Question

我想在不使用任何第三方API的情况下发送加密和签名的邮件。如果我只发送带有签名的备用视图，Windows Mail可以验证它。如果我只发送带有加密数据的备用视图，Windows Mail可以解密它。但如果我发送两个，Windows Mail获得2个附件。如果我签署encryptedBytes并将这些带符号的字节添加到备用视图中，它只验证签名并且消息为空。有什么想法吗？

MailMessage message = new MailMessage();
message.From = new MailAddress(lblMail.Text);
message.Subject = txtSubject.Text;

string body = "Content-Type: text/plain\r\nContent-Transfer-Encoding: 7Bit\r\n\r\n" + structForm();

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

message.To.Add(new MailAddress(provMail));

CmsRecipient recipient = new CmsRecipient(SubjectIdentifierType.SubjectKeyIdentifier, this.certificate);
envelopedCms.Encrypt(recipient);

byte[] encryptedBytes = envelopedCms.Encode();

SignedCms Cms = new SignedCms(new ContentInfo(encryptedBytes));
CmsSigner Signer = new CmsSigner(SubjectIdentifierType.IssuerAndSerialNumber, new X509Certificate2(@"c:\serv.pfx","123"));

Cms.ComputeSignature(Signer);
byte[] SignedBytes = Cms.Encode();

MemoryStream encryptedStream = new MemoryStream(encryptedBytes);
AlternateView encryptedView = new AlternateView(encryptedStream, "application/pkcs7-mime; smime-type=signed--data;name=smime.p7m");
message.AlternateViews.Add(encryptedView);
MemoryStream signedStream = new MemoryStream(SignedBytes);
AlternateView signedView = new AlternateView(signedStream, "application/pkcs7-mime; smime-type=signed-data;name=sig.p7m");
message.AlternateViews.Add(signedView);


System.Net.NetworkCredential SMTPUserInfo = new System.Net.NetworkCredential("emailaddress@xpto.com", "XXXXXX");
SmtpClient client = new SmtpClient("smtp.xpto.com");

client.UseDefaultCredentials = false;
client.Credentials = SMTPUserInfo;

client.Send(message);

Label2.Text = "Assinado e cifrado!";

Answer 1

您应首先签名，然后加密。

虽然原始的CMS和S / MIME规范允许您按任意顺序执行操作，但后来的工作指出，签署一个您无法阅读的文档是一个非常糟糕的主意。签名应该在纯文本上。

生成的MIME消息应该只有一个部分，应该是S / MIME封装数据。您的邮件有两部分，加密部分标有错误标记的签名数据内容类型。创建并签署SignedCms对象。对其进行编码，并使用编码值作为EnvelopedCms对象的内容。加密，并使用其编码值作为MailMessage的内容，内容类型为“application / pkcs7-mime; smime-type = enveloped-data”。

使用C＃发送加密和签名的电子邮件

1 个答案: