Creating a Certificate from a Certification Request : KeyPairGenerator « Security


import java.io.OutputStreamWriter;

import java.math.BigInteger;

import java.security.InvalidKeyException;

import java.security.KeyPair;

import java.security.KeyPairGenerator;

import java.security.NoSuchProviderException;

import java.security.SecureRandom;

import java.security.Security;

import java.security.SignatureException;

import java.security.cert.X509Certificate;

import java.util.Date;

import java.util.Enumeration;



import javax.security.auth.x500.X500Principal;



import org.bouncycastle.asn1.ASN1Set;

import org.bouncycastle.asn1.DERObjectIdentifier;

import org.bouncycastle.asn1.pkcs.Attribute;

import org.bouncycastle.asn1.pkcs.PKCSObjectIdentifiers;

import org.bouncycastle.asn1.x509.BasicConstraints;

import org.bouncycastle.asn1.x509.ExtendedKeyUsage;

import org.bouncycastle.asn1.x509.KeyPurposeId;

import org.bouncycastle.asn1.x509.KeyUsage;

import org.bouncycastle.asn1.x509.X509Extension;

import org.bouncycastle.asn1.x509.X509Extensions;

import org.bouncycastle.jce.PKCS10CertificationRequest;

import org.bouncycastle.openssl.PEMWriter;

import org.bouncycastle.x509.X509V1CertificateGenerator;

import org.bouncycastle.x509.X509V3CertificateGenerator;

import org.bouncycastle.x509.extension.AuthorityKeyIdentifierStructure;

import org.bouncycastle.x509.extension.SubjectKeyIdentifierStructure;



public class MainClass {

  public static KeyPair generateRSAKeyPair() throws Exception {

    KeyPairGenerator kpGen = KeyPairGenerator.getInstance("RSA", "BC");

    kpGen.initialize(1024, new SecureRandom());

    return kpGen.generateKeyPair();

  }



  public static PKCS10CertificationRequest generateRequest(KeyPair pair) throws Exception {

    return new PKCS10CertificationRequest("SHA256withRSA", new X500Principal(

        "CN=Requested Test Certificate"), pair.getPublic(), null, pair.getPrivate());

  }



  public static X509Certificate generateV1Certificate(KeyPair pair) throws InvalidKeyException,

      NoSuchProviderException, SignatureException {

    Security.addProvider(new org.bouncycastle.jce.provider.BouncyCastleProvider());



    X509V1CertificateGenerator certGen = new X509V1CertificateGenerator();



    certGen.setSerialNumber(BigInteger.valueOf(System.currentTimeMillis()));

    certGen.setIssuerDN(new X500Principal("CN=Test Certificate"));

    certGen.setNotBefore(new Date(System.currentTimeMillis() - 10000));

    certGen.setNotAfter(new Date(System.currentTimeMillis() + 10000));

    certGen.setSubjectDN(new X500Principal("CN=Test Certificate"));

    certGen.setPublicKey(pair.getPublic());

    certGen.setSignatureAlgorithm("SHA256WithRSAEncryption");



    return certGen.generateX509Certificate(pair.getPrivate(), "BC");

  }



  public static X509Certificate[] buildChain() throws Exception {

    KeyPair pair = generateRSAKeyPair();

    PKCS10CertificationRequest request = generateRequest(pair);



    KeyPair rootPair = generateRSAKeyPair();

    X509Certificate rootCert = generateV1Certificate(rootPair);



    X509V3CertificateGenerator certGen = new X509V3CertificateGenerator();



    certGen.setSerialNumber(BigInteger.valueOf(System.currentTimeMillis()));

    certGen.setIssuerDN(rootCert.getSubjectX500Principal());

    certGen.setNotBefore(new Date(System.currentTimeMillis()));

    certGen.setNotAfter(new Date(System.currentTimeMillis() + 10000));

    certGen.setSubjectDN(request.getCertificationRequestInfo().getSubject());

    certGen.setPublicKey(request.getPublicKey("BC"));

    certGen.setSignatureAlgorithm("SHA256WithRSAEncryption");



    certGen.addExtension(X509Extensions.AuthorityKeyIdentifier, false,

        new AuthorityKeyIdentifierStructure(rootCert));



    certGen.addExtension(X509Extensions.SubjectKeyIdentifier,



    false, new SubjectKeyIdentifierStructure(request.getPublicKey("BC")));



    certGen.addExtension(X509Extensions.BasicConstraints, true, new BasicConstraints(false));



    certGen.addExtension(X509Extensions.KeyUsage, true, new KeyUsage(KeyUsage.digitalSignature

        | KeyUsage.keyEncipherment));



    certGen.addExtension(X509Extensions.ExtendedKeyUsage, true, new ExtendedKeyUsage(

        KeyPurposeId.id_kp_serverAuth));



    ASN1Set attributes = request.getCertificationRequestInfo().getAttributes();



    for (int i = 0; i != attributes.size(); i++) {

      Attribute attr = Attribute.getInstance(attributes.getObjectAt(i));



      if (attr.getAttrType().equals(PKCSObjectIdentifiers.pkcs_9_at_extensionRequest)) {

        X509Extensions extensions = X509Extensions.getInstance(attr.getAttrValues().getObjectAt(0));



        Enumeration e = extensions.oids();

        while (e.hasMoreElements()) {

          DERObjectIdentifier oid = (DERObjectIdentifier) e.nextElement();

          X509Extension ext = extensions.getExtension(oid);



          certGen.addExtension(oid, ext.isCritical(), ext.getValue().getOctets());

        }

      }

    }

    X509Certificate issuedCert = certGen.generateX509Certificate(rootPair.getPrivate());



    return new X509Certificate[] { issuedCert, rootCert };

  }



  public static void main(String[] args) throws Exception {

    Security.addProvider(new org.bouncycastle.jce.provider.BouncyCastleProvider());

    X509Certificate[] chain = buildChain();



    PEMWriter pemWrt = new PEMWriter(new OutputStreamWriter(System.out));



    pemWrt.writeObject(chain[0]);

    pemWrt.writeObject(chain[1]);



    pemWrt.close();

  }

}
Creating a Certificate from a Certification Request : KeyPairGenerator « Security « Java Tutorial
