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Creating a function to help secure forms

Posted on 2007-11-25
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Last Modified: 2008-02-01
I have a form and I want to make it more secure by using strip slashes and I was seeing some examples and is there a way to make that a function to attach it to every field instead of writing it on each one?

Does that make sense? In the function will have strip slashes, then call it on the field?

Is there anything else I should include in the function to help the security?
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steelseth12 earned 500 total points
ID: 20347336
if magic_quotes are enabled, then an escape character(\)  is added to ingle quote (‘), double quote (“), backslash (\) and NUL (\x00) which are all possibly dangerous characters when inserted into mysql.

If  magic_quotes are off then you should use addslashes to escape those characters manually

Below is a function that will check and addslashes if needed
function sanitise_data() {
 
	foreach($_POST as $key=>$value) {
		
		if(!get_magic_quotes_gpc()) {
	
			$_POST[$key] = addslashes($_POST[$key]);
	
		}
	
	}
	
}

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by:catonthecouchproductions
ID: 20347358
Thank you! So how would I implement this in to my script?
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by:steelseth12
ID: 20347373
You just need to call the function sanitise_data(); before the code that process a form.

Further than that you could validate each field manually to see if the result is what you are expecting.
For example  if you are expecting a number you could check that the result of the $_POST["telephone"] for example is numeric.

if(!is_numeric($_POST["telephone"])) {
    print "Error telephone can only contain numbers";

}


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Author Comment

by:catonthecouchproductions
ID: 20347402
So, i have this at my header.php page

<?php
include_once 'config.php';
include 'santise.php';
sanitise_data();
?>

So this will go for any input? And I am going to go through and make it more valid by like you said numerics, etc.

Can you explain that code? Just for I get a better understanding, i get it slightly.

Thanks for all of this!
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Expert Comment

by:steelseth12
ID: 20347438
Now that i look at it again a better way to write it would be as the one below.
Basically it will first check to see it magic_quotes are on. If they are not the it will loop through the $_POST and it will add slashes to every value
function sanitise_data() {
 
 if(!get_magic_quotes_gpc()) {
 
        foreach($_POST as $key=>$value) {
                
        
           $_POST[$key] = addslashes($_POST[$key]);
        
        }
    }     
}

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by:catonthecouchproductions
ID: 20347439
I just checked and I do have magic quotes on? Does that code work?
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by:steelseth12
ID: 20347450
the code first checks if magic quotes are on. If they are on then it does nothing.
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by:catonthecouchproductions
ID: 20347460
So i do have it on, so still use that code?

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by:steelseth12
ID: 20347473
You will use it only for portability reasons. I use it because the applications i develop , can be set up into defferent servers with different configurations.
If you are only going to set up your application once then there is no need for it. If you plan on reselling your application to others then you should keep it in.
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by:catonthecouchproductions
ID: 20347499
Alrighty, thank you! So having magic quotes on helps a ton? Security wise?
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by:catonthecouchproductions
ID: 20347501
Any other security steps i can take with my form?
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Expert Comment

by:steelseth12
ID: 20347519
If you have magic_quotes on and you validate your input data then you are 99.99% secure from sql injections.
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by:catonthecouchproductions
ID: 20349637
Thanks a ton man!
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