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"If it were easy, I wouldn't be doing this"

2019-11-18 20:59:00

bob ross

... That's what I told my classmate B. (their ballet blog is here) tonight: "if it were easy, I wouldn't be doing this." That's what I honestly believe: I often do things because they're a challenge. Hence why I kind of live by Bob Ross' quote shown to the left.

Or as Nobel laureate Craig Mello put it: "Ask yourself: “are you having fun?”. And sometimes it’s not fun, but there’s something at the back of your mind maybe saying: “if I can just figure this out”, you know? And when you do, finally do make sense of that thing, man! It’s so much better because it was hard!"

So, what are B., our classmates and myself learning?

Ballet.

I am learning ballet and have been for a few months now. I'm an uncoordinated ditz, struggling with basics, but I'm loving it even when I'm hating it. The hating is short and momentary, the loving is something that sticks. 


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In many cases, just cramming for an exam won't work

2019-11-18 20:44:00

Today, someone on Reddit posted the following question

"I have the [...] practice exams, I typed the entire [...] video course from YouTube and I just brought the exam cram book but no matter how much I study I don’t retain anything. Do you guys have tips?"

OP ran into the wall that is learning styles: cramming simply doesn't work for everybody! I'm no expert by any means, but I did explain the following:

It is entirely possible that your current method simply does not suit your personal learning style! If you start poking around the web a little bit, researching learning styles, you will find very quickly that there are many different methods!

You can try and keep brute-forcing your learning the way you have right now, but maybe that will simply not get the results you want. Why not have a think about your days in primary, middle and high school? What did the classes you did best in have in common?

Perhaps you're someone who simply needs something else than quiet self-study, taking notes while listening to a teacher.

Personally I have found that I put great importance on putting new information into context. I don't want to learn floating, individual topics, I want to put them into a context that I'm already familiar with, or build a context around them. This helps me better understand the new material's place. One thing that could help you with this is making mind maps.

Or perhaps you're someone who better learns by doing then by hearing. I understand that playing around with new tools and concepts in a lab can take a lot of time, but there's a reason why many books include lab exercises for the reader. It is often said that people learn <20% by hearing and >50% by doing.

Finally, it is also often said that one way to solidify and test your understanding of a subject, is to explain the topic to somebody else. If you can explain X or Y to a friend, your partner or a rubber ducky, then you can be sure that you've come to a proper understanding. Or perhaps you will find a few gaps in your knowledge that you need to fill out. Either way, it's a win-win.

 


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Zine: "The tale of the Dubious Crypto", a pentesting adventure

2019-11-08 16:15:00

A broken padlock

If you've met me IRL, you will most likely have seen me doodling or drawing. It's an almost compulsory thing for me! I've often said that drawing is like my brain's "Idle Process", running in the background making sure I pay attention to things around me, like meetings or phone calls.

Over the past 30+ years I've mostly drawn for my own enjoyment, though I've also published yonkoma comics about my daily life and even tried my hand at a short story or two. In 2019 things took a new turn after b0rk (Julia) and SailorHG (Amy) inspired me to make a "zine".

To sum it up, a "zine" (short for magazine) is a self-published booklet about subject matter that's dear to the author's heart. The Public have a made a wonderful zine explaining zines (how meta!), which is available here: An Introduction To Zines.

For starters, I'll write about things I've learned during my work and studies which I feel are well-worth sharing with others. The first issue, "The tale of the Dubious Crypto" covers Windows security practices and bad cryptography implementations in a piece of software I pen-tested.

You can find all upcoming releases, including printing instructions and license information, over here -> https://github.com/tsluyter/Zines


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PenTester Academy CRTP exam

2019-10-22 14:24:00

Ooooffff... What a night. What a day. I'm beat :)

It's hard to believe that my OSCP examination took place 2.5 years ago. It feels much more recent! Or maybe that's wishful thinking...

Anywho, over the past twentyfour hours I repeated the experience by taking part in PenTester Academy's CRTP exam: Certified Red Team Professional. It's the closure piece to their "Attacking & Defending AD" online training

I'm gonna say that this exam is absolutely not a red-teaming exercise (per Deviant Olam). RT would include attacks on both the physical space, human employees and on IT resources. And this exam squarely focuses on IT only. So the "RT" in "CRTP" is badly chosen, but alright. Let's put it down as marketing.

