Itextsharp Digital sign and show info(subject and

问题:

I am working on one project using iTextSharp to digitally sign PDF file, it's workable, but need directly show the certificate's info on PDF (Please refer to attached image), how to do or set any parameter of iTextSharp?

    public static X509Certificate2 cert;
    //Sign with certificate selection in the windows certificate store
    public static void Sign(string pdfFile, string outPdfFile){
        Program.WriteLog("Signing Digital Certificate");            
        string IssuerName = null;
        X509Store store = new X509Store(StoreLocation.CurrentUser);
        store.Open(OpenFlags.ReadOnly);
        IssuerName = Properties.Settings.Default.IssuerName;
        if (IssuerName.Length > 0)
            cert = store.Certificates.Find(X509FindType.FindByIssuerName, IssuerName, false)[0];
        if (cert == null)
        {
            //manually chose the certificate in the store
            X509Certificate2Collection sel = X509Certificate2UI.SelectFromCollection(store.Certificates, null, null, X509SelectionFlag.SingleSelection);
            if (sel.Count > 0)
                cert = sel[0];
            else
            {
                Console.WriteLine("Certificate not found");
                return;
            }
        }
        PdfReader reader = new PdfReader(pdfFile); // source pdf file
        FileStream os = new FileStream(outPdfFile, FileMode.Create);  //the output pdf file
        PdfStamper stamper = PdfStamper.CreateSignature(reader, os, '\0');
        stamper.SetEncryption(PdfWriter.STRENGTH128BITS, "", null, PdfWriter.AllowCopy | PdfWriter.AllowPrinting);
        try
        {
            Org.BouncyCastle.X509.X509CertificateParser cp = new Org.BouncyCastle.X509.X509CertificateParser();
            Org.BouncyCastle.X509.X509Certificate[] chain = new Org.BouncyCastle.X509.X509Certificate[] { cp.ReadCertificate(cert.RawData) };
            IExternalSignature externalSignature = new X509Certificate2Signature(cert, "SHA-1");
            PdfSignatureAppearance appearance = stamper.SignatureAppearance;
            //here set signatureAppearance at your will
            appearance.Reason = Properties.Settings.Default.DigitalSignReason;
            appearance.Location = Properties.Settings.Default.DigitalSignLocation;
            appearance.Contact = Properties.Settings.Default.DigitalSignContact;
            if (Properties.Settings.Default.DigitalSignAppearance == 1)
            {
                appearance.SetVisibleSignature(new iTextSharp.text.Rectangle(20, 10, 170, 60), 1, "Signed");
            }
            appearance.SignatureRenderingMode = PdfSignatureAppearance.RenderingMode.DESCRIPTION;
            MakeSignature.SignDetached(appearance, externalSignature, chain, null, null, null, 0, CryptoStandard.CMS);
            //MakeSignature.SignDetached(signatureAppearance, externalSignature, chain, null, null, null, 0, CryptoStandard.CADES);
        }catch(Exception e){
            Console.WriteLine(e.Message, 1);
            File.Delete(outPdfFile);
        }
        finally
        {
            if (reader != null)
                reader.Close();
            if (stamper != null)
                stamper.Close();
            if (os != null)
                os.Close();                
        }
    }

回答1:

According to your screen shot you want a special kind of signature, a certification signature. You can create such a signature by adding

appearance.CertificationLevel = PdfSignatureAppearance.CERTIFIED_FORM_FILLING_AND_ANNOTATIONS;

to your code. Alternatively, to allow less changes, use CERTIFIED_FORM_FILLING or CERTIFIED_NO_CHANGES_ALLOWED.