Riding the Crazy Train

Tracie P

In this article we are going to go through File Inclusion Vulnerability. Wikipedia defines File Inclusion Vulnerability as: "A file inclusion vulnerability is a type of web vulnerability that is most commonly found to affect web applications that rely on a scripting run time. This issue is caused when an application builds a path to executable code using an attacker-controlled variable in a way that allows the attacker to control which file is executed at run time. A file include vulnerability is distinct from a generic directory traversal attack, in that directory traversal is a way of gaining unauthorized file system access, and a file inclusion vulnerability subverts how an application loads code for execution. Successful exploitation of a file inclusion vulnerability will result in remote code execution on the web server that runs the affected web application."
There are two types of File Inclusion Vulnerabilities, LFI (Local File Inclusion) and RFI (Remote File Inclusion). Offensive Security's Metasploit Unleashed guide describes LFI and RFI as:
"LFI vulnerabilities allow an attacker to read (and sometimes execute) files on the victim machine. This can be very dangerous because if the web server is misconfigured and running with high privileges, the attacker may gain access to sensitive information. If the attacker is able to place code on the web server through other means, then they may be able to execute arbitrary commands.
RFI vulnerabilities are easier to exploit but less common. Instead of accessing a file on the local machine, the attacker is able to execute code hosted on their own machine."
In simpler terms LFI allows us to use the web application's execution engine (say php) to execute local files on the web server and RFI allows us to execute remote files, within the context of the target web server, which can be hosted anywhere remotely (given they can be accessed from the network on which web server is running).
To follow along, click on the File Inclusion navigation link of DVWA, you should see a page like this:

Lets start by doing an LFI attack on the web application.
Looking at the URL of the web application we can see a parameter named page which is used to load different php pages on the website.

http://localhost:9000/vulnerabilities/fi/?page=include.php

Since it is loading different pages we can guess that it is loading local pages from the server and executing them. Lets try to get the famous /etc/passwd file found on every linux, to do that we have to find a way to access it via our LFI. We will start with this:

../etc/passwd

entering the above payload in the page parameter of the URL:

http://localhost:9000/vulnerabilities/fi/?page=../etc/passwd

we get nothing back which means the page does not exist. Lets try to understand what we are trying to accomplish. We are asking for a file named passwd in a directory named etc which is one directory up from our current working directory. The etc directory lies at the root (/) of a linux file system. We tried to guess that we are in a directory (say www) which also lies at the root of the file system, that's why we tried to go up by one directory and then move to the etc directory which contains the passwd file. Our next guess will be that maybe we are two directories deeper, so we modify our payload to be like this:

../../etc/passwd

we get nothing back. We continue to modify our payload thinking we are one more directory deeper.

../../../etc/passwd

no luck again, lets try one more:

../../../../etc/passwd

nop nothing, we keep on going one directory deeper until we get seven directories deep and our payload becomes:

../../../../../../../etc/passwd

which returns the contents of passwd file as seen below:

This just means that we are currently working in a directory which is seven levels deep inside the root (/) directory. It also proves that our LFI is a success. We can also use php filters to get more and more information from the server. For example if we want to get the source code of the web server we can use php wrapper filter for that like this:

php://filter/convert.base64-encode/resource=index.php

We will get a base64 encoded string. Lets copy that base64 encoded string in a file and save it as index.php.b64 (name can be anything) and then decode it like this:

cat index.php.b64 | base64 -d > index.php

We will now be able to read the web application's source code. But you maybe thinking why didn't we simply try to get index.php file without using php filter. The reason is because if we try to get a php file with LFI, the php file will be executed by the php interpreter rather than displayed as a text file. As a workaround we first encode it as base64 which the interpreter won't interpret since it is not php and thus will display the text. Next we will try to get a shell. Before php version 5.2, allow_url_include setting was enabled by default however after version 5.2 it was disabled by default. Since the version of php on which our dvwa app is running on is 5.2+ we cannot use the older methods like input wrapper or RFI to get shell on dvwa unless we change the default settings (which I won't). We will use the file upload functionality to get shell. We will upload a reverse shell using the file upload functionality and then access that uploaded reverse shell via LFI.
Lets upload our reverse shell via File Upload functionality and then set up our netcat listener to listen for a connection coming from the server.

nc -lvnp 9999

Then using our LFI we will execute the uploaded reverse shell by accessing it using this url:

http://localhost:9000/vulnerabilities/fi/?page=../../hackable/uploads/revshell.php

Voila! We have a shell.

