What is a good strategy to manage sessions for beta webapplication?

Question

I am trying to create a webapplication using Spring. The webapplication is a beta/demo site, which is invitation only. So, I need to generate a link to the webapplication url, appending a unique id, which would be valid for 24 hours. User can use that link for 24 hours and make use of the (I kind of also have plans of restricting the user by ip)

To achieve such token generation and expiry, should I just rely on the container with session time out to do it? or does it make sense to create spring backed service layer with token creation and expiry services?

EDIT

Now that I have a bounty on this to draw more attention, I thought I will rephrase the question so that it makes more sense - what would be a good strategy to force users out of a web application after a certain period of time?

Answer 1

Here I can think of two use cases that I have seen.

1.) This kind of management is used in applications like online tests or email verifications, where user is provided a link with some token. This link and the token is valid for some fixed period of time and can be used only once. (Ex. online tests or password reset-emails)

2.) Another use case is to provide link with a token which are also valid for a fixed period of time, but in this case the link and the token can be used any number of time within the time period allowed (Ex. Online registration forms for test or some university enrollments).

So, definitely managing this using a session only will not be a good choice as the browsers can be cleared. So you need to maintain the pair of the link and the token at the server (May be in a DB) with some other information like last accessed time, creation date and time, Valid upto .

To be more flexible validity time for link and the token can be set differently (eg. link can be used for a set of users, but the tokens are unique to a user).

So you can use this info on every user visit to check whether the link or token is still valid and what are their last accessed time. If it turn out to be expired then you can show the relevant error message.

Answer 2

Relying on session timeout would not be sufficient solution .

I am not acquaint with Spring . I would put my generic solution as below for any web application having requirement as yours :

1. Invitation is assumed to include a link to the Web Application .

2. The link is assumed to include the unique id .

3. The Beta/Demo user table is assumed to have a beta-expiry ( datetime ) column to hold the expiry date and time .

4. When your web application is accessed using the link in the invitation , update the beta-expiry column for that unique_id considering 24 hrs from then .

5. When a Beta/Demo user attempts to sign in , check the beta-expiry column for that particular user and allow access if the expiry is not reached . Display appropriate message in case of expiry .

6. Whenever a signed in Beta/Demo user performs subsequent accesses to your web application , check the beta-expiry column for that particular user and allow access if the expiry is not reached . Display appropriate message in case of expiry .

7. If seems useful , display a countdown timer showing the left over time somewhere in the header area .

8. In case of extension of Beta usage for all or a portion of users , you could update the beta_expiry column appropriately .

9. Additionally you could also have an invitation-expiry column to hold invitation expiry considering a particular duration for eg. a 48 hrs from when the invitation was sent .

We use a little bit similar solution to sign out ( signed in ) users from our SaaS application after a particular duration of no access .

Answer 3

Tokens

For this marketing purposes we generate tokens upfront, store them in a database alongside all information like restrictions to certain user account, ip ranges (for certain mobile carriers), the date and time ranges of use and so on.

In case of one time codes we just mark it as being used in the database.

To generate those codes we use Random Numbers or encode some information and use (SHA-1 or better). Then we use bigInteger.toString(36) or a different scheme and group the first 16 letters to let it look like a license key.

If we express information with it like useraccount/name or carrier (mobile) or whatever we can even validate the token without a database.

Forcing User Out

Just check for the validity of the token the first time the user starts a session or logs in. Throughout the session you just check if the token has expired (store a value in the session if you have one, append it (encrypted) in the url or whatever or check against a database.

So on every request you just check if the user has permission to access your site otherwise you block the user with an error / info page.

You can also add a java script to each page. The script can determine whether the users permission to use your site has expired by:

• Encrypt the relative time that the token is valid in a hidden div and calculate the absolute time using the users local time. Then compare the absolute expire time with the user time every now and than (lets say every 3 seconds) and you can yourself all those polling and pushing (comet, ajax, websockets) behaviour.

Once the java script program notice the token has become expired remove the content sections and replace it (or mark a hidden div as visible) with the info / error page content. This way every time the user revisits pages still stored in the browser history are destroyed also. (if this is a necessity for you).

