Correct way to sign and verify signature using bouncycastle

Question

I am using bcmail-jdk16-1.46.jar and bcprov-jdk16-1.46.jar (Bouncycastle libraries) to sign a string and then verify the signature.

This is my code to sign a string:

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);

        BASE64Encoder encoder = new BASE64Encoder();

        String signedContent = encoder.encode((byte[]) sigData.getSignedContent().getContent());
        System.out.println("Signed content: " + signedContent + "\n");

        String envelopedData = encoder.encode(sigData.getEncoded());
        System.out.println("Enveloped data: " + envelopedData);
    }
}

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

package my.package;

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 {

        String envelopedData = "MIAGCSqGSIb3DQEHAqCAMIACAQExCzAJBgUrDgMCGgUAMIAGCSqGSIb3DQEHAQAAoIAwggLQMIIC" + 
                               "OQIEQ479uzANBgkqhkiG9w0BAQUFADCBrjEmMCQGCSqGSIb3DQEJARYXcm9zZXR0YW5ldEBtZW5k" + 
                               "ZWxzb24uZGUxCzAJBgNVBAYTAkRFMQ8wDQYDVQQIEwZCZXJsaW4xDzANBgNVBAcTBkJlcmxpbjEi" +
                               "MCAGA1UEChMZbWVuZGVsc29uLWUtY29tbWVyY2UgR21iSDEiMCAGA1UECxMZbWVuZGVsc29uLWUt" + 
                               "Y29tbWVyY2UgR21iSDENMAsGA1UEAxMEbWVuZDAeFw0wNTEyMDExMzQyMTlaFw0xOTA4MTAxMzQy" + 
                               "MTlaMIGuMSYwJAYJKoZIhvcNAQkBFhdyb3NldHRhbmV0QG1lbmRlbHNvbi5kZTELMAkGA1UEBhMC" + 
                               "REUxDzANBgNVBAgTBkJlcmxpbjEPMA0GA1UEBxMGQmVybGluMSIwIAYDVQQKExltZW5kZWxzb24t" + 
                               "ZS1jb21tZXJjZSBHbWJIMSIwIAYDVQQLExltZW5kZWxzb24tZS1jb21tZXJjZSBHbWJIMQ0wCwYD" + 
                               "VQQDEwRtZW5kMIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQC+X1g6JvbdwJI6mQMNT41GcycH" + 
                               "UbwCFWKJ4qHDaHffz3n4h+uQJJoQvc8yLTCfnl109GB0yL2Y5YQtTohOS9IwyyMWBhh77WJtCN8r" + 
                               "dOfD2DW17877te+NlpugRvg6eOH6np9Vn3RZODVxxTyyJ8pI8VMnn13YeyMMw7VVaEO5hQIDAQAB" + 
                               "MA0GCSqGSIb3DQEBBQUAA4GBALwOIc/rWMAANdEh/GgO/DSkVMwxM5UBr3TkYbLU/5jg0Lwj3Y++" + 
                               "KhumYSrxnYewSLqK+JXA4Os9NJ+b3eZRZnnYQ9eKeUZgdE/QP9XE04y8WL6ZHLB4sDnmsgVaTU+p" + 
                               "0lFyH0Te9NyPBG0J88109CXKdXCTSN5gq0S1CfYn0staAAAxggG9MIIBuQIBATCBtzCBrjEmMCQG" + 
                               "CSqGSIb3DQEJARYXcm9zZXR0YW5ldEBtZW5kZWxzb24uZGUxCzAJBgNVBAYTAkRFMQ8wDQYDVQQI" + 
                               "EwZCZXJsaW4xDzANBgNVBAcTBkJlcmxpbjEiMCAGA1UEChMZbWVuZGVsc29uLWUtY29tbWVyY2Ug" + 
                               "R21iSDEiMCAGA1UECxMZbWVuZGVsc29uLWUtY29tbWVyY2UgR21iSDENMAsGA1UEAxMEbWVuZAIE" + 
                               "Q479uzAJBgUrDgMCGgUAoF0wGAYJKoZIhvcNAQkDMQsGCSqGSIb3DQEHATAcBgkqhkiG9w0BCQUx" + 
                               "DxcNMTMwNTIxMDE1MDUzWjAjBgkqhkiG9w0BCQQxFgQU8mE6gw6iudxLUc9379lWK0lUSWcwDQYJ" + 
                               "KoZIhvcNAQEBBQAEgYB5mVhqJu1iX9nUqfqk7hTYJb1lR/hQiCaxruEuInkuVTglYuyzivZjAR54" + 
                               "zx7Cfm5lkcRyyxQ35ztqoq/V5JzBa+dYkisKcHGptJX3CbmmDIa1s65mEye4eLS4MTBvXCNCUTb9" + 
                               "STYSWvr4VPenN80mbpqSS6JpVxjM0gF3QTAhHwAAAAAAAA==";

        Security.addProvider(new BouncyCastleProvider());

        CMSSignedData cms = new CMSSignedData(Base64.decode(envelopedData.getBytes()));
        Store store = cms.getCertificates(); 
        SignerInformationStore signers = cms.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 cert = new JcaX509CertificateConverter().setProvider("BC").getCertificate(certHolder);
            if (signer.verify(new JcaSimpleSignerInfoVerifierBuilder().setProvider("BC").build(cert))) {
                System.out.println("verified");
            }
        }

    }

}

Everything works fine 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)

Can someone please give me a hint of what could be happening?

---

PS. If someone wants to test above code you will need the test certificate file that I am using to replicate this, just download it from here:

https://www.dropbox.com/s/zs4jo1a86v8qamw/certificates.p12?dl=0

Answer 1

The

gen.generate(msg, false)

means the signed data is not encapsulated in the signature. This is fine if you want to create a detached signature, but it does mean that when you go to verify the SignedData you have to use the CMSSignedData constructor that takes a copy of the data as well - in this case the code is using the single argument constructor which has to assume the signed data was encapsulated (so for this case will be empty), with the result that the attempt at verification is failing.