How to create a certificate request with CertEnroll and .NET (C#)

Hi all,

The following C# sample shows how to use CertEnroll COM component to create a certificate request, send the request to the CA, get the response from the CA, and install the new certificate in the machine:

(Note that this sample is a WinForms app with 3 buttons -createRequestButton, sendRequestButton, acceptPKCS7Button- and 2 textboxes -requestText & responseText-)

 using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;

//  Add the CertEnroll namespace
using CERTENROLLLib;
using CERTCLIENTLib;

namespace CATest
{
    public partial class Form1 : Form
    {
        private const int CC_DEFAULTCONFIG = 0;
        private const int CC_UIPICKCONFIG = 0x1;
        private const int CR_IN_BASE64 = 0x1;
        private const int CR_IN_FORMATANY = 0;
        private const int CR_IN_PKCS10 = 0x100;
        private const int CR_DISP_ISSUED = 0x3;
        private const int CR_DISP_UNDER_SUBMISSION = 0x5;
        private const int CR_OUT_BASE64 = 0x1;
        private const int CR_OUT_CHAIN = 0x100;

        public Form1()
        {
            InitializeComponent();
        }

        // Create request
        private void createRequestButton_Click(object sender, EventArgs e)
        {
            //  Create all the objects that will be required
            CX509CertificateRequestPkcs10 objPkcs10 = new CX509CertificateRequestPkcs10Class();
            CX509PrivateKey objPrivateKey = new CX509PrivateKeyClass();
            CCspInformation objCSP = new CCspInformationClass();
            CCspInformations objCSPs = new CCspInformationsClass();
            CX500DistinguishedName objDN = new CX500DistinguishedNameClass();
            CX509Enrollment objEnroll = new CX509EnrollmentClass();
            CObjectIds objObjectIds = new CObjectIdsClass();
            CObjectId objObjectId = new CObjectIdClass();
            CX509ExtensionKeyUsage objExtensionKeyUsage = new CX509ExtensionKeyUsageClass(); 
            CX509ExtensionEnhancedKeyUsage objX509ExtensionEnhancedKeyUsage = new CX509ExtensionEnhancedKeyUsageClass();
            string strRequest;

            try
            {
                requestText.Text = "";

                //  Initialize the csp object using the desired Cryptograhic Service Provider (CSP)
                objCSP.InitializeFromName(
                    "Microsoft Enhanced Cryptographic Provider v1.0"
                );

                //  Add this CSP object to the CSP collection object
                objCSPs.Add(
                    objCSP
                );

                //  Provide key container name, key length and key spec to the private key object
                //objPrivateKey.ContainerName = "AlejaCMa";
                objPrivateKey.Length = 1024;
                objPrivateKey.KeySpec = X509KeySpec.XCN_AT_SIGNATURE;
                objPrivateKey.KeyUsage = X509PrivateKeyUsageFlags.XCN_NCRYPT_ALLOW_ALL_USAGES; 
                objPrivateKey.MachineContext = false;

                //  Provide the CSP collection object (in this case containing only 1 CSP object)
                //  to the private key object
                objPrivateKey.CspInformations = objCSPs;

                //  Create the actual key pair
                objPrivateKey.Create();

                //  Initialize the PKCS#10 certificate request object based on the private key.
                //  Using the context, indicate that this is a user certificate request and don't
                //  provide a template name
                objPkcs10.InitializeFromPrivateKey(
                    X509CertificateEnrollmentContext.ContextUser, 
                    objPrivateKey, 
                    ""
                );

                // Key Usage Extension 
                objExtensionKeyUsage.InitializeEncode(
                    X509KeyUsageFlags.XCN_CERT_DIGITAL_SIGNATURE_KEY_USAGE | 
                    X509KeyUsageFlags.XCN_CERT_NON_REPUDIATION_KEY_USAGE | 
                    X509KeyUsageFlags.XCN_CERT_KEY_ENCIPHERMENT_KEY_USAGE | 
                    X509KeyUsageFlags.XCN_CERT_DATA_ENCIPHERMENT_KEY_USAGE
                );
                objPkcs10.X509Extensions.Add((CX509Extension)objExtensionKeyUsage);

                // Enhanced Key Usage Extension
                objObjectId.InitializeFromValue("1.3.6.1.5.5.7.3.2"); // OID for Client Authentication usage
                objObjectIds.Add(objObjectId);
                objX509ExtensionEnhancedKeyUsage.InitializeEncode(objObjectIds);
                objPkcs10.X509Extensions.Add((CX509Extension)objX509ExtensionEnhancedKeyUsage);

                //  Encode the name in using the Distinguished Name object
                objDN.Encode(
                    "CN=AlejaCMa",
                    X500NameFlags.XCN_CERT_NAME_STR_NONE
                );

                //  Assing the subject name by using the Distinguished Name object initialized above
                objPkcs10.Subject = objDN;

                // Create enrollment request
                objEnroll.InitializeFromRequest(objPkcs10);
                strRequest = objEnroll.CreateRequest(
                    EncodingType.XCN_CRYPT_STRING_BASE64
                );

                requestText.Text = strRequest;

            } catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
            }
        }

        // Submit request to CA and get response 
        private void sendRequestButton_Click(object sender, EventArgs e)
        {
            //  Create all the objects that will be required
            CCertConfig objCertConfig = new CCertConfigClass();
            CCertRequest objCertRequest = new CCertRequestClass();
            string strCAConfig;
            string strRequest;
            int iDisposition;
            string strDisposition;
            string strCert;

            try
            {
                strRequest = requestText.Text;

                // Get CA config from UI
                //strCAConfig = objCertConfig.GetConfig(CC_DEFAULTCONFIG);
                strCAConfig = objCertConfig.GetConfig(CC_UIPICKCONFIG);                

                // Submit the request
                iDisposition = objCertRequest.Submit(
                    CR_IN_BASE64 | CR_IN_FORMATANY,
                    strRequest,
                    null,
                    strCAConfig
                );

                // Check the submission status
                if (CR_DISP_ISSUED != iDisposition) // Not enrolled
                {
                    strDisposition = objCertRequest.GetDispositionMessage();

                    if (CR_DISP_UNDER_SUBMISSION == iDisposition) // Pending
                    {
                        MessageBox.Show("The submission is pending: " + strDisposition);
                        return;
                    }
                    else // Failed
                    {
                        MessageBox.Show("The submission failed: " + strDisposition);
                        MessageBox.Show("Last status: " + objCertRequest.GetLastStatus().ToString());
                        return;
                    }
                }

                // Get the certificate
                strCert = objCertRequest.GetCertificate(
                    CR_OUT_BASE64 | CR_OUT_CHAIN
                );

                responseText.Text = strCert;
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
            }
        }

        // Install response from CA
        private void acceptPKCS7Button_Click(object sender, EventArgs e)
        {
            //  Create all the objects that will be required
            CX509Enrollment objEnroll = new CX509EnrollmentClass();
            string strCert;
            
            try
            {
                strCert = responseText.Text;

                // Install the certificate
                objEnroll.Initialize(X509CertificateEnrollmentContext.ContextUser);
                objEnroll.InstallResponse(
                    InstallResponseRestrictionFlags.AllowUntrustedRoot,
                    strCert,
                    EncodingType.XCN_CRYPT_STRING_BASE64,
                    null
                );

                MessageBox.Show("Certificate installed!");
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
            }
        }      
    }
}

I hope this helps.

Cheers,

 

Alex (Alejandro Campos Magencio)