(Node.js) OAuth2 for a GMail using a JSON Service Account Key

Demonstrates how get an OAuth2 access token for GMail (Google Service Account) using a JSON private key.

After the access token is obtained, it may be used to send email. When the access token expires, a new access token needs to be obtained (using this same procedure).

Note: This is for OAuth2 using Google Service account keys.

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

var os = require('os');
if (os.platform() == 'win32') {  
    if (os.arch() == 'ia32') {
        var chilkat = require('@chilkat/ck-node21-win-ia32');
    } else {
        var chilkat = require('@chilkat/ck-node21-win64'); 
    }
} else if (os.platform() == 'linux') {
    if (os.arch() == 'arm') {
        var chilkat = require('@chilkat/ck-node21-arm');
    } else if (os.arch() == 'x86') {
        var chilkat = require('@chilkat/ck-node21-linux32');
    } else {
        var chilkat = require('@chilkat/ck-node21-linux64');
    }
} else if (os.platform() == 'darwin') {
    if (os.arch() == 'arm64') {
        var chilkat = require('@chilkat/ck-node21-mac-m1');
    } else {
        var chilkat = require('@chilkat/ck-node21-macosx');
    }
}

function chilkatExample() {

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

    // First load the JSON key into a string.
    var fac = new chilkat.FileAccess();
    var jsonKey = fac.ReadEntireTextFile("qa_data/googleApi/ChilkatTest-ab2ecd52ef98.json","utf-8");
    if (fac.LastMethodSuccess !== true) {
        console.log(fac.LastErrorText);
        return;
    }

    // A JSON private key should look like this:

    // 	{
    // 	  "type": "service_account",
    // 	  "project_id": "chilkattest-1350",
    // 	  "private_key_id": "fa2e36ee26986eab628b59868af8bec1d1c64c38",
    // 	  "private_key": "-----BEGIN PRIVATE KEY-----\nMIIEvgIjFa...28N64N2n1E4FYzBZjSdy\n-----END PRIVATE KEY-----\n",
    // 	  "client_email": "598922945226-00rb0ppfg0sndajo6bhvd4v17jtj2d3a@developer.gserviceaccount.com",
    // 	  "client_id": "598922945226-00rb0ppfg0snd9jo7bhvd4v17jtj2d3a.apps.googleusercontent.com",
    // 	  "auth_uri": "https://accounts.google.com/o/oauth2/auth",
    // 	  "token_uri": "https://accounts.google.com/o/oauth2/token",
    // 	  "auth_provider_x509_cert_url": "https://www.googleapis.com/oauth2/v1/certs",
    // 	  "client_x509_cert_url": "https://www.googleapis.com/robot/v1/metadata/x509/598922945226-00rb0ppfg0sndajo6bhvd4v17jtj2d3a%40developer.gserviceaccount.com"
    // 	}

    var gAuth = new chilkat.AuthGoogle();
    gAuth.JsonKey = jsonKey;

    // Choose a scope.
    gAuth.Scope = "https://mail.google.com/";

    // Request an access token that is valid for this many seconds.
    gAuth.ExpireNumSeconds = 3600;

    // If the application is requesting delegated access:
    // The email address of the user for which the application is requesting delegated access,
    // then set the email address here. (Otherwise leave it empty.)
    gAuth.SubEmailAddress = "";

    // Connect to www.googleapis.com using TLS (TLS 1.2 is the default.)
    // The Chilkat socket object is used so that the connection can be established
    // through proxies or an SSH tunnel if desired.
    var tlsSock = new chilkat.Socket();
    var success = tlsSock.Connect("www.googleapis.com",443,true,5000);
    if (success !== true) {
        console.log(tlsSock.LastErrorText);
        return;
    }

    // Send the request to obtain the access token.
    success = gAuth.ObtainAccessToken(tlsSock);
    if (success !== true) {
        console.log(gAuth.LastErrorText);
        return;
    }

    // Examine the access token:
    console.log("Access Token: " + gAuth.AccessToken);

    // Now that we have the access token, it may be used to send email
    // while it remains valid.  Once the access token expires, a new access token 
    // should be obtained using the same code as above.

    // -----------------------------------------------------------------------
    var mailman = new chilkat.MailMan();

    // Set the properties for the GMail SMTP server:
    mailman.SmtpHost = "smtp.gmail.com";
    mailman.SmtpPort = 587;
    mailman.StartTLS = true;

    mailman.SmtpUsername = "YOUR_GOOGLE_APPS_USER_EMAIL_ADDRESS";
    mailman.OAuth2AccessToken = gAuth.AccessToken;

    // Create a new email object
    var email = new chilkat.Email();

    email.Subject = "This is a test";
    email.Body = "This is a test";
    email.From = "YOUR NAME <YOUR_GOOGLE_APPS_USER_EMAIL_ADDRESS>";
    success = email.AddTo("Chilkat Admin","admin@chilkatsoft.com");
    // To add more recipients, call AddTo, AddCC, or AddBcc once per recipient.

    // Call SendEmail to connect to the SMTP server and send.
    // The connection (i.e. session) to the SMTP server remains
    // open so that subsequent SendEmail calls may use the
    // same connection.  
    success = mailman.SendEmail(email);
    if (success !== true) {
        console.log(mailman.LastErrorText);
        return;
    }

    // You may close the connection here.  If the connection is kept open, 
    // the next call to mailman.SendEmail will continue using the already-established connection
    // (and automatically re-connect if needed).
    success = mailman.CloseSmtpConnection();
    if (success !== true) {
        console.log("Connection to SMTP server not closed cleanly.");
    }

    console.log("Email Sent via GMail using an OAuth2 Service Account Key.");

}

chilkatExample();