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how to trick most of cms avatar upload filter [exemple for : RunCms (PoC)]
//how to trick cms avatar upload
//exemple for : RunCms (PoC)
//Bug : avatar/php-shell upload
you can upload a crafted picture on most of cms .
there's actually one protection agains that:
it's to reconvert the picture name uploaded ( see = http://us3.php.net/manual/en/features.file-upload.php )
so the picture called picture.jpg will be renamed has 12d32f2jk25r543jk2ljn543.jpg
now on a webserver , a script is called & executed with the extension , so if you rename & upload a crafted picture , like this :
you will get the php code in the picture executed .(if there's some php code in the crafted picture)
the reverse ( http://site.jpg.php ) will never work , it's usually because the avatar upload filter look for the last extension.
so now we need to trick the upload filter , if you do a simple php script named "script.php" ,it will never work ,
our goal is to trick the avatar filter , so we need a reel picture .
then you need to take a good file editor , like: notepad++
(you can take whatever picture , and edit it without destroying it .)
we need to put some php code AFTER the picture code .
when it's done , try the picture if it still work , if yes , we are ok :).
here's an exemple of a crafted picture :
just upload the picture has your avatar , for Runcms and do a right click ===> property , on your avatar , look at the link ,
and call it with firefox , opera , safary , etc , once this is done you have a php backdoor uploaded in .
usually in: http://site.com/[runcms_path]/images/avatar/sp.php.jpg
ps:this doesn't work with IE .
regards , securfrog@xxxxxxxxx