Gets custom OAuth errors working

src/Umbraco.Web/ViewDataExtensions.cs

@@ -1,7 +1,11 @@
-using System;
+using Newtonsoft.Json;
+using System;
 using System.Collections.Generic;
 using System.Linq;
+using System.Text;
+using System.Web;
 using System.Web.Mvc;
+using Umbraco.Core;
 using Umbraco.Web.Security;
 
 namespace Umbraco.Web
@@ -21,6 +25,49 @@ namespace Umbraco.Web
             return true;
         }
 
+        /// <summary>
+        /// Copies data from a request cookie to view data and then clears the cookie in the response
+        /// </summary>
+        /// <param name="viewData"></param>
+        /// <param name="httpContext"></param>
+        /// <param name="cookieName"></param>
+        /// <returns></returns>
+        /// <remarks>
+        /// <para>
+        /// This is similar to TempData but in some cases we cannot use TempData which relies on the temp data provider and session.
+        /// The cookie value can either be a simple string value
+        /// </para>
+        /// </remarks>
+        internal static bool FromBase64CookieData<T>(this ViewDataDictionary viewData, HttpContextBase httpContext, string cookieName)
+        {
+            var hasCookie = httpContext.Request.HasCookie(cookieName);
+            if (!hasCookie) return false;
+
+            // get the cookie value
+            var cookieVal = httpContext.Request.GetCookieValue(cookieName);
+
+            if (cookieVal == null)
+                return false;
+
+            // ensure the cookie is expired (must be done after reading the value)
+            httpContext.ExpireCookie(cookieName);
+
+            if (cookieVal.IsNullOrWhiteSpace())
+                return false;
+
+            try
+            {
+                var decoded = Encoding.UTF8.GetString(Convert.FromBase64String(System.Net.WebUtility.UrlDecode(cookieVal)));
+                // deserialize to T and store in viewdata
+                viewData[cookieName] = JsonConvert.DeserializeObject<T>(decoded);
+                return true;
+            }
+            catch (Exception)
+            {
+                return false;
+            }
+        }
+
         public static string GetUmbracoPath(this ViewDataDictionary viewData)
         {
             return (string)viewData[TokenUmbracoPath];