aperture: extract TLS configuration into function

aperture.go

@@ -99,70 +99,11 @@ func start() error {
 		Handler: handler,
 	}
 
-	// Create TLS certificates.
-	switch {
-	// When using autocert, we set a TLSConfig on the server so the key and
-	// cert file we pass in are ignored and don't need to exist.
-	case cfg.AutoCert:
-		serverName := cfg.ServerName
-		if serverName == "" {
-			return fmt.Errorf("servername option is required for " +
-				"secure operation")
-		}
-
-		certDir := filepath.Join(apertureDataDir, "autocert")
-		log.Infof("Configuring autocert for server %v with cache dir "+
-			"%v", serverName, certDir)
-
-		manager := autocert.Manager{
-			Cache:      autocert.DirCache(certDir),
-			Prompt:     autocert.AcceptTOS,
-			HostPolicy: autocert.HostWhitelist(serverName),
-		}
-
-		go func() {
-			err := http.ListenAndServe(
-				":http", manager.HTTPHandler(nil),
-			)
-			if err != nil {
-				log.Errorf("autocert http: %v", err)
-			}
-		}()
-		httpsServer.TLSConfig = &tls.Config{
-			GetCertificate: manager.GetCertificate,
-			CipherSuites:   http2TLSCipherSuites,
-			MinVersion:     tls.VersionTLS12,
-		}
-
-	// If we're not using autocert, we want to create self-signed TLS certs
-	// and save them at the specified location (if they don't already
-	// exist).
-	default:
-		tlsKeyFile := filepath.Join(apertureDataDir, defaultTLSKeyFilename)
-		tlsCertFile := filepath.Join(apertureDataDir, defaultTLSCertFilename)
-		if !fileExists(tlsCertFile) && !fileExists(tlsKeyFile) {
-			log.Infof("Generating TLS certificates...")
-			err := cert.GenCertPair(
-				"aperture autogenerated cert", tlsCertFile,
-				tlsKeyFile, nil, nil,
-				cert.DefaultAutogenValidity,
-			)
-			if err != nil {
-				return err
-			}
-			log.Infof("Done generating TLS certificates")
-		}
-
-		// Load the certs now so we can create a complete TLS config.
-		certData, _, err := cert.LoadCert(tlsCertFile, tlsKeyFile)
-		if err != nil {
-			return err
-		}
-		httpsServer.TLSConfig = &tls.Config{
-			Certificates: []tls.Certificate{certData},
-			CipherSuites: http2TLSCipherSuites,
-			MinVersion:   tls.VersionTLS12,
-		}
+	// Create TLS configuration by either creating new self-signed certs or
+	// trying to obtain one through Let's Encrypt.
+	httpsServer.TLSConfig, err = getTLSConfig(cfg.ServerName, cfg.AutoCert)
+	if err != nil {
+		return err
 	}
 
 	// The ListenAndServeTLS below will block until shut down or an error
@@ -258,6 +199,76 @@ func setupLogging(cfg *config) error {
 	return build.ParseAndSetDebugLevels(cfg.DebugLevel, logWriter)
 }
 
+// getTLSConfig returns a TLS configuration for either a self-signed certificate
+// or one obtained through Let's Encrypt.
+func getTLSConfig(serverName string, autoCert bool) (*tls.Config, error) {
+	var tlsKeyFile, tlsCertFile string
+	switch {
+	// When using autocert, we set a TLSConfig on the server so the key and
+	// cert file we pass in are ignored and don't need to exist.
+	case autoCert:
+		serverName := serverName
+		if serverName == "" {
+			return nil, fmt.Errorf("servername option is " +
+				"required for secure operation")
+		}
+
+		certDir := filepath.Join(apertureDataDir, "autocert")
+		log.Infof("Configuring autocert for server %v with cache dir "+
+			"%v", serverName, certDir)
+
+		manager := autocert.Manager{
+			Cache:      autocert.DirCache(certDir),
+			Prompt:     autocert.AcceptTOS,
+			HostPolicy: autocert.HostWhitelist(serverName),
+		}
+
+		go func() {
+			err := http.ListenAndServe(
+				":http", manager.HTTPHandler(nil),
+			)
+			if err != nil {
+				log.Errorf("autocert http: %v", err)
+			}
+		}()
+		return &tls.Config{
+			GetCertificate: manager.GetCertificate,
+			CipherSuites:   http2TLSCipherSuites,
+			MinVersion:     tls.VersionTLS12,
+		}, nil
+
+	// If we're not using autocert, we want to create self-signed TLS certs
+	// and save them at the specified location (if they don't already
+	// exist).
+	default:
+		tlsKeyFile = filepath.Join(apertureDataDir, defaultTLSKeyFilename)
+		tlsCertFile = filepath.Join(apertureDataDir, defaultTLSCertFilename)
+		if !fileExists(tlsCertFile) && !fileExists(tlsKeyFile) {
+			log.Infof("Generating TLS certificates...")
+			err := cert.GenCertPair(
+				"aperture autogenerated cert", tlsCertFile,
+				tlsKeyFile, nil, nil,
+				cert.DefaultAutogenValidity,
+			)
+			if err != nil {
+				return nil, err
+			}
+			log.Infof("Done generating TLS certificates")
+		}
+
+		// Load the certs now so we can return a complete TLS config.
+		certData, _, err := cert.LoadCert(tlsCertFile, tlsKeyFile)
+		if err != nil {
+			return nil, err
+		}
+		return &tls.Config{
+			Certificates: []tls.Certificate{certData},
+			CipherSuites: http2TLSCipherSuites,
+			MinVersion:   tls.VersionTLS12,
+		}, nil
+	}
+}
+
 // initTorListener initiates a Tor controller instance with the Tor server
 // specified in the config. Onion services will be created over which the proxy
 // can be reached at.