Digital Signatures

using System;
using System.Collections.Generic;
using System.Text;


using org.bouncycastle.crypto;
using org.bouncycastle.x509;
using System.Collections;
using org.bouncycastle.pkcs;
using iTextSharp.text.pdf;
using System.IO;
using iTextSharp.text.xml.xmp;
using iTextSharp.text;


///
/// <summary>
/// This Library allows you to sign a PDF document using iTextSharp
/// </summary>
/// <author>Alaa-eddine KADDOURI</author>
///
///

namespace iTextSharpSign
{
    /// <summary>
    /// This class hold the certificate and extract private key needed for e-signature 
    /// </summary>
    class Cert
    {
        #region Attributes

        private string path = "";
        private string password = "";
        private AsymmetricKeyParameter akp;
        private org.bouncycastle.x509.X509Certificate[] chain;

        #endregion

        #region Accessors
        public org.bouncycastle.x509.X509Certificate[] Chain
        {
          get { return chain; }
        }
        public AsymmetricKeyParameter Akp
        {
          get { return akp; }
        }

        public string Path
        {
            get { return path; }
        }

        public string Password
        {
            get { return password; }
            set { password = value; }
        }
        #endregion

        #region Helpers

        private void processCert()
        {
                string alias = null;                                                
                PKCS12Store pk12;

                //First we'll read the certificate file
                pk12 = new PKCS12Store(new FileStream(this.Path, FileMode.Open, FileAccess.Read), this.password.ToCharArray());

                //then Iterate throught certificate entries to find the private key entry
                IEnumerator i = pk12.aliases();
                while (i.MoveNext())
                {
                    alias = ((string)i.Current);
                    if (pk12.isKeyEntry(alias))
                        break;
                }

                this.akp = pk12.getKey(alias).getKey();
                X509CertificateEntry[] ce = pk12.getCertificateChain(alias);
                this.chain = new org.bouncycastle.x509.X509Certificate[ce.Length];
                for (int k = 0; k < ce.Length; ++k)
                    chain[k] = ce[k].getCertificate();

            }
        #endregion

        #region Constructors
            public Cert()
            { }
            public Cert(string cpath)
            {
                this.path = cpath;
                this.processCert();
            }
            public Cert(string cpath, string cpassword)
            {
                this.path = cpath;
                this.Password = cpassword;
                this.processCert();
            }
        #endregion

    }

    /// <summary>
    /// This is a holder class for PDF metadata
    /// </summary>
    class MetaData
    {
        private Hashtable info = new Hashtable();

        public Hashtable Info
        {
            get { return info; }
            set { info = value; }
        }

        public string Author
        {
            get { return (string)info["Author"]; }
            set { info.Add("Author", value); }
        }
        public string Title
        {
            get { return (string)info["Title"]; }
            set { info.Add("Title", value); }
        }
        public string Subject
        {
            get { return (string)info["Subject"]; }
            set { info.Add("Subject", value); }
        }
        public string Keywords
        {
            get { return (string)info["Keywords"]; }
            set { info.Add("Keywords", value); }
        }
        public string Producer
        {
            get { return (string)info["Producer"]; }
            set { info.Add("Producer", value); }
        }

        public string Creator
        {
            get { return (string)info["Creator"]; }
            set { info.Add("Creator", value); }
        }

        public Hashtable getMetaData()
        {
            return this.info;
        }
        public byte[] getStreamedMetaData()
        {
            MemoryStream os = new System.IO.MemoryStream();
            XmpWriter xmp = new XmpWriter(os, this.info);            
            xmp.Close();            
            return os.ToArray();
        }

