I originally used static variables to store some user information when a user is browsing my site. I had issues where occasionally a user would navigate somewhere and see a different users name on the page. I switched to using session variables to solve this, but the same problem occurred. I then thought making the session variable names unique in some way would solve the problem, e.g. instead of
Session["userId"]
I changed all session variables to append the unique username of the user when they are created and referenced, so they are:
Session["userId" + Context.Identity.User.Name.ToString()]
So far I've had no reports of the issue, but is this actually going to work? Is there a simple way to protect sessions so the variables don't leak between users? I'm confident with ASP.NET code (webforms specifically) but have only encountered the session issue as more users use the site. I don't have much control over IIS settings as the site is built via AWS Elastic Beanstalk, so it's mostly default IIS settings.
This should work fine, but I suggest storing username or user profile information in cookies or local storage since as you mentioned when lot of users logged in it maintains session for them on server memory(I believe session is in-memory by default not in-proc or redis). This is not scalable as if millions of user logged in or you create load test server considerable memory will be taken by session management. Few hundred users however is not much overhead.
You can store information at user browser using sessionStorage like:
Setting value
sessionStorage.setItem("user_name", "test");
Getting Value
var userName = sessionStorage.getItem("user_name");
It can store javascript object or json too.
Cookies are old way to store info at user end :
Creating cookie
document.userCookie = "username=John Doe";
reading cookie
document.userCookie //"username=John Doe"
Forms authentication also provide encrypted & secured cookies which is maintained with session which is also good if user profile information is sensitive data.
Sorry, I can't write comments for your question, but:
Same issue happed to Java developer with AWS Elastic Beanstalk:
https://forums.aws.amazon.com/thread.jspa?threadID=84027
First, I suggest you try to set no-cache for your HttpResponse (temporary solution), than
I suggest you try to play with your IIS proxy settings.
If it didn't help (and you're using load balancer) - refuse from using inproc settings like in this topic:
User on wrong session
PS. You really don't have to make session variable names different - Session uniqueness is guaranteed by ASP.NET setting different Session_ID for each session.
Related
I'm using a login form to authenticate users.
FormsAuthentication is right out as it stores sensitive user/role membership in either client-side in a cookie or within the URL. Within the URL is a huge security risk, so I won't even get into that. With the
FormsAuthentication cookie, this creates problems with a) security where the client is in the position of dictating it's own roles; and b) way too much data stored in cookies. Since I'm gaining nothing through security and loosing out big time on the size of user data storage, I'd rather just work with Sessions.
I'd like to reuse something like FormsAuthentication for all its basic login form-handling features. But i would rather have it store user data server-side in perhaps Session rather than client-side all stuffed into a single cookie. I'd rather just authenticate against a Session token of some sort.
I have no database and local disk storage of user data is forbidden. I rely on a 3rd party authentication service provider, and a requirement is that I must reduce chatter with this service. Thus, sessions for temporary storage of user info. Sucks, but that's not necessarily the problem I'm asking about. Also, a requirement is that I must set/use HttpContext.user and likely Thread.CurrentPrincipal for use later on in such things as AuthorizeAttribute, for displaying user info in views, etc.
So FormsAuthentication stores all user data client-side in a cookie. Whereas Session stores all data server-side and just relies on a simple client-side token cookie. However, Session is not available anywhere during the asp.net startup and authentication steps. Is there an equivalent forms "membership" provider that stores all data in Session server-side instead of client-side?
If there is no Session equivalent...
Where do I set HttpContext.user and Thread.CurrentPrincipal to make both values available throughout the rest of both MVC apps without interfering or messing up other MVC components?
Hinging on #1, is Session available at that entry point? If not, how do I make it available so I can create the Principle/Identity object using the data stored in Session?
This can't possibly be a unique requirement. Are there libraries already available which handle this?
Session stores information in a client-side cookie too! (or in the URL if cookieless).
If you want to authenticate a client, he'll have to provide some kind of credentials - usually an encrypted token in a cookie once he has logged on. If not a cookie, then what do you propose?
You should use FormsAuthentication. The sensitive information stored in a client-side cookie is encrypted using a key that should only be known to the web server. "the encryption methods being public knowledge" doesn't mean that you can decrypt the data without access to the appropriate cryptographic key.
You mention "roles" and a "third-party authentication provider". If your third party is also providing roles (i.e. an "authorization provider" as well as an "authentication provider"), then it would be reasonable to cache roles obtained from the provider on the server. Session is not available when a request is being authorized, so the best solution is to use the Cache (System.Web.Caching.Cache).
