(Delphi ActiveX) Get Access Token using a Pre-Created JSON Web Token

Demonstrates how to get an access token using a pre-created JSON Web Token (JWT).

For more information, see https://developer.abnamro.com/get-started#headingFive

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
privkey: TPrivateKey;
success: Integer;
jwt: TChilkatJwt;
jsonHeader: TChilkatJsonObject;
jsonPayload: TChilkatJsonObject;
curDateTime: Integer;
jwtStr: WideString;
http: TChilkatHttp;
req: TChilkatHttpRequest;
resp: IChilkatHttpResponse;
json: TChilkatJsonObject;

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

// We're going to duplicate this CURL statement:
// curl -X POST https://api-sandbox.abnamro.com/v1/oauth/token \
// -H "Content-Type: application/x-www-form-urlencoded" \
// -H "API-Key: xxxxxx" \
// -d 'client_assertion_type=urn:ietf:params:oauth:client-assertion-type:jwt-bearer&grant_type=client_credentials&client_assertion=eyJhbGciOiJSUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiJ4eHh4eHgiLCJleHAiOiIxNDk5OTQ3NjY4IiwiaXNzIjoibWUiLCJhdWQiOiJodHRwczovL2F1dGgtc2FuZGJveC5hYm5hbXJvLmNvbS9vYXV0aC90b2tlbiJ9.jGwHKG_YjgKpR8NPpaLu6nJ97obeP2vcxg6fOWBKdJ0&scope=tikkie'

// Load our pre-creaed private key PEM file.
// Note: Please share your public key along with your app name and developer email id at api.support@nl.abnamro.com. 
// Token generation will not work unless public key is associated with your app.
privkey := TPrivateKey.Create(Self);

success := privkey.LoadPemFile('qa_data/pem/abnAmroPrivateKey.pem');
if (success = 0) then
  begin
    Memo1.Lines.Add(privkey.LastErrorText);
    Exit;
  end;

// Create the JWT.
jwt := TChilkatJwt.Create(Self);

// Create the header:
// {
//     "typ": "JWT",
//     "alg": "RS256"
// }
jsonHeader := TChilkatJsonObject.Create(Self);
jsonHeader.UpdateString('typ','JWT');
jsonHeader.UpdateString('alg','RS256');

// Create the payload:
// {
//     "nbf": 1499947668,
//     "exp": 1499948668,
//     "iss": "me",
//     "sub": "anApiKey",
//     "aud": "https://auth-sandbox.abnamro.com/oauth/token"
// }
jsonPayload := TChilkatJsonObject.Create(Self);

curDateTime := jwt.GenNumericDate(0);

// Set the "not process before" timestamp to now.
success := jsonPayload.AddIntAt(-1,'nbf',curDateTime);

// Set the timestamp defining an expiration time (end time) for the token
// to be now + 1 hour (3600 seconds)
success := jsonPayload.AddIntAt(-1,'exp',curDateTime + 3600);

jsonPayload.UpdateString('iss','me');
jsonPayload.UpdateString('sub','anApiKey');
jsonPayload.UpdateString('aud','https://auth-sandbox.abnamro.com/oauth/token');

// Produce the smallest possible JWT:
jwt.AutoCompact := 1;

jwtStr := jwt.CreateJwtPk(jsonHeader.Emit(),jsonPayload.Emit(),privkey.ControlInterface);
if (jwt.LastMethodSuccess <> 1) then
  begin
    Memo1.Lines.Add(jwt.LastErrorText);
    Exit;
  end;

http := TChilkatHttp.Create(Self);

req := TChilkatHttpRequest.Create(Self);
req.AddParam('client_assertion_type','urn:ietf:params:oauth:client-assertion-type:jwt-bearer');
req.AddParam('grant_type','client_credentials');
req.AddParam('client_assertion',jwtStr);
req.AddParam('scope','tikkie');

resp := http.PostUrlEncoded('https://api-sandbox.abnamro.com/v1/oauth/token',req.ControlInterface);
if (http.LastMethodSuccess = 0) then
  begin
    Memo1.Lines.Add(http.LastErrorText);
    Exit;
  end;

if (resp.StatusCode <> 200) then
  begin
    Memo1.Lines.Add(resp.BodyStr);

    Exit;
  end;

// Get the JSON result:
// {
//     "access_token": "{your access token}",
//     "expires_in": "{duration of validity in seconds}",
//     "scope": "{scope(s) for which the access token is valid}",
//     "token_type": "{it is always Bearer}"
// }
json := TChilkatJsonObject.Create(Self);
json.Load(resp.BodyStr);
Memo1.Lines.Add('access_token: ' + json.StringOf('access_token'));
Memo1.Lines.Add('token_type: ' + json.StringOf('token_type'));
Memo1.Lines.Add('expires_in: ' + json.StringOf('expires_in'));
Memo1.Lines.Add('scope: ' + json.StringOf('scope'));
end;