Correctly creating a new certificate with an intermediate certificate using bouny castle

问题

So my problem is as follows,

Basically I want to create a certificate chain using bouncy castle (jdk16 version 1.46). I am rather new to bouncy castle and java.security in general so if my approach might be completely wrong, but anyway this is what I did:

So far I am able to create a self signed certificate which I use as the root certificate. This is done using the following code:

//-----create CA certificate with key
KeyPair caPair = Signing.generateKeyPair("DSA", 1024, null, null);

This basically creates the keypair, the two null options are for a provider and a secure random, if needed.

Map<ASN1ObjectIdentifier, Entry<Boolean, DEREncodable>> caMap = new HashMap<ASN1ObjectIdentifier, Entry<Boolean, DEREncodable>>();
caMap.put(X509Extensions.BasicConstraints, new AbstractMap.SimpleEntry<Boolean, DEREncodable>(true, new BasicConstraints(true)));

//------this creates the self signed certificate        
X509Certificate caCert = X509CertificateGenerator.generateX509Certificate(serial, "CN=CA", "CN=CA", start, end, "SHA1withDSA", caPair.getPrivate(), caPair.getPublic(), null, caMap);

This will create the a certificate with the provided attributes.

serial = simply the current time in milliseconds
start = same as serial basically (may have 1 or 2 milliseconds difference)
end = start + 2 days

The map simply adds the basic contraint to set the certificate to be a CA. I use a map here since I want to be able to add additional X509Extensions if need be.

//-----save ca certificate in PEM format
X509CertificateGenerator.savePemX509Certificate(caCert, caPair.getPrivate(), caWriter);

This will store the certificate and private key in a pem file using the bouncy caste pem writer.

After that the file is generated and I can install the file as well (I use IE and then install it via the Internet Options as a trusted CA. The certificate is also shown to be valid).

After that I create the intermediate certificate, using the following code (note the above code is in the same scope so those variables are available as well)

KeyPair intermediatePair = Signing.generateKeyPair("DSA", 1024, null, null);    

Map<ASN1ObjectIdentifier, Entry<Boolean, DEREncodable>> intermediateMap = new HashMap<ASN1ObjectIdentifier, Entry<Boolean, DEREncodable>>();
intermediateMap.put(X509Extensions.AuthorityKeyIdentifier, new AbstractMap.SimpleEntry<Boolean, DEREncodable>(false, new AuthorityKeyIdentifierStructure(caCert)));
intermediateMap.put(X509Extensions.SubjectKeyIdentifier, new AbstractMap.SimpleEntry<Boolean, DEREncodable>(false, new SubjectKeyIdentifierStructure(intermediatePair.getPublic())));

X509Certificate intermediateCert = X509CertificateGenerator.generateX509Certificate(serial.add(BigInteger.valueOf(1l)), "CN=intermediate", caCert.getSubjectX500Principal().toString(), start, end, "SHA1withDSA", caPair.getPrivate(), intermediatePair.getPublic(), null, intermediateMap);   

//-----save intermediate certificate in PEM format
X509CertificateGenerator.savePemX509Certificate(intermediateCert, intermediatePair.getPrivate(), intermediateWriter);

The procedure is bascially the same, however I add additional X509Extensions:

X509Extensions.AuthorityKeyIdentifier = sets the CA certificate as the intermediates parent
X509Extensions.SubjectKeyIdentifier = uses the generates public key for the certificate

furthermore the CA is used as the issuer and the CA private key is used to create the intermediate certificate.

This also works and I can install the intermediate certificate (using IE again), it is also shown that the parent certififcate is the generated CA certificate and that the certificate is valid.

Now comes the tricky part where I am making a mistake I guess. I now create a new certificate using the intermediate certificate, using the following code.

