(C++) IMAP Download and Verify Signed MIME

Downloads the original MIME of a digitally signed email and saves the .p7s signature along with other MIME parts. It then imports the email into a Chilkat email object to unwrap the S/MIME and verify the signature, and subsequently saves the attachments if they haven't been saved already.

Note: This example requires Chilkat v11.0.0 or greater.

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#include <CkImap.h>
#include <CkStringBuilder.h>
#include <CkMime.h>
#include <CkStringTable.h>
#include <CkEmail.h>
#include <CkCert.h>

void ChilkatSample(void)
    {
    bool success = false;

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

    CkImap imap;

    // Connect to an IMAP server.
    // Use TLS
    imap.put_Ssl(true);
    imap.put_Port(993);
    success = imap.Connect("imap.example.com");
    if (success == false) {
        std::cout << imap.lastErrorText() << "\r\n";
        return;
    }

    success = imap.Login("myLogin","myPassword");
    if (success == false) {
        std::cout << imap.lastErrorText() << "\r\n";
        return;
    }

    // Select an IMAP mailbox
    success = imap.SelectMailbox("Inbox");
    if (success == false) {
        std::cout << imap.lastErrorText() << "\r\n";
        return;
    }

    // Download the 1st email (as MIME) in the Inbox by sequence number.
    CkStringBuilder sbMime;
    success = imap.FetchSingleAsMimeSb(1,false,sbMime);
    if (success == false) {
        std::cout << imap.lastErrorText() << "\r\n";
        return;
    }

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

        // This will save the .p7s and other parts...
        CkStringTable st;
        success = mime.PartsToFiles("c:/temp/qa_output",st);
        if (success == true) {
            int numFiles = st.get_Count();
            int i = 0;
            while (i < numFiles) {
                std::cout << "Created: " << st.stringAt(i) << "\r\n";
                i = i + 1;
            }

            alreadySavedParts = true;
        }

    }

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

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

        std::cout << "This email was signed." << "\r\n";

        // Check to see if the signatures were verified.
        if (email.get_SignaturesValid() == true) {
            std::cout << "Digital signature(s) verified." << "\r\n";

            std::cout << "Signer: " << email.signedBy() << "\r\n";

            // The certificate used for signing may be obtained
            // by calling email.GetSignedByCert.
            CkCert cert;
            success = email.LastSignerCert(i,cert);
            if (success == false) {
                std::cout << "Failed to get signing certificate object." << "\r\n";
            }
            else {
                std::cout << "Signing cert: " << cert.subjectCN() << "\r\n";
            }

        }

    }
    else {
        std::cout << "Digital signature verification failed." << "\r\n";
    }

    if (alreadySavedParts != true) {
        email.SaveAllAttachments("c:/temp/qa_output");
    }
    }