(JavaScript) 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 v11.0.0 or greater.

Note

This example is intended for running within a Chilkat.Js embedded JavaScript engine. All Chilkat JavaScript examples require Chilkat v11.4.0 or greater.

var success = false;

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

// 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" 
//      } 

var sbPubKey = new CkStringBuilder();
sbPubKey.Append("{\"kty\":\"EC\",");
sbPubKey.Append("\"crv\":\"P-256\",");
sbPubKey.Append("\"x\":\"f83OJ3D2xF1Bg8vub9tLe1gHMzV76e8Tus9uPHvRVEU\",");
sbPubKey.Append("\"y\":\"x_FEzRu9m36HLN_tue659LNpXW6pCyStikYjKIWI5a0\"");
sbPubKey.Append("}");

var pubKey = new CkPublicKey();
success = pubKey.LoadFromString(sbPubKey.GetAsString());
if (success == false) {
    console.log(pubKey.LastErrorText);
    return;
}

var jws = new CkJws();

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

// Load the JWS.
var sbJws = new CkStringBuilder();
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);
if (success == false) {
    console.log(jws.LastErrorText);
    return;
}

// Validate the 1st (and only) signature at index 0..
var v = jws.Validate(signatureIndex);
if (v < 0) {
    // Perhaps Chilkat was not unlocked or the trial expired..
    console.log("Method call failed for some other reason.");
    console.log(jws.LastErrorText);
    return;
}

if (v == 0) {
    console.log("Invalid signature.  The ECC key was incorrect, the JWS was invalid, or both.");
    return;
}

// If we get here, the signature was validated..
console.log("Signature validated.");
console.log("--");

// Recover the original content:
console.log("Recovered content:");
console.log(jws.GetPayload("utf-8"));
console.log("--");

// Examine the protected header:

var joseHeader = new CkJsonObject();
success = jws.GetProtectedH(signatureIndex,joseHeader);
if (success == false) {
    console.log(jws.LastErrorText);
    return;
}

joseHeader.EmitCompact = false;

console.log("Protected (JOSE) header:");
console.log(joseHeader.Emit());

// Output:

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