feat(metrics): import keypairreloader from a private project

Signed-off-by: Xe Iaso <me@xeiaso.net>
This commit is contained in:
Xe Iaso
2026-04-22 13:52:40 -04:00
parent 888c477933
commit 63e6a15280
3 changed files with 359 additions and 1 deletions
+81
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@@ -0,0 +1,81 @@
package metrics
import (
"crypto/tls"
"fmt"
"log/slog"
"os"
"sync"
"time"
)
type KeypairReloader struct {
certMu sync.RWMutex
cert *tls.Certificate
certPath string
keyPath string
modTime time.Time
lg *slog.Logger
}
func NewKeypairReloader(certPath, keyPath string, lg *slog.Logger) (*KeypairReloader, error) {
result := &KeypairReloader{
certPath: certPath,
keyPath: keyPath,
lg: lg,
}
cert, err := tls.LoadX509KeyPair(certPath, keyPath)
if err != nil {
return nil, err
}
result.cert = &cert
st, err := os.Stat(certPath)
if err != nil {
return nil, err
}
result.modTime = st.ModTime()
return result, nil
}
func (kpr *KeypairReloader) maybeReload() error {
kpr.lg.Debug("loading new keypair", "cert", kpr.certPath, "key", kpr.keyPath)
newCert, err := tls.LoadX509KeyPair(kpr.certPath, kpr.keyPath)
if err != nil {
return err
}
st, err := os.Stat(kpr.certPath)
if err != nil {
return err
}
kpr.certMu.Lock()
defer kpr.certMu.Unlock()
kpr.cert = &newCert
kpr.modTime = st.ModTime()
return nil
}
func (kpr *KeypairReloader) GetCertificate(*tls.ClientHelloInfo) (*tls.Certificate, error) {
st, err := os.Stat(kpr.certPath)
if err != nil {
return nil, fmt.Errorf("stat(%q): %w", kpr.certPath, err)
}
kpr.certMu.RLock()
needsReload := st.ModTime().After(kpr.modTime)
kpr.certMu.RUnlock()
if needsReload {
if err := kpr.maybeReload(); err != nil {
return nil, fmt.Errorf("reload cert: %w", err)
}
}
kpr.certMu.RLock()
defer kpr.certMu.RUnlock()
return kpr.cert, nil
}
+265
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@@ -0,0 +1,265 @@
package metrics
import (
"bytes"
"crypto/rand"
"crypto/rsa"
"crypto/x509"
"crypto/x509/pkix"
"encoding/pem"
"errors"
"log/slog"
"math/big"
"os"
"path/filepath"
"testing"
"time"
)
func discardLogger() *slog.Logger {
return slog.New(slog.DiscardHandler)
}
// writeKeypair generates a fresh self-signed cert + RSA key and writes them
// as PEM files in dir. Returns the paths and the cert's DER bytes so callers
// can identify which pair was loaded.
