(Delphi ActiveX) Verify a JWT Created by the Amazon Cognito Service

Demonstrates how to verify a JWT created by the Amazon Cognito Service.

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
http: TChilkatHttp;
sbJsonKeys: TChilkatStringBuilder;
success: Integer;
jsonKeys: TChilkatJsonObject;
jsonKey1: IChilkatJsonObject;
pubKey1: TPublicKey;
jwt: TChilkatJwt;
token: WideString;
sigVerified: Integer;
leeway: Integer;
bTimeValid: Integer;
payload: WideString;
json: TChilkatJsonObject;
joseHeader: WideString;

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

// The public keys for this example are at https://cognito-idp.us-east-2.amazonaws.com/us-east-2_******/.well-known/jwks.json
// Let's get them:

http := TChilkatHttp.Create(Self);
sbJsonKeys := TChilkatStringBuilder.Create(Self);
success := http.QuickGetSb('https://cognito-idp.us-east-2.amazonaws.com/us-east-2_******/.well-known/jwks.json',sbJsonKeys.ControlInterface);
if (success = 0) then
  begin
    Memo1.Lines.Add(http.LastErrorText);
    Exit;
  end;

jsonKeys := TChilkatJsonObject.Create(Self);
jsonKeys.LoadSb(sbJsonKeys.ControlInterface);
jsonKeys.EmitCompact := 0;
Memo1.Lines.Add(jsonKeys.Emit());

// Here are the keys:

// {
//   "keys": [
//     {
//       "alg": "RS256",
//       "e": "AQAB",
//       "kid": "1A/L5Fsb2EsEwxy5E0cmCMS1BnMe6Jl6NXiMig4iNwU=",
//       "kty": "RSA",
//       "n": "y0w7BJrIJYi ... jKG27z2P3OKw",
//       "use": "sig"
//     },
//     {
//       "alg": "RS256",
//       "e": "AQAB",
//       "kid": "mos6VTJnvDwurY3ghJg6IAPUq+dMwl6CL/iThzJOkzg=",
//       "kty": "RSA",
//       "n": "qbIEH-7tg6yrT ... 3Fj94ooTd0w",
//       "use": "sig"
//     }
//   ]
// }

// Try the 1st key.
jsonKey1 := jsonKeys.ObjectOf('keys[0]');
if (jsonKeys.LastMethodSuccess = 0) then
  begin
    Memo1.Lines.Add('Did not get the 1st JSON public key.');
    Exit;
  end;

pubKey1 := TPublicKey.Create(Self);
success := pubKey1.LoadFromString(jsonKey1.Emit());
if (success = 0) then
  begin
    Memo1.Lines.Add(pubKey1.LastErrorText);
    Exit;
  end;

Memo1.Lines.Add('Success');

jwt := TChilkatJwt.Create(Self);

// I did not include the an actual AWS Cognito token here because our test sample used customer-provided data..
token := 'eyJ..asXg';

// First verify the signature.
sigVerified := jwt.VerifyJwtPk(token,pubKey1.ControlInterface);
Memo1.Lines.Add('verified: ' + IntToStr(Ord(sigVerified)));

// Let's see if the time constraints, if any, are valid.
// The above JWT was created on the afternoon of 16-May-2016, with an expiration of 1 hour.
// If the current system time is before the "nbf" time, or after the "exp" time,
// then IsTimeValid will return false/0.
// Also, we'll allow a leeway of 60 seconds to account for any clock skew.
// Note: If the token has no "nbf" or "exp" claim fields, then IsTimeValid is always true.
leeway := 60;
bTimeValid := jwt.IsTimeValid(token,leeway);
Memo1.Lines.Add('time constraints valid: ' + IntToStr(Ord(bTimeValid)));

// Now let's recover the original claims JSON (the payload).
payload := jwt.GetPayload(token);
// The payload will likely be in compact form:
Memo1.Lines.Add(payload);

// We can format for human viewing by loading it into Chilkat's JSON object
// and emit.
json := TChilkatJsonObject.Create(Self);
success := json.Load(payload);
json.EmitCompact := 0;
Memo1.Lines.Add(json.Emit());

// We can recover the original JOSE header in the same way:
joseHeader := jwt.GetHeader(token);
// The payload will likely be in compact form:
Memo1.Lines.Add(joseHeader);

// We can format for human viewing by loading it into Chilkat's JSON object
// and emit.
success := json.Load(joseHeader);
json.EmitCompact := 0;
Memo1.Lines.Add(json.Emit());
end;