KeyPair endPair = Signing.generateKeyPair("DSA", 1024, null, null);

Map<ASN1ObjectIdentifier, Entry<Boolean, DEREncodable>> endMap = new HashMap<ASN1ObjectIdentifier, Entry<Boolean, DEREncodable>>();
endMap.put(X509Extensions.AuthorityKeyIdentifier, new AbstractMap.SimpleEntry<Boolean, DEREncodable>(false, new AuthorityKeyIdentifierStructure(intermediateCert)));
endMap.put(X509Extensions.SubjectKeyIdentifier, new AbstractMap.SimpleEntry<Boolean, DEREncodable>(false, new SubjectKeyIdentifierStructure(endPair.getPublic())));

X509Certificate endCert = X509CertificateGenerator.generateX509Certificate(serial.add(BigInteger.valueOf(1l)), "CN=end", intermediateCert.getSubjectX500Principal().toString(), start, end, "SHA1withDSA", intermediatePair.getPrivate(), endPair.getPublic(), null, endMap);

X509CertificateGenerator.savePemX509Certificate(endCert, endPair.getPrivate(), endWriter);

Essentially it is the same as creating the intermediate certificate. However I now use the following X509Extension settings:

X509Extensions.AuthorityKeyIdentifier = sets the intermediate certificate as the certificates parent
X509Extensions.SubjectKeyIdentifier = uses the generates public key for the certificate

Also the intermediate certificate is used as the issuer and its private key is used to create the certificate.

I can also install the new certificate but when I examine if (again IE), it shows that the certificate is however invalid because "This CA is either not entitled to issue certificates or the certificate can not be used as an end-entity."

So I somehow need to enable the intermediate certificate to be able to create new certificates as well, by adding some KeyUsages/ExtendedKeyUsage I assume.

Does someone know how I enable the intermediate certificate to do what I need it to do or if I do something wrong in general ?

EDIT 1:

So okay I forgot to provide the code for the method which created the certificate and the one that saved it in PEM format (I renamed it to savePemX509Certificate since the old one was misguiding).

Code for the certificate generation:

public static X509Certificate generateX509Certificate(BigInteger serialnumber, String subject, String issuer, Date start , Date end, String signAlgorithm, PrivateKey privateKey, PublicKey publicKey, String provider, Map<ASN1ObjectIdentifier, Entry<Boolean, DEREncodable>> map) throws CertificateEncodingException, InvalidKeyException, IllegalStateException, NoSuchProviderException, NoSuchAlgorithmException, SignatureException
{
    if(serialnumber!=null && subject!=null && issuer!=null && start!=null && end!=null && signAlgorithm !=null && privateKey!=null && publicKey!=null)
    {
        //-----GENERATE THE X509 CERTIFICATE
        X509V3CertificateGenerator certGen = new X509V3CertificateGenerator();
        X509Principal dnSubject = new X509Principal(subject);
        X509Principal dnIssuer = new X509Principal(issuer);

        certGen.setSerialNumber(serialnumber);
        certGen.setSubjectDN(dnSubject);
        certGen.setIssuerDN(dnIssuer);
        certGen.setNotBefore(start);
        certGen.setNotAfter(end);
        certGen.setPublicKey(publicKey);
        certGen.setSignatureAlgorithm(signAlgorithm);

        //-----insert extension if needed
        if(map!=null)
            for(ASN1ObjectIdentifier extension : map.keySet())
                certGen.addExtension(extension, map.get(extension).getKey(), map.get(extension).getValue());

        return certGen.generate(privateKey, provider);  
    }
    return null;
}

Code for the saveing of the certificate and key:

public static boolean savePemX509Certificate(X509Certificate cert, PrivateKey key, Writer writer) throws NoSuchAlgorithmException, NoSuchProviderException, CertificateEncodingException, SignatureException, InvalidKeyException, IOException 
{       
    if(cert!=null && key!=null && writer!=null)
    {               
        PEMWriter pemWriter = new PEMWriter(writer);
        pemWriter.writeObject(cert);
        pemWriter.flush();

        if(key!=null)
        {
            pemWriter.writeObject(key);
            pemWriter.flush();
        }
        pemWriter.close();
        return true;
        }
    return false;
}

As you can see I basically put the certificate and the key in the file, thats all. The result is the following and seems good to me.

