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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.

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Add-Type -Path "C:\chilkat\ChilkatDotNet47-x64\ChilkatDotNet47.dll"

$success = $false

$mime = New-Object Chilkat.Mime
$success = $mime.LoadMimeFile("qa_data/signed.eml")
if ($success -eq $false) {
    $($mime.LastErrorText)
    exit
}

#  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 -ne $true) {
    $($mime.LastErrorText)
    exit
}

$n = $mime.NumSignerCerts
$cert = New-Object Chilkat.Cert

for ($i = 0; $i -le $n - 1; $i++) {
    $success = $mime.LastSignerCert($i,$cert)
    if ($success -eq $false) {
        $($mime.LastErrorText)
        exit
    }

    $("Signer " + $i + ": " + $cert.SubjectCN + " (issued by " + $cert.IssuerCN + ")")
}