I'm currently trying to set up a session management interface for users to essentially log out their sessions that may be active on other devices. However, I'm still somewhat new to Asp.Net Core 2.1 and am having trouble finding good documentation on the subject.
I thought about using the distributed SQL server cache system. However, after further inspection, I found that the keys for the distributed cache are not equal, as they shouldn't be, with the session id.
I also tried writing some middleware that stores the session id in a separate table with a many-to-one relationship with the user table. This table would have a sliding expiration dates and a tokens. If the session had a token, the session would be persisted.. My thought was to assign a token to the client using a cookie. That way if their session expired, it would lookup the session with the cookie token and, if one existed, log the corresponding user in. Then it would copy over the token and delete the old session. Kind of like a 'remember me' system. If the token is null and the session time was expired, it would be disposed of. If no session was found, or the user field is null, it would log the user out. If duplicate tokens were found, it would log all of the sessions with the corresponding token out. However, I'd rather use some kind of built in feature, if it exists, to minimize the risk in opening up unwanted security vulnerabilities.
I've also found examples where you can log another user out... But, because Asp.Net Identity is cookie-based, it allows the user to continue to use the site until their cookie expires... This would be undesirable in this scenario.
I know that Asp.Net had the IHttpSessionState, but I've been unable to find a similar interface in Core. Unfortunately, most solutions I've found either point to implementing a custom-made system, or they just show how to log the current session out.
Basically, is there already some kind of mechanism in Asp.Net Core that already implements something like this? If not, is there any specific interfaces that I should be researching and trying to implement? If not, should I resort to writing my own system? If so, are there any holes in my logic above?
Here's an example of what I'm talking about, pulled from Facebook's account management. I know that it's a much larger scope website, but I wouldn't think that such a feature would be extremely hard to integrate? Might be wrong though...
(Redacted some personal info)
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I wanted to try this code/solution to my ASP.net (VScode 1.69.1) but I am not sure where is the "Global.asax". Anyone know how I can apply the code below to asp.net core?
https://teknohippy.net/2008/08/21/stopping-aspnet-concurrent-logins/
I would not advise you to use that code, it wasn't even good advice back in 2015, but we can explore the concept and it's flaws which might help you come to a better overall solution.
This post will provide some context to the issue: Single Instance Login Implementation but is not a direct duplicate. The original source article does actually go into better detail about the general issues with this approach: http://www.nullskull.com/articles/20030418.asp
Using an In-Memory cache is not a viable option for production as multiple instances of the application would not share the same cache, especially if the application is hosted across multiple servers or serverless infrastructure that is configured to scale out beyond a single instance.
If all you want to do is block new logins, if the user is already logged in, then a server-based or cache concept itself is the right solution, conceptually to enforce a single instance across different browser sessions and across multiple servers will require that there is a server-side cache or store that holds the source of truth for all active connections. This could be in the form of a database or a distributed cache like REDIS.
But this is not a practical model for how users actually use their browsers and devices. Instead of blocking new logins, it is more practical from a user point of view to expire or force close the existing logins. The problem with only blocking new logins is that if the user doesn't have access to the original browser session that holds the login, then there is no way to log out the previous session, you would have to wait for it to timeout. The challenge with being able to expire a login session is that your clients and the server code must be designed to round-trip to the session store to validate the session token. Most default JWT or even cookie implementations do not do this, they will rely on the expiry or validity information in the token itself, and bypass consulting the store.
Instead of the article you have found, please try these resources:
ASP.NET Core security topics
Can I force a logout or expiration of a JWT token?
JSON Web Tokens (JWT) are Dangerous for User Sessions—Here’s a Solution
I have an ASPNET CORE 2.0 website that is published to a web server farm. I am using Identity Role/User claims for authorization. I have a large number of claims associated with the logged in user, which is bloating the size of the application cookie. I see a few techniques for dealing with this situation, but am unsure what path to take.
Using a custom ClaimsTransformer: create a custom DB store outside of the Identity Role/User claims tables and load the claims on TransformAsync. I'm not sure if there is a better solution that doesn't involve a DB call every round trip to the server.
Specify a Distributed Cache Session Store when specifying the ApplicationCookie. I'm not sure if this will resolve the bloated cookie issue.
Using a sticky Session to store user claims. I don't think that this works with claims authorization ([Authorize])
How do I use Claims Based Identity across multiple web servers when the user has a large number of claims?
