C#利用Spire.Pdf包实现为PDF添加数字签名
作者：旅途。
Spire.PDF for .NET 是一款专业的基于.NET平台的PDF文档控制组件。它能够让开发人员在不使用Adobe Acrobat和其他外部控件的情况下，运用.NET 应用程序创建，阅读，编写和操纵PDF 文档。本文将利用其实现添加数字签名，需要的可以参考一下
背景
- 对PDF文档进行数字签名的需求
- 对PDF文档添加水印的需求
- 网上资料版本不一或不全
本文章提到的Spire.Pdf均是使用的Spire.Pdf for .NET，除此之前还有其他语言的版本，如Spire.Pdf for JAVA；
Spire.Pdf主要用于操作PDF，另外还有Spire.Excel、Spire.Doc等
主要介绍了在C#中使用Spire.Pdf组件包对PDF文档进行数字签名、添加水印功能，旨在引导大家快速、轻松的对PDF文档进行数字签名和添加水印功能；
简介
Spire.PDF for .NET 是一款专业的基于.NET平台的PDF文档控制组件。它能够让开发人员在不使用Adobe Acrobat和其他外部控件的情况下，运用.NET 应用程序创建，阅读，编写和操纵PDF 文档。Spire.PDF for .NET 功能丰富，除了基本的功能比如：绘制多种图形，图片，创建窗体字段，插入页眉页脚，输入数据表，自动对大型表格进行分页外，Spire.PDF for .NET还支持PDF数字签名，将HTML转换成PDF格式，提取PDF文档中的文本信息和图片等，目前Spire.PDF for .NET共有两个版本，一个是免费版本一个是付费版本，免费版本如果只是处理简单的pdf是没问题的，但是如果涉及到输出为pdf则会只显示前10页，第十一页则是预定的购买页介绍，我这里主要是对PDF文档的数字签名和水印，所以不涉及输出pdf；
依赖
本文示例代码依赖于Spire.Pdf，可以在项目中使用NuGet程序包引入。
源码
核心代码
public class DigitalSignature
{
/// <summary>
/// 页顶部红色警告字样覆盖白色图片Base64.
/// </summary>
private const string WatermarkCoverBase64 = "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";
/// <summary>
/// 构造函数.
/// </summary>
/// <param name="waitSignFile">待签名文件.</param>
/// <param name="imageSign">签名图片.</param>
/// <param name="pfx">签名证书.</param>
/// <param name="pfxPwd">签名证书密码.</param>
public DigitalSignature(byte[] waitSignFile, byte[] imageSign, byte[] pfx, string pfxPwd)
{
this.WaitSignFile = waitSignFile;
this.ImageSign = imageSign;
this.Pfx = pfx;
this.PfxPwd = pfxPwd;
}
/// <summary>
/// 构造函数.
/// </summary>
/// <param name="waitSignFile">待签名文件.</param>
/// <param name="charactersSign">签名文字.</param>
/// <param name="signRightLeftWidth">签名右向左宽度.</param>
/// <param name="signBottomUpHeight">签名低向上高度.</param>
/// <param name="pfx">签名证书.</param>
/// <param name="pfxPwd">签名证书密码.</param>
public DigitalSignature(byte[] waitSignFile, string charactersSign, float signRightLeftWidth, float signBottomUpHeight, byte[] pfx, string pfxPwd)
{
this.WaitSignFile = waitSignFile;
this.CharactersSign = charactersSign;
this.SignRightLeftWidth = signRightLeftWidth;
this.SignBottomUpHeight = signBottomUpHeight;
this.Pfx = pfx;
this.PfxPwd = pfxPwd;
}
/// <summary>
/// 构造函数.
/// </summary>
/// <param name="waitSignFile">待签名文件.</param>
/// <param name="imageSign">签名图片.</param>
/// <param name="charactersSign">签名文字.</param>
/// <param name="pfx">签名证书.</param>
/// <param name="pfxPwd">签名证书密码.</param>
public DigitalSignature(byte[] waitSignFile, byte[] imageSign, string charactersSign, byte[] pfx, string pfxPwd)
{
this.WaitSignFile = waitSignFile;
this.ImageSign = imageSign;
this.CharactersSign = charactersSign;
this.Pfx = pfx;
this.PfxPwd = pfxPwd;
}
/// <summary>
/// Gets or sets 待签名文件.
/// </summary>
public byte[] WaitSignFile { get; set; }
/// <summary>
/// Gets or sets 图签名.
