//// This code is part of Document Solutions for PDF .NET demos.// Copyright (c) MESCIUS inc. All rights reserved.//using System;using System.IO;using System.Linq;using System.Collections.Generic;using System.Security.Cryptography.X509Certificates;
using GrapeCity.Documents.Pdf;using GrapeCity.Documents.Pdf.Security;using GrapeCity.Documents.Pdf.AcroForms;

namespace DsPdfWeb.Demos{    // This sample shows how to sign an existing PDF file containing    // an empty signature field with a signature that complies with    // the various PAdES (PDF Advanced Electronic Signatures) levels.    // Note that when run online, this sample simply returns an unsigned    // PDF with an empty signature field. To actually sign the PDF    // you will need to provide a valid .pfx file (see "JohnDoe.pfx").    // The sample contains 5 methods that can be used to sign a PDF    // with the various PAdES levels, the last 3 methods can be    // used in a chain to incrementally increase the signature strength.    // To check the signature compliance, open the signed PDF in Acrobat    // Reader and inspect the signature properties.    //    // IMPORTANT! The code in this sample WILL NOT work correctly    // unless DsPdf is licensed with a valid license key.    // Email us.sales@mescius.com to obtain a trial key.    public class PadesLevels    {        // Certificate issued by CA Cert Signing Authority, used for verification:        static X509Certificate2 s_caCertRoot = new X509Certificate2(Path.Combine("Resources", "Misc", "CACertRoot.crt"));        // TODO: replace with a real certificate:        static X509Certificate2 s_cert = new X509Certificate2(Path.Combine("Resources", "Misc", "JohnDoe.pfx"), "secret");
        static PadesLevels()        {            // TODO: GcPdfDocument MUST BE LICENSED for the signatures to remain valid,            // as otherwise the license nag text added when saving the PDF invalidates            // incremental updates. Email us.sales@mescius.com to obtain a trial key.            // GcPdfDocument.SetLicenseKey("my key");        }
        public void CreatePDF(Stream stream, int paramsIdx = 0)        {            CreatePDF(stream, GetSampleParamsList()[paramsIdx]);        }
        // While this sample includes code that does the actual signing and time stamping,        // that code is NOT executed by the online demo. So the online sample driver        // simply returns the PDF that includes info about the selected PAdES level,        // and can be signed or time stamped using a valid certificate.        // You can copy the corresponding code and use it in your applications.        public void CreatePDF(Stream stream, string[] sampleParams)        {            // TODO: change to true to actually run the signing/time stamping code:            bool doSigning = false;
            // The unsigned PDF with a signature field to sign:            var fn = Path.Combine("Resources", "PDFs", sampleParams[3]);
            if (doSigning)            {                // Running this code will produce 5 PDFs with increasing PAdES levels:
                // PAdES B-B:                Do_B_B(fn);                // PAdES B-T:                Do_B_T(fn);                // Note that the next 3 steps use PDFs produced by the previous step,                // incrementally adding verification info:                // PAdES B-LT:                Do_B_LT("B-T.pdf");                // PAdES B-LTA:                Do_B_LTA("B-LT.pdf");                // LTV Enabled:                Do_B_LTA_LTV("B-LTA.pdf");            }
            // Copy the source PDF to output stream            // to provide the demo result:            using var fs = File.OpenRead(fn);            fs.CopyTo(stream);        }
        // Signs a PDF with a PAdES B-B Level signature:        void Do_B_B(string fn)        {            using FileStream fs = File.OpenRead(fn);            var doc = new GcPdfDocument();            doc.Load(fs);
            var signField = doc.AcroForm.Fields.FirstOrDefault(f_ => f_ is SignatureField);            if (signField == null)                throw new Exception("Could not find a signature field.");
            var sp = new SignatureProperties()            {                SignatureField = signField,                SignatureBuilder = new Pkcs7SignatureBuilder(s_cert)                {                    Format = Pkcs7SignatureBuilder.SignatureFormat.ETSI_CAdES_detached,                },            };            // Sign and save the PDF to a file:            doc.Sign(sp, "B-B.pdf");        }
