sign okex api in flutter - flutter

Question

i have problem to sign api for okex
,in document of okex:
The OK-ACCESS-SIGN header is generated as follows:
Create a prehash string of timestamp + method + requestPath + body
(where + represents String concatenation). Prepare the SecretKey. Sign
the prehash string with the SecretKey using the HMAC SHA256. Encode
the signature in the Base64 format. Example:
sign=CryptoJS.enc.Base64.stringify(CryptoJS.HmacSHA256(timestamp +
'GET' + '/users/self/verify', SecretKey))
The timestamp value is the same as the OK-ACCESS-TIMESTAMP header with
millisecond format of ISO, e.g. 2020-12-08T09:08:57.715Z.
The request method should be in UPPERCASE: e.g. GET and POST.
The requestPath is the path of requesting an endpoint.
Example: /api/v5/account/balance
The body refers to the String of the request body. It can be omitted
if there is no request body (frequently the case for GET requests).
method i made fo sign is:
dynamic _getSign(String timestamp, String methodType, String url, String body) {
if (body.isEmpty) {
body = "";
}
String message = timestamp + methodType.toUpperCase() + url + body;
var hmacSha256 = Hmac(sha256, utf8.encode(oKSecretKey));
var mac = hmacSha256.convert(utf8.encode(message));
// var a = mac.bytes;
var a = base64Url.encode(mac.bytes);
print(a);
return a;
}
Future<String> getAccountInfo() async {
try {
String timestamp = getServerTime();
String url = '/api/v5/account/balance';
Response response = await OKEXApi.dio.get(url,
queryParameters: {},
options: Options(headers: {
"OK-ACCESS-KEY": oKACCESSKEY,
"OK-ACCESS-PASSPHRASE": oKACCESSPASSPHRASE,
"OK-ACCESS-TIMESTAMP": timestamp,
"OK-ACCESS-SIGN": _getSign(timestamp, "GET", url, ""),
'Accept': 'application/json',
'Content-type': 'application/json',
}));
print(response.data);
return response.data;
} on DioError catch (e) {
return e.error;
}
}
and for timestamp
String getServerTime() {
DateTime now = DateTime.now().toUtc();
String isoDate = now.toIso8601String();
return isoDate;
}
And when i send data, response is:
{"msg":"Invalid Sign","code":"50113"}

Answer 1

The spec says:
OK-ACCESS-TIMESTAMP header with millisecond format of ISO, e.g.
2020-12-08T09:08:57.715Z
Truncate the microseconds away like this:
final now = DateTime.now().toUtc();
final microlessNow = now.subtract(Duration(microseconds: now.microsecond));
final isoDate = microlessNow.toIso8601String();
print(isoDate);