Validating a SWT Token REST WCF Service

Question

I'm currently working on a WPF client, which obtains a SWT token from Windows Azure AppFabric ACS. With this token I want to consume a RESTful WCF Service. I used this tutorial to obtain the SWT token and it works perfect. With the help of this MSDN tutorial I created the RESTful WCF service.

The problem is that the token may have the wrong format, because the token validator can't validate it (Error in the IsHMACValid method of the token validator, swtWithSignatur.Length == 1).

Example of a token with which I contact the server:

{"appliesTo":"http://localhost:7100/Service/Default.aspx","context":null,"created":1326996221,"expires":1326999821,"securityToken":"<?xml version="1.0" encoding="utf-16"?><wsse:BinarySecurityToken wsu:Id="uuid:74ba5667-04ea-4074-9544-aaafb570c648" ValueType="http://schemas.xmlsoap.org/ws/2009/11/swt-token-profile-1.0" EncodingType="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-soap-message-security-1.0#Base64Binary" xmlns:wsu="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-utility-1.0.xsd" xmlns:wsse="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-secext-1.0.xsd">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</wsse:BinarySecurityToken>","tokenType":"http://schemas.xmlsoap.org/ws/2009/11/swt-token-profile-1.0"}

In the Windows Azure Management Portal I've selected SWT as token format for my Relying Party Application. According to the first tutorial the format for the SWT token looks good, but the token validator won't accept it.

PS: If someone is trying the second tutorial (How To: Authenticate to a REST WCF Service Deployed to Windows Azure Using ACS): I think there is an error in point 11 in step 3, where you have to modify the web.config file (the system/webService section doesn't exist). The configuration should look something like this:

<?xml version="1.0"?>
<configuration>
  <system.webServer>
    <modules runAllManagedModulesForAllRequests="true">
      <add name="SWTModule" type="SecurityModule.SWTModule, SecurityModule" />
    </modules>
  </system.webServer>
</configuration>

Robar Robar · Accepted Answer · 2012-01-21T00:48:39

The token, which I sent to the server, had the wrong format. The above token is in a json format and contains a 'securityToken', which is encoded xml. With HttpUtility.UrlDecode and XMLReader it is possible to retrieve the base64 string. The base64 string of the above token is:

aHR0cCUzYSUyZiUyZnNjaGVtYXMueG1sc29hcC5vcmclMmZ3cyUyZjIwMDUlMmYwNSUyZmlkZW50aXR5JTJmY2xhaW1zJTJmZW1haWxhZGRyZXNzPXBhdHJpY2suZWNrZXIlNDBnbWFpbC5jb20maHR0cCUzYSUyZiUyZnNjaGVtYXMueG1sc29hcC5vcmclMmZ3cyUyZjIwMDUlMmYwNSUyZmlkZW50aXR5JTJmY2xhaW1zJTJmbmFtZT1QYXRyaWNrK0Vja2VyJmh0dHAlM2ElMmYlMmZzY2hlbWFzLnhtbHNvYXAub3JnJTJmd3MlMmYyMDA1JTJmMDUlMmZpZGVudGl0eSUyZmNsYWltcyUyZm5hbWVpZGVudGlmaWVyPWh0dHBzJTNhJTJmJTJmd3d3Lmdvb2dsZS5jb20lMmZhY2NvdW50cyUyZm84JTJmaWQlM2ZpZCUzZEFJdE9hd2xzM1doNlgwRFJ6d1BsdzU2a1R0WURmLVNNaDZxZFJtQSZodHRwJTNhJTJmJTJmc2NoZW1hcy5taWNyb3NvZnQuY29tJTJmYWNjZXNzY29udHJvbHNlcnZpY2UlMmYyMDEwJTJmMDclMmZjbGFpbXMlMmZpZGVudGl0eXByb3ZpZGVyPUdvb2dsZSZBdWRpZW5jZT1odHRwJTNhJTJmJTJmbG9jYWxob3N0JTNhNzEwMCUyZlNlcnZpY2UlMmZEZWZhdWx0LmFzcHgmRXhwaXJlc09uPTEzMjY5OTk4MjEmSXNzdWVyPWh0dHBzJTNhJTJmJTJmZmhiYXlhenVyZW5zLmFjY2Vzc2NvbnRyb2wud2luZG93cy5uZXQlMmYmSE1BQ1NIQTI1Nj1SUnN3OUJTSlc2ZFJ0MjJyNkNkcjZWZHpyJTJicTF6MHlhV0FMNVdlJTJiJTJmV3owJTNk

I decoded this string and got my ACS token. This ACS token is now valid and my RESTful WCF service can be used.

Code on the server side didn't changed. This is what I've got on the client side:

// parse the token from the json string, 
var token = JsonNotifyRequestSecurityTokenResponse.FromJson(txtReceivedToken.Text);
// get the security token and decode it
string xmlString = HttpUtility.UrlDecode(token.SecurityTokenString);
// get the base64 string an
string string64 = "";
using (XmlReader xmlReader = XmlReader.Create(new StringReader(xmlString))) {
  while (xmlReader.Read()) {
    if (xmlReader.NodeType == XmlNodeType.Text) { // find the first text element, which should be the base64 string
      string64 = xmlReader.Value;
      break;
    }
  }
}
// decode it
string acsToken = base64Decode(string64);

// set the header
string headerValue = string.Format("WRAP access_token=\"{0}\"", acsToken);
client.Headers.Add("Authorization", headerValue);
Stream stream = client.OpenRead(@"http://127.0.0.1:81/Service1.svc/users");

StreamReader reader = new StreamReader(stream);
String response = reader.ReadToEnd();

The base64Decode method i 'stole' from http://www.vbforums.com/showthread.php?t=287324. The JsonNotifyRequestSecurityTokenResponse.FromJson part i got from http://www.leastprivilege.com/ , but i think it could be parsed with any available JSON parser.

I don't know if it is the best solution, but it works for me.

Validating a SWT Token REST WCF Service

1 Answers