(C) JWS Using HMAC SHA-256

Creates a JSON Web Signatures (JWS) using HMAC SHA-256.

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

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#include <C_CkJsonObject.h>
#include <C_CkJws.h>

void ChilkatSample(void)
    {
    BOOL success;
    HCkJsonObject jwsProtHdr;
    HCkJws jws;
    const char *hmacKey;
    int signatureIndex;
    BOOL bIncludeBom;
    const char *payloadStr;
    const char *jwsCompact;
    HCkJws jws2;
    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.

    // First create the JWS Protected Header
    jwsProtHdr = CkJsonObject_Create();
    CkJsonObject_AppendString(jwsProtHdr,"typ","JWT");
    CkJsonObject_AppendString(jwsProtHdr,"alg","HS256");
    printf("JWS Protected Header: %s\n",CkJsonObject_emit(jwsProtHdr));

    // Output:
    // JWS Protected Header: {"typ":"JWT","alg":"HS256"}

    jws = CkJws_Create();

    // Set the HMAC key:
    hmacKey = "AyM1SysPpbyDfgZld3umj1qzKObwVMkoqQ-EstJQLr_T-1qS0gZH75aKtMN3Yj0iPS4hcgUuTwjAzZr1Z9CAow";
    signatureIndex = 0;
    CkJws_SetMacKey(jws,signatureIndex,hmacKey,"base64url");

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

    // 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));
        CkJsonObject_Dispose(jwsProtHdr);
        CkJws_Dispose(jws);
        return;
    }

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

    // sample output:
    // JWS: eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.SW4gb3VyIHZpbGxhZ2UsIGZvbGtzIHNheSBHb2QgY3J1bWJsZXMgdXAgdGhlIG9sZCBtb29uIGludG8gc3RhcnMu.bsYsi8HJ0N6OqGI1hKQ9QQRNPxxA5qMpcHLtOvXatk8

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

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

    // Set the MAC key used for validation.
    signatureIndex = 0;
    CkJws_SetMacKey(jws2,signatureIndex,hmacKey,"base64url");

    // 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));
        CkJsonObject_Dispose(jwsProtHdr);
        CkJws_Dispose(jws);
        CkJws_Dispose(jws2);
        return;
    }

    if (v == 0) {
        printf("Invalid signature.  The MAC key was incorrect, the JWS was invalid, or both.\n");
        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");
        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:
    // 	{ 
    // 	  "typ": "JWT",
    // 	  "alg": "HS256"
    // 	} 


    CkJsonObject_Dispose(jwsProtHdr);
    CkJws_Dispose(jws);
    CkJws_Dispose(jws2);

    }