(Objective-C) Payeezy HMAC Computation

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

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#import <CkoCrypt2.h>
#import <CkoPrng.h>
#import <NSString.h>
#import <CkoDateTime.h>
#import <CkoStringBuilder.h>
#import <CkoJsonObject.h>

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

CkoCrypt2 *crypt = [[CkoCrypt2 alloc] init];
CkoPrng *prng = [[CkoPrng alloc] init];
BOOL success;

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

// The nonce is a random number (bytes), something like "6057786719490086000"
NSString *nonce = [prng GenRandom: [NSNumber numberWithInt: 8] encoding: @"decimal"];
NSLog(@"%@%@",@"nonce = ",nonce);

CkoDateTime *dtNow = [[CkoDateTime alloc] init];
[dtNow SetFromCurrentSystemTime];
CkoStringBuilder *sbTimestamp = [[CkoStringBuilder alloc] init];
// Get the epoch timestamp in seconds
[sbTimestamp Append: [dtNow GetAsUnixTimeStr: NO]];
// Change it to milliseconds
[sbTimestamp Append: @"000"];
// The timestamp is a number similar to this: 1546011905000 (which is a timestamp taken on 28-Dec-2018).
NSString *timestamp = [sbTimestamp GetAsString];
NSLog(@"%@%@",@"timestamp = ",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"
// 	    }
// 	  }
// 	}

CkoJsonObject *json = [[CkoJsonObject alloc] init];
[json UpdateString: @"merchant_ref" value: @"Astonishing-Sale"];
[json UpdateString: @"transaction_type" value: @"authorize"];
[json UpdateString: @"method" value: @"token"];
[json UpdateString: @"amount" value: @"200"];
[json UpdateString: @"currency_code" value: @"USD"];
[json UpdateString: @"token.token_type" value: @"FDToken"];
[json UpdateString: @"token.token_data.type" value: @"visa"];
[json UpdateString: @"token.token_data.value" value: @"2537446225198291"];
[json UpdateString: @"token.token_data.cardholder_name" value: @"JohnSmith"];
[json UpdateString: @"token.token_data.exp_date" value: @"1030"];
[json UpdateString: @"token.token_data.special_payment" value: @"B"];

// string hashData = apiKey + nonce + timestamp + token + jsonString;
CkoStringBuilder *sbHmacData = [[CkoStringBuilder alloc] init];
[sbHmacData Append: apiKey];
[sbHmacData Append: nonce];
[sbHmacData Append: timestamp];
[sbHmacData Append: token];
[sbHmacData Append: [json Emit]];

// HMAC the data to produce a hex string.
crypt.EncodingMode = @"hexlower";
crypt.MacAlgorithm = @"hmac";
[crypt SetMacKeyString: apiSecret];
crypt.HashAlgorithm = @"sha256";
crypt.Charset = @"utf-8";
NSString *hexHash = [crypt MacStringENC: [sbHmacData GetAsString]];

// Now base64 encode the hex string:
CkoStringBuilder *sbBase64Hash = [[CkoStringBuilder alloc] init];
[sbBase64Hash Append: hexHash];
[sbBase64Hash Encode: @"base64" charset: @"utf-8"];

NSLog(@"%@",@"This is the Authorization header to be sent with the payeezy request:");
NSLog(@"%@%@",@"Authorization: ",[sbBase64Hash GetAsString]);