var err error
	priv, err = rsa.GenerateKey(crand.Reader, rsaBits)
	if err != nil {
		return nil, nil, fmt.Errorf("failed to generate private key: %w", err)
	}

	notBefore := time.Now()
	notAfter := notBefore.Add(validFor)

	serialNumberLimit := new(big.Int).Lsh(big.NewInt(1), 128)
	serialNumber, err := crand.Int(crand.Reader, serialNumberLimit)
	if err != nil {