如何在java中創建CA證書

Question

我想在java中創建一個CA自簽名證書。 我已經使用充氣城堡創建了自簽名證書，但是如何將此證書的基本約束添加為CA證書。 謝謝

Answer 1

您可以使用以下代碼創建具有basicConstraints擴展名的自簽名證書：

public static Certificate selfSign(KeyPair keyPair, String subjectDN) throws OperatorCreationException, CertificateException, IOException
{
    Provider bcProvider = new BouncyCastleProvider();
    Security.addProvider(bcProvider);

    long now = System.currentTimeMillis();
    Date startDate = new Date(now);

    X500Name dnName = new X500Name(subjectDN);
    BigInteger certSerialNumber = new BigInteger(Long.toString(now)); // <-- Using the current timestamp as the certificate serial number

    Calendar calendar = Calendar.getInstance();
    calendar.setTime(startDate);
    calendar.add(Calendar.YEAR, 1); // <-- 1 Yr validity

    Date endDate = calendar.getTime();

    String signatureAlgorithm = "SHA256WithRSA"; // <-- Use appropriate signature algorithm based on your keyPair algorithm.

    ContentSigner contentSigner = new JcaContentSignerBuilder(signatureAlgorithm).build(keyPair.getPrivate());

    JcaX509v3CertificateBuilder certBuilder = new JcaX509v3CertificateBuilder(dnName, certSerialNumber, startDate, endDate, dnName, keyPair.getPublic());

    // Extensions --------------------------

    // Basic Constraint
    BasicConstraints basicConstraints = new BasicConstraints(true); // <-- true for CA, false for EndEntity

    certBuilder.addExtension(new ASN1ObjectIdentifier("2.5.29.19"), true, basicConstraints); // Basic Constraints is usually marked as critical.

    // -------------------------------------

    return new JcaX509CertificateConverter().setProvider(bcProvider).getCertificate(certBuilder.build(contentSigner));
}