Given that session state is not reccomended in ASP.NET MVC. I'm trying to understand under what circumstances session is used. I know that using the TempData creates a session but what other circumstances are there and does it matter how I configure the session state timeout for better security?
<sessionState cookieName="s" timeout="20" />
The accepted answer you reference states in part
This tended to lead to an overuse of session, populating "current" variables in session intended to indicate what the current object being interacted with was. This overuse in turn made applications very state-dependent and much harder to determine expected behaviour ("Is this variable populated?" "Do I have the current order ID yet?").
MVC is structured around the idea that your website is a view into a logical model of information. It encourages having stateless operations through the use of simple controllers responding to actions with key information passed as part of the HTTP request
Session is not a bad thing when your website needs to tie certain content to a specific user, whether for security or personalization purposes. It is fine, expected and normal to use a session for that purpose.
What you should avoid doing is stuffing the session with any and all information that you might need anywhere in your web application. Take time to learn and understand the MVC architecture, and favor loading data that you need to render a given page when that page is actually being rendered. Only cache things that are relatively expensive to load, or are needed on many/all pages.
does it matter how I configure the session state timeout for better security?
The primary concern with session timeout periods is a session hijacking attack, which allows a man in the middle to intercept session information and control the session from a different device under control of the hacker. For most applications, I don't see anything wrong with the default session timeout.
The another concern is people that walk away from their device, leaving it unattended. People that do that have much greater security worries than just your website.
as you mentioned, it is true that session is not recommended in mvc . Because, in mvc identity is used to in identity there is no need for session.the data is stored in profile.
Session is used in such a condition when you want to maintain the value for multiple pages or multiple controllers. For ex, after, login you maintain the username and keep it until you remain in the application. While the tempdata is used to save or maintain value for the current action and the value is discarded after the next action
session state has no concern with security so there is no need to change the session time out value for the sake of security.
Related
This application is running in a load balanced environment. It uses a SQL database as the session store. The app is simple and does not have it's own database.
I have created an endpoint to be called from another internal server that knows the SessionId. I want this endpoint to be able to grab a session variable by SessionId instead of from the current session.
I know that I could create a new database to do this, but it would be overkill as it would only have 1 table with 2 fields, SessionId and the one value related to it. I could even put this table in the current session database. I am trying to avoid having to add database connection code if at all possible.
Is there a way to access the variables of a different session other than the current session?
I might be wrong and if I am - downvote; the fact that the session state storage is database-based (and not in-memory) does not change the principles of how the IHttpSessionState works. I doubt you will be able to do that and I doubt you actually want to: you simply cannot access an absolutely separate context from a different context. Doing so has a lot of potential issues (thread safety, problems if the session state implementation is changed and so on). Your web application might not be aware of the session state store.
For example, if I simply use session state and have the session state configured directly in IIS, there is no way for the application thread to know it's in the database which immediately presents an issue: what if I decide to run the same application without the DB-backed session state? No changes to application code are required, just IIS reconfiguration. It might introduce unexpected behavior and/or runtime errors.
The suggestion (in the comment) to set the cookie to the known session ID is the only "way out" but from the security perspective it's less than optimal.
However, what you are trying to implement seems like a proper job for a Cache Provider. You can use SqlCacheDependency from System.Web.Caching to use the database for your cache. Then you could use the aforementioned SessionId as one of the cache identifiers.
I currently am using a ConcurrentDictionary to hold a collection of login names that have authenticated with my API. I do this to prevent duplicate logins from other web clients (a requirement of the system architecture). If a user authenticates with a login that is already "logged in" they are given a choice ...
Continue and the previous login will be expired
Cancel and the current session will be logged out
I am using a ConcurrentDictionary because it is supposed to be thread safe which is important in an environment where multiple clients are accessing the API.
What I am asking is if the ConcurrentDictionary is needed because I am running into trouble deleting all items in the collection that match a given key. Is a ConcurrentDictionary called for in this case? If not, would a plain Dictionary suffice? If not, and a ConcurrentDictionary is needed is there a method that will remove all entries matching a given key? All I can see is TryRemove() which only seems to remove a single entry.
The direct answer to your question:
Yes, you need a ConcurrentDictionary. You are sharing state across several threads.