/// </summary>
public byte[] ImageSign { get; set; }
/// <summary>
/// Gets or sets 文字签名.
/// </summary>
public string CharactersSign { get; set; }
/// <summary>
/// Gets or sets 签名右向左的宽度.
/// </summary>
public float? SignRightLeftWidth { get; set; }
/// <summary>
/// Gets or sets 签名顶向上高度.
/// </summary>
public float? SignBottomUpHeight { get; set; }
/// <summary>
/// Gets or sets 签名索引页面（不指定默认所有页进行签名）.
/// </summary>
public int? SignIndexPages { get; set; }
/// <summary>
/// Gets or sets Pfx证书.
/// </summary>
public byte[] Pfx { get; set; }
/// <summary>
/// Gets or sets Pfx证书密码.
/// </summary>
public string PfxPwd { get; set; }
public Stream Signature()
{
///加载PDF文档
PdfDocument pdf = new PdfDocument();
pdf.LoadFromBytes(this.WaitSignFile);
if (pdf?.Pages?.Count <= 0)
{
throw new Exception("文件有误");
}
X509Certificate2 x509 = new X509Certificate2(this.Pfx, this.PfxPwd);
PdfOrdinarySignatureMaker signatureMaker = new PdfOrdinarySignatureMaker(pdf, x509);
var appearance = new PdfCustomSignatureAppearance(this.CharactersSign, this.ImageSign, this.SignRightLeftWidth, this.SignBottomUpHeight);
IPdfSignatureAppearance signatureAppearance = appearance;
// 绘画白底图片
PdfRubberStampAnnotation logoStamp = new PdfRubberStampAnnotation(new RectangleF(new PointF(0, 0), new SizeF(350, 22)));
PdfAppearance logoApprearance = new PdfAppearance(logoStamp);
//var logoPath = AppDomain.CurrentDomain.BaseDirectory + "\\white.jpg";
byte[] byt = Convert.FromBase64String(WatermarkCoverBase64);
Stream streamByLogo = new MemoryStream(byt);
PdfImage image = PdfImage.FromStream(streamByLogo);
PdfTemplate template = new PdfTemplate(350, 22);
template.Graphics.DrawImage(image, 0, 0);
logoApprearance.Normal = template;
logoStamp.Appearance = logoApprearance;
if (this.SignIndexPages.HasValue)
{
if (this.SignIndexPages.Value < 0 || this.SignIndexPages.Value > pdf?.Pages?.Count)
{
throw new Exception("签名索引页有误");
}
var page = pdf.Pages[this.SignIndexPages.Value];
// 添加白底图片覆盖页面顶部印记
page.AnnotationsWidget.Add(logoStamp);
// 在页面中的指定位置添加可视化签名
signatureMaker.MakeSignature("signName_", page, page.ActualSize.Width - appearance.SignRightLeftWidth, page.ActualSize.Height - appearance.SignBottomUpHeight, appearance.SignRightLeftWidth, appearance.SignBottomUpHeight, signatureAppearance);
}
else
{
foreach (PdfPageBase page in pdf.Pages)
{
// 添加白底图片覆盖页面顶部印记
page.AnnotationsWidget.Add(logoStamp);
// 在页面中的指定位置添加可视化签名
signatureMaker.MakeSignature("signName_", page, page.ActualSize.Width - appearance.SignRightLeftWidth, page.ActualSize.Height - appearance.SignBottomUpHeight, appearance.SignRightLeftWidth, appearance.SignBottomUpHeight, signatureAppearance);
}
}
MemoryStream stream = new MemoryStream();
pdf.SaveToStream(stream, FileFormat.PDF);
pdf.Close();
return stream;
}
/// <summary>
/// 使用第三方插件 =》 去除 Evaluation Warning : The document was created with Spire.PDF for .NET.
