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[WIP] *: watch tls certificate changes #45
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,172 @@ | ||
| /* | ||
| Copyright 2017 Frederic Branczyk All rights reserved. | ||
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| 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 | ||
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| http://www.apache.org/licenses/LICENSE-2.0 | ||
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| 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 tls | ||
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| import ( | ||
| "context" | ||
| "crypto/tls" | ||
| "fmt" | ||
| "os" | ||
| "path/filepath" | ||
| "sync" | ||
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| "github.com/fsnotify/fsnotify" | ||
| "github.com/golang/glog" | ||
| ) | ||
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| // CertReloader is the struct that parses a certificate/key pair, | ||
| // providing a goroutine safe GetCertificate method to retrieve the parsed content. | ||
| // | ||
| // The GetCertificate signature is compatible with https://golang.org/pkg/crypto/tls/#Config.GetCertificate | ||
| // and can be used to hot-reload a certificate/key pair. | ||
| // | ||
| // For hot-reloading the Watch method must be started explicitly. | ||
| type CertReloader struct { | ||
| certPath, keyPath string | ||
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| // contains the watch targets (keys) | ||
| // and the watch locations (values) | ||
| watchables map[string]string | ||
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| mu sync.RWMutex // protects the fields below | ||
| cert *tls.Certificate | ||
| } | ||
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| func NewCertReloader(certPath, keyPath string) (*CertReloader, error) { | ||
| watchables := make(map[string]string) | ||
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| w, in, err := newWatchable(certPath) | ||
| if err != nil { | ||
| return nil, fmt.Errorf("error adding cert watchable: %v", err) | ||
| } | ||
| watchables[w] = in | ||
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| w, in, err = newWatchable(keyPath) | ||
| if err != nil { | ||
| return nil, fmt.Errorf("error adding key watchable: %v", err) | ||
| } | ||
| watchables[w] = in | ||
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| r := &CertReloader{ | ||
| certPath: certPath, | ||
| keyPath: keyPath, | ||
| watchables: watchables, | ||
| } | ||
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| if err := r.reload(); err != nil { | ||
| return nil, fmt.Errorf("error loading certificates: %v", err) | ||
| } | ||
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| return r, nil | ||
| } | ||
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| func newWatchable(target string) (watchable, in string, _ error) { | ||
| // simple case: the target is a file. | ||
| // in that case we watch for changes in its own directory. | ||
| watchable = filepath.Clean(target) | ||
| in, _ = filepath.Split(target) | ||
| in = filepath.Clean(in) | ||
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| stat, err := os.Lstat(target) | ||
| if err != nil { | ||
| return "", "", fmt.Errorf("lstat on %q failed: %v", target, err) | ||
| } | ||
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| // k8s case: the target is a symlink. | ||
| // Here, we watch the intermediate symlink (named `..data`) | ||
| // in the same directory as the target. | ||
| if stat.Mode()&os.ModeSymlink != 0 { | ||
| dest, err := os.Readlink(target) | ||
| if err != nil { | ||
| return "", "", fmt.Errorf("lstat on %q failed: %v", target, err) | ||
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| } | ||
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| watchable, _ = filepath.Split(dest) | ||
| watchable = filepath.Clean(watchable) | ||
| } | ||
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| return | ||
| } | ||
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| // Watch watches the configured certificate and key path and blocks the current goroutine | ||
| // until the scenario context is done or an error occurred during reloading. | ||
| func (r *CertReloader) Watch(ctx context.Context) error { | ||
| watcher, err := fsnotify.NewWatcher() | ||
| if err != nil { | ||
| return fmt.Errorf("error creating fsnotify watcher: %v", err) | ||
| } | ||
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| for _, v := range r.watchables { | ||
| glog.V(4).Infof("watching: %q", v) | ||
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| if err := watcher.Add(v); err != nil { | ||
| return fmt.Errorf("error adding watchable: %v", err) | ||
| } | ||
| } | ||
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| for { | ||
| select { | ||
| case <-ctx.Done(): | ||
| return nil | ||
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| case event := <-watcher.Events: | ||
| glog.V(5).Infof("watcher event %v", event) | ||
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| if _, ok := r.watchables[filepath.Clean(event.Name)]; !ok { | ||
| continue | ||
| } | ||
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| if event.Op&(fsnotify.Write|fsnotify.Create) == 0 { | ||
| continue | ||
| } | ||
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| case err := <-watcher.Errors: | ||
| glog.Errorf("watch failed: %v", err) | ||
| continue | ||
| } | ||
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| if err := r.reload(); err != nil { | ||
| return fmt.Errorf("reloading failed: %v", err) | ||
| } | ||
| } | ||
| } | ||
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| func (r *CertReloader) reload() error { | ||
| r.mu.Lock() | ||
| defer r.mu.Unlock() | ||
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| glog.V(4).Info("reloading key ", r.keyPath, " certificate ", r.certPath) | ||
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| cert, err := tls.LoadX509KeyPair(r.certPath, r.keyPath) | ||
| if err != nil { | ||
| return fmt.Errorf("error loading certificate: %v", err) | ||
| } | ||
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| r.cert = &cert | ||
| return nil | ||
| } | ||
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| // GetCertificate returns the current valid certificate. | ||
| // The ClientHello message is ignored | ||
| // and is just there to be compatible with https://golang.org/pkg/crypto/tls/#Config.GetCertificate. | ||
| func (r *CertReloader) GetCertificate(_ *tls.ClientHelloInfo) (*tls.Certificate, error) { | ||
| r.mu.RLock() | ||
| defer r.mu.RUnlock() | ||
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| return r.cert, nil | ||
| } | ||
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I wonder if we, in addition should add a ticker anyways. I am not sure we have 100% guarantees to catch all file system events, cc @lucab.
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Curious: for this very case, why not just read the files once per minute and apply if they changed? For other cases I agree that reloading as quickly as possible when available makes perfect sense, but here we have a lot of time to apply cert rotation anyways no?
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sounds good yes, this will simplify a lot of things and we don't have to think about edge cases 👍 let me implement a ticker-only based approach here and reuse the implemented logic here for prometheus-config-reloader.