B4X

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 B4X Downloads

Download Chilkat for B4X

B4X

Dim success As Boolean = False

Dim mime As ChilkatMime
mime.Initialize
success = mime.LoadMimeFile("qa_data/signed.eml")
If success = False Then
    Log(mime.LastErrorText)
    Return
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
    Log(mime.LastErrorText)
    Return
End If


Dim n As Int = mime.NumSignerCerts
Dim cert As ChilkatCert
cert.Initialize("cert")
Dim i As Int
For i = 0 To n - 1
    success = mime.LastSignerCert(i, cert)
    If success = False Then
        Log(mime.LastErrorText)
        Return
    End If

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