(Node.js) 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).

Install Chilkat for Node.js and Electron using npm at Chilkat npm packages for Node.js Chilkat npm packages for Electron on Windows, Linux, MacOS

var os = require('os');
if (os.platform() == 'win32') {  
  var chilkat = require('@chilkat/ck-node23-win64'); 
} else if (os.platform() == 'linux') {
    if (os.arch() == 'arm') {
        var chilkat = require('@chilkat/ck-node23-linux-arm');
    } else if (os.arch() == 'arm64') {
        var chilkat = require('@chilkat/ck-node23-linux-arm64');
    } else {
        var chilkat = require('@chilkat/ck-node23-linux-x64');
    }
} else if (os.platform() == 'darwin') {
  var chilkat = require('@chilkat/ck-node23-mac-universal');
}

function chilkatExample() {

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

    var imap = new chilkat.Imap();

    // Connect to an IMAP server.
    // Use TLS
    imap.Ssl = true;
    imap.Port = 993;
    var success = imap.Connect("imap.someMailServer.com");
    if (success !== true) {
        console.log(imap.LastErrorText);
        return;
    }

    success = imap.Login("myLogin","myPassword");
    if (success !== true) {
        console.log(imap.LastErrorText);
        return;
    }

    // Select an IMAP mailbox
    success = imap.SelectMailbox("Inbox");
    if (success !== true) {
        console.log(imap.LastErrorText);
        return;
    }

    // Download the 1st email (as MIME) in the Inbox by sequence number.
    var sbMime = new chilkat.StringBuilder();
    success = imap.FetchSingleAsMimeSb(1,false,sbMime);
    if (success !== true) {
        console.log(imap.LastErrorText);
        return;
    }

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

        // This will save the .p7s and other parts...
        // sa: StringArray
        var sa = mime.ExtractPartsToFiles("qa_output");
        if (mime.LastMethodSuccess == true) {
            var numFiles = sa.Count;
            var i = 0;
            while (i < numFiles) {
                console.log("Created: " + sa.GetString(i));
                i = i+1;
            }

            alreadySavedParts = true;
        }

    }

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

    if (email.ReceivedSigned == true) {

        console.log("This email was signed.");

        // Check to see if the signatures were verified.
        if (email.SignaturesValid == true) {
            console.log("Digital signature(s) verified.");

            console.log("Signer: " + email.SignedBy);

            // The certificate used for signing may be obtained
            // by calling email.GetSignedByCert.
            // cert: Cert
            var cert = email.GetSignedByCert();
            if (email.LastMethodSuccess !== true) {
                console.log("Failed to get signing certificate object.");
            }
            else {
                console.log("Signing cert: " + cert.SubjectCN);

            }

        }

    }
    else {
        console.log("Digital signature verification failed.");
    }

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


}

chilkatExample();