Signing Apple's passbook passes

Question

I am trying to sign a manifest.json file in C# for Apple Passbook passes. I've followed Apple's guide for signing passes and looked at posts here and here. When I execute the code, a CryptographicException occurs at the line signedCms.ComputeSignature(cmsSigner); saying that

Key does not exist

This is the code I currently have:

    private void button2_Click(object sender, EventArgs e)
    {

        String manifest = System.IO.File.ReadAllText(@"C:\Users\Administrator\Downloads\Testpass\Testpass\manifest.json");
        byte[] msgBytes = Encoding.Unicode.GetBytes(manifest);
        byte[] sign = SignMsg(msgBytes, findCertificate(true));

        //byte[] sign = signit(manifest);
        File.WriteAllBytes(@"C:\Users\Administrator\Downloads\Testpass\Testpass", sign);


    }

    private byte[] SignMsg(Byte[] msg, X509Certificate2 signerCert)
    {
        ContentInfo contentInfo = new ContentInfo(msg);
        SignedCms signedCms = new SignedCms(contentInfo, true);

        X509Certificate2 developerCertificate = new X509Certificate2(@"C:\Users\Administrator\Downloads\pass.cer");
        X509Certificate2 appleWWDRCA = new X509Certificate2(@"C:\Users\Administrator\Downloads\AppleWWDRCA.cer");
        CmsSigner cmsSigner = new CmsSigner(SubjectIdentifierType.IssuerAndSerialNumber, developerCertificate);
        cmsSigner.IncludeOption = X509IncludeOption.EndCertOnly;
        cmsSigner.Certificates.Add(appleWWDRCA);
        cmsSigner.SignedAttributes.Add(new Pkcs9SigningTime(DateTime.Now));

        //  Sign the CMS/PKCS #7 message.
        signedCms.ComputeSignature(cmsSigner);

        //  Encode the CMS/PKCS #7 message.
        return signedCms.Encode();
    }

Is it neccessary to get the certificates from the Windows Certificate Store, or is getting it from the file system OK? Any help on how to fix the problem is appreciated!

PS: I have also looked at DotNet-Passbook, but first of all it created some problems for me, and second, I really only need the signing of the manifest file, not everything else that the library provide.

Answer 1

I'm the creator of dotnet-passbook.

This error looks like your certificate doesn't include the private key component.

When you open the certificate in Windows, it will indicate whether or not the private key is included.