public Websocket()
{
Credentials = FetchCredentials();
string requestUrl = Sigv4util.getSignedurl(Credentials);
var factory = new MqttFactory();
mqttClient = factory.CreateMqttClient();
mqttClientOptions = new MqttClientOptionsBuilder().
WithWebSocketServer(requestUrl).
WithKeepAlivePeriod(TimeSpan.FromMinutes(10)).Build();
}
public static string getSignedurl(WebsocketCredentials credentials)
{
string requestUrl;
try
{
var requestDateTime = DateTime.UtcNow;
string datetime = requestDateTime.ToString(ISO8601BasicFormat, CultureInfo.InvariantCulture);
var date = requestDateTime.ToString(DateStringFormat, CultureInfo.InvariantCulture);
string method = "GET";
string protocol = "wss";
string uri = "/mqtt";
string service = "iotdevicegateway";
string algorithm = "AWS4-HMAC-SHA256";
string credentialScope = date + "/" + credentials.region + "/" + service + "/" + "aws4_request";
string canonicalQuerystring = "X-Amz-Algorithm=" + algorithm;
canonicalQuerystring += "&X-Amz-Credential=" + HttpHelper.UrlEncode(credentials.accessKey + '/' + credentialScope);
canonicalQuerystring += "&X-Amz-Date=" + datetime;
canonicalQuerystring += "&X-Amz-Expires=86400";
canonicalQuerystring += "&X-Amz-SignedHeaders=host";
string canonicalHeaders = "host:" + credentials.iotEndpoint + "\n";
var canonicalRequest = method + "\n" + uri + "\n" + canonicalQuerystring + "\n" + canonicalHeaders + "\n" + "host" + "\n" + EmptyBodySha256;
byte[] hashValueCanonicalRequest = CanonicalRequestHashAlgorithm.ComputeHash(Encoding.UTF8.GetBytes(canonicalRequest));
var builder = new StringBuilder();
for (int i = 0; i < hashValueCanonicalRequest.Length; i++)
{
builder.Append(hashValueCanonicalRequest[i].ToString("x2"));
}
string byteString = builder.ToString();
var stringToSign = algorithm + "\n" + datetime + "\n" + credentialScope + "\n" + byteString;
// compute the signing key
var keyedHashAlgorithm = KeyedHashAlgorithm.Create(HmacSha256);
keyedHashAlgorithm.Key = getSignatureKey(credentials.secretKey, date, credentials.region, service);
var signingKey = keyedHashAlgorithm.Key;
var signature = ComputeKeyedHash(HmacSha256, signingKey, Encoding.UTF8.GetBytes(stringToSign));
var signatureString = ToHexString(signature, true);
canonicalQuerystring += "&X-Amz-Signature=" + signatureString;
canonicalQuerystring += "&X-Amz-Security-Token=" + HttpHelper.UrlEncode(credentials.sessionToken);
requestUrl = protocol + "://" + credentials.iotEndpoint + uri + "?" + canonicalQuerystring;
}
catch (Exception e)
{
throw new Sigv4UtilException("Unable to get signed url", e);
}
return(requestUrl);
}
