Bug #76519 [Com]: include function access file written after question mark (?)

Edit report at https://bugs.php.net/bug.php?id=76519&edit=1 ID: 76519 Comment by: ziyahan at netsparker dot com Reported by: ziyahan at netsparker dot com Summary: include function access file written after question mark (?) Status: Not a bug Type: Bug Package: Filesystem function related Operating System: Ubuntu PHP Version: 7.0.30 Block user comment: N Private report: N New Comment: BTW, I forgot to say. For the case below: http://VULNERABLE_HOST/test/file.php?target=file.txt../../../../../../../etc/passwd I can reach /etc/passwd either way, existence of file.txt does not matter! Previous Comments: ------------------------------------------------------------------------ [2018-06-22 11:41:19] ziyahan at netsparker dot com Hi again, There is a wrong assumption here. If OS would be Windows, you're right, payload can be considered OK. It is because in Windows, you will be able to access test/../../../file.txt, even if the directory test does not exist However, the OS that I worked on is Ubuntu. Yes, question mark is not mandatory. http://VULNERABLE_HOST/test/lfi.php?target=wrong.php../../../../../../../etc/passwd However, the file, wrong.php, does not exist actually:) How can I access the file /etc/Password by using the payload above? It seems weird, a bug. IF you don't think so, please explain how it can be possible? ------------------------------------------------------------------------ [2018-06-22 10:28:51] requinix@php.net That is a simple path traversal attack. https://www.google.com/search?q=path+traversal+attack The %3f and %253f is used to trick phpMyAdmin's checkPageValidity() into allowing the path. Why it even allows for anything other than a strict whitelist, let alone for question marks in the *filename*, I don't know... The question mark is not required for your proof of concept. ?target=ziyahan.txt/../../../../../../../../etc/passwd ------------------------------------------------------------------------ [2018-06-22 10:27:29] cmb@php.net This does not look like a bug at all. You are checking if $page *starts* with "ziyahan.txt", and it does. This is certainly insufficient to validate a user supplied filename which you intend to pass to include. A properly configured open_basedir setting should prevent the inclusion of etc/passwd, though. ------------------------------------------------------------------------ [2018-06-22 10:06:32] ziyahan at netsparker dot com Description: ------------ a few days ago, a bug disclosure has been published: https://mp.weixin.qq.com/s?__biz=MzIzMTc1MjExOQ==&mid=2247485036&idx=1&sn=8e9647906c5d94f72564dec5bc51a2ab&chksm=e89e2eb4dfe9a7a28bff2efebb5b2723782dab660acff074c3f18c9e7dca924abdf3da618fb4&mpshare=1&scene=1&srcid=0621gAv1FMtrgoahD01psMZr&pass_ticket=LqhRfckPxAVG2dF%2FjxV%2F9%2FcEb5pShRgewJe%2FttJn2gIlIyGF%2FbsgGmzcbsV%2BLmMK#rd In disclosure, researcher use question mark (?) to bypass validity mechanism of phpmyadmin, however this trick can be used also in pure PHP script. I really don't understand how php interpreter evaluates question mark that given as param to include function. I have a code like below: <?php $page = $_REQUEST["target"]; if(strpos($page,"ziyahan.txt")===0) { include $page; } ?> It does not seem bypassable first, however I realize that a weird payload can bypass this ?target=ziyahan.txt%3f/../../../../../../../../etc/passwd I cannot understand how the payload has an affect there? It seems a bug. ------------------------------------------------------------------------ -- Edit this bug report at https://bugs.php.net/bug.php?id=76519&edit=1