带有数字签名和嵌入图像的电子邮件答案

【问题标题】：Email with digital signature and embedded image带有数字签名和嵌入图像的电子邮件
【发布时间】：2014-05-27 22:21:17
【问题描述】：

我有以下用于发送数字签名电子邮件的工作代码。我必须插入一个带有 gif 徽标的基于 html 的签名，该签名应该从程序集资源中提取。我四处搜索，发现Convert.ToBase64String() 是可能的解决方案，但 Outlook 不显示图像。第二种方法是LinkedResource 和AlternateView 嵌入我的图像，但实际上我无法使用下面的代码让它工作。我已经有一个AlternateView 来发送带有数字签名的电子邮件。是否也可以以某种方式添加图像？

所以mailer(to, from, from_name, relay, subject, body, cc1, cc2);。

private void mailer(string toaddress, string fromaddress, string fromaddress_disp, string relays, string mailsubject, string bodytext, string ccman, string cccct)
{
    string certname = "";

    MailAddress from = new MailAddress(fromaddress, fromaddress_disp);
    MailAddress to = new MailAddress(toaddress);
    MailAddress cc_man = new MailAddress(ccman);
    MailAddress cc_cct = new MailAddress(cccct);
    MailMessage message = new MailMessage(from, to);
    message.CC.Add(cc_man);
    message.CC.Add(cc_cct);
    message.Subject = mailsubject;
    message.IsBodyHtml = true;
    string body = "Content-Type: text/html; charset=iso-8859-1 \r\nContent-Transfer-Encoding: 8bit\r\n\r\n" + bodytext;
    byte[] messageData = Encoding.ASCII.GetBytes(body);
    ContentInfo content = new ContentInfo(messageData);

    SignedCms Cms = new SignedCms(new ContentInfo(messageData));
    X509Store store = new X509Store(StoreLocation.CurrentUser);
    store.Open(OpenFlags.ReadOnly);

    RSACryptoServiceProvider csp = null;
    X509Certificate2Collection certCollection = store.Certificates;
    X509Certificate2 cert = null;
    foreach (X509Certificate2 c in certCollection)
    {
        if ((c.Subject.Contains("myEmailAddress")) && (c.FriendlyName.Contains("CompanyEmailDigSig")))
        {
            cert = c;
            break;
        }
    }

    if (cert != null)
    {
            csp = (RSACryptoServiceProvider)cert.PrivateKey;
    }
    else
    {
        throw new Exception("Valid certificate was not found");
    }

    CmsSigner Signer = new CmsSigner(SubjectIdentifierType.IssuerAndSerialNumber, cert);
    Cms.ComputeSignature(Signer);
    byte[] SignedBytes = Cms.Encode();
    MemoryStream signedStream = new MemoryStream(SignedBytes);
    AlternateView signedView = new AlternateView(signedStream, "application/pkcs7-mime; smime-type=signed-data; name=sig.p7m");
    message.AlternateViews.Add(signedView);
    SmtpClient client = new SmtpClient(relays);
    store.Close();

    try
    {
        client.Send(message);
    }
    catch (Exception ex)
    {
    //exception
    }
}

编辑：我不得不重新打开这个帖子，因为之前接受的答案不够好。

【问题讨论】：

标签： c# email embedded-resource digital-signature

【解决方案1】：

我确实认为使用System.Net.Mail 对整个消息进行签名是不可能的。但这也可能对您有所帮助：- Send Email in C# Tutorial - SSL, HTML, Embedded Image, S/MIME

还要检查这个：-(Send Email with Embedded Images - ImportHtml - Example)：-

using System;
using System.Collections.Generic;
using System.Text;
using EASendMail; //add EASendMail namespace

namespace mysendemail
{
    class Program
    {
        static void Main(string[] args)
        {
            SmtpMail oMail = new SmtpMail("TryIt");
            SmtpClient oSmtp = new SmtpClient();

            // Set sender email address, please change it to yours
            oMail.From = "test@emailarchitect.net";

            // Set recipient email address, please change it to yours
            oMail.To = "support@emailarchitect.net";

            // Set email subject
            oMail.Subject = "test html email with attachment";

            // Your SMTP server address
            SmtpServer oServer = new SmtpServer("smtp.emailarchitect.net");

            // User and password for ESMTP authentication, if your server doesn't require
            // User authentication, please remove the following codes.            
            oServer.User = "test@emailarchitect.net";
            oServer.Password = "testpassword";

            // If your SMTP server requires SSL connection, please add this line
            // oServer.ConnectType = SmtpConnectType.ConnectSSLAuto;

            try
            {
               // Import html body and also import linked image as embedded images.
               oMail.ImportHtml( "<html><body>test <img src=\"test.gif\"> importhtml</body></html>",
                    "c:\\my picture", //test.gif is in c:\\my picture
                    ImportHtmlBodyOptions.ImportLocalPictures | ImportHtmlBodyOptions.ImportCss );

                Console.WriteLine("start to send email with embedded image...");
                oSmtp.SendMail(oServer, oMail);
                Console.WriteLine("email was sent successfully!");
            }
            catch (Exception ep)
            {
                Console.WriteLine("failed to send email with the following error:");
                Console.WriteLine(ep.Message);
            }
        }
    }
}

【讨论】：