Relatively new rails programmer here, so bear with me.
I have an app where registered users can create polls but anyone can answer the polls.
I am using Devise for my authentication. I want non-authenticated users to be able to answer the polls but I want to prevent double-voting.
I assume this should be done with persistent (not session) cookies, but I'm not sure. So when the user enters the site, I create a user in devise and I store some random value in both the User model and in the cookie, and I check that the user has not answered the question previously when he/she attempts to load my "answer" page?
Can someone give me some advice on whether this is the right approach and/or point me towards a resource to help me get started?
I have found relatively little information out there on how to manage persistent cookies in Rails.
You can't reliably prevent people from voting multiple times without logging in. It's not possible. I guess people could also create multiple user accounts to vote so there is no fool proof way.
Cookies are often cleared automatically by certain popular cleaners and unless you are only going to allow people to vote on a product they have purchased I think you are kind fighting a lost battle.
Stack Overflow limits voting capability by making sure a certain level has been achieved before being allowed to vote but I guess that's not really applicable to your scenario.
This is not so much about sessions and cookies and more about setting up your database to record a vote including the voter id.
In the view that allows users to vote I would suggest that you switch between a voted icon and a vote now link depending on whether or not the currently logged in user has voted.
To determine if the user has voted then include the user id of the currently logged in user in a question_vote xref table.
For the belt and braces approach to prevent abuse of the html in the browser add the check to the validations of the question_vote record.
I would do this by adding a can_vote? method to the user model that accepts a question id as a parameter then you can use the question_id plus the user id to find a matching record in the question_vote table if a reordx is found return false otherwise return true
Related
I am Biulding an mvc asp.net website i want to add polls, i want to check if the user vote before what can i use:
1. IP : there is the problem of private and public IP
2.Cookie can be deleted
help please.
The only reliable way to achieve this is to require your users to authenticate to your site before voting. This way you can store the information that a user has already voted in your database. This way when a user logs in and attempts to vote you will know whether he has already voted or not.
If you allow anonymous users to vote on your site there just is no reliable way to do this.
I'm working on my first simple Rails app in which users submit sport "tweets" (e.g. "tennis, squash") and the server matches them up with partners. The server will return you a list of SportMatches based on similar tweets and you have different options (e.g. email, SMS) to reply back to someone's tweet and accept him/her as partner. Initially, the modeling was straight forward since: User has_many SportTweets and SportTweet belongs to User. Notifications were simply part of the User, or they could have been modeled as a 1-to-1 relationship to User.
My business requirements changed a little, as now I have anonymous users who can also post SportTweets. Because they don't have an account/profile, they must also submit notifications (e.g. email, SMS) with the tweet. I don't know how to model this the Rails way. SportTweets are now either anonymous, or authenticated-user-posted (AUP). So, now, my SportTweets table will have the following columns:
type: either "anonymous" or "AUP"
user_id: only for AUP
notifications_id: only for anonymous
sports: for all
post_date: for all
post_location: for all
etc.
There would be a Notifications table. A notification record would belong either to a User, or to a SportsTweet. I guess I would model this with polymorphic associations.
That just doesn't look like the Rails way. Did anyone come across a similar problem? How did you solve it?
Did a bit of searching and the answer is STI. See The Rails 3 Way - Chapter 9.
Use Devise if you can. I think this link might help you.
In some applications, it's useful to have a guest User object to pass around even before the (human) user has registered or logged in. Normally, you want this guest user to persist as long as the browser session persists.
Our approach is to create a guest user object in the database and store its id in session[:guest_user_id]. When (and if) the user registers or logs in, we delete the guest user and clear the session variable. A helper function, current_or_guest_user, returns guest_user if the user is not logged in and current_user if the user is logged in.
Followed by the code which you might find helpful in that page
I'm using devise/cancan for my app and everything is pretty sound -- provided a user creates an account and signs in.
What I'd like to do is allow a user to get started without creating an account. And then sign up if they want to actually save their work.
Has anybody come across this before? Should I be figuring out how to create dummy accounts with devise? Or allowing unauthorized users access to creating models in my app via CanCan?
I could go into detail about how I've been thinking about approaching this, but it feels like a pretty obvious use case that somebody has come up with a nice solution for.
Thanks in advance,
Mike
If you go with creating dummy accounts, you would have to track the user somehow via a cookie and cache the values in that cookie in your db. Cancan does allow for guest accounts via the ability model. For example:
user ||= User.new # Guest user, for users who are not registered or don't have an account yet
Which is enough you to you started with applying permissions for non registered users. Note though, tracking by cookie alone is not very reliable and can lead to some type of security hazard (i.e. by means of cookie hijacking). User, one day, can also decide to clear out his cookies.
If need be, I would suggest letting the user do minimal interaction with a guest account and motivating the user to sign up / register with Devise as much as possible.
Hope that helps!
I actually am considering the same problem, I have a scheduling app that makes a calendar. To get over the problem I'm thinking that you use
user ||= User.new
Like was suggested above and using cookies to get the data to the database once the user creates an account.
