I know a few sites (such as my bank and my school) that kill a session after their has been idle for a set amount of time. It is my understanding that session activity is determined by users following links or at the very least from some kind of active interaction, like updating a form via ajax. Basically the server gets a request to do something during the session and goes ahead and extends the session time another 15 minutes.
But on some occasions I have lost major amounts of time and info while filling out a text box or reading some long set of instructions along the way.
So why not have an ajax script that listens for keyboard activity and mouse movement and lets the server know that the user is still there and active, even if they aren't clicking a submit button or following a link?
I was wondering if anyone knew of respectable sites that already do this, or if I was overlooking some major security hazard with this idea.
The only thing I can imagine would be risky are the random acts of cats, vibrating electronics nearby, or a hyper child.
But in all of the above, the user is most likely at home and -- unless they are trying to get exploited -- have probably minimized the window and thus these things are very unlikely to trigger as an event.
Does anybody see any other major risks?
Typical AJAX sites are making posts back to the server anyway. These events are renewing the users session already.
If you put these events on keyboard or mouse clicks, how many times are you going to be posting to the server? If I am typing in a form field like I am now, that means you could potentially have a ping to the server for each letter I type; not a very efficient solution. On the other end, what if your user is just sitting their reading or using an external text editor to type their text into and will copy it into your form later.
I think the more typical solution to provide a friendly UI so that long posts do not get dropped because of a session expiration is to use an auto-save feature. Google Docs does this. Every few seconds/minutes, they post the contents of the editor back to the server without the user actually clicking save/submit. The other option is to inform the user that their session is about to expire (could be done with a javascript timeout). Provide a link to ping the server to renew the session.
Your solution lends itself to the same problem: you are relying on user behavior. In the first case, navigating between pages and in the second, mouse clicks.
I used to work for a company that did a lot of online contests where users would have to enter essay content as well as shorter blocks of data; we used to modify the session time out "session.setMaxInactiveInterval()" for the user's session when they hit the "long-winded" page so that they would have more time to edit, and then we would set it back to normal after the submit.
Later at that company and a couple others I worked at I proposed a solution similar to what you are describing, but for various reasons it was never accepted. It was never considered a bad idea, just not one we chose. Basically it was going to be an ajax call on a timer so that just before the session timed out, it would fire off a light-weight ajax "ping" and keep the session alive as long as that page was open. I have never had the chance to implement it in the "real world" so perhaps there are negatives that I have not thought of.
Good luck.
Related
I'm developing a website that is suppoused to control some devices that rotate when pushing one button. However, I only want one user at a time to be able to push the button.
That is, when a user enters the page, check if it is the "first" or only user that is there. In case he is, he can use the button freely. In case he isn't, the button appears as disabled.
What would be the best way to implement this? I'm using a classic design of html+js+php.
Thank you.
This is a design question, and still, you should have already tried something and post that something before asking here.
You should use a lock system:
create an endpoint with php, to call with Ajax that checks over a variable globally shared (better if on db) that acts like a semaphore, the first who arrive make it red and 'acquire the lock'.
If the lock is acquired, the client can do the action,
If the lock is not acquired, someone else took it already.
Do not forget to release the lock after the action.
You can use the same call to acquire the lock, do the action and release the lock. If the lock is not acquired the call return an error message and the user will know which is the issue.
P.S.
If you was thinking about a real time system, you may consider using websockets or just the system above with different calls for acquire the lock and do the action (and poll for the lock status).
To track a user on a website is not that difficult, but check if and when he/she leaves is the challenge.
If this is not time crucial you can do this with timeouts.
First, you need to be able to track the current user on your site (maybe with sqlite, textfile, mysql/mariadb) (maybe identified by IP) wich is updated a user loads the page.
After a timeout the tracking storage can be updated and the next or new one can hold the button.
If you need this realtime, you need a bit more to do. In this case I would use Websockets or NodeJS to keep connections to your page wich in fact you can use to keep track on active users and wich one should be able to keep the button.
Just keep it like a realtime online chat without texting. There you need to keep track of online users as well.
