(Java) 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.

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import com.chilkatsoft.*;

public class ChilkatExample {

  static {
    try {
        System.loadLibrary("chilkat");
    } catch (UnsatisfiedLinkError e) {
      System.err.println("Native code library failed to load.\n" + e);
      System.exit(1);
    }
  }

  public static void main(String argv[])
  {
    // This example assumes the Chilkat API to have been previously unlocked.
    // See Global Unlock Sample for sample code.

    CkCrypt2 crypt = new CkCrypt2();

    // Verify a PKCS7 signed-data (opaque signature) file and extract the original content to a file.
    boolean success = crypt.VerifyP7M("qa_data/p7m/opaqueSig.p7","qa_output/originalData.dat");
    if (success != true) {
        System.out.println(crypt.lastErrorText());
        return;
        }

    // Alternatively, we can do it in memory...
    CkBinData binData = new CkBinData();
    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 != true) {
        System.out.println(crypt.lastErrorText());
        return;
        }

    // For our testing, we signed some text, so we can get it from the binData..
    System.out.println("Original Data:");
    System.out.println(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..
    int numCerts = crypt.get_NumSignerCerts();
    int i = 0;
    while (i < numCerts) {
        CkCert cert = crypt.GetSignerCert(i);
        System.out.println(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 < numCerts) {
        CkCertChain certChain = crypt.GetSignerCertChain(i);
        // You can examine the various properties and methods for certChain in the online
        // reference documentation...

        i = i+1;
        }
  }
}