Google OAuth2 API Refresh Tokens

Question

I'm using the google-auth-library-nodejs library to integrate into a number of GMail accounts, to get lists of emails.

My process flow is simple:

1) Try to authorize the client, using this function:

function _authorise(mailBox, callback) {
  let auth = new googleAuth();

  let clientId = eval(`process.env.GMAIL_API_CLIENT_ID_${mailBox.toUpperCase()}`);
  let clientSecret = eval(`process.env.GMAIL_API_CLIENT_SECRET_${mailBox.toUpperCase()}`);
  let redirectUri = eval(`process.env.GMAIL_API_REDIRECT_URI_${mailBox.toUpperCase()}`);
  let tokenFile = process.env.GMAIL_API_TOKEN_PATH + mailBox.toLowerCase()+ process.env.GMAIL_API_TOKEN_BASE_FILE_NAME;

  let oauth2Client = new auth.OAuth2(clientId, clientSecret, redirectUri);
  fs.readFile(tokenFile, ((err, token) => {
    if (err) {
      _getNewToken(mailBox,oauth2Client,callback);
    } else {
      oauth2Client.credentials = JSON.parse(token);
      callback(oauth2Client);
    }
  }))
}

2) The method will check for existence of a token in a file. If the file is NOT found, the following functions will create the file:

function _getNewToken(mailBox, oauth2Client, callback) {
  var authUrl = oauth2Client.generateAuthUrl({
    access_type: 'offline',
    scope: process.env.GMAIL_API_SCOPES
  });
  console.log('To authorize this app, please use this url: ', authUrl);
  var rl = readline.createInterface({
    input: process.stdin,
    output: process.stdout
  });
  rl.question('Enter the code from that page here: ', ((code) => {
    rl.close();
    oauth2Client.getToken(code, function(err, token) {
      if (err) {
        console.log('Error while trying to retrieve access token', err);
        return;
      }
      oauth2Client.credentials = token;
      _storeToken(mailBox,token);
      callback(oauth2Client);
    });
  }));
}

function _storeToken(mailBox, token) {
  let tokenFile = process.env.GMAIL_API_TOKEN_PATH + mailBox.toLowerCase()+ process.env.GMAIL_API_TOKEN_BASE_FILE_NAME;
  fs.writeFile(tokenFile, JSON.stringify(token));
}

I am using https://www.googleapis.com/auth/gmail.readonly as the scopes.

Here's a sample of the file created:

{"access_token":"xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx","token_type":"Bearer","refresh_token":"xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx","expiry_date":1460509994081}

When processed, here's a sample of the auth object that is returned:

OAuth2Client {
  transporter: DefaultTransporter {},
  clientId_: 'xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx.apps.googleusercontent.com',
  clientSecret_: 'xxxxxxxxxxxxxxxxxxxxxxxx',
  redirectUri_: 'urn:ietf:wg:oauth:2.0:oob',
  opts: {},
  credentials: {
access_token: 'xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx',
     token_type: 'Bearer',
     refresh_token: 'xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx',
     expiry_date: 1460509994081
  }
}

If I delete the file, and go through the manual consent process, then the authentication works 100%, until the token expires. After this, I get the "Invalid Credentials" message.

My assumption is that once the token expires, that the refresh token will be used to auto recreate the access token. Am I missing something?

Answer 1

Here is the updated solution to get Access Token with Refresh Token:

const { google } = require("googleapis");
const OAuth2 = google.auth.OAuth2;

const oauth2Client = new OAuth2(
  "xxxxxxxxx.apps.googleusercontent.com", // ClientID
  "xxxxxxx", // Client Secret
  "https://developers.google.com/oauthplayground" // Redirect URL
);

oauth2Client.setCredentials({
  refresh_token:
    "xxxxxxxx"
});

const accessToken = oauth2Client.getAccessToken();

Answer 2

Okay, so I have discovered the getAccessToken method, which will check the access_token, and use it, unless it has expired, in which case it will use the refresh_token to generate a new access_token.