Include CmsSigner or other SignedAttributes in Signed Message

[xtomas]

Hello again.

I'm facing problem with missing required SignedAttributes in signed/non-encrypted/non-compressed mime message. Is there any way, how to include for example SigningTime attribute for CmsSigner? I have solved this only by creating own derived classes for WindowsSecureMimeContext and MultipartSigned but it's a lot of duplicate code from MimeKit...

public MimePart Sign(string certificateThumbprint, DigestAlgorithm digestAlgo, Stream content)
{
if (string.IsNullOrEmpty(certificateThumbprint))
throw new ArgumentNullException("certificateThumbprint");

        if (content == null)
            throw new ArgumentNullException("content");

        var contentInfo = new ContentInfo(ReadAllBytes(content));
        var cmsSigner   = GetRealCmsSigner(certificateThumbprint, digestAlgo);

        // add signingTime attribute
        cmsSigner.SignedAttributes.Add(new Pkcs9SigningTime());

        var signed      = new SignedCms(contentInfo, true);

        signed.ComputeSignature(cmsSigner);
        var signedData = signed.Encode();

        return new ApplicationPkcs7Signature(new MemoryStream(signedData, false));
    }

Regards,

Tomas

[jstedfast]

What you can do instead is this:

var mailbox = new SecureMailboxAddress ("Joe Sixpack", "[email protected]", fingerprint);
var signed = ctx.Sign (mailbox, digestAlgo, content);

I've added the Pkcs9SigningTime as a standard attribute.

I haven't really spent a lot of time on the WindowsSecureMimeContext as almost all of my effort has been on the other implementation because my interest has been on making it work cross-platform using Bouncy Castle, so there may be other issues you'll encounter. I do appreciate the bug reports tho, as the WindowsSecureMimeContext should get polished to the same level as the Bouncy Castle backend.

In the other backend, the reason you can override GetCmsSigner(MailboxAddress, DigestAlgorithm) is so that you can add custom attributes. However, with the Windows backend, it uses GetRealCmsSigner() instead which isn't virtual.

[xtomas]

I've tried your fixed code and it works for my case as well. (Btw, I'm implementing As2 Protocol communication)

When will be this fix available on MimeKit Nuget Package?

Tomas

[jstedfast]

I've just released a 1.0.7 NuGet with this fix.

[xtomas]

Thank you. It works now for me 👍

[jstedfast]

Awesome :-)