(C) JWS Using RSASSA-PSS using SHA-256 and MGF1 with SHA-256

Creates and validates a JSON Web Signature (JWS) using RSASSA-PSS using SHA-256 and MGF1 with SHA-256.

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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#include <C_CkStringBuilder.h>
#include <C_CkPrivateKey.h>
#include <C_CkJsonObject.h>
#include <C_CkJws.h>
#include <C_CkPublicKey.h>

void ChilkatSample(void)
    {
    HCkStringBuilder sbJwk;
    HCkPrivateKey rsaKey;
    BOOL success;
    HCkJsonObject jwsProtHdr;
    HCkJws jws;
    int signatureIndex;
    BOOL bIncludeBom;
    const char *payloadStr;
    const char *jwsCompact;
    HCkJws jws2;
    HCkPublicKey rsaPubKey;
    int v;
    HCkJsonObject 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.

    // Use the following RSA key loaded from JWK format.
    sbJwk = CkStringBuilder_Create();
    CkStringBuilder_Append(sbJwk,"{\"kty\":\"RSA\",");
    CkStringBuilder_Append(sbJwk,"\"n\":\"ofgWCuLjybRlzo0tZWJjNiuSfb4p4fAkd_wWJcyQoTbji9k0l8W26mPddx");
    CkStringBuilder_Append(sbJwk,"HmfHQp-Vaw-4qPCJrcS2mJPMEzP1Pt0Bm4d4QlL-yRT-SFd2lZS-pCgNMs");
    CkStringBuilder_Append(sbJwk,"D1W_YpRPEwOWvG6b32690r2jZ47soMZo9wGzjb_7OMg0LOL-bSf63kpaSH");
    CkStringBuilder_Append(sbJwk,"SXndS5z5rexMdbBYUsLA9e-KXBdQOS-UTo7WTBEMa2R2CapHg665xsmtdV");
    CkStringBuilder_Append(sbJwk,"MTBQY4uDZlxvb3qCo5ZwKh9kG4LT6_I5IhlJH7aGhyxXFvUK-DWNmoudF8");
    CkStringBuilder_Append(sbJwk,"NAco9_h9iaGNj8q2ethFkMLs91kzk2PAcDTW9gb54h4FRWyuXpoQ\",");
    CkStringBuilder_Append(sbJwk,"\"e\":\"AQAB\",");
    CkStringBuilder_Append(sbJwk,"\"d\":\"Eq5xpGnNCivDflJsRQBXHx1hdR1k6Ulwe2JZD50LpXyWPEAeP88vLNO97I");
    CkStringBuilder_Append(sbJwk,"jlA7_GQ5sLKMgvfTeXZx9SE-7YwVol2NXOoAJe46sui395IW_GO-pWJ1O0");
    CkStringBuilder_Append(sbJwk,"BkTGoVEn2bKVRUCgu-GjBVaYLU6f3l9kJfFNS3E0QbVdxzubSu3Mkqzjkn");
    CkStringBuilder_Append(sbJwk,"439X0M_V51gfpRLI9JYanrC4D4qAdGcopV_0ZHHzQlBjudU2QvXt4ehNYT");
    CkStringBuilder_Append(sbJwk,"CBr6XCLQUShb1juUO1ZdiYoFaFQT5Tw8bGUl_x_jTj3ccPDVZFD9pIuhLh");
    CkStringBuilder_Append(sbJwk,"BOneufuBiB4cS98l2SR_RQyGWSeWjnczT0QU91p1DhOVRuOopznQ\",");
    CkStringBuilder_Append(sbJwk,"\"p\":\"4BzEEOtIpmVdVEZNCqS7baC4crd0pqnRH_5IB3jw3bcxGn6QLvnEtfdUdi");
    CkStringBuilder_Append(sbJwk,"YrqBdss1l58BQ3KhooKeQTa9AB0Hw_Py5PJdTJNPY8cQn7ouZ2KKDcmnPG");
    CkStringBuilder_Append(sbJwk,"BY5t7yLc1QlQ5xHdwW1VhvKn-nXqhJTBgIPgtldC-KDV5z-y2XDwGUc\",");
    CkStringBuilder_Append(sbJwk,"\"q\":\"uQPEfgmVtjL0Uyyx88GZFF1fOunH3-7cepKmtH4pxhtCoHqpWmT8YAmZxa");
    CkStringBuilder_Append(sbJwk,"ewHgHAjLYsp1ZSe7zFYHj7C6ul7TjeLQeZD_YwD66t62wDmpe_HlB-TnBA");
    CkStringBuilder_Append(sbJwk,"-njbglfIsRLtXlnDzQkv5dTltRJ11BKBBypeeF6689rjcJIDEz9RWdc\",");
    CkStringBuilder_Append(sbJwk,"\"dp\":\"BwKfV3Akq5_MFZDFZCnW-wzl-CCo83WoZvnLQwCTeDv8uzluRSnm71I3Q");
    CkStringBuilder_Append(sbJwk,"CLdhrqE2e9YkxvuxdBfpT_PI7Yz-FOKnu1R6HsJeDCjn12Sk3vmAktV2zb");
    CkStringBuilder_Append(sbJwk,"34MCdy7cpdTh_YVr7tss2u6vneTwrA86rZtu5Mbr1C1XsmvkxHQAdYo0\",");
    CkStringBuilder_Append(sbJwk,"\"dq\":\"h_96-mK1R_7glhsum81dZxjTnYynPbZpHziZjeeHcXYsXaaMwkOlODsWa");
    CkStringBuilder_Append(sbJwk,"7I9xXDoRwbKgB719rrmI2oKr6N3Do9U0ajaHF-NKJnwgjMd2w9cjz3_-ky");
    CkStringBuilder_Append(sbJwk,"NlxAr2v4IKhGNpmM5iIgOS1VZnOZ68m6_pbLBSp3nssTdlqvd0tIiTHU\",");
    CkStringBuilder_Append(sbJwk,"\"qi\":\"IYd7DHOhrWvxkwPQsRM2tOgrjbcrfvtQJipd-DlcxyVuuM9sQLdgjVk2o");
    CkStringBuilder_Append(sbJwk,"y26F0EmpScGLq2MowX7fhd_QJQ3ydy5cY7YIBi87w93IKLEdfnbJtoOPLU");
    CkStringBuilder_Append(sbJwk,"W0ITrJReOgo1cq9SbsxYawBgfp_gh6A5603k2-ZQwVK0JKSHuLFkuQ3U\"");
    CkStringBuilder_Append(sbJwk,"}");

