Creating A Service Bus SAS Token and Consuming Relay in WinRT - wcf

Question

I have a Service Bus Relay (WCF SOAP) I want to consume in my Windows Store App. I have written the code to create a token as well as the client which is below.
The problem is that I get an AuthorizationFailedFault returned with a faultstring "InvalidSignature: The token has an invalid signature." And I can't figure it out.
My Create Token method:
private static string CreateSasToken()
{
TimeSpan sinceEpoch = DateTime.UtcNow - new DateTime(1970,1, 1);
var expiry = Convert.ToString((int)sinceEpoch.TotalSeconds + 3600);
string stringToSign = webUtility.UrlEncode(ServiceUri.AbsoluteUri) + "\n" + expiry;
string hashKey = Encoding.UTF8.GetBytes(Secret).ToString();
MacAlgorithmProvider macAlgorithmProvider = MacAlgorithmProvider.OpenAlgorithm(MacAlgorithmNames.HmacSha256);
BinaryStringEncoding encoding = BinaryStringEncoding.Utf8;
var messageBuffer = CryptographicBuffer.ConvertStringToBinary(stringToSign,encoding);
IBuffer keyBuffer = CryptographicBuffer.ConvertStringToBinary(hashKey,encoding);
CryptographicKey hmacKey = macAlgorithmProvider.CreateKey(keyBuffer);
IBuffer signedMessage = CryptographicEngine.Sign(hmacKey, messageBuffer);
string signature = CryptographicBuffer.EncodeToBase64String(signedMessage);
var sasToken = String.Format(CultureInfo.InvariantCulture,
"SharedAccessSignature sr={0}&sig={1}&se={2}&skn={3}",
WebUtility.UrlEncode(ServiceUri.AbsoluteUri),
WebUtility.UrlEncode(signature), expiry, Issuer);
return sasToken;
}
My Client class:
public partial class ServiceClient
{
public async Task<string> GetDataUsingDataContract(string item, string sasToken)
{
HttpClient client = new HttpClient();
client.DefaultRequestHeaders.Add("ServiceBusAuthorization",sasToken);
client.DefaultRequestHeaders.Add("SOAPAction",".../GetDataUsingDataContract");
client.DefaultRequestHeaders.Add("Host", "xxxxxxxxxxx.servicebus.windows.net");
HttpRequestMessage request = new HttpRequestMessage(HttpMethod.Post,ServiceUri);
var content =new StringContent(#"<s:Envelope
xmlns:s=""http://schemas.xmlsoap.org/soap/envelope/"">
<s:Header></s:Header><s:Body>"+ item +#"</s:Body>
</s:Envelope>",System.Text.Encoding.UTF8,"application/xml");
request.Content = content;
HttpResponseMessage wcfResponse = client.SendAsync(request).Result;
HttpContent stream = wcfResponse.Content;
var response = stream.ReadAsStringAsync();
var returnPacket = response.Result;
return returnPacket;
}
}
I have been successful consuming the Relay using Http (via Fiddler) by copying an unexpired token created by Micorosft.ServiceBus in a console app.

