So I have been working with the Java implementation of IText, but now I'm pretty much writing a port of our signing process to C#, and I've hit a snag. So when im signing my document using the SetVisibleSignature(rect, page, name) overload, it signs the document as expected(as long as the signature field does not exist), but when i use the overload SetVisibleSignature(name) to sign an existing field, it does not actually sign the document. Am I doing something stupid perhaps and missing something?
Thank you for any help.
Updated Code
using iTextSharp.text;
using iTextSharp.text.pdf;
using iTextSharp.text.pdf.security;
using Org.BouncyCastle.Security;
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Security.Cryptography;
using System.Security.Cryptography.X509Certificates;
using BouncyCastle = Org.BouncyCastle;
public class DocumentSigner : IDocumentSigner
{
private const string _datetimeFormat = "dd/MM/yyyy hh:mm:ss";
private readonly IDateTimeProvider _dateTimeProvider;
private readonly ISettingManager _settingManager;
public DocumentSigner(IDateTimeProvider dateTimeProvider, ISettingManager settingManager)
{
Guard.ArgumentNotNull(dateTimeProvider, "dateTimeProvider");
Guard.ArgumentNotNull(settingManager, "settingManager");
_dateTimeProvider = dateTimeProvider;
_settingManager = settingManager;
}
public byte[] Sign(Certificate certificate, SigningInformation information, List<SigningBlock> signingBlocks, List<MemberItemSignature> signatureImages, byte[] document, bool certify)
{
document = AddMetaData(information, document);
document = AddSignatureFields(information, signingBlocks, document);
return SignDocument(certificate, information, signingBlocks, signatureImages, document, certify);
}
private byte[] AddMetaData(SigningInformation information, byte[] document)
{
if (information.CustomProperties != null && information.CustomProperties.Any())
{
using (MemoryStream outputStream = new MemoryStream())
{
using (PdfReader reader = new PdfReader(document))
{
using (PdfStamper stamper = new PdfStamper(reader, outputStream, '\0', true))
{
Dictionary<string, string> currentProperties = reader.Info;
foreach (string key in information.CustomProperties.Keys)
{
if (currentProperties.ContainsKey(key))
{
currentProperties[key] = information.CustomProperties[key];
}
else
{
currentProperties.Add(key, information.CustomProperties[key]);
}
}
stamper.MoreInfo = currentProperties;
}
}
return outputStream.ToArray();
}
}
return document;
}
private byte[] AddSignatureFields(SigningInformation information, List<SigningBlock> signingBlocks, byte[] document)
{
for (int i = 0; i < signingBlocks.Count; i++)
{
using (MemoryStream outputStream = new MemoryStream())
{
using (PdfReader reader = new PdfReader(document))
{
using (PdfStamper stamper = new PdfStamper(reader, outputStream, '\0', true))
{
CreateSignatureField(reader, stamper, signingBlocks[i]);
}
}
document = outputStream.ToArray();
}
}
return document;
}
private PdfSignatureAppearance CreatePdfAppearance(PdfStamper stamper, SigningInformation information, bool certify)
{
PdfSignatureAppearance appearance = stamper.SignatureAppearance;
appearance.Location = information.Location;
appearance.Reason = information.Purpose;
appearance.SignatureRenderingMode = PdfSignatureAppearance.RenderingMode.DESCRIPTION;
CreatePdfAppearanceCertifyDocument(appearance, certify);
return appearance;
}
private void CreatePdfAppearanceCertifyDocument(PdfSignatureAppearance appearance, bool certify)
{
if (certify)
{
appearance.CertificationLevel = PdfSignatureAppearance.CERTIFIED_FORM_FILLING;
}
else
{
appearance.CertificationLevel = PdfSignatureAppearance.NOT_CERTIFIED;
}
}
private PdfStamper CreatePdfStamper(PdfReader reader, MemoryStream outputStream, byte[] document)
{
return PdfStamper.CreateSignature(reader, outputStream, '\0', null, true);
}
private void CreateSignatureField(PdfReader reader, PdfStamper stamper, SigningBlock signingBlock)
{
if (signingBlock == null)
{
return;
}
if (!DoesSignatureFieldExist(reader, signingBlock.Name))
{
PdfFormField signatureField = PdfFormField.CreateSignature(stamper.Writer);
signatureField.SetWidget(new Rectangle(signingBlock.X, signingBlock.Y, signingBlock.X + signingBlock.Width, signingBlock.Y + signingBlock.Height), null);
signatureField.Flags = PdfAnnotation.FLAGS_PRINT;
signatureField.FieldName = signingBlock.Name;
signatureField.Page = signingBlock.Page;
stamper.AddAnnotation(signatureField, signingBlock.Page);
}
}
private bool DoesSignatureFieldExist(PdfReader reader, string signatureFieldName)
{
