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 by this way:

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 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?

---

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

https://dl.dropboxusercontent.com/u/15208254/keys/certificates.p12

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.

Answer 2

There are two kinds of CMSSignedData object generated using CMSSignedDataGenerator They are generated by the following way:

The one below generates a CMSSignedData object carrying a detached CMS signature

gen.generate(cmsdata);

The code below creates a CMSSignedData carrying a detached CMS signature, having the data encapsulated

gen.generate(cmsdata, true);

So verifying them requires 2 approaches

Approach No.1 to verify detached signature with encapsulated data

//sig is the Signature object
CMSSignedData signedData = new CMSSignedData(Base64.decode(sig.getBytes()));

Approach No.2 to verify detached signature without encapsulated data, just the detached signature

//Create a CMSProcessable object, specify any encoding, I have used mine 
CMSProcessable signedContent = new CMSProcessableByteArray(content.getBytes("ISO-8859-1"));
//Create a InputStream object
InputStream is = new ByteArrayInputStream(Base64.decode(sig.getBytes()));
//Pass them both to CMSSignedData constructor
CMSSignedData signedData = new CMSSignedData(signedContent, is);

Rest of the code for verification remains the same

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

    if (signer.verify(new JcaSimpleSignerInfoVerifierBuilder().setProvider("BC").build(cert))) {
        ret = true; 
    }
}

Answer 3

If we use signature.sign() as in the OP's answer, we won't be able to retrieve the original message, because its only the signature.

You should just input the original text bytes rather than the signed content. Basically, ignore this part:

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

and just input as:

CMSTypedData msg = new CMSProcessableByteArray(text.getBytes());

Answer 4

You can find answer at this link here You need to just add some headers to message or just add one blank line before message then sign the message then it will work fine.

Answer 5

Got it working for detached signature :D

package signature;

import java.security.Provider;
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.CMSProcessable;
import org.bouncycastle.cms.CMSProcessableByteArray;
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 {

    static final String DIGEST_SHA1 = "SHA1withRSA";
    static final String BC_PROVIDER = "BC";

    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==";
        String Sig_Bytes ="YduK22AlMLSXV3ajX5r/pX5OQ0xjj58uhGT9I9MvOrz912xNHo+9OiOKeMOD+Ys2/LUW3XaN6T+/"+
                "tuRM5bi4RK7yjaqaJCZWtr/O4I968BQGgt0cyNvK8u0Jagbr9MYk6G7nnejbRXYHyAOaunqD05lW"+
                "U/+g92i18dl0OMc50m4=";

        Provider provider = new BouncyCastleProvider();
        Security.addProvider(provider);
        CMSSignedData signedData = new CMSSignedData(Base64.decode(envelopedData.getBytes()));

        CMSProcessable cmsProcesableContent = new CMSProcessableByteArray(Base64.decode(Sig_Bytes.getBytes()));
        signedData = new CMSSignedData(cmsProcesableContent, Base64.decode(envelopedData.getBytes()));
        // Verify signature
        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");
            }
        }
    }



}