Return more info to the client using OAuth Bearer Tokens Generation and Owin in WebApi

I have created a WebApi and a Cordova application. I am using HTTP requests to communicate between the Cordova application and the WebAPI. In the WebAPI, I've implemented OAuth Bearer Token Generation.

public void ConfigureOAuth(IAppBuilder app)
    {
        var oAuthServerOptions = new OAuthAuthorizationServerOptions
        {
            AllowInsecureHttp = true,
            TokenEndpointPath = new PathString("/token"),
            AccessTokenExpireTimeSpan = TimeSpan.FromDays(1),
            Provider = new SimpleAuthorizationServerProvider(new UserService(new Repository<User>(new RabbitApiObjectContext()), new EncryptionService()))
        };

        // Token Generation
        app.UseOAuthAuthorizationServer(oAuthServerOptions);
        app.UseOAuthBearerAuthentication(new OAuthBearerAuthenticationOptions());

    }

and this is inside the SimpleAuthorizationServerProvider implementation

 public override async Task GrantResourceOwnerCredentials(OAuthGrantResourceOwnerCredentialsContext context)
    {
       context.OwinContext.Response.Headers.Add("Access-Control-Allow-Origin", new[] { "*" });

        // A little hack. context.UserName contains the email
        var user = await _userService.GetUserByEmailAndPassword(context.UserName, context.Password);

        if (user == null)
        {
            context.SetError("invalid_grant", "Wrong email or password.");
            return;
        }

        var identity = new ClaimsIdentity(context.Options.AuthenticationType);
        identity.AddClaim(new Claim("sub", context.UserName));
        identity.AddClaim(new Claim("role", "user"));

        context.Validated(identity);
    }

after a successful login request to the API from the Cordova app, I receive the following JSON

{"access_token":"some token","token_type":"bearer","expires_in":86399}

The problem is, that I require more information about the user. For example, I have a UserGuid field in the database and I want to send it to the Cordova app when the login is successful and to use it later in other requests. Can I include other information to return to the client, other than "access_token", "token_type" and "expires_in"? If not, how can I get the user in the API based on the access_token?

EDIT:

I think that I found a workaround. I added the following code inside GrantResourceOwnerCredentials

identity.AddClaim(new Claim(ClaimTypes.Name, user.UserGuid.ToString()));

and after that, I access the GUID inside my controller like this: User.Identity.Name

I also can add the the guid with a custom name identity.AddClaim(new Claim("guid", user.UserGuid.ToString()));

I'm still interested to know if there is a way to return more data to the client with the bearer token JSON.

You can add as many claims as you want.
You can add the standard set of claims from System.Security.Claims or create your own.
Claims will be encrypted in your token so they will only be accessed from the resource server.

If you want your client to be able to read extended properties of your token you have another option: AuthenticationProperties.

Let's say you want to add something so that your client can have access to. That's the way to go:

var props = new AuthenticationProperties(new Dictionary<string, string>
{
    { 
        "surname", "Smith"
    },
    { 
        "age", "20"
    },
    { 
    "gender", "Male"
    }
});

Now you can create a ticket with the properties you've added above:

var ticket = new AuthenticationTicket(identity, props);
context.Validated(ticket);

That's the result your client will fetch:

.expires: "Tue, 14 Oct 2014 20:42:52 GMT"
.issued: "Tue, 14 Oct 2014 20:12:52 GMT"
access_token: "blahblahblah"
expires_in: 1799
age: "20"
gender: "Male"
surname: "Smith"
token_type: "bearer"

On the other hand if you add claims you will be able to read them in your resource server in your API controller:

public IHttpActionResult Get()
{
    ClaimsPrincipal principal = Request.GetRequestContext().Principal as ClaimsPrincipal;

    return Ok();
}

Your ClaimsPrincipal will contain your new claim's guid which you've added here:

identity.AddClaim(new Claim("guid", user.UserGuid.ToString()));

If you want to know more about owin, bearer tokens and web api there's a really good tutorial here and this article will help you to grasp all the concepts behind Authorization Server and Resource Server.

UPDATE:

You can find a working example here. This is a Web Api + Owin self-hosted.
There's no database involved here. The client is a console application (there's a html + JavaScript sample as well) which call a Web Api passing credentials.

As Taiseer suggested, you need to override TokenEndpoint:

public override Task TokenEndpoint(OAuthTokenEndpointContext context)
{
    foreach (KeyValuePair<string, string> property in context.Properties.Dictionary)
    {
        context.AdditionalResponseParameters.Add(property.Key, property.Value);
    }

    return Task.FromResult<object>(null);
}

Enable 'Multiple Startup Projects' from Solution -> Properties and you can run it straight away.

My recommendation is not to add extra claims to the token if not needed, because will increase the size of the token and you will keep sending it with each request. As LeftyX advised add them as properties but make sure you override TokenEndPoint method to get those properties as a response when you obtain the token successfully, without this end point the properties will not return in the response.

 public override Task TokenEndpoint(OAuthTokenEndpointContext context)
    {
        foreach (KeyValuePair<string, string> property in context.Properties.Dictionary)
        {
            context.AdditionalResponseParameters.Add(property.Key, property.Value);
        }

        return Task.FromResult<object>(null);
    }

You can check my repo here for complete example. Hope it will help.