To learn more about File Upload Vulnerability and the reverse shell we have used here read Learning Web Pentesting With DVWA Part 5: Using File Upload to Get Shell. Attackers usually chain multiple vulnerabilities to get as much access as they can. This is a simple example of how multiple vulnerabilities (Unrestricted File Upload + LFI) can be used to scale up attacks. If you are interested in learning more about php wrappers then LFI CheetSheet is a good read and if you want to perform these attacks on the dvwa, then you'll have to enable allow_url_include setting by logging in to the dvwa server. That's it for today have fun.
Leave your questions and queries in the comments below.

References:

FILE INCLUSION VULNERABILITIES: https://www.offensive-security.com/metasploit-unleashed/file-inclusion-vulnerabilities/
php://: https://www.php.net/manual/en/wrappers.php.php
LFI Cheat Sheet: https://highon.coffee/blog/lfi-cheat-sheet/
File inclusion vulnerability: https://en.wikipedia.org/wiki/File_inclusion_vulnerability
PHP 5.2.0 Release Announcement: https://www.php.net/releases/5_2_0.php

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Tracie P

Give gifts this holiday season that inspires your favorite hackers to make something great. Our ten top picks for gifts to make 'em smile are perfect for hackers of all styles, ages, and interests.

Holiday gift guides always struggle when faced with nailing down a list for hackers — that's because hackers are as diverse in their interests and fascinations as they are diverse in gender, color, size and everything else. Someone with a multi-focused set of curiosity and unique gifts for finding out what makes the crackable crack may seem like a daunting individual to stuff a stocking for … but don't fret. With a keen eye on the latest interests in hacker culture, we've got a gift guide that can make the hacker in your life smile as they enjoy using your gift to hack and explore throughout the coming year.

Anonymity online: The Onion Pi

One of the most popular "snake oil" (fake) privacy gadgets is the so-called "Tor in a box" — a plug-and-play gadget that promises to make you anonymous online. Nearly all of these are made by clueless charlatans whose products put you at risk for privacy and security breaches. But your favorite hacker can just make or build an "Onion Pi" for $69.95, and with this free tutorial.

Attribution Dice

With Attribution Dice ($20), anyone can be a high-priced security consultant, and predict breach headlines before PR firms have a chance to feed them to reporters! With every security breach, hackers roll their eyes when headlines and PR firms roll out the same old, same old terms, methods and culprits. Instead of rolling eyes, your hacker can roll the dice, and wow friends, family, and neighbors with their hacker cyber-powers.

21 Bitcoin Computer

Money is always a welcome gift. Give the gift of going hands-on with Bitcoin with the 21 Bitcoin Computer. "The 21 Bitcoin Computer is ideal for buying and selling digital goods and services. You can use it to create bitcoin-payable APIs, set up your own personal digital goods store, pay people to share your content online, or host online games of skill." It's not cheap ($395) and comes with controversy, but it's a cool toy with a lot of potential, and 21 Inc. is going to be releasing an open source package for the device soon.

Gentleman's Bogota Lockpicks and Clear Practice Lock

Conventional wisdom suggests that all hackers know how to pick locks, but can they do it in style? A perfect stocking stuffer for slick hackers of all genders is the Gentleman's Bogota lockpick set ($34.95). These featherweights pin discreetly to a collar, hat, sleeve, vest, hemline, or wherever they choose. If the hacker you're shopping for wants to learn to lockpick, or just brush up on technique, throw in the clever Clear Practice Lock ($34.95).

