(C++) 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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#include <CkCrypt2.h>
#include <CkBinData.h>
#include <CkCert.h>
#include <CkCertChain.h>

void ChilkatSample(void)
    {
    bool success = false;

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

    CkCrypt2 crypt;

    // 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 == false) {
        std::cout << crypt.lastErrorText() << "\r\n";
        return;
    }

    // Alternatively, we can do it in memory...
    CkBinData 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 == false) {
        std::cout << crypt.lastErrorText() << "\r\n";
        return;
    }

    // For our testing, we signed some text, so we can get it from the binData..
    std::cout << "Original Data:" << "\r\n";
    std::cout << binData.getString("utf-8") << "\r\n";

    // 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.
    CkCert cert;
    CkCertChain certChain;
    int numCerts = crypt.get_NumSignerCerts();
    int i = 0;
    while (i < numCerts) {
        crypt.LastSignerCert(i,cert);
        std::cout << cert.subjectDN() << "\r\n";

        success = cert.BuildCertChain(certChain);
        if (success == false) {
            std::cout << cert.lastErrorText() << "\r\n";
            return;
        }

        i = i + 1;
    }
    }