Web API 2 Basic Authentication and allow actions not marked [Authorize] - security

Question

I have been looking at Basic Authentication in Web Api2 and don’t seem to find an explanation for something I am confused about.
I created a web api application project with individual authentication in Visual studio 2017.
I have the default code
public class ValuesController : ApiController
{
public IEnumerable<string> Get()
{
return new string[] { "value1", "value2" };
}
public string Get(int id)
{
return "value";
}
}
I call these actions via postman, browser etc all good.
If I add the [Authorize] attribute to one of the methods I get 401 unauthorized response as expected.
So far so good.
I then add basic authentication by creating a class derived from AuthorizationFilterAttribute
public class BasicAuthenticationAttribute : AuthorizationFilterAttribute
{
public override void OnAuthorization(HttpActionContext actionContext)
{
var authHeader = actionContext.Request.Headers.Authorization;
if (authHeader != null)
{
var authenticationToken = actionContext.Request.Headers.Authorization.Parameter;
var decodedAuthenticationToken = Encoding.UTF8.GetString(Convert.FromBase64String(authenticationToken));
var usernamePasswordArray = decodedAuthenticationToken.Split(':');
var userName = usernamePasswordArray[0];
var password = usernamePasswordArray[1];
var isValid = userName == "ade" && password == "password";
if (isValid)
{
var principal = new GenericPrincipal(new GenericIdentity(userName), null);
HttpContext.Current.User = principal;
return;
}
}
}
HandleUnathorized(actionContext);
}
private static void HandleUnathorized(HttpActionContext actionContext)
{
actionContext.Response = actionContext.Request.CreateResponse(HttpStatusCode.Unauthorized);
actionContext.Response.Headers.Add("WWW-Authenticate", "Basic Scheme='Data' location = 'http://localhost:");
}
I register the filter in WebApiConfig.cs
config.Filters.Add(new BasicAuthenticationAttribute());
I use postman to call the action marked with [Authorize] and send with header Authorization: Basic YWRlOnBhc3N3b3Jk
The request is authorized and I get my action response. All good.
Now I call the action that is not marked with [Authorize] without a Authorization header from postman expecting to get a response but the OnAuthorization is called and obviously returns HandleUnathorized(actionContext); I only expected the OnAuthorization method to be called where an action is marked with [Authorize]
So now I am thinking what is the point of the [Authorize] attribute because OnAuthorization is called regardless so what is the point of marking actions [Authorize] attribute?
Secondly, I added the following method to my class
private static bool SkipAuthorization(HttpActionContext actionContext)
{
Contract.Assert(actionContext != null);
return actionContext.ActionDescriptor.GetCustomAttributes<AllowAnonymousAttribute>().Any()
|| actionContext.ControllerContext.ControllerDescriptor.GetCustomAttributes<AllowAnonymousAttribute>().Any();
}
I call this method at the beginning of OnAuthorization
if (SkipAuthorization(actionContext)) return;
If I mark my actions with [AllowAnonymous] it works.
If there is no [Authorize] attribute on the controller or specific actions then surely the OnAuthorization should also be skipped?
I just don't see the point of using [Authorize], I am clearly missing something here, am I doing something wrong or do I need to mark the actions with [AllowAnonymous] to exclude them.

Answer 1

If you are using [Authorize] attribute and windows authentication, then authorization will done automatically, you don't need to do any special configuration, but any special case if you need to override [Authorize] class then your class is like below,
Instead of inheriting AuthorizationFilterAttribute, you can
inherit AuthorizeAttribute
public class BasicAuthenticationAttribute : AuthorizeAttribute
{
//your override methods
}
Instead of using [Authorize] attribute, use your derived class name. In your case use [BasicAuthenticationAttribute], not [Authorize]

Answer 2

Thanks Fran you set me off on the right path.
I commented out the following line
config.Filters.Add(new BasicAuthenticationAttribute());
I used the following attributes in controller
public class ValuesController : ApiController
{
public IEnumerable<string> Get()
{
return new string[] { "value1", "value2" };
}
[Authorize]
[BasicAuthentication]
public string Get(int id)
{
return "value";
}
}
If I called the action get() I got a response, OnAuthorisation was not called.
If I call get(int id) I get 401 Unauthorised and OnAuthorisation is not called.
I removed the [Authorize] from get(int id) action
[BasicAuthentication]
public string Get(int id)
{
return "value";
}
and it all worked, OnAuthorisation was called as expected.