So after gtrig provided me with the correct way to create the certificate, I ended up using this method to create either a normal or self signed (if the private key is from the same keyPair as the public key that is) certificate

public static X509Certificate createX509V3Certificate(X500Principal name, BigInteger serial, Date start, Date end, PublicKey pubKey, String algorithm, PrivateKey privateKey, Map<ASN1ObjectIdentifier, Entry<Boolean, ASN1Object>> map, X509Certificate parentCert) throws IOException, OperatorCreationException, CertificateException
{
    if(serial!=null && start!=null && end!=null && name!=null && pubKey!=null && algorithm!=null && privateKey!=null)
    {
        ContentSigner signer = new JcaContentSignerBuilder(algorithm).build(privateKey);
        X509v3CertificateBuilder certBldr = null;
        if(parentCert==null)
            certBldr = new JcaX509v3CertificateBuilder(name, serial, start, end, name, pubKey);
        else
            certBldr = new JcaX509v3CertificateBuilder(parentCert, serial, start, end, name, pubKey);

        if(map!=null)
            for(ASN1ObjectIdentifier extension : map.keySet())
                certBldr.addExtension(extension, map.get(extension).getKey(), map.get(extension).getValue());

        return new JcaX509CertificateConverter().setProvider("BC").getCertificate(certBldr.build(signer));  
    }
    return null;
}

回答1:

Something looks wrong with the way you're creating the PEM files. You're using a method called, generateSelfSignedPemX509Certificate, but you don't really want a self-signed certificate, you want an end certificate signed by the intermediate private key, and you want an intermediate certificate signed by the CA private key.

Also, you need basic constraints and key usage extensions on your certificates.

For creating certificates signed by other entities (non-self-signed), I use these methods from Bouncy Castle to create an "end" certificate.

  ASN1Sequence seq= 
     (ASN1Sequence) new ASN1InputStream(parentPubKey.getEncoded()).readObject();

  SubjectPublicKeyInfo parentPubKeyInfo = new SubjectPublicKeyInfo(seq);

  ContentSigner signer = new JcaContentSignerBuilder(algorithm).build(parentPrivKey);

  X509v3CertificateBuilder certBldr = 
     new JcaX509v3CertificateBuilder(
        parentCert, 
        serialNum,
        startDate, 
        endDate, 
        distName, 
        pubKey)
     .addExtension(
           new ASN1ObjectIdentifier("2.5.29.35"),
           false,
           new AuthorityKeyIdentifier(parentPubKeyInfo))
     .addExtension(
        new ASN1ObjectIdentifier("2.5.29.19"), 
        false,
        new BasicConstraints(false)) // true if it is allowed to sign other certs
     .addExtension(
        new ASN1ObjectIdentifier("2.5.29.15"),
        true,
        new X509KeyUsage(
           X509KeyUsage.digitalSignature |
           X509KeyUsage.nonRepudiation   |
           X509KeyUsage.keyEncipherment  |
           X509KeyUsage.dataEncipherment));

  // Build/sign the certificate.
  X509CertificateHolder certHolder = certBldr.build(signer);

  X509Certificate cert = new JcaX509CertificateConverter().setProvider(BC)
     .getCertificate(certHolder);

For a CA or intermediate certificate, you'll need to add a SubjectKeyIdentifier extension. Also, BasicConstraints should be true, and KeyUsage should be:

        new X509KeyUsage(
           X509KeyUsage.keyCertSign|
           X509KeyUsage.cRLSign));

来源：https://stackoverflow.com/questions/18633273/correctly-creating-a-new-certificate-with-an-intermediate-certificate-using-boun

标签

java

security

x509certificate

bouncycastle

pem