cert = nil
+				m.lastCheck = now
+			}
+		}
+	}
+
+	// load the cert from disk
+	if cert == nil {
+		c, err := tls.LoadX509KeyPair(m.config.CertFile, m.config.KeyFile)
+		if err != nil {
+			utilruntime.HandleError(fmt.Errorf("Unable to load client certificate key pair from disk: %v", err))
+			return nil
+		}
+		m.cert = &c
+	}
+	return m.cert
+}
+
+// connTracker is a dialer that tracks all open connections it creates.
+type connTracker struct {
+	dialer *net.Dialer
+
+	mu    sync.Mutex
+	conns map[*closableConn]struct{}
+}
+
+// closeAllConns forcibly closes all tracked connections.
+func (c *connTracker) closeAllConns() {
+	c.mu.Lock()
+	conns := c.conns
+	c.conns = make(map[*closableConn]struct{})
+	c.mu.Unlock()
+
+	for conn := range conns {
+		conn.Close()
+	}
+}
+
+func (c *connTracker) DialContext(ctx context.Context, network, address string) (net.Conn, error) {
+	conn, err := c.dialer.DialContext(ctx, network, address)
+	if err != nil {
+		return nil, err
+	}
+
+	closable := &closableConn{Conn: conn}
+
+	// Start tracking the connection
+	c.mu.Lock()
+	c.conns[closable] = struct{}{}
+	c.mu.Unlock()
+
+	// When the connection is closed, remove it from the map. This will
+	// be no-op if the connection isn't in the map, e.g. if closeAllConns()
+	// is called.
+	closable.onClose = func() {
+		c.mu.Lock()
+		delete(c.conns, closable)
+		c.mu.Unlock()
+	}
+
+	return closable, nil
+}
+
+type closableConn struct {
+	onClose func()
+	net.Conn
+}
+
+func (c *closableConn) Close() error {
+	go c.onClose()
+	return c.Conn.Close()
+}