(.NET Core C#) 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.

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// 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
Chilkat.Socket socket = new Chilkat.Socket();

// Connect to an NIST time server and read the current date/time
int maxWaitMs = 8000;
bool useTls = false;
bool success = socket.Connect("time-c.nist.gov",37,useTls,maxWaitMs);
if (success != true) {
    Debug.WriteLine(socket.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.
bool bigEndian = true;
success = socket.ReceiveInt32(bigEndian);
if (success != true) {
    Debug.WriteLine(socket.LastErrorText);
    return;
}

Chilkat.CkDateTime dt = new Chilkat.CkDateTime();
dt.SetFromNtpTime(socket.ReceivedInt);

// Show the current local date/time
bool bLocalTime = true;
Debug.WriteLine("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.
Chilkat.FileAccess fac = new Chilkat.FileAccess();
string jsonKey = fac.ReadEntireTextFile("qa_data/googleApi/ChilkatTest-ab2ecd52ef98.json","utf-8");
if (fac.LastMethodSuccess != true) {
    Debug.WriteLine(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"
// 	}

Chilkat.AuthGoogle gAuth = new Chilkat.AuthGoogle();
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.
int unixTime = dt.GetAsUnixTime(false);
Debug.WriteLine("unixTime = " + Convert.ToString(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.
Chilkat.Socket tlsSock = new Chilkat.Socket();
bool success = tlsSock.Connect("www.googleapis.com",443,true,5000);
if (success != true) {
    Debug.WriteLine(tlsSock.LastErrorText);
    return;
}

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

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