Move certificate handling into a separate module.

go.mod

@@ -5,6 +5,7 @@ go 1.13
 require (
 	github.com/at-wat/ebml-go v0.16.0
 	github.com/gorilla/websocket v1.4.2
+	github.com/jech/cert v0.0.0-20210819231831-aca735647728
 	github.com/jech/samplebuilder v0.0.0-20210711185346-d34c6dd315fb
 	github.com/pion/ice/v2 v2.1.10
 	github.com/pion/rtcp v1.2.6

go.sum

@@ -22,6 +22,10 @@ github.com/google/uuid v1.2.0/go.mod h1:TIyPZe4MgqvfeYDBFedMoGGpEw/LqOeaOT+nhxU+
 github.com/gorilla/websocket v1.4.2 h1:+/TMaTYc4QFitKJxsQ7Yye35DkWvkdLcvGKqM+x0Ufc=
 github.com/gorilla/websocket v1.4.2/go.mod h1:YR8l580nyteQvAITg2hZ9XVh4b55+EU/adAjf1fMHhE=
 github.com/hpcloud/tail v1.0.0/go.mod h1:ab1qPbhIpdTxEkNHXyeSf5vhxWSCs/tWer42PpOxQnU=
+github.com/jech/cert v0.0.0-20210819214059-b84cf5e78f7a h1:3VzfD0n6o2Y3FW6cluxqj535fT9Uq3ANaYkG1JuiADI=
+github.com/jech/cert v0.0.0-20210819214059-b84cf5e78f7a/go.mod h1:FXUA/zpiQfV4uBVN2kAwkf3X7pU7l1l2ovS45CsSYZs=
+github.com/jech/cert v0.0.0-20210819231831-aca735647728 h1:tN+W1ll2oKuJGMCaO1CRK4rr+xSRjVSfWmnKlACdx38=
+github.com/jech/cert v0.0.0-20210819231831-aca735647728/go.mod h1:FXUA/zpiQfV4uBVN2kAwkf3X7pU7l1l2ovS45CsSYZs=
 github.com/jech/samplebuilder v0.0.0-20210711185346-d34c6dd315fb h1:ctDbFqRHUmxTThbYcTP2cdOVOkECsvhNyQKqeEK7RQQ=
 github.com/jech/samplebuilder v0.0.0-20210711185346-d34c6dd315fb/go.mod h1:PXhvo7PKy8CVqirCgoNG2BIjwow2Zd6LwCTScabl584=
 github.com/kr/pretty v0.1.0 h1:L/CwN0zerZDmRFUapSPitk6f+Q3+0za1rQkzVuMiMFI=

