(Delphi DLL) Validate JWS with Multiple Signatures using the General JSON Serialization Format

Validates and recovers data and headers from a JSON Web Signature (JWS) containing 3 signatures.

Note: Chilkat supports all of the following JWS algorithms:

   +--------------+-------------------------------+--------------------+
   | "alg" Param  | Digital Signature or MAC      | Implementation     |
   | Value        | Algorithm                     | Requirements       |
   +--------------+-------------------------------+--------------------+
   | HS256        | HMAC using SHA-256            | Required           |
   | HS384        | HMAC using SHA-384            | Optional           |
   | HS512        | HMAC using SHA-512            | Optional           |
   | RS256        | RSASSA-PKCS1-v1_5 using       | Recommended        |
   |              | SHA-256                       |                    |
   | RS384        | RSASSA-PKCS1-v1_5 using       | Optional           |
   |              | SHA-384                       |                    |
   | RS512        | RSASSA-PKCS1-v1_5 using       | Optional           |
   |              | SHA-512                       |                    |
   | ES256        | ECDSA using P-256 and SHA-256 | Recommended+       |
   | ES384        | ECDSA using P-384 and SHA-384 | Optional           |
   | ES512        | ECDSA using P-521 and SHA-512 | Optional           |
   | PS256        | RSASSA-PSS using SHA-256 and  | Optional           |
   |              | MGF1 with SHA-256             |                    |
   | PS384        | RSASSA-PSS using SHA-384 and  | Optional           |
   |              | MGF1 with SHA-384             |                    |
   | PS512        | RSASSA-PSS using SHA-512 and  | Optional           |
   |              | MGF1 with SHA-512             |                    |
   +--------------+-------------------------------+--------------------+

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
sbRsaJwk: HCkStringBuilder;
rsaKey: HCkPublicKey;
success: Boolean;
sbEccJwk: HCkStringBuilder;
eccKey: HCkPublicKey;
hmacKey: PWideChar;
sbJws: HCkStringBuilder;
jws: HCkJws;
protHeader: HCkJsonObject;
sbKeyId: HCkStringBuilder;
bCaseSensitive: Boolean;
numSignatures: Integer;
i: Integer;
v: Integer;

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.

// First, prepare the public keys that will be needed for each signature.

// ---------------------------------------------------
// Use the following RSA key loaded from JWK format.
sbRsaJwk := CkStringBuilder_Create();
CkStringBuilder_Append(sbRsaJwk,'{"kty":"RSA",');
CkStringBuilder_Append(sbRsaJwk,'"n":"ofgWCuLjybRlzo0tZWJjNiuSfb4p4fAkd_wWJcyQoTbji9k0l8W26mPddx');
CkStringBuilder_Append(sbRsaJwk,'HmfHQp-Vaw-4qPCJrcS2mJPMEzP1Pt0Bm4d4QlL-yRT-SFd2lZS-pCgNMs');
CkStringBuilder_Append(sbRsaJwk,'D1W_YpRPEwOWvG6b32690r2jZ47soMZo9wGzjb_7OMg0LOL-bSf63kpaSH');
CkStringBuilder_Append(sbRsaJwk,'SXndS5z5rexMdbBYUsLA9e-KXBdQOS-UTo7WTBEMa2R2CapHg665xsmtdV');
CkStringBuilder_Append(sbRsaJwk,'MTBQY4uDZlxvb3qCo5ZwKh9kG4LT6_I5IhlJH7aGhyxXFvUK-DWNmoudF8');
CkStringBuilder_Append(sbRsaJwk,'NAco9_h9iaGNj8q2ethFkMLs91kzk2PAcDTW9gb54h4FRWyuXpoQ",');
CkStringBuilder_Append(sbRsaJwk,'"e":"AQAB"');
CkStringBuilder_Append(sbRsaJwk,'}');

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

// ---------------------------------------------------
// Use the following ECC public key loaded from JWK format.
sbEccJwk := CkStringBuilder_Create();
CkStringBuilder_Append(sbEccJwk,'{"kty":"EC",');
CkStringBuilder_Append(sbEccJwk,'"crv":"P-256",');
CkStringBuilder_Append(sbEccJwk,'"x":"f83OJ3D2xF1Bg8vub9tLe1gHMzV76e8Tus9uPHvRVEU",');
CkStringBuilder_Append(sbEccJwk,'"y":"x_FEzRu9m36HLN_tue659LNpXW6pCyStikYjKIWI5a0"');
CkStringBuilder_Append(sbEccJwk,'}');

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

// ---------------------------------------------------
// The HMAC key (in base64url format)
hmacKey := 'AyM1SysPpbyDfgZld3umj1qzKObwVMkoqQ-EstJQLr_T-1qS0gZH75aKtMN3Yj0iPS4hcgUuTwjAzZr1Z9CAow';

// The code below will verify each of the signatures in this JWS:

// { 
//   "payload": "SW4gb3VyIHZpbGxhZ2UsIGZvbGtzIHNheSBHb2QgY3J1bWJsZXMgdXAgdGhlIG9sZCBtb29uIGludG8gc3RhcnMu",
//   "signatures": [
//     { 
//       "protected": "eyJhbGciOiJSUzI1NiIsImtpZCI6Im15UnNhS2V5In0",
//       "signature": "IPMQ02niTQDwLzsRZSCaEm9VEyAX_AVe3HWjniNt9kW-a8d6ZVbd2k6jGae8s1yIh0cgxDnXQ6-p6_sBI0cnMO0xpuJANhh2vFtNJl5lisad94-H3mB3lSfafRqxeYp5D8bh39BPv7y3PrUNVMQdKEJp_D5oJ0ROPTIYx3EG8eJQOx1HO0KqhcUo401XR6KSsIyFm5joBLNKTVzxZUTT1RRZZtwTdeZkbGevugIOX_9gHAtARpV6WaFA4Vvjnq8X9wPgqjWNCQRupadhTPz0JAsa-wy5vXQjsFlXAn43mDPpMfna5Ab3F5pS4yDwkbX6nRn7XBxH1SnnNJRFholQZw"
//     },
//     { 
//       "protected": "eyJhbGciOiJFUzI1NiIsImtpZCI6Im15RWNLZXkifQ",
//       "signature": "1OQtaT3pgZmkDxvlfghvxL_8kX16WIen6u1MadEq1pA4qytA0--_EwZDNk00GDPWFpoJtKznibMZzLOg_UhHIw"
//     },
//     { 
//       "protected": "eyJhbGciOiJIUzI1NiIsImtpZCI6Im15TWFjS2V5In0",
//       "signature": "YY8yVjmJJfy7YJOn3uUydG8WCY2PEuCvOLil5Ks5lnw"
//     }
//   ]
// }

sbJws := CkStringBuilder_Create();
CkStringBuilder_Append(sbJws,'{ ');
CkStringBuilder_Append(sbJws,'  "payload": "SW4gb3VyIHZpbGxhZ2UsIGZvbGtzIHNheSBHb2QgY3J1bWJsZXMgdXAgdGhlIG9sZCBtb29uIGludG8gc3RhcnMu",');
CkStringBuilder_Append(sbJws,'  "signatures": [');
CkStringBuilder_Append(sbJws,'    { ');
CkStringBuilder_Append(sbJws,'      "protected": "eyJhbGciOiJSUzI1NiIsImtpZCI6Im15UnNhS2V5In0",');
CkStringBuilder_Append(sbJws,'      "signature": "IPMQ02niTQDwLzsRZSCaEm9VEyAX_AVe3HWjniNt9kW-a8d6ZVbd2k6jGae8s1yIh0cgxDnXQ6-p6_sBI0cnMO0xpuJANhh2vFtNJl5lisad94-H3mB3lSfafRqxeYp5D8bh39BPv7y3PrUNVMQdKEJp_D5oJ0ROPTIYx3EG8eJQOx1HO0KqhcUo401XR6KSsIyFm5joBLNKTVzxZUTT1RRZZtwTdeZkbGevugIOX_9gHAtARpV6WaFA4Vvjnq8X9wPgqjWNCQRupadhTPz0JAsa-wy5vXQjsFlXAn43mDPpMfna5Ab3F5pS4yDwkbX6nRn7XBxH1SnnNJRFholQZw"');
CkStringBuilder_Append(sbJws,'    },');
CkStringBuilder_Append(sbJws,'    { ');
CkStringBuilder_Append(sbJws,'      "protected": "eyJhbGciOiJFUzI1NiIsImtpZCI6Im15RWNLZXkifQ",');
CkStringBuilder_Append(sbJws,'      "signature": "1OQtaT3pgZmkDxvlfghvxL_8kX16WIen6u1MadEq1pA4qytA0--_EwZDNk00GDPWFpoJtKznibMZzLOg_UhHIw"');
CkStringBuilder_Append(sbJws,'    },');
CkStringBuilder_Append(sbJws,'    { ');
CkStringBuilder_Append(sbJws,'      "protected": "eyJhbGciOiJIUzI1NiIsImtpZCI6Im15TWFjS2V5In0",');
CkStringBuilder_Append(sbJws,'      "signature": "YY8yVjmJJfy7YJOn3uUydG8WCY2PEuCvOLil5Ks5lnw"');
CkStringBuilder_Append(sbJws,'    }');
CkStringBuilder_Append(sbJws,'  ]');
CkStringBuilder_Append(sbJws,'}');

jws := CkJws_Create();

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

// The payload is easily accessible:
Memo1.Lines.Add('Payload: ' + CkJws__getPayload(jws,'utf-8'));

sbKeyId := CkStringBuilder_Create();
bCaseSensitive := False;

numSignatures := CkJws_getNumSignatures(jws);
i := 0;
while i < numSignatures do
  begin
    protHeader := CkJws_GetProtectedHeader(jws,i);

    Memo1.Lines.Add('--------------------------');
    Memo1.Lines.Add(IntToStr(i) + ': ');

    // Get the protected header.
    CkJsonObject_putEmitCompact(protHeader,False);
    Memo1.Lines.Add(CkJsonObject__emit(protHeader));

    // Get the key ID ("kid") member.

    // Note: In this example, the "kid" values are contained in the protected headers.
    // They could've just as easily been located in unprotected headers.  In that case,
    // we would've called GetUnprotectedHeader(i) instead of GetProtectedHeader(i).

    CkStringBuilder_Clear(sbKeyId);
    CkStringBuilder_Append(sbKeyId,CkJsonObject__stringOf(protHeader,'kid'));

    // Set the key based on key ID.
    if (CkStringBuilder_ContentsEqual(sbKeyId,'myRsaKey',bCaseSensitive) = True) then
      begin
        CkJws_SetPublicKey(jws,i,rsaKey);
      end;
    if (CkStringBuilder_ContentsEqual(sbKeyId,'myEcKey',bCaseSensitive) = True) then
      begin
        CkJws_SetPublicKey(jws,i,eccKey);
      end;
    if (CkStringBuilder_ContentsEqual(sbKeyId,'myMacKey',bCaseSensitive) = True) then
      begin
        CkJws_SetMacKey(jws,i,hmacKey,'base64url');
      end;

    // Validate this signature.
    v := CkJws_Validate(jws,i);
    if (v < 0) then
      begin
        // Perhaps Chilkat was not unlocked or the trial expired..
        Memo1.Lines.Add('Validate failed for some other reason.');
        Memo1.Lines.Add(CkJws__lastErrorText(jws));
      end
    else
      begin
        if (v = 0) then
          begin
            Memo1.Lines.Add('Invalid signature.  The key was incorrect, the JWS was invalid, or both.');
          end
        else
          begin
            Memo1.Lines.Add('Signature validated.');
          end;
      end;

    CkJsonObject_Dispose(protHeader);
    i := i + 1;
  end;

// The output of this program is:

// 	Payload: In our village, folks say God crumbles up the old moon into stars.
// 	--------------------------
// 	0: 
// 	{
// 	  "alg": "RS256",
// 	  "kid": "myRsaKey"
// 	}
// 
// 	Signature validated.
// 	--------------------------
// 	1: 
// 	{
// 	  "alg": "ES256",
// 	  "kid": "myEcKey"
// 	}
// 
// 	Signature validated.
// 	--------------------------
// 	2: 
// 	{
// 	  "alg": "HS256",
// 	  "kid": "myMacKey"
// 	}
// 
// 	Signature validated.

CkStringBuilder_Dispose(sbRsaJwk);
CkPublicKey_Dispose(rsaKey);
CkStringBuilder_Dispose(sbEccJwk);
CkPublicKey_Dispose(eccKey);
CkStringBuilder_Dispose(sbJws);
CkJws_Dispose(jws);
CkStringBuilder_Dispose(sbKeyId);

end;