(Unicode C) 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 v9.5.0.66 or greater.

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#include <C_CkStringBuilderW.h>
#include <C_CkPublicKeyW.h>
#include <C_CkJwsW.h>
#include <C_CkJsonObjectW.h>

void ChilkatSample(void)
    {
    HCkStringBuilderW sbPubKey;
    HCkPublicKeyW pubKey;
    BOOL success;
    HCkJwsW jws;
    int signatureIndex;
    HCkStringBuilderW sbJws;
    int v;
    HCkJsonObjectW joseHeader;

    // 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-256", 
    //       "x":"f83OJ3D2xF1Bg8vub9tLe1gHMzV76e8Tus9uPHvRVEU", 
    //       "y":"x_FEzRu9m36HLN_tue659LNpXW6pCyStikYjKIWI5a0" 
    //      } 

    sbPubKey = CkStringBuilderW_Create();
    CkStringBuilderW_Append(sbPubKey,L"{\"kty\":\"EC\",");
    CkStringBuilderW_Append(sbPubKey,L"\"crv\":\"P-256\",");
    CkStringBuilderW_Append(sbPubKey,L"\"x\":\"f83OJ3D2xF1Bg8vub9tLe1gHMzV76e8Tus9uPHvRVEU\",");
    CkStringBuilderW_Append(sbPubKey,L"\"y\":\"x_FEzRu9m36HLN_tue659LNpXW6pCyStikYjKIWI5a0\"");
    CkStringBuilderW_Append(sbPubKey,L"}");

    pubKey = CkPublicKeyW_Create();
    success = CkPublicKeyW_LoadFromString(pubKey,CkStringBuilderW_getAsString(sbPubKey));
    if (success != TRUE) {
        wprintf(L"%s\n",CkPublicKeyW_lastErrorText(pubKey));
        CkStringBuilderW_Dispose(sbPubKey);
        CkPublicKeyW_Dispose(pubKey);
        return;
    }

    jws = CkJwsW_Create();

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

    // Load the JWS.
    sbJws = CkStringBuilderW_Create();
    CkStringBuilderW_Append(sbJws,L"eyJhbGciOiJFUzI1NiJ9");
    CkStringBuilderW_Append(sbJws,L".");
    CkStringBuilderW_Append(sbJws,L"eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFt");
    CkStringBuilderW_Append(sbJws,L"cGxlLmNvbS9pc19yb290Ijp0cnVlfQ");
    CkStringBuilderW_Append(sbJws,L".");
    CkStringBuilderW_Append(sbJws,L"DtEhU3ljbEg8L38VWAfUAqOyKAM6-Xx-F4GawxaepmXFCgfTjDxw5djxLa8ISlSA");
    CkStringBuilderW_Append(sbJws,L"pmWQxfKTUJqPP3-Kg6NU1Q");

    success = CkJwsW_LoadJwsSb(jws,sbJws);
    if (success != TRUE) {
        wprintf(L"%s\n",CkJwsW_lastErrorText(jws));
        CkStringBuilderW_Dispose(sbPubKey);
        CkPublicKeyW_Dispose(pubKey);
        CkJwsW_Dispose(jws);
        CkStringBuilderW_Dispose(sbJws);
        return;
    }

    // Validate the 1st (and only) signature at index 0..
    v = CkJwsW_Validate(jws,signatureIndex);
    if (v < 0) {
        // Perhaps Chilkat was not unlocked or the trial expired..
        wprintf(L"Method call failed for some other reason.\n");
        wprintf(L"%s\n",CkJwsW_lastErrorText(jws));
        CkStringBuilderW_Dispose(sbPubKey);
        CkPublicKeyW_Dispose(pubKey);
        CkJwsW_Dispose(jws);
        CkStringBuilderW_Dispose(sbJws);
        return;
    }

    if (v == 0) {
        wprintf(L"Invalid signature.  The ECC key was incorrect, the JWS was invalid, or both.\n");
        CkStringBuilderW_Dispose(sbPubKey);
        CkPublicKeyW_Dispose(pubKey);
        CkJwsW_Dispose(jws);
        CkStringBuilderW_Dispose(sbJws);
        return;
    }

    // If we get here, the signature was validated..
    wprintf(L"Signature validated.\n");
    wprintf(L"--\n");

    // Recover the original content:
    wprintf(L"Recovered content:\n");
    wprintf(L"%s\n",CkJwsW_getPayload(jws,L"utf-8"));
    wprintf(L"--\n");

    // Examine the protected header:
    joseHeader = CkJwsW_GetProtectedHeader(jws,signatureIndex);
    if (CkJwsW_getLastMethodSuccess(jws) != TRUE) {
        wprintf(L"No protected header found at the given index.\n");
        CkStringBuilderW_Dispose(sbPubKey);
        CkPublicKeyW_Dispose(pubKey);
        CkJwsW_Dispose(jws);
        CkStringBuilderW_Dispose(sbJws);
        return;
    }

    CkJsonObjectW_putEmitCompact(joseHeader,FALSE);

    wprintf(L"Protected (JOSE) header:\n");
    wprintf(L"%s\n",CkJsonObjectW_emit(joseHeader));
    CkJsonObjectW_Dispose(joseHeader);

    // Output:

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


    CkStringBuilderW_Dispose(sbPubKey);
    CkPublicKeyW_Dispose(pubKey);
    CkJwsW_Dispose(jws);
    CkStringBuilderW_Dispose(sbJws);

    }