webserver/certificate.go

-package webserver
-
-import (
-	"crypto/rand"
-	"crypto/rsa"
-	"crypto/tls"
-	"crypto/x509"
-	"errors"
-	"log"
-	"math/big"
-	"os"
-	"path/filepath"
-	"sync"
-	"sync/atomic"
-	"time"
-)
-
-type certInfo struct {
-	certificate *tls.Certificate
-	keyTime     time.Time
-	certTime    time.Time
-}
-
-// certMu protects writing to certificate
-var certMu sync.Mutex
-
-// certificate holds our current certificate, of type certInfo
-var certificate atomic.Value
-
-// generateCertificate generates a self-signed certficate
-func generateCertificate() (tls.Certificate, error) {
-	priv, err := rsa.GenerateKey(rand.Reader, 2048)
-	if err != nil {
-		return tls.Certificate{}, err
-	}
-
-	serialNumberLimit := new(big.Int).Lsh(big.NewInt(1), 128)
-	serialNumber, err := rand.Int(rand.Reader, serialNumberLimit)
-	now := time.Now()
-
-	template := x509.Certificate{
-		SerialNumber:          serialNumber,
-		NotBefore:             now,
-		NotAfter:              now.Add(365 * 24 * time.Hour),
-		KeyUsage:              x509.KeyUsageKeyEncipherment | x509.KeyUsageDigitalSignature,
-		ExtKeyUsage:           []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth},
-		BasicConstraintsValid: true,
-	}
-	bytes, err := x509.CreateCertificate(
-		rand.Reader, &template, &template, &priv.PublicKey, priv,
-	)
-	if err != nil {
-		return tls.Certificate{}, err
-	}
-
-	return tls.Certificate{
-		Certificate: [][]byte{bytes},
-		PrivateKey:  priv,
-	}, nil
-}
-
-func modTime(filename string) time.Time {
-	fi, err := os.Stat(filename)
-	if err != nil {
-		if !os.IsNotExist(err) {
-			log.Printf("%v: %v", filename, err)
-		}
-		return time.Time{}
-	}
-	return fi.ModTime()
-}
-
-// loadCertificate returns the current certificate if it is still valid.
-func loadCertificate(certFile string, certTime time.Time, keyFile string, keyTime time.Time) *certInfo {
-	info, ok := certificate.Load().(*certInfo)
-	if !ok {
-		return nil
-	}
-
-	if !info.certTime.Equal(certTime) || !info.keyTime.Equal(keyTime) {
-		return nil
-	}
-
-	return info
-}
-
-// storeCertificate returns the current certificate if it is still valid,
-// and either reads or generates a new one otherwise.
-func storeCertificate(certFile string, certTime time.Time, keyFile string, keyTime time.Time) (info *certInfo, err error) {
-	certMu.Lock()
-	defer certMu.Unlock()
-
-	// the certificate may have been updated since we checked
-	info = loadCertificate(certFile, certTime, keyFile, keyTime)
-	if info != nil {
-		return
-	}
-
-	var cert tls.Certificate
-	nocert := certTime.Equal(time.Time{})
-	nokey := keyTime.Equal(time.Time{})
-
-	if nocert != nokey {
-		err = errors.New("only one of cert.pem and key.pem exists")
-		return
-	} else if nokey {
-		log.Printf("Generating self-signed certificate")
-		cert, err = generateCertificate()
-		if err != nil {
-			return
-		}
-	} else {
-		cert, err = tls.LoadX509KeyPair(certFile, keyFile)
-		if err != nil {
-			return
-		}
-	}
-	info = &certInfo{
-		certificate: &cert,
-		certTime:    certTime,
-		keyTime:     keyTime,
-	}
-	certificate.Store(info)
-	return
-}
-
-func getCertificate(dataDir string) (*tls.Certificate, error) {
-	certFile := filepath.Join(dataDir, "cert.pem")
-	keyFile := filepath.Join(dataDir, "key.pem")
-	certTime := modTime(certFile)
-	keyTime := modTime(keyFile)
-
-	info := loadCertificate(certFile, certTime, keyFile, keyTime)
-
-	if info == nil {
-		var err error
-		info, err = storeCertificate(
-			certFile, certTime, keyFile, keyTime,
-		)
-		if info == nil || err != nil {
-			return nil, err
-		}
-	}
-	return info.certificate, nil
-}

webserver/certificate_test.go

-package webserver
-
-import (
-	"testing"
-)
-
-func TestGenerateCertificate(t *testing.T) {
-	_, err := generateCertificate()
-	if err != nil {
-		t.Errorf("generateCertificate: %v", err)
-	}
-}
-
-func BenchmarkGenerateCertificate(b *testing.B) {
-	for i := 0; i < b.N; i++ {
-		_, err := generateCertificate()
-		if err != nil {
-			b.Errorf("generateCertificate: %v", err)
-		}
-	}
-}
-
-func TestGetCertificate(t *testing.T) {
-	cert1, err := getCertificate("/tmp/no/such/file")
-	if err != nil {
-		t.Errorf("getCertificate: %v", err)
-	}
-
-	cert2, err := getCertificate("/tmp/no/such/file")
-	if err != nil {
-		t.Errorf("getCertificate: %v", err)
-	}
-
-	if cert1 != cert2 {
-		t.Errorf("cert1 != cert2")
-	}
-}
-
-func BenchmarkGetCertificate(b *testing.B) {
-	_, err := getCertificate("/tmp/no/such/file")
-	if err != nil {
-		b.Errorf("getCertificate: %v", err)
-	}
-	b.StartTimer()
-	for i := 0; i < b.N; i++ {
-		_, err := getCertificate("/tmp/no/such/file")
-		if err != nil {
-			b.Errorf("getCertificate: %v", err)
-		}
-	}
-}

webserver/webserver.go

@@ -22,6 +22,7 @@ import (
 
 	"github.com/gorilla/websocket"
 
+	"github.com/jech/cert"
 	"github.com/jech/galene/diskwriter"
 	"github.com/jech/galene/group"
 	"github.com/jech/galene/rtpconn"
@@ -58,9 +59,13 @@ func Serve(address string, dataDir string) error {
 		IdleTimeout:       120 * time.Second,
 	}
 	if !Insecure {
+		certificate := cert.New(
+			filepath.Join(dataDir, "cert.pem"),
+			filepath.Join(dataDir, "key.pem"),
+		)
 		s.TLSConfig = &tls.Config{
 			GetCertificate: func(hello *tls.ClientHelloInfo) (*tls.Certificate, error) {
-				return getCertificate(dataDir)
+				return certificate.Get()
 			},
 		}
 	}