Personally I would encapsulate this in a custom RoleProvider. The custom RoleProvider would implement GetRolesForUser by getting roles from the third party on the first call, then caching them in Cache.
Not sure if I like what I'm about to suggest, but you could do the following:
Leverage the Application State or System.Cache as a global storage for user credentials.
Use an InMemory database (like RavenDb) which can also have encryption (in memory, I believe).
Using the Application state as a place to storage relatively common / frequent stuff I think is not a great place because of
Scaling / locking issues? <-- just a gut feeling.
Permenant data? so you have users in the website's memory .. then the website crashes or recycles, etc... what happens now to that data?
RavenDb is awesomeballs - go.use.it.now.
I understand that you are not storing anything locally, so whenever a user hits your system, you need to refresh your inmemory cache, etc. Fine. A pain in the f'ing butt , but fine none-the-less. (EDIT: unless the data has been cached in memory .. that is)
Anywys, two suggestions.
ProTip:
Oh! move away from role based shiz and start using Claims based identity stuff. Yes, it still works with IPrincipal and HttpContext.User, etc. So all previous code is NOT busted. But now it's baked into .NET 4.5
Awesome Video on this for you, me, everyone!
Finally - bonus suggestion
A nice package that auth's with either Facebook/Google/Twitter. You said you're keeping the user cred's on another site (good move!). If you're using other providers, then stick with DNOA or SS.
GL!
For various reasons I am fed up with ASP.NET session state and I'm trying to do it myself (separate question coming soon related to why I'm fed up and whether it's feasible to do it myself, but for now let's assume that it is).
Security concerns aside, it seems like tracking sessions involves little more than storing a cookie with a guid and associating that guid with a small "sessions" table in the database, which is keyed on the guid and contains a small number of fields to track timeout and to link to the primary key in the user's table, for those sessions that are linked to registered users.
But I'm stuck on a detail with the cookie, in the case the user's browser is not set to accept cookies. It seems to me that each time a user accesses any page that has session state enabled, ASP.NET must determine whether the browser supports cookies. If there already is a session cookie sent with the request, obviously it knows cookies are accepted.
If not, it seems like it needs to check, which as I understand it involves trying to write a cookie and redirecting to a page that tries to read the cookie. So it seems, when a user with cookies turned off visits several pages of a site, that ASP.NET
(a) has to do this round-trip test for every page the user visits, or
(b) has to assume the browser accepts cookies and create a record with a (provisional) session id for the user on each page -- and if session state is supposed to be persistent, it seems it has to write that initial session id to the database on each page.
But (a) sounds crazy and (b) sounds crazy also, since we would quickly accumulate session ids for all these single-page sessions. So I'm thinking there must be some other trick/heuristic that is used to know when to do the round-trip test and/or when to actually create a record for the session.
Am I wrong to be perplexed?
(To be clear, I'm not talking about implementing a custom storage solution within ASP.NET's pluggable session state system. I'm talking about skipping ASP.NET's session state system entirely. My question is a more detailed version of this one: Implementing own Session Management in ASP.NET.)
Session behaviour is set through the sessionState element in web.config. In the sessionState element the HttpCookieMode can be set to one of UseUri, UseCookies, AutoDetect, UseDeviceProfile.
UseUri and UseCookies tell ASP.NET explicitly how to handle storing the session identifier. If UseDeviceProfile is used then the behavior is determined by whether the user agent supports cookies (not whether they are enabled or not).
AutoDetect is the interesting case that you are interested in. How ASP.NET is handling the auto detection is explained in Understand How the ASP.NET Cookieless Feature Works. In that article you will see that they have 5 different checks they do. One of the checks is, as you mention, to set a cookie and do a redirect to see if the cookie exists. If the cookie exists, then the browser supports cookies and the sessionID cookie is set. However, this is not done on every request because another check they do before tring to redirect is is check to for the existence of any cookies. Since after the initial set-cookie and redirect the sessionID cookie will be set then the existence of the cookie lets ASP.NET know that cookies are supported and no further set-cookie and redirects are required.
Well, cookies are a standard mechanism of web authentication. Do you have any reason at all why you wouldn't want to use them? Are you sure you're not trying to invent a problem where there isn't any problem?
Most serious websites I know of require the browser to accept cookies in order for the user to be authenticated. It's safe to assume that every modern browser supports them.
There's an interesting article about cookieless ASP.NET that you should read.