func writeKeypair(t *testing.T, dir, prefix string) (certPath, keyPath string, certDER []byte) {
t.Helper()
priv, err := rsa.GenerateKey(rand.Reader, 2048)
if err != nil {
t.Fatalf("rsa.GenerateKey: %v", err)
}
tmpl := &x509.Certificate{
SerialNumber: big.NewInt(time.Now().UnixNano()),
Subject: pkix.Name{CommonName: "keypairreloader-test"},
NotBefore: time.Now().Add(-time.Hour),
NotAfter: time.Now().Add(time.Hour),
KeyUsage: x509.KeyUsageDigitalSignature | x509.KeyUsageKeyEncipherment,
ExtKeyUsage: []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth},
BasicConstraintsValid: true,
DNSNames: []string{"keypairreloader-test"},
}
der, err := x509.CreateCertificate(rand.Reader, tmpl, tmpl, &priv.PublicKey, priv)
if err != nil {
t.Fatalf("x509.CreateCertificate: %v", err)
}
certPath = filepath.Join(dir, prefix+"cert.pem")
keyPath = filepath.Join(dir, prefix+"key.pem")
certPEM := pem.EncodeToMemory(&pem.Block{Type: "CERTIFICATE", Bytes: der})
keyPEM := pem.EncodeToMemory(&pem.Block{Type: "RSA PRIVATE KEY", Bytes: x509.MarshalPKCS1PrivateKey(priv)})
if err := os.WriteFile(certPath, certPEM, 0o600); err != nil {
t.Fatalf("write cert: %v", err)
}
if err := os.WriteFile(keyPath, keyPEM, 0o600); err != nil {
t.Fatalf("write key: %v", err)
}
return certPath, keyPath, der
}
func TestNewKeypairReloader(t *testing.T) {
dir := t.TempDir()
goodCert, goodKey, _ := writeKeypair(t, dir, "good-")
garbagePath := filepath.Join(dir, "garbage.pem")
if err := os.WriteFile(garbagePath, []byte("not a pem file"), 0o600); err != nil {
t.Fatalf("write garbage: %v", err)
}
tests := []struct {
name string
certPath string
keyPath string
wantErr error
wantNil bool
}{
{
name: "valid cert and key",
certPath: goodCert,
keyPath: goodKey,
},
{
name: "missing cert file",
certPath: filepath.Join(dir, "does-not-exist.pem"),
keyPath: goodKey,
wantErr: os.ErrNotExist,
wantNil: true,
},
{
name: "missing key file",
certPath: goodCert,
keyPath: filepath.Join(dir, "does-not-exist-key.pem"),
wantErr: os.ErrNotExist,
wantNil: true,
},
{
name: "cert file is garbage",
certPath: garbagePath,
keyPath: goodKey,
wantNil: true,
},
}
for _, tt := range tests {
t.Run(tt.name, func(t *testing.T) {
kpr, err := NewKeypairReloader(tt.certPath, tt.keyPath, discardLogger())
if tt.wantErr != nil && !errors.Is(err, tt.wantErr) {
t.Errorf("err = %v, want errors.Is(..., %v)", err, tt.wantErr)
}
if tt.wantErr == nil && !tt.wantNil && err != nil {
t.Errorf("unexpected err: %v", err)
}
if tt.wantNil && kpr != nil {
t.Errorf("kpr = %+v, want nil", kpr)
}
if !tt.wantNil && kpr == nil {
t.Errorf("kpr is nil, want non-nil")
}
})
}
}
func TestKeypairReloader_GetCertificate(t *testing.T) {
tests := []struct {
name string
run func(t *testing.T)
}{
{
name: "returns loaded cert",
run: func(t *testing.T) {
dir := t.TempDir()
certPath, keyPath, wantDER := writeKeypair(t, dir, "a-")
kpr, err := NewKeypairReloader(certPath, keyPath, discardLogger())
if err != nil {
t.Fatalf("NewKeypairReloader: %v", err)
}
got, err := kpr.GetCertificate(nil)
if err != nil {
t.Fatalf("GetCertificate: %v", err)
}
if len(got.Certificate) == 0 || !bytes.Equal(got.Certificate[0], wantDER) {
t.Errorf("GetCertificate returned wrong cert bytes")
}
},
},
{
name: "reloads when mtime advances",
run: func(t *testing.T) {
dir := t.TempDir()
certPath, keyPath, _ := writeKeypair(t, dir, "a-")
kpr, err := NewKeypairReloader(certPath, keyPath, discardLogger())
if err != nil {
t.Fatalf("NewKeypairReloader: %v", err)
}
// Overwrite with a new pair at the same paths and bump mtime.
