(Delphi ActiveX) Validate a JWS Using ECDSA P-256 SHA-256

Validates a JSON Web Signature (JWS) that uses ECDSA P-256 SHA-256

Note: This example requires Chilkat v9.5.0.66 or greater.

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
sbPubKey: TChilkatStringBuilder;
pubKey: TPublicKey;
success: Integer;
jws: TChilkatJws;
signatureIndex: Integer;
sbJws: TChilkatStringBuilder;
v: Integer;
joseHeader: IChilkatJsonObject;

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

// Note: This example requires Chilkat v9.5.0.66 or greater.

// This example takes a JSON signature in compact serialization format,
// and uses an ECDSA public key to validate and recover the protected header and payload.

// We only need a public key for signature validation.  This is the ECDSA public key
// that is used:

//      {"kty":"EC", 
//       "crv":"P-256", 
//       "x":"f83OJ3D2xF1Bg8vub9tLe1gHMzV76e8Tus9uPHvRVEU", 
//       "y":"x_FEzRu9m36HLN_tue659LNpXW6pCyStikYjKIWI5a0" 
//      } 

sbPubKey := TChilkatStringBuilder.Create(Self);
sbPubKey.Append('{"kty":"EC",');
sbPubKey.Append('"crv":"P-256",');
sbPubKey.Append('"x":"f83OJ3D2xF1Bg8vub9tLe1gHMzV76e8Tus9uPHvRVEU",');
sbPubKey.Append('"y":"x_FEzRu9m36HLN_tue659LNpXW6pCyStikYjKIWI5a0"');
sbPubKey.Append('}');

pubKey := TPublicKey.Create(Self);
success := pubKey.LoadFromString(sbPubKey.GetAsString());
if (success <> 1) then
  begin
    Memo1.Lines.Add(pubKey.LastErrorText);
    Exit;
  end;

jws := TChilkatJws.Create(Self);

// Set the ECC public key:
signatureIndex := 0;
jws.SetPublicKey(signatureIndex,pubKey.ControlInterface);

// Load the JWS.
sbJws := TChilkatStringBuilder.Create(Self);
sbJws.Append('eyJhbGciOiJFUzI1NiJ9');
sbJws.Append('.');
sbJws.Append('eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFt');
sbJws.Append('cGxlLmNvbS9pc19yb290Ijp0cnVlfQ');
sbJws.Append('.');
sbJws.Append('DtEhU3ljbEg8L38VWAfUAqOyKAM6-Xx-F4GawxaepmXFCgfTjDxw5djxLa8ISlSA');
sbJws.Append('pmWQxfKTUJqPP3-Kg6NU1Q');

success := jws.LoadJwsSb(sbJws.ControlInterface);
if (success <> 1) then
  begin
    Memo1.Lines.Add(jws.LastErrorText);
    Exit;
  end;

// Validate the 1st (and only) signature at index 0..
v := jws.Validate(signatureIndex);
if (v < 0) then
  begin
    // Perhaps Chilkat was not unlocked or the trial expired..
    Memo1.Lines.Add('Method call failed for some other reason.');
    Memo1.Lines.Add(jws.LastErrorText);
    Exit;
  end;
if (v = 0) then
  begin
    Memo1.Lines.Add('Invalid signature.  The ECC key was incorrect, the JWS was invalid, or both.');
    Exit;
  end;

// If we get here, the signature was validated..
Memo1.Lines.Add('Signature validated.');
Memo1.Lines.Add('--');

// Recover the original content:
Memo1.Lines.Add('Recovered content:');
Memo1.Lines.Add(jws.GetPayload('utf-8'));
Memo1.Lines.Add('--');

// Examine the protected header:
joseHeader := jws.GetProtectedHeader(signatureIndex);
if (jws.LastMethodSuccess <> 1) then
  begin
    Memo1.Lines.Add('No protected header found at the given index.');
    Exit;
  end;
joseHeader.EmitCompact := 0;

Memo1.Lines.Add('Protected (JOSE) header:');
Memo1.Lines.Add(joseHeader.Emit());

// Output:

// 	Signature validated.
// 	--
// 	Recovered content:
// 	{"iss":"joe",
// 	 "exp":1300819380,
// 	 "http://example.com/is_root":true}
// 	--
// 	Protected (JOSE) header:
// 	{ 
// 	  "alg": "ES256"
// 	}
end;