EDIT:
#o.k.w: By default the session state is kept by ASP.NET in-process (read: in memory). Unless told explicitly by the configuration to store the session in the database (SQL Server is supported out-of-the-box), this won't result in a database hit. The stale session states will get purged from the in-process storage. Unfortunately, with default ASP.NET settings every cookieless request will result in a new session being created.
Here's a detailed comparison of available session storage options: http://msdn.microsoft.com/en-us/library/ms178586.aspx.
I'm porting an ASP.NET application to MVC and need to store two items relating to an authenitcated user: a list of roles and a list of visible item IDs, to determine what the user can or cannot see.
We've used WSE with a web service in the past and this made things unbelievably complex and impossible to debug properly. Now we're ditching the web service I was looking foward to drastically simplifying the solution simply to store these things in the session. A colleague suggested using the roles and membership providers but on looking into this I've found a number of problems:
a) It suffers from similar but different problems to WSE in that it has to be used in a very constrained way maing it tricky even to write tests;
b) The only caching option for the RolesProvider is based on cookies which we've rejected on security grounds;
c) It introduces no end of complications and extra unwanted baggage;
All we want to do, in a nutshell, is store two string variables in a user's session or something equivalent in a secure way and refer to them when we need to. What seems to be a ten minute job has so far taken several days of investigation and to compound the problem we have now discovered that session IDs can apparently be faked, see
http://blogs.sans.org/appsecstreetfighter/2009/06/14/session-attacks-and-aspnet-part-1/
I'm left thinking there is no easy way to do this very simple job, but I find that impossible to believe.
Could anyone:
a) provide simple information on how to make ASP.NET MVC sessions secure as I always believed they were?
b) suggest another simple way to store these two string variables for a logged in user's roles etc. without having to replace one complex nightmare with another as described above?
Thank you.
Storing the user's role information in a server-side session is safe providing a session cannot be hijacked. Restating this more broadly, it does not matter where user role info is stored if an authenticated session is hijacked.
I advise not putting too much faith in the article you linked to, but the 2002 vintage report linked to from your link is of interest. Here are my take-aways:
Don't accept session IDs embedded in URLs.
Focus your time on eliminating cross site scripting dangers i.e. scan all user supplied data and parse out executable java script.
Issue cookies for complete domains (e.g. myapp.mydomain.com)
Host your domain at a high class DNS operator e.g. one that only allows DNS changes from a preset remote IP address.
Don't issue persistent session cookies.
Reissue a session cookie if someone arrives at a login page with a sessionID already associated with an authenticated session.
Better still, always issue a new session cookie on successful authentication and abandon the prior session. (Can this be configured in IIS?)
The only way to make a secure cinnection is to use SSL. Anything less than that, and you simply have to make the evaluation when it's "safe enough".
A session variable works fine for storing a value, with the exception that the web server may be recycled now and then, which will cause the session to be lost. When that happens you would have to re-authenticate the user and set the session variable again.
The session variable itself is completely safe in the sense that it never leaves the server unless you specifically copy it to a response.
Have you considered setting up a custom Authorize tag in MVC. I gave an example of this in another question.
On initial authorization (sign-in screen or session start) you could seed a session value with the IP address also. Then in your custom authorization, you could also verify that IP's still match up as well. This will help make sure that someone isn't 'stealing' the person's session. Everytime you access your session data just make sure to pass the requester's IP and have some check on it.
Are you trying to control the access to functions at the client level? That is the only reason I would expose the roles and items to control client side functions.
Alternatively, you could create a function to obtain the items that the roles of the user are allowed to use, and then even if the function is called outside of the items given back to the web application, you can prevent the user from accessing them.
4Guys seems to show how to control functions with the roles.
The approach I have used in the past is to use symmetric encryption of a cookie alongside SSL. Encrypt the user information in the reponse and decrypt it in the request. I'm not claiming this is foolproof or 100% secure and I wouldn't want to do this on a banking application, but it is good enough for many purposes.
The main issue with session variables is that if you store them inProc rather than persisting them, then you need to apply 'sticky' sessions to your load balancing in a web farm environment. Guffa is correct that without this persistence session variables will occasionally be lost causing a poor user experience.
Sticky sessions can lead to uneven load balancing, perhaps reducing the value of being able to scale out.
If you are going to be be persisting the sessions so they can be accessed by all servers in your web farm, you may be better off using a Guid to identify the user, encrypting this in a cookie and retrieving the user record from your data store each time.
