Search code examples
javabouncycastlesignatureca

Bouncy Castle: Signed Certificate with an existing CA

I'm trying to create a certificate (A) which is signed for other certificate (B) stored in a p12 keystore. This stored certificate (B) was added to the trusted certificate store of my local machine.

Certificate A is used to sign a pdf document using bouncy castle 1.52 library, but the digital signature that I obtain in the signed document is invalid.

I'm going to explain the steps done just if somebody can help me.

First, I create a CSR from the p12 keystore(B):

    private static PKCS10CertificationRequest generateCSR() {
    PKCS10CertificationRequest csr = null;
    try {
        initCACert();
        PKCS10CertificationRequestBuilder p10Builder = new JcaPKCS10CertificationRequestBuilder(
                new X500Principal("CN=Requested Test Certificate"), CAcert.getPublicKey());
        JcaContentSignerBuilder csBuilder = new JcaContentSignerBuilder("SHA256withRSA");
        ContentSigner signer = csBuilder.build(CApk);
        csr = p10Builder.build(signer);
    } catch (Exception e) {
        log.error(e);
    }
    return csr;
}

Then, a certificate was generated (A) with this CSR.

    private static Certificate signCSR() throws Exception { 
    PKCS10CertificationRequest csr = generateCSR();

    AlgorithmIdentifier sigAlgId = new DefaultSignatureAlgorithmIdentifierFinder().find("SHA256withRSA");
    AlgorithmIdentifier digAlgId = new DefaultDigestAlgorithmIdentifierFinder().find(sigAlgId);

    X500Name issuer = X500Name.getInstance(CAcert.getSubjectX500Principal().getEncoded());

    BigInteger serial = new BigInteger(32, new SecureRandom());
    Calendar c = Calendar.getInstance();
    c.add(Calendar.SECOND, -1);
    Date from = c.getTime();
    c.add(Calendar.YEAR, 5);
    Date to = c.getTime();

    X509v1CertificateBuilder certBuilder = new X509v1CertificateBuilder(issuer, serial, from, to, csr.getSubject(),
            csr.getSubjectPublicKeyInfo());

    ContentSigner signer = new BcRSAContentSignerBuilder(sigAlgId, digAlgId)
            .build(PrivateKeyFactory.createKey(CApk.getEncoded()));
    X509CertificateHolder holder = certBuilder.build(signer);

    CertificateFactory certFactory = CertificateFactory.getInstance("X.509");
    InputStream in = new ByteArrayInputStream(holder.getEncoded());
    Certificate cert = certFactory.generateCertificate(in);

    return cert;
}

Finally, I use this generated certificate (A) to sign my pdf.

        Certificate cert = signCSR();

        SignerInfoGeneratorBuilder signerInfoBuilder = new SignerInfoGeneratorBuilder(
                    new JcaDigestCalculatorProviderBuilder().setProvider("BC").build()
                    );
        signerInfoBuilder.setSignedAttributeGenerator( signedAttributeGenerator );

        JcaContentSignerBuilder contentSignerBuilder = new JcaContentSignerBuilder( "SHA1WITHRSA" );
        contentSignerBuilder.setProvider("BC");


        X509CertificateHolder certificateHolder = new X509CertificateHolder( cert.getEncoded( ) );

        generator.addSignerInfoGenerator(
                signerInfoBuilder.build( contentSignerBuilder.build( CApk ),
                        certificateHolder ) 
                );

        ArrayList<X509CertificateHolder> signingChainHolder = new ArrayList<X509CertificateHolder>( );
        certificateHolder = new X509CertificateHolder( cert.getEncoded() );
        certificateHolder = new X509CertificateHolder( CAcert.getEncoded() );

        signingChainHolder.add( certificateHolder );

        Store certs = new JcaCertStore( signingChainHolder );
        generator.addCertificates( certs );

        CMSTypedData content = new CMSProcessableByteArray(datos);

        CMSSignedData signedData = generator.generate( content, true );
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        new DEROutputStream(baos).writeObject(signedData.toASN1Structure());
        result = baos.toByteArray();

All the process is executed apparently right, but when I open the pdf the signature is invalid:

enter image description here

enter image description here

enter image description here

EDIT: I have made an export of the generated certificate. This is the result obtained.

enter image description here

I will appreciate any comment or information that can help me to fix this.

Thanks in advance.

Solution

  • I have identified the problem: I was building the certificate chain in the opposite order that should be.

    I had this order:

     certificateHolder = new X509CertificateHolder( cert.getEncoded() );
 certificateHolder = new X509CertificateHolder( CAcert.getEncoded() );

    And the right order is this:

    certificateHolder = new X509CertificateHolder( CAcert.getEncoded() );
certificateHolder = new X509CertificateHolder( cert.getEncoded() );

    I hope somebody can find this information useful!