(Websockets or NodeJS are here only a example, there are alot technique to archive realtime "collaboration".)
I am using Casperjs to Login in my Amazon Account and retrieve some data.
But once in a while I get Captchas on the login. So casperjs display to me the captcha and I manually return the solution so it can submit the form.
The problem is that CasperJS gets immediately another captcha, this time it's more difficult. I resolve this too, but another captcha appears... and so on indefinitely...
I don't do anything special, just some casperjs fill and click.
Casperjs loads in the page an external js file with the captcha solution, and then submit.
I am sure that the right captcha is submited.
How can Amazon be so sure to trap me in an infinite loop?
Consider how it looks from their point of view. They can tell a robot is accessing your account based on mouse and keyboard interactions. A human will scan the page and move their mouse randomly while searching for the login buttons. Your script jumps directly to clicking the selector.
When a captcha appears, you fill it in. This does not prove you are a human. This simply proves that your robot can alert you to a captcha for a human to fill in. The rest of the interactions are all done by a robot, and Amazon is fully aware of this. You can answer as many captchas as you like, but the interactions to get this far are still going to be flagged as a robot.
You may want to go down a different route, like having a cookie to start a CasperJS session with your account already logged in. Alternatively, does Amazon provide any sort of API to pull out the value you're interested in?
They're blocking your robot out of geniune love and concern, if that makes you feel any better!
Unfortunately this is not an exact science, so probably there is no such thing as a general, durable solution. Amazon.com uses different techniques to check if you are a robot, including browser fingerprinting, cookie challenges and user behavior profiling (mouse movements and so on).
I would try first to randomize some part of the user agent, only to see if that works. And I would also try a full headless browser like Chromium, using Selenium to allow the script to talk with it.
Can I ask how frequently are you trying to crawl your account? I think it shouldn't be a big deal if you are doing that one a day or so.
I have an html5/javascript application in which multiple users can be viewing the same set of data of any given time. For the sake of a real world example, lets say its a calendar type page.
So user1 is looking has the browser open and looking at the calendar page and user2 is also on the calendar page. User2 makes a change to the calendar and i'd like (as quickly as possible) for those changes the be recognized and refreshed on user1's screen. What is the best way to do this?
I'm thinking about have a mysql table for active users that stores the page they are currently on and a timestamp for its last update, then use ajax calls to ping the server every few seconds and check for an updated timestamp, if its newer than what they have client side, the new data gets sent and the page "reloaded." I am putting reloaded in quotes because the actual browser window will not be refreshed, but a function will be called via javascript that will reload the page. Sort of the way stack overflow performs its update checks, but instead of telling the user the page has changed and providing a button for reload, it should happen automatically. If user1 is working away on the calendar, it seems it might be quite annoying for user2's screen to constantly be refreshing...
Is this a horrible idea? Is pinging the server with an ajax request every few seconds going to cause major slow downs? Is there a better way to do this? I would like the views on either users side to be real time because its important that user1 not be able to update an element on the calendar page that user2 has already changed.
Update: based on some web sockets research it doesnt seem like a proper solution. First its not compatible with older browsers and i support ie8+ and second i dont need real time updstes for all users on the site. The site is an account based applicatiin and an account can have multiple users. The data needs to sync between those users only. Any other recommendations would be great.
You need realtime app for this. You should have a look at socketio. Everytime a user log in, you make him listen for changes on the server. Then when something changed on the server, every users listening are notified.
you can find examples on the official website : http://socket.io/
I am trying to prevent fraud in a webproject I am building.
The project is a game which includes multiple websites.
Each website does a ajax check for with each pageview to a webpage on my server for a status update of the game.
The response page, lets say www.domain.com/response.cfm (it is coldfusion) normally returns nothing, but at a certain point of time within the games timeframe, it will display a JSON string with information.
This information is then used by the script that is included on the websites.
So website A has been viewed 100 times (all of its pages), which will generate 100 ajax calls.
The problem I have is that a robot could check the ajax destination too, and much faster. Now I can detect a robot, or could make it difficult for him by using a session or checking for cookies, BUT...
the biggest issue is that I found out you can do a lot in the Firebug script console, or the Safari console. Probably Chrome too.