    rsaKey = CkPrivateKey_Create();
    // Note: This example loads the RSA key from JWK format.  Any format can be loaded
    // into the private key object. (See the online reference documentation..)
    success = CkPrivateKey_LoadJwk(rsaKey,CkStringBuilder_getAsString(sbJwk));
    if (success != TRUE) {
        printf("%s\n",CkPrivateKey_lastErrorText(rsaKey));
        CkStringBuilder_Dispose(sbJwk);
        CkPrivateKey_Dispose(rsaKey);
        return;
    }

    // Create the JWS Protected Header
    jwsProtHdr = CkJsonObject_Create();
    CkJsonObject_AppendString(jwsProtHdr,"alg","PS256");

    jws = CkJws_Create();

    // Set the protected header:
    signatureIndex = 0;
    CkJws_SetProtectedHeader(jws,signatureIndex,jwsProtHdr);

    // Set the RSA key:
    CkJws_SetPrivateKey(jws,signatureIndex,rsaKey);

    // Set the payload.
    bIncludeBom = FALSE;
    payloadStr = "In our village, folks say God crumbles up the old moon into stars.";
    CkJws_SetPayload(jws,payloadStr,"utf-8",bIncludeBom);

    // Create the JWS
    // By default, the compact serialization is used.
    jwsCompact = CkJws_createJws(jws);
    if (CkJws_getLastMethodSuccess(jws) != TRUE) {
        printf("%s\n",CkJws_lastErrorText(jws));
        CkStringBuilder_Dispose(sbJwk);
        CkPrivateKey_Dispose(rsaKey);
        CkJsonObject_Dispose(jwsProtHdr);
        CkJws_Dispose(jws);
        return;
    }

    printf("JWS: %s\n",jwsCompact);