Cookie size is basically the strongest argument against "everything as a claim," and it's unfortunate because that model works pretty well, otherwise (I've been in your shoes). Just as you suspect, the best approach is to restrict your claims to the bare minimum and use the identity (subject id) to retrieve more detailed app-specific information from a database as needed.
If database response-time is a concern, you're basically back to stateful session data. Microsoft would likely guide you towards Redis in-memory caching. Not sure if that's an option on Amazon, I use Azure.
I tried the ClaimsTransformer routine, but it became a larger hassle constantly addressing "is this really a claim or just something we're treating as a claim?" versus just separating persistence/retrieval of real IDP claims versus internal application-level user data.
The question is really that how can an auth server that serves JWT be used by multiple websites of same company or domain (with the websites as sub-domains), for example? Not something for the public.
Already, I'm thinking of asymmetric JWT. Also, I don't want to implement OAuth 2.0 in order to avoid complexity and because the auth server would only serve web apps that are sub-domains of a same root domain.
seeking for less complex solutions based on the current description in this post
If you want a reliable and secure way to share resources between different sites, you might want to look at IdentityServer.
In a nutshell, you basically redirect anonymous user to identity server to login. After successful login, it will return a token to the user. Then the user uses that token to access resources from different sites.
Look at the basic workflow and screenshots at my GitHub sample project.
Ok so here is the deal.
Can multiple web apps access the same database (identity db or otherwise)? Of course! Now if you are using Entity Framework (and I assume you are though it wasn't stated) then this can get tricky as far as migrations etc. Personally I use Dapper so I never have to worry about that :-)
Yes the apps can each access the db but that is WAY different from from SingleSignOn which is really what you are talking about. You want a user to log in to one site and that identity to persist to other completely different sites. That's not nearly as simple as simply accessing a db. IdentityServer is virtually the standard for this kind of thing for many reasons.
No, the ajax approach will not work because when the user logs in at site1 the cookies are for site1. If he goes to site2 the browser does not have any cookies associated with site2 even though you sent credentials via ajax. The user was on site1 when this all happened so all cookies are site1 cookies, totally separate from site2 cookies. Even if you can find a way to make this work it would pose a serious security risk.
You could conceivably do something like this using hidden IFrames instead of ajax because you can set the iframe's site's cookies while you are there. But I don't recommend you do this as there are security risks involved.
You need to separate the idea of "Authentication" from the ideas of "Authorization" and even "User Management".
Authentication---- Am I who I say I am? (check my usename and password and maybe even additional form like text message etc)
Authorization---- Ok you know who I am, but what can I do on your site? This can vary from site to site. Maybe I am an admin on one of your sites but just a regular user on another. My individual site cookies will includes roles etc and they are different for each site.
User Management---- Can I change my name/email/etc?
The best way to handle this is to use a separate server app running IdentityServer. This handles the authentication and builds out the cookies for all of your sites at once. Ideally you should also use this for any user management but that can be a pain and isn't as vital. Here are a few sample apps for IdentityServer4.
Response to your Update 2----
Not exactly... Here is the basic flow: User goes to site1 and clicks "login". This fires a "challenge" which redirects them to website-auth. On website-auth the use submits their credentials (username/pw) via form post. This logs them in to the website-auth but then also redirects the user back to the original calling app (site1 in this case) with everything they need. Let's say the user now goes to site2, they are already logged in!!! Using IdentityServer4, the user will become logged in to all of the sites sorta automatically. You won't have to do extra stuff they way you described, just plug in the necessary stuff and let IdentityServer4 handle the rest.
Look, I understand that IdentityServer4 probably looks a bit intimidating, it did to me until I began working with it. Truth is, all of the hard stuff is handled for you. There is still a decent amount of configuration involved in getting it set up but it really is the best solution for what you are looking for.
Check out these quickstarts: https://github.com/IdentityServer/IdentityServer4.Samples/tree/release/Quickstarts
Response to Update3------
I understand the concern of relying on a third party and how that can seem like a questionable practice, especially when it comes to security. My response is this:
These guys are the EXPERTS in the field. So much so that IdentityServer has become the defacto security solution even in the basic templates Macrosoft provides.
Any home grown solution you will come up with will have more security holes that what IdentityServer has. This is not a slight on you at all. These guys know what they are doing. They have been doing it for years.
Why reinvent the wheel? You will spend 10x (at least) as many man-hours trying to come up with an alternative that, in the end, will still not be as good.
If what you were doing was a single website cookie based authentication then using identity really isn't necessary. Identity can do that, but there are other simple alternatives. But when it comes to multiple sites and SSO, and I really can't emphasize this enough, IdentityServer is the way to go.
