I'm writing an app that make some calls to my API that have restrictions. If users were to figure out what these url routes were and the proper parameters and how to specify them, then they could exploit it right?
For example if casting a vote on something and I only want users to be able to cast one vote, a user knowing the route:
get '/castvote/' => 'votemanager#castvote'
could be problematic, could it not? Is it easy to figure out these API routes?
Does anyone know any ways to remove the possibility of this happening?
There is no way to hide AJAX calls - if nothing else, one just needs to open Developer Tools - Network panel, and simply see what was sent. Everything on clientside is an open book, if you just know how to read it.
Instead, do validation on serverside: in your example, record the votes and users that cast them; if a vote was already recorded by that user, don't let them do it again.
Your API should have authorization built into it. Only authorized users having specific access scopes should be allowed to consume your API. Checkout Doorkeeper and cancancan gems provided by the rails community.
As others have said, adding access_tokens/username/password authorisation is a good place to start. Also, if your application should only allow one vote per user, then this should be validated by your application logic on the server
This is a broader problem. There's no way to stop users from figuring out how voting works and trying to game it but there are different techniques used to make it harder. I list some solutions from least to most effective here:
Using a nonce or proof of work, in case of Rails this is implemented through authenticity token for non-GET requests. This will require user to at least load the page before voting, therefore limiting scripted replay attacks
Recording IP address or other identifiable information (i.e. browser fingerprinting). This will limit number of votes from a single device
Requiring signup. This is what other answers suggest
Requiring third-party login (i.e. Facebook, Twitter)
Require payment to cast a vote (like in tv talent shows)
None of those methods is perfect and you can quickly come up with ways to trick any of them.
The real question is what your threat model and how hard you want it to make for users to cast fake votes. From my practical experience requiring third-party login will ensure most votes are valid in typical use cases.
Related
We are providing a form inside an iOS app for users to be able to fill out a survey. The submission works against our rails server, however, we don't require any user authentication since it's a public facing app. My concern is that with a properly configured curl command, someone could easily write a script that could fill up the database very quickly with bogus data. I could probably add some rate limiting that might help, but what would be a good way to minimally prevent someone from doing this? You could maybe limit it by using some obscure user agent that couldn't easily be guessed, but is there some sort of token scheme or some similar that would work that wouldn't require us to implement user auth? I'm not looking for absolute security--just a basic deterrent. Any ideas? Thanks.
Rails has some very good methods for role based authorization, e.g., cancan
But how can you grant authorization to specific pages, rather than controllers/actions.
For example, take the case of an app that contains a receipt or invoice model. A User can log in and generate an invoice. The User then needs to send his customer a URL to that invoice. The customer should not be able to access invoices of other customers, particularly important as Rails generates sequential and easily guessable path names (e.g., /invoices/1, /invoices/2, etc.).
Ideally the customer should not need to signup to view these pages. One solution might be to generate a random password on Invoice creation, and send this to the customer to unlock that page specific page.
This sounds like an issue that should be reasonably common, but after Googling I have not found much information of use (though I may be using incorrect search terms).
So I would like to know:
Is this something I should be attempting with Rails?
Are there any gems or example apps that I could study?
What are the potential considerations/ pitfalls of this approach?
Hi if the user you wish to have access was registered in the system it would be no issue at all as you could generate a permission record.
How ever your concern with the predictable urls can be easily solved by :
FriendlyID(https://github.com/norman/friendly_id)
or my personal favourite
Vanity permalinks (http://blog.teamtreehouse.com/creating-vanity-urls-in-rails)
Ideally the customer should not need to signup to view these pages. One solution might be to generate a random password on Invoice creation, and send this to the customer to unlock that page specific page.
So anyone with the information should be able to access it. One solution is to obfuscate the url or use a UUID, so don't give out /invoices/1, instead give /invoices/8a20ae59-30d5-41b6-86d3-ac66e3b43e9d. The url is unguessable. Still the url is the only piece of information one needs to access the contents.
If you want two-factor authorization, then the easiest way is to use http basic auth, generate a password from the url and your secret_base, and send it to the user separately. As it's generated, you don't need to store it, you can always check it by generating it again.
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.
What's the best way to keep users from sharing session cookies in Rails?
I think I have a good way to do it, but I'd like to run it by the stack overflow crowd to see if there's a simpler way first.
Basically I'd like to detect if someone tries to share a paid membership with others. Users are already screened at the point of login for logging in from too many different subnets, but some have tried to work around this by sharing session cookies. What's the best way to do this without tying sessions to IPs (lots of legitimate people use rotating proxies).
The best heuristic I've found is the # of Class B subnets / Time (some ISPs use rotating proxies on different Class Cs). This has generated the fewest # of false positives for us so I'd like to stick with this method.
Right now I'm thinking of applying a before filter for each request that keeps track of which Subnets and session_ids a user has used in memcached and applies the heuristic to that to determine if the cookie is being shared.
Any simpler / easier to implement ideas? Any existing plugins that do this?
You could tie the session information to browser information. If people are coming in from 3 or 4 different browser types within a certain time period, you can infer that something suspicious may be going on.
An alternative answer relies on a bit of social-engineering. If you have some heuristic that you trust, you can warn users (at the top of the page) that you suspect they are sharing their account and that they are being watched closely. A "contact us" link in the warning would allow legitimate users to explain themselves (and thus be permanently de-flagged). This may minimize the problem enough to take it off your radar.
One way I can think of would be to set the same random value in both the session and a cookie with every page refresh. Check the two to make sure they are the same. If someone shares their session, the cookie and session will get out of sync.
As a part of the signup process for my online application, I'm thinking of tracking the source and/or search keywords used to get to my site. This would allow me to see what advertising is working and from where with a somewhat finer grain than Google Analytics would.
I assume I could set some kind of cookie with this information when people get to my site, but I'm not sure how I would go about getting it. Is it even possible?
I'm using Rails, but a language-independent solution (or even just pointers to where to find this information) would be appreciated!
Your best bet IMO would be to use javascript to look for a cookie named "origReferrer" or something like that and if that cookie doesn't exist you should create one (with an expiry of ~24hours) and fill it with the current referrer.
That way you'll have preserved the original referrer all the way from your users first visit and when your users have completed whatever steps you want them to have completed (ie, account creation) you can read back that cookie on the server and do whatever parsing/analyzing you want.
Andy Brice explains the technique in his blog post Cookie tracking for profit and pleasure.