[英]Howto sign a pdf using iText which contains an OCSP which is embedded
[英]Howto sign a pdf with iText with a PKCS1 signature
我需要使用將返回 PKCS1 簽名的外部服務簽署 pdf 文檔。 這意味着我必須在 IExternalSignatureContainer 實例中添加公鑰。 我在整個簽名過程中使用 iText 7。
iText 網站上有一個很好的例子
我確實實現了這個示例,但我沒有使用服務來簽署 hash 值,而是使用 X509 證書進行。 問題是簽名在某種程度上無效(它說文件在簽名后被更改)。 證書似乎是正確集成的。
我在一個文件中創建了整個唱歌過程的示例。 所需參考資料:
(自簽名)公鑰、私鑰和簽名 pdf 文檔的示例可在此處下載: http://www.filedropper.com/pdfsignfiles
知道我在這里做錯了什么嗎?
示例代碼(一個文件中的兩個類可用於控制台應用程序):
using System;
using System.Collections.Generic;
using System.IO;
using System.Security.Cryptography;
using System.Security.Cryptography.X509Certificates;
using System.Text;
using iText.Kernel.Pdf;
using iText.Signatures;
using Org.BouncyCastle.X509;
using X509Certificate = Org.BouncyCastle.X509.X509Certificate;
namespace SignExternalTestManuel
{
class Program
{
public static void Main(String[] args)
{
string filePath = @"c:\temp\pdfsign\";
string pdfToSign = Path.Combine(filePath, @"test.pdf");
string destinationFile = Path.Combine(filePath, "test_signed.pdf");
string userCertificatePublicKey = Path.Combine(filePath, "BITSignTestManuel5Base64.cer");
string caCertificatePublicKey = Path.Combine(filePath, "BITRoot5Base64.cer");
string privateKeyFile = Path.Combine(filePath, "BITSignTestManuel5.pfx");
string privateKeyPassword = "test";
PdfReader reader = new PdfReader(pdfToSign);
using (FileStream os = new FileStream(destinationFile, FileMode.OpenOrCreate))
{
StampingProperties stampingProperties = new StampingProperties();
//For any signature in the Pdf but the first one, you need to use appendMode
// stampingProperties.useAppendMode();
stampingProperties.UseAppendMode();
PdfSigner pdfSigner = new PdfSigner(reader, os, stampingProperties);
pdfSigner.SetCertificationLevel(PdfSigner.CERTIFIED_NO_CHANGES_ALLOWED);
IExternalSignatureContainer external = new GsSignatureContainer(
PdfName.Adobe_PPKLite,
PdfName.Adbe_pkcs7_detached,
userCertificatePublicKey,
caCertificatePublicKey,
privateKeyFile,
privateKeyPassword);
pdfSigner.SignExternalContainer(external, 32000);
}
}
}
public class GsSignatureContainer : IExternalSignatureContainer
{
private PdfDictionary sigDic;
private string userCertificatePublicKey;
private string caCertificatePublicKey;
private string privateKeyFile;
private string privateKeyPassword;
public GsSignatureContainer(PdfName filter, PdfName subFilter, string userCertificatePublicKey, string caCertificatePublicKey, string privateKeyFile, string privateKeyPassword)
{
sigDic = new PdfDictionary();
sigDic.Put(PdfName.Filter, filter);
sigDic.Put(PdfName.SubFilter, subFilter);
this.userCertificatePublicKey = userCertificatePublicKey;
this.caCertificatePublicKey = caCertificatePublicKey;
this.privateKeyFile = privateKeyFile;
this.privateKeyPassword = privateKeyPassword;
}
/// <summary>
/// Implementation based on https://kb.itextpdf.com/home/it7kb/examples/how-to-use-a-digital-signing-service-dss-such-as-globalsign-with-itext-7#HowtouseaDigitalSigningService(DSS)suchasGlobalSign,withiText7-Examplecode
/// </summary>
/// <param name="pdfStream"></param>
/// <returns></returns>
public byte[] Sign(Stream pdfStream)
{
//Create the certificate chaing since the signature is just a PKCS1, the certificates must be added to the signature
string cert = System.IO.File.ReadAllText(userCertificatePublicKey);
string ca = System.IO.File.ReadAllText(caCertificatePublicKey);
X509Certificate[] chain = CreateChain(cert, ca);
String hashAlgorithm = DigestAlgorithms.SHA256;
PdfPKCS7 pkcs7Signature = new PdfPKCS7(null, chain, hashAlgorithm, false);
//Create the hash of of the pdf document
byte[] hash = DigestAlgorithms.Digest(pdfStream, DigestAlgorithms.GetMessageDigest(hashAlgorithm));
//TODO: Unclear whether i need to use this. It is from the example, but maybe only required for
//byte[] sh = pkcs7Signature.GetAuthenticatedAttributeBytes(hash, null, null, PdfSigner.CryptoStandard.CMS);
//using (SHA256 sha256 = SHA256.Create())
//{
// sh = sha256.ComputeHash(hash);
//}
//Create the actual signautre (This will be done via Service)
byte[] signature = CreateSignature(hash, privateKeyFile, privateKeyPassword);
pkcs7Signature.SetExternalDigest(signature, null, "RSA");
return pkcs7Signature.GetEncodedPKCS7(hash, null, null, null, PdfSigner.CryptoStandard.CMS);
}
public void ModifySigningDictionary(PdfDictionary signDic)
{
signDic.PutAll(sigDic);
}
private static X509Certificate[] CreateChain(String cert, String ca)
{
//Note: The root certificate could be omitted and it would still work
X509Certificate[] chainy = new X509Certificate[2];
X509CertificateParser parser = new X509CertificateParser();
chainy[0] = new X509Certificate(parser.ReadCertificate(Encoding.UTF8.GetBytes(cert))
.CertificateStructure);
chainy[1] = new X509Certificate(parser.ReadCertificate(Encoding.UTF8.GetBytes(ca))
.CertificateStructure);
return chainy;
}
#region "Create signature, will be done by an actual service"
private byte[] CreateSignature(byte[] hash, string privateKeyFile, string privateKeyPassword)
{
X509Certificate2 rootCertificateWithPrivateKey = new X509Certificate2();
byte[] rawData = System.IO.File.ReadAllBytes(privateKeyFile);
rootCertificateWithPrivateKey.Import(rawData, privateKeyPassword, X509KeyStorageFlags.Exportable);
using (var key = rootCertificateWithPrivateKey.GetRSAPrivateKey())
{
return key.SignData(hash, HashAlgorithmName.SHA256, RSASignaturePadding.Pkcs1);
}
}
#endregion
}
}
我想我在我的代碼中發現了問題。 我在沒有使用 GetAuthenticatedAttributeBytes 的情況下直接簽署了 hash 值。 只要我添加以下代碼,然后簽名 sh 而不是 hash,簽名就會生效:
//Create the hash based on the document hash which is suitable for pdf siging
X509Certificate2 rootCertificateWithoutPrivateKey = new X509Certificate2();
rootCertificateWithoutPrivateKey.Import(caCertificatePublicKey);
X509Certificate rootCertBouncy = DotNetUtilities.FromX509Certificate(rootCertificateWithoutPrivateKey);
List<X509Certificate> c = new List<X509Certificate>();
c.Add(rootCertBouncy);
PdfPKCS7 sgn = new PdfPKCS7(null, c.ToArray(), hashAlgorithm, false);
byte[] sh = sgn.GetAuthenticatedAttributeBytes(hash, null, null, PdfSigner.CryptoStandard.CMS);
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