Is there a way to remove the authentication cookie, or sign a user out once they are removed from the asp.net membership database? By default if a user is removed from the database, the user can still browse the website since they still have a valid authentication cookie.
I've tried different things within global.asax but nothing seems to work. Is something like this even possible?
See here: FormsAuthentication.SignOut Method. Although this refers to users not being logged out server side, a similar approach can be used for managing deleted users.
Calling the SignOut method only removes the forms authentication cookie. The Web server does not store valid and expired authentication tickets for later comparison. This makes your site vulnerable to a replay attack if a malicious user obtains a valid forms authentication cookie. To improve security when using a forms authentication cookie, you should do the following:
Use absolute expiration for forms authentication cookies by setting the SlidingExpiration property to false. This limits the window in which a hijacked cookie can be replayed.
Only issue and accept authentication cookies over Secure Sockets Layer (SSL), by setting the RequireSSL property to true and by running the entire Web site under SSL. Setting the RequireSSL property to true ensures that ASP.NET will never send an authentication cookie to the browser over a non-SSL connection; however, the client might not honor the secure setting on the cookie. This means the client might send the forms authentication cookie over a non-SSL connection, thus leaving it vulnerable to hijack. You can prevent a client from sending the forms authentication cookie in the clear by running the entire Web site under SSL.
Use persistent storage on the server to record when a user logs out of the Web site, and then use an application event such as PostAuthenticateRequest event to determine whether the current user was authenticated with forms authentication. If the user was authenticated with forms authentication, and if the information in persistent storage indicates the user is logged out, immediately clear the authentication cookie and redirect the browser back to the login page. After a successful login, update storage to reflect that the user is logged in. When you use this method, your application must track the logged-in status of the user, and must force idle users to log out.
The third option is the most secure but requires the most effort. IMO, the first two do not resolve the issue adequately.
It is also possible to store custom information in the Forms Authentication Ticket. You could store the last explicit logout time in this ticket, and check it against your server side database record. Please note that if this record is at user level instead of session, then all logins under that account would be logged out at the same time.
In your case, if you are deleting server side user and session records, as the record does not exist you will be able to also fail the authentication request.
I'd advise also storing and checking the last date/time the password was changed - that way if a user updates their password then all existing sessions are logged out.
Related
It is a Plain ASP.NET application using SQL Membership Provider for authentication. While application runs good most of the time. We have recently seeing complains from users saying they are seeing other users account.
I am pretty sure & confirmed again I directly consume HttpContext.Current.User.Identity.Name in the code to get user information. So under heavy load I get different user name returned.
Has anyone faced similar issue ? Have possible cause ?
Application Runs in ASP.NET 4.0, Web Forms , No caching ,Not handled any cookies in code, no Javascripts that is sniffing cookies.
I see these two links taking about same but no answers posted.
http://bytes.com/topic/asp-net/answers/324385-serious-issue-httpcontext-current-user-identity-name
http://www.experts-exchange.com/Web_Development/Miscellaneous/Q_21105924.html
Forms Authentication shouldn't be related to Membership provider too much.
FormsAuthentication saves signed user information into .ASPXAUTH cookie. And when next request comes to server, it decrypts cookie value and set it back to HttpContext.Current.User.Identity.Name. It uses MachineKey for encryption\decription. Then it creates FormsIdentity object based on FormsAuthenticationTicket object that holds username. So, your userName is stored on client. And whole this process doesn't include usage of Membership provider.
Forms Authentication uses Membership only when you do login for user, and then based on logged in user FormsAuthentication creates a cookie with UserName.
About your problem, you need to check .ASPXAUTH cookie value for those requests who has invalid UserName. You can try to log cookie information for these bad requests, and then you can decrypt them to get userName info from request. Or if you can reproduce it locally you can disable Forms cookie encryption (protection element), and then check it's value for bad requests
Instead of using ASP.NET MVC User's system, I'm simply using session, as the following:
When he logs in (username + password), I fetch the corresponding user from the Database and set:
Session["UserId"] = fetchedUser.UserId;
Then, I'm always checking if he is logged in:
if (Session["UserId"] != null && ...)
The problem is that if someone copies the value of ASP.NET_SessionId from a logged in user (eg: user goes to bathroom and coworker who is sitten next to him checks his cookies with chrome inspector), then he will be able to create a cookie in his computer and act as that user.
My questions are:
Why are sessions safer than cookies if the session id is saved in a cookie?
Can I make this safer (and continue using session)?
How does internally ASP.NET User authetication system do it?
A primary reason for not using Session as an authentication mechanism is that it could render your application vulnerable to Session Fixation. For example, a problem could be if a user arrived on your site using the HTTP protocol and receives a session ID that is stored in the ASP.NET_SessionId cookie. The user may later log in, and even though your login pages might be secured under HTTPS the session token has already been generated under HTTP which means it has already been transported using cleartext.
To answer your other points:
Why are sessions safer than cookies if the session id is saved in a
cookie?
The data stored in session is stored server side, so it is more difficult for an attacker to tamper with this data. All the cookie stores is a token for this data, rather than the data itself. Having said that, it is still safer to use the FormsAuthenticationProvider as this creates a new authentication token once login is complete rather than on session start for the reasons of avoiding session fixation as above.
Can I make this safer (and continue using session)? How does
internally ASP.NET User authetication system do it?
