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

uses
    Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
    Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, FileAccess, AuthGoogle, CkDateTime, Socket;

...

procedure TForm1.Button1Click(Sender: TObject);
var
socket: HCkSocket;
maxWaitMs: Integer;
useTls: Boolean;
success: Boolean;
bigEndian: Boolean;
dt: HCkDateTime;
bLocalTime: Boolean;
fac: HCkFileAccess;
jsonKey: PWideChar;
gAuth: HCkAuthGoogle;
unixTime: Integer;
tlsSock: HCkSocket;
success: Boolean;

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 := CkSocket_Create();

// Connect to an NIST time server and read the current date/time
maxWaitMs := 8000;
useTls := False;
success := CkSocket_Connect(socket,'time-c.nist.gov',37,useTls,maxWaitMs);
if (success <> True) then
  begin
    Memo1.Lines.Add(CkSocket__lastErrorText(socket));
    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 := CkSocket_ReceiveInt32(socket,bigEndian);
if (success <> True) then
  begin
    Memo1.Lines.Add(CkSocket__lastErrorText(socket));
    Exit;
  end;

dt := CkDateTime_Create();
CkDateTime_SetFromNtpTime(dt,CkSocket_getReceivedInt(socket));

// Show the current local date/time
bLocalTime := True;
Memo1.Lines.Add('Current local date/time: ' + CkDateTime__getAsRfc822(dt,bLocalTime));

maxWaitMs := 10;
CkSocket_Close(socket,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 := CkFileAccess_Create();
jsonKey := CkFileAccess__readEntireTextFile(fac,'qa_data/googleApi/ChilkatTest-ab2ecd52ef98.json','utf-8');
if (CkFileAccess_getLastMethodSuccess(fac) <> True) then
  begin
    Memo1.Lines.Add(CkFileAccess__lastErrorText(fac));
    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 := CkAuthGoogle_Create();
CkAuthGoogle_putJsonKey(gAuth,jsonKey);

// Choose a scope.
CkAuthGoogle_putScope(gAuth,'https://www.googleapis.com/auth/cloud-platform');

// Request an access token that is valid for this many seconds.
CkAuthGoogle_putExpireNumSeconds(gAuth,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.)
CkAuthGoogle_putSubEmailAddress(gAuth,'');

// ------------------------------------------------------------------------
// Set the IAT using the date/time from the NIST time server.
unixTime := CkDateTime_GetAsUnixTime(dt,False);
Memo1.Lines.Add('unixTime = ' + IntToStr(unixTime));
CkAuthGoogle_putIat(gAuth,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 := CkSocket_Create();
success := CkSocket_Connect(tlsSock,'www.googleapis.com',443,True,5000);
if (success <> True) then
  begin
    Memo1.Lines.Add(CkSocket__lastErrorText(tlsSock));
    Exit;
  end;

// Send the request to obtain the access token.
success := CkAuthGoogle_ObtainAccessToken(gAuth,tlsSock);
if (success <> True) then
  begin
    Memo1.Lines.Add(CkAuthGoogle__lastErrorText(gAuth));
    Exit;
  end;

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

CkSocket_Dispose(socket);
CkDateTime_Dispose(dt);
CkFileAccess_Dispose(fac);
CkAuthGoogle_Dispose(gAuth);
CkSocket_Dispose(tlsSock);

end;