Passing data securely in PHP

Question

I have a site that allows user A to search for and view other users. When user A clicks on say user B. I pass user B's id as a GET variable. I then use that id inside my view to display the appropriate data. Is this good practice? Should I expose a users ID?

Also, when user A is on user B's profile he can send user A a message. How do I pass user B's id securely to my controller?

Any help greatly appreciated.

Answer 1

There are more than one way to do this.

One way that I usually use for such use cases, is to create a unique hashed identifier that is enough pseudo-random so that when that gets passed through the url, the user will not be able to just randomly change some values in it and get another user's profile.

Eg suppose you are passing ID, the URL would be something like:

showProfile.php?id=1256

changing 1256 to 1257 might reveal the next user.

Supposing you pass a hashed string that is sufficiently random:

showProfile.php?id=u4n5l4534mnk43nl34n

And such hashes do not follow sequences, so that you cannot change a character/number in order to get the next one.

It also depends on how secure you want to make user data sharing between members of the site

Answer 2

So, I am thinking that when user A clicks on user B profile, the url becomes something like site.com/profile.php?id=24 hmm? 24 being user B's profile. If that is the case, then there is no problem with it. At some point, when you are searching for a user's profile, you are going to echo something that is in your database, be it, his id, username, or lastname. So, id is good, but if you need professionalism, you could even user the username, with a little bit of help from htaccess, it might as well look like site.com/profile/john

So, in short there is no way you can echo something for each profile, which is not already in database.

BUT looking at your tag, that you have mentioned mysql if you are using on profile page, something like this:

$user  = $_GET['id'];
$query = mysql_query("SELECT * FROM USER WHERE id = '$user' ");

Well... that is Dangerous and leaves your website/database OPEN for an attack. So, if you are using something similar to above, you should use PDO