Summary

• Use random tokens and a database or encrypt information (like the day the token can be used) and SHA-1.
• Check the tokens validity every time the user requests a page (store the timeframe in a session / url to save roundtrips to the database)
• Provide a java script that destroys local pages in the history on revisit.

Answer 4

One strategy is to keep track of expiry date-time of all the users by storing the relevant data in DB and using a cache library (to reduce DB hits while checking for the expiry date). Here is a small example:

Create a DB table with columns to map user id to expiry date: id, unique_user_id, expiry_date_time. You need to create the unique user id in your code and save it in DB before sending the URL to the user with this id. You can keep null as the initial value for expiry_date_time. Create a class to represent this mapping in Java:

class UserIdWithExpiryDate{
        private String userId;
        private Date expiryDateTime;
        ...
}

Define a Service with a cacheable method that will return an instance of this for a given userId :

public interface CacheableService {
    @Cacheable("expiryDates")
    public UserIdWithExpiryDate getUserIdWithExpiryDate(String id);

    public void updateUserIdWithExpiryDate(String userId);
}

import org.joda.time.DateTime;
@Service
public class CacheableServiceImpl implements CacheableService {

    @Autowired
    private YourDao dao;

    @Override
    public UserIdWithExpiryDate getUserIdWithExpiryDate(String id) {
        return dao.getUserIdWithExpiryDate(id);
    }

    public void updateUserIdWithExpiryDate(String userId){
        Date expiryDate = new Date(new DateTime().plusHours(24).getMillis());
        dao.update(userId, expiryDate);
    }
}

The result of getUserIdWithExpiryDate method is stored into the cache so on subsequent invocations (with the same argument), the value in the cache is returned without having to actually execute the method.

Next step is to check the user's expiry date while accessing the site. This can be done using OncePerRequestFilter:

@Component("timeoutFilter")
public class TimeoutFilter extends OncePerRequestFilter {

    @Autowired
    CacheableService cacheableService;
    // Here you need to decide whether to proceed with the request or not
    @Override
    protected void doFilterInternal(HttpServletRequest request,
            HttpServletResponse response, FilterChain filterChain)
            throws ServletException, IOException {
        filterChain.doFilter(request, response);
    }

}

Steps that can be taken inside the doFilterInternal method to check the validity of the user:

1. Get the user Id from request
2. Execute: cacheableService.getUserIdWithExpiryDate(userId)
3. If step 2 returns null, there is no user present with this id. You should not proceed with the request.
4. If step 2 returns an instance of UserIdWithExpiryDate, check the value of "expiryDateTime"
5. If the value of "expiryDateTime" is null,it means user is accessing the site for the first time.Update "userExpiryDate":cacheableService.updateUserIdWithExpiryDate(userId) and proceed with the request.
6. If "expiryDateTime" is not null, compare this with current date_time. If expiryDateTime.isAfter(currentDateTime), proceed with the request.

For caching, you can use Spring Cache Abstraction with EHCACHE.

Answer 5

I think that you should rely more in the back-end rather than a session on a cookie, imagine the case that you set the cookie for 24 hours expiration but the client deletes the cookies from the browser, (depending on your logic) your link will generate a new session or the request will be blocked.

IMHO you can store a session cookie on the client but you need to have a second source of comparison in the server, maybe a database, no-sql document, a collection in cache, something that you can compare and check the latest access to the client.

just to put all together imagine the following use case:

• the user get the invitation link and click on it
• the system check if the first time they log into the system, and save that date as a "start date" and another one as "last access"
• the system sets an authentication cookie with 24 hours expiration
• the system track every post back/ ajax call to the server and update "last access" date
• if user deletes the cookie the system check the "last access" and make a comparison with the current server date
• if valid the system creates a new auth cookie with the remaining hours
• if not valid the system sends a message to the user.
• for the user the cookie will expire according to the time left (calculation between start date and last access)

I hope this helps. regards

Answer 6

You can store the id with expiration time and when a request comes in with that id check if it's still valid and if you are trying to accomplish something like id is valid say 5 hrs after first request then store time when the first request is made and for each subsequent request check if it's still valid

Answer 7

What about "deleting the user's account" (depends on how you are building your logging system) after 24 hours. Coupling this with checking user's account every time (s)he loads the page, will force him/her out at the first refreshing after the 24 hours threshold passses.