dev: Use system certs if not insecure

pkg/source/chirpstack/config/config.go

@@ -105,13 +105,6 @@ func (c *Config) Initialize() error {
 	if err := c.JoinEUI.UnmarshalText([]byte(c.joinEUI)); err != nil {
 		return errInvalidJoinEUI.WithAttributes("join_eui", c.joinEUI)
 	}
-
-	if !c.insecure && c.caPath != "" {
-		if err := setCustomCA(c.caPath); err != nil {
-			return err
-		}
-	}
-
 	err := c.dialGRPC(
 		grpc.FailOnNonTempDialError(true),
 		grpc.WithBlock(),
@@ -125,11 +118,14 @@ func (c *Config) Initialize() error {
 }
 
 func (c *Config) dialGRPC(opts ...grpc.DialOption) error {
-	if c.insecure || c.caPath == "" {
+	if c.insecure {
 		opts = append(opts, grpc.WithTransportCredentials(insecure.NewCredentials()))
-	}
-	if tls := http.DefaultTransport.(*http.Transport).TLSClientConfig; tls != nil {
-		opts = append(opts, grpc.WithTransportCredentials(credentials.NewTLS(tls)))
+	} else {
+		tlsConfig, err := generateTLSConfig(c.caPath)
+		if err != nil {
+			return err
+		}
+		opts = append(opts, grpc.WithTransportCredentials(credentials.NewTLS(tlsConfig)))
 	}
 
 	ctx, cancel := context.WithTimeout(context.Background(), dialTimeout)
@@ -143,18 +139,24 @@ func (c *Config) dialGRPC(opts ...grpc.DialOption) error {
 	return nil
 }
 
-func setCustomCA(path string) error {
-	pemBytes, err := os.ReadFile(path)
-	if err != nil {
-		return err
+// GenerateTLSConfig generates a TLS configuration.
+func generateTLSConfig(caPath string) (cfg *tls.Config, err error) {
+	cfg = http.DefaultTransport.(*http.Transport).TLSClientConfig
+	if cfg == nil {
+		cfg = &tls.Config{}
 	}
-	rootCAs := http.DefaultTransport.(*http.Transport).TLSClientConfig.RootCAs
-	if rootCAs == nil {
-		if rootCAs, err = x509.SystemCertPool(); err != nil {
-			rootCAs = x509.NewCertPool()
+	if cfg.RootCAs == nil {
+		if cfg.RootCAs, err = x509.SystemCertPool(); err != nil {
+			cfg.RootCAs = x509.NewCertPool()
 		}
 	}
-	rootCAs.AppendCertsFromPEM(pemBytes)
-	http.DefaultTransport.(*http.Transport).TLSClientConfig = &tls.Config{RootCAs: rootCAs}
-	return nil
+	if caPath == "" {
+		return cfg, nil
+	}
+	pemBytes, err := os.ReadFile(caPath)
+	if err != nil {
+		return nil, err
+	}
+	cfg.RootCAs.AppendCertsFromPEM(pemBytes)
+	return cfg, nil
 }