(PowerShell) Verify Opaque Signature and Retrieve Signing Certificates

Demonstrates how to verify a PCKS7 opaque digital signature (signed data), extract the original file/data, and then extract the certificate(s) that were used to sign.

Note: This example requires Chilkat v11.0.0 or greater.

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

$success = $false

# This example assumes the Chilkat API to have been previously unlocked.
# See Global Unlock Sample for sample code.

$crypt = New-Object Chilkat.Crypt2

# Verify a PKCS7 signed-data (opaque signature) file and extract the original content to a file.
$success = $crypt.VerifyP7M("qa_data/p7m/opaqueSig.p7","qa_output/originalData.dat")
if ($success -eq $false) {
    $($crypt.LastErrorText)
    exit
}

# Alternatively, we can do it in memory...
$binData = New-Object Chilkat.BinData
$success = $binData.LoadFile("qa_data/p7m/opaqueSig.p7")
# Your app should check for success, but we'll skip the check for brevity..

# If verified, the signature is unwrapped and binData is replaced with the original data that was signed.
$success = $crypt.OpaqueVerifyBd($binData)
if ($success -eq $false) {
    $($crypt.LastErrorText)
    exit
}

# For our testing, we signed some text, so we can get it from the binData..
$("Original Data:")
$($binData.GetString("utf-8"))

# After any method call that verifies a signature, the crypt object will contain the certificate(s)
# that were used for signing (assuming the X.509 certs were available in the signature, which is typically the case).

# Get each signing certificate, and build the certificate chain for each.
$cert = New-Object Chilkat.Cert
$certChain = New-Object Chilkat.CertChain
$numCerts = $crypt.NumSignerCerts
$i = 0
while ($i -lt $numCerts) {
    $crypt.LastSignerCert($i,$cert)
    $($cert.SubjectDN)

    $success = $cert.BuildCertChain($certChain)
    if ($success -eq $false) {
        $($cert.LastErrorText)
        exit
    }

    $i = $i + 1
}