これを行う方法も検索しましたが、例が見つからなかったため、代わりに keytool ソースを調べました。(ここで見つけることができます: http://www.docjar.com/html/api/sun/security/tools/KeyTool.java.html )
署名を行う方法の例を次に示します。
private static final String SIGNATURE_ALGORITHM = "SHA1WITHRSA";
private static final long VALIDITY_DAYS = 14L;
public static byte[] sign(PKCS10 csr, X509CertImpl signerCert, PrivateKey signerPrivKey) throws CertificateException, IOException, InvalidKeyException, SignatureException {
/*
* The code below is partly taken from the KeyTool class in OpenJDK7.
*/
X509CertInfo signerCertInfo = (X509CertInfo) signerCert.get(X509CertImpl.NAME + "." + X509CertImpl.INFO);
X500Name issuer = (X500Name) signerCertInfo.get(X509CertInfo.SUBJECT + "." + CertificateSubjectName.DN_NAME);
/*
* Set the certificate's validity:
* From now and for VALIDITY_DAYS days
*/
Date firstDate = new Date();
Date lastDate = new Date();
lastDate.setTime(firstDate.getTime() + VALIDITY_DAYS * 1000L * 24L * 60L * 60L);
CertificateValidity interval = new CertificateValidity(firstDate, lastDate);
/*
* Initialize the signature object
*/
Signature signature;
try {
signature = Signature.getInstance(SIGNATURE_ALGORITHM);
} catch (NoSuchAlgorithmException e) {
throw new RuntimeException(e);
}
signature.initSign(signerPrivKey);
/*
* Add the certificate information to a container object
*/
X509CertInfo certInfo = new X509CertInfo();
certInfo.set(X509CertInfo.VALIDITY, interval);
certInfo.set(X509CertInfo.SERIAL_NUMBER, new CertificateSerialNumber(new Random().nextInt() & 0x7fffffff));
certInfo.set(X509CertInfo.VERSION, new CertificateVersion(CertificateVersion.V3));
try {
certInfo.set(X509CertInfo.ALGORITHM_ID, new CertificateAlgorithmId(AlgorithmId.get(SIGNATURE_ALGORITHM)));
} catch (NoSuchAlgorithmException e) {
throw new RuntimeException(e);
}
certInfo.set(X509CertInfo.ISSUER, new CertificateIssuerName(issuer));
certInfo.set(X509CertInfo.KEY, new CertificateX509Key(csr.getSubjectPublicKeyInfo()));
certInfo.set(X509CertInfo.SUBJECT, new CertificateSubjectName(csr.getSubjectName()));
/*
* Add x509v3 extensions to the container
*/
CertificateExtensions extensions = new CertificateExtensions();
// Example extension.
// See KeyTool source for more.
boolean[] keyUsagePolicies = new boolean[9];
keyUsagePolicies[0] = true; // Digital Signature
keyUsagePolicies[2] = true; // Key encipherment
KeyUsageExtension kue = new KeyUsageExtension(keyUsagePolicies);
byte[] keyUsageValue = new DerValue(DerValue.tag_OctetString, kue.getExtensionValue()).toByteArray();
extensions.set(KeyUsageExtension.NAME, new Extension(
kue.getExtensionId(),
true, // Critical
keyUsageValue));
/*
* Create the certificate and sign it
*/
X509CertImpl cert = new X509CertImpl(certInfo);
try {
cert.sign(signerPrivKey, SIGNATURE_ALGORITHM);
} catch (NoSuchAlgorithmException e) {
throw new RuntimeException(e);
} catch (NoSuchProviderException e) {
throw new RuntimeException(e);
}
/*
* Return the signed certificate as PEM-encoded bytes
*/
ByteOutputStream bos = new ByteOutputStream();
PrintStream out = new PrintStream(bos);
BASE64Encoder encoder = new BASE64Encoder();
out.println(X509Factory.BEGIN_CERT);
encoder.encodeBuffer(cert.getEncoded(), out);
out.println(X509Factory.END_CERT);
out.flush();
return bos.getBytes();
}