C# Generate client Certificate from Root Certificate using CertEnroll

I would like to write a function that generates client certificates signed by my root certificate using CertEnroll.dll, I do have Root PFX file at specific location and by reading that creating CSignerCertificate object. Here is my code for the same.

I am getting error for below code 'CertEnroll::CSignerCertificate::Initialize: Cannot find object or property. 0x80092004 (-2146885628 CRYPT_E_NOT_FOUND)'

 public static X509Certificate2 CertCreateNew(string subjectName)
        // create DN for subject and issuer
        var dn = new CX500DistinguishedName();
        dn.Encode("CN=" + subjectName, X500NameFlags.XCN_CERT_NAME_STR_NONE);

        // create a new private key for the certificate
        CX509PrivateKey privateKey = new CX509PrivateKey();
        privateKey.ProviderName = "Microsoft Base Cryptographic Provider v1.0";
        privateKey.MachineContext = false;
        privateKey.Length = 2048;
        privateKey.KeySpec = X509KeySpec.XCN_AT_SIGNATURE; // use is not limited
        privateKey.ExportPolicy = X509PrivateKeyExportFlags.XCN_NCRYPT_ALLOW_PLAINTEXT_EXPORT_FLAG;

        var hashobj = new CObjectId();
            AlgorithmFlags.AlgorithmFlagsNone, "SHA256");

        // add extended key usage if you want - look at MSDN for a list of possible OIDs
        var oid = new CObjectId();
        oid.InitializeFromValue(""); // SSL server
        var oidlist = new CObjectIds();
        var eku = new CX509ExtensionEnhancedKeyUsage();

        // Create the self signing request
        var cert = new CX509CertificateRequestCertificate();
        X509Certificate2 signercertificate = CertOpen("My Personal CA");
        X509Certificate2 signer = new X509Certificate2(System.IO.File.ReadAllBytes(@"d:\\PKICertificates\\Root Certificates\\MyPersonalCA.pfx"), "password");
        if (signer == null)
            throw new CryptographicException("Signer not found");

        ISignerCertificate signerCertificate = new CSignerCertificate();

        signerCertificate.Initialize(false, X509PrivateKeyVerify.VerifySilent, EncodingType.XCN_CRYPT_STRING_BASE64, Convert.ToBase64String(signer.RawData)); 

        cert.Issuer.Encode(signer.Subject, X500NameFlags.XCN_CERT_NAME_STR_NONE);

        cert.InitializeFromPrivateKey(X509CertificateEnrollmentContext.ContextUser, privateKey, "");           
        cert.SignerCertificate = (CSignerCertificate)signerCertificate;
        cert.Subject = dn;            
        cert.NotBefore = DateTime.Now;
        // this cert expires immediately. Change to whatever makes sense for you
        cert.NotAfter = DateTime.Now.AddYears(10);
        cert.X509Extensions.Add((CX509Extension)eku); // add the EKU
        cert.HashAlgorithm = hashobj; // Specify the hashing algorithm
        cert.Encode(); // encode the certificate

        // Do the final enrollment process
        var enroll = new CX509Enrollment();
        enroll.InitializeFromRequest(cert); // load the certificate
        enroll.CertificateFriendlyName = subjectName; // Optional: add a friendly name

        string csr = enroll.CreateRequest(); // Output the request in base64
                                             // and install it back as the response
            csr, EncodingType.XCN_CRYPT_STRING_BASE64, ""); // no password
                                                            // output a base64 encoded PKCS#12 so we can import it back to the .Net security classes
        var base64encoded = enroll.CreatePFX("", // no password, this is for internal consumption

        // instantiate the target class with the PKCS#12 data (and the empty password)
        return new System.Security.Cryptography.X509Certificates.X509Certificate2(
            System.Convert.FromBase64String(base64encoded), "",
            // mark the private key as exportable (this is usually what you want to do)

Does anyone know how I can generate a client CX509CertificateRequest signed by my root?

Any help or advice would be greatly appreciated.

Read more here: https://stackoverflow.com/questions/61595035/c-sharp-generate-client-certificate-from-root-certificate-using-certenroll

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This content was originally published by Manoj Ahuja at Recent Questions - Stack Overflow, and is syndicated here via their RSS feed. You can read the original post over there.

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