This would mean that you would not have to worry about clearing out cookies because they would create an account if they want to save data.
i have a question-answer survey..
Only one user can answer on survey! User cant click on previous button (in browser) and once again pass the survey. How i can possible do this? I need sessions and unique token? Please help me, i;m stuck with this...
If you have user-login, then you only need to validate whether they have already voted or not. This is really required to be 100% sure of no dup votes.
If not, you can't 100% guarantee dup votes, but you could make it difficult:
store in the session[:voted] = true
on receiving a vote submission don't accept if session[:voted] == true
Obviously the user can clear cookies which will clear your session.
You could enhance this by logging ip's but then consider proxy-servers (all users from behind the proxy will appear as coming from the same IP -- the proxy).
I you must enforce this then I imagine you'd require users to login and then you can store which surveys / survey sections they have already answered in your database.
Otherwise it's generally enough to prevent people from filling in surveys multiple times by storing their ip address in your system and also setting cookies on their browser based on which sections they have already completed. They can get around this by clearing their cookies but at least if you store their ip address they'd need to change ip to redo the survey.
It's hard to say without knowing the context of the survey. Is it on an existing app where users already have accounts? Is it standalone etc.
Thnanks guys for respons.
I thought about this (user-login), but i want to without it.. so i give link address, user get it, click on this address.. like www.blabalbla.com/test/survey/32643928569832569 (unique token).. and user can pass survey.. then when he finished he cant pass this survey again on this link.
so I have designed this voting thing which does not let somebody vote for the same article twice in 24 hours. However, suppose a person votes and after seeing the person was able to cast vote or that he is falling in that 24 hour window, I disable the vote-casting button (and this is all Ajax btw).
But what to do when a person closes his/her browser and comes back up or even refreshes the page? Obviously, he would not be able to cast vote, because of my algorithm, but the person would still end up succeeding in making call to the server. So if he really wanted, he would keep refreshing the page and clicking on the vote and put unnecessary load on the server. How to avoid that by doing some sort of client-side thing or something?
I am using ASP.NET MVC, so session variables are out of question.
Am I being over-concerned by this?
If voting happens only from logged in (known) members then you shouldn't have any problem.
If, on the other hand, everyone can vote then you need to store all user vote events:
timestamp
poll
poll_vote
ip
user agent
user uniqueness cookie
So you'll need a random hash sent out as cookie. This will ensure that you don't accept another vote for the same poll from the same person.
If the user deletes his cookies you fallback to plan B, where you don't allow more than (say) 10 votes from the same IP and user agent combination for 24 hours.
The system is not perfect since users can change IPs and (more easily) user agents. You'd need advanced pattern detection algorithms to detect suspicious votes. The good thing about storing all user vote events is that you can process these later on using a scheduler, or outsource the votes to someone else who can process them for you.
Good luck
Refreshing is not a problem
If you're doing all this voting using Ajax, refreshing a page won't do anything except load the page using GET.
If you're not using Ajax you should make sure you call RedirectToAction/RedirectToRoute action result, that would as well help you avoid refresh problems.
How do you recognise users
If you use some sort of user authentication this re-voting is not a problem. But if your users are plain anonymous, you should store IP address with your votes. This is how things are usually done. This makes it possible to avoid session variables as well. But you have to be aware of this technique because it's not 100% perfect.
Cookies?
You could of course also use absolute expiration cookies. They'd expire in an day. Advanced users would of course be able to avoid your voting restrictions, but they would be able to avoid other ways as well. Sessions BTW are also based on cookies anyway.
Combination
But when you'd like to make you system as great as possible, you'll probably use a combination of the above.
The best way would be to track who voted for what and when on the server (probably storing it in a database). In order to do this you must use an authentication system on your site (probably forms authentication) to identify users. So every time someone tries to vote you check first in your data storage if he already voted and when and decide whether to validate the vote or not. This is the most reliable way.
If your site is anonymous (no authentication required to vote) then you could store a persistent cookie on the client computer that will last for 24 hours and indicate that a vote has already been cast from this computer. Remember though that cookies might be disabled, removed and are not a reliable way to identify a given user.
I am using ASP.NET MVC, so session
variables are out of question.
Any reason for that? Sessions are perfectly fine in ASP.NET MVC applications. It is in your case that they won't work because if the user closes the browser he will lose the session.
Obviously, he would not be able to
cast vote, because of my algorithm,
but the person would still end up
succeeding in making call to the
server. So if he really wanted, he
would keep refreshing the page and
clicking on the vote and put
unnecessary load on the server
Automated bots could also put unnecessary load to your server which is much more important than a single user clicking on F5.
If you just want to ensure the user can only vote once on an article then you just need to store a Set (i.e. HashSet) of all article id's that they've already voted on, then just check before allowing the vote.
If you still wanted a 24hr limit then you need to store a Dictionary<articleId,DateTime> then you can check if he has already voted for that article and if he has when it was.