Custom AuthorizeAttribute with custom authentication

Question

I am using ASP.NET MVC 4 Web application as a front-end for some WCF services. All the user log in/log out and session control is done on the back-end. MVC app should only

Answer 1

Here is how I did it for now:

  public class MyAuthorizeAttribute : AuthorizeAttribute
    {
        public override void OnAuthorization(AuthorizationContext filterContext)
        {
            bool authorized = false;

            /// MVC 4 boilerplate code follows
            if (filterContext == null)
                throw new ArgumentNullException("filterContext");

            bool skipAuthorization = filterContext.ActionDescriptor.IsDefined(typeof(AllowAnonymousAttribute), inherit: true)
                          || filterContext.ActionDescriptor.ControllerDescriptor.IsDefined(typeof(AllowAnonymousAttribute), inherit: true);

            if (skipAuthorization)
            {
                return;
            }

            if (OutputCacheAttribute.IsChildActionCacheActive(filterContext))
            {
                throw new InvalidOperationException(
                    "MyAuthorizeAttribute cannot be used within a child action caching block."
                );
            }
            // end of MVC code


            // custom code
            if (!AuthorizeCore(filterContext.HttpContext))
            {
                // if not authorized from some other Action call, let's try extracting user data from custom encrypted cookie
                var identity = MyEncryptedCookieHelper.GetFrontendIdentity(filterContext.HttpContext.Request);
                // identity might be null if cookie not received
                if (identity == null)
                {
                    filterContext.HttpContext.User = new GenericPrincipal(new GenericIdentity(""), null);
                }
                else
                {
                    authorized = true;
                    filterContext.HttpContext.User = new MyFrontendPrincipal(identity);
                }

                // make sure the Principal's are in sync - there might be situations when they are not!
                Thread.CurrentPrincipal = filterContext.HttpContext.User;
            }

            // MVC 4 boilerplate code follows
            if (authorized)
            {
                // ** IMPORTANT **
                // Since we're performing authorization at the action level, the authorization code runs
                // after the output caching module. In the worst case this could allow an authorized user
                // to cause the page to be cached, then an unauthorized user would later be served the
                // cached page. We work around this by telling proxies not to cache the sensitive page,
                // then we hook our custom authorization code into the caching mechanism so that we have
                // the final say on whether a page should be served from the cache.

                HttpCachePolicyBase cachePolicy = filterContext.HttpContext.Response.Cache;
                cachePolicy.SetProxyMaxAge(new TimeSpan(0));
                cachePolicy.AddValidationCallback(CacheValidateHandler, null /* data */);
            }
            else
            {
                HandleUnauthorizedRequest(filterContext);
            }
            //end of MVC code
        }

        protected override bool AuthorizeCore(HttpContextBase httpContext)
        {
            if (httpContext == null)
                throw new ArgumentNullException("httpContext");

            // check to make sure the user is authenticated as my custom identity
            var principal = httpContext.User as MyFrontendPrincipal;
            if (principal == null)
                return false;

            var identity = principal.Identity as MyFrontendIdentity;
            if (identity == null)
                return false;

            return true;
        }

        protected override void HandleUnauthorizedRequest(AuthorizationContext filterContext)
        {            
            // default MVC result was:
            // filterContext.Result = new HttpUnauthorizedResult();

            // but I redirect to index login page instead of kicking 401
            filterContext.Result = new RedirectResult("/Home/Index/NeedsLogin");
        }

        // MVC 4 boilerplate code follows
        private void CacheValidateHandler(HttpContext context, object data, ref HttpValidationStatus validationStatus)
        {
            validationStatus = OnCacheAuthorization(new HttpContextWrapper(context));
        }

        // This method must be thread-safe since it is called by the caching module.
        protected virtual HttpValidationStatus OnCacheAuthorization(HttpContextBase httpContext)
        {
            if (httpContext == null)
                throw new ArgumentNullException("httpContext");

            bool isAuthorized = AuthorizeCore(httpContext);
            return (isAuthorized) ? HttpValidationStatus.Valid : HttpValidationStatus.IgnoreThisRequest;
        }
    } 

It does not handle my 3rd scenario, though, so I'll implement it in a global error handler.