VB.NET

Check for an S/MIME Signing Time

Demonstrates the Chilkat Mime.HasSignatureSigningTime method, which returns whether the signer at a zero-based index included a CMS signingTime signed attribute. The only argument is the signer index; use NumSignerCerts for the count.

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: A signing time records when the signer claims to have signed, which matters for auditing and for validating a certificate that has since expired. It is an optional signed attribute, so not every signature has one — this predicate lets you check before calling GetSignatureSigningTimeStr, avoiding an error for signers that omitted it. Being a signed attribute, it is covered by the signature and cannot be altered undetected.

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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 verifying, check whether each signer included a CMS signingTime signed attribute.  The
'  only argument is the zero-based signer index.
success = mime.Verify()
If (success <> True) Then
    Debug.WriteLine(mime.LastErrorText)
    Exit Sub
End If


Dim n As Integer = mime.NumSignerCerts
Dim i As Integer
For i = 0 To n - 1
    If (mime.HasSignatureSigningTime(i)) Then
        Debug.WriteLine("Signer " & i & " included a signing time.")
    Else
        Debug.WriteLine("Signer " & i & " did not include a signing time.")
    End If

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