带有附件的数字签名电子邮件答案

【问题标题】：Digitally signed e-mail with attachment带有附件的数字签名电子邮件
【发布时间】：2014-09-30 09:45:46
【问题描述】：

我有一个邮件脚本，可以发送一封经过数字签名的电子邮件。现在我必须将文件附加到邮件中。我的问题：

如果没有附件，则邮件正常并经过数字签名。没关系。
如果有任何附件，则邮件正文丢失且未签名，但它可以正确发送文件。为什么会这样？

mailer(to, from, from_name, relay, subject, body, attachment_list);

private void mailer(string toaddress, string fromaddress, string fromaddress_disp, string relays, string mailsubject, string bodytext, List<string> att)
{
    string certname = "";

    MailAddress from = new MailAddress(fromaddress, fromaddress_disp);
    MailAddress to = new MailAddress(toaddress);
    MailMessage message = new MailMessage(from, to);

    //this is the attachment part added
    if (att.Count != 0)
        {
            for (int i = 0; i < att.Count; i++)
            {
                Attachment attachment = new Attachment(att[i].ToString());
                message.Attachments.Add(attachment);
            }
        }
    //this is the end of attachment part added

    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
    }
}

问题在于它只在正文上签名：

byte[] messageData = Encoding.ASCII.GetBytes(body);
ContentInfo content = new ContentInfo(messageData);
SignedCms Cms = new SignedCms(new ContentInfo(messageData));

如何签署整封邮件？

【问题讨论】：

标签： c# .net visual-studio-2010 email email-attachments

【解决方案1】：

我终于可以用 EASendMail 解决这个问题了：

http://www.emailarchitect.net/easendmail/dev/csharp.asp

此代码对整个电子邮件消息以及任何附件和/或嵌入图像进行签名。它也非常易于使用。

【讨论】：

链接已失效。