My obvious question is that why do you want to store a users role in session ?
Here is my answer to your query, how this helps. I have attached a small demo application for you to take a look at and understand my points. When you open this project in visual studio, click on the project tab on the top and select asp.net configuration. From the page that will show up you can do the user administration stuff.
You need to store the roles of a user in some secure manner ? The answer to this question is that there is no need for you to worry about storing the role for any user, when we have the asp.net membership, profiles and roles framework to help us out on this. All you need to do is create a role in the aspnet database and assign that role to the user.
Next you want to store two string in some secure manner. I suggest you user profile for storing user specific information. This way you have the information available to you where ever you want from the profilecommon class.
Also please see the attached demo application placed at the end of my blog http://blogs.bootcampedu.com/blog/post/Reply-to-httpstackoverflowcomquestions1672007user-roles-why-not-store-in-session.aspx
Just a suggestion, you might consider using this little library:
http://www.codeproject.com/KB/aspnet/Univar.aspx
It has a server side implementation of the cookie whereby all cookies can be stored on the server while asp.net authentification is used to identify the user. It supports encryption and is also very flexible making it very easy to switch from one storage type to another.
Is it possible to hack someone's session variables and create a new shadow user?
What are the common ways of avoiding such surprizes?
SSL certificate installation or ....?
Short answer... it depends.
Session in ASP.NET can be stored in a variety of ways (InProc / SQL Server / State Server) etc... another thing to note is how the client session is maintained (query string value, cookies etc...)
As the poster in this answer suggests
Can we hack a site that just stores the username as a session variable?
One thing you could do when you authenticate the user and store their name in Session, would be to also store some other information about them. e.g. Their UserAgentString, their IP Address and if a different IP or UserAgentString attempted to interact with the session, you could invalidate it.
Anything is possible, however by default it's hard.
Generally you hijack a session by stealing the session cookie and recreating it on another machine. However in order to do this the web site must be vulnerable to Cross Site Scripting (which you can mitigate against with Server.HtmlEncode when you echo user input back). If if you do end up vulnerable the ASP.NET session cookie is marked as HTTP Only, which means, if a browser supports it, it is not accessible to access from client side scripts (although Safari ignores this setting).
I am trying to achieve anonymous personalization in a ASP.net environment. I know that ASP.NET 2.0 provide Profile. However, I want to avoid traffic to the database as much as possible since the site I am working on is a relatively high traffic site.
The other obvious solution is cookie, but given the limitation of cookie, I was wondering if anyone have any efficient method to store information into cookie. Does anyone know how amazon or yahoo deals anon. personalization?
Ultimately, We are trying to serve up different dynamic content to our user base on a set of business rules outline in a pre-defined campaign. The reason is to measure conversion rate in our site. The same campaign can be use on all different pages of the site. The reason I need to set this to a cookie is that the user is able to see the same content served up previously if we want it to be. So this is what I have in cookie right now.
campaign code:page id:result display
And you can see that this will build up if there is a lot of campaign and each campaign is used on many pages.
Thanks in advance!
If database load is an issue, you can retrieve the personalization when the user starts his session on the website, and then store it on the session state. This way, only the first page load will make a call to the database.
You can store the user ID in the cookie.
Just remember to persist the session in the db when the user updates his preferences, and deleting old db records after a while might be a good idea too if that many anonymous users will visit your website.
If you want to persist the changes, such as each campaign view, there really isn't any way around accessing to write those changes. ASP.NET Membership is not bad on a high-volume site (>1 mil a day), when used correctly. For instance, you should be wrapping calls to the membership provider in a cached object, and refresh often (short expiration). Also, make sure to set the cacheRefreshInterval on the RoleProvider. This will force asp.net to cache the Roles in a cookie, to cut down on DB activity.
Another way to look at this is to take Ady's advice and to seperate the Membership into a separate DB. Yet again, another great feature of the ASP.NET Membership provider - you can set a different SQL connection string, and load it up on a different DB and/or server.
There are several other techniques around the membership provider that can really increase performance. Some quick google searches comes up a number of them.
I'd create a database record for the visitor and only store the ID in the cookie, this way you can look up all the personalised details from the database, and keep the cookie size to a minimum.
If database speed is an issue, perhaps use a differrent database and server to store the personalisations.
Alternativly you could store personal data in the file system, and load into the session when the visitor returns matching the cookie ID.
If identifying the user and cookie clearing is an issue, you cold use and ActiveX control, but this requires installation on the client computer, which people could object to.