(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 <C_CkCrypt2.h>
#include <C_CkBinData.h>
#include <C_CkCert.h>
#include <C_CkCertChain.h>

void ChilkatSample(void)
    {
    BOOL success;
    HCkCrypt2 crypt;
    HCkBinData binData;
    HCkCert cert;
    HCkCertChain certChain;
    int numCerts;
    int i;

    success = FALSE;

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

    crypt = CkCrypt2_Create();

    // Verify a PKCS7 signed-data (opaque signature) file and extract the original content to a file.
    success = CkCrypt2_VerifyP7M(crypt,"qa_data/p7m/opaqueSig.p7","qa_output/originalData.dat");
    if (success == FALSE) {
        printf("%s\n",CkCrypt2_lastErrorText(crypt));
        CkCrypt2_Dispose(crypt);
        return;
    }

    // Alternatively, we can do it in memory...
    binData = CkBinData_Create();
    success = CkBinData_LoadFile(binData,"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 = CkCrypt2_OpaqueVerifyBd(crypt,binData);
    if (success == FALSE) {
        printf("%s\n",CkCrypt2_lastErrorText(crypt));
        CkCrypt2_Dispose(crypt);
        CkBinData_Dispose(binData);
        return;
    }

    // For our testing, we signed some text, so we can get it from the binData..
    printf("Original Data:\n");
    printf("%s\n",CkBinData_getString(binData,"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 = CkCert_Create();
    certChain = CkCertChain_Create();
    numCerts = CkCrypt2_getNumSignerCerts(crypt);
    i = 0;
    while (i < numCerts) {
        CkCrypt2_LastSignerCert(crypt,i,cert);
        printf("%s\n",CkCert_subjectDN(cert));

        success = CkCert_BuildCertChain(cert,certChain);
        if (success == FALSE) {
            printf("%s\n",CkCert_lastErrorText(cert));
            CkCrypt2_Dispose(crypt);
            CkBinData_Dispose(binData);
            CkCert_Dispose(cert);
            CkCertChain_Dispose(certChain);
            return;
        }

        i = i + 1;
    }



    CkCrypt2_Dispose(crypt);
    CkBinData_Dispose(binData);
    CkCert_Dispose(cert);
    CkCertChain_Dispose(certChain);

    }