How to sign signature data using bouncy castle?

Question

**This is my code to sign a String.</br>**

package my.package;

import java.io.FileInputStream;
import java.security.Key;
import java.security.KeyStore;
import java.security.PrivateKey;
import java.security.Security;
import java.security.Signature;
import java.security.cert.X509Certificate;
import java.util.ArrayList;
import java.util.List;
import org.bouncycastle.cert.jcajce.JcaCertStore;
import org.bouncycastle.cms.CMSProcessableByteArray;
import org.bouncycastle.cms.CMSSignedData;
import org.bouncycastle.cms.CMSSignedDataGenerator;
import org.bouncycastle.cms.CMSTypedData;
import org.bouncycastle.cms.jcajce.JcaSignerInfoGeneratorBuilder;
import org.bouncycastle.jce.provider.BouncyCastleProvider;
import org.bouncycastle.operator.ContentSigner;
import org.bouncycastle.operator.jcajce.JcaContentSignerBuilder;
import org.bouncycastle.operator.jcajce.JcaDigestCalculatorProviderBuilder;
import org.bouncycastle.util.Store;
import sun.misc.BASE64Encoder;

public class SignMessage {
    static final String KEYSTORE_FILE = "keys/certificates.p12";
    static final String KEYSTORE_INSTANCE = "PKCS12";
    static final String KEYSTORE_PWD = "test";
    static final String KEYSTORE_ALIAS = "Key1";

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

        String text = "This is a message";

        Security.addProvider(new BouncyCastleProvider());

        KeyStore ks = KeyStore.getInstance(KEYSTORE_INSTANCE);
        ks.load(new FileInputStream(KEYSTORE_FILE), KEYSTORE_PWD.toCharArray());
        Key key = ks.getKey(KEYSTORE_ALIAS, KEYSTORE_PWD.toCharArray());

        //Sign
        PrivateKey privKey = (PrivateKey) key;
        Signature signature = Signature.getInstance("SHA1WithRSA", "BC");
        signature.initSign(privKey);
        signature.update(text.getBytes());

        //Build CMS
        X509Certificate cert = (X509Certificate) ks.getCertificate(KEYSTORE_ALIAS);
        List certList = new ArrayList();
        CMSTypedData msg = new CMSProcessableByteArray(signature.sign());
        certList.add(cert);
        Store certs = new JcaCertStore(certList);
        CMSSignedDataGenerator gen = new CMSSignedDataGenerator();
        ContentSigner sha1Signer = new JcaContentSignerBuilder("SHA1withRSA").setProvider("BC").build(privKey);
        gen.addSignerInfoGenerator(new JcaSignerInfoGeneratorBuilder(new JcaDigestCalculatorProviderBuilder().setProvider("BC").build()).build(sha1Signer, cert));
        gen.addCertificates(certs);
        CMSSignedData sigData = gen.generate(msg, false);

        FileOutputStream sigfos = new FileOutputStream("D:\\SBI-DATA\\file\\signature_1.txt");
            sigfos.write(Base64.encodeBase64(sp.getEncoded()));

            sigfos.close();
    }
}

---

Now, the EnvelopedData output will be used in the process to verify the signature by this way:

import java.security.Security;
import java.security.cert.X509Certificate;
import java.util.Collection;
import java.util.Iterator;
import org.bouncycastle.cert.X509CertificateHolder;
import org.bouncycastle.cert.jcajce.JcaX509CertificateConverter;
import org.bouncycastle.cms.CMSSignedData;
import org.bouncycastle.cms.SignerInformation;
import org.bouncycastle.cms.SignerInformationStore;
import org.bouncycastle.cms.jcajce.JcaSimpleSignerInfoVerifierBuilder;
import org.bouncycastle.jce.provider.BouncyCastleProvider;
import org.bouncycastle.util.Store;
import org.bouncycastle.util.encoders.Base64;

public class VerifySignature {
    public static void main(String[] args) throws Exception {
        File p7s = new File("D:\\SBI-DATA\\file\\signature_2.txt") ;
        int size = ((int) p7s.length());
        byte[] sig = new byte[size]; 
        File f = new File("D:\\SBI-DATA\\file\\plain.txt") ;
        int sizecontent = ((int) f.length());
        byte[] Data_Bytes = new byte[sizecontent];  
        Security.addProvider(new BouncyCastleProvider());    
        CMSSignedData signedData = new CMSSignedData(new CMSProcessableByteArray(Data_Bytes), sig);     
            Store store = signedData.getCertificates(); 
            SignerInformationStore signers = signedData.getSignerInfos(); 
            Collection c = signers.getSigners(); 
            Iterator it = c.iterator();
            while (it.hasNext()) { 
                SignerInformation signer = (SignerInformation) it.next(); 
                Collection certCollection = store.getMatches(signer.getSID()); 
                Iterator certIt = certCollection.iterator();
                X509CertificateHolder certHolder = (X509CertificateHolder) certIt.next();
                X509Certificate certFromSignedData = new JcaX509CertificateConverter().setProvider(BC_PROVIDER).getCertificate(certHolder);
                if (signer.verify(new JcaSimpleSignerInfoVerifierBuilder().setProvider(BC_PROVIDER).build(certFromSignedData))) {
                    System.out.println("Signature verified");
                } else {
                    System.out.println("Signature verification failed");
                }
            }
    }    
}  

---

Everything works good until signer.verify(..) due to the following Exception:

Exception in thread "main" org.bouncycastle.cms.CMSSignerDigestMismatchException: message-digest attribute value does not match calculated value
    at org.bouncycastle.cms.SignerInformation.doVerify(Unknown Source)
    at org.bouncycastle.cms.SignerInformation.verify(Unknown Source)
    at my.package.VerifySignature.main(VerifySignature.java:64)

And I really don't know what I am doing wrong. Can someone please give me a hint of what is happening?

Answer 1

I think you are signing it twice, once directly using Signature and the other one using ContentSigner. You need only to sign the data, not the signature.

So the solution should be to replace signature.sign() with text.getBytes(), or text.getBytes(StandardCharsets.UTF_8) if you want to explicitly define a character set for text instead of using some system default.