Dangerous, but want to make it work! Help!

garoof

Hello,
I have a website and I want users to be able to store PHP scripts on it. The PHP scripts would be ONLY for their personal use and I want to set it up so it cannot be accessed, read, written by, or any other communication with any users except the one creating it.

Basically, I want to set up a max 2mb webspace for users to mess with PHP.

I'm fairly new at PHP, and understand giving users the ability to use script on any part of a website is a security risk. I am very driven to get this to work safely. My ideas pertain to:

Setting up FTP space for each user so they only have access to THEIR files.
Filtering any commands that attempt to use any databases (filtering my database name and other creation/writing to database commands).
Filtering any FTP commands.
Tracking attempts to use FTP/database commands and immediately (temporarily?) banning users that get X amount of "attempts".

Is there a way to make user-created php files be able to interact solely with other php files in the user's ftp space? Is there really any even semi-safe way to do this at all?

bretticus

Well, you should certainly chroot apache at the bare minimum. Ideally, you'd have someway to sandbox each individual account. Or even the ability to virtualize a mini server for each user (expensive.)

etully

Yes. There are lots of ways to do this.

The truth is that your question isn't really a PHP question - it's really a sysadmin / web hosting question.

It's good that you recognize this as dangerous. It's also good that you're realistic about your skills and experience level.

If your goal is to learn how to get this done, you have years worth of work to do to gain the skills to administer a multi user server. If we wrote 500 pages of instruction here to help you along, it wouldn't be enough. Start small and build your way up to what you are proposing.

If your goal is to get this project done, your best bet is to get a web server and hire a sysadmin who has experience with chroot or vserver environments - or even normal Unix permissions. Frankly, though, web hosting (far better than you describe) can be had for about four bucks a month which is essentially free.

Unless you are doing this for your own learning purposes and to gain experience, it just doesn't make sense to spend thousands of hours learning to build this system when people can get something way better for four bucks a month.

garoof

Thanks for the quick feedback.

Yes, my goal is to make a sort of PHP sandbox. The purpose is really to allow users to create a few php files in their "sandbox" in order to practice using basic php functions. I could set them up with a cheap web-hosting package, but I'm trying to create something with a very simple interface. The sole purpose is to practice PHP and I'd like to rid it of all the other fruits that come with a complete hosting package.

Ideally, I'd like a form-esque input where the user can create a new file, delete an existing one, or view a file they made (test the code). That is really all I'd like to do with it - and would like to very much limit any other uses for the "sandbox" space.

Perhaps I am getting in over my head...but I'd like to be persistent in understanding more about php and server structure function. Thanks!

bretticus

Well, I suppose you could disable pretty much any function that could be construed as a dangerous function using ini_set before calling eval() on your users text. (I'd probably not give them an ftp account as that just introduces more risk.) Look at safe mode documentation for ideas. Still, when you allow someone to run code on your machine, you are always taking a significant risk. Again, chroot apache. I suppose you wouldn't need to jail accounts if you don't provide them (I wouldn't if I were you.)