Answer 1

I figured out a solution which involved both methods being wrong.
CreateSasToken method:
A minor change involved setting the hashKey variable as byte[] and not string. This line:
string hashKey = Encoding.UTF8.GetBytes(Secret).ToString();
Changed to this:
var hashKey = Encoding.UTF8.GetBytes(Secret);
This change meant that I needed to use a different method to set keyBuffer.
This line:
IBuffer keyBuffer = CryptographicBuffer.ConvertStringToBinary(hashKey,encoding);
Change to this:
IBuffer keyBuffer = CryptographicBuffer.CreateFromByteArray(hashKey);
So the new CreateSasToken method is:
private static string GetSasToken()
{
TimeSpan sinceEpoch = DateTime.UtcNow - new DateTime(1970, 1, 1);
var expiry = Convert.ToString((int)sinceEpoch.TotalSeconds + 3600);
string stringToSign = WebUtility.UrlEncode(ServiceUri.AbsoluteUri) + "\n" + expiry;
var hashKey = Encoding.UTF8.GetBytes(Secret);
MacAlgorithmProvider macAlgorithmProvider =
MacAlgorithmProvider.OpenAlgorithm(MacAlgorithmNames.HmacSha256);
const BinaryStringEncoding encoding = BinaryStringEncoding.Utf8;
var messageBuffer = CryptographicBuffer.ConvertStringToBinary(stringToSign,
encoding);
IBuffer keyBuffer = CryptographicBuffer.CreateFromByteArray(hashKey);
CryptographicKey hmacKey = macAlgorithmProvider.CreateKey(keyBuffer);
IBuffer signedMessage = CryptographicEngine.Sign(hmacKey, messageBuffer);
string signature = CryptographicBuffer.EncodeToBase64String(signedMessage);
var sasToken = String.Format(CultureInfo.InvariantCulture,
"SharedAccessSignature sr={0}&sig={1}&se={2}&skn={3}",
WebUtility.UrlEncode(ServiceUri.AbsoluteUri),
WebUtility.UrlEncode(signature),
expiry, Issuer);
return sasToken;
}
Service Client Class
A couple of things to note here.
In order for the request to work, the SAS Token had to be added to the header as a parameter of a AuthenticationValueHeader object. So I added the following method to my helper class (ServiceBusHelper) which held the Key, KeyName and SasToken as properties and the CreateSasToken as a method.
public static AuthenticationHeaderValue CreateBasicHeader()
{
return new AuthenticationHeaderValue("Basic", SasToken);
}
The HttpRequestMessage Content property had to be created a special way. Taking the item parameter passed in, which was a serialized WCF DataContract type I needed to do a few things to make the SOAP envelope. Rather than go through them in detail here is the entire class (one method only). I will comment on the code to handle the response immediately following.
public partial class SalesNotifyServiceClient
{
public async Task<string> GetDataUsingDataContract(string item)
{
string returnPacket = "";
string element = "";
try
{
HttpClient client = new HttpClient();
client.DefaultRequestHeaders.Add("ServiceBusAuthorization",
ServiceBusHelper.CreateBasicHeader().Parameter);
client.DefaultRequestHeaders.Add("SOAPAction",
".../GetDataUsingDataContract");
client.DefaultRequestHeaders.Add("Host",
"xxxxxxxxxx.servicebus.windows.net");
HttpRequestMessage request = new HttpRequestMessage(HttpMethod.Post,
ServiceBusHelper.ServiceUri);
//Creating the request.Content
var encodedItem = item.Replace("<", "<").Replace(">", ">");
var strRequest =
#"<s:Envelope xmlns:s=""http://schemas.xmlsoap.org/soap/envelope/"">
<s:Header></s:Header><s:Body><GetDataUsingDataContract xmlns=
""http://www.xxxxxxxxxx.com/servicemodel/relay""><item>" +
encodedItem +
#"</item></GetDataUsingDataContract></s:Body></s:Envelope>";
var content = new StringContent(strRequest,
System.Text.Encoding.UTF8, "application/xml");
request.Content = content;
HttpResponseMessage wcfResponse = client.SendAsync(request).Result;
HttpContent stream = wcfResponse.Content;
var response = await stream.ReadAsStringAsync();
//Handling the response
XDocument doc;
using (StringReader s = new StringReader(response))
{
doc = XDocument.Load(s);
}
if (doc.Root != null)
{
element = doc.Root.Value;
}
returnPacket = element;
}
catch (Exception e)
{
var message = e.Message;
}
return returnPacket;
}
}
In order to get at the DataContract object I had to do a few things to the response string. As you can see at the //Handling the response comment above, using StringReader I loaded the returned SOAP envelope as a string into an XDocument and the root value was my serialized DataContract object. I then deserialized the returnPacket variable returned from the method had my response object.