Remember, a dictionary has one entry per key. That's the definition of what a Dictionary is, and a ConcurrentDictionary doesn't change that.
A fuller and more complete answer to your requirement is below.
The whole solution is short sighted as you have no connection with the session infrastructure to know when a user's session has timed out and effectively caused them to be logged out. Additionally there is no coordination with other instances of your app if you ever think about deploying to a cloud platform that spins up new instances.
In other words, you are putting yourself in a situation that makes it very difficult to scale your app without breaking this feature.
Probably one of the most robust ways of handling the single session requirement is to use your database:
Have a field that keeps track of the last session ID your user had when logging in.
Add a session listener to clear the field when the session times out
If the session ID is not the same as what's in the field, you know you have a new login attempt.
If you need complete control over the session ID, then supply your own session id manager (may be necessary to include an encoded server ID in it).
You'll find that the requirement is much more involved than it sounds on the surface. You can't think like a desktop application in the web space--which is precisely where this requirement even comes from.
I am using WebMatrix (C#) to design Intranet web applications for the organization I work for.
I have made one database driven site, and am currently working on another, and for some time, I have been having some trouble with the Session variables randomly becoming null and throwing errors. So much so, that one simple Session variable was switched with the use of the server cache memory instead (which I originally thought would be more volatile, but that remains to be seen, so far...)
One question is: Is there any practical use of the Session variable, at all? If it truly is as volatile as it has seemed to be, they appear to be good for just about nothing.\
I know they are technically cookies, so I know that their data shouldn't be relied upon, but therein lies the problem. I need to send data to other pages that I "can" rely upon. This leaves out both Session variables and cookies.
I generally stay away from query strings or url data, for their blatant "plain-text" display of any sensitive information (like Social Security Numbers), with which, even SSL won't help.
The server cache memory is also volatile and is not to be relied upon.
AppState variables aren't user specific.
That leaves hidden input fields... The problem here is that, sometimes after "Post" I do Response.Redirect, and such, so C# doesn't always render a page after post (it seems).
Maybe this is just a lack of knowledge on my part, but I kind of seem cornered no matter which way I go.
Do I really have to save all page information into a separate database with every page and retrieve it with a sql query on the other page just to get reliable and not "blatantly" displayed information from one page to another with Web Pages? Still even this method would be a problem using several different users, no?
ASP.NET has different Session State modes:
InProc, this is in-memory. Session State lives as long as the IIS Application Pool isn't recycled or the entire IIS is restarted.
SqlServer. This is Session State is stored in a SQL Server storage. This is great because sessions survives after an IIS Application Pool or entire IIS restart, but it's a bottleneck as it means that every access to the session requires a deserialization and/or serialization of the Session State objects and, after all, database connections and so on.
StateServer. Similar to SqlServer, but using a Session State Server provided by Microsoft. This mode isn't used at all, but it's an option... (I've no experience with it).
Custom. You can implement some interfaces/abstract classes and define your own Session State storage.
In the other hand, Session State is server-side, it has nothing to do with cookies. It's a way of simulating state in a stateless world ruled by HTTP. Since ASP.NET writes an HTTP cookie in the browser, it can link a browser session with an unique server session too.
About if Session State is useful or not.... In my case, I've decided to avoid "states" at all. I prefer to stay stateless as much as possible. I write down some HTTP cookies in the browser to identity settings, preferences or users, and I do things per-request.
I prefer that because a good caching mechanism can insanely optimize the requests' performance as in most of the cases you wouldn't be accessing data directly in the store but in some cache, which means a lot of speed!
By the way, Session State shouldn't be used to store large object but basic values. Session State isn't a cache. For example, Session State could be a good place to store something like current logged-in user or his/her role. Or their profile identifier. Who knows.
Any other data should be queried in a per-request basis.
And again: cache should be your friend in terms of optimizing your environment and don't accessing the database or whatever in each request, compromising the system performance.
