Using Identity Server 3, ClaimsPrinciple null even after successful bearer token authentication - asp.net

Question

I have a test console app which I'm pointing at a local instance of Identity Server 3 to request an access token. The following code does this and returns my token fine (passing a single scope "scope.test.client").
static TokenResponse GetClientToken(string clientId, string clientSecret, string[] scopes)
{
var uri = new Uri(string.Concat(ID_BASE_URI, ID_URL_TOKEN));
var client = new TokenClient(
uri.AbsoluteUri,
clientId,
clientSecret);
return client.RequestClientCredentialsAsync(string.Join(" ", scopes)).Result;
I then use this token to call an API also running locally. This takes the TokenResponse obtained above and passed it to this method:
static void CallApi(string url, TokenResponse response)
{
try
{
using (var client = new HttpClient())
{
client.SetBearerToken(response.AccessToken);
Console.WriteLine(client.GetStringAsync(url).Result);
}
}
catch (Exception x)
{
Console.WriteLine(string.Format("Exception: {0}", x.Message));
}
}
The API (an ASP.NET WebApi project) uses an Owin Startup class to enforce bearer token authentication for all requests:
appBuilder.Map(baseApiUrl, inner =>
{
inner.UseWebApi(GlobalConfiguration.Configuration);
// Enforce bearer token authentication for all API requests
inner.UseIdentityServerBearerTokenAuthentication(new IdentityServerBearerTokenAuthenticationOptions
{
Authority = "https://identityserver/core",
ValidationMode = ValidationMode.ValidationEndpoint,
RequiredScopes = new[] { "scope.test.client" }
});
});
It also ensures all API requests are handled by a custom authorize attribute:
GlobalConfiguration.Configuration.Filters.Add(new DefaultApiAuthorizeAttribute());
Debugging this API, the first line in my overridden OnAuthorize method (in DefaultApiAuthorizeAttribute) is this:
var caller = actionContext.RequestContext.Principal as System.Security.Claims.ClaimsPrincipal;
If I break on this line I can see that actionContext.RequestContext.Principal is always null. However, I can see that ((System.Web.Http.Owin.OwinHttpRequestContext)actionContext.RequestContext).Request.Headers contains an Authorization header with the bearer token passed from my console app.
So it would seem that the API project is not authenticating the bearer token. Certainly the Identity Server logs suggest it isn't being hit at all after issuing the initial access token. So I'd appreciate your expert advice about why this might not be happening, or at least some pointers about where to look.
I suspect it might have something to do with SSL. Both sites are hosted locally under self-signed SSL certs, although Identity Server is configured to not require SSL and uses the idsrv3test.pfx development certificate for signing. I do have another test MVC web app which delegates authentication to the same IS3 instance which works fine locally, so I believe my IS3 instance is configured correctly.

Answer 1

You need to call UseIdentityServerBearerTokenAuthentication before you call UseWebApi. When you set up an OWIN Middleware Pipeline, the order is important.
In your case, Web API will be handling your requests before they get sent onto Identity Server (if they get sent on at all).

Answer 2

I imagine a range of possible issues could have the impact I described, but in my case I was able to find the cause by adding a diagnostics log to my consuming API. This led me to discover that the problem was an assembly conflict. The Owin middleware was looking for a Newtonsoft.JSON assembly with version 8.0.0.0 but my consuming API (actually running on top of a CMS intance) was using 7.0.0.0.
For anyone else who wants to find the answer fast, rather than spend hours tweaking configurations, here's the documentation that describes how to add this logging: https://identityserver.github.io/Documentation/docsv2/consuming/diagnostics.html