Fetching data from API with HMAC SHA512 - Swift

Question

I'm trying to use API described here. It uses HMAC SHA512 authorization based on a secret key.

There is an example of implementation in PHP:

function bitmarket_api($method, $params = array())
{
  $key = "klucz_jawny";
  $secret = "klucz_tajny";

  $params["method"] = $method;
  $params["tonce"] = time();

  $post = http_build_query($params, "", "&");
  $sign = hash_hmac("sha512", $post, $secret);
  $headers = array(
      "API-Key: " . $key,
      "API-Hash: " . $sign,
  );

  $curl = curl_init();
  curl_setopt($curl, CURLOPT_RETURNTRANSFER, true);
  curl_setopt($curl, CURLOPT_URL, "https://www.bitmarket.pl/api2/");
  curl_setopt($curl, CURLOPT_POST, true);
  curl_setopt($curl, CURLOPT_POSTFIELDS, $post);
  curl_setopt($curl, CURLOPT_HTTPHEADER, $headers);
  $ret = curl_exec($curl);

  return json_decode($ret);
}

Then I was trying to implement it in Swift:

import Alamofire
import CryptoSwift

func getRawJSON(method: String, params: [String]) -> String {
    let publicKey = "publicKeyHere"
    let secretKey = "secretKeyHere"
    let APIURL = "https://www.bitmarket.pl/api2/"

    var params = [
        "method": method,
        "tonce:": NSDate().timeIntervalSince1970
        ] as [String : Any]

    let hmac: Array<UInt8> = try! HMAC(key: secretKey.utf8.map({$0}), variant: .sha512).authenticate(params)

    var headers = [
        "API-Key": publicKey,
        "API-Hash": hmac
    ] as [String : Any]
}

As you may noticed, there is no Alamofire usage for fetching data yet because I have a problem with preparing data to send. I mean I've messed up something with CryptoSwift because I'm getting this error: Cannot convert value of type '[String : Any]' to expected argument type 'Array<UInt8>' when I'm trying to declare hmac variable.

How to solve it? I probably have to convert params array to Array<UInt8 somehow, but I don't know how to do that. I'm not sure is everything correct too.

Edit: Thanks to Martin R, the actual code is:

func getRawJSON(method: String, paramether: String) {
    let publicKey = "publicKeyHere"
    let secretKey = "secretKeyHere"
    let APIURL = "https://www.bitmarket.pl/api2/"

    let query = NSURLComponents()
    query.queryItems = [NSURLQueryItem(name: "method", value: method) as URLQueryItem,
                        NSURLQueryItem(name: "tonce", value: String(Int(NSDate().timeIntervalSince1970))) as URLQueryItem]

    let requestString = query.query!
    let requestData = Array(requestString.utf8)

    let params = [
        "method": method,
        "tonce:": String(Int(NSDate().timeIntervalSince1970))
        ] as [String : Any]

    let hmac: Array<UInt8> = try! HMAC(key: secretKey.utf8.map({$0}), variant: .sha512).authenticate(requestData)

    let hmacData = Data(bytes: hmac)
    let hmacString = hmacData.base64EncodedString()

    let headers = [
        "API-Key": publicKey,
        "API-Hash": hmacString
    ] as [String : String]

    Alamofire.request(APIURL, withMethod: .post, parameters: params, encoding: .url, headers: headers)
        .responseJSON { response in
        print(response)
    }
}

Unfortunately, after calling the function (getRawJSON(method: "info", paramether: "")), I'm fetching a JSON with an error:

{
error = 502;
errorMsg = "Invalid message hash";
time = 1472910139;
}

What's wrong with my hash?

score 0 · Answer 1 · answered Sep 03 '16 at 09:06

0

Your Swift code is missing what

$post = http_build_query($params, "", "&");

does in the PHP version: Create a query string from the given parameters. You can either "manually" build that string, or use NSURLComponents:

let comps = NSURLComponents()
comps.queryItems = [ NSURLQueryItem(name: "method",
                                    value: "YOUR_METHOD"),
                     NSURLQueryItem(name: "tonce",
                                    value: String(Int(NSDate().timeIntervalSince1970))) ]
let requestString = comps.query!
print(requestString) // method=YOUR_METHOD&tonce=1472893376

Finally convert this string to an [UInt8] array for the HMAC function:

let requestData = Array(requestString.utf8)
print(requestData) // [109, 101, 116, ..., 54]

answered Sep 03 '16 at 09:06

Martin R

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Huge thanks, helped a lot. Now I'm getting a problem with hash, edited my question with more details. – kkarol Sep 03 '16 at 13:49
@kkarol: Compare the `$post` and `$sign` values from the PHP code with `requestString` and `hmac` from the Swift code. – Martin R Sep 03 '16 at 13:53
`requestString` is equal to `$post`, but `$sign` is different from `hmac` and `hmacString`. `hmacString` is base64 while `$sign` contains e.g. `450043310da274122369bfc0ca621e47fb0b03857746c096a944748585fcd3280744ee4633711f98bbfe3bf0c199deec329a64b723799e597304cfd683ac40e6`. Don't know how to convert `Array` to right format. – kkarol Sep 03 '16 at 14:37
@kkarol: You have to convert the data to a *hex string*, not to a Base64 encoded string. See for example http://stackoverflow.com/a/38131414/1187415. – Martin R Sep 09 '16 at 07:58

Fetching data from API with HMAC SHA512 - Swift

1 Answers1