How to get a unique PC ID from a web browser

Question

I have a web app that will be running n several specific target machines. I could have the user select which machine he is on when he logs in, but that is prone to error. Is there a way I can get some unique ID from each PC, store those in a database on my server and then when someone logs in from a particular machine, identify that machine? I thought of IP address but those might change as well due to the nature of our deployment. But is is critical that I know which machine the system is running on.

Note: I am not trying to determine the machine code of a web user's machine as that would be a privacy violation. I KNOW my machines so I was wanting to tie them to the database somehow. This also acts as security for me as I can reject logins from unknown machines.

Thanks for any ideas. I am running Apache with Code Igniter 3 and Centos 6.5

Answer 1

It's not possible without a client component, browser plugin or something similar. The closest alternatives are:

• using cookies;
• using client certificates;
• using browser fingerprinting;

each with their own disadvantages.

Answer 2

You could use this as a computer ID:

$computerId = $_SERVER['HTTP_USER_AGENT'].$_SERVER['LOCAL_ADDR'].$_SERVER['LOCAL_PORT'].$_SERVER['REMOTE_ADDR'];

It's not completely fool proof, as the values of $_SERVER can be faked, however it will still add an extra layer of security that does not rely on cookies.