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webhook: Handle TLS certificate rotation
This watches the configured TLS certificate and key files for admission webhooks. On any change, it attempts to reload them from disk.
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/* | ||
Copyright 2019 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. | ||
*/ | ||
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package certwatcher | ||
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import ( | ||
"crypto/tls" | ||
"sync" | ||
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"gopkg.in/fsnotify.v1" | ||
logf "sigs.k8s.io/controller-runtime/pkg/internal/log" | ||
) | ||
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var log = logf.RuntimeLog.WithName("certwatcher") | ||
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// CertWatcher watches certificate and key files for changes. When either file | ||
// changes, it reads and parses both and calls an optional callback with the new | ||
// certificate. | ||
type CertWatcher struct { | ||
sync.Mutex | ||
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currentCert *tls.Certificate | ||
watcher *fsnotify.Watcher | ||
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certPath string | ||
keyPath string | ||
} | ||
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// New returns a new CertWatcher watching the given certificate and key. | ||
func New(certPath, keyPath string) (*CertWatcher, error) { | ||
var err error | ||
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cw := &CertWatcher{ | ||
certPath: certPath, | ||
keyPath: keyPath, | ||
} | ||
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// Initial read of certificate and key. | ||
if err := cw.ReadCertificate(); err != nil { | ||
return nil, err | ||
} | ||
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cw.watcher, err = fsnotify.NewWatcher() | ||
if err != nil { | ||
return nil, err | ||
} | ||
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return cw, nil | ||
} | ||
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// GetCertificate fetches the currently loaded certificate, which may be nil. | ||
func (cw *CertWatcher) GetCertificate(_ *tls.ClientHelloInfo) (*tls.Certificate, error) { | ||
cw.Lock() | ||
defer cw.Unlock() | ||
return cw.currentCert, nil | ||
} | ||
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// Start starts the watch on the certificate and key files. | ||
func (cw *CertWatcher) Start(stopCh <-chan struct{}) error { | ||
files := []string{cw.certPath, cw.keyPath} | ||
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for _, f := range files { | ||
if err := cw.watcher.Add(f); err != nil { | ||
return err | ||
} | ||
} | ||
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go cw.Watch() | ||
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log.Info("Starting certificate watcher") | ||
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// Block until the stop channel is closed. | ||
<-stopCh | ||
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return cw.watcher.Close() | ||
} | ||
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// Watch reads events from the watcher's channel and reacts to changes. | ||
func (cw *CertWatcher) Watch() { | ||
for { | ||
select { | ||
case event, ok := <-cw.watcher.Events: | ||
// Channel is closed. | ||
if !ok { | ||
return | ||
} | ||
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cw.handleEvent(event) | ||
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case err, ok := <-cw.watcher.Errors: | ||
// Channel is closed. | ||
if !ok { | ||
return | ||
} | ||
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log.Error(err, "certificate watch error") | ||
} | ||
} | ||
} | ||
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// ReadCertificate reads the certificate and key files from disk, parses them, | ||
// and updates the current certificate on the watcher. If a callback is set, it | ||
// is invoked with the new certificate. | ||
func (cw *CertWatcher) ReadCertificate() error { | ||
cert, err := tls.LoadX509KeyPair(cw.certPath, cw.keyPath) | ||
if err != nil { | ||
return err | ||
} | ||
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cw.Lock() | ||
cw.currentCert = &cert | ||
cw.Unlock() | ||
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log.Info("Updated current TLS certiface") | ||
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return nil | ||
} | ||
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func (cw *CertWatcher) handleEvent(event fsnotify.Event) { | ||
// Only care about events which may modify the contents of the file. | ||
if !(isWrite(event) || isRemove(event) || isCreate(event)) { | ||
return | ||
} | ||
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log.V(1).Info("certificate event", "event", event) | ||
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// If the file was removed, re-add the watch. | ||
if isRemove(event) { | ||
if err := cw.watcher.Add(event.Name); err != nil { | ||
log.Error(err, "error re-watching file") | ||
} | ||
} | ||
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if err := cw.ReadCertificate(); err != nil { | ||
log.Error(err, "error re-reading certificate") | ||
} | ||
} | ||
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func isWrite(event fsnotify.Event) bool { | ||
return event.Op&fsnotify.Write == fsnotify.Write | ||
} | ||
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func isCreate(event fsnotify.Event) bool { | ||
return event.Op&fsnotify.Create == fsnotify.Create | ||
} | ||
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func isRemove(event fsnotify.Event) bool { | ||
return event.Op&fsnotify.Remove == fsnotify.Remove | ||
} |
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