(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.

Chilkat .NET Downloads Chilkat .NET Assemblies

Add-Type -Path "C:\chilkat\ChilkatDotNet47-9.5.0-x64\ChilkatDotNet47.dll"

# 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 -ne $true) {
    $($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 -ne $true) {
    $($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 the number of signing certificates, and get each..
$numCerts = $crypt.NumSignerCerts
$i = 0
while ($i -lt $numCerts) {
    $cert = $crypt.GetSignerCert($i)
    $($cert.SubjectDN)

    $i = $i + 1
}

# We could also get the complete certificate chain of each signer cert,
# assuming the certs in the chain of authentication to the trusted root
# are available on the system, or provided to Chilkat by some other means
# (such as via the XmlCertVault class, the TrustedRoots class, etc.)
$i = 0
while ($i -lt $numCerts) {
    $certChain = $crypt.GetSignerCertChain($i)
    # You can examine the various properties and methods for certChain in the online
    # reference documentation...

    $i = $i + 1
}