/// </summary>
/// <param name="sourcePdfs">原文件地址</param>
//private static MemoryStream ClearPdfFilesFirstPage(MemoryStream sourcePdf)
//{
// iTextSharp.text.pdf.PdfReader reader = null;
// iTextSharp.text.Document document = new iTextSharp.text.Document();
// iTextSharp.text.pdf.PdfImportedPage page = null;
// iTextSharp.text.pdf.PdfCopy pdfCpy = null;
// int n = 0;
// reader = new iTextSharp.text.pdf.PdfReader(sourcePdf);
// reader.ConsolidateNamedDestinations();
// n = reader.NumberOfPages;
// document = new iTextSharp.text.Document(reader.GetPageSizeWithRotation(1));
// MemoryStream memoryStream = new MemoryStream();
// pdfCpy = new iTextSharp.text.pdf.PdfCopy(document, memoryStream);
// document.Open();
// for (int j = 2; j <= n; j++)
// {
// page = pdfCpy.GetImportedPage(reader, j);
// pdfCpy.AddPage(page);
// }
// reader.Close();
// document.Close();
// return memoryStream;
//}
}
public class PdfCustomSignatureAppearance : IPdfSignatureAppearance
{
public PdfCustomSignatureAppearance(string charactersSign, byte[] sign, float? signRightLeftWidth, float? signBottomUpHeight)
{
this.CharactersSign = charactersSign;
if (sign != null && sign.Length > 0)
{
this.Sign = sign;
MemoryStream ms = new MemoryStream(sign);
var image = System.Drawing.Image.FromStream(ms);
if (!signRightLeftWidth.HasValue)
{
signRightLeftWidth = image.Width;
}
if (!signBottomUpHeight.HasValue)
{
signBottomUpHeight = image.Height;
}
}
this.SignRightLeftWidth = signRightLeftWidth.Value;
this.SignBottomUpHeight = signBottomUpHeight.Value;
}
/// <summary>
/// Gets or sets 签名.
/// </summary>
public byte[] Sign { get; set; }
/// <summary>
/// Gets or sets 签名右向左的宽度.
/// </summary>
public float SignRightLeftWidth { get; set; }
/// <summary>
/// Gets or sets 签名顶向上高度.
/// </summary>
public float SignBottomUpHeight { get; set; }
/// <summary>
/// Gets or sets 文字签名.
/// </summary>
public string CharactersSign { get; set; }
public void Generate(PdfCanvas g)
{
if (!string.IsNullOrWhiteSpace(CharactersSign))
{
float fontSize = 15;
var font = new System.Drawing.Font("Arial", fontSize);
PdfTrueTypeFont fontByPdf = new PdfTrueTypeFont(font, true);
g.DrawString(CharactersSign, fontByPdf, PdfBrushes.Black, new PointF(0, 0));
}
if (this.Sign != null && this.Sign.Length > 0)
{
Stream stream = new MemoryStream(this.Sign);
g.DrawImage(Spire.Pdf.Graphics.PdfImage.FromStream(stream), new PointF(20, 20));
}
}
}调用实现
static void Main(string[] args)
{
/*
前言：最近有个需求是需要对文档进行数字签名；
描述：本示例基于Spire.Pdf组件对PDF进行数字签名，演示了
签名证书使用项目
CreateSelfSignedCertificateByBouncyCastle(https://github.com/daileass/CreateSelfSignedCertificateByBouncyCastle.git)
生成的自签名证书pfx，解决了数字签名后文档头部有警告
*/
var fileCert = System.Environment.CurrentDirectory + "\\Cert\\";
var file = System.Environment.CurrentDirectory + "\\File\\";
var filePath = file + "dome.pdf";
var newFilePath = file + $"dome_{DateTime.Now.ToString("yyyyMMddHHmmss")}.pdf";
var pfxFilePath = fileCert + "edd9386229324d969692dcabf97ac095dpps.fun.pfx";
var pfxFilePwd = "ABCD123456";
var signFilePath = file + "sign.png";
// 数字签名
var digitalSignature = new DigitalSignature(
File2Bytes(filePath),
File2Bytes(signFilePath),
"Sign Here:",
File2Bytes(pfxFilePath),
pfxFilePwd
);
var stream = digitalSignature.Signature();
// 保存签名后的文件
using (var fileStream = File.Create(newFilePath))
{
stream.Seek(0, SeekOrigin.Begin);
stream.CopyTo(fileStream);
}
Console.WriteLine("OK");
Console.ReadLine();
}
/// <summary>
/// 将文件转换为byte数组
/// </summary>
/// <param name="path">文件地址</param>
/// <returns>转换后的byte数组</returns>
public static byte[] File2Bytes(string path)
{
if (!System.IO.File.Exists(path))
{
return new byte[0];
}
FileInfo fi = new FileInfo(path);
byte[] buff = new byte[fi.Length];
FileStream fs = fi.OpenRead();
fs.Read(buff, 0, Convert.ToInt32(fs.Length));
fs.Close();
return buff;
}源码下载：https://github.com/daileass/PDFDigitalSignatureBySelfSignedCertificate
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