(C) Payeezy HMAC Computation

Demonstrates how to calculate the HMAC for a Payeezy REST request.

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#include <C_CkCrypt2.h>
#include <C_CkPrng.h>
#include <C_CkDateTime.h>
#include <C_CkStringBuilder.h>
#include <C_CkJsonObject.h>

void ChilkatSample(void)
    {
    HCkCrypt2 crypt;
    HCkPrng prng;
    BOOL success;
    const char *apiKey;
    const char *apiSecret;
    const char *token;
    const char *nonce;
    HCkDateTime dtNow;
    HCkStringBuilder sbTimestamp;
    const char *timestamp;
    HCkJsonObject json;
    HCkStringBuilder sbHmacData;
    const char *hexHash;
    HCkStringBuilder sbBase64Hash;

    // This example requires the Chilkat API to have been previously unlocked.
    // See Global Unlock Sample for sample code.

    crypt = CkCrypt2_Create();
    prng = CkPrng_Create();

    // An API key such as y6pWAJNyJyjGv66IsVuWnklkKUPFbb0a
    apiKey = "my_api_key";
    // An API secret such as 86fbae7030253af3cd15faef2a1f4b67353e41fb6799f576b5093ae52901e6f7
    apiSecret = "my_api_secret";
    // A token such as fdoa-a480ce8951daa73262734cf102641994c1e55e7cdf4c02b6
    token = "my_merchant_token";

    // The nonce is a random number (bytes), something like "6057786719490086000"
    nonce = CkPrng_genRandom(prng,8,"decimal");
    printf("nonce = %s\n",nonce);

    dtNow = CkDateTime_Create();
    CkDateTime_SetFromCurrentSystemTime(dtNow);
    sbTimestamp = CkStringBuilder_Create();
    // Get the epoch timestamp in seconds
    CkStringBuilder_Append(sbTimestamp,CkDateTime_getAsUnixTimeStr(dtNow,FALSE));
    // Change it to milliseconds
    CkStringBuilder_Append(sbTimestamp,"000");
    // The timestamp is a number similar to this: 1546011905000 (which is a timestamp taken on 28-Dec-2018).
    timestamp = CkStringBuilder_getAsString(sbTimestamp);
    printf("timestamp = %s\n",timestamp);

    // Generate the following JSON request body:
    // 	{
    // 	  "merchant_ref": "Astonishing-Sale",
    // 	  "transaction_type": "authorize",
    // 	  "method": "token",
    // 	  "amount": "200",
    // 	  "currency_code": "USD",
    // 	  "token": {
    // 	    "token_type": "FDToken",
    // 	    "token_data": {
    // 	      "type": "visa",
    // 	      "value": "2537446225198291",
    // 	      "cardholder_name": "JohnSmith",
    // 	      "exp_date": "1030",
    // 	      "special_payment": "B"
    // 	    }
    // 	  }
    // 	}

    json = CkJsonObject_Create();
    CkJsonObject_UpdateString(json,"merchant_ref","Astonishing-Sale");
    CkJsonObject_UpdateString(json,"transaction_type","authorize");
    CkJsonObject_UpdateString(json,"method","token");
    CkJsonObject_UpdateString(json,"amount","200");
    CkJsonObject_UpdateString(json,"currency_code","USD");
    CkJsonObject_UpdateString(json,"token.token_type","FDToken");
    CkJsonObject_UpdateString(json,"token.token_data.type","visa");
    CkJsonObject_UpdateString(json,"token.token_data.value","2537446225198291");
    CkJsonObject_UpdateString(json,"token.token_data.cardholder_name","JohnSmith");
    CkJsonObject_UpdateString(json,"token.token_data.exp_date","1030");
    CkJsonObject_UpdateString(json,"token.token_data.special_payment","B");

    // string hashData = apiKey + nonce + timestamp + token + jsonString;
    sbHmacData = CkStringBuilder_Create();
    CkStringBuilder_Append(sbHmacData,apiKey);
    CkStringBuilder_Append(sbHmacData,nonce);
    CkStringBuilder_Append(sbHmacData,timestamp);
    CkStringBuilder_Append(sbHmacData,token);
    CkStringBuilder_Append(sbHmacData,CkJsonObject_emit(json));

    // HMAC the data to produce a hex string.
    CkCrypt2_putEncodingMode(crypt,"hexlower");
    CkCrypt2_putMacAlgorithm(crypt,"hmac");
    CkCrypt2_SetMacKeyString(crypt,apiSecret);
    CkCrypt2_putHashAlgorithm(crypt,"sha256");
    CkCrypt2_putCharset(crypt,"utf-8");
    hexHash = CkCrypt2_macStringENC(crypt,CkStringBuilder_getAsString(sbHmacData));

    // Now base64 encode the hex string:
    sbBase64Hash = CkStringBuilder_Create();
    CkStringBuilder_Append(sbBase64Hash,hexHash);
    CkStringBuilder_Encode(sbBase64Hash,"base64","utf-8");

    printf("This is the Authorization header to be sent with the payeezy request:\n");
    printf("Authorization: %s\n",CkStringBuilder_getAsString(sbBase64Hash));


    CkCrypt2_Dispose(crypt);
    CkPrng_Dispose(prng);
    CkDateTime_Dispose(dtNow);
    CkStringBuilder_Dispose(sbTimestamp);
    CkJsonObject_Dispose(json);
    CkStringBuilder_Dispose(sbHmacData);
    CkStringBuilder_Dispose(sbBase64Hash);

    }