    }


    /// <summary>
    /// this is the most important class
    /// it uses iTextSharp library to sign a PDF document
    /// </summary>
    class PDFSigner
    {
        private string inputPDF = "";
        private string outputPDF = "";
        private Cert myCert;
        private MetaData metadata;

        public PDFSigner(string input, string output)
        {
            this.inputPDF = input;
            this.outputPDF = output;
        }

        public PDFSigner(string input, string output, Cert cert)
        {
            this.inputPDF = input;
            this.outputPDF = output;
            this.myCert = cert;
        }
        public PDFSigner(string input, string output, MetaData md)
        {
            this.inputPDF = input;
            this.outputPDF = output;
            this.metadata = md;
        }
        public PDFSigner(string input, string output, Cert cert, MetaData md)
        {
            this.inputPDF = input;
            this.outputPDF = output;
            this.myCert = cert;
            this.metadata = md;
        }

        public void Verify()
        {
        }


        public void Sign(string SigReason, string SigContact, string SigLocation, bool visible, float x, float y, float x1, float y1,bool val1,bool val2,bool val3,bool def)
        {
            PdfReader reader = new PdfReader(this.inputPDF);
            //Activate MultiSignatures
            PdfStamper st = PdfStamper.CreateSignature(reader, new FileStream(this.outputPDF, FileMode.Create, FileAccess.Write), '\0', null, true);
            //To disable Multi signatures uncomment this line : every new signature will invalidate older ones !
            //PdfStamper st = PdfStamper.CreateSignature(reader, new FileStream(this.outputPDF, FileMode.Create, FileAccess.Write), '\0'); 

            st.MoreInfo = this.metadata.getMetaData();
            st.XmpMetadata = this.metadata.getStreamedMetaData();
            PdfSignatureAppearance sap = st.SignatureAppearance;
            sap.Acro6Layers = true;
            sap.SetCrypto(this.myCert.Akp, this.myCert.Chain, null, PdfSignatureAppearance.WINCER_SIGNED);
            if (def == false)
            {
                if (val1 == false)
                {
                    sap.Reason = SigReason;
                }
                if (val2 == false)
                {
                    sap.Contact = SigContact;
                }
                if (val3 == false)
                {
                    sap.Location = SigLocation;
                }
            }

            if (visible)
            {
                sap.SetVisibleSignature(new iTextSharp.text.Rectangle(x, y, x1, y1), 1, null);

                if (def == true)
                {

                    Font fontSig = FontFactory.GetFont(FontFactory.HELVETICA, (float)7, Font.NORMAL);
                    sap.Layer2Font = fontSig;
                    //sap.Render = PdfSignatureAppearance.SignatureRender.Description;

                    string signerName = PdfPKCS7.GetSubjectFields(this.myCert.Chain[0]).GetField("CN");
                    PdfTemplate template = st.SignatureAppearance.GetLayer(2);
                    template.MoveTo(0, 200);
                    template.LineTo(500, 0);
                    template.Stroke();
                    template.BeginText();
                    BaseFont bf1 = BaseFont.CreateFont(BaseFont.HELVETICA, BaseFont.CP1252, BaseFont.NOT_EMBEDDED);
                    template.SetFontAndSize(bf1, 10);
                    template.SetTextMatrix(1, 1);
                    template.ShowTextAligned(PdfContentByte.ALIGN_LEFT, "" + signerName + "", 0, 40, 0);

                    BaseFont bf = BaseFont.CreateFont(BaseFont.HELVETICA, BaseFont.CP1252, BaseFont.NOT_EMBEDDED);
                    template.SetFontAndSize(bf, 7);
                    template.SetTextMatrix(1, 1);
                    template.ShowTextAligned(PdfContentByte.ALIGN_LEFT, "" + System.DateTime.Now.ToString("yyyy.MM.dd HH:mm:ss zzz") + "", 50, 30, 0);

                    template.SetFontAndSize(bf, 7);
                    template.SetTextMatrix(1, 1);
                    template.ShowTextAligned(PdfContentByte.ALIGN_LEFT, "Signer:", 0, 25, 0);

                    template.SetFontAndSize(bf, 7);
                    template.SetTextMatrix(1, 1);
                    template.ShowTextAligned(PdfContentByte.ALIGN_LEFT, "" + "CN=" + PdfPKCS7.GetSubjectFields(myCert.Chain[0]).GetField("CN") + "", 10, 17, 0);

                   

                    template.SetFontAndSize(bf, 7);
                    template.SetTextMatrix(1, 1);
                    template.ShowTextAligned(PdfContentByte.ALIGN_LEFT, "" + "C=" + PdfPKCS7.GetSubjectFields(myCert.Chain[0]).GetField("C") + "", 10, 10, 0);


                    template.EndText();
                }
            }
            st.Close();
        }

    }
}