So! There are a few reviews out there about the CRTP (like Truneski's, or this thread on TechExams, and Spentera's), but as always I'm going to quickly recap my own experiences.

To get the obvious question out of the way: was it worth it? I got in at the introductory price of $550 for 90 days (normally $600) and either way I'd say "Heck yes!". Fourteen hours of video material and a well-built lab environment to hack Active Directory made it well worth it! 

Nikhil's videos are well-made and are perfect for playing at 1.3x or 1.5x speed.  The slide deck and lab guides are certainly good enough as well. 

It's great how the training explains multiple ways to achieve the same goal, though at times it became hard to tell them apart :D That's mostly a failing of my own though. It has become very much apparent that I need to go back and review these materials a few times before fully grasping these AD attacks. Luckily there are many great resources, like the harmj0y, adsecurity and Specter Ops blogs.

Excluding the exam, I spent roughly sixty (60) hours on the videos, labs and research. That's a lot of CPE for my CISSP, CEH and CompTIA certs!

The exam! Ooohhh, I loved it! It's like OSCP, where you're given a twentyfour hour window to attack and pwn a number of target systems. But where OSCP offers X amount of disparate hosts, CRTP has them tied together in an Active Directory environment. You're not attacking software on its vulnerabilities, no you're attacking an environment based on misconfigurations in AD or Windows!

Like ChrisOne in the TechExams thread I ran into a wall which would last me well over six hours. Here's a rough timeline (it's no secret that there are five target hosts, so I feel it's safe to describe the timeline):

You will notice that things moved really fast once I got onto the second target host. That's because my enumeration of the domain objects had provided me with a clear path of attack to move from the second through to the fourth one. The fifth one was pretty cut and dry from there on out, but it required more manual labour. 

Getting privesc on my workstation only took so long because I didn't want to outright get started with that. :) I first wanted to put as much time as possible into properly enumerating the domain.

By 2230, exactly twelve hours after the start of my exam, was I done with the attacks. I'd gathered notes and lots of evidence while attacking, so all that remained was writing the report. That's where things took a turn for the nostalgic: it played out like my OSCP exam! I wanted to take a nap before writing the report, but really could not get to sleep. So by 0030 I was up and writing again! And finally, five hours later at 0530, I submitted roughly 36 pages of report to PTA.

Fingers crossed! I'm hoping for good news!


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Ooofff, what a week (yes, still alive)

2019-10-04 20:01:00

And to think that I used to be such a diligent blogger! Weekly, or even daily updates! And now I've been quiet for almost three months?! Either, I've got nothing going on in my life, or way too much! :p Hint: it's the latter.

This week has been awesome!

I snagged my first official CVE, an XSS in Micro Focus Enterprise Server. I'd been sitting on that one for a few months now, so I can finally gloat a little bit :)

===

Last night was PvIB's annual CTF. Lemme tell you, it was a lot harder than in the previous years! I only managed to grab one of the "easy" flags. I learned a few cool new things though that I hadn't done before.

Most importantly: using Wireshark to decrypt TLS traffic in a PCAP. I had assumed that you would need the server's private key to do so, which turned out to be correct :) In this case the traffic had been encrypted with a private key which a malware creator had accidentally leaked. Had I Googled the subject's name on the certificate earlier, then I'd have found the private key much sooner as well ;)

===

Speaking of challenges: I took ${CLIENT}'s internal secure programming training for DevOps engineers this week. The training's a bit rough around the edges, but it covers a lot of important stuff for folks building web apps. I'm pretty impressed and also a bit daunted about teaching it in a few weeks. 

I'm now horribly aware that my webdev experience is 15 years old and antiquated. I've never even done much Javascript, let alone Flask, Angular, Jinja, and so on. So that's a challenge.

I took the exam for the course today: it was great! Like a mini OSCP where you're given a webapp with 15+ known vulnerabilities (ranging from CSRF, through XXE and SSTI through broken deserialization and JWT tokens). Lost of those things I'd not heard of yet! 

Anyway: you have nine hours! Find all the vulns, exploit them, suggest fixes and remedies and then report it all correctly. Nine hours?! That was a slog, even having full white-box access to the Docker container and all the sources.


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Yes, I'm still here! Just very busy

2019-07-31 21:48:00

It's been three months since I last posted publicly. Don't worry, I'm still here :) I just have a lot of things going on.

