OWIN Integration Testing with OAuth Bearer Tokens

Situation

The situation is pretty simple. We have a project written with Web API 2.2 that we have running with OWIN. The API requires user authorization. To accomplish that, we use the OWIN OAuth libraries.

Upon until recently, the OAuth authorization server (the thing that takes in the user credentials and issues the token) and the API (the resource server) were hosted in the same site and web project.

Integration testing was pretty easy at this point. For the authorized calls, we simply wrote helper methods that logged a test user in through the authorization server (hosted along with the API in the OWIN test server), got a bearer token and then made the integration test calls.

Problem

When we recently decided to split the authorization server and resource server code up into two separate code bases (so that they could be hosted separately) we ran into issues with the authorization and API calls no longer being possible within a single integration test. The code to generate the bearer token was now no longer accessible in the test server for the API integration tests because the authorization server was now designed to be hosted separately. We’d have to somehow generate the bearer token without making a call with the OWIN test server.

Solution

The solution is to generate a valid bearer token in your test code and send it along with your test API call as you would have previous. How to generate that valid bearer token though?? It turns out to be easier than I thought.

How you use OWIN’s test server is beyond the scope of this blog post, but eventually you’ll have some code resembling this:

var server = TestServer.Create();

You’ll have to use a overload of the Create() method to capture a reference to the server’s IDataProtector. This interface defines what OWIN OAuth will use to encrypt a ClaimsIdentity into a valid bearer token.

Update your server creation code like this:

  var dataProtector;
  var server = TestServer.Create(app =>
  {
    var s = new Startup();
    s.Configuration(app);

    dataProtector = app.CreateDataProtector(
      typeof(OAuthBearerAuthenticationMiddleware).Namespace,
      "Access_Token", "v1");
  });

You have to get the dataProtector this way because it’s the same way that the OWIN OAuth libraries get it before trying to decrypt the bearer token. See the source for the OWIN OAuth code here: OAuthBearerAuthenticationMiddleware.cs

Once you’ve “captured” the dataProtector, in your integration test (or in some helper code, probably) you can generate your ClaimsIdentity and then your bearer token with the dataProtector.

  // inside an integration test
  using (server)
  {
    // create your valid identity any way you need to here
    ClaimsIdentity identity = new ClaimsIdentity(new GenericIdentity("username"));

    // these classes are defined in the OWIN OAuth libraries.
    var properties = new AuthenticationProperties();
    var ticket = new AuthenticationTicket(identity, properties);
    var format = new TicketDataFormat(dataProtector);

    string bearerToken = format.Protect(ticket);

    // ... call your API through the test server with the bearer token...
    var response = server.CreateRequest("/api/someendpoint")
        .AddHeader("Authorization", "Bearer " + bearerToken)
        .GetAsync()
        .Result;
  }

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