Lazarus Pascal

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. Lazarus Pascal

program ChilkatDemo;

// Demonstrates using the Chilkat Pascal wrapper via the C bridge DLL.
// Builds as a console application under Lazarus (FPC) or Delphi.

{$IFDEF FPC}
  {$MODE DELPHI}
{$ENDIF}
{$APPTYPE CONSOLE}

uses
  {$IFDEF UNIX}
  cthreads,
  {$ENDIF}
  SysUtils,
  CkDllLoader,
  Chilkat.FileAccess,
  Chilkat.AuthGoogle,
  Chilkat.CkDateTime,
  Chilkat.Socket;

// ---------------------------------------------------------------------------

procedure RunDemo;
var
  success: Boolean;
  socket: TSocket;
  maxWaitMs: Integer;
  useTls: Boolean;
  bigEndian: Boolean;
  dt: TCkDateTime;
  bLocalTime: Boolean;
  fac: TFileAccess;
  jsonKey: string;
  gAuth: TAuthGoogle;
  unixTime: Integer;
  tlsSock: TSocket;

begin
  success := False;

  //  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 := TSocket.Create;

  //  Connect to an NIST time server and read the current date/time
  maxWaitMs := 8000;
  useTls := False;
  success := socket.Connect('time-c.nist.gov',37,useTls,maxWaitMs);
  if (success <> True) then
    begin
      WriteLn(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
  //  True or False to indicate success.  If successful, the integer
  //  is obtained via the ReceivedInt property.
  bigEndian := True;
  success := socket.ReceiveInt32(bigEndian);
  if (success <> True) then
    begin
      WriteLn(socket.LastErrorText);
      Exit;
    end;

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

  //  Show the current local date/time
  bLocalTime := True;
  WriteLn('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 := TFileAccess.Create;
  jsonKey := fac.ReadEntireTextFile('qa_data/googleApi/ChilkatTest-ab2ecd52ef98.json','utf-8');
  if (fac.LastMethodSuccess <> True) then
    begin
      WriteLn(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 := TAuthGoogle.Create;
  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(False);
  WriteLn('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.
  tlsSock := TSocket.Create;
  success := tlsSock.Connect('www.googleapis.com',443,True,5000);
  if (success <> True) then
    begin
      WriteLn(tlsSock.LastErrorText);
      Exit;
    end;

  //  Send the request to obtain the access token.
  success := gAuth.ObtainAccessToken(tlsSock);
  if (success <> True) then
    begin
      WriteLn(gAuth.LastErrorText);
      Exit;
    end;

  //  Examine the access token:
  WriteLn('Access Token: ' + gAuth.AccessToken);


  socket.Free;
  dt.Free;
  fac.Free;
  gAuth.Free;
  tlsSock.Free;

end;

// ---------------------------------------------------------------------------

begin

  try
    RunDemo;
  except
    on E: Exception do
      WriteLn('Unhandled exception: ', E.ClassName, ': ', E.Message);
  end;

  WriteLn;
  {$IFDEF MSWINDOWS}
  WriteLn('Press Enter to exit...');
  ReadLn;
  {$ENDIF}
end.