(MFC) Validate a JWS Using ECDSA P-521 SHA-512

Validates a JSON Web Signature (JWS) that uses ECDSA P-521 SHA-512

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

Chilkat C/C++ Library Downloads MS Visual C/C++ Libs

See Also: Using MFC CString in Chilkat

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

void ChilkatSample(void)
    {
    CkString strOut;

    // 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-521", 
    //       "x":"AekpBQ8ST8a8VcfVOTNl353vSrDCLLJXmPk06wTjxrrjcBpXp5EOnYG_NjFZ6OvLFV1jSfS9tsz4qUxcWceqwQGk", 
    //       "y":"ADSmRA43Z1DSNx_RvcLI87cdL07l6jQyyBXMoxVg_l2Th-x3S1WDhjDly79ajL4Kkd0AZMaZmh9ubmf63e3kyMj2" 
    //      } 

    CkStringBuilder sbPubKey;
    sbPubKey.Append("{\"kty\":\"EC\",");
    sbPubKey.Append("\"crv\":\"P-521\",");
    sbPubKey.Append("\"x\":\"AekpBQ8ST8a8VcfVOTNl353vSrDCLLJXmPk06wTjxrrjcBpXp5EOnYG_NjFZ6OvLFV1jSfS9tsz4qUxcWceqwQGk\",");
    sbPubKey.Append("\"y\":\"ADSmRA43Z1DSNx_RvcLI87cdL07l6jQyyBXMoxVg_l2Th-x3S1WDhjDly79ajL4Kkd0AZMaZmh9ubmf63e3kyMj2\"");
    sbPubKey.Append("}");

    CkPublicKey pubKey;
    bool success = pubKey.LoadFromString(sbPubKey.getAsString());
    if (success != true) {
        strOut.append(pubKey.lastErrorText());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    CkJws jws;

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

    // Load the JWS.
    CkStringBuilder sbJws;
    sbJws.Append("eyJhbGciOiJFUzUxMiJ9");
    sbJws.Append(".");
    sbJws.Append("UGF5bG9hZA");
    sbJws.Append(".");
    sbJws.Append("AdwMgeerwtHoh-l192l60hp9wAHZFVJbLfD_UxMi70cwnZOYaRI1bKPWROc-mZZq");
    sbJws.Append("wqT2SI-KGDKB34XO0aw_7XdtAG8GaSwFKdCAPZgoXD2YBJZCPEX3xKpRwcdOO8Kp");
    sbJws.Append("EHwJjyqOgzDO7iKvU8vcnwNrmxYbSW9ERBXukOXolLzeO_Jn");

    success = jws.LoadJwsSb(sbJws);
    if (success != true) {
        strOut.append(jws.lastErrorText());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        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..
        strOut.append("Method call failed for some other reason.");
        strOut.append("\r\n");
        strOut.append(jws.lastErrorText());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    if (v == 0) {
        strOut.append("Invalid signature.  The ECC key was incorrect, the JWS was invalid, or both.");
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    // If we get here, the signature was validated..
    strOut.append("Signature validated.");
    strOut.append("\r\n");
    strOut.append("--");
    strOut.append("\r\n");

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

    // Examine the protected header:
    CkJsonObject *joseHeader = jws.GetProtectedHeader(signatureIndex);
    if (jws.get_LastMethodSuccess() != true) {
        strOut.append("No protected header found at the given index.");
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    joseHeader->put_EmitCompact(false);

    strOut.append("Protected (JOSE) header:");
    strOut.append("\r\n");
    strOut.append(joseHeader->emit());
    strOut.append("\r\n");
    delete joseHeader;

    // Output:
    // (the string "Payload" was the content that was signed.)

    // 	Signature validated.
    // 	--
    // 	Recovered content:
    // 	Payload
    // 	--
    // 	Protected (JOSE) header:
    // 	{
    // 	  "alg": "ES512"
    // 	}


    SetDlgItemText(IDC_EDIT1,strOut.getUnicode());

    }