Stop Users from Cross-linking Attachments

I've hacked my attachment.php script to prevent users from posting an attachment on my board, and then using the HTML to display it somewhere else. This prevents people from posting a pic on your board, then using your bandwidth to place that pic elsewhere. It is a tiny code change.

I've substituted my own logo, (LOL), but you can replace that with anything, or just use the "exit;" line to eliminate the pic entirely.

In attachment.php, right after:

PHP Code:

require("./global.php"); 


Add the following code:

PHP Code:

// Cross-link hack by Guru 2/24/2002
// Check that we aren't linked somewhere else
$url = parse_url($_SERVER['HTTP_REFERER']); 
$checkurl = strtolower($url["host"]); 
if (! strstr($checkurl, "yourdomain")) {

    // Remove this code if you just want to break the image
    // Substitute my Logo
    header("Content-Type: image/gif"); 
    $filename = "/usr/public_html/grafix/logo.gif";
    $image = fread(fopen($filename,"r"),100000); 
    echo $image; 
    fclose($image);
    // End Substitute my Logo

    exit; 
} 


Change yourdomain to your actual domain name, and the logo URL to what you want to replace the cross-linked image with.

NOTE: Changed to use the full path in "$filename = ..." to get this to work on some servers.

ANOTHER: See this post in this thread for a modification that works on Win32 servers: https://vborg.vbsupport.ru/showthrea...895#post297895

AGAIN: If you modify avatar.php similarly, you can prevent people from cross-linking your avatars: https://vborg.vbsupport.ru/showthrea...893#post303893

UPDATE: The parse_url line is slightly different to use the new PHP syntax.

[Lionel]

it does not work for me in 2.21. I am able to view attachment from dreamweaver and from anywhere

[Guru]

Try to view the attchment from a site that is not related to yours... look at nafae's post, above...

[voogru]

Testing

[Guru]

Originally posted by voogru
Testing

heh heh...

[Guru]

Hey! Post your own variations here! We'd all like to see.

[lifesourcerec]

I rather not Rated R label... teach those pesky bandwidth stealers a lesson.

I was thinking of using my avatar and use the text "You want your ear bit off too??"

[Lionel]

Originally posted by Guru
Try to view the attchment from a site that is not related to yours... look at nafae's post, above...

I tried the same. It will not work. Unlucky me.

[LanciaStratos]

This is an awesome, money-saving hack! Thank you very much! I'm going to give it a shot right here...my new image is a giant orange logo with my URL...

[Sidd]

testing

[amsch]

just a test