(Visual FoxPro) 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.

Chilkat ActiveX Downloads ActiveX for 32-bit and 64-bit Windows

LOCAL lnSuccess
LOCAL loCrypt
LOCAL loBinData
LOCAL loCert
LOCAL loCertChain
LOCAL lnNumCerts
LOCAL i

lnSuccess = 0

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

loCrypt = CreateObject('Chilkat.Crypt2')

* Verify a PKCS7 signed-data (opaque signature) file and extract the original content to a file.
lnSuccess = loCrypt.VerifyP7M("qa_data/p7m/opaqueSig.p7","qa_output/originalData.dat")
IF (lnSuccess = 0) THEN
    ? loCrypt.LastErrorText
    RELEASE loCrypt
    CANCEL
ENDIF

* Alternatively, we can do it in memory...
loBinData = CreateObject('Chilkat.BinData')
lnSuccess = 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.
lnSuccess = loCrypt.OpaqueVerifyBd(loBinData)
IF (lnSuccess = 0) THEN
    ? loCrypt.LastErrorText
    RELEASE loCrypt
    RELEASE loBinData
    CANCEL
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 each signing certificate, and build the certificate chain for each.
loCert = CreateObject('Chilkat.Cert')
loCertChain = CreateObject('Chilkat.CertChain')
lnNumCerts = loCrypt.NumSignerCerts
i = 0
DO WHILE i < lnNumCerts
    loCrypt.LastSignerCert(i,loCert)
    ? loCert.SubjectDN

    lnSuccess = loCert.BuildCertChain(loCertChain)
    IF (lnSuccess = 0) THEN
        ? loCert.LastErrorText
        RELEASE loCrypt
        RELEASE loBinData
        RELEASE loCert
        RELEASE loCertChain
        CANCEL
    ENDIF

    i = i + 1
ENDDO

RELEASE loCrypt
RELEASE loBinData
RELEASE loCert
RELEASE loCertChain