Inverse Path USB Armory

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In this reviewer's opinion, every hacker should have a USB Armory in their stocking this year. The Inverse Path USB Armory ($130) is a little USB stick with an entire computer onboard (800MHz ARM processor, 512MB RAM), designed to be a portable platform for personal security applications — and lives up to its reputation as "the Swiss Army Knife of security devices."

Hack-A-Day Gift Card

The cornerstone of hacker culture Hack-A-Day has a store offering gift cards and merchandise a-plenty. In it, you'll find a Bukito portable 3D printer ($899.97), ever-popular Facedancer21 and Gootfet42, a low energy Bluetooth Arduino microcontroller called the Lightblue Bean, and the pocket-sized open source robot arm, Mearm.

Hackers 20th Anniversary Blu-Ray Edition

Hack the planet! The 20th anniversary of influential 1995 cyberpunk film "Hackers" was this year, and this cult classic got a special edition Blu-ray release, making it the must-have for the hackers in your life. The 20th anniversary "Hackers" Blu-ray features an hour-long "making of" documentary, rich video and audio transfer for the film itself, and interviews with: Cast members Matthew Lillard, Fisher Stevens, and Penn Jillette; hacking consultants Nicholas Jarecki and Emmanuel Goldstein; Director Iain Softley, and many more involved with the film's production and style.

A Hacker's hope for better sleep: The Re-Timer

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Hackers are increasingly hacking themselves to make their own systems run better, and one thing hackers struggle with is their sleep cycles and feeling rested. Something that can help out is the Re-Timer ($299), a retro-future looking set of glasses and kit that adjusts the circadian rhythm and suppresses the body's production of melatonin (the sleepy hormone our bodies produce which makes us feel tired). Based on 25 years of research and on the market worldwide for three years, the Re-Timer has its own jet lag calculator app, as well as its Sleep App for Fitbit that makes a customized schedule based on actual sleep tracked.

USB Rubber Ducky Deluxe and LAN Turtle

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A longtime favorite with hackers, penetration testers and IT professionals, the USB Rubber Ducky Deluxe ($42.99)is a cross-platform (Windows, Mac, Linux, Android) testing and experimentation device that is detected as a keyboard — imagine the possibilities. This stocking stuffer pairs well with its animal friend LAN Turtle ($50), a covert sysadmin and pentest tool for remote access, network intel gathering, and man-in-the-middle monitoring through a simple graphic shell (all in a generic USB ethernet adapter case).

TechShop Gift Certificate

Give the gift of hacking and making: A gift certificate to a TechShop. "Part fabrication and prototyping studio, part hackerspace, and part learning center, TechShop provides access to over $1 million worth of professional equipment and software. We offer comprehensive instruction and expert staff to ensure you have a safe, meaningful and rewarding experience." There are TechShops in Arizona, California, Michigan, Missouri, Pennsylvania, Texas, and Virginia/Washington, D.C. (some states have multiple locations). Future locations include St. Louis, MO and Paris, France.

Products to avoid

If you see these products, run! You're better off with a lump of coal. Don't waste precious holiday money on "snake oil" privacy and security products like these:

Anonabox
Wemagin
Webcloak
iGuardian (now SHIELD)
LogMeOnce
Sever: The Anti-Villain Box

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Tracie P

"ShellForge is a python program that builds shellcodes from C. It is inspired from Stealth's Hellkit. Some wrapper functions arround system calls are defined in header files. The C program uses them instead of libc calls. ShellForge uses gcc to convert it into assembler. It then modifies it a bit, compiles it, extract code from the object, may encode it and add a loader at the begining." read more...

Website: http://www.secdev.org/projects/shellforge/

Riding the Crazy Train

Friday, June 2, 2023

Learning Web Pentesting With DVWA Part 6: File Inclusion

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