Dart

Get Google API Access Token using JSON Private Key using NIST Time Server Date/Time

Demonstrates how to get a Google API access token using a JSON service account private key, using the NIST time server date/time rather than the local system date/time. Dart

import 'package:chilkat/chilkat.dart';

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

  // First, let's get the current date/time from time-c.nist.gov
  final socket = CkSocket();

  // Connect to an NIST time server and read the current date/time
  var maxWaitMs = 8000;
  final useTls = false;
  try {
    socket.connect('time-c.nist.gov', 37, useTls, maxWaitMs);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // The time server will send a big-endian 32-bit integer representing
  // the number of seconds since since 00:00 (midnight) 1 January 1900 GMT.
  // The ReceiveInt32 method will receive a 4-byte integer, but returns
  // true or false to indicate success.  If successful, the integer
  // is obtained via the ReceivedInt property.
  final bigEndian = true;
  try {
    socket.receiveInt32(bigEndian);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  final dt = CkDateTime();
  dt.setFromNtpTime(socket.receivedInt);

  // Show the current local date/time
  final bLocalTime = true;
  print('Current local date/time: ${dt.getAsRfc822(bLocalTime)}');

  maxWaitMs = 10;
  socket.close(maxWaitMs);

  // ------------------------------------------------------------------------
  // OK, we have the current date/time.  We'll use it to set the IAT property
  // in the code below.

  // First load the JSON key into a string.
  final fac = CkFileAccess();
  final String jsonKey;
  try {
    jsonKey = fac.readEntireTextFile('qa_data/googleApi/ChilkatTest-ab2ecd52ef98.json', 'utf-8');
  } on ChilkatException catch (e) {
    print(e.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"
  // 	}

  final gAuth = CkAuthGoogle();
  gAuth.jsonKey = jsonKey;

  // Choose a scope.
  gAuth.scope = 'https://www.googleapis.com/auth/cloud-platform';

  // 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 = '';

  // ------------------------------------------------------------------------
  // Set the IAT using the date/time from the NIST time server.
  final unixTime = dt.getAsUnixTime(false);
  print('unixTime = $unixTime');
  gAuth.iat = unixTime;

  // 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.
  final tlsSock = CkSocket();
  try {
    tlsSock.connect('www.googleapis.com', 443, true, 5000);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // Send the request to obtain the access token.
  try {
    gAuth.obtainAccessToken(tlsSock);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // Examine the access token:
  print('Access Token: ${gAuth.accessToken}');
}