(Delphi ActiveX) 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.

Chilkat for Delphi Downloads Chilkat ActiveX DLL for Delphi Chilkat non-ActiveX DLL for Delphi * The examples here use the ActiveX DLL.

uses
    Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
    Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, Chilkat_TLB;

...

procedure TForm1.Button1Click(Sender: TObject);
var
socket: TChilkatSocket;
maxWaitMs: Integer;
useTls: Integer;
success: Integer;
bigEndian: Integer;
dt: TCkDateTime;
bLocalTime: Integer;
fac: TCkFileAccess;
jsonKey: WideString;
gAuth: TChilkatAuthGoogle;
unixTime: Integer;
tlsSock: TChilkatSocket;
success: Integer;

begin
// 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
socket := TChilkatSocket.Create(Self);

// Connect to an NIST time server and read the current date/time
maxWaitMs := 8000;
useTls := 0;
success := socket.Connect('time-c.nist.gov',37,useTls,maxWaitMs);
if (success <> 1) then
  begin
    Memo1.Lines.Add(socket.LastErrorText);
    Exit;
  end;

// 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
// 1 or 0 to indicate success.  If successful, the integer
// is obtained via the ReceivedInt property.
bigEndian := 1;
success := socket.ReceiveInt32(bigEndian);
if (success <> 1) then
  begin
    Memo1.Lines.Add(socket.LastErrorText);
    Exit;
  end;

dt := TCkDateTime.Create(Self);
dt.SetFromNtpTime(socket.ReceivedInt);

// Show the current local date/time
bLocalTime := 1;
Memo1.Lines.Add('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.
fac := TCkFileAccess.Create(Self);
jsonKey := fac.ReadEntireTextFile('qa_data/googleApi/ChilkatTest-ab2ecd52ef98.json','utf-8');
if (fac.LastMethodSuccess <> 1) then
  begin
    Memo1.Lines.Add(fac.LastErrorText);
    Exit;
  end;

// 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"
// 	}

gAuth := TChilkatAuthGoogle.Create(Self);
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.
unixTime := dt.GetAsUnixTime(0);
Memo1.Lines.Add('unixTime = ' + IntToStr(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.
tlsSock := TChilkatSocket.Create(Self);
success := tlsSock.Connect('www.googleapis.com',443,1,5000);
if (success <> 1) then
  begin
    Memo1.Lines.Add(tlsSock.LastErrorText);
    Exit;
  end;

// Send the request to obtain the access token.
success := gAuth.ObtainAccessToken(tlsSock.ControlInterface);
if (success <> 1) then
  begin
    Memo1.Lines.Add(gAuth.LastErrorText);
    Exit;
  end;

// Examine the access token:
Memo1.Lines.Add('Access Token: ' + gAuth.AccessToken);
end;