How to add smime certificate to outlook contacts programmatically?

Question

We're currently working on a project that requires adding S/MIME certificates to outlook contacts. Currently there's no api to add or retrieve S/MIME related information with existing solutions (We looked into Graph API but it doesn't provide the functionality. We've also looked into outlook addin JS docs. It also, doesn't reference anything related to S/MIME).

Our guess is that we need to add the certificates in the local device. We got this code snippet on Github which we think adds S/MIME certificate to our own email only but not contacts.

So, how to add or import S/MIME certificate of outlook contacts Programmatically?

Outlook JS / Web Add-ins do not support contacts. (or S/MIME related information) — Outlook Add-ins Team - MSFT, May 23 '22 at 19:10
Thanks for the information! So, to add S/MIME certificates programmatically, what should we do? Can VSTO do this? We've seen somewhere that VSTO might get deprecated (Some issue with .NET) — null_override, May 24 '22 at 18:24
Also, can you provide the exact path that S/MIME certificates get added when someone imports the cert via Outlook app? — null_override, May 24 '22 at 18:26
Sorry, the members of this account only have expertise regarding the Outlook JS / Web Add-ins. Hopefully, you can find an answer to your question regarding VSTO in the answer below. — Outlook Add-ins Team - MSFT, May 31 '22 at 19:37

score 2 · Accepted Answer · answered May 22 '22 at 21:27

I found a dated solution attempt in this post:

   private static object[] BuildProperty(byte[] rawData)
    {
        using (MemoryStream ms = new MemoryStream())
        {
            byte[] headerWithoutLength = { 0x01, 0x00, 0x08, 0x00, 0x01, 0x00, 0x00, 0x00, 0x03, 0x00 };
            ms.Write(headerWithoutLength, 0, headerWithoutLength.Length);
            byte[] lengthBytes = BitConverter.GetBytes((short)(rawData.Length + 4));
            ms.WriteByte(lengthBytes[0]);
            ms.WriteByte(lengthBytes[1]);
            ms.Write(rawData, 0, rawData.Length);
            byte[] footer = { 0x06, 0x00, 0x08, 0x00, 0x01, 0x00, 0x00, 0x00, 0x20, 0x00, 0x08, 0x00, 
                0x07, 0x00, 0x00, 0x00, 0x02, 0x00, 0x04, 0x00 };
            ms.Write(footer, 0, footer.Length);

            object[] o = new object[] { ms.ToArray() };
            return o;
        }

    }

    private static void Create()
    {
        OutLook.Application outlookObj = new OutLook.Application();
        try
        {
            X509Certificate2 existingCert = new X509Certificate2(@"[path to my certificate].cer");
            byte[] result = existingCert.RawData;

            OutLook.MAPIFolder fldContacts = (OutLook.MAPIFolder)outlookObj.Session.GetDefaultFolder(OutLook.OlDefaultFolders.olFolderContacts);

            OutLook.ContactItem newContact = (OutLook.ContactItem)fldContacts.Items.Add(OutLook.OlItemType.olContactItem);

            newContact.FirstName = "Test Name";
            newContact.FileAs = "Test Name";

            object[] o = BuildProperty(result);
            newContact.PropertyAccessor.SetProperty("http://schemas.microsoft.com/mapi/proptag/0x3A701102", o);

            newContact.Save();
        }
        finally
        {
            Marshal.ReleaseComObject(outlookObj);
        }
    }

It creates a new contact and assigns a certificate to it. To assign a certificate to an existing contact should be similar. Additional error checking is required to make this snippet useful and trustworthy.

How to add smime certificate to outlook contacts programmatically?

1 Answers1