So, im working in a huge .NET MVC 3 system. As many users could be logged in at same time. I was just writting a way of "hey there's still someone logged with this key" with HttpContext. But, is this the best practice ? is it better to Query DB ?
what i wrote:
MvcApplication.SessionsLock();
if (!force && MvcApplication.Sessions.Values.Any(p => p.ID.Equals(acesso.id_usuario.ToString(CultureInfo.InvariantCulture)) && p.Valid))
throw new BusinessException("There's another user logged with this key. Continue ?");
MvcApplication.SessionsUnlock();
our I can query my DB.. maybe cookies ? any ideas would be appreciated
Storage
The database provides a central, durable location for this information. You might use a custom data structure, or ASP.Net SQL session might meet your requirements (more below on this).
There is not a deterministic way of always knowing exactly when a user's session ended. For example, you can listen to the Session End event, but it will only fire for in-process sessions and is not guaranteed to fire at all (e.g. the OS could crash).
Regardless, if you are building a "huge system" as you state, you shouldn't design against using in-proc session as it won't scale upwards. Start thinking about SQL-based session state which is more scalable (and may give you enough information to determine roughly how many users are active).
Session Pro/Con
I want to know if session is a good practice. That piece of code
works. But i have been reading a lot of articles deprecating usage of
sessions on ASP.NET MVC Application.
As far as Session being a good or bad thing--as always--it depends on how it is used. Properly designed MVC apps can present fairly complex views without needing to preserve state. Part of this is due to strong support for AJAX (no need to reload the page) and elegant model binding (which can take a complex Request.Form and turn it into a complete model).
Conversely, there is nothing inherently wrong with putting small snippets of repeatedly-used information into session state, using it to avoid sending sensitive data to the client, using it to make a smoother user flow, etc.
Do beware of session fixation attacks in high-security scenarios. Session may not be appropriate and/or may need to be manually secured further.
One thing to be aware of is that ASP.Net places a lock on session. This can lead to very real performance issues when multiple requests are made at once. Normally, this isn't an issue, but consider a page with a dozen AJAX widgets which all requested data from a controller or endpoint that used session. These will contend with each other (firsthand experience).
A non-locking in-process ASP.NET session state store
https://stackoverflow.com/a/2327051/453277
MVC provides an easy way to mark a controller as needing only readonly access to Session, which eliminates the issue. However, any read/write activity to Session will still be serialized, so plan accordingly.
Business Considerations
From a business perspective it's not always important to know that the session has expired so much as work has ceased (do you care that they stopped using the site, or that their session timed out?) This can be reliably addressed by checking last modified timestamps on entities and warning the users. Warn, don't lock. In my opinion, you shouldn rarely/never lock records based on login/logout in a web application (too easy to get stuck in a locked status).
Quick question: Is there a "per-user" data storage object (similar to Session) that I can store data in the global scope (similar to HttpRuntime.Cache)? Almost as if Session and HttpRuntime.Cache had a baby.
Full Background: I have a ASP.NET website that was originally written for a single thread. Now I changed it so that certain actions will spawn a background thread and the browser polls a service to get status updates.
The problem I am having with this is that certain pieces of data are stored into the HttpContext.Session[] object (membership authentication token, for example). These pieces of data need to be unique to each user and accessible to the background thread. Session is not available to the background thread.
I am aware of HttpRuntime.Cache but that would require micromanagement to segment out the users and to expire it at the same time the session is expired. Session, on the other hand, automatically expires this things at the right times that I want it too and is already used by things like the SqlMembershipProvider.
My question is, is there something that behaves similar to the Session but exists in the global scope?
I don't think there is anything like you need out of the box. I would do the following though:
User the application cache
Make the key the user ID or unique identifier
Store a Dictionary or some object list in the value for the user. Use this to store all the data you require.
Consider all prepending something on the user ID if you think there could be a conflict with the user unique identifier (eg domain etc)
Make sure to set an expiry on the cached data similar to the session (eg sliding)
Try passing the HttpContext.Current object to the method on your background thread. You should be able to access the session from the background thread through currentContext.Session assuming currentContext is the HttpContext parameter that was passed in.
See this blog post on how to safely access the HttpContext object from multiple threads.
No.
Since when application pool restarts all backgound activity die I suggest to think about moving user's state to your own database or external storage. Unfortunately you'll lose automatic session management benifits (sliding expiration), but if you need backgound activity it will work better - i.e. you'll be able to move your activity out of IIS process to separate process/machine if needed later.