newCertPath, newKeyPath, newDER := writeKeypair(t, dir, "b-")
mustRename(t, newCertPath, certPath)
mustRename(t, newKeyPath, keyPath)
future := time.Now().Add(time.Hour)
if err := os.Chtimes(certPath, future, future); err != nil {
t.Fatalf("Chtimes: %v", err)
}
got, err := kpr.GetCertificate(nil)
if err != nil {
t.Fatalf("GetCertificate: %v", err)
}
if len(got.Certificate) == 0 || !bytes.Equal(got.Certificate[0], newDER) {
t.Errorf("GetCertificate did not return reloaded cert")
}
},
},
{
name: "does not reload when mtime unchanged",
run: func(t *testing.T) {
dir := t.TempDir()
certPath, keyPath, originalDER := writeKeypair(t, dir, "a-")
kpr, err := NewKeypairReloader(certPath, keyPath, discardLogger())
if err != nil {
t.Fatalf("NewKeypairReloader: %v", err)
}
// Overwrite the cert/key files with a *different* keypair, then
// rewind mtime so the reloader must not pick up the change.
newCertPath, newKeyPath, newDER := writeKeypair(t, dir, "b-")
mustRename(t, newCertPath, certPath)
mustRename(t, newKeyPath, keyPath)
past := time.Unix(0, 0)
if err := os.Chtimes(certPath, past, past); err != nil {
t.Fatalf("Chtimes: %v", err)
}
got, err := kpr.GetCertificate(nil)
if err != nil {
t.Fatalf("GetCertificate: %v", err)
}
if len(got.Certificate) == 0 {
t.Fatal("empty cert chain")
}
if bytes.Equal(got.Certificate[0], newDER) {
t.Errorf("GetCertificate reloaded despite unchanged mtime")
}
if !bytes.Equal(got.Certificate[0], originalDER) {
t.Errorf("GetCertificate did not return original cert")
}
},
},
{
name: "does not panic when reload fails after mtime bump",
run: func(t *testing.T) {
dir := t.TempDir()
certPath, keyPath, _ := writeKeypair(t, dir, "a-")
kpr, err := NewKeypairReloader(certPath, keyPath, discardLogger())
if err != nil {
t.Fatalf("NewKeypairReloader: %v", err)
}
// Corrupt the cert file and bump mtime. maybeReload will fail.
if err := os.WriteFile(certPath, []byte("not a pem file"), 0o600); err != nil {
t.Fatalf("corrupt cert: %v", err)
}
future := time.Now().Add(time.Hour)
if err := os.Chtimes(certPath, future, future); err != nil {
t.Fatalf("Chtimes: %v", err)
}
defer func() {
if r := recover(); r != nil {
t.Fatalf("GetCertificate panicked on reload failure: %v", r)
}
}()
got, err := kpr.GetCertificate(nil)
if err == nil {
t.Errorf("GetCertificate returned nil err for corrupt cert; got %+v", got)
}
},
},
}
for _, tt := range tests {
t.Run(tt.name, func(t *testing.T) {
tt.run(t)
})
}
}
func mustRename(t *testing.T, from, to string) {
t.Helper()
if err := os.Rename(from, to); err != nil {
t.Fatalf("rename %q -> %q: %v", from, to, err)
}
}
+13 -1
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@@ -2,6 +2,7 @@ package metrics
import (
"context"
"crypto/tls"
"errors"
"fmt"
"log/slog"
@@ -62,6 +63,17 @@ func (s *Server) Run(ctx context.Context, done func()) error {
defer ln.Close()
if s.Config.TLS != nil {
kpr, err := NewKeypairReloader(s.Config.TLS.Certificate, s.Config.TLS.Key, lg)
if err != nil {
return fmt.Errorf("can't setup keypair reloader: %w", err)
}
srv.TLSConfig = &tls.Config{
GetCertificate: kpr.GetCertificate,
}
}
lg.Debug("listening for metrics", "url", metricsURL)
go func() {
@@ -75,7 +87,7 @@ func (s *Server) Run(ctx context.Context, done func()) error {
switch s.Config.TLS != nil {
case true:
if err := srv.ServeTLS(ln, s.Config.TLS.Certificate, s.Config.TLS.Key); !errors.Is(err, http.ErrServerClosed) {
if err := srv.ServeTLS(ln, "", ""); !errors.Is(err, http.ErrServerClosed) {
return fmt.Errorf("can't serve TLS metrics server: %w", err)
}
case false: