(.NET Core C#) 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.

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// 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.
Chilkat.StringBuilder sbRsaJwk = new Chilkat.StringBuilder();
sbRsaJwk.Append("{\"kty\":\"RSA\",");
sbRsaJwk.Append("\"n\":\"ofgWCuLjybRlzo0tZWJjNiuSfb4p4fAkd_wWJcyQoTbji9k0l8W26mPddx");
sbRsaJwk.Append("HmfHQp-Vaw-4qPCJrcS2mJPMEzP1Pt0Bm4d4QlL-yRT-SFd2lZS-pCgNMs");
sbRsaJwk.Append("D1W_YpRPEwOWvG6b32690r2jZ47soMZo9wGzjb_7OMg0LOL-bSf63kpaSH");
sbRsaJwk.Append("SXndS5z5rexMdbBYUsLA9e-KXBdQOS-UTo7WTBEMa2R2CapHg665xsmtdV");
sbRsaJwk.Append("MTBQY4uDZlxvb3qCo5ZwKh9kG4LT6_I5IhlJH7aGhyxXFvUK-DWNmoudF8");
sbRsaJwk.Append("NAco9_h9iaGNj8q2ethFkMLs91kzk2PAcDTW9gb54h4FRWyuXpoQ\",");
sbRsaJwk.Append("\"e\":\"AQAB\"");
sbRsaJwk.Append("}");

Chilkat.PublicKey rsaKey = new Chilkat.PublicKey();
bool success = rsaKey.LoadFromString(sbRsaJwk.GetAsString());
if (success != true) {
    Debug.WriteLine(rsaKey.LastErrorText);
    return;
}

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

Chilkat.PublicKey eccKey = new Chilkat.PublicKey();
success = eccKey.LoadFromString(sbEccJwk.GetAsString());
if (success != true) {
    Debug.WriteLine(eccKey.LastErrorText);
    return;
}

// ---------------------------------------------------
// The HMAC key (in base64url format)
string 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"
//     }
//   ]
// }

Chilkat.StringBuilder sbJws = new Chilkat.StringBuilder();
sbJws.Append("{ ");
sbJws.Append("  \"payload\": \"SW4gb3VyIHZpbGxhZ2UsIGZvbGtzIHNheSBHb2QgY3J1bWJsZXMgdXAgdGhlIG9sZCBtb29uIGludG8gc3RhcnMu\",");
sbJws.Append("  \"signatures\": [");
sbJws.Append("    { ");
sbJws.Append("      \"protected\": \"eyJhbGciOiJSUzI1NiIsImtpZCI6Im15UnNhS2V5In0\",");
sbJws.Append("      \"signature\": \"IPMQ02niTQDwLzsRZSCaEm9VEyAX_AVe3HWjniNt9kW-a8d6ZVbd2k6jGae8s1yIh0cgxDnXQ6-p6_sBI0cnMO0xpuJANhh2vFtNJl5lisad94-H3mB3lSfafRqxeYp5D8bh39BPv7y3PrUNVMQdKEJp_D5oJ0ROPTIYx3EG8eJQOx1HO0KqhcUo401XR6KSsIyFm5joBLNKTVzxZUTT1RRZZtwTdeZkbGevugIOX_9gHAtARpV6WaFA4Vvjnq8X9wPgqjWNCQRupadhTPz0JAsa-wy5vXQjsFlXAn43mDPpMfna5Ab3F5pS4yDwkbX6nRn7XBxH1SnnNJRFholQZw\"");
sbJws.Append("    },");
sbJws.Append("    { ");
sbJws.Append("      \"protected\": \"eyJhbGciOiJFUzI1NiIsImtpZCI6Im15RWNLZXkifQ\",");
sbJws.Append("      \"signature\": \"1OQtaT3pgZmkDxvlfghvxL_8kX16WIen6u1MadEq1pA4qytA0--_EwZDNk00GDPWFpoJtKznibMZzLOg_UhHIw\"");
sbJws.Append("    },");
sbJws.Append("    { ");
sbJws.Append("      \"protected\": \"eyJhbGciOiJIUzI1NiIsImtpZCI6Im15TWFjS2V5In0\",");
sbJws.Append("      \"signature\": \"YY8yVjmJJfy7YJOn3uUydG8WCY2PEuCvOLil5Ks5lnw\"");
sbJws.Append("    }");
sbJws.Append("  ]");
sbJws.Append("}");

Chilkat.Jws jws = new Chilkat.Jws();

success = jws.LoadJwsSb(sbJws);
if (success != true) {
    Debug.WriteLine(jws.LastErrorText);
    return;
}

// The payload is easily accessible:
Debug.WriteLine("Payload: " + jws.GetPayload("utf-8"));

Chilkat.JsonObject protHeader = null;
Chilkat.StringBuilder sbKeyId = new Chilkat.StringBuilder();
bool bCaseSensitive = false;

int numSignatures = jws.NumSignatures;
int i = 0;
while (i < numSignatures) {
    protHeader = jws.GetProtectedHeader(i);

    Debug.WriteLine("--------------------------");
    Debug.WriteLine(Convert.ToString(i) + ": ");

    // Get the protected header.
    protHeader.EmitCompact = false;
    Debug.WriteLine(protHeader.Emit());

    // 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).

    sbKeyId.Clear();
    sbKeyId.Append(protHeader.StringOf("kid"));

    // Set the key based on key ID.
    if (sbKeyId.ContentsEqual("myRsaKey",bCaseSensitive) == true) {
        jws.SetPublicKey(i,rsaKey);
    }

    if (sbKeyId.ContentsEqual("myEcKey",bCaseSensitive) == true) {
        jws.SetPublicKey(i,eccKey);
    }

    if (sbKeyId.ContentsEqual("myMacKey",bCaseSensitive) == true) {
        jws.SetMacKey(i,hmacKey,"base64url");
    }

    // Validate this signature.
    int v = jws.Validate(i);
    if (v < 0) {
        // Perhaps Chilkat was not unlocked or the trial expired..
        Debug.WriteLine("Validate failed for some other reason.");
        Debug.WriteLine(jws.LastErrorText);
    }
    else {
        if (v == 0) {
            Debug.WriteLine("Invalid signature.  The key was incorrect, the JWS was invalid, or both.");
        }
        else {
            Debug.WriteLine("Signature validated.");
        }

    }

    i = i + 1;
}

// 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.