(Lianja) 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 Lianja Extension Download Chilkat Lianja Extension

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

loCrypt = createobject("CkCrypt2")

// Verify a PKCS7 signed-data (opaque signature) file and extract the original content to a file.
llSuccess = loCrypt.VerifyP7M("qa_data/p7m/opaqueSig.p7","qa_output/originalData.dat")
if (llSuccess <> .T.) then
    ? loCrypt.LastErrorText
    release loCrypt
    return
endif

// Alternatively, we can do it in memory...
loBinData = createobject("CkBinData")
llSuccess = loBinData.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.
llSuccess = loCrypt.OpaqueVerifyBd(loBinData)
if (llSuccess <> .T.) then
    ? loCrypt.LastErrorText
    release loCrypt
    release loBinData
    return
endif

// For our testing, we signed some text, so we can get it from the binData..
? "Original Data:"
? loBinData.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..
lnNumCerts = loCrypt.NumSignerCerts
i = 0
do while i < lnNumCerts
    loCert = loCrypt.GetSignerCert(i)
    ? loCert.SubjectDN
    release loCert
    i = i + 1
enddo

// 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
do while i < lnNumCerts
    loCertChain = loCrypt.GetSignerCertChain(i)
    // You can examine the various properties and methods for certChain in the online
    // reference documentation...
    release loCertChain
    i = i + 1
enddo


release loCrypt
release loBinData