(Swift 3,4,5...) 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 Downloads for the Swift Programming Language MAC OS X (Cocoa) Objective-C/Swift Libs iOS Objective-C/Swift Libs

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

    let imap = CkoImap()!

    // Connect to an IMAP server.
    // Use TLS
    imap.ssl = true
    imap.port = 993
    var success: Bool = imap.connect("imap.someMailServer.com")
    if success != true {
        print("\(imap.lastErrorText!)")
        return
    }

    success = imap.login("myLogin", password: "myPassword")
    if success != true {
        print("\(imap.lastErrorText!)")
        return
    }

    // Select an IMAP mailbox
    success = imap.selectMailbox("Inbox")
    if success != true {
        print("\(imap.lastErrorText!)")
        return
    }

    // Download the 1st email (as MIME) in the Inbox by sequence number.
    let sbMime = CkoStringBuilder()!
    success = imap.fetchSingle(asMimeSb: 1, bUid: false, sbMime: sbMime)
    if success != true {
        print("\(imap.lastErrorText!)")
        return
    }

    // Load it into a MIME object and check to see if it is signed
    let mime = CkoMime()!
    mime.loadSb(sbMime)
    var alreadySavedParts: Bool = false
    if mime.containsSignedParts() == true {

        // This will save the .p7s and other parts...
        var sa: CkoStringArray? = mime.extractParts(toFiles: "qa_output")
        if mime.lastMethodSuccess == true {
            var numFiles: Int = sa!.count.intValue
            var i: Int = 0
            while i < numFiles {
                print("Created: \(sa!.getString(i)!)")
                i = i + 1
            }

            sa = nil
            alreadySavedParts = true
        }

    }

    // Load the MIME into an Email object.  This unwraps the security layers and verifies signatures.
    let email = CkoEmail()!
    email.setFromMimeSb(sbMime)

    if email.receivedSigned == true {

        print("This email was signed.")

        // Check to see if the signatures were verified.
        if email.signaturesValid == true {
            print("Digital signature(s) verified.")

            print("Signer: \(email.signedBy!)")

            // The certificate used for signing may be obtained
            // by calling email.GetSignedByCert.
            var cert: CkoCert? = email.getSignedByCert()
            if email.lastMethodSuccess != true {
                print("Failed to get signing certificate object.")
            }
            else {
                print("Signing cert: \(cert!.subjectCN!)")
                cert = nil
            }

        }

    }
    else {
        print("Digital signature verification failed.")
    }

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


}