IOLI Crackme 0x03

I am continuing my reverse engineering review by tackling the IOLI crackmes by @pof. These are beginner friendly challenges that is perfect for newbies or for those who want to review the basics like me. Check out my writeups for 0x00, 0x01, and 0x02.

Getting the password

After opening the program in IDA I immediately saw that the code is almost exactly as the one in challenge 0x02, with the exception of our expected cmp command being inside the _test function.

Reading through the code I realized that the password for this challenge is exactly the same as the previous one!

But what's this? The success and failure messages are all garbled? And plus, what is this other new function called _shift?

A different kind of challenge

Opening up the _shift function shows us a short, but interesting looking program flow with two branches and one of the branches looping …

Maldoc101 Writeup (Part 1)

This is part 1 out of 2 of my writeup for the Maldoc101 challenge made by Josh Stroschein (@jstrosch) and is currently playable at Cyberdefenders.Org. I've done some maldoc analysis before but this is the first time I'm writing about my approach.

There is also an already existing writeup about this challenge from the creator himself. You should check that out if you want a more detailed and focused writeup. This writeup is more from the perspective of someone relatively new to malware analysis. There's a lot more exploration and trial-and-error which, I hope, might give the reader a different view in how this kind of problem is approached.

The challenge

Name

MalDoc101 - Malicious Document

Description

It is common for threat actors to utilize living off the land (LOTL) techniques, such as the execution of PowerShell to further their attacks and transition from macro code. This challenge is intended …

IOLI Crackme 0x02

I am continuing my reverse engineering review by tackling the IOLI crackmes by @pof. These are beginner friendly challenges that is perfect for newbies or for those who want to review the basics like me. Check out my writeups for 0x00 and 0x01.

Getting the password

After the first two challenges I kinda know what to expect already so I skipped running the program and immediately loaded it in IDA.

So the lines leading to the comparison command now looks more complicated than before. We could easily see that there are some computations that happens thanks to the presence of add and imul. Before those, we have two values (5Ah and 1ECh) which we can easily guess are the values that will be worked on by these arithmetic functions.

So going through the lines sequentially we can see that the two numbers are first added with add [eax], edx. Which …

Introducing shcode2exe

[Edit: shcode2exe is now part of Remnux]

I've been playing around with Remnux and encountered a problem trying to get one of the tools to run properly. The tool is shellcode2exe, it is used to compile binary shellcode to a file so it can easily be debugged by a debugger.

When I checked out the code, I was surprised to find out how simple it is. Basically, what happens is that the inputted shellcode is added to a barebones assembly file using the incbin assembly instruction. From there, the file is then automatically compiled and linked.

One big problem with the tool is that it needs to use Wine if it needs to run on Linux. I don't want such a huge dependency especially for my own malware analysis lab so I decided to write my own version which have led to the creation of shcode2exe.

shcode2exe

While similar in …

IOLI Crackme 0x01

I am continuing my reverse engineering review by tackling the IOLI crackmes by @pof. These are beginner friendly challenges that is perfect for newbies or for those who want to review the basics like me. Check out my writeup for 0x00 here.

Getting the password

Of course, the first thing we do is run the program.

Just like last time, we opened up the program in IDA and focused on the part of the code that does the comparing of passwords.

cmp [ebp+var_4], 149Ah
jz short loc_40137c

This seems easy enough.

Initially I entered 149A as the password but this turned out to be incorrect. The reason for this is because scanf was passed a format of "%d".

mov [esp+18h+Format], offset aD ; "%d"
call _scanf

This means that the input it expects is actually a decimal integer. So converting 149A to decimal results in 5274 …

IOLI Crackme 0x00

I am re-familiarizing myself with reverse engineering again by going through some simple crackme challenges. This one is called the IOLI Crackmes by pof. The goal is to find the correct password and also to patch it so that it can accept any input and still show that it's correct.

Getting the password

Running the program shows a password prompt.

Of course, randomly entering passwords is going to be a waste of time so I opened up IDA to look at its code.

I knew that whatever password I enter in the program would be checked against the actual password. This is the part of the program that I should focus on so I scanned the code and found this:

mov [esp+38h+Str2], offset Str2; "250382"
mov [esp+38h+Format], eax; 
call _strcmp

And just from these few lines alone I already knew what the password is …

Hunt the Kingdom CTF Challenge

TLDR: Participated in a blue team CTF, had a lot of fun, looking forward for more

Yesterday I participated in the GuideM "Hunt the Kingdom" CTF challenge. It served as the final activity at the end of the "Cyber Defense and Threat Hunting" course.

I was looking forward to this CTF, especially after my awesome experience with the Red Team Village CTF at Defcon. This one is centered on the Blue Team side, and I was curious as to how it will play out.

The Preparation

I took one whole day to study and prepare. I went through all our slides and have written down the important concepts and commands to an org file. This is important because I wanted them to be easily searchable, which helped a lot during the challenge.

I also did research about the Hunt the Kingdom challenge itself. There weren't much information online about it …

My experience with manufacturing printed circuit boards

I've done a lot of electronics projects already, all of them were painstakingly hand-soldered on a perfboard. I actually like this approach for quick prototyping, and plus, I've also grown fond of how "raw" it looks like. In spite of this, I've always been curious and interested in having my own printed PCB. I remember designing one for my TIRO vibrating watch but I never pushed through with it because I wasn't confident with what I've made.

I really like the raw, almost electronic-punk look of my work

A couple of months ago I got an email from PCBWay asking if I was interested in trying out their PCB manufacturing service. The email from PCBWay re-ignited this interest in having a PCB made. The problem is I didn't have a PCB design that I built myself that I knew was going to work. My best option was the "ESPBoy project …

CovidScammers writeup (Defcon RTV CTF)

I joined the Defcon Red Team Village CTF because I was curious about it and I wanted to test out the skills that I have gained playing with CTF sites like overthewire.org and vulnhub. I knew that the challenges won't be easy, but thankfully, I was able to join up with other newbies who were willing to give it a go and learn with each other.

Unfortunately, I fell asleep just before the CTF started and when I woke up all the easy challenges were already solved by my team members. There was one easy challenge that was still open on the CovidScammers category, so I quickly got started to solving that.

Free Flag (and binary) [1 point]

You've been contacted by a high-end but morally ambiguous finance company (unhackable-bitcoin-wallet.com) to investigate a data breach. The box in question is a mail server in their internal network, a …

Study notes: MAC Spoofing

Study notes are my personal research notes on certain topics that interests me.

Any network capable device has a unique factory-assigned Media Access Control (MAC) address. Users have no way to change the MAC address but it can be done. However, it is possible to mask the MAC address and have it show a different value. This is called MAC spoofing.

There are legitimate uses for MAC spoofing. For example, there may be certain applications that require a particular MAC address to work, or maybe your ISP expects a certain MAC address to connect to the network. MAC spoofing is largely used for illegitimate uses, like circumventing an access control list or getting past a filter on a wireless network.

Changing MAC Address via ifconfig

In Linux we could use ifconfig to change the MAC address.

To view the current MAC address:

$ ifconfig

The current MAC address is 08:00 …