    // Note: RSA PSS padding uses random values, so the output will be different each time a signature is produced.
    // sample output:
    // JWS: eyJhbGciOiJQUzI1NiJ9.SW4gb3VyIHZpbGxhZ2UsIGZvbGtzIHNheSBHb2QgY3J1bWJsZXMgdXAgdGhlIG9sZCBtb29uIGludG8gc3RhcnMu.TRWhwRo5dMv9-8OzrInfJTwmUGYgjLfHk8lqF072ND-FmLWEBnUTOpY8oJXp8FdWw2SalbdOeNlrtlJjwk4XK8Ql2iJ_2qMCtxsvLPhKBOqFoAF4aBvTOEDVJDxf0DaBSiydEEtfTVV2iwBcjWabu5J2XieR5y7QZQtuHsn7T3qKBvCcCejN3Y2oqAT3qMHvu1fTms1r_91wBn_K7Wjd9UkZ1n02qQcUHJznR_OF2BgN7_KWIDAF9ZS9keoju2NPpPelO4yxa2XUPnehY3G7dHKoCxUEQR4d2Xc5voqDASTVCDqQS4PVOZdvT3Ein6-SanAlCwbWBbkvT8g6-5PImQ

    // Now load the JWS, validate, and recover the original text.
    jws2 = CkJws_Create();

    // Load the JWS.
    success = CkJws_LoadJws(jws2,jwsCompact);

    rsaPubKey = CkPrivateKey_GetPublicKey(rsaKey);

    // Set the RSA public key used for validation.
    signatureIndex = 0;
    CkJws_SetPublicKey(jws2,signatureIndex,rsaPubKey);
    CkPublicKey_Dispose(rsaPubKey);

    // Validate the 1st (and only) signature at index 0..
    v = CkJws_Validate(jws2,signatureIndex);
    if (v < 0) {
        // Perhaps Chilkat was not unlocked or the trial expired..
        printf("Method call failed for some other reason.\n");
        printf("%s\n",CkJws_lastErrorText(jws2));
        CkStringBuilder_Dispose(sbJwk);
        CkPrivateKey_Dispose(rsaKey);
        CkJsonObject_Dispose(jwsProtHdr);
        CkJws_Dispose(jws);
        CkJws_Dispose(jws2);
        return;
    }

    if (v == 0) {
        printf("Invalid signature.  The RSA key was incorrect, the JWS was invalid, or both.\n");
        CkStringBuilder_Dispose(sbJwk);
        CkPrivateKey_Dispose(rsaKey);
        CkJsonObject_Dispose(jwsProtHdr);
        CkJws_Dispose(jws);
        CkJws_Dispose(jws2);
        return;
    }

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

    // Recover the original content:
    printf("%s\n",CkJws_getPayload(jws2,"utf-8"));

    // Examine the protected header:
    joseHeader = CkJws_GetProtectedHeader(jws2,signatureIndex);
    if (CkJws_getLastMethodSuccess(jws2) != TRUE) {
        printf("No protected header found at the given index.\n");
        CkStringBuilder_Dispose(sbJwk);
        CkPrivateKey_Dispose(rsaKey);
        CkJsonObject_Dispose(jwsProtHdr);
        CkJws_Dispose(jws);
        CkJws_Dispose(jws2);
        return;
    }

    CkJsonObject_putEmitCompact(joseHeader,FALSE);

    printf("Protected (JOSE) header:\n");
    printf("%s\n",CkJsonObject_emit(joseHeader));
    CkJsonObject_Dispose(joseHeader);

    // Output:

    // 	Signature validated.
    // 	In our village, folks say God crumbles up the old moon into stars.
    // 	Protected (JOSE) header:
    // 	{ 
    // 	  "alg": "PS256"
    // 	}


    CkStringBuilder_Dispose(sbJwk);
    CkPrivateKey_Dispose(rsaKey);
    CkJsonObject_Dispose(jwsProtHdr);
    CkJws_Dispose(jws);
    CkJws_Dispose(jws2);

    }