if (String.IsNullOrWhiteSpace(signatureFieldName))
{
return false;
}
return reader.AcroFields.DoesSignatureFieldExist(signatureFieldName);
}
private byte[] GetSignatureImage(List<MemberItemSignature> signatureImages, string signingBlockName)
{
MemberItemSignature signature = signingBlockName.Contains("Initial") ? signatureImages.Where(image => image.Use == SignatureUses.Initial).FirstOrDefault() : signatureImages.Where(image => image.Use == SignatureUses.Signature).FirstOrDefault();
if (signature != null)
{
return signature.Image;
}
else
{
return null;
}
}
private byte[] SignDocument(Certificate certificate, SigningInformation information, List<SigningBlock> signingBlocks, List<MemberItemSignature> signatureImages, byte[] document, bool certify)
{
for (int i = 0; i < signingBlocks.Count; i++)
{
using (MemoryStream outputStream = new MemoryStream())
{
using (PdfReader reader = new PdfReader(document))
{
using (PdfStamper stamper = CreatePdfStamper(reader, outputStream, document))
{
SigningBlock signingBlock = signingBlocks[i];
PdfSignatureAppearance appearance = CreatePdfAppearance(stamper, information, certify && i == 0);
SignDocumentSigningBlock(certificate, information, signingBlock, appearance, stamper, GetSignatureImage(signatureImages, signingBlock.Name));
}
}
document = outputStream.ToArray();
}
}
return document;
}
private void SignDocumentSigningBlock(Certificate certificate, SigningInformation information, SigningBlock block, PdfSignatureAppearance appearance, PdfStamper stamper, byte[] signatureImage)
{
X509Certificate2 x509Certificate = new X509Certificate2(certificate.Bytes, certificate.Password, X509KeyStorageFlags.Exportable);
appearance.SetVisibleSignature(block.Name);
SignDocumentSigningBlockWithImage(signatureImage, appearance);
SignDocumentSigningBlockWithText(appearance, x509Certificate);
using (RSACryptoServiceProvider rsa = (RSACryptoServiceProvider)x509Certificate.PrivateKey)
{
IExternalSignature externalSignature = new PrivateKeySignature(DotNetUtilities.GetRsaKeyPair(rsa).Private, _settingManager["DocumentSigningEncryptionHashAlgorithm"]);
MakeSignature.SignDetached(appearance, externalSignature, new BouncyCastle::X509.X509Certificate[] { DotNetUtilities.FromX509Certificate(x509Certificate) }, null, null, new TSAClientBouncyCastle(_settingManager["DocumentSigningTimestampingServiceAddress"]), Int32.Parse(_settingManager["DocumentSigningEstimatedTimestampSize"]), CryptoStandard.CMS);
}
}
private void SignDocumentSigningBlockWithImage(byte[] signatureImage, PdfSignatureAppearance appearance)
{
if (signatureImage != null && signatureImage.Length > 0)
{
Image signatureImageInstance = Image.GetInstance(signatureImage);
appearance.Image = signatureImageInstance;
appearance.SignatureGraphic = signatureImageInstance;
}
}
private void SignDocumentSigningBlockWithText(PdfSignatureAppearance appearance, X509Certificate2 x509Certificate)
{
if (x509Certificate == null)
{
return;
}
appearance.Layer2Text = SignDocumentSigningBlockWithTextBuildText(x509Certificate);
appearance.Layer2Font = new Font(Font.FontFamily.COURIER, 7.0f, Font.NORMAL, BaseColor.LIGHT_GRAY);
appearance.Acro6Layers = true;
}
private string SignDocumentSigningBlockWithTextBuildText(X509Certificate2 x509Certificate)
{
Dictionary<string, string> fields = SignDocumentSigningBlockWithTextBuildTextIssuerFields(x509Certificate.IssuerName.Name);
string organization = fields.Keys.Contains("O") ? fields["O"] : String.Empty;
string commonName = fields.Keys.Contains("CN") ? fields["CN"] : String.Empty;
string signDate = _dateTimeProvider.Now.ToString(_datetimeFormat);
string expirationDate = x509Certificate.NotAfter.ToString(_datetimeFormat);
return "Digitally signed by " + organization + "\nSignee: " + commonName + "\nSign date: " + signDate + "\n" + "Expiration date: " + expirationDate;
}
private Dictionary<string, string> SignDocumentSigningBlockWithTextBuildTextIssuerFields(string issuer)
{
Dictionary<string, string> fields = new Dictionary<string, string>();
string[] issuerFields = issuer.Split(',');
foreach (string field in issuerFields)
{
string[] fieldSplit = field.Split('=');
string key = fieldSplit[0].Trim();
string value = fieldSplit[1].Trim();
if (!fields.Keys.Contains(key))
{
fields.Add(key, value);
}
else
{
fields[key] = value;
}
}
return fields;
}
}
Values
_settingManager["DocumentSigningEncryptionHashAlgorithm"] = "SHA-256";
_settingManager["DocumentSigningTimestampingServiceAddress"] = "http://services.globaltrustfinder.com/adss/tsa";
_settingManager["DocumentSigningEstimatedTimestampSize"] = 104000;
