And if you want to take it a step further, to ensure that the values are submitted from YOUR form, check the $_SERVER['HTTP_REFERER'] to see if it's coming from your domain | page.

Paul Nicholson wrote:
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On Friday 25 October 2002 11:23 am, Johnson, Kirk wrote:

And what should these precautions be?  If a malicious user can submit
his own form and you are looking for a POST variable, how can you
ensure that $admin came from your form and not that user's?
The problem is when a cracker uses form variables in an attempt to set the
values of "flag" variables kept only in the session, for example, $isAdmin.
As far as the form variables *you* put in your form, it doesn't matter
whether the user submits your form or a form they made themselves. Those
form variables are just data you are trying to collect.

With register_globals on, PHP takes *all* variables (GET, POST, COOKIE)
received from the client and assigns them to global variables. So if the
user posts a value for $isAdmin, she can give herself admin privileges.

The key is to retrieve *only* the form variables *you* put in the form from
the the $_POST array. So don't write a loop and grab *everything* from that


Exactly! Not only should you retrieve *only* the vars you need from POST,
you should also filter them to make sure they contain what you're looking for.....is_alpha($_POST['name']). And no, php doesn't have an 'is_alpha' function....I created that as part of a filtering class.


- -- ~Paul Nicholson
Design Specialist @ WebPower Design
"The web....the way you want it!"

"It said uses Windows 98 or better, so I loaded Linux!"
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