(Delphi DLL) 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 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, StringBuilder, Jws, PublicKey, JsonObject;

...

procedure TForm1.Button1Click(Sender: TObject);
var
sbPubKey: HCkStringBuilder;
pubKey: HCkPublicKey;
success: Boolean;
jws: HCkJws;
signatureIndex: Integer;
sbJws: HCkStringBuilder;
v: Integer;
joseHeader: HCkJsonObject;

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 := CkStringBuilder_Create();
CkStringBuilder_Append(sbPubKey,'{"kty":"EC",');
CkStringBuilder_Append(sbPubKey,'"crv":"P-256",');
CkStringBuilder_Append(sbPubKey,'"x":"f83OJ3D2xF1Bg8vub9tLe1gHMzV76e8Tus9uPHvRVEU",');
CkStringBuilder_Append(sbPubKey,'"y":"x_FEzRu9m36HLN_tue659LNpXW6pCyStikYjKIWI5a0"');
CkStringBuilder_Append(sbPubKey,'}');

pubKey := CkPublicKey_Create();
success := CkPublicKey_LoadFromString(pubKey,CkStringBuilder__getAsString(sbPubKey));
if (success <> True) then
  begin
    Memo1.Lines.Add(CkPublicKey__lastErrorText(pubKey));
    Exit;
  end;

jws := CkJws_Create();

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

// Load the JWS.
sbJws := CkStringBuilder_Create();
CkStringBuilder_Append(sbJws,'eyJhbGciOiJFUzI1NiJ9');
CkStringBuilder_Append(sbJws,'.');
CkStringBuilder_Append(sbJws,'eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFt');
CkStringBuilder_Append(sbJws,'cGxlLmNvbS9pc19yb290Ijp0cnVlfQ');
CkStringBuilder_Append(sbJws,'.');
CkStringBuilder_Append(sbJws,'DtEhU3ljbEg8L38VWAfUAqOyKAM6-Xx-F4GawxaepmXFCgfTjDxw5djxLa8ISlSA');
CkStringBuilder_Append(sbJws,'pmWQxfKTUJqPP3-Kg6NU1Q');

success := CkJws_LoadJwsSb(jws,sbJws);
if (success <> True) then
  begin
    Memo1.Lines.Add(CkJws__lastErrorText(jws));
    Exit;
  end;

// Validate the 1st (and only) signature at index 0..
v := CkJws_Validate(jws,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(CkJws__lastErrorText(jws));
    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(CkJws__getPayload(jws,'utf-8'));
Memo1.Lines.Add('--');

// Examine the protected header:
joseHeader := CkJws_GetProtectedHeader(jws,signatureIndex);
if (CkJws_getLastMethodSuccess(jws) <> True) then
  begin
    Memo1.Lines.Add('No protected header found at the given index.');
    Exit;
  end;
CkJsonObject_putEmitCompact(joseHeader,False);

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

// Output:

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

CkStringBuilder_Dispose(sbPubKey);
CkPublicKey_Dispose(pubKey);
CkJws_Dispose(jws);
CkStringBuilder_Dispose(sbJws);

end;