outlook无法打开s/mime签名的邮件

Question

我需要使用s/mime对电子邮件进行数字签名。我为我的附件创建了一个独立的签名，但outlook无法打开它："；无法打开此项目。您的数字ID名称无法被底层安全系统找到"；。证书安装在这台电脑上，有smth需要在这个代码中进行调整：

const int CHARS_IN_LINE = 64;
StringBuilder message = new StringBuilder();
message.AppendLine("Content-Type: multipart/signed; protocol="application/pkcs7-signature";");
message.AppendLine(" boundary="__multipart-signed-boundary__"");
message.AppendLine("Content-Transfer-Encoding: 7bit");
message.AppendLine("MIME-Version: 1.0");
message.AppendLine("Subject: " + tbMessageSubject.Text);
message.AppendLine();
message.AppendLine("--__multipart-signed-boundary__");
message.AppendLine("Content-Type: text/xml; charset="windows - 1251"");
message.AppendLine("Content-Disposition: attachment; ");
message.AppendLine(" filename="" + Path.GetFileName(filename) + """);
message.AppendLine("Content-Transfer-Encoding: base64");
message.AppendLine();
var dataToSign = File.ReadAllBytes(filePath);
var base64Data = Convert.ToBase64String(dataToSign, Base64FormattingOptions.None);
var base64DataSb = new StringBuilder(base64Data);
for (int i = CHARS_IN_LINE; i < base64DataSb.Length; i += CHARS_IN_LINE + 2) // rn
base64DataSb.Insert(i, "rn");
message.AppendLine(base64DataSb.ToString());
message.AppendLine("--__multipart-signed-boundary__");
message.AppendLine("Content-Type: application/pkcs7-signature; name="smime.p7m"");
message.AppendLine("Content-Transfer-Encoding: base64");
message.AppendLine("Content-Disposition: attachment; filename=smime.p7s");
message.AppendLine();
CmsSigner signer = new CmsSigner(clientCert);
SignedCms cms = new SignedCms(new ContentInfo(dataToSign), true);
cms.ComputeSignature(signer);
var signature = cms.Encode();
var base64Signature = Convert.ToBase64String(signature, Base64FormattingOptions.None);
var base64Sb = new StringBuilder(base64Signature);
for (int i = CHARS_IN_LINE; i < base64Sb.Length; i += CHARS_IN_LINE + 2) // rn
base64Sb.Insert(i, "rn");
message.AppendLine(base64Sb.ToString());
message.AppendLine();
message.AppendLine("--__multipart-signed-boundary__--");
message.AppendLine(".");
var stream = new MemoryStream(Encoding.ASCII.GetBytes(message.ToString()));
MailMessage mail = new MailMessage();
mail.From = new MailAddress(tbEmailFrom.Text);
mail.To.Add(new MailAddress(tbEmailTo.Text));
AlternateView alternateView = new AlternateView(stream, "application/pkcs7-mime; smime-type=signed-data; name=smime.p7m");
alternateView.TransferEncoding = TransferEncoding.SevenBit;
mail.AlternateViews.Add(alternateView);
SmtpClient client = new SmtpClient(host, port);
client.EnableSsl = chbUseSSL.Checked;
client.Send(mail);

Answer 1

最后，问题出现在AlternateView中指定的mediaType中，正确的方式是：

AlternateView alternateView = new AlternateView(stream, "multipart/signed; protocol="application/pkcs7-signature"; boundary="__multipart-signed-boundary__"");
alternateView.TransferEncoding = TransferEncoding.SevenBit;

感谢jdweng，我需要签署的不是附件，而是带有标题的附件(第一个带有附件的__multipart-signed-boundary(