With this console, they can even evade the crossdomain restriction. I created a simple script that does a couple of calls to the Ajax page and when I go to the same domain first, and then use the console...there is no crossdomain limitation. And you execute all kind of javascript, so in essence someone like me could commit fraud in the game by using the javascript console which masks him as regular browser user.
My question now is: Does anyone know how to prevent this? I tried to disable the usage of the console but I don't think I can. It may be possible to detect if the console is active and then disable MY scripts so the game doesn't work. But I think they can load the script source in the console manually and then the game does work.
Looks like console is a beautiful thing, but a nightmare for me now to prevent people cheating in the game I am creating.
Hope anyone has suggestions.
ps: of course I am trying to implement som server side checks to detect cheating, but most of the time it is not realtime.
UPDATE 19/3/2012
The fraud that I am trying to prevent is cheating in the game by polling the page that generates logic for the next step of the game. This is a serverscript page which generates json code which will trigger a change on the website the game is played on. For your information, websites the are involved have a script in there header, like google analytics, so they will communicate with my server every pageview.
Polling that serverpage can reveal information which will gain the cheaters knowledge or progress.
So i have to prevent people from getting knowledge ahead of other earnest players by monitoring the serverpage which will reveal information at a certain time. I don't want them auto polling it and when info is revealed, the send themselves a notifcation and check the website.
So what I will do is make sure that if people have to many pageviews per second, they are blocked. Plus you need a cookie to be able to join in and you only get a cookie by logging in. Hopefully this will give me enough tools to make it as robust as possible.
Thanks for all your knowledge, people.
It would be very, very difficult to disable web consoles across the majority of browsers, and anyone who managed to do this would probably be exploiting a browser bug. But read on...
First rule of web programming: You can never trust anything you receive from the web client. Anything that gets sent to your data might have been forged or altered intentionally or unintentionally, and even if you did manage to block a web console, what's to stop me from opening it in a different browser which specifically disallows websites with the console? So that's out. As #DCoder mentions in the comments, there are other methods as well, including browser extensions, which would allow user-defined JavaScript to be executed.
So any checking you do has to be server side. I know you're trying to do some checking already, and it's hard to give advice without having more specifics. That said, one way to do this, as far as I can see right now, is to issue each client an ID and store that in a database somewhere. They can't be sequential IDs, and make sure that they're not trivially forgeable even if someone has a bunch of different IDs (for example, you might want to salt the username, and then hash it). Each time a request is made to the server, only issue a response if the last request was >500 ms ago, and update the database accordingly. Expire the ID after logoff or some time.
The first thing you should think about is securing your server, not the client. It's impossible to hide client code from the client. While it might arguably help prevent a few people who want to cheat from cheating, it's not your primary objective. You have to do this from the server side. This means validating the requests on the server to ensure that they conform to your expectations to some degree.
Game companies will
Require user authentication of some kind so they can identify users
Create some rules about possibilities. For example, the laws of physics should apply, so you know when someone has cheated. Something they can validate as human activity.
Ban people who cheat
If you are not sending data continuously over the network, then you have an issue which is unsolvable unless you are willing to make checks on the server securely and continuously over the course of the game. This will increase server load, but that's the unfortunate cost of preventing cheats.
I have an application that send very big quantity of requests to the server (they appears after the page is loaded, and made from flash app)
This happens so often that status line go mad (displaying: Transferring data text every few seconds), and it's really annoying.
I that possible to handle all events on the page, and don't allow them to change status line? Or set it to empty string, if it's impossible to disable?
In many UAs the user can disable the "feature" of changing the status line with JavaScript so the short answer to your question is:
No, at least not reliable.
A not reliable semi solution could be that you launch your webapp in a new window without a status bar. But again, not reliable as users can override that or have new windows open as tabs etc.
Possibly OT: personally I think the user has the right to know when her/his UA is sending and/or receiving data. It´s about integrity, privacy and all that stuff.
Just try to embrace the fact that the end user (the actual owner of the UA) is in control (and should be).