(Delphi DLL) Verify JWT with EdDSA / Ed25519 Signature

Note: This example requires Chilkat v9.5.0.84 or greater.

Demonstrates how to verify a JWT that was signed using an Ed25519 private key.

This example verifies the EdDSA signature. It also does the following:

• Checks to see if the time constraints ("nbf" and "exp") are valid.
• Recovers the original JOSE header.
• Recovers the original data.

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, Jwt, PublicKey;

...

procedure TForm1.Button1Click(Sender: TObject);
var
jsonPubKey: PWideChar;
pubKey: HCkPublicKey;
success: Boolean;
jwt: HCkJwt;
token: PWideChar;
sigVerified: Boolean;
leeway: Integer;
bTimeValid: Boolean;
payload: PWideChar;
joseHeader: PWideChar;

begin
// Demonstrates how to verify a JWT with an EdDSA/Ed25519 Signature
// *** Requires Chilkat v9.5.0.84 or greater.

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

// Use this Ed25519 public key for verification

jsonPubKey := '{"kty": "OKP","alg": "EdDSA","crv": "Ed25519","x": "11qYAYKxCrfVS_7TyWQHOg7hcvPapiMlrwIaaPcHURo"}';

pubKey := CkPublicKey_Create();
success := CkPublicKey_LoadFromString(pubKey,jsonPubKey);
if (success = False) then
  begin
    Memo1.Lines.Add(CkPublicKey__lastErrorText(pubKey));
    Exit;
  end;

jwt := CkJwt_Create();
token := 'eyJhbGciOiJFZERTQSJ9.RXhhbXBsZSBvZiBFZDI1NTE5IHNpZ25pbmc.hgyY0il_MGCjP0JzlnLWG1PPOt7-09PGcvMg3AIbQR6dWbhijcNR4ki4iylGjg5BhVsPt9g7sVvpAr_MuM0KAg';

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

if (sigVerified = False) then
  begin
    Memo1.Lines.Add(CkJwt__lastErrorText(jwt));
    Exit;
  end;

// 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 := CkJwt_IsTimeValid(jwt,token,leeway);
Memo1.Lines.Add('time constraints valid: ' + IntToStr(Ord(bTimeValid)));

// Recover the original data (the payload).
payload := CkJwt__getPayload(jwt,token);
Memo1.Lines.Add(payload);

// Recover the original JOSE header in the same way:
joseHeader := CkJwt__getHeader(jwt,token);
Memo1.Lines.Add(joseHeader);

CkPublicKey_Dispose(pubKey);
CkJwt_Dispose(jwt);

end;