        // Signs a PDF with a PAdES B-T Level signature:        void Do_B_T(string fn)        {            using FileStream fs = File.OpenRead(fn);            var doc = new GcPdfDocument();            doc.Load(fs);
            var signField = doc.AcroForm.Fields.FirstOrDefault(f_ => f_ is SignatureField);            if (signField == null)                throw new Exception("Could not find a signature field.");
            var sp = new SignatureProperties()            {                SignatureField = signField,                SignatureBuilder = new Pkcs7SignatureBuilder(s_cert)                {                    Format = Pkcs7SignatureBuilder.SignatureFormat.ETSI_CAdES_detached,                },                TimeStamp = new TimeStamp(@"http://ts.ssl.com"),            };            // Sign and save the PDF to a file:            doc.Sign(sp, "B-T.pdf");        }
        // Adds LTV information to a B-T level signature (e.g. as created by the do_B_T method above),        // which makes the signature compliant with PAdES B-LT:        void Do_B_LT(string fn)        {            using FileStream fs = File.OpenRead(fn);            var doc = new GcPdfDocument();            doc.Load(fs);
            var signField = doc.AcroForm.Fields.FirstOrDefault(f_ => f_ is SignatureField);            if (signField == null)                throw new Exception("Could not find a signature field.");
            // Get the signature and add verification information for it:            var sig = (Signature)signField.Value;            var vp = new DocumentSecurityStore.VerificationParams();            vp.Certificates = new X509Certificate2[] { s_caCertRoot };            if (!doc.SecurityStore.AddVerification(sig, vp))                throw new Exception($"Could not add verification for {sig.Name}.");
            // Save the PDF to a file using incremental update so that the signature remains valid:            doc.Save("B-LT.pdf", SaveMode.IncrementalUpdate);        }
        // Adds time stamp to a signed PDF (e.g. as created by the do_B_LT method above),        // which makes the document compliant with B-LTA level:        void Do_B_LTA(string fn)        {            using FileStream fs = File.OpenRead(fn);            var doc = new GcPdfDocument();            doc.Load(fs);
            var ts = new TimeStampProperties()            {                TimeStamp = new TimeStamp(@"http://ts.ssl.com"),            };            // Save the PDF to a file adding a time stamp to it:            doc.TimeStamp(ts, "B-LTA.pdf");        }
        // Adds verification information for a PDF time-stamp (e.g. as created by the do_B_LTA method above)        // which makes the signature LTV enabled:        void Do_B_LTA_LTV(string fn)        {            using FileStream fs = File.OpenRead(fn);            var doc = new GcPdfDocument();            doc.Load(fs);
            var signField = doc.AcroForm.Fields.FirstOrDefault(f_ => f_ is SignatureField);            if (signField == null)                throw new Exception("Could not find a signature field.");
            // Get the signature and add verification information for it:            var sig = (Signature)signField.Value;            if (!doc.SecurityStore.AddVerification(sig))                throw new Exception($"Could not add verification for {sig.Name}.");
            // Save the PDF to a file using incremental update so that the signature remains valid:            doc.Save("B-LTA_LTV.pdf", SaveMode.IncrementalUpdate);        }
        public static List<string[]> GetSampleParamsList()        {            // Strings are name, description, info, rest are arbitrary strings:            return new List<string[]>()            {                new string[] { "@b-sign/PAdES B-B Level", "How to sign a PDF complying with PAdES B-B level", "",                    "PAdES-B-B.pdf" },                new string[] { "@b-sign/PAdES B-T Level", "How to sign a PDF complying with PAdES B-T level", "",                    "PAdES-B-T.pdf" },                new string[] { "@b-sign/PAdES B-LT Level", "How to add LTV information to a signature", "",                    "PAdES-B-LT.pdf" },                new string[] { "@b-sign/PAdES B-LTA Level", "How to time stamp a signed PDF", "",                    "PAdES-B-LTA.pdf" },                new string[] { "@b-sign/LTV Enabled Signature", "How to make a signature LTV enabled", "",                    "PAdES-B-LTA-LTV.pdf" },            };        }    }}