I have the requirement that the end user should not be able to go back to the restricted page after logout/sign out. But currently the end user is able to do that by the browser back button, visiting browser history or even by re-entering the URL in browser's address bar.
Basically, I want that the end user should not be able to access the restricted page in any way after sign out. How can I achieve this the best? Can I disable the back button with JavaScript?
You can and should not disable the browser back button or history. That's bad for user experience. There are JavaScript hacks, but they are not reliable and will also not work when the client has JS disabled.
Your concrete problem is that the requested page is been loaded from the browser cache instead of straight from the server. This is essentially harmless, but indeed confusing to the enduser, because s/he incorrectly thinks that it's really coming from the server.
You just need to instruct the browser to not cache all the restricted JSP pages (and thus not only the logout page/action itself!). This way the browser is forced to request the page from the server instead of from the cache and hence all login checks on the server will be executed. You can do this using a Filter which sets the necessary response headers in the doFilter() method:
@WebFilter
public class NoCacheFilter implements Filter {
@Override
public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain) throws IOException, ServletException {
HttpServletResponse response = (HttpServletResponse) res;
response.setHeader("Cache-Control", "no-cache, no-store, must-revalidate"); // HTTP 1.1.
response.setHeader("Pragma", "no-cache"); // HTTP 1.0.
response.setDateHeader("Expires", 0); // Proxies.
chain.doFilter(req, res);
}
// ...
}
Map this Filter on an url-pattern of interest, for example *.jsp.
@WebFilter("*.jsp")
Or if you want to put this restriction on secured pages only, then you should specify an URL pattern which covers all those secured pages. For example, when they are all in the folder /app, then you need to specify the URL pattern of /app/*.
@WebFilter("/app/*")
Even more, you can do this job in the same Filter as where you're checking the presence of the logged-in user.
Don't forget to clear browser cache before testing! ;)
*.jsp in Url Pattern won't work if you forward a page. Try to include your servlet too.. that will make your application secure from this back button problem.
The simplest way to do it without disabling the browser back buton is by adding this code to the page_load event for the page that you don't want the user to go back to after logging out:
if (!IsPostBack)
{
if (Session["userId"] == null)
{
Response.Redirect("Login.aspx");
}
else
{
Response.ClearHeaders();
Response.ClearContent();
Response.Clear();
Session.Abandon();
Session.Remove("\\w+");
Response.AddHeader("Cache-Control", "no-cache, no-store, max-age = 0, must-revalidate");
Response.AddHeader("Pragma", "no-cache");
Response.AddHeader("Expires", "0");
}
}
The correct way to do this is to add the
Vary: Cookie
header on secured pages. When the user logs out, clear their session cookie. Then, when they navigate back after logging out, the browser cache will miss. This also has the benefit of not completely defeating caching.
You can try telling the browser not to cache the homepage (using the appropriate headers - Expires, Cache-Control, Pragma). But it is not guaranteed to work. What you can do, is make an ajax call to the server on page load to check if the user is logged, and if not - redirect.
