(Java) IMAP Download and Verify Signed MIME

Downloads the unmodified MIME of a digitally signed email, saves the .p7s signature (and other MIME parts), then loads the email into a Chilkat email object (which unwraps the S/MIME and verifies the signature) and then saves attachments (if the MIME parts were not already saved).

Chilkat Java Downloads Java Libs for Windows, MacOS, Linux, Alpine Linux, Solaris Java Libs for Android

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

    CkImap imap = new CkImap();

    // Connect to an IMAP server.
    // Use TLS
    imap.put_Ssl(true);
    imap.put_Port(993);
    boolean success = imap.Connect("imap.someMailServer.com");
    if (success != true) {
        System.out.println(imap.lastErrorText());
        return;
        }

    success = imap.Login("myLogin","myPassword");
    if (success != true) {
        System.out.println(imap.lastErrorText());
        return;
        }

    // Select an IMAP mailbox
    success = imap.SelectMailbox("Inbox");
    if (success != true) {
        System.out.println(imap.lastErrorText());
        return;
        }

    // Download the 1st email (as MIME) in the Inbox by sequence number.
    CkStringBuilder sbMime = new CkStringBuilder();
    success = imap.FetchSingleAsMimeSb(1,false,sbMime);
    if (success != true) {
        System.out.println(imap.lastErrorText());
        return;
        }

    // Load it into a MIME object and check to see if it is signed
    CkMime mime = new CkMime();
    mime.LoadMimeSb(sbMime);
    boolean alreadySavedParts = false;
    if (mime.ContainsSignedParts() == true) {

        // This will save the .p7s and other parts...
        CkStringArray sa = mime.ExtractPartsToFiles("qa_output");
        if (mime.get_LastMethodSuccess() == true) {
            int numFiles = sa.get_Count();
            int i = 0;
            while (i < numFiles) {
                System.out.println("Created: " + sa.getString(i));
                i = i+1;
                }

            alreadySavedParts = true;
            }

        }

    // Load the MIME into an Email object.  This unwraps the security layers and verifies signatures.
    CkEmail email = new CkEmail();
    email.SetFromMimeSb(sbMime);

    if (email.get_ReceivedSigned() == true) {

        System.out.println("This email was signed.");

        // Check to see if the signatures were verified.
        if (email.get_SignaturesValid() == true) {
            System.out.println("Digital signature(s) verified.");

            System.out.println("Signer: " + email.signedBy());

            // The certificate used for signing may be obtained
            // by calling email.GetSignedByCert.
            CkCert cert = email.GetSignedByCert();
            if (email.get_LastMethodSuccess() != true) {
                System.out.println("Failed to get signing certificate object.");
                }
            else {
                System.out.println("Signing cert: " + cert.subjectCN());

                }

            }

        }
    else {
        System.out.println("Digital signature verification failed.");
        }

    if (alreadySavedParts != true) {
        email.SaveAllAttachments("qa_output");
        }
  }
}