if err != nil {
			return
		}
		defer func() {
			caFile.Close()
			os.Remove("caFile")
		}()
		_, err = caFile.Write(caCert)
		if err != nil {
			return
		}

		// call readCACert()
		_, _ = readCACert("caFile")
	})

		return nil, nil, err
	}

	// If there is a failure of cleaning up CSR, the error is returned.
	return certChain, caCert, err
}

// Read CA certificate and check whether it is a valid certificate.
func readCACert(caCertPath string) ([]byte, error) {
	caCert, err := os.ReadFile(caCertPath)
	if err != nil {
		log.Errorf("failed to read CA cert, cert. path: %v, error: %v", caCertPath, err)