The built in provider is already fit for purpose, so it would be desirable to use that rather than fudge another mechanism to meet your requirements. It is also easily extensible so you can customise it to your needs. The ASP.NET User Authentication creates an encrypted ticket and stores it in the cookie rather than storing a reference to a server side variable: http://support.microsoft.com/kb/910443
I would also draw your attention to the signout mechanism and how to secure it. Particularly
Calling the SignOut method only removes the forms authentication cookie. The Web server does not store valid and expired authentication tickets for later comparison. This makes your site vulnerable to a replay attack if a malicious user obtains a valid forms authentication cookie.
Details here: http://msdn.microsoft.com/en-us/library/system.web.security.formsauthentication.signout.aspx
In addition you may want to set the "secure" flag on your ASP auth cookie to prevent it being leaked over HTTP by a MITM attacker.
In asp.net, I am able to login using forms authentication as usual, copy our auth cookie value, log out, add the cookie artificially to the client using the 'Edit This Cookie' addon for Chrome, refresh the (anonymous) landing page and hey presto i'm logged in again. This seems to be a vulnerability - is there any way of fixing it using the the standard forms auth or will I have to do something like use a custom Authorize attribute which overrides the existing one in asp.net mvc?
I don't think this is a bug per se. The following happens during forms authentication
You provide a username/password to the server
Server validates username/password
If valid, the server then sends an encrypted authentication ticket (cookie) to the client with the expiration time (set in the web.config forms authentication section) and username (all encrypted)
On each request that requires authorization, the cookie is decrypted on the server, expiration time is checked and username is used to see if authorized (or getting that role for the requested resource).
When you logout, the expiration time on the cookie is set in the past, therefore, it is not longer a valid cookie
Now, as to why you are seeing what you are seeing... You are copying the cookie before you logout. Thus your copied cookie never registers the logout (moved expiration time). When you reattach, you still have a valid auth cookie. Now, if your forms authentication timeout is set to...let's say 20 minutes...this method would fail if you copy the cookie and wait 21 minutes as by that time, it has expired.
Cookies are always vulerable and we can't do much about that. What we can do is prevent someone from stealing the cookies.
Regarding ASP.NET MVC it does a good job to avoid stealing cookies. Some of the main things it does by default as part of security are:
Encode the strings that are rendered to the view (if you are using Razor don't know about others) to prevent from XSS attacks.
Request validation (stop potentially dangerous data ever reaching the
application).
Preventing GET access for JSON data.
Preventing CSRF Using the Antiforgery Helpers
Regarding cookies Microsoft provides HttpOnly feature and this helps to hide the cookies from javascript. The Forms authentication that you are talking about is a HttpOnly cookie means someone can't steal that through JavaScript and it's more safe.
You can do that with any cookie/s. You can inspect/copy all the cookies from any given domain, and spoof if you want. You can do that to yourself (only) because its your PC (or user logged in to PC). Obviously if you're on a shared PC, that is a problem (across all your info).
The act of "copying your cookie" is in fact one way malware attempts to steal/hijack your identity (or current session on some web site). That said, unless you have some malware, you can't just "copy cookies" of someone else.
Assuming logout is done, you can ask users to close their browsers so the expired cookie is removed from the (file) system.
I'm building web portal in ASP.NET MVC 3 that uses distant web service as only way to communicate with database. Web service has requirement to always have Username/Password passed in request header, otherwise it rejects the call.
I have overridden ASP.NET Membership so that my ValidateUser method sends Username/Password to web service Login method, and returns true/false if authentication is successful. It works quite nice with AcountController provided with MVC 3 Empty internet template. Since I have to pass Username/Password on every web service call, I'm saving them in Session.
My problem is:
If I close browser and reopen it... I remain logged to website, but my Session variables are expired, so none of my requests to web service are being accepted, even though I'm still logged with credentials.
I'm looking for nice suggestion how to sync user logged in state with session state. Either to keep them both persistent until log off is used or to have them both dispose on browser being closed.
Thanks for all suggestions :)
When the user signs in using your AccountController, try setting the auth cookie like this:
FormsAuthentication.SetAuthCookie(model.UserName, false);
This should tell ASP.NET to delete the cookie when the browser window is closed. Then, when user opens up a new browser, both the session and the auth cookie should both be destroyed.
Sessions are cookies on the client side. Forms Authentication (which uses your membership provider) also uses cookies.
They are different.
Is your auth ticket or cookie persistent? This MS KB will explain things and scenarios in more detail than I would here...
Hth.
I'm working on a website where I get a feed of usernames / hashed passwords from another service. When someone sucesfully logs in I set a forms authentication cookie with FormsAuthentication.SetAuthCookie.
My client doesn't like multiple people logged with the same credentials. They would like a log in to invalidate any currently logged in clients.
There isn't a method on FormsAuthentication to tell the server "invalidate any other cookie under this name". KB900111 suggests the server doesn't maintain a list of valid cookies. So my approach isn't sounding good.
What's the alternative? Time to ditch forms auth?
Not necessarily. Forms auth still provides quite a bit of baked-in functionality you might want. Maybe you can generate and issue a Guid the first time each user logs in, and store that on the server-side, and in a cookie (security ticket preferably). Every time a request is made, you check to make sure the user is using not only the correct credentials, but also the same machine and browser (based on the cookie you issued the user when the user logged in). You would of course have to make sure that your Guid expires at some point, and also make sure you clear it out when the user signs out.