ASP.NET MVC 5 でのユーザーごとの画像フォルダー

<!-- true: each signed-in user gets uploads/users/<id>/ (see RteFiles.RootFor) -->
<add key="rte:PerUserFolders" value="false" />

// The storage root for this request, as an app-relative virtual path. Files are written
// to Server.MapPath(root) and served from the same URL, so it stays inside ~/uploads,
// which web.config locks down to static files only.
//
// Default: one shared folder. With <add key="rte:PerUserFolders" value="true" /> in
// web.config, every signed-in user gets ~/uploads/users/<id>/ and anonymous requests get
// 401. /uploads/... is still a public URL: per-user roots keep users out of each other's
// folders in the dialog, they do not make the files private.
public static string RootFor(HttpContextBase context)
{
    if (WebConfigurationManager.AppSettings["rte:PerUserFolders"] != "true")
        return "~/uploads";

    IPrincipal user = context.User;
    if (user == null || !user.Identity.IsAuthenticated)
        throw new RteException(401, "Sign in to use the image gallery.");
    return "~/uploads/users/" + FolderIdFor(user.Identity.Name);
}

// A folder name for a user: the same user always gets the same folder, and nothing the
// user typed reaches the disk path (a name like "DOMAIN\bob" or "a@b.com" is not a folder name).
// If your users have a numeric id in your database, return that instead.
static string FolderIdFor(string userName)
{
    using (SHA256 sha = SHA256.Create())
    {
        byte[] hash = sha.ComputeHash(Encoding.UTF8.GetBytes(userName.ToLowerInvariant()));
        return BitConverter.ToString(hash, 0, 8).Replace("-", "").ToLowerInvariant();
    }
}

// Json() refuses GET unless told otherwise (JsonRequestBehavior.DenyGet is the default)
// and caps output at 2,097,152 characters; both are lifted here. Property names are
// written as declared, so the anonymous objects in RteFiles produce camelCase JSON.
JsonResult JsonStatus(int status, object data)
{
    Response.StatusCode = status;
    // Without this, IIS replaces 4xx bodies with its own error page for remote users.
    Response.TrySkipIisCustomErrors = true;
    // Forms authentication would turn a 401 into a 302 to the login page; keep the 401.
    Response.SuppressFormsAuthenticationRedirect = true;
    Response.Cache.SetCacheability(HttpCacheability.NoCache);
    Response.Cache.SetNoStore();
    return new JsonResult
    {
        Data = data,
        JsonRequestBehavior = JsonRequestBehavior.AllowGet,
        MaxJsonLength = int.MaxValue
    };
}

<!-- Any ASP.NET sign-in works (Forms, Windows, OWIN cookies): RootFor only reads
     HttpContext.User. AccountController.SignIn is a demo stand-in for your real login. -->
<authentication mode="Forms">
  <forms loginUrl="~/Account/SignIn" name=".RTEDEMO" />
</authentication>

curl -i "http://localhost:5402/rte/gallery?folder="
HTTP/1.1 401 Unauthorized
{"error":"Sign in to use the image gallery."}