Imagine a space shooter with a scrolling level. What methods are there for preventing a malicious player from modifying the game to their benefit? Things he could do that are hard to limit server-side is auto-aiming, peeking outside the visible area, speed hacking and other things.
What ways are there of preventing this? Assume that the server is any language and that the clients are connected via WebSocket.
Always assume that the code is 100% hackable. Think of ways to prevent a client completely rewritten (for the purposes of cheating) from cheating. These can be things such as methods for writing a secure game protocol, server-side detection, etc.
The server is king. Clients are hackable.
What you want to do is two things with your websocket.
Send game actions to the server and receive game state from the server.
You render the game state. and you send input to the server.
You can NOT solve these problems by minifying code. Code on the client is ONLY there to handle input and display output. ALL logic has to be done on the server.
You simply need to write server side validation . The only thing is that a game input is significantly harder to validate then form input due to complexity. It's the exact same thing you would do to make forms secure.
You need to be really careful with your "input is valid" detection though. You do not want to kick/ban highly skilled players from your game. It's very hard to hit the balance of too lax on bot detection and too strict on bot detection. The whole realm of bot detection is very hard overall. For example Quake had an auto aim detection that kicked legitedly skilled players back in the day.
As for stopping a bots from connecting to your websocket directly set up a seperate HTTP or HTTPS verification channel on your multiplayer game for added security. Use multiple Http/https/ws channels to validate a client as being "official", acting as some form of handshake. This will make connecting to the ws directly harder.
Think of a simple multiplayer game. A 2D room based racing game. Upto n users go on a flat 2D platformer map and race to get from A to B.
Let's say for arguments sake that you have a foolsafe system where there's a complex authetication going over a HTTPS channel so that users can not access your websocket channel directly and are forced to go through the browser. You might have a chrome extension that deals with the authentication and you force users to use that. This reduces the problem domain.
So the hacker now has your websocket in a chrome sandbox. He sees the input. Of course your race course is dynamically and uniquely generated. If you had a set amount of them then the hacker could pre engineer the optimum race route. The data you send to visualise this map can be rendered faster then human interaction with your game and the optimum moves to win your racing game can be calculated and send to your server.
If you were to try and ban players who reacted too fast to your map data and call them bots then the hacker adjusts this and adds a delay. If you try and ban players who play too perfectly then the hacker adjusts this and plays less then perfect using random numbers. If you place traps in your map that only algorithmic bots fall into then they can be avoided by learning about them, through trial and error or a machine learning algorithm. There is nothing you can do to be absolutely secure.
At the server-side, there are 2 options:
1) Full server-side game
Each client sends their "actions" to the server. The server executes them and sends relevant data back. e.g. a ship wants to move north, the server calculates its new position and sends it back. The server also sends a list of visible ships (solving maphacks), etcetera.
2) Full client-side game
Each client still sends their actions to the server. But to reduce workload on the server, the server doesn't execute the actions but forwards them to all other clients. The clients then resolve all actions simultaneously. As a result, each client should end up with an identical game. Periodically, each client sends their absolute data (ship positions, etc.) to the server and the server checks if all client data is identical. Otherwise, the games are out of sync and someone must be hacking.
Disadvantage of the second method is that some hacks remain undetected: A maphack for example. A cheater could inject code so he sees everything, but still only sends the data he should normally be able to see to the server.
Obviously, a hacker could easily disable this component. To fix that, you could force the client to periodically reload the component from the server (The server can check if the script file was requested by the user periodically). This introduces a new problem: the hacker simply periodically requests the component via AJAX but prevents it from running. To avoid that: have the component redownload itself, but a slightly modified version of itself.
For example: have the component be located at yoursite/cheatdetect.js?control=5. The server will generate a slightly modified cheatdetect.js so that in the next iteration, cheatdetect.js?control=22 (for example) must be downloaded. If the control mechanism is sufficiently complicated, the hacker won't be able to predict which control number to request next, and cheatdetect.js must be executed in order to continue the game.
Obfuscate your client exposed code as much as possible. Additionally, use some magic.
They don't have to touch your client-side code -- they could just sniff and implement your Websocket protocol and write a tiny agent that pretends to be a human player.
Update: The problem has a few parts, and I don't have answers off the top of my head, but the various options could be evaluated with these questions in mind:
Sure many of the roadblocks you throw up can be side-stepped, but what is the cost to the player and you? See "Attrition warfare".
I'd use a combination of minification and AJAX. If all of the functions and data aren't loaded into the page, it'd be more difficult to cheat.
On the other hand, modding turned out to be a very profitable tool for companies like Id Software. Perhaps allowing the system to be modded might make the game that much more enjoyable to the community at large.
For eg.,. for a Basic login action : in angular while making a call to server, the backend validates username & pwd and if validated, it will come back to the client and let the user login using angular.
When I say login using angular, it is going to store things in cookies, like user objects and other things. But still the user can remove the JS code which is making the call to backend, and return TRUE(wherever needed) and insert user object(dummy) to cookies and other objects(whatever needed) and login. It is a very difficult thing to do, but it is doable. In many scenarios, this is not desirable even if it takes hours to edit/hack the code.
This is possible in single page applications, where JS files dont get reloaded for each page. To mitigate the possibility of getting hacked we can use minified codes. And I guess if actions like this is done in backend(like login in Django) it is much safer.
Please correct me if I am wrong.
There's nothing you can really do to prevent anyone from modifying your JS or writing a GreaseMonkey script. However you can make it hard for them by minifying your script as well as making your code as cryptic as possible. Maybe even throwing in some fake methods or variables that do nothing but are used to throw an attacker off. But given enough time, none of these methods are completely foolproof, as once your code goes to the client, it is no longer yours.
Some other methods that can be implemented:
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