(C++) Validate JWS Using RSASSA-PKCS1-v1_5 SHA-256

Validates a JSON Web Signature (JWS) that uses RSASSA-PKCS1-v1_5 SHA-256.

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

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#include <CkStringBuilder.h>
#include <CkPublicKey.h>
#include <CkJws.h>
#include <CkJsonObject.h>

void ChilkatSample(void)
    {
    // 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 RSA public key to validate and recover the protected header and payload.

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

    //      {"kty":"RSA", 
    //       "n":"ofgWCuLjybRlzo0tZWJjNiuSfb4p4fAkd_wWJcyQoTbji9k0l8W26mPddx
    //            HmfHQp-Vaw-4qPCJrcS2mJPMEzP1Pt0Bm4d4QlL-yRT-SFd2lZS-pCgNMs
    //            D1W_YpRPEwOWvG6b32690r2jZ47soMZo9wGzjb_7OMg0LOL-bSf63kpaSH
    //            SXndS5z5rexMdbBYUsLA9e-KXBdQOS-UTo7WTBEMa2R2CapHg665xsmtdV
    //            MTBQY4uDZlxvb3qCo5ZwKh9kG4LT6_I5IhlJH7aGhyxXFvUK-DWNmoudF8
    //            NAco9_h9iaGNj8q2ethFkMLs91kzk2PAcDTW9gb54h4FRWyuXpoQ", 
    //       "e":"AQAB"
    //      }

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

    CkPublicKey pubKey;
    bool success = pubKey.LoadFromString(sbPubKey.getAsString());
    if (success != true) {
        std::cout << pubKey.lastErrorText() << "\r\n";
        return;
    }

    CkJws jws;

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

    // Load the JWS.
    CkStringBuilder sbJws;
    sbJws.Append("eyJhbGciOiJSUzI1NiJ9");
    sbJws.Append(".");
    sbJws.Append("eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFt");
    sbJws.Append("cGxlLmNvbS9pc19yb290Ijp0cnVlfQ");
    sbJws.Append(".");
    sbJws.Append("cC4hiUPoj9Eetdgtv3hF80EGrhuB__dzERat0XF9g2VtQgr9PJbu3XOiZj5RZmh7");
    sbJws.Append("AAuHIm4Bh-0Qc_lF5YKt_O8W2Fp5jujGbds9uJdbF9CUAr7t1dnZcAcQjbKBYNX4");
    sbJws.Append("BAynRFdiuB--f_nZLgrnbyTyWzO75vRK5h6xBArLIARNPvkSjtQBMHlb1L07Qe7K");
    sbJws.Append("0GarZRmB_eSN9383LcOLn6_dO--xi12jzDwusC-eOkHWEsqtFZESc6BfI7noOPqv");
    sbJws.Append("hJ1phCnvWh6IeYI2w9QOYEUipUTI8np6LbgGY9Fs98rqVt5AXLIhWkWywlVmtVrB");
    sbJws.Append("p0igcN_IoypGlUPQGe77Rw");

    success = jws.LoadJwsSb(sbJws);
    if (success != true) {
        std::cout << jws.lastErrorText() << "\r\n";
        return;
    }

    // Validate the 1st (and only) signature at index 0..
    int v = jws.Validate(signatureIndex);
    if (v < 0) {
        // Perhaps Chilkat was not unlocked or the trial expired..
        std::cout << "Method call failed for some other reason." << "\r\n";
        std::cout << jws.lastErrorText() << "\r\n";
        return;
    }

    if (v == 0) {
        std::cout << "Invalid signature.  The RSA key was incorrect, the JWS was invalid, or both." << "\r\n";
        return;
    }

    // If we get here, the signature was validated..
    std::cout << "Signature validated." << "\r\n";
    std::cout << "--" << "\r\n";

    // Recover the original content:
    std::cout << "Recovered content:" << "\r\n";
    std::cout << jws.getPayload("utf-8") << "\r\n";
    std::cout << "--" << "\r\n";

    // Examine the protected header:
    CkJsonObject *joseHeader = jws.GetProtectedHeader(signatureIndex);
    if (jws.get_LastMethodSuccess() != true) {
        std::cout << "No protected header found at the given index." << "\r\n";
        return;
    }

    joseHeader->put_EmitCompact(false);

    std::cout << "Protected (JOSE) header:" << "\r\n";
    std::cout << joseHeader->emit() << "\r\n";
    delete joseHeader;

    // Output:

    // 	Signature validated.
    // 	--
    // 	Recovered content:
    // 	{"iss":"joe", 
    // 	 "exp":1300819380,
    // 	 "http://example.com/is_root":true}
    // 	--
    // 	Protected (JOSE) header:
    // 	{ 
    // 	  "alg": "RS256"
    // 	}
    }