VB.NET

Get the S/MIME Signer's Certificate

Demonstrates the Chilkat Mime.LastSignerCert method, which loads the signer certificate at a zero-based index from the most recent successful verification (or security-unwrapping) into a Cert. The first argument is the signer index and the second is the receiving Cert.

Note: The file paths are relative to the application's current working directory. Absolute paths may also be used. Supply the paths appropriate to your own environment.

Background: Verifying tells you the signature is mathematically valid, but you usually also need to know who signed — the subject, the issuer, the validity dates — to decide whether to trust it. This retrieves each signer's certificate after verification so your code can inspect and apply its own trust rules. A message can have multiple signers, so iterate from 0 to NumSignerCerts - 1.

Chilkat VB.NET Downloads

Download Chilkat for VB.NET

VB.NET

Dim success As Boolean = False

Dim mime As New Chilkat.Mime
success = mime.LoadMimeFile("qa_data/signed.eml")
If (success = False) Then
    Debug.WriteLine(mime.LastErrorText)
    Exit Sub
End If


'  After a successful verification, load each signer's certificate to inspect it.  The 1st argument
'  is the zero-based signer index and the 2nd is a Cert object that receives the certificate.
success = mime.Verify()
If (success <> True) Then
    Debug.WriteLine(mime.LastErrorText)
    Exit Sub
End If


Dim n As Integer = mime.NumSignerCerts
Dim cert As New Chilkat.Cert
Dim i As Integer
For i = 0 To n - 1
    success = mime.LastSignerCert(i,cert)
    If (success = False) Then
        Debug.WriteLine(mime.LastErrorText)
        Exit Sub
    End If

    Debug.WriteLine("Signer " & i & ": " & cert.SubjectCN & " (issued by " & cert.IssuerCN & ")")
Next