In our private life lots of things are also going on, but I'll leave those for another time and place.


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CTF036 2019, the Secured By Design CTF

2019-04-05 09:10:00

Me, on stage

The photograph on the left was provided by Secured By Design.

I love CTFs and though I can't take part in a lot of them, I make it a point to always play in Secured By Design's CTF036. Four years in a row now and the events just keep getting better! 

I was invited to give a small talk again, this time covering the basics of PKI: public key infrastructure. In short, PKI is one of the ways to solve the challenge of "trust" in an environment: how can you trust that someone or something really is whom they claim to be? We were very much cramped for time, so I had to try and smush everything into half an hour! While the talk went smoothly, I'm not entirely happy: there was just too much info in too little time. And I didn't even cover it all! 

My slide deck for "When Alice met Bob..." is over here. 

The CTF itself was, as always, a blast! Roughly a hundred participants, attacking six copies of the same target environment: three servers and two desktop systems, part of a fake school's infrastructure. Our goal was to grab as many student IDs as possible. 

The usual suspects were there yet again: weak passwords on mailboxes, SMB shares without proper ACLs, simulated end-users and a rudimentary daemon which you could try a buffer overflow on.

I spent most of my time on attacking one of the end users: a professor. The school's website featured an open forum, with sections dedicated to each of the classes taught. One professor warned his students that their final presentations were due any day now and that they should be submitted "through the usual share". This refers to the aforementioned, open SMB share which had a subfolder "Presentations". 

I recalled that SETookit and Metasploit offered options to create Word/Powerpoint/Office payloads, but had forgotten how to. I'm rusty, it's been a while since I've done this :) After a bit of research, I turned to exploit/windows/fileformat/office_OLE*. When configuring the exploit I simply chose to target all possible options, which generated roughly twenty files with shellcode. In real life this would obviously not work, because who would fall for that?! Twenty files without content, clicking through all of them? Nope :) But in this case the script set up on the workstation (to simulate the professor) was greedy and simply went through all of them. 

Using this method I got a nice and shell_reverse_tcp to my port 443. Looking to escalate my privileges on the workstation I tried to get a Meterpreter payload to run in the same way, but failed. I guess the payload was too tricky for the target. 

I explained this particular attack vector to two teams (ex-colleagues to my right, the team in #1 slot to my left), which was a fun exercise. I love explaining stuff like this to people who're just getting their feet wet (my ex-colleagues). The #1 team quickly latched onto the idea and offered an improvement to the attack: use the reverse shell to download a Meterpreter payload .EXE file. Duh! I should've thought of that! 

Anyway: a wonderful day with fun hacking and meeting cool people! Heartily recommended :)


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PKI: using a private versus a public ca

2019-04-05 06:17:00

This morning an interesting question passed through the SANS Advisory Board mailing list:

"Looking for anyone that has done a cost benefit analysis, or just general consideration, of using a Public CA vs. a Private CA for a PKI deployment. Some vendors are becoming very competitive in this space and the arguments are all one-sided. So aside from cost, I’m looking for potential pitfalls using a public CA might create down the road."

My reply:

My previous assignment started out with building a PKI from scratch. I’d never done this before, so the customer took a gamble on me. I’m very grateful that they did, I learned a huge amount of cool stuff and the final setup turned out pretty nicely! I’ll try and tackle this in four categories.

UPSIDES OF PRIVATE PKI

 

UPSIDES OF PUBLIC PKI

 

DOWNSIDES OF PRIVATE PKI

 

DOWNSIDES OF PUBLIC PKI

If your infrastructure needs to be cut off from the outside world, you will HAVE to run your own, private PKI. 

I’ve recently presented on the basics of PKI and on building your own PKI, be it for fun, for testing or production use. The most important take-away was: “If you’re going to do it, do it right!”. You do NOT simply fire up a Linux box with OpenSSL, or a single instance Windows Server box with ADCS and that’s that. If you’re going to do it right, you will define policy documents, processes and work instructions that are to be strictly followed, you’ll consider HA and DR and you’ll include HSMs (Hardware Security Modules). The latter are awesomely cool tech to work with, but they can get pricy depending on your wants and needs. 

Remember: PKI might be cool tech, but the point of it all is TRUST. And if trust is damaged, your whole infrastructure can go tits-up. 


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