PHP and C# HMAC SHA256

Question

I need to convert the following php code in C#:

$res = mac256($ent, $key);
$result = encodeBase64($res);

where

function enc         


        

Answer 1

Redsys provides libraries for php and java.

Starting from the java library, I've translated the ApiMacSha256 class to C#

public class ApiMacSha256 {
    //////////////////////////////////////////////////////////////////////////////////////////////
    //////////////////////////////////////////////////////////////////////////////////////////////
    ////////////                    FUNCIONES AUXILIARES:                              ///////////
    //////////////////////////////////////////////////////////////////////////////////////////////
    //////////////////////////////////////////////////////////////////////////////////////////////

    /** 3DES Function */
    private byte[] encrypt_3DES(byte[] key, string data) {
        //http://www.mywebexperiences.com/2012/12/11/crypting-data-using-3des-c/
        //http://stackoverflow.com/a/33479952/2938518
        using (var tdes = new TripleDESCryptoServiceProvider()) {
            tdes.IV = new byte[8] { 0, 0, 0, 0, 0, 0, 0, 0 };
            tdes.Key = key;
            tdes.Padding = PaddingMode.Zeros;
            tdes.Mode = CipherMode.CBC;

            var toEncrypt = Encoding.ASCII.GetBytes(data);
            var result = tdes.CreateEncryptor().TransformFinalBlock(toEncrypt, 0, toEncrypt.Length);

            return result;
        }
    }

    /** MAC Function */
    private byte[] mac256(string dsMerchantParameters, byte[] secretKo) {
        //http://stackoverflow.com/a/17315619/2938518
        byte[] hash;
        using (var hmac = new HMACSHA256(secretKo)) {
            hash = hmac.ComputeHash(Encoding.ASCII.GetBytes(dsMerchantParameters));
        }

        return hash;
    }

    /** Base64 Functions */
    private string encodeB64String(byte[] data) {
        return Convert.ToBase64String(data, Base64FormattingOptions.None);
    }

    //////////////////////////////////////////////////////////////////////////////////////////////
    //////////////////////////////////////////////////////////////////////////////////////////////
    ////////////        FUNCIONES PARA LA GENERACIÓN DEL FORMULARIO DE PAGO:          ////////////
    //////////////////////////////////////////////////////////////////////////////////////////////
    //////////////////////////////////////////////////////////////////////////////////////////////
    public String createMerchantSignature(string merchantParamsB64, string claveComercio, string OrderId) {
        byte[] clave = Convert.FromBase64String(claveComercio);
        byte[] secretKo = encrypt_3DES(clave, OrderId);

        // Se hace el MAC con la clave de la operación "Ko" y se codifica en BASE64
        byte[] hash = mac256(merchantParamsB64, secretKo);
        String res = encodeB64String(hash);
        return res;
    }
}

The main method 'createMerchantSignature', requires a string encoded in base64 of the merchant params embeded in a json structure, the secret key of the merchant and the OrderId.