数字签名签名者姓名未显示

Question

在 C# 中，为什么在由 Itextsharp 库签名时不在 pdf 中显示签名者姓名？我尝试通过数字证书 USB 令牌创建签名的 PDF。当我在每个页面上生成签名时，时间签名无法显示歌手姓名。

获取证书的代码如下：

X509Certificate2 certClient = null;
X509Store st = new X509Store(StoreName.My, StoreLocation.CurrentUser);
string filename = @"..\List1.pdf";
st.Open(OpenFlags.MaxAllowed);
X509Certificate2Collection collection = st.Certificates;
foreach (X509Certificate2 cert in collection)
{                    
    if (cert.Subject.ToLower().Contains("serialnumber"))
    {
        certClient = cert;
        string username = certClient.Subject;
        string startdate = certClient.GetEffectiveDateString();
        string enddate = certClient.GetExpirationDateString();           
    }
}          
st.Close();
IList<X509Certificate> chain = new List<X509Certificate>();
X509Chain x509Chain = new X509Chain();
x509Chain.Build(certClient);
foreach (X509ChainElement x509ChainElement in x509Chain.ChainElements)
{
     chain.Add(DotNetUtilities.FromX509Certificate(x509ChainElement.Certificate));
}
PdfReader inputPdf = new PdfReader(filename);
string dest = @"..\sign10a.pdf";
PdfReader reader = new PdfReader(filename);
FileStream os = new FileStream(dest, FileMode.Create, FileAccess.Write);
PdfStamper stamper = PdfStamper.CreateSignature(reader, os, '[=10=]');
PdfSignatureAppearance appearance = stamper.SignatureAppearance;
appearance.Acro6Layers = false;
appearance.Image = null;
appearance.SignatureRenderingMode = PdfSignatureAppearance.RenderingMode.DESCRIPTION;
appearance.SetVisibleSignature(new iTextSharp.text.Rectangle(100, 10, 250, 100), reader.NumberOfPages, null);
IExternalSignature externalSignature1 = new X509Certificate2Signature(certClient, "SHA-256"); 
AllPagesSignatureContainer allPagesContainer = new AllPagesSignatureContainer(appearance, externalSignature1, chain);
MakeSignature.SignExternalContainer(appearance, allPagesContainer, 8192);
reader.Close();
stamper.Dispose();

这是我的多重外观代码：

public class AllPagesSignatureContainer : IExternalSignatureContainer
{
    public AllPagesSignatureContainer(PdfSignatureAppearance appearance, IExternalSignature externalSignature, ICollection<X509Certificate> chain)
    {
        this.appearance = appearance;
        this.chain = chain;
        this.externalSignature = externalSignature;
    }

    public void ModifySigningDictionary(PdfDictionary signDic)
    {
        signDic.Put(PdfName.FILTER, PdfName.ADOBE_PPKMS);
        signDic.Put(PdfName.SUBFILTER, PdfName.ADBE_PKCS7_DETACHED);
        PdfStamper stamper = appearance.Stamper;
        PdfReader reader = stamper.Reader;
        PdfDictionary xobject1 = new PdfDictionary();
        PdfDictionary xobject2 = new PdfDictionary();
        xobject1.Put(PdfName.N, appearance.GetAppearance().IndirectReference);
        xobject2.Put(PdfName.AP, xobject1);
        PdfIndirectReference PRef = stamper.Writer.PdfIndirectReference;
        PdfLiteral PRefLiteral = new PdfLiteral((PRef.Number + 1 + 2 * (reader.NumberOfPages - 1)) + " 0 R");

        for (int i = 1; i < reader.NumberOfPages; i++)
        {
            var signatureField = PdfFormField.CreateSignature(stamper.Writer);
            signatureField.Put(PdfName.T, new PdfString("ClientSignature_" + i.ToString()));
            signatureField.Put(PdfName.V, PRefLiteral);
            signatureField.Put(PdfName.F, new PdfNumber("132"));
            signatureField.SetWidget(appearance.Rect, null);
            signatureField.Put(PdfName.SUBTYPE, PdfName.WIDGET);
            signatureField.Put(PdfName.AP, xobject1);
            signatureField.SetPage();
            Console.WriteLine(signatureField);

            stamper.AddAnnotation(signatureField, i);
        }
    }

    public byte[] Sign(Stream data)
    {
        String hashAlgorithm = externalSignature.GetHashAlgorithm();
        PdfPKCS7 sgn = new PdfPKCS7(null, chain, hashAlgorithm, false);
        IDigest messageDigest = DigestUtilities.GetDigest(hashAlgorithm);
        byte[] hash = DigestAlgorithms.Digest(data, hashAlgorithm);
        byte[] sh = sgn.getAuthenticatedAttributeBytes(hash, null, null, CryptoStandard.CMS);
        byte[] extSignature = externalSignature.Sign(sh);
        sgn.SetExternalDigest(extSignature, null, externalSignature.GetEncryptionAlgorithm());
        return sgn.GetEncodedPKCS7(hash, null, null, null, CryptoStandard.CMS);            
    }
    PdfSignatureAppearance appearance;
    ICollection<X509Certificate> chain;
    IExternalSignature externalSignature;
}

数字签名显示多页但无法显示签名者姓名。

希望对您有所帮助，我根据在互联网上找到的示例编写了代码。它会工作，但只有歌手名字不显示。

Answer 1

您想知道为什么在您的可视化中

“Digitally signed by”后没有名字。

iTextSharp 创建这样的文本行：

buf.Append("Digitally signed by ");
String name = null;
CertificateInfo.X509Name x500name = CertificateInfo.GetSubjectFields((X509Certificate)signCertificate);
if (x500name != null) {
    name = x500name.GetField("CN");
    if (name == null)
        name = x500name.GetField("E");
}
if (name == null)
    name = "";
buf.Append(name).Append('\n');

（摘自PdfSignatureAppearance.GetAppearance()）

signCertificate 这里是 BouncyCastle X509Certificate 否则可通过 PdfSignatureAppearance 属性 Certificate.

访问

但是在您的代码中您没有设置 appearance.Certificate 属性。因此，在上面的代码中 x500Name 是 null。因此 name 是 "" 并且在 "Digitally signed by ".

之后没有添加名称

如果您希望 iText 自动填写该字段，请提供必要的信息并设置 appearance.Certificate。或者，您可以自己生成外观。

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