The answer is a microservices auth serve that generates RSA/Asymmetric JWTs with a private key and the other servers each have the same counterpart public key to validate the JWT and retrieve the user claims.
But that solution doesn't not cater to the situation where each of those other servers need a different set of claims about about a user.
It is also not a single sign-on approach. So, I'll be back.
But OAuth 2.0 seems to be the answer, but it is too complex for my liking.
i am using a session cookie (not a permanent one) to save the user id to know if the user is logged in.
basically, user logs in, we check the credentials, then set a session cookie userID = 37 (for this particular user, another user would have 73 or 69, etc...)
Session.Add("UserID", 37);
my question is, is it possible for the logged in user to somehow change this session cookie from 37 to 73 and thus fool the server into thinking he is actually user 73?
if YES, then what am i doing wrong, how to handle this case? it seems insane to put in session user id and password hash and check them EVERY TIME??
we are using this userid value also in queries later to restrict them.
i am sorry if this is not an EXACT code question, but it is very much relevant to my code.
The session cookie contains only the session id. It is used to identify the user. It contains nothing more. The actual information for this session is stored on the server. So this is secure. The user can never change the value that has been stored on the server. The user cannot change his id if you stored this inside the session.
This being said, when dealing with user ids you could consider using forms authentication to track authenticated users instead of reinventing wheels with the Session.
ASP.NET session state provides an important security advantage over client state management techniques in that the actual state is stored on the server side and not exposed on the client and other network entities along the HTTP request path. However, there are several important aspects of session state operation that need to be considered in order to maintain application security. Security best practices fall into three major categories: preventing session ID spoofing and injection, securing the state storage in the back-end, and ensuring session state deployment security in dedicated or shared environments.
Read : Securing Session State
That isn't the cookie, and is perfectly safe as it cannot be changed by the user. The only thing stored on the server side in a cookie is the session ID.
As the other answers have noted, the actual value (37 in the example) is stored on the server, not the client, but that doesn't mean that you're immune to potential attacks. This mechanism is still vulnerable to cross site scripting attacks. Basically, what is stored on the client's cookie is some big long identifier. If someone other than the actual user gets ahold of that identifier they can put that in a cookie of their own and essentially pretend to be that user. You can research cross site scripting more on your own (I'm not an expert on the subject) to see some of the common ways that a malicious user will attempt to look at other users' cookies and to try to set it as their own, along with ways of defending against such attacks (some of which I'm sure will be done for you by browsers and ASP).
I'm re-writing a website from the ground up for azure. Each user has ownership of a number of objects, and has a number of permissions. Together, these determine what they are authorized to do. The question is, how should this information be stored. I want to do the authentication myself, using custom logic.
For performance reasons, I'd like to cache these authorization lists for each user once they're logged in. Can someone give me a sample for how to store & access this session information securely and efficiently.
Edit
I looked into the App Fabric Access Control, but that seemed overkill as I was going to have to create a separate site for authentication, which doesn't seem to make sense. Would the claims based authentication make sense separately though? How would you do that if it does?
Would it make more sense to just keep the username in a cookie in the traditional way and then re-query table storage with each request to get the permissions etc.? How would storing the username work in Azure?
Cost is a big factor here as it's a very small site (by azure standards) but I want high performance for a small number of users.
If you want to run with a reasonable amount of availability you need to run your site with two instances. If you're running with two instances you need to use a session provider that's no the default InProc one. Your choices are:
AppFabric Caching (which you don't want to use because it's too expensive, fair enough)
Azure Storage Session Provider. Don't use this. It's an interesting experiment, but it's only sample code, it's slow and doesn't cope well in production.
SQL Server session provider.
If the permissions for a user weren't going to change while they were logged in, you could just store their permissions in session. This will probably be fast enough. However this information will need to be read from SQL for each request that uses session and it is overhead.
If you wanted to make things faster you could just store the user ID in session and load the permissions into a static dictionary (keyed on user ID) when needed. These items will need to be expired after a certain amount of time or lack of use.
Well, you could use the Azure App Fabric cache to store the session info. ASP.Net can be configured to use it as the backing store for its session state as like a normal custom session state provider.
This article from MSDN shows you how to configure it:
http://msdn.microsoft.com/en-us/library/windowsazure/gg278339.aspx
From your code you just use the normal ASP.Net way to get/set the state.
Be aware though - it could be expensive ($45/month for 128MB of cache).