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Watch TLS cert file changes to update certs when needed. (#20)
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,179 @@ | ||
| /* | ||
| Copyright 2021 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. | ||
| */ | ||
|
|
||
| package certwatcher | ||
|
|
||
| import ( | ||
| "context" | ||
| "crypto/tls" | ||
| "log" | ||
| "sync" | ||
|
|
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| "github.com/fsnotify/fsnotify" | ||
| ) | ||
|
|
||
| var ( | ||
| VerboseLogs bool | ||
| Logger *log.Logger | ||
| ) | ||
|
|
||
| func logf(format string, args ...any) { | ||
| if Logger != nil { | ||
| Logger.Printf(format, args...) | ||
| } else { | ||
| log.Printf(format, args...) | ||
| } | ||
| } | ||
|
|
||
| func vlogf(format string, args ...any) { | ||
| if VerboseLogs { | ||
| logf(format, args...) | ||
| } | ||
| } | ||
|
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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.RWMutex | ||
|
|
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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.RLock() | ||
| defer cw.RUnlock() | ||
| return cw.currentCert, nil | ||
| } | ||
|
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| // Start starts the watch on the certificate and key files. | ||
| func (cw *CertWatcher) Start(ctx context.Context) error { | ||
| files := []string{cw.certPath, cw.keyPath} | ||
|
|
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| for _, f := range files { | ||
| if err := cw.watcher.Add(f); err != nil { | ||
| logf("error watching file: %s", err) | ||
| return err | ||
| } | ||
| } | ||
|
|
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| go cw.Watch() | ||
|
|
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| // Block until the context is done. | ||
| <-ctx.Done() | ||
|
|
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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) | ||
|
|
||
| case err, ok := <-cw.watcher.Errors: | ||
| // Channel is closed. | ||
| if !ok { | ||
| return | ||
| } | ||
|
|
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| logf("certificate watch error: %s", err) | ||
| } | ||
| } | ||
| } | ||
|
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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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| vlogf("updated current TLS certificate") | ||
|
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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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| vlogf("certificate event: %s", 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 { | ||
| logf("error re-watching file: %s", err) | ||
| } | ||
| } | ||
|
|
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| if err := cw.ReadCertificate(); err != nil { | ||
| logf("error re-reading certificate: %s", err) | ||
| } | ||
| } | ||
|
|
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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 | ||
| } |