Lazarus Pascal

Get OAuth 2.0 Access Token using G_SvcOauthAccessToken2

Obtains an OAUTH2 access token from the Google OAuth 2.0 Authorization Server using the G_SvcOauthAccessToken2 method. This is for Server to server applications using Google API's that need an access token. See https://developers.google.com/accounts/docs/OAuth2ServiceAccount 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.Http,
  Chilkat.Hashtable,
  Chilkat.Cert;

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

procedure RunDemo;
var
  success: Boolean;
  http: THttp;
  cert: TCert;
  claimParams: THashtable;
  numSec: Integer;
  accessToken: string;

begin
  success := False;

  //  This example assumes the Chilkat API to have been previously unlocked.
  //  See Global Unlock Sample for sample code.

  //  --------------------------------------------------------------------------------
  //  For a step-by-step guide for setting up your Google Workspace service account,
  //  see Setup Google Workspace Account for Sending SMTP GMail from a Service Account
  //  --------------------------------------------------------------------------------

  http := THttp.Create;

  //  When a service account (Client ID) is created at https://code.google.com/apis/console/
  //  Google will generate a P12 key.  This is a PKCS12 (PFX) file that you will download
  //  and save.  The password to access the contents of this file is "notasecret".
  //  NOTE: The Chilkat Pfx API provides the ability to load a PFX/P12 and re-save
  //  with a different password.

  //  Begin by loading the downloaded .p12 into a Chilkat certificate object:
  cert := TCert.Create;
  success := cert.LoadPfxFile('/myDir/API Project-1c43a291e2a1-notasecret.p12','notasecret');
  if (success <> True) then
    begin
      WriteLn(cert.LastErrorText);
      Exit;
    end;

  //  The next (and final) step is to request the access token.  Chilkat internally
  //  does all the work of forming the JWT header and JWT claim set, encoding and
  //  signing the JWT, and sending the access token request.
  //  The application need only provide the inputs: The iss, scope(s), sub, and the
  //  desired duration with a max of 3600 seconds (1 hour).
  //  
  //  Each of these inputs is defined as follows 
  //  (see https://developers.google.com/accounts/docs/OAuth2ServiceAccount
  //  iss: The email address of the service account.
  //  scope: A space-delimited list of the permissions that the application requests.
  //  sub: The email address of the user for which the application is requesting delegated access.
  //  numSec: The number of seconds for which the access token will be valid (max 3600).

  claimParams := THashtable.Create;

  //  The required claim parameters that must be provided by the application are
  //  the "iss" and "scope" params:
  success := claimParams.AddStr('iss','761326798069-r5mljlln1rd4lrbhg75efgigp36m78j5@developer.gserviceaccount.com');
  success := claimParams.AddStr('scope','https://mail.google.com/');

  //  The "sub" param is required if there is an email address, such as for a
  //  Google Apps domain—if you use Google Apps for Work, where the administrator of the Google Apps domain 
  //  can authorize an application to access user data on behalf of users in the Google Apps domain.
  //  
  //  Comment out this line if there is no such email address.
  success := claimParams.AddStr('sub','user@your-domain.com');

  //  The "aud" parameter is optional.  If not set, it defaults to the value shown here:
  success := claimParams.AddStr('aud','https://accounts.google.com/o/oauth2/token');

  numSec := 3600;

  accessToken := http.G_SvcOauthAccessToken2(claimParams,numSec,cert);
  if (http.LastMethodSuccess <> True) then
    begin
      WriteLn(http.LastErrorText);
    end
  else
    begin
      WriteLn('access token: ' + accessToken);
    end;


  http.Free;
  cert.Free;
  claimParams.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.