How do I port php's openssl_sign to C#?

Question

Hi,

I need to translate the following code to C# from php. What libraries / namespaces do I need to use?

function sign($method, $uuid, $data) {
    $merchant_private_key = openssl_get_privatekey(file_get_contents('merchant_private_key.pem'));
    $plaintext = $method . $uuid . serialize_data($data);
    **openssl_sign($plaintext, $signature, $merchant_private_key);**
    return base64_encode($signature);
}

The api can be found over at http://php.net/manual/en/function.openssl-sign.php. Where do I start? I have no idea what the open_ssl sign in php does behind the covers.

Anyone able to help out that knows both php and C# or could someone at least explain what openssl_sign does in the background so that I can port it.

EDIT: 2010-08-18 I can't find a way to use openssl, it keeps saying it can't load managedopenssl.dll. Think it is because of my machine being x64.

Answer 1

The difficulty here consist in reading and decoding the private key. You could use the following openssl helper class. Once you have referenced it you may try this:

public static string Sign(string method, string uuid, string data)
{
    string merchantPrivateKey = File.ReadAllText("merchant_private_key.pem");
    byte[] der = opensslkey.DecodePkcs8PrivateKey(merchantPrivateKey);
    using (RSACryptoServiceProvider rsa = opensslkey.DecodePrivateKeyInfo(der))
    using (MD5CryptoServiceProvider md5 = new MD5CryptoServiceProvider())
    {
        // This will contain the data to sign
        byte[] dataToSign = Encoding.Default.GetBytes(method + uuid + data);
        byte[] signature = rsa.SignData(dataToSign, md5);
        return Convert.ToBase64String(signature);
    }
}

In this example I have used MD5 but you could use anything that is appropriate to your scenario. I think openssl_sign uses SHA1 by default.

Answer 2

maybe this can help?

Answer 3

Thank you for the suggestions.

I have found a solution for my problems. There is a library called ChilKat that we will be using. The answer was found here. Unfortunately this does not work on my x64 machine. Fortunately our servers are all x86 still so we have some more time to look into a workaround.